This is an abridged excerpt from a (possibly unpublished) text by Mr Ted Packer, who was aa WSRL engineer in the 60s. It covers the problems encountered in the AQS13 sonar fit when the Wessex 31A was converted to the 31B, and is a fascinating snapshot not only of the life and time, but of the systems and technology available at that time. The article was forwarded by Chris Donald, who has our thanks.
“Navy Has a Problem!”
By December 1965 my modelling work for the Bloodhound II project was almost finished, when, one afternoon, my PO, Alex Biggs, called me into his office. He told me we were about to meet the Director of Navy Scientific Services (DNSS), Mr. J.P. Lonergan, who had approached our division (SAD) for informal discussions on a matter in which the Navy needed our scientific assistance. Apparently, the problem concerned a decision Navy had taken some two years previously to convert its 26 Westland Wessex Mk 31A helicopters to a new standard which was to be known as the Wessex Mk 31B.
At this point, Mr. Lonergan arrived and was shown in and introduced to us by our Divisional Superintendent, Mr. Peter Twiss. Jack Lonergan was a tall, easy-going man of around fifty. He was clean-shaven, clear-eyed and his dark hair was receding. We shook hands and sat down. He sat forward and looked at us seriously. He had an earthy, direct, but clear, way of putting things. He called a helicopter a “helo”, which was the American slang.
He explained that Navy had decided to convert its 26 Wessex Mk 31A helicopters to a new standard to be known as the Wessex Mk 31B. The purpose of the conversion was to improve the ASW (Anti-Submarine Warfare) capability of the Wessex by means of a modernisation programme, including the fitting of the Bendix (Pacific) AQS 13 sonar set as a replacement for the ageing Plessey Type 194 sonar set. Such sonars are active submarine-detection devices, often referred to as “transducers”, the Type 194 being a Plessey (UK) development of the Bendix (Pacific) AQS 4.
Most helicopter-deployed sonar sets are operated by lowering them into the sea on a cable. Sonar information received by the transducer is routed up the cable to the helicopter and interpreted there by a sonar operator with the aid of electronic display and signal-processing equipment.
For best performance, the body of the sonar had to be kept close to the vertical in the water, especially for long-range detection, and it had to be as near as possible stationary in the water. This was because, when water flows around or through a sonar body, it causes acoustic noise which, even at half a knot, can drown out the echo of a modern submarine several thousand yards away.
Once the sonar was lowered into the sea, the helicopter ASW system was switched to its “Cable Hover Mode”. This situation was known in naval slang as “the dunk” or “the dip”. In this mode, the angle of the cable as it entered the aircraft had to be kept as close to vertical as possible.
To achieve this the cable was used to control the motion of the aircraft. This was normal for most anti-submarine helicopters, as it still is today. It was done by using sensors to measure the angle by which the cable deviated from the vertical as it left the aircraft. This angle was then automatically fed into the automatic cable-hover control system to manoeuvre the aircraft so as to bring the cable back to the vertical.
The reason behind this somewhat bizarre scheme was that it had been shown mathematically that only if the cable was vertical as it left the aircraft would the sonar set, way down below, remain stationary and near vertical in the water.
In hostile operations, the pilot was required to take the chopper down to hover at thirty feet above sea-level, lower the sonar and switch the control system over to automatic cable hover mode. This might often need to be done at night and in bad weather with rough sea-states. Once in automatic cable hover, the pilot could sit back and take no part in flying the aircraft, trusting to the control system to stabilise it for him!
For pilots to have that kind of faith in the helicopter, the whole system has to be demonstrably capable of maintaining a high degree of stability and control with a high degree of reliability, at night and in heavy weather conditions.
The Type 194 could not be lowered more than eighty feet into the sea, and it was desirable to operate sonar at depths of up to four hundred feet, in some cases, for tactical reasons. The fact that the AQS 13 could provide this capability was the reason why the replacement of the Type 194 by the AQS 13 was the key part of the conversion project.
However, the sonar upgrade would mean changing the length − and strength − of the cable used to lower the sonar into the water, which would, in turn, require the replacement of the on-board reeling machine used for that purpose, by a larger, heavier one.
It was also seen as an opportune time to refit the aircraft with some new and improved electronics systems for surveillance and communications. These would also add a good deal to the all-up weight of the fully-equipped aircraft.
To carry all this extra weight, it would be necessary to increase the rotation speed of the rotor by 10%. The rotor could take this without ill effects, but to provide the extra power required, it would also be necessary to refit the aircraft with a more powerful Rolls-Royce gas-turbine engine.
Another problem was floor space in the cabin of the helicopter. The cable and its sensors were enclosed in a conical funnel, open at the bottom, and the cable passed from the reeling machine, and out of the cabin, through the large hole formed by the cone, in the cabin floor, passing through the cable-angle sensors on its way. The hole in the floor of the Wessex 31A was large enough to permit the cable to swing by up to 20º from vertical in any direction. But the addition of the new electronics racks in the cabin did not leave enough space for such a large opening in the cabin floor of the Wessex 31B.
The large amount of space had originally been provided to allow for violent swings of the cable when strong wind gusts struck the aircraft or waves hit the cable, making it tilt in one direction or another. The reasoning had been that the more room the cable had to deflect during a disturbance, the larger the demand signal from the sensors would be, and this large signal would cause the helicopter to make a more rapid recovery from the upset.
Such violent upsets were called “drag-offs” and the maximum angle the cable was free to adopt before coming up against the rubber-padded cuff around the edge of the hole, was called “the cable authority” over the aircraft. A large cable angle would send a large demand to the autopilot, referred to as the ASE (Auto-Stabilisation Equipment), to make the helicopter recover its correct flight attitude as rapidly as possible.
In the Wessex 31B there was only enough space to allow for the cable to swing ±12º fore-and-aft, (i.e. in pitch), and ±8º from side-to-side, (i.e. in roll). Such a limited space for cable movement was seen by the RAN as a major reduction in the control system’s authority to make large demands on the aircraft for corrective manoeuvres in drag-offs, and they were concerned that, in bad weather (wind, seas, currents), the system might not be able to keep the sonar near vertical or close to stationary in the water. The stability of the aircraft itself, when acting as part of the complete closed-loop system, “in the dip”, was also giving Navy cause for concern.
Other suggested problems were mentioned, such as a possible loss of system stability due to the use of a longer cable, which might curve unduly in ocean currents and winds, causing inputs not simply dependent on sonar transducer velocity or attitude.
All the conversion work had been studied for its feasibility by Westland Helicopters and plans had
been drawn up for the necessary modifications to be made to two 31A’s, initially, which were to be used for flight trials n the UK, to assess the success, or otherwise, of the new version. Then, if there were no unforeseen problems, the remaining 24 Mk 31A aircraft would be similarly converted to the new build-standard by Hawker de Havilland, Australia, at its Bankstown factory, near Sydney.
The Mk 31B would be the only Wessex of its kind in the world. The Royal Navy had ordered a very different new variant of the Wessex, to be known as the Wessex Mk 3, and its production development was also under way, but Australia had decided not to use the Mk 3, either because of some unsuitability for Australia’s purposes or perhaps because of the cost involved.
At the time of our meeting with Jack in December, the first 31A was under conversion in England.
Jack explained that for all these reasons, the RAN was concerned that there could well be serious technical problems during the conversion programme and the acceptance flying. He was uncertain as to which of the potential problems were likely to be real and serious. If possible, the RAN would like to engage SAD in a consultative capacity to help in identifying any important problems and how to solve them. It was desirable for any studies to be completed before the acceptance flying, which was scheduled for early 1967, but might well be delayed until late in 1967.
After explaining all this, Jack looked closely at each of us and told us that it had been largely at his suggestion that, after some preliminary studies, Navy had decided to upgrade its sonar sets and then to introduce the other related improvements.
‘Fellas, I’m in deep doo-doo over this! I need your help! It’s a case of cock-on-the-block! Do you think you can do anything to help?’
Those were his very words. We laughed at his way of putting it, but how could we refuse to do our best to solve the problem? Anyway, it all sounded pretty intriguing to me.
Alex turned and asked me, ‘Do you think you can sort this out, Ted? How would you tackle it?’
‘I would need to build models of the aerodynamics and the control system and try to isolate any likely source of trouble, Alex. I should like to think about it for a while to get to know the problem a bit better and just how I should tackle the modelling’, I explained.
Then I asked Jack, ‘Mr. Lonergan, could you send us some summary information on the cable-hover mode and let us know what formal documentation we can get hold of to find the details of the control system and the geometry of the aircraft?’
‘Sure, I can get you some stuff on all that and send it over when I get back to Canberra. I brought over a few sketches of how it works, so you can take a look at them first, OK?’, he replied.
After the meeting, Alex told me that he wanted me to tidy up the rest of my work on Bloodhound and take charge of this project in my own right. So this was to be my first chance to manage a major study project!
It was soon formally agreed that, in response to the approach by Navy, SAD would do all it could to assist and would allocate the task to SS(1) Group, which would form a small modelling team to begin the study.
The first stage of the work was to develop a mathematical model of the Wessex Mk 31A helicopter, cable and Type 194 sonar transducer, sufficient for prediction of the system’s dynamic behaviour in specified weather and sea conditions, but not including sonar acoustic signals. In the light of our experience with guided weapons modelling and simulation, it was considered that a mathematical model was an essential tool for solving the kinds of problems the Navy anticipated.
It was pointed out that the studies team would require extensive engineering data on system configuration and design details. Mr. Lonergan, as DNSS, undertook to try to provide such data as would be required.
The information I had asked for arrived and I studied it carefully. It included drawings of the aircraft, and other data, such as the masses of the aircraft and the rotor-blades, centre of gravity, rotor speeds and detailed drawings of the rotor-hub mechanisms. This was sufficient for the detailed model of the aircraft aerodynamics and kinematics to be formulated. Thus, these sections of the complete system model were founded on data known to be correct, so that validity in this area was entirely a matter of the reliability and accuracy of the complex physical theory used in the formulation of the model.
However, the flight control systems of the 31A and 31B (which are almost identical) involve a great many electronic, electro-mechanical, mechanical and hydraulic sub-systems. In this area the problem of acquiring reliable factual data on the sizes and values of so many different physical components was the formidable task, while, by comparison, the theoretical formulation of this section of the model was relatively easy.
In the first two months of the study I derived a fully dynamic, three-dimensional model of the aircraft’s aerodynamics, including all six degrees of freedom of body motion, plus main rotor and tail rotor flapping and rotational freedoms. My model also incorporated a new technique for prediction and simulation of rotor inflow behaviour, which was valid in any kind of manoeuvre, in wind gusts from any direction and for all flight conditions up to airspeeds of over sixty knots.
The model also incorporated the full body kinematics of the aircraft.
