Trials and Errors

by Mike Brooke

  ‘The other number three engine,’ said Terry Colgan, with not a little exasperation.

  ‘Oh, yes. That one is going round OK,’ responded our embarrassed fighter jock!

  On board the Argosy there were all sorts of new toys to play with, like a nose wheel steering tiller to manoeuvre the machine on the ground. From where I was sitting, 20ft up, there was a very good view ahead out of the window and ground handling was quite easy, although I had to learn to be aware that the wings stuck out a long way each side. Take-off was a joint effort between the occupants of the pilots’ seats. Steering was initially done by the left seat occupant and power applied by the right-hand man, who also restrained the control yoke. At a predetermined point the ‘captain’ took full control of everything. I had to learn new things to listen to and call, such as the various key speeds on take-off, like ‘V1’, ‘Rotate’ and ‘V2’ – it was all very ‘Speedbird’ and ‘Captain Speaking’ stuff! Once up and away we made stately progress above Wiltshire. The manually operated flying controls were, as expected, fairly heavy, but not overly so; but I had a definite feeling that the final connection to the actual control surfaces was made of rubber – the controls lacked the solidity I was used to. Vic Lockwood came back from his first sortie in the Whistling Wheelbarrow and likened it to driving a London bus from the top deck, but attached to the steering wheel by elasticated bungees.

  The most important things we had to experience and learn to do was to briefly explore the stalling characteristics, which were reasonably benign, but with lots of shaking, rattling and a bit of rolling, and flying with three or two engines operating. After my long experience on the Canberra I found that the three-engined flying was pretty much a non-event. However, once two engines on the same side were throttled back, the handling, speeds and control forces were reminiscent of the Canberra. The most challenging item to conquer was a two-engined go-around from about 500ft on an approach to land. It was difficult but my past experience of flying and teaching that sort of thing for several years helped me out. Then there was the landing. I was supposed to call out power settings in pounds of torque to the engineer who would set the requested number using the throttles. However, I did observe that when any of us made a gross error the correct number would mysteriously appear on the gauges. With the landing gear and full flap down the correct call as the aircraft floated over the end of the runway was ‘Slow Cut’. Then it was a case of fighting the tendency of the aircraft to want to land on its nose wheel with lots of aft control yoke, but to not overdo it and flop out of the sky from a great height. The poor old Argosy took a lot of punishment in this phase of the course. But it was very satisfying to fly a large aircraft for once – as long as I didn’t have to do it for a living!

  Although it didn’t happen until April, there was just one other conversion to type to complete the ‘Full House’ of ETPS Fixed Wing aircraft types in my portfolio. And what a way to finish: the English Electric Lightning. Finally the day arrived when my name was on the daily flying programme against Lightning T4 XL 629. Three of us were down to fly it and the plan was that our tutor would stay in the cockpit while the jet was refuelled and we would make the long walk all the way down to the far end of Boscombe Down’s huge concrete apron to where the Lightning was parked. I set off as soon as we knew that the aircraft was down and still serviceable from the previous sortie.

  By the time I reached it, the refuelling truck was pulling away. While paperwork was being raised and signed I walked around the tall, sleek, red and silver jet. The heat haze was still emanating from the two vertically mounted jet exhaust pipes at the flat rear end, beneath the fin and rudder that towered 20ft above me. I then walked under the wing to marvel at the left undercarriage leg. It was spindly to look at and the wheel and tyre on the end of it looked far too narrow. That was because the landing gear retracted outwards into the 60° swept wing, which was as thin as the structural engineers would allow. The way that the wheel and leg twisted back into the wing was all down to the angle of the bearing on which it was suspended. The normal pressure in the tyre was around 300 psi; I thought that they might just as well have made it out of solid rubber. Our tame Lightning drivers, Vic Lockwood and George Ellis, had regaled us with lots of stories about this potent Cold War fighting machine, one of which was that the explosion from a Lightning tyre bursting on landing, apparently not an infrequent occurrence, could be heard all over the county! The wear on these tyres is so much that they are changed after ten landings; that is if they’ve lasted that long. Hence we would not be making touch and go practice landings!

  Soon I was at the foot of the long ladder on the left-hand side of the nose. The jet was ready to go, but I was beginning to wonder whether I was. As I climbed up to the cockpit I thought, You’re about to overreach yourself now, lad. You won’t keep up with this one. Graham was sitting there beaming at me; I just hoped that he had more confidence in me than I did. I checked the ejection seat, sat down, strapped in and put my helmet on. No going back now! After carefully going through the pre-start checks I indicated that I was about to start the No. 1 Engine. At that point I couldn’t remember whether the No. 1 was the one on the top or the bottom of the fuselage behind and below me. I then decided that it didn’t really matter, as long as I knew which of the shiny levers and switches to use. The engines were 300 Series Rolls-Royce Avons and were started, like the Hunter F6 and the Canberra PR9, with the ‘rocket fuel’ more correctly known as AVPIN. That meant that when I pushed the engine start button there should be a ‘Wheeee’ and then a ‘Phut’. If it came the other way round we were in trouble!

