“Try not to crash…”
The engineer looked at me and smiled. “Try not to crash”, was all he said as I let the brakes off and the heavily laden B767 started to roll forward under the application of power. As I lined the aircraft up on the centreline, of runway 03 Left I knew this was going to be a difficult takeoff. Johannesburg is 5600 feet above sea level, where the air is much thinner and therefore takeoff performance is more limiting.
Add that to the fact that we were close to the maximum takeoff weight of 186 tonnes and the outside air temperature gauge was reading 40 degrees Celsius. Oh and I nearly forgot, we were expecting Windshear on departure. On the face of it, the engineer’s words seemed like good advice.
Windshear is one of nature’s little tricks which can ruin your whole day when you fly aeroplanes for a living. The effects of rapidly shifting wind speed and direction during takeoff or landing can produce large and sudden deviations in airspeed that are difficult to counteract.
Quite often associated with adverse weather systems like thunderstorms, these shifts in wind speed are hard to predict as they are invisible until you fly into them. Unfortunately there is much reliance upon PIREPS (pilot reports) and these are not necessarily authentic indicators of real Windshear conditions. One man’s Windshear is another man’s turbulence.
I recall many years ago when flying a light, propeller driven aircraft into an airfield that the flying conditions on final approach were certainly sporty, however no worse than moderately turbulent. Looking at the windsock, it was not difficult to see why, as it was in agreement with the Met man’s prediction of a strong and gusty wind. While taxiing in to the apron, I was amused to hear the pilot who was now on final approach transmitting to the tower, “Tower, this is XXX, be advised there is VERY SEVERE WINDSHEAR on finals!” His voice had a certain breathless quality to it and he had obviously just given himself a big fright, but his PIREP was a little over the top. In fact there are only two types of Windshear to be reported, either moderate or severe. There is nothing worse than “severe” – so VERY is not an option.
As the 767 gathered speed, I noted that the acceleration was slow, even though full power was applied and the significant speed of 80 knots seemed to take ages to appear. At this rate, it was going to take a week to get to rotate speed. Due to the heavyweight takeoff, the Vr was pretty huge at 160 knots and our takeoff roll was going to require most of the runway to get airborne. The call of “Vee One” came and went. In my own thoughts I said to myself, there’s no going back now… we were committed to fly. The thrust levers were hard up against the throttle stops and the N1 (power) gauges of both engines were showing maximum.
I could see the end of the runway approaching and thought, this is going to be close, then I heard the call…“ROTATE!”
I had already started to increase the back pressure on the control column and now it felt REALLY heavy. I could sense the nosegear unstick and see the pitch attitude increasing — the end of the paved surface was really close now.
The call, “Positive Climb”, came when we were only 20 feet off the ground with both the Radio Altimeter and the VSI showing a climb.
“Gear Up!” I replied through tightly pursed lips and then I saw the airspeed start to decay. The synthetic voice started calling “WINDSHEAR! WINDSHEAR!” and the red warning captions displayed on the attitude indicators. I noted that we had barely made 150 feet on the radalt when the Windshear warning started as the airspeed dropped and dropped…
I held the attitude close to the Pitch Limit Indicators (PLIs) and hoped for the best. Brief stickshaker warnings showed we were very close to the stall, but now the radalt started decreasing and outside the flightdeck windows I could see the ground getting awfully close.
The pressure from my right arm forcing the thrust levers forward increased, but the engines were already giving their all. The GPWS warnings added their voice to the proceedings with an American accent, “DON’T SINK… DON’T SINK!” Again, good advice I mused while scanning the radalt, airspeed and VSI all at once. ‘38 feet’ was the lowest number I saw on the radio altimeter before we finally began to climb again and the airspeed started to behave itself. Eventually we were accelerating and passing 500 feet on the radalt – sheer luxury! Soon we could start retracting the flaps. Phew!
Only THIRTY EIGHT FEET! It was time to make a decision.“Let’s go back and have another go — that was too close to call it a success”.
I had made my mind up and the engineer working the simulator instructor panel pressed the motion freeze button. Of course that’s the beauty of the “Sim”, it allows us to live and fight another day when in the real case we might be toast. You could be forgiven for thinking that we were ‘playing’ here, but there was a real reason for our presence in the simulator. I had been asked to come and help the engineers calibrate the windshear settings for the machine as in the recent CAA annual approval test-flight they had been pronounced as too extreme and in some cases ‘unsurvivable’. This came as no surprise to me as many of the scenarios installed in the programme of the simulator are based on real accidents where the aircraft and all on board were lost in the accident which followed. They were denoted Dallas, Tokyo, Philadelphia etc.
In my discussions with the engineers, they told me that the Training Captains of old, made sure there was little chance of the crews surviving the simulated windshear by using the 100% option on the selection panel. Apparently their reasoning here was that the crews would be scared of going anywhere near windshear situations and therefore they would fly safer. In the modern way of training professional pilots this is known as ‘negative training’ and is definitely at odds with current thinking, hence the CAA finding fault with a machine which emulates unsurvivable scenarios. The philosophy now runs with the principle of allowing crews to fly into a windshear event and then by using the correct flying techniques to keep the shiny side up, fly safely away from the ground again. In the simulated takeoff from Jo’burg, we had survived, but only just and we needed to have a little more of a comfort factor here. To prove it, I flew the departure twice more, using the recommended technique and the aircraft collided with the ground on both occasions – just about in the same position where I had missed it by 38 feet on the first one.
By a clever tweak in the software, it was possible to experience windshear on takeoff, but survive. Don’t get me wrong here, the dramatic effects of the ‘shear close to the ground were still there, but by rigid adherence to the recommendations of the manufacturer in the Flight Crew Training Manual we had climbed away safely. You would still not describe this as ‘a walk in the park’, as some of the pitch attitudes required feel and look quite extreme, but Mr Boeing as always is there to help us with the little yellow (amber) PLIs on the attitude indicators.
The aim is to select an attitude where the small black wingbars of the aircraft, sit on the bottom of the yellow eyebrows and despite some transient stickshaker indications with full power engaged, this will give you the best rate of climb. The technique benefits from practice of course, because normally when we pilots are alerted by the ‘shaker, our response is to push forward out of the aerodynamic stall – at such low altitudes this is not an option… The houses get awfully big, awfully quickly.
It is amazing how time passes when you are having fun and soon four hours had been consumed while we explored all of the listed windshear events on the instructor screen. Some of them, we deleted as they were of nil training value, for example when they produced such a minor airspeed excursion, that there was nothing to confirm a windshear was present. There were a few which were toned down in severity and all were checked under the worst possible conditions. For example during the approaches, we made certain the aircraft was at or close to maximum landing weight with high ambient temperature and a high elevation airfield. If all the foregoing proves nothing else, it shows that the authorities are working in the right way to improve training facilities and techniques to enable airline crew to benefit from the experience of flying the simulator every six months during their recurrent checks in a modern, progressive environment.
It is not often that we get time to meet and work with the simulator engineers and I was pleased to be able to take part in some really interesting flying exercises which stretched my poling abilities beyond the norm for some time. In the real world there have been a few occasions when we have delayed our departure until the thunderstorm which has been hovering in the overhead of the airfield has moved away. The recent simulator experience I had will not make me any keener to get airborne in such difficult weather conditions.
After all as the old saying goes, “it is always better to be down here wishing you were up there… than the other way round!”
© James McBride
