Newsletter 11
Winter 2005
Updated on 18Nov2005
Published by the Hawker Association
for the Members.
Contents © Hawker Association

Agenda for Aerospace
Duxford Visit
Harrier First Delivery
Hawker People News
Heritage Memorial Project
HMS Invincible Retires
Last Pegasus
Programme 2005-6
Sopwith Stories
Tangmere Hawker Weekend
Unified Flight Control
John Farley explains the contemporary significance of the RAE/DERA/QinetiQ's work on their VAAC Harrier TMk2 XW175 and the historical background to this success...

On the 16th of May 2005 Justin Paines, a QinetiQ civilian test pilot, pressed the 'coffee bar button' and thereafter everything happened exactly as intended and just like I had wanted it to for years. The 'coffee bar button' was in the rear cockpit of Harrier XW175 (the second two-seater ever to fly, way back in 1969) and the result of Justin pressing it was that 175 looked around, sniffed the air with its satellite navigation system, decided where Justin's coffee bar was located, took him to it and landed him safely, gently and of course vertically, on board HMS Invincible.
Control System
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This first fully automatic recovery of a Harrier to a ship was the end of a journey on which RAE scientists embarked in 1952. Yes, that is correct. The journey started eight years before Bill Bedford broke his ankle and the doctors decided the only thing he was then fit to 'fly' was the first prototype P1127 tethered to the grid at Dunsfold. Just what were RAE (later to become DERA and now QinetiQ) scientists up to all that time ago that eventually led to the Invincible landing fifty three years later?  Also why was I so keen for such a capability to be developed? I will try to  explain.

By 1951 the senior management of RAE realised that the thrust of jet engines was increasing all the time and that one day an aircraft with a thrust greater than its weight would become possible. But how could the attitude of such an aircraft be controlled in the hover?

In an attempt to answer this question Dennis  Higton, a former RAE apprentice who had joined the Aerodynamics Research Flight at Farnborough at the  end of his apprenticeship in 1942, devised a rig to investigate the feasibility of controlling the attitude of a hovering aeroplane by means of small jets mounted in the nose, tail and wingtips. The layout he used is shown in RAE Tech Memo 286  of April 1952 in which Higton reported his work.

These early experiments showed that a reaction control system was indeed suitable and enabled Higton, working with colleague Roger Duddy, to draw up the specification for a full size piloted rig to be used by the RAE. This rig, which first hovered tethered under a safety gantry at Rolls-Royce Hucknall in 1953,flew free for the first time in 1954 and was known as the Flying Bedstead. From those early days the scientists of the Aerodynamics Research Flight at RAE - or simply Aero Flight as they were known - worked continuously to develop and improve the handling qualities of jet lift aircraft. After the Flying Bedstead they commissioned the Short SC1 which they operated from the new RAE research airfield at Thurleigh, near Bedford.

From the start the RAE approach to the control of jet VSTOL aircraft was to use a high degree of autostabilisation to make the handling as easy as possible for the pilot. Hawkers on the other hand favoured simplicity as a means of reducing the control system failure cases. Accordingly the initial Hawker P1127, Kestrel and Harrier aircraft could be flown without artificial aids, relying on the pilot to compensate for any inherent handling deficiencies.

With hindsight both teams were correct. The RAE approach was without doubt the ideal way ahead for the pilot but - and it was a big but - the electro-mechanical engineering reliability of automatics in those days was far from assured given the technology then available. Because of this, the Hawker approach of simplicity and reliance on the pilot to compensate was absolutely correct during the 1960s and enabled the Harrier to happen.

Once the Harrier went into service, there was a slow but continuous trend to add devices to it that made control easier and safer for the pilot at low speeds. Not surprisingly the RAE Aero Flight input into the development and certification of these aids was considerable and from 1964 onwards they were helped in this work by having their own P1127. By 1964  six P1127 aircraft had been flown at Dunsfold and naturally the later aircraft incorporated lessons learned from the earlier ones. Because of this the standard of the original prototype, XP831, was by then looking fairly unrepresentative so the ministry allocated it to Aero Flight at Bedford. At that time I happened to be serving there as an RAF Flight Lieutenant and was fortunate enough to be given the job of collecting it from Dunsfold. Three years later, following the retirement of Bill Bedford, my luck continued and I took my uniform off and joined Dunsfold as their new junior test pilot.

Later in 1970 Dunsfold Chief Test Pilot, Hugh Merewether, asked me to represent him at a meeting being held at RAE Farnborough. Hugh explained that it appeared the RAE boffins had ideas for making life easier for jet VSTOL pilots and so he needed somebody to go and keep tabs on them. He pointed out that as a former RAE apprentice I was obviously the bloke for the job and anyway he had better things to do that afternoon. At that meeting it was clear to me that the eventual aim of the scientists was to hand over control of the aircraft to a computer leaving the pilot just to tell that computer what manoeuvre he wanted it to fly. If this happened it would mean the Harrier pilot's nozzle lever would no longer be needed because control of the nozzle angle – as well as everything else that the pilot hitherto controlled – would be left to the computer.

As I drove back to Dunsfold I was quite excited about what I had heard. After using my left hand to operate the nozzle lever and throttle for six years, it was clear to me that it was only a matter of time before I made a mistake and moved the wrong one with potentially disastrous results. Therefore I welcomed the boffins' ideas although I realised it might take a few years to turn them into reality (it actually took twenty nine!). Meanwhile the RAF had only two years experience with their Harriers and the provision of this single nozzle lever was seen as the simple masterpiece that had enabled VSTOL to happen. Rather naturally at Kingston and Dunsfold, any talk of removing the nozzle lever was as close to Harrier Heresy as you could get so care was needed when broaching the subject. Anyhow they were all so busy coping with the USMC decision to buy Harriers it was not reasonable to expect them to give serious consideration to futuristic ideas.

