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Why did they want us to maintain altitude

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Why did they want us to maintain altitude

Old 5th Aug 2018, 19:50
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Why did they want us to maintain altitude

As I go through the Airbus Upset Recovery Training they mention about how we used to try to maintain altitude in a stall recovery in the sim until the obvious became obvious and it was not longer trained that way.

But one does have to ask, how did it become that way in the first place. Was there a desire by the Powers That Be to not have an ATC violation or was it assumed that a stall could only ever happen close to the ground.

Was this something that came from the manufacturers or the regulators?

Perhaps it is all lost in the sands of time but it would be interesting to know how it was done back in the '60's or earlier.

Anyone?
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Old 6th Aug 2018, 15:20
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Originally Posted by JammedStab View Post
As I go through the Airbus Upset Recovery Training they mention about how we used to try to maintain altitude in a stall recovery in the sim until the obvious became obvious and it was not longer trained that way.

But one does have to ask, how did it become that way in the first place. Was there a desire by the Powers That Be to not have an ATC violation or was it assumed that a stall could only ever happen close to the ground.

Was this something that came from the manufacturers or the regulators?

Perhaps it is all lost in the sands of time but it would be interesting to know how it was done back in the '60's or earlier.

Anyone?
I believe the old drill was based on the assumption that it was a departure or arrival stall.
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Old 6th Aug 2018, 15:57
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Originally Posted by JammedStab View Post
As I go through the Airbus Upset Recovery Training they mention about how we used to try to maintain altitude in a stall recovery in the sim until the obvious became obvious and it was not longer trained that way.

But one does have to ask, how did it become that way in the first place. Was there a desire by the Powers That Be to not have an ATC violation or was it assumed that a stall could only ever happen close to the ground.

Was this something that came from the manufacturers or the regulators?

Perhaps it is all lost in the sands of time but it would be interesting to know how it was done back in the '60's or earlier.

Anyone?
Can't speak for Airbus but we used to differentiate between "stall without risk of imminent ground contact" and "stall well clear of ground" on several types I flew. "Without risk of imminent ground contact" it was like the current "shove stick forward, accelerate, gently pull" while "with risk of imminent ground contact" you'd apply maximum thrust and try to lose as little altitude as possible while accelerating.

AFAIK this technique was rescinded after or at least around the Air France accident, probably with the background that there are circumstances where it will not work, i.e. if you're so far behind the power curve that the aircraft will not accelerate without dropping the nose, and given that a stalled wing can only be recovered by lowering angle of attack.

I'd still be reluctant to push forward heartily if I e.g. botched a turn during a circling approach/visual pattern and got a rattle of the stick shaker, where a dab of power will accelerate the A/C sufficiently to avoid harm. The current theory says "push down" regardless of circumstances, but I haven't so far got a reply whether that's really a good idea in the "very low" scenario.
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Old 6th Aug 2018, 16:55
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AFAIK this technique was rescinded after or at least around the Air France accident
A SAFO was issued after Colgan air stall on Approach which got aggravated after thrust was applied and crashed. In the airbus video on stall it is stated that the old recovery method was based on Approach to stall condition where stall warning gets activated. It further states that even for a test pilot it is difficult to differntiate between full stall and incipient stall. Therefore there must be standard procedure to treat it as AOA phenomenon. The procedure is in two parts. First is unstalling the wing and second is recovery of flight path. This procedure makes people uncomfortable in case of low level stall with ground contact possibility. It has been discussed even with airbus. The point is there are no two procedures. As for low level, aircraft should not be stalled close to the ground and if stalled fully some loss of altitude is inevitable and it will not recover as in Colgan case with a bash of thrust. If it's case of stall warning activation where aircraft is not stalled but close to stall it may recover with thrust. So first AoA must be reduced but the second part the recovery of Flight path can be started sooner to reduce loss of of altitude.

Last edited by vilas; 6th Aug 2018 at 17:10.
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Old 6th Aug 2018, 17:02
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The A330 manual at our company does have a stall recovery after take off memory procedure vs. the regular stall recovery procedure.

The procedure calls for TOGA and to set pitch to 15 degrees. At low altitudes the ability to simply power ones way out of a stall is much greater than at altitude.

My company now insists on all pilots performing at least one stall recovery every six months. It alternates between low and high altitude. In my experience if the recovery is done at a standard pace while taking care of the secondary stalls, at low altitudes 700 feet is about what one can expect to loose.

