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JammedStab
5th Aug 2018, 20:50
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?

aterpster
6th Aug 2018, 16:20
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.

Alpine Flyer
6th Aug 2018, 16:57
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.

vilas
6th Aug 2018, 17:55
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.

Airmann
6th Aug 2018, 18:02
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.

vilas
6th Aug 2018, 18:44
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.

Airmann
6th Aug 2018, 18:57
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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FullWings
6th Aug 2018, 20:23
If you ever get to the point of stalling an airliner, then the emphasis has to be on unloading the wing so you’re 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 don’t hit it: if you have speed (== life) you can pull out - if you’re 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 you’re probably going to screw up the recovery as well...

Vessbot
6th Aug 2018, 20:58
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.

Jwscud
6th Aug 2018, 20:59
I take the view that if you manage to unwittingly aerodynamically stall a jet transport aircraft, especially at low level, then you’re probably going to screw up the recovery as well...

Take a look at the RYR incident in Eindhoven:

Ryanair Eindhoven incident (http://avherald.com/h?article=4641efec/0000)

They went from chasing the glide idle thrust fully configured to 20° nose up and sped dropping through the floor in half a second. The copilot recovered the aircraft beautifully. It does happen...

Denti
7th Aug 2018, 06:56
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.

casablanca
7th Aug 2018, 08:55
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

FullWings
7th Aug 2018, 09:46
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. It’s hard to deliberately fly something into the deck (unless that’s 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 you’re getting stick shaker at 500’, then either conditions are such that an approach is not prudent or you haven’t been paying attention to flying basics, in which case I refer to my earlier comment about recoveries. The stick shaker doesn’t change its tune whether you are 1kt or 15kts into its warning envelope, so you’re experiencing a time-critical event and need to do the right thing right now!

eckhard
7th Aug 2018, 14:45
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.

vilas
7th Aug 2018, 15:45
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.

Judd
7th Aug 2018, 16:33
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

FullWings
7th Aug 2018, 17:11
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...

Officer Kite
7th Aug 2018, 17:56
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.

Pugilistic Animus
7th Aug 2018, 20:25
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

Pugilistic Animus
8th Aug 2018, 00:47
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

zzuf
8th Aug 2018, 02:10
A stall at Va is a limit load. Any stall above Va is an ultimate load

Well that depends entirely on what speed the manufacturer decides to use as Va.

Pugilistic Animus
8th Aug 2018, 02:32
Well that depends entirely on what speed the manufacturer decides to use as Va.
That is true, I should have said stall limited Va...Actual stall limited Va (Vp) is always changing because Va is a function of stall speed and design limit load

Vp= Vs×n^0.5 where n is the limit load

zzuf
8th Aug 2018, 03:03
That is true, I should have said stall limited Va...Actual stall limited Va (Vp) is always changing because Va is a function of stall speed and design limit load

Vp= Vs×n^0.5 where n is the limit load

No, Va is a function of whatever the manufacturer chooses.
The only time Va is a function of stall speed is if the manufacturer decides to use Va min as the design Va.
There is no airworthiness design requirement for Va to have any relationship to limit load, or perhaps you can point to one.
There is nothing to stop a designer selecting Va=Vne
To try to put the long held Va myth to bed the FAA found it necessary to use a new speed - Vo.

vilas
8th Aug 2018, 06:30
lower the AOA while setting max thrust is how I've always seen. No! Thrust comes in only after stall warning/indication has stopped and not simultaniously.
Edit: Yes I'm aware of the thrust possibly causing nose up in the recovery but pilots are supposed fight that if expected It may not be possible as happened in Colgan case. With a stalled wing you can't fight the pitch up. That's the whole point in having this new look at stall recovery. You cannot afford to stall at low level and then seek guarantees. You are taking a chance. In any case in Airbus stall is an issue only in alternate law that too with four cases of alternate law with no protection. In other cases of reduced protection the nose will drop unless sustained back pressure is maintained on the side stick.

zzuf
8th Aug 2018, 07:22
No! Thrust comes in only after stall warning/indication has stopped and not simultaniously.
It may not be possible as happened in Colgan case. With a stalled wing you can't fight the pitch up. That's the whole point in having this new look at stall recovery. You cannot afford to stall at low level and then seek guarantees. You are taking a chance. In any case in Airbus stall is an issue only in alternate law that too with four cases of alternate law with no protection. In other cases of reduced protection the nose will drop unless sustained back pressure is maintained on the side stick.