I then began work on the model of the sonar cable and transducer. This part of the system model had to be fully dynamic to allow simulation of system behaviour in rough seas and gusty conditions. I derived and formulated this model in a further two months. This area was again one where accurate and reliable data, giving a full description of the physical system, were available. But in this section of the system model, its validity is virtually assured, since it is derived entirely from classical mechanics.
From the outset of the study, work had been under way to collect the large body of data necessary to define the structure and logic of the flight control system. In this work I was ably assisted by Mr. Peter Benyon, a Senior Research Scientist (SRS) and fellow-member of SS(1) Group, who had a great deal more knowledge of electrical engineering than I had. The kinds of documents available for this work were largely unsatisfactory, either because they had been written for Navy use in servicing and maintenance, or because they had been hurriedly prepared, were out of date or out of context papers collected by Navy on various visits to contractors, each involved with a minor part of the system.
Much of the data collected was inaccurate or even self-contradictory. In several cases the required data could not be found at all. However, the functional form of the control system was discovered with a fair degree of certainty, thanks largely to the hard work of Peter Benyon.
The control system model was formulated accordingly and much of the numerical data was filled in with reasonable confidence, as a result of laborious cross-checking between the various available documents. The remainder of the numerical data was in some doubt.
Some further checks were made by comparing the control system model data in the cable mode, against similar data used in a very simple model built by Plessey (UK), some time earlier, for the Wessex Mk 1, which was the UK version of the 31A and was identical to it for this purpose. This gave us some coarse checks on several of the values of components in the hover-coupler. It also gave us good estimates of the stability margins of the aircraft in pitch and roll, which were of interest, as will be explained in a later section.
Visit to HMAS Albatross
After our preliminary study of the documentation, Jack suggested that Peter and I should visit 725 Squadron at Naval Air Station HMAS “Albatross”, in Nowra, New South Wales, in order to familiarise with the Wessex Mk 31A and to discuss various aspects of its behaviour, operation and maintenance with the officers of the squadron, and to collect various details of the mechanical and aerodynamic aspects of the aircraft.
So, in November 1965, I travelled, first with Peter Benyon and the next time on my own, to Nowra where we found out as much as we could about these things. I met the squadron commanding officer, Lt. Cdr. (Slug) Whitton and several other squadron members. One of these was Lt. Cdr. Peter Campbell, one of the senior pilots. Peter offered to take me up in a 31A on a familiarisation flight and I was, of course, keen to accept. After some difficulty with the question of whether I should be required to sign a “blood chit”, thereby absolving the Australian government of any liability in the event of my being injured, or whether I was automatically covered by virtue of the fact that I was to fly as part of my duty as a public servant, the latter was confirmed and I was ableto fly without signing away any of my rights.
Peter Campbell knew that I was an aeronautical engineer and that I had done quite a bit of flying in gliders and light aircraft, so he was happy to explain the normal flying duties of the helicopter pilot to me and to allow me to fly the Wessex myself, under his tutelage of course.
We did a few circuits of the area, during which he pointed out some fifteen or so bushfires in the hills surrounding Nowra, a few miles away. That was pretty normal for the time of year. He asked me to try to fly the aircraft straight and level, first with, and then without, the use of the automatic pilot (ASE). With the ASE on, it was a simple matter to keep it straight and level, but when I switched the ASE off, it was a tricky balancing act that demanded quite a lot of practice.
This did not surprise me, because I knew that all helicopters are, by their nature, only marginally stable. But it was surprising to see how steady the aircraft was when Peter flew it manually.
We then did several exercises at my request, to satisfy my curiosity. We hovered just a few feet above the runway and I learned how to climb and descend vertically. Then I flew the aircraft at various speeds, twenty feet or so above the runway. Finally, I asked him about the ability of the Wessex to fly backwards and he showed me how to perform this feat. Once I had tried it out and come back to the hover, I asked him how fast we could fly backwards. He explained the rules and the need to set a limit at just over 80 knots. He agreed to let me try this for myself and, starting from the threshold, I flew the Wessex backwards, at a height of thirty feet, at speeds up to 80 knots along the runway.
At one point about halfway down the runway, I turned briefly to glance out of the side window and, to my amazement, there was a crowd of naval ratings gathered in front of hangar number one, about 500 yards away, staring at our strange stunts with looks of utter disbelief on their faces.
Peter was a great guy, as far as I was concerned. He was a very handsome young fellow of about thirty, and totally professional in every way. He knew his stuff but was always modest, friendly and helpful. He invited me to join him and his wife, Diane, for dinner at his home the following evening. I was grateful for a taste of home away from home and accepted gladly. Diane turned out to be one of the rarest of gorgeous young women! She had lovely dark hair, long and soft, and she was so beautiful that I shall never forget how she looked. She had prepared a wonderful meal for us, the highlight of which was a magnificent Pavlova decorated with fresh kiwi-fruit and strawberries − one of my favourites.
While I was based at Nowra I was provided with a ‘cabin’ (bedroom) in the wardroom, which is the name the Navy gives to the Oofficers’ Mess. The wardroom at HMAS Albatross, Nowra, was like a large gentlemen’s club, with an excellent dining-room, bar area, billiard room, reading-room and comfortable individual cabins.
Subsequently, I was to make many visits to HMAS Albatross and was always made welcome and at home in the wardroom, where I met a good number of colourful characters among the Navy officers
Ramjet Model Completed
By January 1966, I had finished the work required to produce the comparisons between the Thor flight performance records and my model and I had plotted out the resulting graphs. Imagine my euphoria when I found that there was no discernible difference between any graph taken from engine behaviour and the corresponding graph produced by my model! I had done something no-one had ever done before!
Once I had this exciting proof that my model was correct, I hit upon another good idea. The form of the model was highly complex. After all, it accurately simulated every shock-wave, every fluid-flow process, including the internal boundary layers, the flame chemistry in the combustion chamber, the effects of fuel and air molecule dissociation at the high temperatures that occur during combustion and the behaviour of the transonic and supersonic flow regimes in the exhaust nozzle!
This complexity would clearly make the model difficult to use or to adapt to any major design changes which might make a new ramjet different from the family of engines my model was intended for. For example, if the model user was interested in adapting it to simulate a variable geometry ramjet.
My new idea was to produce a simplified form of the model by fitting curves to thrust, and other predictions coming out of the fundamental model. So I first ran the model over a wide range of flight speeds (i.e. Mach numbers), altitudes and fuel-to-air mixture ratios, and then I plotted the performance over these ranges of variables. Then I searched for simple mathematical functions that I could fit to the data. This technique yielded a new form of model that reproduced the full model behaviour with a high degree of accuracy and the fitted functions even revealed a new and interesting piece of understanding of the way the combustion efficiency behaved at very weak fuel- to-air mixtures.
By this time it was March. I added the new, simplified form of my model to the thesis, along with the experimental proof of the validity of my full model and I was now delighted with my final achievement. The world now had a simple way to predict ramjet behaviour and it had been proved to work accurately. I re-submitted the thesis in May, 1966.
Completing the Helicopter Model
Requests for further information to help us to clear up the remaining doubtful items were sent to Westlands in Yeovil, UK, in the form of a series of specific questions. The reply was that the information could best be supplied if a member of our project team could visit Yeovil in person to discuss the queries. Approval for an overseas visit was therefore sought and Jack Lonergan felt it would be advisable to visit, in addition, other companies, such as Louis Newmark (UK), Sikorsky Aircraft (US), David Taylor Model Basin (US) and Bendix Pacific (US), in order to cover other areas, such as the AQS 13 hydrodynamics data, ASE data and hover-coupler data, as well as to learn more about what other problems might be expected to arise.
I was the logical person to make these visits, which were also to take me to Plessey (UK). The visits took place in September and October, 1966. But before I left, by August 1966, the bulk of the model had been built and the programming of it to run on our IBM 7090 mainframe computer was largely complete. However, it still needed a few minor refinements and the values of several of the control system components had yet to be found and checked on the computer against tests and measurements to be made on the helicopter.
By August 1966 the complete system model had been formulated. There still existed areas of uncertainty concernining data values, largely for the accurate definition of flight control system components and cable and sonar transducer geometry and masses.
The system model was at first set up on the computer to simulate the Wessex 31A with the early sonar/cable system, and was flying and behaving much like the real 31A did. However, it was mildly dynamically unstable in pitch and roll during cable hover, unlike the real 31A, and I was not yet sure why.
I made checks on the programming and plotted stability charts based on the equations of the model. These checks proved that the instability was not due to any programming errors but was inherent in the equations of the system model. Our April visit to HMAS Albatross, at Nowra, had shown us that the 31A was dynamically stable, although not very, in all modes of operation, including in the cable hover mode (i.e. “in the dip”), so it was clear that there were still some important differences between the model and the real Wessex, which would have to be found.
Visits to UK and USA
On Wednesday, 14 September 1966, I flew overseas to try to find the source of the errors causing the instability of the model, as distinct from the real Wessex Mk 31A.
It was arranged that Lt. Cdr. Oscar J. Hughes, RAN, the Wessex Conversion Project Officer based at Yeovil, would assist me at Westlands, where he was posted and knew the right people to see there about our problems. He would then escort me on my various USA visits, as he was already familiar with the key people in the US companies I was to call upon, and could ensure that I saw those most able to assist us.
After what was my second charter flight via Cocos, I attended the usual briefings at Australia House for discussions with Cdr. N.E. Lee (Staff Officer, Air) and Lt. Cdr. J. Duff, both members of the staff of ANRUK (Australian Naval Representative, UK). Lt. Cdr. Hughes was also there to meet me. Later, at Castlewood House, I met Mr. Leo Cohen, the WRE Representative in the UK, to brief him on my visits.
At both meetings we discussed progress with the Wessex/Sonar modelling project, and our problems in trying to collect accurate numerical values of ASE components. I explained that I hoped to unearth the data we needed during my visits in the UK and the USA, that my itinerary had been agreed at ANRUK and that Oscar was to accompany me on all these visits to ensure that I was able to see the best people and to support me in my task.
Lt. Cdr. Lee felt strongly that I should amend my departure for the USA from Sunday 2nd of October to Saturday 1st , to enable us to settle into our hotel and so that I could meet the Australian Naval Attaché and his staff socially, in Washington on Sunday 2nd. My travel bookings were altered to fit in with this.
Also on the Thursday morning, I despatched several sets of model equations and flow-charts to Sikorsky Aircraft, Bendix (Pacific) and The David Taylor Model Basin, via the Australian Defence R&D Attaché, Washington, together with a letter explaining where to send them.
Oscar and I travelled to Yeovil, in Somerset, together, the next day. On our way we discussed the project, our visit plans and how best to try to get the data we needed. I found Oscar to be a bright, fast-moving young bachelor with a degree in Electrical Engineering. He was good-looking, quick-witted, perceptive, self-assured and thorough in his planning. He was able to be either polite and respectful or a precocious leg-puller, as the occasion required. But he was perhaps a little too sure of his own ability to make a quick appraisal of a complicated technical problem. Jack Lonergan had told me that Oscar was highly thought of in Navy and was “earmarked” for rapid promotion. His prophecy was right on the ball, as time was to show.