Time passed and I became increasingly frustrated that the RAE approach to specifying the modifica- tions of a Harrier to start flight trials had turned out to be so conservative in that they were not intending to split the control of the four engine nozzles. I remember talking to Kingston aerodynamicist Robin Balmer about this in the mid seventies and suggesting that if we let a computer put the nozzles down on one side only, we could get rates of roll in low speed combat that would make any opposition's eyes water. Equally by putting down the front or rear pair we could pitch in a way nobody else could even dream about. It seemed so obvious to me that the Pegasus offered a ready made way to endow the aircraft with unmatchable manoeuvrability. However, such ideas were viewed as too way out. Not surprisingly the Kingston design office and spiritual home of "Keep it simple, stupid" (and that is meant as a compliment not as a criticism) was not about to change horses in mid stream and take the lead in the brave new world of computer-based systems or fly-by-wire as they are called today.

My apologies - I digress. By 1982 the RAE programme, now called VAAC for Vectored thrust Aircraft Advanced flight Control, had laid the three key foundation stones needed for eventual success.

The first of these was the choice of a two-seat aircraft for the programme. Had the team chosen to modify a single seat Harrier, they would only have been able to test tomorrow's ideas on today's Harrier pilots - hardly the best way to conduct open minded research. (NASA went this route with a modified Harrier and I suspect lived to regret their decision).

The second was installing something termed the Independent Monitor (IM). The IM was essentially a special computer that was carried around in the test aircraft for many sorties during which time it was taught by the Harrier crew to recognise the safe limits of Harrier operation. It was then sealed and became the basis for the subsequent airworthiness certification of the aircraft as a research tool. When the trials proper started, the IM was thus able to keep an unblinking eye on what the (single channel) experimental equipment was attempting to do with the various Harrier controls. If it detected anything that looked like going outside what the human pilots had previously agreed was a limit, it instantly disengaged the experimental kit and handed the aircraft back to the safety pilot in the front seat. That way the safety pilot would always be left with a recoverable situation.

The third foundation stone was that by then two Bedford men, scientist Peter Nicholas and test pilot Flight Lieutenant Peter Bennett, had conceived the notion of something called Unified. To cut a long story short, this meant that if the pilot wanted the aircraft to go up then the stick had to be pulled back and to go down the stick was pushed forward. Sound familiar? Well yes, but Unified was conceived for use at any speed.  Helicopter pilots raise or lower a lever called 'the collective' to go up or down in the hover while Harrier pilots use the engine throttle for the same thing. The aim of Unified was to allow the pilot to fly using the stick at any speed. You may prefer to think of it as eliminating the concept of a 'stalling speed'. When the pilot asked to fly slower than the stalling speed, the computer merely put the nozzles down and used the engine instead of the wings to support the weight. This of course was what human (superhuman?) Harrier pilots already did but only after special and expensive training. Unified enabled any fixed wing pilot to handle a Harrier in the circuit without extra training. Easy though Unified may appear, it was in actual fact far from straightforward to optimise and approve all the necessary software. After all, exactly how did various pilots want the aircraft to react to their demands at different speeds and so on?

In 1983 I turned into a pumpkin and retired from Harrier test flying but the VAAC team were kind enough to keep in touch with me and I was invited back in 1993 and again in 1999 to fly the aircraft and comment on how I thought they were getting on. In 1999 my safety pilot was one Squadron Leader Justin Paines. When I got out after our couple of sorties at Boscombe, I told him that I thought the team had cracked it and that Unified was the way ahead. Shortly after that, following a detailed and quantitative evaluation trial where the VAAC was flown by many test pilots including several from the USA (some of whom had never been in a Harrier before) the VAAC team was able to convince the US Joint Strike Fighter Programme Office that their ideas were indeed the way ahead.

Again there was much more to selling Unified to the US than my account might suggest. Justin Paines, who led the final test pilot push, was in no doubt that the opinion of Harrier squadron pilots on both sides of the Atlantic was bitterly divided. While some saw the attraction of Unified others were seriously opposed to it. The opposition even included senior BAE test pilots. As I saw it the opponents all had many years of successfully using the nozzle lever and arguably it was that skill that made them better pilots than those who had no such experience. It made them better in the circuit, better in the bar, and probably better in bed. As for the mistakes Harrier pilots had made over the years it was only lesser mortals, not people like them, who moved the wrong lever. Expecting such senior operators to vote for abolishing the nozzle lever was akin to expecting turkeys to vote for Christmas.

In the end I am glad to say that the VAAC team's arguments in favour of deskilling the process of flying jet VSTOL won the day, thus saving costly training as well as reducing the likelihood of accidents. The JSF will be in service for 50 years from now so many of its future pilots have yet to be conceived. Thankfully the aircraft is to be built with them in mind, not yesterday's nozzle lever men.

Finally what about my wish for a 'coffee bar button'?  In many of the conversations I had with Harrier pilots about the controversial idea of Unified, I was at pains to point out that although I wanted to get rid of their beloved nozzle lever I was not a boffin's nark and against the operational pilot's point of view. In fact quite the reverse. I believed that while operational pilots were over the target (and being shot at on our behalf) their views about what they needed to do their job were paramount. However, once they turned their back on the target and their operational job was done, they should be able to press a 'coffee bar' button whereupon the aeroplane would then take them home safely, day or night, in any weather, regardless of whether they were exhausted, injured or (heaven forbid) it was just their day to make a mistake during their approach to land.