My reading of the Colgan accident was that the pilot responded to a stick shaker operation with a nose up control input, then over rode the stick pusher 3 times. Most (probably all) certificated aircraft do not pitch up uncontrollably when stalled.

vilas
8th Aug 2018, 11:56
Most (probably all) certificated aircraft do not pitch up uncontrollably when stalled. If that be the case then why would the manufacturers say so? Not only that they further explain should it happen you may have to reduce thrust to reduce the AoA. Swept wing aircraft have a tendancy to pitch up at stall and that gets aggravated by thrust.

zzuf
8th Aug 2018, 13:04
If that be the case then why would the manufacturers say so? Not only that they further explain should it happen you may have to reduce thrust to reduce the AoA. Swept wing aircraft have a tendancy to pitch up at stall and that gets aggravated by thrust.

I understand and have experience with the pitching moments generated by underslung engines at low speed and high thrust.
But it seems to me that you are saying that there is a bunch of aircraft around that suffer severe, possibly uncontrollable pitch up at the stall, but are still certificated.
This is not true, make me wonder which manufacturers claim their aircraft are, essentially not fit for certification.
The Colgan accident investigation report makes no reference to uncontrollable pitch up that you alluded to.
The days seem to be long gone that wing designers are unable to develop a swept wing without significant low speed pitch up problems on transport aircraft.
I was introduced to the "blast out" of the stall technique by airline trainers over 40 years ago, I thought it a crock then and have never changed my mind. I rejected the technique as soon as I stepped out of the aircraft or simulator. The surprise is that it took the airline trainers so long to realize the nonsense of the procedure.

vilas
8th Aug 2018, 17:03
I think I didn't make it clear. What I'm saying is that pitch up caused by rapid thrust increase as it happens normally gets aggravated in stalled conditions because there is loss of pitch authority in stalled condition. Yes I agree Colgan was more of a result of mishandling than anything else. I had read it a long time ago.

aerodestination
8th Aug 2018, 17:18
I don't get it either. How I was trained during ME/IR was to recover without altitude loss when doing stalls in landing or take-off config. Clean stalls were normally trained based on 'minimum height loss'

it is wrong, I completely agree with you.

When I moved on from the MEP to MCC on the 737 I saw way to many fellow students entering secondary stalls when recovering. When you have height to spare, use it! On the 737 you will get a huge pitch/power couple especially at lower speeds. For stall recovery you actually have to keep forward pressure on the yoke to let the nose come up really slowly.

RetiredBA/BY
8th Aug 2018, 21:20
Minimum height loss recovery, of course, pretty obvious really.

SO what was wrong with what we taught in the RAF via CFS, where I was a standards QFI ( and later a Boeing TC)

Stall means we have exceeded the max cl angle and lift is deteriorating, probably because we have let IAS get too low and increased a of a to try and compensate,

SO: stick forward just enough to reduce angle of attack and restore lift, lower nose until buffet, stick shaker stops AND add FULL POWER. Gently rotate into climb.

And when the 737 pitches up on power,, control it to your advantage using forward stick, basic. ( And I have a few thousand hours, LHS on type plus a few thousand hours on bigger Boeing’s )

Recovery achieved, lminimum height loss.

Simples !

What were we we getting wrong?

Pugilistic Animus
8th Aug 2018, 21:31
That's why I changed it to Vp, Zzuff
Vilas that was how I was trained for approach to stall DP Davies style but I haven't flown commercially since 2005

zzuf
9th Aug 2018, 01:25
That's why I changed it to Vp, Zzuff

Sorry PA, my last dealing with Vp was concerning aquaplanning, I have no idea of the lastest definition, thanks.

eckhard
9th Aug 2018, 02:52
Minimum height loss recovery, of course, pretty obvious really.