The secondary stalls is also far more common on the narrow bodies.
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Old 6th Aug 2018, 17:44
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At low altitudes the ability to simply power ones way out of a stall is much greater than at altitude.
powering out of stall is conceptually wrong. Because thrust increases speed to help recovery but stall is AoA phenomenon and aircraft can stall at any speed. At altitude it is useless it takes ages to recover even cruise speed after some drop in speed.
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Old 6th Aug 2018, 17:57
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Originally Posted by vilas View Post
powering out of stall is conceptually wrong. Because thrust increases speed to help recovery but stall is AoA phenomenon and aircraft can stall at any speed. At altitude it is useless it takes ages to recover even cruise speed after some drop in speed.
Sure but an increase in speed while pitch remains constant increases the lift and thus changes the aircraft trajectory, which in turn lowers the angle of attack. I guess Airbus also figures that most pilots will react before the stall gets too serious, in which case there's still time to power out. The stalls done in the Sim are well past the incipient stage.

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Old 6th Aug 2018, 19:23
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If you ever get to the point of stalling an airliner, then the emphasis has to be on unloading the wing so youíre flying again and under some sort of control. Everything else goes out of the window. Get as close to the ground as you like during the recovery as long as you donít hit it: if you have speed (== life) you can pull out - if youíre still at the far end of the drag curve you might not be able to.

I take the view that if you manage to unwittingly aerodynamically stall a jet transport aircraft, especially at low level, then youíre probably going to screw up the recovery as well...
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Old 6th Aug 2018, 19:58
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Originally Posted by Airmann View Post
Sure but an increase in speed while pitch remains constant increases the lift and thus changes the aircraft trajectory, which in turn lowers the angle of attack.

​​​​​
This is true, but in the end the reduction in AOA is accomplished by the stick being pushed forward, as it always is; and this must not be forgotten. (Especially in planes with underwing engines and a nose-up thrust couple.) The phrase "powering out of the stall" needs to die in a fire, starting yesterday, because people are always going to misinterpret it in the most simplistic way possible. Say "only reduce the AOA a little bit" instead.
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Old 6th Aug 2018, 19:59
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Originally Posted by FullWings View Post
I take the view that if you manage to unwittingly aerodynamically stall a jet transport aircraft, especially at low level, then youíre probably going to screw up the recovery as well...
Take a look at the RYR incident in Eindhoven:

Ryanair Eindhoven incident

They went from chasing the glide idle thrust fully configured to 20į nose up and sped dropping through the floor in half a second. The copilot recovered the aircraft beautifully. It does happen...
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Old 7th Aug 2018, 05:56
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Originally Posted by Airmann View Post
The A330 manual at our company does have a stall recovery after take off memory procedure vs. the regular stall recovery procedure.

The procedure calls for TOGA and to set pitch to 15 degrees. At low altitudes the ability to simply power ones way out of a stall is much greater than at altutude.
The same exists on the small bus, however it explicitly notes that spurious stall warnings at take are something that happens because of a damaged AoA probe and the procedure is designed to take one safely out of the danger of ground contact.
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Old 7th Aug 2018, 07:55
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Originally Posted by Alpine Flyer View Post
Can't speak for Airbus but we used to differentiate between "stall without risk of imminent ground contact" and "stall well clear of ground" on several types I flew. "Without risk of imminent ground contact" it was like the current "shove stick forward, accelerate, gently pull" while "with risk of imminent ground contact" you'd apply maximum thrust and try to lose as little altitude as possible while accelerating.

AFAIK this technique was rescinded after or at least around the Air France accident, probably with the background that there are circumstances where it will not work, i.e. if you're so far behind the power curve that the aircraft will not accelerate without dropping the nose, and given that a stalled wing can only be recovered by lowering angle of attack.