  A few minutes later both the engines were running, the flaps and airbrake operations checked and we were ready to go. Once cleared, we moved off, trying to use as little thrust as possible. In fact, once under way, the machine was like a thoroughbred hacking down the racecourse to the starting gate; it definitely wanted to go flying. Then it was onto the runway, brakes on and run the engines up to 85 per cent power. Cleared to go, brakes off and open the throttles to the stop, check rpms at 100 per cent, Jet Pipe Temperatures (JPTs) in limits and no warnings. We were already accelerating like a Ferrari but now I had to apply the reheat to make this rocket sled go even faster. Rock the throttles outboard, towards the cockpit wall and then push them even further forward. Then something odd happened. It was like we had started to slow down. This was during the short pause while the jet exhaust nozzles at the back end opened, which reduced the thrust, and the extra neat fuel injected into the jet pipe was ignited, which then increased the thrust even more. No sooner had this deceleration feeling registered than it was replaced with a powerful shove in the back. Now we were really motoring. I watched the airspeed indicator and as it reached 135kt I eased the stick back and waited. Soon afterwards the nose came up and we parted company with terra firma. I checked forward slightly with the stick, briefly applied the brakes and reached out for the button that raised the undercarriage.

  Now came a crucial bit. The Lightning’s hydraulic system couldn’t raise all the wheels at once so they were sequenced. The two main legs retracted first and then, when they were up and stowed away, the nose wheel leg went up. However, it retracted forwards into its bay underneath the air intake, right below where we were sitting. If I let the airspeed get above 240kt before it had retracted it would stay down, held there by the air pressure overcoming the hydraulic pressure. The best thing to do in this case was to raise the nose to an almost vertical attitude and let the speed reduce. This wasn’t a very pretty sight from the ground and was a very public display that you’d got it wrong. But today, on my first ever take-off in control of a supersonic interceptor, there was a satisfying thump from down below as the speed was passing 230kt. All the undercarriage lights were out and we were on our way. At 430kt, which turned up very quickly, I raised the nose to about 60° above the horizon to hold 450kt, until the Mach meter showed 0.9 (90 per cent of the speed of sound). The machine was climbing at about 20,000ft per minute! It
felt like I was lying on my back. I was supposed to level off at 36,000ft and not go supersonic. Graham had given me the hint to start the level off at about 30,000ft and by the time I had pushed the nose down and reduced power we should be at or near the desired altitude. Phew! And it’s less than two minutes since I let the brakes off! I thought.

  After a bit of handling up here we descended to 15,000ft and did some more turns, rolls and a loop, which took up a huge amount of sky. The aircraft was a joy to handle and I found it relatively easy to make it do what I wanted; maybe it won’t be so hard after all? There was plenty of buffet to warn me when the wing was getting close to its limits and after trying some slow flight with the landing gear and flaps down it was time to go home and try to land the beast. The Lightning has many good features, but neither range nor endurance is on the list. Fuel will only fit in the thin wings or the streamlined bulge underneath, known as the ventral tank. The total amount of fuel was 700 gallons and this even included 33 gallons in the tiny flaps!

  Once we got back to the visual circuit at Boscombe Down, my initial anxieties returned. The Lightning had, so far, been a bit like a big Hawker Hunter, but landing it would be quite different. I would only be making one touchdown, there would be no practice landings, as we did in all the other aircraft, so we would just make low overshoots. And we only had enough fuel for three of those! I knew that it was crucial that I didn’t do something that had become natural to me over thirteen years of flying; that was to throttle back before the main wheels were on the runway. Otherwise the big jet could drop out of the sky and its tail-end strike the runway. So I set off downwind, with the undercarriage down, reducing speed to about 190kt. At the turn-in point I opened the airbrakes to increase the drag and dropped the flaps. There was plenty of buffet now and the most important thing to do was to not let the speed fall too low. Once lined up with the runway, at about 300ft, the minimum speed should be 165kt, slowly reducing to 155kt over the touchdown point.

  As I flew the three practice approaches I became more and more astonished by how easy things were. The speed and angle of approach could be easily controlled with small movement of the stick and just one of the throttles. But now it was time to land. As I came over the beginning of the runway, known as the threshold, the speed was right and I just held the attitude and then the main wheels touched the runway. I simultaneously lowered the nose and throttled back. Holding the nose wheel firmly on the ground I pulled the handle that steamed the brake parachute. The control tower confirmed that it had deployed and then I started braking, gently at first. We turned off the runway after about 7,000ft of landing run. So I had flown the Lightning – a small step for a fighter pilot, a giant leap for me!

  On my second sortie I would have to fly supersonic, then make single-engined approaches, flapless approaches and approaches with the artificial control feel system turned off. We would be doing our test flying exercises in the supersonic regime so I’ll describe that later. The other various practice failure cases were, as far as I could tell, almost non-events; this aircraft really was a credit to Teddy Petter who had designed it, test pilot Roly Beamont and the English Electric team who had helped to perfect it. To my mind Petter’s genius in designing both the Canberra and the Lightning puts him alongside the greats of aircraft design such as Mitchell, Camm and Handley Page. I was very satisfied that I hadn’t, after all, overreached myself; well not yet!