That afternoon, we attended a meeting at Westlands with Messrs. J. Speechley, the Chief Designer, G. Dillaway, the Chief Systems Engineer and R. Gray, the Wessex Conversion Project Engineer. We discussed our modelling and what could be done to assist us.
I outlined the stage our project had reached, itemising the types of information I was hoping to find with their help. Mr. Speechley assured me that Westlands would give me every possible assistance. Our model was of great interest to the meeting and I was questioned about its versatility, degree of simplification and capabilities. Dillaway and Gray were very keen to encourage our activity, while Speechley seemed pessimistic and hard to persuade that modelling would help to produce a better understanding of aircraft behaviour. I saw this as the attitude of a Luddite, I’m afraid.
We were given full co-operation but it was not a simple matter to locate the many items of data we needed. None of the staff had a thorough, all-round systems engineer’s familiarity with the design detail or even the control principles which determined the Mk 31A, or 31B, ASW system stability.
Westland staff were heavily committed to the conversion and development work for the Royal Navy’s Mk 3 Wessex, in addition to their commitments on the Mk 31B. In any case they were not in a position to use the kind of data required for detailed modelling and so did not have much data in a ready-to-use form. However, we were given copies of some useful drawings and test schedules, which would later yield some useful checks. But we gathered little of major value there and one of the important figures we did get turned out to be incorrect.
I did at least manage to confirm the detailed switching logic in the hover-coupler with Dillaway, after spending one entire afternoon with him while he dug out the details, first deciding that we had it wrong and finally realising he had made some errors and that we were correct after all!
On the Tuesday afternoon I met Mr. J. Mackenzie, the Chief Aerodynamicist and Mr. B. Pitkin of the aerodynamics section for a detailed discussion of the aerodynamic model. We were in complete agreement on the validity of this part of the model and I was promised some recordings of in-flight measurements against which to check its behaviour.
Before I left on Tuesday 20th, to visit Louis Newmark’s at Croydon, I left Dillaway a list of drawings, reports, papers and recordings which he agreed to collect for me prior to my return the following Monday.
While in Yeovil, I stayed at the “Pickety Witch”, a small but pleasant bed-and-breakfast hotel. Oscar had been staying there during his time with Westlands. In the evenings he and his friends took me out to play skittles and nine-pin bowling, and to a local pub called “The Rummer” where we had a few beers and met up with the young crowd, many of them being from Westlands.
The pub was crowded every evening, with people standing pretty much shoulder-to-shoulder in the bar. Oscar was very keen on a young lady he often saw there. Her name was Mary and she worked at Westlands too and usually turned up with a few of her office friends.
I asked Oscar why he didn’t go over and chat to her. It seemed he was too nervous! So, saying that I would fix it for him, I wandered over next to her and introduced myself to her group. Some of them were aware of my visit and all seemed to be at ease with my joining their discussion. After a couple of minutes, I drew Mary aside, asking her if I might speak to her about something personal. She didn’t seem to mind, so I told her that my good friend, Oscar, had been suffering for weeks with a terrible crush on her and that he was too shy to approach her. She was astounded!
‘Really? Are you kidding me?’, she asked.
‘No, it’s true, I swear!’, I assured her. ‘I’m worried that he’s starting to let it affect his work! What do you think?’, I asked. ‘Would it embarrass you if I asked him to come over?’
She told me she had seen him at the office and that he looked good in his uniform! So I offered to introduce them, to which she responded ‘OK, why not?’.
So I went back to Oscar and explained that Mary wanted me to introduce them.
‘What did you say to her? You didn’t say anything funny about me, I hope?’, he bumbled, nervously.
‘Come on, mate, never mind that! I think you’re in here, Oscar m’boy!’
After I introduced them they were never apart all evening, and Oscar finally drove her home in his pride and joy, the Ford Cortina GT.
The next morning at breakfast, Oscar didn’t turn up until we were all leaving the dining-room. He was looking decidedly haggard and semi-comatose, but he had a happy look on his face. He was, of course, leg-pulled for days about that, but, before we left for the USA, they had become engaged! They were married shortly after Oscar’s return to England. It seems I was the match-maker!
The visit to Louis Newmark’s was one of the most informative of my entire mission. I had two full days of detailed discussions and checking of the hover-coupler model against the hover-coupler flow-charts produced by its designers at Donner Scientific (USA). We established that the model logic was all correct but we found several corrections to component values used in the model. It turned out later that one or two of these were of some importance, others were not and the rest were simply misconstrued as a result of our misinterpreting Louis Newmark specifications.
The SAD modelling work fascinated the staff and they were most interested in our computer simulation and optimisation capabilities. The view was put to me more than once that SAD might well act as a technical centre for all future helicopter-borne ASW design, evaluation and optimisation work in the Commonwealth countries and that this would be most desirable. While I conceded that this might well be so some day, I explained that, at present, SAD was engaged by the RAN simply as a scientific consultant on the Wessex Mk 31B sonar study.
We left the company, after exchanging addresses for further communications, late on the afternoon of Friday 23rd.
The Monday afternoon and Tuesday at Westlands were fairly uneventful. I did collect some documents and a set of measurements that Dillaway had made for me during my absence, and I arranged to have some others made of the responses of the secondary servos in the ASE. We also discussed some minor features of rotor-blade aerodynamics. On Tuesday I met him again to collect a series of in-flight measurements he had found for me.
I then met Mr. M Harrison, Chief Research Aerodynamicist, for a wide-ranging discussion of helicopter aerodynamics topics, including rotor inflow theory, how the inflow is affected by translational motion and a number of minor corrections we might want to consider.
On Wednesday, Oscar and I met to discuss the progress I had made so far on my visits. My conclusion was that only minor corrections had arisen, none of which was likely to affect the stability of the model.
Later that morning I received a phone call from a Cdr. Grant, RN. He told me that a Mr. C. Shaw, the BDRSS (British Defence Research Scientific Service) representative from Salisbury, had just arrived in London and had advocated that the Royal Navy should consider asking SAD to carry out similar consultative studies, on their ASW helicopter systems, as we were providing to the RAN. He asked me to try to meet him in London that week to discuss the feasibility of this proposal. After a few words on the matter by phone, I agreed to meet him at Australia House that Friday afternoon. Then I telephoned Mr. Herrington, the Senior Representative at Australia House to advise him of the matter. He expressed great interest and asked me to take notes at the Friday meeting and send them to him so that he could study the situation.
I spent the afternoon with Mr. J. Plowman, the Chief Electrical Designer, to check out some autopilot gain settings. I collected from him a sheet of old Donner Scientific Company overall gain check figures used for control system and hover-coupler tests.
Thursday was almost entirely wasted as Dillaway and I spent a great deal of time trying to check the secondary servo mechanical linkage geometry and to establish overall gain checks for validating the control system model. This was, again, a waste of time, because he was clearly unfamiliar with the detail of the mechanisms and had difficulty in trying to locate dimensions of components. Eventually, he gave me incorrect information, radically different from the model of the servo, and did not agree with the RAN Air Publications, which were originally produced by Westlands! I was sceptical and asked him to be absolutely sure. He did some further checks and insisted that his figures were accurate. It was not until I visited Sikorsky in the USA that I was able to confirm that the figures given in RAN Air Publications were correct and, therefore, so was the SAD model.
What little correct information I did collect was of almost no value for model improvement.
Later in the day, I visited the assembly shops with Lt. (Slug) Whitton, RAN, the official observer for the Wessex conversion project and inspected at first-hand the first of the two RAN aircraft being fitted with its conversion equipment.
On the Friday, as it was clear that I was not going to be able to check the whole control system model while I was in the UK, I made up a list of the additional items of information I needed to collect, and gave it to Oscar to collect and forward to me on his return from the USA. Oscar agreed to do all he could to get the data and send it on.
Before leaving Yeovil at 11 a.m., I made a point of thanking each of the people who had gone out of their way to make my visit worthwhile.
I returned to Australia House in the afternoon to finalise my amended travel arrangements and I spent some time with Cdr. Grant, RN. We discussed his proposal that WRE should undertake, under the existing Joint Project arrangements, helicopter/sonar studies for the scientific evaluation of Royal Navy ASW helicopter systems. As I have said, Mr. C. Shaw of BDRSS (British Defence Research Scientific Service) had suggested that similar studies should be conducted by WRE for the Royal Navy as those already being performed for the RAN.
Cdr. Grant told me that the RN had ordered Wessex Mk 3 aircraft fitted with Plessey 195 sonar sets and Sikorsky SH3-D (i.e. S 61) Sea King helicopters fitted with AQS 13 sonars. The stage reached in the development of the Wessex 3/195 systems was very similar to that of the Wessex Mk 31A/AQS 13 conversion project. Test flying and delivery dates even seemed to be about the same, give or take a month. The Sea King programme was about a year behind the others.
He believed that the proposed studies were highly desirable but it might be a bit late to start them for the Mk 3 because any useful results would have to be available by mid-‘67 at the latest, but preferably by January ’67. However, he thought the time was opportune to begin the studies on the Sea King for which results would not be required until much later. He asked me about the degree of validity we could expect to achieve in the model, and for some idea of the time it would take to complete such a study.
I told him we were obliged to give the current RAN work priority but that the proposed RN studies were a sound idea and could be completed with the existing model and facilities. I outlined the high degree of detail and versatility of the SAD model and he was impressed and keen to have the model used to evaluate the RN aircraft. I explained that it would be necessary for us to carry out a similar overseas mission to gather data for the MK 3 and the Sea King and that SAD would need a clear statement of the problem areas which the RN wanted us to investigate. He said that would be a simple matter. I also assured him that once we had found all the control system description data, it would be a very short task to set up a realistic simulation facility. But there would be administrative delays in setting up the arrangements, which could well amount to several months.
He then said that, even if the results for the MK 3 study were not available until late ’67, they could well be worthwhile for various reasons, such as improvements in operating procedures. I gave him my rough guess at the likely costs of the studies and he thought these were very low, as I now think they probably were.
He promised to prepare a submission immediately to initiate proceedings through the RN and BDRSS London, in which WRE would be formally requested to undertake specific detailed studies.
Before leaving Australia House, I gave a debriefing on my UK visits to the staff of ANRUK, who expressed the view that the visits had been well worthwhile. Oscar formally requested that he should be sent copies of the minutes of all future project progress meetings.
The next morning I checked out of my hotel and met Oscar at the airport for our flight to the USA. It turned out that he had booked his flight on PanAm’s First Class “Royal Ambassador” service.
For Australian public servants, it was then normal to fly first-class when on business, but we were expected to fly with QANTAS, or an airline of any other British Commonwealth country, such as British Airways, or Air Canada, if there was a choice. I had been booked to fly with British Airways. Oscar, in a rather cavalier fashion, told me,
‘Oh, don’t worry about that, I always fly with PanAm, they give you much better service! Come on, we’ll go and get your tickets endorsed over to PanAm so we can fly together.’