I'd still be reluctant to push forward heartily if I e.g. botched a turn during a circling approach/visual pattern and got a rattle of the stick shaker, where a dab of power will accelerate the A/C sufficiently to avoid harm. The current theory says "push down" regardless of circumstances, but I haven't so far got a reply whether that's really a good idea in the "very low" scenario.
I do think they are making a mistake trying to sell everyone a "one size fits all" recovery. Obviously a great lesson to be learned from several crashes, and a full stall has to lower nose or angle of attack to recover, but it is hard to get in a full stall in modern aircraft with all the safety nets built into planes.......but like you are saying it seems like common sense to slightly lower nose and add thrust at initial stick shaker when at 500 feet on base turn. The new group of aviators will have only ever learned nose down and power idle until fully recovered then smoothly add power, and that is likely to also cause a crash someday too
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Old 7th Aug 2018, 08:46
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Take a look at the RYR incident in Eindhoven:
Interesting one. Lots of lessons for everybody there but the recovery *was* screwed up as power was put on first (TOGA) *then* an attempt to pitch down, which was made much harder by the large pitch/power couple now existing. They went to 26.5degs NU and 97kts before getting the pitch under control. Not getting at the pilots in any way as they were handed a really nasty situation, although the approach was not (and was never going to be) stable at any point...

The new group of aviators will have only ever learned nose down and power idle until fully recovered then smoothly add power, and that is likely to also cause a crash someday too
Possible but what really starts the whole chain of events is getting the aeroplane in a low energy state near the ground. Itís hard to deliberately fly something into the deck (unless thatís what you want) but it is easy to be forced into it due lack of energy. There is an area in the flight envelope for most aircraft (with the exception of very high thrust:weight ratios) where drag overwhelms power available and you need to get out of that area before a recovery can be effective.

If youíre getting stick shaker at 500í, then either conditions are such that an approach is not prudent or you havenít been paying attention to flying basics, in which case I refer to my earlier comment about recoveries. The stick shaker doesnít change its tune whether you are 1kt or 15kts into its warning envelope, so youíre experiencing a time-critical event and need to do the right thing right now!
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Old 7th Aug 2018, 13:45
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Originally Posted by JammedStab View Post
As I go through the Airbus Upset Recovery Training they mention about how we used to try to maintain altitude in a stall recovery in the sim until the obvious became obvious and it was not longer trained that way.

But one does have to ask, how did it become that way in the first place. Was there a desire by the Powers That Be to not have an ATC violation or was it assumed that a stall could only ever happen close to the ground.

Was this something that came from the manufacturers or the regulators?

Perhaps it is all lost in the sands of time but it would be interesting to know how it was done back in the '60's or earlier.

Anyone?
I think it was due to the wording of the Practical Test Standards in use at the time, which mandated a stall recovery with minimum loss of height. If you lost more than 100ft(?) during the recovery, you failed the test. The only way to achieve that was to add loads of power and only lower the nose a tiny amount.

This requirement was fed back into the type-rating training courses and this eventually became the ‘standard method’ of teaching stall recovery. It was certainly the way I was taught to recover in the 737 and 747. I thought it was wrong at the time (unless at very low altitude) but discussing it with the examiner did not prove worthwhile.

I was pleased when both Boeing and Airbus revised their techniques following the Colgan, Air France and Turkish crashes. I was taught the ‘stick forward first’ method on the A320 and 787.
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Old 7th Aug 2018, 14:45
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The stalls done in the Sim are well past the incipient stage.
Deep stalls are not truly represented in normal Simulators and they are not to be practiced that way. This is clarified by Airbus.
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Old 7th Aug 2018, 15:33
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I do think they are making a mistake trying to sell everyone a "one size fits all" recovery
With our operation (737) in the simulator during type rating and recurrent training, we practice two types of recoveries. High and low altitude recoveries. At 37,000 ft at buffet/stick shaker, we lower the nose to zero degrees body angle or slightly lower, while at the same time apply GA power. Since the thrust is only about 4000 lbs aside at that height (as against 20K at sea level) the pitch up is hardly noticeable and easily counteracted.
At zero body angle the speed increases slowly until at 230 knots IAS we gently level out. This results in about 3000 feet loss of height. The 230 knots IAS figure comes from the FCTM where it says if FMC speeds not available above 25,000 ft use Vref40 +100 knots for holding. That is roughly 230 knots IAS.

If the stall was due to mishandling in severe turbulence and during the recovery severe turbulence still exists, then the aircraft is held in the descent angle until severe turbulence speed in attained and then recovered to level flight. Expect a height loss of 5000 ft. In each case no attempt is made to revert to level flight until those safe airspeeds are attained.