  4 SO MUCH TO LEARN

  Day by day, as the spring started to dress the trees around our house and along the roadsides of my morning walk down to the Ground School, things academic and practical were getting harder. The staff were conspiring to fill us with such a huge quantity of new knowledge that there was a danger that we would have no little grey cells left to absorb it. However, that did not apply evenly across the course. There were those among us who had university educations in related subjects and brains the size of planets. One even had a Master’s degree in aeronautical engineering. These special people were rapidly becoming more and more popular, as those of us who spent an increasing number of classroom hours in a baffled state pumped them for simpler explanations than we were being fed by Chalky et al. What was a Fourier transform and what was it for? How did a Laplace transform really work? How do you conceptualise non-dimensional time?

  On top of all that brain-burning stuff we were ploughing through the test-flying syllabus. The first such exercise for me was stalling in the Jet Provost. There were four sorties in which to explore all the possible stalls that one could do in a trainer. We then had to report, in cogent English and a prescribed sequence, what we had observed, how it matched the specified requirements and our recommendations as to the suitability of the aircraft for service in its stated role. We were also encouraged to report on all unsatisfactory items that we found, and argue sensibly as to why they might need corrective action.

  The JP did not have any automatic recording equipment so everything would have to be quantified using the normal flight instruments, a stopwatch, a hand-held force measuring gauge and a tape measure. Neil Sellers was my Flight Test Observer (FTO) and he grappled with the tape measure to measure how much the stick was moving. It worked well until we were doing the stalls while turning hard and then the tape kept bending under the increased force of gravity or G. Eventually Neil brought a lump of Blu-Tack and stuck it to the instrument panel to stick the end of the tape to. Talk about the cutting edge of white-hot technology! The big surprise at the end of the exercise was that the JP failed to meet the requirement for the margin of stall warning laid down in the regulations. Yet it had spent almost twenty years successfully training pilots.

  By the time we had finished those flights and started writing the report I was flying the next test exercise, something called PECs. The acronym stands for Pressure Error Corrections. Air-sensing instruments, the altimeter and airspeed indicator, rely on accurate measurement of the atmospheric pressure the aircraft is flying through. This is done with a sensor or sensors positioned somewhere on the aircraft. However, wherever the sensors are positioned they never give perfect results because the aeroplane itself can induce errors by its very presence. These errors usually vary with speed and configuration, whether or not the flaps and undercarriage are up or down. The way that we had to quantify these errors turned out to be rather good fun and took the form of a legal, low flying competition. Our syndicate was allocated the Basset. What we had to do was fly down the runway at different speeds and in different configurations and measure our height very accurately with a special altimeter fed from the static pressure sensor on the aircraft; the same one as fed the instruments.

  On the top of the main HQ building, which overlooked the airfield, was a small observation post from which the FTE would take photographs of each flypast and note down each run number as per our previously agreed test plan. He also had a similar special altimeter. Later the readings and photographs were compared with the aircraft’s sensitive altimeter readings and the errors then calculated. Some guys had the Hunter, lucky devils, and others the Jet Provost. The low flying element was restricted by one factor: something called ‘Ground Effect’. This was not, as one wag had it, what caused the wheels to go round on landing. It was the influence of the slightly higher pressure caused by the air getting squashed between the aeroplane and the ground if it was flown too low; this would then cause a pressure error of its own. As a rule of thumb if you flew higher than half the wingspan the effect would be negligible. However, I did spot a couple of guys determined to ignore that!

  In the classroom we were starting to master the concept of stability derivatives. They were represented by a whole collection of Greek letters mixed up with normal characters that were shorthand for certain features of an aircraft’s stability and control characteristics. At the time we used the British system of axis, moment and derivative designators and we soon picked up this new lingo. No longer would we spend Happy Hours just shooting down our wristwatches with our hands when describing the week’s
flying events. Now we would start talking about Nv and Lv and Tsinθ; but not for long. After a couple of beers, it would soon get back to shooting down wristwatches again!

  The next challenge to our test flying abilities was to be a longitudinal static stability exercise, which our syndicate was to fly in the mighty Argosy. There would be three trips: that was one each for George Ellis, Gerard Le Breton and me. Each would be with the aircraft’s centre of gravity (CG) in a different position: forward, mid and aft. The two extremes were achieved by lots of bags of lead ballast being strategically positioned in the cargo bay. George won first prize, having to fly the big beast with the CG at the forward limit, I got the aft CG trip and Gerard the mid. The Argosy had a full test instrumentation pack, so there would be lots of automatic measurements of things like airspeed, elevator angles and trim positions. Of course we had to prepare our test plans, the many test cards for each condition and then go off and fly. We pilots acted as co-pilots for each other, Neil Sellers was along as the observer and one of the engineers was there to make sure that we didn’t do anything too naughty to his precious ‘Whistling Wheelbarrow’.

  The only memory I now have of this exercise was when I was flying co-pilot for our French fighter pilot, Gerard. We were getting progressively late for our planned return in order for the next crew to take over. I was trying hard to persuade Gerard to forget his Gallic pride and set off home, even if he hadn’t got all his planned test-points completed. Eventually he relented and we set off back to base.