British Airways obliged me without hesitation and so Oscar and I found our first-class departure lounge and took a seat to await our boarding call.
The next morning I had a meeting at the Australian Embassy with Dr. R.I. Garrod, the Defence R&D Attaché, together with Oscar and Tony Hunt. We discussed the arrangements for my visits in Washington. It was suggested that Oscar and I should visit the US Naval Air Test Centre at Patuxent River, on Chesapeake Bay, the next morning. My visit plan had room for this extra item and Oscar wanted to make the visit anyway. As it would probably give me some useful background on the functioning, and some of the operational problems encountered with US helicopter/ASW systems, I agreed, and the security clearances were quickly arranged.
During the Monday afternoon, Oscar, Tony and I made our visit to the David Taylor Model Basin at Silver Springs, in Maryland.
We were given a tour of the facilities and shown some films of tests which had been carried out on the behaviour of the Bendix AQS 13 sonar in one of their vast test tanks.
The tour was most impressive, as the water tanks, which were all indoors, and the testing facilities installed there, were enormous, technically advanced and extremely well equipped with modern instrumentation. The establishment was one whose description must be filled with superlatives. The main test tank looked like an indoor lake and the experimenters had full control of its water currents, wind speeds and the huge waves that can be sent across it when testing ships, sonars orany other water-borne equipment.
Some of the tests on the AQS 13 were done on scaled-down models and others on the real sonar. In every case the sonar was suspended in the water, from an overhead support, by a cable (scaled or real, as the case required) while winds and currents of various speeds were introduced.
The tests showed a cable angle of 5º at half a knot of steady current, 20º at about one knot and 45º at between one and a half and two knots. Each angle was almost constant along the entire cable. The transducer angle seemed to be about ¾ of this angle throughout. I questioned the staff about whether they had any data on virtual mass of the sonar in water or details of the flow through the structure of the sonar, but all they had was what we had already found out at WRE.
Although this visit gave me very little data for direct use in the model, it did give me a good idea of the scale of the effects of wind and current on the cable and the transducer.
Before we left, I was given a beautifully made 0.18 scale model of the AQS 13 and cable, to take back with me.
On Tuesday morning, after a brief visit to the Embassy to keep the Australian R&D Attaché informed of progress, Oscar and I took a Greyhound coach journey, of about eighty miles, to Patuxent River, on Chesapeake Bay, to visit the US Naval Air Test Centre.
I was sitting next to a young African-American woman who was nursing a very small baby with a bad cold and a runny nose. The mother seemed to have some problem which meant that she frequently needed to visit the toilet at the rear of the coach. She hadn’t spoken to me at all, yet each time she had to go, she dumped the baby in my arms, with hardly a word, except, ‘Y’all hol’ ma chahl!’, and climbed over me to make a run for it. I found this amusing and supposed it to be less presumptuous there in the US than it would have been in Australia.
We had no difficulty gaining access to the base, since the usual arrangements had been made for us by the staff of the Naval Attaché.
Oscar was interested in the SH3-D (Sea King) and its dunking trials with the AQS 13. As I had been told, the RAN was concerned about the stability of the cable and sonar during hoisting and lowering operations, and we found out quite a bit of useful information on what was being learned about this in the USA.
I was shown some pen-recordings made during technical evaluation trials over Chesapeake Bay with the SH3-D, dunking an AQS 13 to 100 and 200 feet. The recordings plotted cable angle history from the time of sonar release and for three or four minutes thereafter. Each trial showed the cable going into a long, slow, lightly-damped oscillation which took over two minutes to settle down enough for acoustic soundings to be worth taking;- hardly acceptable in a combat situation! The cable always started on the aft rim of the funnel opening, stayed there for ten to twenty seconds, then moved to the forward rim, again for ten to twenty seconds, and then it swung back and forth at a period of about ten to twenty seconds without touching the rim. The oscillations were very lightly damped, indicating that the complete system was only slightly stable!
This told me that the control system of even this much more modern aircraft, had been set up with too much feedback gain in the cable mode of hover, a fact I was only beginning to understand myself, and which was not yet well understood in the UK either. Apparently it was not yet properly understood even in the USA!
We were also shown cine-films of SH3-D sonar hoisting tests in various sea-states and winds, which were similar to what we had seen at the David Taylor Model Basin. It was clear that there was a problem, in that, if the sonar was hoisted when the cable was at a large angle from vertical, it could swing violently and even do serious damage to the underside of the helicopter. This was being averted by moving the aircraft forward slowly as the sonar was raised. This damps out the oscillations during the hoist quite effectively.
The old question was again raised of whether we should consider including the sonar hoisting and lowering dynamics in the SAD model. It seemed to me that this would involve a great deal more work for very little benefit and I was against it. Clearly, the thing was to see to it that the overall system was made properly stable and then the cable swinging would be minimal, as it had been during the era of successful operation of the Wessex Mk 31A/ Plessey 194 system.
After getting approval from our Defence R&D Attaché, Dr. Garrod, on Wednesday morning, I made a brief courtesy visit to the Canadian Defence Headquarters in Washington, where I had an informal chat with Cdr. R.J. Legeer, the Electrical Staff Officer with the RCN Attaché. The Canadians were operating Sikorsky SH3-D/AQS 13 systems with an advanced Doppler radar system designed by Canadian Marconi, and were recognised as being well advanced in the helicopter/ASW field, so I thought it was a good idea to establish contact with the RCN so that mutually beneficial information could be exchanged.
Cdr. Legeer made me welcome and showed great interest in the SAD helicopter/ASW modelling studies. We both agreed to make formal recommendations to have our respective organisations included in each other’s R&D report distribution lists. He took the address of our Chief Defence Scientist and I understood that he would make a formal application through the RCN Attaché.
In the afternoon, Oscar Hughes, Tony Hunt and I visited the Pentagon to see Rear Admiral E.W. Dobie, USN, in the office of the Chief of Naval Operations. The Admiral had set up our visit through the offices of our Naval and Defence R&D Attachés.
He took a personal interest in the RAN’s problems with the AQS 13 and wished to discuss our system studies efforts. He was clearly well informed on developments in the Wessex conversion project and was even aware of our system modelling work. He was hard to convince of the value of mathematical models in general, preferring to see evaluation carried out on real systems. We had an amicable discussion on this and I explained some of the major benefits of the model studies approach, especially for investigation of the effectiveness or otherwise of proposed design improvements, but also in saving the enormous costs of expending very expensive missile systems or putting expensive combat systems into dangerous experiments. I also pointed out that it was often impossible to evaluate a weapon system’s performanve against a target, such as a bomber, belonging to a potential enemy, because the other side was not likely to supply a target for use in such trials. But this type of evaluation was done by SAD with great accuracy by means of model simulations. To his credit, he seemed to appreciate the merit of my arguments. Before we left, he was kind enough to assure us that USN assistance would be given if we needed any information.
That evening, Oscar and I flew to Bridgeport, Connecticut, then drove to Stratford, where we werecollected the next morning by Mr. P. Torry and driven to the Sikorsky Aircraft Plant. There we met Mr. S. Orndorff, Supervisor of Systems Engineering, and Messrs. C. Wittmer, P. Adams and J.R. Maciolek, of Armament and Control Section, Systems Design and Development Branch.
When I asked whether Sikorsky used mathematical models in the design and development of its helicopters, Charlie Wittmer told me they did, but that their models were extremely simple. He showed me a linearised model he had been using for design work on the SH3-D helicopter and thought he should be able to dig out a similar model for the S 58 aerodynamics and control system.
The remainder of Thursday afternoon was spent searching through microfilm indexes to find and reprint component drawings I needed to establish the geometry of the mechanical feedback linkages in the control system of the S 58. I had to check the disconcerting information given to me by Dillaway at Westlands, which implied a need for radical changes in the set-up of our Wessex 31A model. By late afternoon we had established with certainty that Dillaway’s information was not correct for the S 58 and that the actual geometry corresponded exactly with the Wessex 31A data in the RAN Air Publications, as produced for the RAN by Westlands themselves! Thus it was clear that Westlands had not redesigned this system, that the information given to me by Dillaway was wrong and that our model had been correct in this respect all along!
On Friday I discussed aerodynamic modelling with Joe Maciolek in the vast open-plan design office where he worked. He showed me a variety of models but each of them was highly restricted in comparison to our model. Some were only for single-plane motion. They had some for the pitch plane and others for the roll plane. Another could only simulate vertical motion. These were all linearised and suited to simulating only small disturbances to the aircraft motion at specific speeds. Wind gusts had to be very small or the model would give incorrect results, and so on.
When I described the SAD model and its great versatility for realistic simulation, in all planes simultaneously, and for almost any speed or any size of disturbance, to Joe and his colleagues, this aroused great interest and was much discussed. Unfortunately, the model specification papers I had sent them on the 15th September, via the Defence R&D Attaché, had only arrived at Stratford the previous day and so the staff had not yet been able to study them.
Joe and the others were crowded around me as I sat at one of the office desks and they all wanted to know whether they could get copies of the reports on our model so that they could set it up and use it in their own design work. I told them about the papers I had already sent and showed them copies of each of the technical papers setting out the various sections of our model. I told them that we were all members of the same ‘defence club’ and that we in Australia were only too pleased to have an opportunity to pay something towards our ‘club dues’ and, so saying, I presented them with a set of the publications there and then, upon which I took them on a brief tour of each paper, to show them what it contained and how to use the model to build a simulation programme.
This was all gratefully received and I was asked to send them a copy of the software and the language manual for the SIMTRAN simulation language we had built in SAD and which we had used to implement the Wessex model, among many others, for our simulation studies. I sent all this material upon my return to SAD.
I was given every assistance with my enquiries and treated in a most friendly way. This may have been, in part, because we at SAD were seen by Sikorsky as, in effect, a part of the Australian Navy, which was a likely customer for the SH3-D helicopter, and I guess they were eager to make a potential customer happy.
It was a great honour for me that one of the world’s greatest − if not the greatest − designers and manufacturers of helicopters, should find my work so valuable that its staff planned to use it for their future helicopter design and development studies, in preference to their own models.
I was also grateful when Joe Maciolek explained some of the subtle technology built into the Sikorsky helicopters, such as a clever method they used to prevent the tail rotor from exciting dangerous resonant vibrations in the rear fuselage structure of the aircraft.
Oscar and I were then taken on a comprehensive tour of the vast manufacturing plant. This was extremely impressive and most absorbing for someone as aircraft crazy as I was.
Later in the afternoon, I collected up all the component drawings, flow diagrams and sketches I had been given. I also discussed cable/sonar modelling with Charlie Wittmer. I telephoned a message to Washington for teletype despatch to SAD about the verified secondary servo data and swapped addresses for future communications. After thanking our hosts for their warm welcome and valuable assistance, Oscar and I then took our leave.