For low altitude practice stall on final approach, the autopilot is coupled to the ILS and at 1500 ft agl both thrust levers set to idle. The AP trims the stabiliser more or less continually backwards as the AP tries to fly the glide slope and the IAS reduces until around Vref minus 25 knots the stick shaker goes off. There is no discernible buffet. By the time the airspeed reaches Vref minus 25 and the stick shaker operates (and you wonder how crews has missed the speed indications in previous accidents/incidents) , the stabiliser trim would have moved back to about 13 units under the AP as it tries to hold the ILS glide slope angle.

Max (firewall) power is applied, the AP is disengaged and nose lowered to around five degrees nose up. Anything lower than that will result in severe height loss which could be dangerous if close to the ground. It then becomes a compromise between descending while close to the ground and picking up speed and trying to "claw" your way up at low speed. At the same time the pitch up caused by full power is contained by strong forward control column while simultaneously applying immediate continuous forward stabiliser trim for about seven seconds to place the trim in a position where the forward elevator pressure becomes effective. While still maintaining five degrees nose up, the IAS gradually increases, although some height loss occurs but only for a few seconds.

By now, about 3-500 feet has been lost during the recovery and as soon as airspeed passes through Vref in the ensuing climb, the aircraft is pitched up to normal GA attitude and Flaps 15 selected. Flap is left at landing flap until Vref is reached on the recovery. That is because if flap is selected to 15 as part of the recovery while airspeed is well below Vref then the aircraft is in danger of stalling.

I am sure there are other ways "to skin the cat" as the saying goes, but these two methods work well in the simulator.
Constructive criticism welcomed but please don't shoot the messenger on this one

Last edited by Judd; 7th Aug 2018 at 16:01.
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Old 7th Aug 2018, 16:11
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Constructive criticism welcomed but please don't shoot the messenger on this one
Nothing to criticise, it just shows how complicated it can get if you let a low speed situation develop without intervention. Add in startle effect and you can see why there are hair-raising incidents and hull losses. At least your organisation is getting you to practice these things so the awareness is there.

The stabiliser is effectively the most powerful flying control on the 737 (and other types) and the elevator is the trim. Moving the stabiliser for long periods in one direction can be the best way out of a bad situation or if done wrong, seal your fate. Scary stuff in a situation where SA has by definition been severely degraded or lost altogether...
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Old 7th Aug 2018, 16:56
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Originally Posted by vilas View Post
powering out of stall is conceptually wrong. Because thrust increases speed to help recovery but stall is AoA phenomenon and aircraft can stall at any speed. At altitude it is useless it takes ages to recover even cruise speed after some drop in speed.
So why is there such a huge emphasis on 'stall speeds' in training?

Also, why in the current aircraft I'm training on (C172) if i pull nose up to say 20 degrees pitch at 100 kts on idle power, I don't stall (at least not for a short while). However, if I pull nose up at 50 kts with full flaps, stall will be imminent, without even being able to reach 20 degrees pitch up.

I am not disagreeing with what you say, just interested in the answer. In ground school we learned about the critical angle and that a stall can happen at any speed etc etc, but then we learn about Vs, Vs1 etc and see our susceptibility to stall is determined according to these speeds, even with 0 degrees pitch you'll stall at not much beneath them.
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Old 7th Aug 2018, 19:25
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Originally Posted by Officer Kite View Post
So why is there such a huge emphasis on 'stall speeds' in training?

Also, why in the current aircraft I'm training on (C172) if i pull nose up to say 20 degrees pitch at 100 kts on idle power, I don't stall (at least not for a short while). However, if I pull nose up at 50 kts with full flaps, stall will be imminent, without even being able to reach 20 degrees pitch up.

I am not disagreeing with what you say, just interested in the answer. In ground school we learned about the critical angle and that a stall can happen at any speed etc etc, but then we learn about Vs, Vs1 etc and see our susceptibility to stall is determined according to these speeds, even with 0 degrees pitch you'll stall at not much beneath them.
A stall at Va is a limit load. Any stall above Va is an ultimate load
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Old 7th Aug 2018, 23:47
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Maintaining altitude was never my concern but containing the stall to a smaller block with power or thrust is what one is trying to accomplish...lower the AOA while setting max thrust is how I've always seen.
Edit: Yes I'm aware of the thrust possibly causing nose up in the recovery but pilots are supposed fight that if expected


Just to add the the maximum weight to ever be carried by the wing is the weight that the wing carries at stall

Last edited by Pugilistic Animus; 8th Aug 2018 at 00:12.
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