Friday, 15 November 2013

Upset recovery training

Flying "under the hood"
I've just returned from progress test four*, our last exam in a single engine aeroplane. The whole test is "under the hood" meaning I could see only the instruments and not outside. After performing various basic manoeuvres, stalls and slow flight the instructor simulated a vacuum pump failure by covering up the artificial horizon and heading indicators with scraps of paper.

Using this limited panel of instruments, I demonstrated timed turns, which are done by flying an accurate rate of turn for a calculated time to end up heading in the required direction. Next I had to recover from "unusual attitudes" using just the limited panel instruments.

In this context, unusual attitudes are pretty tame, the nose will generally be within 20 degrees above or below the horizon and the wings within 45 degrees of bank.

An aeroplane can of course fly as much as 90 degrees nose up or down (straight to the sky or straight to the ground) and up 180 degrees of bank (upside down). This is the full range of attitudes that is actually possible, but normal training we are exploring just four or five percent of this envelope. In commercial aviation, it is even less.

So if we never experience the more extreme attitudes, how do we know how to react if we suddenly find ourselves in one? The answer is to strap in tight to a fully aerobatic stunt plane with a massively experienced instructor and do some...

...Upset recovery training

In three days of flying the awesome 300bhp Extra 300L fully aerobatic plane in all sorts of crazy attitudes and situations with APS training we were able to explore what happens way beyond our normal limits, both in terms of flying and what our stomachs could take! I should add that we were still nowhere near the limits of the aircraft, these things can take plus or minus eight g which is a lot more than I can.

So what is an aeroplane upset? Any time you are outside your normal operational limits for pitch, bank and speed, for whatever reason, you are obviously in an upset.

Less obviously, any time the plane does something you did not command on the controls, or does not do something you did command, it can be said to be upset. Most likely this is because you have stalled, but it could be a jammed or disconnected control surface or some other mechanical failure.

A stall occurs when the "angle of attack" — the angle at which the air hits the wing — is too great. It has nothing to do with speed, though trying to fly too slowly can certainly cause one. You can stall at any speed at attitude if you try (or if you don't pay attention) simply by pulling back too much.

We practice gentle stalls on our school Warriors regularly, and the results are an unspectacular nose drop, perhaps accompanied by one wing falling a little. The recovery is easy and equally undramatic. They are slow, stable, draggy machines designed to be easy to fly for students and amateurs.

Many aircraft do not do this. For example fast, slippery aircraft with thin swept back wings like the ones we should be flying in a year or so. In these machines, the stall can be sudden, violent and leave the aircraft in almost any attitude and falling fast.

One answer is simply to say "these aircraft shall never be allowed to stall," and go ahead and fit stick shakers, stick pushers, envelope protection and other funky gadgets to prevent the pilots being so stupid. But to err is human, and people are still dying because pilots lose control of even ultra-modern airliners because they stalled.

So this is what an Extra does if you stall it from a slipping turn. A slip, by the way, is a perfectly valid technique where the rudder is applied opposite to the bank angle. This makes the plane fly somewhat sideways, increases drag and increases descent rate. Very useful if you need to get down fast or fix a too-high approach to landing. A slip is a stall-resistant manoeuvre, look how hard I have to work to make the plane stall:

Look fairly dramatic? Compare this to a stall from a skidded turn. A skid is NOT a valid manoeuvre. A pilot will typically skid when trying to get around a turn faster using the rudder instead of banking over more. Reacting incorrectly to an engine failure on a twin engine plane can cause a skid too. Unlike the slipping turn when I really had to pull hard and ignore the plane shaking and complaining, this one had no warning at all...

If this happened on final turn, even with the excellent training we have just had, there is no room to recover before meeting the ground. The only answer is to fix it before it happens. We were told how to spot the skid (the slip ball moves to the high wing) and not to hesitate to fix the situation straight away, whether we are pilot flying or not. That's a lesson I won't forget in a hurry.

APS teach a fantastic recovery technique that's now drummed firmly into us; push, power, rudder, roll, climb. It works in almost every situation, even if you don't know how or why you got there. But there is one mode of flight where it will not help you — that is the fully developed spin.

This next video shows what a full spin looks like. We try various controls movements to escape, but as you can see none of them help and some make the spin faster. The only recovery that does work is the one I take at the end of the clip, although I fluff the calls a bit. Well, wouldn't you?

You can't see the altimeter very well in this video, but from the spin entry to when the instructor says "recover" we lose 4000 feet in 34 seconds! During the recovery I lose a further 1500 feet though I did better on subsequent attempts.

Being able to recover visually is one skill, but imagine you are flying happily along in the clouds when out of nowhere there is a thump and you are suddenly upside down. Panic? Freeze? Flail around on the controls? A week ago I'm sure I would have done something similar. But now...

That video shows the instructor using a snap roll to simulate the effects of wake turbulence — flying into the vortices left by a plane in front of you. I am under the hood here, eyes closed, not touching the controls and expecting a typical unusual attitude recovery. I manage to recover from violent inverted upset on instruments in only a few seconds. I am not trying to show off here — I am trying to show how invaluable this training really is.

Enough of the serious technical stuff. Part of the training is simply taking the fear out of being in unusual attitudes, having a "face full of dirt", and what better way to desensitise than trying our hands at some aerobatics?

Here is my first (and second) attempt at a Hammerhead. Sometimes incorrectly known as a stall turn, you pull vertically upward until you have almost run out of airspeed, then kick the rudder to rotate the plane sideways into a vertical dive (see picture on the right).

Sounds awful, but the whole thing happens close to zero g (yes, like in space!) and it is actually quite a gentle experience for the pilot until the pull-out at the end.

I also managed to fly some reasonable loops, Split Ss and Cuban 8s. To fly a Cuban 8 you do the first three-quarters of a loop,  roll back the right way up, pull up into another loop and do the same thing again. The full range of bank and pitch attitudes in a single manoeuvre.

Certainly not air show quality stuff, but I am very happy to have tried it.

If you have been to an air show recently, you may have seen a stunt pilot doing a vertical climb followed by a crazy tumbling manoeuvre. This is the Lomcevak (Czech for 'headache'). The plane is flown vertically until almost stationary, then some violent control input I don't understand causes it to do a gyroscopic precession around the rotating engine-crankshaft-propeller assembly. Or something. So when the instructor offered a demonstration, how could I say no? This one is certainly not gentle on the pilot or the plane!

It just remains to say a big thank you to the amazing staff at APS. All you pilots out there, private and commercial alike, think seriously about getting some upset recovery training like this. It may be expensive, but it might just possibly save your life and others too.

Before you go, please do consider donating a few points to the very worthy but under-sung causes of prostate and testicular cancer through my Movember page. I haven't quite made it to £100 yet, but even so, here it is at 14 days as promised. Pretty pathetic but I will keep trying...

* I passed by the way

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