After an otherwise uneventful flight, I arrived in Montreal and had no difficulty in meeting up with Mike. We were both highly pleased to see each other again after ten years or more and Mike told me that he had already bought me a return ticket for my Montreal-Ottawa journey. We boarded our flight and didn’t stop talking until he rang the front door-bell of his house and Sylvia came to open it for us. However, it seemed that my luggage had not made the flight (no wonder!) and I was told that it would be delivered to me at Mike’s home later in the evening. And so it was, to my amazement.
We spent a really wonderful weekend together, visiting the picturesque lakes and hills of the Gatineau Ranges, forested with every kind of conifer, sycamore, birch, elm and maple in every colour of autumn. We walked around the city centre, Parliament House, the architectural splendour of the National Art Gallery and the Observatory. We stood looking down on the Rideau canal from a very high cliff-edge as millions of timber logs drifted slowly past on their way to the mill.
I said my farewells to my friends on the Sunday evening and flew back to Montreal where I boarded my American Airlines flight to LA.
On arrival in LA, I took a cab to the hotel we were all to stay at − The Sportsman’s Lodge, on Ventura Boulevard, Coldwater Canyon – met Oscar to arrange our plans for the following morning and turned in early for a sound night’s sleep.
Next morning, I wandered down to the poolside coffee shop and had a really American breakfast of blueberry hotcakes with crispy bacon and maple syrup on the side, and a fantastic mug of black coffee. As I was about to finish this, Oscar arrived with a Mr. H. Bailey of Bendix (Pacific), who had come to collect us and drive us to the plant in North Hollywood.
Once there, he introduced us to Messrs. Danner, Urell, Snyder (Simulation Section), Banghart (Systems Design) and Fred Lundquist, the Bendix International (Washington) Representative.
Once again, our model statement papers had not yet arrived! Clearly someone on our side had not been very diligent in forwarding this important material.
Mr. Bailey showed us around and I was able to collect a drawing of the AQS-13 sonar transducer.
I discussed the hydrodynamics of the AQS 13 sonar transducer with the above members of the staff of Bendix, but I discovered that they were far more concerned with its vertical motion through the sea during lowering and raising, than with its behaviour in lateral motion, and that very little was known about the horizontal flow through the structure of the sonar or of its virtual mass in water.
Mr. Snyder showed me an analogue simulator they used for studying towed, passive sonar bodies. This included a model of the helicopter aerodynamics and control system which was none other than the crude, simplified model used, and supplied to them complete, by Sikorsky’s, plus the cable and sonar dynamics and the acoustic signalling system.
When I enquired about the ‘dynamic’ model of the cable motion, I was assured that it was fully representative of the kinematics and fluid dynamic forces acting on the cable and its towed body. It was operated in real time too, so I was keen to compare the model equations with ours. However, on investigation, I found that it was not a dynamic model at all but simply a steady-state model in which the steady-state cable catenary was re-calculated at each time-step in the simulation.
When I explained the limitations of this approach, Snyder was keen to see if he could use our cable model. So I gave him our derivation notes to photo-copy so that he would be able to follow the model equations when they eventually arrived at Bendix. He was also keen to have a copy of our
SIMTRAN simulation language manual and the corresponding language translator software so that his people would be able to set up our cable simulation on the IBM 7090 mainframe at Bendix.
On the Tuesday morning I spent some time discussing the acoustic functioning and signal- processing aspects of the AQS 13 to get a better understanding of how the sonar tilt angle affects the usefulness and accuracy of the processed acoustic data. As a result, I gained a much better appreciation of the need for tilt to be controlled in various operational situations.
None of this was of any help to me in my task of correcting the stability characteristics of our Wessex model. It seemed, once again, that the major beneficiary of my visit was to be my host.
There was nothing more I could contribute or learn there, so, after lunch, I exchanged addresses, said my thanks and farewells, and took my leave, rather than hang around making a nuisance of myself.
It was already clear to me that my extensive travel and investigation efforts had yielded only enough knowledge to allow me to verify part of the control system model and to effect some minor corrections to other sections of it. All I had proved, really, was that no one organisation had a sufficiently complete set of information about the Wessex 31A to be able to provide us with answers to all the questions which were vital if we were to make our system model fully valid and reliable for our purposes, as the only consultants available to solve the RAN’s problems.
I was going to have to find another way to answer many remaining questions.
The afternoon weather was glorious, so when we returned to the hotel, we freshened up, donned casual dress and relaxed on poolside banana lounges to have a cool drink, chew over the results of our visits and talk about what we were planning to do next.
The pool area of the Sportsman’s Lodge was something special. It was a great place to relax after a day’s work. Not only was it quiet on weekday afternoons, and glamorous, but every couple of minutes a few delightful young beauties in skimpy bikinis and very high heels would wander past, between us and the pool, often casting unnecessary glances our way. Now, it will surprise no-one to hear that young bachelor Naval officers found this sort of thing animating, but I can attest that a young married scientist can experience a very similar response, especially after several weeks in foreign lands, away from home comforts!
The next day, Wednesday, I took a bus to Disneyland and spent several hours there. I rode in the very front upstairs seat on the mono-rail and had a fantastic view straight ahead as I went to every part of that fabulous park. I bought Mickey Mouse hats and various souvenirs for Robbie and Sue and had my first taste of pistachio nuts in an ice-cream sundae at the bar of a soda-fountain in “Main Street USA” while a brass band in dark-green and gold striped uniforms marched past the open front of the store.
My sundae took so long to arrive that I had only two minutes to eat what I could before I had to dash for the mono-rail, in order to connect with the bus, that would take me to LA International Airport to catch my flight to Hawaii, on my way back to Australia. But, at least I did get to taste the pistachios I had only heard about through movies and TV, and had always longed to try.
Luckily, I made it on time and as I settled back into my first-class seat on the Jumbo-jet, I wondered what it was going to be like to visit Hawaii, where I was entitled to a 24-hour rest break.
Hawaii is the name of the state, which is made up of several islands, of which the largest is called Hawaii, but the capital is the city of Honolulu, which is situated on the island of Oahu. My hotel had been booked for me by the Embassy, and it was in Honolulu.
I spent an enjoyable break in Honolulu, seeing the sights, including some open-air shooting for the TV series “Hawaii Five-O”, then, on Thursday evening, I flew on the next leg, to Sydney via Fiji, where we stopped for an hour or so to refuel and to exchange a few passengers. While there, I bought a beautiful necklace of jet-black, shiny, coral beads for Pat.
My flight arrived in Sydney at about 7 a.m. n Saturday 15 October and after a wait, I boarded the morning flight to Adelaide. The journey was over. The excitement was past. The search was complete. But my task was not!
Back at work in SAD, I analysed all of the information I had collected and made a few indicated minor adjustments to our model of the Wessex 31A and its cable/sonar system.
There was no perceptible change in the mild instability of the model, although a few minor effects were simulated better. My analysis of the large quantity of literature I had collected began early in November 1966 and took months to complete.
At this stage, we learned that slippage had occurred in the UK work on the Wessex conversion and that it was now not expected to be finished until April 1967.
Concerned about the elusiveness of the cause of the model instability, I decided to start a series of thorough checks on all the work we had done so far.
Firstly, I linearised the aerodynamic model and compared it with the equivalent linearised model given to me by Sikorsky Aircraft. The agreement was very close. However, I made a minor adjustment to the rotor aerodynamic damping in the hover, as this had been suggested by Sikorskys. This had no appreciable effect on model behaviour either.
Next, I simplified a copy of the full system model, incorporating all of the simplifying assumptions made in the Plessey model. The stability behaviour of my simple model was compared against that of the Plessey model and the agreement I obtained was good. The odd thing was that no one stage of the simplification seemed to cause much of the change from the poor stability of our full model to the greater stability of the Plessey model.
These two sets of checks confirmed that the cause of the instability of the full model was not to be found in the aerodynamic model, nor in its computer programming. They also confirmed our earlier assessment that there were still serious errors in the control system model data, in spite of all our efforts to gather the correct data. Also, the hover-coupler model had been largely confirmed by the staff of Louis Newmarks. Suspicion was therefore beginning to fall on the autopilot (ASE) and flying controls area.
To study the nature of the mechanism causing the instability, I analysed the frequency response characteristics of the linearised Plessey model. The results showed plainly that the gain of the pitch hover coupler output stage was the obvious thing to adjust to improve system stability in pitch and, by analogy, the same would be true in roll. Reduced gain led to increased stability.
Glancing over my notes on the April 1966 flying I did in the Mk 31A at Nowra, it appeared that a reduction in this gain of about 20% would give the Plessey model the correct degree of stability.
I wondered if there might have been some confusion in Plessey’s estimation of the effective gain of the hover coupler output stage magnetic modulator. Maybe its effective gain was lower than stated because of some sort of ‘form factor’ error in its output carrier. I also realised that it would take a bit more than 20% reduction in gain to make our system model have the correct degree of stability. Furthermore, as I had already deduced − contrary to the popularly held view − if the cable funnel floor-opening was to be reduced in size then, increasing the cable pick-off gain in order to compensate for the smaller opening, would make the aircraft less stable, so any increase in cable capture time (or slower “drag-off” recovery) with the smaller opening, would simply have to be accepted.
The only way to be certain of my conclusions about the hover-coupler output gains, was to return to Nowra to measure them and any other doubtful quantities which we could measure with the helicopter on the ground.
These views were formally distributed to the RAN and to the Wessex Conversion Project Officer (Oscar Hughes) in January 1967. During the preceding few weeks, flight tests on the first of the converted Wessex Mk31B aircraft had been under way in the UK. The cable pick-off gains, or the hover coupler output gains (which have the same effects in cable hover), had been increased to compensate for the reduced size of the cable-funnel opening. This had caused instability. Not only that, but the excessive signal voltages engendered in the hover coupler electronics were found to cause a serious increase in frequency of component failures, thus reducing aircraft reliability.
We were advised that Westlands had tried making adjustments to various features of the system in their attempts to improve stability, but with no success, as I expected.
When Oscar passed on our recommendation to try reducing the gains, this was seen as being in contradiction of the prevailing theory that the gains must be increased to increase the ‘cable authority’ over the control system, apparently in disregard for aircraft stability!
By that time, I was convinced that Westlands had failed to understand the nature of the effect on stability of increasing feedback gains, but perhaps they were driven to make sure that the recovery of the aircraft from a large disturbance to the tilt of the cable, would be no worse than it had been with the Mk31A, as it was a requirement of their contract with the RAN that ‘cable authority’ must be no less than it was with the Mk31A.
Among the first few things we measured on a Mk31A at Nowra, in March 1967, was how large the cable angle had to be to force the autopilot to go ‘hard over’, that is, to make its maximum possible demand on the control system’s servos for the recovery manoeuvre. We were very surprised to find that a 13 degree cable movement was enough to give full servo-motor travel from centre to ‘hard over’. In other words, full authority was already obtained at an angle of only 13 degrees!
