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Mythbusters

This is obviously type dependent but assymetric flap deployment is likely to make the aircraft totally uncontrollable in roll.

Just maybe, the ailerons might have enough authority if the assymetry was limited, but no way would that be the case (on most GA types) with one flap going to the full landing position.

I once had asymmetric flap extension, in a TB10 in fact. It was due to faulty maintenance, the torque tube was not fastened to the airframe in one wing

I wonder how far up the chain was this reported... that's terrible.

Out of curiosity I've just opened up an out of warranty KS271C autopilot roll servo (which I have had as a spare for several years) and found the two power transistors not screwed down onto the heatsink. That servo would have burnt out (literally burnt out - they do!) within minutes, if not seconds, of the autopilot being engaged. Can anything be done about it? No. It comes with original Honeywell paperwork, so it is perfect.

Administrator
Shoreham EGKA, United Kingdom

Backpacker makes a good point. At the beginning of the circuit lessons for ab initio training I discourage flap deployment in the turn for the reasons he stated. However as the student gains competence and confidence I don't have a problem with the practice. Of more interest to me is the the bigger issue of aircraft management. In other words is the circuit square and with a sensible flight path. If the student puts a bunch of flap out in the turn because they are too close and too high and rushing to get down the issue is not flap deployment it is the issue of not staying ahead of the aircraft.

For advanced training I expect the student to do what it takes to make the airplane go where it needs to be. Under some scenarios adding or even reducing flap in the turn is the most appropriate action.

The central question is has there ever been a case where there was an asymmetrical deployment of flaps that resulted in an accident where the plane would not have crashed if the asymmetrical deployment had occurred in level flight. I challenge anyone to produce even 1 accident or incident report where this occurred.

Yes anything Can happen but how likely is it ? I think the risk is probably about the same magnitude as the risk of the extra loading on the down going wing causing it to fail from some hidden fault. So using that logic we should never turn........

I think this is an example of somebody in a flight school holding an opinion which has then been mindlessly passed down without any critical examination from instructor to instructor.

Another flight school myth which I find particularly irksome is the common. " Oh the fuel gauges are always wrong so you can pretty well ignore them" .

We recently had an aircraft written off at my home airport. He was "sure" he had enough fuel and the fuel gauges sitting on "E" must be wrong .....until the engine stopped.

Wine, Women, and Airplanes = Happy
Canada

Another flight school myth which I find particularly irksome is the common. " Oh the fuel gauges are always wrong so you can pretty well ignore them" .

Well yes and no. On the PA-46 the Piper supplied gauges are rubbish - although apparently a new revision is about to be released. We have an added complication in that we have the extended fuel caps STC installed which means that Instead of the Avidyne shown 120 gallons, we actually carry 152. There is unfortunately no way currently to reset that in flight (after 32 gallons used). However, the totaliser (fuel used) is correct and will continue to count up above 120.

So we have inaccurate tank gauges, a fuel remaining number which is wrong but an accurate fuel used. As a result you monitor the amount in the tanks based on the fuel used 10, 30, 50 gallons etc.

That said, if I lost track and a gauge showed a low fuel amount I would assume it was correct.

EGTK Oxford

Leaning your engine too much will destroy it.

That is not a myth - that is a fact!

Don't fly too slow, and never fly fas...
at the moment I spend a lot of time in LFMN

That is not a myth - that is a fact!

Only if you lean at high (excessive) power settings.

For Lyco engines, the limit is generally 75% of max rated power. At or below 75% you are authorised to run at peak EGT, which is very very close to the optimal SFC (MPG, if you like).

Administrator
Shoreham EGKA, United Kingdom

Jason

The central question is has there ever been a case where there was an asymmetrical deployment of flaps that resulted in an accident where the plane would not have crashed if the asymmetrical deployment had occurred in level flight. I challenge anyone to produce even 1 accident or incident report where this occurred.

Reading the report I see no evidence that putting flaps down in a turn or turning with flaps caused the aircraft to crash. It crashed in level flight when it stalled above the runway. It is also a fact that the accident rate due to structural failure is much higher in experimental aircraft then it is in certified aircraft and so care needs to be taken when extrapolating data from one part of aviation, across all types of flying.

I still believe that it is very unlikely anyone could find an accident report that meets the requirements of the central question above.

However I suppose that if it makes you feel better there is nothing inherently wrong with choosing to not deploy flaps in a turn although I feel the risk is so negligible that it is an unnecessary precaution and pilots should worry about the many many higher probability potential problems that could occur.

One thing I am hard over on, is that for anyone who advocates that turns with flaps are dangerous, is IMO being just plain silly.

Wine, Women, and Airplanes = Happy
Canada

Interesting to read everyone's thoughts on flap deployment (or retraction, possibly) in a turn. Thinking hard, I believe the reason I was given during my training is that doing so changes the aerodynamic qualities of the aircraft at a moment when flying it requires slightly more attention anyway (managing the turn), as BackPacker and BPF have mentioned.

The implication, though, was that one shouldn't do it, full stop. But with safety in mind, maybe some (many?) instructors prefer to err on the side of caution, giving simple, conservative rules that are easier to recall later on, i.e. a long time after initial training?

I can't recall asymmetry being mentioned. I'll be asking some tough questions next time I get hold of an instructor, LOL.

Bordeaux

Thinking hard, I believe the reason I was given during my training is that doing so changes the aerodynamic qualities of the aircraft at a moment when flying it requires slightly more attention anyway (managing the turn), as BackPacker and BPF have mentioned.

I think that is reasonable. It's just like not changing fuel tanks, or engine power settings, when over water, or over the Alps, or at low level

Sometimes, one has to bring in the full landing flap during a bank when flying a tight circuit, to prevent the aircraft accelerating during the descent.

Administrator
Shoreham EGKA, United Kingdom

One shouldn't use flaps in a turn?

Why Not?

In the UK advice on how to fly the base leg and final approach was produced some years ago on the recommendation of the AAIB following a number of accidents in the base turn. The objective was to reduce the workload for inexperienced pilots by spacing events, rather than doing several things at once with the possibility of loss of control.

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