Menu Sign In Contact FAQ
Banner
Welcome to our forums

Stalling near the operating ceiling

I have just read a somewhat scary account of somebody doing this in a TB21.

He did a power-on stall. He is not saying how high but probably at FL200-250. Instead of stalling it simply rotated in what appeared to be slow motion, with the nose going further up until they were upside down hanging in their seat belts. He recovered by centering everything and just leaving it, and after a few more tumbles it recovered by itself.

There was an SR22 high altitude accident where the pilot said it was just turbulence which caused it to enter a spin, and he pulled the chute.

I wonder if this sort of thing is normal. I have always found the TB20 to be stable high up but then I was never throwing it around.

Administrator
Shoreham EGKA, United Kingdom

I thought the risk of stall at high altitude was high only for non-turbo planes. When I used to own a non-Turbo SR22, the autopilot almost stalled the plane at FL180 above the Alps because of a downdraught. I was lucky to have the IAS under my attention in that specific moment, because all happened very quickly and no way I could have felt what was going to happen in any other way. One of the reasons I now have a Turbo with an autopilot (GFC700) intelligent enough not to stall the plane.

So it rotated and tumbled before stalling (stall warner sounding, buffeting etc?) Would this be what is otherwise termed as a ‘wing over’ or incipient spin, which normally would happen after a stall.

Last Edited by PiperArcher at 26 Jun 15:28

It sounds very strange.

Obviously an aircraft at its ceiling is quite close to the stall in normal – level flight.

But the description of the nose rising and going back over itself sounds very strange.

Is their any possibility that the pilot had inadequate supply of Oxygen and their recollection might not be reliable? Certainly a roll seems much more likely than a ‘head over heal’ roll.

EIWT Weston, Ireland

I heard a report that a CJ2 was seriously damaged recovering from a high altitude stall, the incident was near Honily I believe, and the aircraft returned to Leeds. Apparently there was serious structural damage.

It is a difficult situation to train for

Darley Moor, Gamston (UK)

You may all be aware of this, but in high altitude flight with jets there is an aerodynamic spot called “coffins corner”. The aircraft can maintain flight at a certain speed, but going faster or slower causes it either to tuck under (nose over) or stall. The certified performance envelope is limited to ensure that the aircraft is never operated in this region under normal conditions.
With an aircraft and airfoil designed to operate in the lower regions of altitude one should expect non-standard behavior at high altitudes. This is one reason why ATPL studies include additional aerodynamics, both to take in account the higher speeds, ram effect, supersonic drag and also the different stall characteristics.

I’m sure the TB21 is certified to the altitude at which he was flying, but the stall characteristics are probably not tested extensively at FL250.
What was his loading condition at the time? Near the rear limit? How does the loading affect stall characteristics at altitude, is the envelope really linear all the way up?

ESSB, Stockholm Bromma

Much as this is a TB20/21 supporters’ site it is unlikely any part of the aircraft would experience transonic flow!

Flutter characteristics are linked to TAS and therefore this has some role in certifying ceilings for turbo charged aircraft below their aerodynamic service ceiling – it is also one of the reasons why your red line on turbine conversions is top of the green.

The incident cited sounds as if he entered into a hung loop – why undertake a power on stall, possibly accelerated, at service ceiling is an interesting question.

Oxford (EGTK), United Kingdom

I thought the risk of stall at high altitude was high only for non-turbo planes. When I used to own a non-Turbo SR22, the autopilot almost stalled the plane at FL180 above the Alps because of a downdraught. I was lucky to have the IAS under my attention in that specific moment, because all happened very quickly and no way I could have felt what was going to happen in any other way. One of the reasons I now have a Turbo with an autopilot (GFC700) intelligent enough not to stall the plane.

FL 180? In a SR22 N/A? Presumably this was an STEC 55 autopilot? They will happily fly you into a stall at any altitude, if conditions are right for that, and then disconnect and leave you to sort the resulting mess out yourself.

Your GFC 700, of course, has envelope protection as does the Avidyne DFC 90 to which many pre-Perspective Cirrus pilots have upgraded and which is in every way a far better autopilot.

EGSC

if conditions are right for that, and then disconnect and leave you to sort the resulting mess out yourself.

Yes but a proper plane in a coordinated flight (ball in the middle) should just stall, straight ahead. It should not enter a spin at that point.

If I set say 200fpm on my KFC225, the TB20 will stall at maybe 17000ft, but first the stall warner comes on and later you get the buffet. It should not anything crazy. That is assuming the pilot is conscious and has been adjusting the rudder trim, increasingly, to keep the flight coordinate.

You don’t need envelope protection. You just need a pilot who is basically awake

Much as this is a TB20/21 supporters’ site

No it isn’t TB owners feature no more here than the other types. I could probably extract the stats, but many people have not filled in anything in their profile.

I thought the risk of stall at high altitude was high only for non-turbo planes

A turbo plane will do it just the same, but higher up.

Administrator
Shoreham EGKA, United Kingdom

Peter you do not need to be an owner to be a supporter! You mis read my intent, I was just amused at the thought of a TB21 experiencing transonic flow.

Oxford (EGTK), United Kingdom
26 Posts
Sign in to add your message

Back to Top