This meant that, even in the Mk31A, the last 7 degrees of cable movement produced no further increase in the demand for corrective manoeuvre by the aircraft. Consequently, the concerns over the reduced size of the funnel-opening had been unfounded!
We relayed this information to Westlands, via Oscar Hughes, and it was of considerable help to them. They had apparently been under a misapprehension about the matter. Largely as a result of this advice, and in view of our earlier advice to lower the hover coupler gains, Westland’s engineers lowered the overall hover coupler gains by some 35% and the result was a satisfactory aircraft stability margin. Hover-coupler failures were also reduced because of the consequent reductions in loadings on their electronic components.
The RAN indicated, through the DNSS, Mr. Jack Lonergan, its gratitude for the services provided to them by SAD/WRE and stated that their immediate problems appeared to have been very satisfactorily resolved.
Our measurements of the output signal produced by the hover-coupler were performed on two hover-couplers, one in the pitch channel and the other in the altitude channel, for each of two Mk31A aircraft. The results showed that the magnetic modulator output signal wave-forms were far from sinusoidal, with a very high degree of harmonic distortion, which varied with the level of the fundamental D.C. voltage.
Any attempt to estimate the gain of such a device would need to take into account the response characteristics of the servo-motor it was driving. The only practical way to determine the effective gain was, first, to measure the gain from the d.c. voltage of the input to the modulator, right across to the autopilot output (the servo-motor output), and, second, to measure the gain of the autopilot response to a pure 400Hz sinusoidal input. Then, by dividing the first gain by the second, an effective hover-coupler gain was obtained.
This appeared to be very nearly constant over the full range of the input signal and similar results were given by measurements taken from both the pitch and altitude channels of the two aircraft tested.
The figure we got was 18.6% less than the one we had earlier derived from the literature made available to us, and confirmed by Louis Newmarks in the UK. The earlier, higher figure is what would have been found if the modulator output had been measured with an RMS reading (hot wire) voltmeter, which is what must have occurred.
This remarkable result was just what I had predicted from my frequency response studies where I had compared the model response with my subjective impressions of stability gained from my familiarisation flight in April 1966. This, together with the successful early diagnosis of the likely cause of the gain error, namely form factor error, was a most satisfying result and one which earned for my modelling team much confidence from the Department of the Navy.
However, on our return to SAD, we found that this correction to the hover coupler modulator gains, though sufficient to stabilise the ‘Plessey type’ model, wasn’t large enough to stabilise our own model fully. Its earlier instability was reduced by the correction, to the point where it was almost exactly neutrally stable. This was still not close enough to the Mk31A, which was mildly stable, with about 10 to 20 degrees of stability phase-margin. So our model was still not sufficiently representative of the behaviour of the Wessex Mk31A.
Several other types of measurement were made during the March visit to Nowra, on almost every other aspect of the hover couplers. We also recorded some cine-film during flight in the cable hover, over Jervis Bay, in various drift conditions and after we introduced various cable disturbances. Two of these films clearly showed enough to permit us to estimate the stability margins of the aircraft in pitch and roll, to within a few degrees. The results varied a little from one Wessex to another, but were generally in the region of between 6 and 10 degrees.
After a full analysis of all the data gathered during our March 1967 trials at Nowra, and after learning of the satisfactory outcome of the gain reduction trials at Yeovil, we decided, for several reasons, to recommend to Navy that further and more extensive trials should be conducted at Nowra.
Our system model was not sufficiently stable yet and it was not safe to assume, just because one serious problem had been discovered and cured, that no others existed. We felt that the proper discharge of the responsibilities we had earlier accepted, required, at least, that the model should be adequately validated and used to perform exploratory, pre-flight, all-weather testing of the proposed Wessex Mk31B/AQS-13 system by computer simulation.
Several of the design settings for the current Mk 31B control system were still far from optimal.
My view was that, once an adequately validated model was available, it should be possible to make further worthwhile improvements in system stability and control and to ensure a smooth transition from cruising flight down to the cable hover state, at 35 feet.
In addition, several service problems had been brought to my attention by operational personnel of the RAN. These were all ideally suited to quick solution by the use of a validated system model. These ranged from accident investigation, investigation of the taping of the leading edges of the main rotor blades to prevent corrosion, and the computation of minimum time courses for navigation between various sonar dunking stations in a range of wind conditions.
In view of the above reasons and others related to the possibility of improving the reliability of the flight control system circuitry, our proposal to conduct further trials at Nowra was supported by DNSS (Mr. Lonergan) and the Director of Aircraft Maintenance and Repair (DAMR) in Navy.
The trials were to be designed and conducted with the aim of gathering any remaining experimental data necessary for the proper validation of the model.
DAMR promised to make an aircraft available to the model team for two weeks in June 1967. He apologised for not being able to provide any further aircraft, explaining that two squadrons were at sea at that time, so that most of his serviceable aircraft were unavailable.
In April 1967 SAD agreed to provide all necessary test-flight instrumentation and recording equipment, to attend Nowra during preparations for, and conduct of, the trials and to give direction to RAN personnel assisting with them.
We had only six weeks in which to plan the trials, specify the details of all the recordings to be made in flight and on the ground, design the data measurement requirements and get all the trials instrumentation ready. Some of this required to be purpose-designed, built and tested in that time.
Ever since the Gliding Club ‘ding’ in early 1964, a small sharp pain in my left side had bothered me from time to time. It wasn’t much at first and I just ignored it for a year or two, but by the end of 1966 it was becoming more annoying.
I was busy with my helicopter study and other work, at the time, so I just put up with it. One evening in January 1967, at the gliding club, I drank one glass of a heavy ale and by the time Pat and I got back home the pain was so bad that I took a pain killer and had to call the doctor the next morning.
It was Dr. Worm, the man who had fixed me up when I had the amoebic enteritis on my return from my 1964 trip to the UK. He sent me to North Adelaide to see a Professor Sir Kerr-Grant, a most eminent gastro-enterologist. The specialist examined me, sent me for a barium meal x-ray and told me that the indigestion I had suffered since I was 21 was due to ‘pyloric spasm’. He taught me how to use breathing to relax properly when my gut was knotted up, and prescribed Buscopan as a muscle relaxant to get me started with the relaxation programme.
Then he told me that he believed I had another complaint altogether and that it was probably related to an abnormality in my left kidney. This was rather impressive, since he was not a urologist and kidneys were not his area of specialisation. He referred me to one of his colleagues, a Mr. Hardison, who would look into it for me.
Mr. Hardison arranged for an IVP x-ray of my kidneys. This showed that I had been born with a very small left kidney and a right one of larger than normal size. It appeared that the pain was due to a malfunction of the left kidney and there was some hope that he might be able to correct it surgically, so I was admitted to St. Andrews Private Hospital in Adelaide and scheduled for two hours in theatre for a catheter exploration of the kidney.
When I came out of the anaesthetic my specialist explained that the interior of the kidney appeared to have been badly damaged by fluid pressure owing to its small size, a condition known as ‘congenital hydro-nephrosis’, and that it was not possible to repair it, so I would need further surgery to have it removed. So I was booked into theatre for the nephrectomy to be done the next day. This time I was in theatre for about 4½ hours. The nursing staff at St. Andrews were excellent and so I received the best of care. The wound healed quickly, leaving a very neatly made, thin scar. However, I was very impatient to get back home to continue my work and I made a nuisance of myself in my efforts to persuade Mr. Hardison to give me his release to go home. He told me that the minimum stay for my type of recuperation was at least two weeks, and usually three or more, but I persevered and, eventually, he let me go home after ten days, but only on my solemn promise to rest at home for another two weeks, not to allow the children to jump on me and under no circumstances to drive a car for at least two weeks more.
What a relief it was to get home! A week or so later I was back at work and I felt fine, as if nothing had happened. The whole episode had been a testimony to the excellent work of the surgeon and the staff of the hospital.
I have never had any sign of after-effects of any kind, from my operation.
By the time I went into hospital we had sold the Vauxhall Cresta and bought our first brand-new car – a Vauxhall Viva. The Viva was a small four-seater saloon and very nippy in city traffic. It was easier for Pat to handle and more economical on fuel and maintenance than the Cresta had been. Also, the Cresta had cost us quite a lot in repairs lately. All the same, I did love that car and I missed its luxury for many months to come.
In April, very soon after my convalescence, we moved into our new house. It still needed lots of hard work to turn it into a comfortable home for us, but it was almost magical, finally to be able to walk through it and to see the results of our planning. It had all worked out rather well and we were very proud of it. For the next year we were both busy laying floor tiles, re-erecting the garage we had brought with us from Tindall Road, putting in our wide front lawn two or three times before it eventually grew properly, and so many other outdoor projects to develop the garden areas.
The house already incorporated a garage under the main roof, with an inside door opening into the front door entrance area, but we expected to get a second car before too long and, anyway, I needed the separate garage for my garden tools and to use as a small workshop.
A month after we had moved in, I attended the academic convocation ceremony at the University of Adelaide to receive a degree of Master of Engineering for my thesis on the ramjet modelling work.
As we settled into our new home we became friendly with our neighbours, Robbie attended primary school in nearby Salisbury and our quality of life improved greatly.
I was now 30 years old and I was conscious of being paid attention by two or three rather attractive young women who worked in the same Labs Area building as I did. I had been married for almost eight years; my seven-year itch was making itself felt, and, although I was still very devoted to Pat, I was beginning to feel that I might have missed a great deal by marrying my first real love at the tender age of only 22. It was the sixties, after all, and ‘the pill’ had long since arrived, heralding in a whole new age of sexual freedom. Most people of around my age were enjoying it all as we were constantly reminded, not only by the TV and the cinema, but by life all around us. I was gradually coming to feel left out and that I was only one woman short of celibate. I should have loved to have affairs with a few of the most attractive young women who were making it very clear that they were interested in me. But I was determined to resist the impulse.
Pat and I discussed this topic briefly now and then and, although she was disarmingly understanding about my feelings, for the time being we came to no clear conclusions.
As soon as I was fit again we went back to our gliding, but only for a few more months. We had too many other things to do.
Dad and Anne came over to visit us for a couple of weeks during the summer. We all enjoyed the visit, although I was suffering more than ever with a severe case of hay-fever, no doubt exacerbated by our new location in an open area, surrounded by hills covered with rye grass and a weed imported by the early settlers and known in Adelaide as ‘Salvation Jane’ or in the eastern states as ‘Patterson’s Curse’. I was eventually driven to my doctor in desperation and injected with steroids which improved matters greatly, but only for a few weeks.
The Completion of the Wessex Project
At least six other groups within WRE had to be brought in to provide specialist experience, high precision measurement and recording equipment and the technical expertise needed to ensure that the complete package would work safely under the extreme conditions of heat and vibration that are normal during helicopter flight.
