Stall recovery on twin pistons!

[despegue]

Last week, I flew as an observer on a training flight with a Seneca, flown by a very experienced instructor and his student.
At stall, this instructor immediately ordered full power and nose down.
After the flight, I had a private chat with this instructor about my opinion that this stall recovery might be the thing to do in a single engine, but is potentially disasterous on a twin due to the fact that stall speed with full flaps is often below the "red line" (Vmca).
So if you had an engine malfunction at application of full power, you would end up with an uncontrollable aircraft.
I have always been taught by my twin instructor at Airmed that at stall, smoothly nose down, controls centered and let speed increase until passing red line, then smoothly full power.
I now fly B737's and don't even have a twin piston rating anymore, but I do wonder who is right here.
How do you teach the twin stall recovery?

[fireflybob]

What does the specific type Flight Manual/POH say about stall recovery?

[IRRenewal]

despegue,

I fully agree with you. No power below Red Line, climb away at Blue Line. An instructor demanding full power below red line has a death wish.

What did the instructor say when you had a chat with him?

[hugh flung_dung]

despegue,
I agree with you if they opened the throttles rapidly but there's nothing wrong with opening them together slowly.
Vmca (red line) is defined as the speed at which, if sudden complete failure of the critical engine occurs when in straight, steady flight (flaps, etc in T/O position, gear retracted) it is possible without reducing thrust to regain and maintain straight steady flight at the same speed (I can't remember off hand where the CG is but suspect it's at the rear limit - worst case). Providing you bring the power up slowly you will have accelerated through Vmca long before even half power is reached.
BTW I hope the sequence was "stick sufficiently far forward to unstall the wing" and THEN smoothly up to full power.
HFD

[bookworm]

The event that you're simulating is an inadvertent stall. This is likely at low level where height is critical. In such a situation minimizing height loss during the stall is paramount.

The probability of an engine failing catastrophically at that same moment is vanishingly small. Even if it does, application of full power is not immediately fatal -- but it does require very rapid action, just like an engine failure on the take-off roll below Vmcg.

That leads me to the conclusion that not applying maximum power in the case of an inadvertent stall is poor risk management. There seems little point in practising as a drill a different recovery technique. Power can be monitored carefully for its symmetry during the initial stages of the recovery.

[despegue]

Bookworm,

There is a seperate manoeuvre for approaches to stall near the ground, in landing config.
This is called "the characteristic stall" in Spain, and I'm sure that it is practiced elsewhere under a different name.
You perform this at stall WARNING, which starts above red line, so immediate action IS possible by applying smoothly full power, while preventing the aircraft to balloon and yaw, but at the same time not descending one foot anymore.
The normal stall exercise is a simulation of a situation where there IS enough height available for normal recovery.
Let us not mix these 2 situations.

[bookworm]

You perform this at stall WARNING, which starts above red line...

It isn't on mine (Twin Comanche). It isn't even close. Vmca is 90 mph. Stall is 70 mph.

I take your point about having two distinct exercises, though I'm not convinced that the height is unimportant in the "normal stall" exercise. My recollection is that recovery is meant to be with minimum height loss.

[willbav8r]

Hence the Vmc demo where one realises it is a bit quieter on one side - reduce power on the operating engine and lower nose. Bring back the power nicely to avoid loss of directional control.

All depends on how smoothly someone is applying power. Jam 'em forward in under 1/2 second and there may not be a chance if one falters. A second or two should give enough warning if one is not developing power?

So, assuming this is done as an approach stall (hence full flaps) the ground is likely to be a bit too close for comfort. options: impact ground or possible Vmc roll. In that order.

But, some aircraft have plenty of power, and full chat ain't necessary. Dunno if the Seneca falls into this category in whatever scenario it might have been (high airport / dens alt)?

[machonepointone]

The standard stall recovery is "control column centrally forward to unstall the wings and apply full power." There is a bit more to it but those two actions are what it takes to unstall an aircraft with minimum height loss. Anything else is guaranteed to earn a fail with a CAA examiner (or CAA authorised examiner) irrespective of what type of aircraft you are flying and the number of engines that it has since the requirement on the CPL and IR Skill Tests are recovery with minimum height loss. Unnecessarily waiting for Blue Line will cost 637 pounds which is, I believe, the current test fee for the previously mentioned flight tests. Based on Seneca stall speeds that works out at about 21 pounds per knot!

As Bookworm rightly says, the chances of entering an inadvertant stall and subsequently losing an engine are pretty remote. I appreciate that we teach and train for the real event, but in practice all training stalls should be carried out at a safe altitude, usually one that ensures recovery from the stall by not less than 2000 feet agl. Under these circumstances the recovery in the event of an engine failure during the recovery would be to reduce power on the live engine (idle if necessary), in order to maintain directional control.

Despegue did not mention what mark of Seneca he was in, nor the type of stall he was observing, but the Mark IIIs that I currently fly, and the Mark IVs that I used to fly, have a Vmca of 66 knots which is generally not more than 10 knots above the stall speed. However, we teach that the recovery from any stall other than a clean one must be taken at the first sign of an approaching stall (ie stall warner or buffet, whichever comes first), which means in practice that the recovery almost invariably begins at a speed at or slightly above Vmca.

So, to sum up, any inadvertant stall should have the pilot initiating recovery at the stall warner which should ensure a speed in excess of Vmca. Practice stalls, where the speed may be below Vmca, are done at an altitude sufficient to allow recovery from the stall with the throttles closed in the unlikely event of an engine failure at that time. So long as the engines keep working, therefore, there is no problem in using the correct stall recover technique which includes the use of full power. As an instructor for the last 24 years I can assure IRRenewal that I do not have a death wish any more than any of my colleagues.

[whatunion]

full thrust or power is not standard on all a/c and all situations

[fireflybob]

From my earlier posting:-

"What does the specific type Flight Manual/POH say about stall recovery?"

Well?

[machonepointone]

Fireflybob,

Good question(s) but the Seneca POH does not give any guidance about stall recovery techniques other than to quote possible height loss.