The list of equipments required for the June 1967 Nowra trials included;-
a power supply conversion unit
a signal-processing unit to frequency-modulate and multiplex 24 channels of D.C. signals
a voice commentary recording facility
a discriminator to allow for post-flight ‘quick-look’ analysis of trials data recordings
two SFIM flight recorders of the galvanometer oscillograph type
and a Tektronics oscilloscope.
Also, the types of signals to be monitored in the aircraft were diverse. Some were D.C., some were modulated on 400 Hz carriers. Some were fully floating and some were relative to aircraft ground and their source impedances were often as high as a few thousand Ohms.
Because of all this, it became necessary to acquire a data-monitoring and pre-processing unit with the following features:-
- Input impedance not less than 0.2 MΏ
- Safety features to normal flight electronics standards
- Capability for at least 17 channels of data
- Capability for input amplification with several selectable levels for each channel
- Capability for input demodulation and phase detection in several channels
- Less than 200Ώ output impedance
- Freedom from vibration sensitivity
- Less than 100 lb weight.
The weight limit was necessary because the other instrumentation equipment already weighed around 400 lb and a full aircrew was to be carried.
In less than five weeks this special unit was designed, developed, built, tested, calibrated and dispatched to Nowra!
It is a tribute to the design staff and to those who assisted them that this unit worked exceptionally well in very severe operational conditions throughout the trials. Technicians were sent to Nowra where all of the equipment was checked out on site and made ready for the trials by the agreed date.
A brief summary of the types of flight and ground trials conducted follows:-
(1) Full-scale stick movement and autopilot travels were recorded in pitch, roll and altitude channels to calibrate recording equipment.
(2) Pitch and roll Doppler radar velocity signals were calibrated by flying over a runway of known length in a measured time.
(3) Altitude recordings were calibrated in flight against the cockpit panel radio-altimeter.
(4) Pitch and roll gyro recordings were calibrated by mounting the gyros on a tilt table.
(5) Pitch, roll and altitude channel autopilots were excited by step and oscillatory inputs from the pilot’s sticks and the barometric altimeter pressure sensor, respectively, on the ground.
(6) In ground tests, temporary sensors were rigged to the output jacks of the pitch, roll and altitude hydraulic servos. Then, with the engine off, these sensors were calibrated against their respective autopilot servomotor outputs and the rotor-blade angles, which were measured by inclinometers strapped to the cuffs of the blades. The inclinometers were removed and then the autopilot servos and hydraulic servos were caused to respond to inputs introduced by moving the various cockpit controls. These trials gave us checks on the responses of the autopilot and the hydraulic servos, to inputs from the pilot’s controls and these were used to compare against the model values.
(7) Trials similar to the latter were conducted in flight, both in the hover and at various forward and rearward flight speeds, in the pitch, roll and altitude channels.
(8) An engine-off landing was tape-recorded.
(9) A vertical descent (in the vortex-ring state) at 3,500 feet per minute, was recorded.
(10) A series of further ground tests was conducted to measure various hover coupler gains.
At this point I can’t resist the temptation to recount a couple of the many incidents that took place during these rapidly prepared trials at Nowra. They tell something of the character of the naval officers I worked with and came to admire so much.
During one of the flight trials, in cable hover, I needed to make the helicopter respond to a sudden violent movement of the cable, first to one side and then forward. The aircraft would be expected to make a sudden strong manoeuvre in response to these cable inputs. In the lateral case it would undoubtedly tip over towards the shifted cable, in order to fly sideways to bring it back to vertical. In the forward case, it would drop its nose rapidly, so as to fly forward and, again, bring the cable back to the vertical.
The question was, how was the cable to be pulled suddenly away from the vertical? It seemed to me that to attempt this over the ocean would be too hazardous, so I suggested to Lt. Cdr. Slug Whitton, the CO of No. 725 Squadron, that perhaps we had better do it over the airfield, with a sailor off to one side, pulling on a good length of rope attached to the cable.
Slug was a really genuine guy with shortish dark curly hair, thoughtful eyes and a gentle nature. He spoke in short staccato bursts that I could barely catch.
He didn’t seem too keen on my plan, no doubt because he was worried about an accident in which the aircraft might crash to the ground. After a few seconds thought, he decided that we should do it at sea! I was taken aback by this idea and a little afraid that someone, or maybe all of us, might finish up keeping the local sharks company. I said so. But Slug assured me it was no problem −
‘All in the day’s work’, as he put it.
So he arranged the flight. I can’t recall who the pilot was − perhaps Peter Campbell, Eddie Bell or Dave Brown. I was in the left-hand seat and Slug was in the rear cabin. We all wore regulation
flying suits, Mae West life-jackets, ‘bone-dome’ safety helmets equipped with headphones and throat mikes.
We took off and flew out over Jervis Bay a mile or two, where we transitioned down to the hover and dropped the cable and sonar. It was winter and a moderate breeze was making a few white caps on the waves. The sea temperature would have been on the low side; not so good for a swim!
Slug spoke on the RT and told us that he was going outside on the winch cable to try to get hold of the sonar cable by using a length of electrical flex he had with him. The idea was to try to flick one end of the flex around the sonar cable and catch it as it came around. He would then use the flex to pull on the sonar cable. On his query, I confirmed that all our instrumentation was switched on and ready to use.
With that, he unhooked himself from the safety rail in the rear cabin, slid back the large rear door, hooked his harness to the thin multi-stranded winch cable, and stepped outside!
I was astounded! There he was, dangling like a rag doll in space, a few feet away from the side of the Wessex, trying to stop his body from rotating around on the winch cable. He looked a bit like an astronaut floating outside his space-craft on a space walk.
The thing that amazed me more than anything was that he was whistling a little tune to himself as he worked, as if he did this sort of thing every day!
‘Fellas! I can’t quite reach the bloody cable’, he reported, meaning, of course, the thick, black, sonar cable, ‘How the Hell am I going to get a hold of it?’
The pilot asked him,
‘Would you like me to rock the aircraft a bit, sir?’
‘Good idea, mate, give it a go!’
As the Wessex began to roll back and forth, Slug would say,
‘A wee bit more… almost got it… OK? Yeah, that’s it, like that.’
By this time the aircraft was rocking from side to side by up to 15 degrees of tilt. Slug kept on whistling, as if he was picking apples from a tree in his back yard.
Finally, he swung himself to and fro and just managed to grab the cable.
‘Are you guys ready? OK, I’ll give it a pull to starboard, hang on.’
Suddenly, the helicopter lurched to starboard about 45 degrees! I caught a glimpse of Slug as he swung outwards. He was grinning, between whistles, of course.
‘How was that? OK? Did you get it all right?’
I assured him that he had done very well and to let the aircraft settle down before he tried to yank the cable forward.
It wasn’t easy for him but, somehow, don’t ask me how he managed it, he eventually got the cable to jerk forward and we were off again on another big-dipper ride.
When all the excitement was over, Slug did a bit of a trapeze act and swung himself back to the door sill where he grabbed a hold and climbed aboard, still whistling his song.
I had seen bravery before but never such nonchalant bravery in such a fearful situation.
I was highly impressed by that and I thanked Slug most warmly for his help. But that was the kind of thing Navy people did, without fuss. What a breed!
Another time, Dave Brown took me and my young electronics graduate, John Riedl, on a flight which was scheduled to perform a ‘vortex-ring state descent’. In this manoeuvre the helicopter is flown to a high altitude and put, as closely as possible, into a perfect hover, that is, with no horizontal motion at all. Then the pilot drops the collective stick to the floor, which turns the blades of the main rotor to an almost horizontal position so that they provide almost no lift. The aircraft then falls vertically, gathering more and more speed downwards as it falls. The air-flow is now forced down through the rotor by the blades, but with so little power that it is forced back up around the tips of the rotor blades by the surrounding air during the descent, and so it forms a ‘doughnut’, or annular, flow pattern with the rotor in the centre. This recycling of the air down, then up around the blade tips and back down through the rotor is a closed-loop flow pattern and is known as the ‘vortex ring state’.
In this situation the helicopter falls very quickly and usually vibrates quite a bit.
Although I had read many text-books and scientific reports from around the world, on helicopter
aerodynamics, and searched the technical libraries, I had been unable to find any evidence of a helicopter being flown through this state while fully equipped with flight instrumentation, and so, as we were all set up for it, it would have seemed a wasted opportunity not to have attempted a vortex ring descent during our trials, even if only for the benefit of posterity. But I was also interested to see whether my model could reproduce the motion of this descent, as a check on its aerodynamics section.
As usual, I was in the left seat of the cockpit, with the pilot in the right seat. John Riedl was in the rear cabin to try to make sure that no harm befell our instrumentation, tape-recorder and the four large car batteries, which were all tied down with rubber ‘bungee’ ropes.
We climbed to 5,000 feet and I asked Dave not to use the controls to take us out of the descent until he judged that it was necessary for safety reasons. He agreed without any sign of concern, almost as if I had asked him to switch on the light.
He made one attempt which failed, as the helicopter soon began to slide forward as it fell, and so out of the descent. This was because we were not precisely at rest when he dropped the stick. So he went back up and tried more carefully to establish a perfect hover. This one was good and we fell straight down.
As we accelerated into the fall, I was watching the altimeter and the rate of descent indicator. The altimeter was winding around anti-clockwise… 5000, 4500, 4000, 3500, 3000 feet. The airfield was coming up to meet us at an alarming rate, my stomach was uneasy and I was only held down by my seat-belt.
Halfway down Dave asked John if he was OK in the back and told him he had better find something to hold on to, adding that it would all be over in a minute or so.
John told us over the RT that he was fine but the batteries were starting to float around.
‘But I’m OK’, he said, ‘I’m holding on to a long, black and yellow striped bar of metal on the door.’
‘My God!’, shouted Dave, ‘That’s the emergency hatch jettison lever! Don’t hang on to that!’
My amusement would have to wait, because the grass was starting to look like it was made of separate blades and I knew from my own flying that this meant we were within fifty feet of the ground! Just as I noticed this, Dave was pushing the cyclic stick forward and lifting the collective to get back our lift and fly us forward out of the descent.
‘Phew!’, I said, ‘That was pretty close, Dave.’
We landed and taxied over to Hangar No. 1, where the power was cut and the rotor began to wind down.
Dave and I were pulling John’s leg about the lever he had been holding.
Later that evening, as we usually did, John and I came back to the hangar after dinner to look over the day’s recordings on the discriminator scope. As I was going over some papers, John suddenly called out,
‘Good God, look at this boss!’
I looked over his shoulder at the screen. He was studying the altitude trace we had recorded during the vortex ring descent.
‘Look at that!’, he exclaimed, pointing to the part where we had levelled out.
The height trace showed that at the lowest point of our pull-out, our wheels had been only five feet above the ground! Considering that we got up to 3,500 feet per minute vertical velocity during our fall, the five feet seemed a bit too close for comfort! Yet, on reflection, I realised that to an expert pilot like David Brown, that too, was all in the day’s work!
When the trials were all over, I was offered a ride in an old Navy DC3 Dakota which was going back to Edinburgh airfield, very close to where I worked at WRE. The ‘Dak’ was one of the greatest ladies of the sky ever to fly and I had been in love with her since I was a little boy, so I accepted gratefully. The Dak’s I had flown in previously had all been fitted out for passenger work and so they had interior panelling and upholstery to dull the roar of their noisy Wright Cyclone radial engines.
However, the Dakotas that belonged to the armed services hardly ever carried such luxuries.
When I climbed on board I was full of anticipation about the flight. As if I wasn’t lucky enough, I was shown to my seat by a delightful young Wran Officer in naval uniform and she sat in the seat on my left and offered me one of the usual services-packed lunches in a white cardboard box. We were just getting acquainted nicely when the skipper started up the engines and, damn it all, we
couldn’t hear a word we were saying to each other!
Nevertheless, she took great care of me all the way back, using signs and gestures to see whether I wanted this or that. All I wanted was some quiet so that I could get to know her. But it wasn’t meant to be!
Back at the lab, the copious stacks of tapes containing all the data from our trials were processed through the highly complex processes that WRE staff were well trained to carry out, and soon, there it was, a huge collection of strip-chart graphs, analogue tapes and digital tapes, all bearing the fruits of our work, converted, calibrated and in the various formats we needed to use them on our computers.
It took months to analyse all of that but we knew pretty well that we were likely to find the more serious errors from our study of the trials involving the autopilot behaviour. We did just that, quickly finding several useful corrections to the model, most of them fairly minor, but one was of primary importance.
The gain of the pitch autopilot’s rate path was about two and a half times as large as what we had been led to believe by the literature supplied by the contractors − the only source of this value we had available to us. Our March trials at Nowra had failed to detect this discrepancy because suitable instruments had not been available to us with which to measure it.
We also found fairly important, but secondary, errors in the proportional gains of both the pitch and roll autopilots.
When all these factors were corrected, our model behaved, in every mode of operation, very much as did the real helicopter. The only validation work remaining was to go through the data more
carefully in order to adjust these gains even more precisely, but this was just to put the final polish on the model. Many other less important features were also adjusted and finally, the model behaviour was so good that even the most experienced pilots could not discern any difference from the behaviour of the real helicopter and were, in fact, amazed to see detail that they thought would be impossible to find in any model, such as a tiny bump that they felt when the aircraft was switched from Doppler hover into cable hover.
This polishing work went on for many months as we worked our way through all the trials results, but no further changes of any note were found to be necessary.
In due course, by mid-1968 the model was fully validated and all the best settings for use in the flight control system of the Mk31B were passed officially to Navy and to Westland Aircraft for implementation.
By early August 1968, No. 725 Squadron at Nowra had taken delivery of the first four Mk31B helicopters. These had been converted by Hawker de Havilland at its Bankstown factory in New South Wales. I believe the two that were set up by Westlands were still in the process of shipment to Australia on board the HMAS Melbourne aircraft carrier.
The acceptance flight-tests at Nowra showed up serious control problems in the cable hover with all four aircraft. They were found to oscillate violently in pitch and roll attitude in a moderate swell.
Angles of up to 15 degrees, plus and minus, in both pitch and roll, were reported by the flight crews. Aware of the substantial expertise we had built up at WRE, Capt. Jim Bailey, Director of Naval Air Policy, telephoned me one afternoon when I was enjoying a barbecue in our back garden
with Pat, Robbie and Sue, to ask for my urgent assistance to sort out this further problem.
The next day I flew to Nowra to look into the matter. I suspected that our official advice on the settings to be applied to the control system, had somehow failed to be implemented, even though they had been embodied in the official Navy Air Publications (RAN)8 for the Wessex Mk31B.
I went up in one of the Mk31B aircraft and confirmed the No. 725 Squadron reports of instability. The gains in the pitch and roll feedback paths were then checked and it was discovered that the cable pick-off gains were set abnormally high, at between 290 and 340 mV per degree, in all four aircraft, instead of the required figure of 230 mV per degree.
I reported that this was the reason for the instability and advised the Nowra authorities to set them back to the 230 figure. This was done and the stability problem disappeared.
During this visit I found several other settings in the flight control system that were also incorrect. In particular, the altitude control system was still misbehaving. It was not possible to investigate this further on such a short visit, so I returned to Nowra between the 16th and 20th of September for this purpose. I soon found that several of the settings in the altitude channel of the hover-coupler were incorrect. Some were well outside specified limits and others, although apparently correctly set up, were very different from the values supplied to SAD by Westlands. Some others could only be measured with specialised equipment which was not at hand in Nowra.
So the altitude control problem became complicated, forcing me back to WRE once more to run a series of simulations to determine the best settings to be used before proceeding further at Nowra.
Arrangements were made for my return to Nowra, taking with me Mr. Bill Dickson, one of our
experienced electronics engineers, to assist me with the many measurements required on the altitude hover-coupler, autopilot and barometric altimeter. The visit lasted from the 29th September until the 4th October. We took the specialised equipment we needed with us.
The main problems proved to be that the gain of the Barometric Altimeter unit was being set too high by some 70% in all aircraft, and that the altitude channel autopilot rate gain was set to half the value indicated by Westlands. The latter was a relatively minor error but the altimeter gain error was likely to have caused the major ‘kangaroo hops’ during descent to the cable hover.
We found a number of other errors, most of which were caused by high vibration levels in the rear fuselage of the Mk31B. This affected the radio altimeter and barometric altimeter readings and was greatly alleviated by remounting the altimeter units in different directions on shock-absorbent padding materials, but it was not the cause of the altitude instability.
Towards the end of the visit we readjusted the various wrongly set gains to the figures we found best, through our model simulations, and sent formal recommendations to DNAP, DAMR, Nowra’s CO and to Hawker de Havilland, to note the new settings requirements.
We tested the four aircraft to find which one was most seriously in error and then we reset all of its parameters to our new values and Lt. Cdr. Dave Brown took me for a test flight over Jervis Bay at noon, to find out whether all the anomalies had been cured.
We flew transitions down from 120 feet and 90 knots airspeed, to the 35 foot cable hover. We repeated these in cross-winds, tail-winds and into wind. Each transition was completely accurate and smooth. Dave was visibly elated by all this.
The morale of the Wessex crews had plummeted over the past year or more, as a result of the seemingly never-ending series of problems. They had friends who were flying Mk31A aircraft at night, and in rough weather, in the hostile environment of Vietnam at the time. One had already lost his life and others expected to be posted up there on active duty before long. That was probably the reason why guys like Dave had become decidedly dejected and heavy-hearted about the Wessex, especially when it wasn’t even stable. There was talk of pilots ‘running up big laundry bills’ by flying the Wessex!
Our test flight was most impressive. The Mk31B we flew showed no signs of any kind of abnormality, even when Dave had put it through all its paces. We landed back at Hangar No. 1 just after 1 p.m., to be met by a large crowd of ratings and officers alike, all anxious to know the results.
As the rotors wound themselves down and the whine of the gas turbine faded away, Dave slid back his window and looked out at the crowd. Someone yelled out,
‘How did it go, sir?’
Dave grinned and yelled back,
‘Mate, it was like goin’ down Bondi on the bloody tram!’
This was what they had all been waiting for and a hubbub of conversation broke out as sailors, who usually stopped work for the week at noon each Friday, shook hands with each other, slapped backs and made whooping noises.
It was Friday 4 October, 1968 and the project was finally complete. I felt something great inside me that I could never forget.
A staff car pulled up at the hangar door and two white-helmeted naval policemen got out and asked to speak with me. I climbed down, removing my bone-dome as I did so, and walked over to them.
‘Sir, the station commander requests your presence at the squadron de-briefing hut. He would like you to tell the senior officers about your work and how you solved the problems’, he told me. ‘Sir, would you like to come with us? We’ll give you and your colleague a lift.’
So Bill Dickson and I walked into the de-briefing hut.
All the senior officers of HMAS Albatross were there, waiting to hear the good news. The station Commanding Officer spoke briefly to welcome us and to express the appreciation of everyone present for the work we had done for them and the success of our team effort. He asked me if I would address the gathering and explain the nature of the problems we had solved and how we had accomplished it.
The room provided a raised platform, a lectern and a large white-board and markers. I rose and thanked the station CO for his kind words, then I explained that the topic was very complex in parts but that I would do my best to keep my remarks as clear and simple as I could.
For about 45 minutes I sketched the control system organisation, identifying various items that had been problematical and explaining, as best I could, how my team and I had managed to diagnose the faults and remedy them by using the model we had spent so much effort to validate.
There were a few questions after my address and I did my best to answer them. There were more kind words of appreciation from the CO and then Lt. Cdr. Les Powell, the Senior Observer of No. 725 Squadron, came up the steps, stood beside me and thanked me on behalf of the squadron. He told me that my name had been entered into the “Squadron Book”, so that I was now a life member of 725. Then, to my dismay, he unpinned the gold wings from his uniform, pinned them to my shirt front and shook my hand, amid applause from the audience.
He announced that we should all retire to the Wardroom (Navy term for Officers’ Mess), where a buffet lunch had been prepared in honour of their WRE visitors − Bill Dickson and me!
Everyone began to wander out through the front doors of the hut and down the steps, to walk the four or five hundred yards to the Wardroom.
As I disentangled myself from others who wanted to say things to us, and went outside, I saw four very tall, young, naval officers standing on the landing just outside the doors, two on each side. Before I knew what hit me, they picked me up bodily, hoisted me on to their shoulders and ‘chaired’ me all the way to the Wardroom, even marching directly across the hallowed and forbidden ground of the station parade-ground! I protested but it was no use! I had to sit there like Guy Fawkes and bear the embarrassment of it. I’m sure my face must have been a delicate shade of beetroot. Later on, when I had regained my equanimity a little, I realised what a great honour this had been, and that was another deep bond I had with the Navy. All the same, although the work we had done was exciting and, sometimes, quite challenging, I still thought they had over-egged the pudding a bit to consider me deserving of such a demonstration of affection.
The ‘buffet lunch’ was a banquet fit for royalty. It was set out on a row of connected tables covered with pure white linen and was some twenty-five feet in length. There was every kind of celebration food there: whole salmon, roast suckling pig, complete with the apple; a side of roast beef; huge pyramids of king prawns; Chinese dishes; and goodness knows what else. The bar was open and there was champagne, a variety of excellent wines, beer and fruit juices. Then the desserts arrived and we had a similar array of gateaux, pastries, cherries jubilee, crêpes, pavlovas and more that I can’t recall.
There were toasts, speeches and abundant good humour in the true Aussie style. All this on their afternoon off, just to show their appreciation!
This was the most satisfying project I had been involved in, so far in my tender young career, and I shall never forget it.