SO what was wrong with what we taught in the RAF via CFS, where I was a standards QFI ( and later a Boeing TC)

Stall means we have exceeded the max cl angle and lift is deteriorating, probably because we have let IAS get too low and increased a of a to try and compensate,

SO: stick forward just enough to reduce angle of attack and restore lift, lower nose until buffet, stick shaker stops AND add FULL POWER. Gently rotate into climb.

And when the 737 pitches up on power,, control it to your advantage using forward stick, basic. ( And I have a few thousand hours, LHS on type plus a few thousand hours on bigger Boeing’s )

Recovery achieved, lminimum height loss.

Simples !

What were we we getting wrong?

The way you describe it - not much. BUT, that was not the way it was taught on my (UK CAA) 737 course in 1987, nor on my 747 course in 1997.

At low altitude, we were told to keep the AP in and add full power, period.
If manually flying, select and hold 5 degrees nose-up and add full power.
At high altitude, an attitude just below the horizon was selected and held, while adding full power.

No mention of ‘lower the nose until the buffet stops’, just select and hold the appropriate attitude. Made me feel very uncomfortable.

john_tullamarine
10th Aug 2018, 00:26
Side note - I've known zzuf for around 40 years - his background is very pertinent to this discussion and his counsel is well worth heeding.

Some of the problems with stall and stall recovery -

(a) the design standards have changed subtly over the years ie it is not a case of one-size-fits-all,

(b) if one wants to know something of the story for aircraft XYZ, one really needs to consult with the OEM FT group to find out just what they did. I have had reason to do so on a few occasions. Some of the responses have been somewhat different to what I had presumed to be the case.

(c) as for any design/certification thing, the first place to start is with the relevant set of design standards (cited in the TCDS), ACs relevant to those regs, and any details in the TCDS which might suggest any variations done between OEM and Regulator.

I recall an FT short course, years ago, where a very well-known instructor TP waxed lyrical on the subject for some time and opened a few eyes. Zzuf would recall that course at Cessnock in the early 90s. It is very important that the OEM's guidance material is followed for routine line operations as we out in the Industry don't necessarily know just what went on during the certification program. That is to say, do things rather differently to what the OEM test program did and one just might get an unpleasant surprise. Indeed, the instructor TP related a tale of (as I recall) a USAF TP trainee who thought it might be a good idea to push on well into the stall in a well-known light twin. Apparently the OEM's program didn't go anywhere near that situation. End result was an inverted spin which provided some thoughts for that evening's reflection over an ale or three for the student TP involved ...

Although it may not be precisely relevant to any particular Type/Model under discussion, it might be useful for folks to have a read of the current stall and recovery words in AC 25-7D to get a general idea of what the FAA thinks about the subject
https://www.faa.gov/regulations_policies/advisory_circulars/index.cfm/go/document.information/documentID/1033309

On another tack, historically, the ops and certification folks have not always sung to the same music and that has been a source of much of the confusion we see in the Industry .. an unfortunate fact of life which gets pushed into sharp relief from time to time when a major mishap occurs. One could think of the training changes post AF447.

Sometimes there be dragons lurking for those of us who might fancy ourselves more knowledgeable than we be.

eckhard
10th Aug 2018, 02:42
I agree with the general tone of the above but it does leave one a bit confused/doubtful when we are told, from one day to the next, “the way we have done it all these years is wrong. From now on, do it this way”.

Who is to say that this new officially-sanctioned method won’t be superseded in time? Perhaps it might be wiser to hang on to a few basic principles and keep in mind that the atmosphere and the aircraft haven’t read the manuals, nor are they concerned with any revisions to them.

Judd
10th Aug 2018, 03:26
At low altitude, we were told to keep the AP in and add full power, period.

I am curious to know why the accent on keeping the autopilot engaged if a stall occurs at low altitude? After all, if the AP fails to cope immediately full power is applied, the natural tendency is to wonder why, and the pilots attention drawn to the mode control indications. By then you have lost valuable seconds in which to manually reduce the angle of attack and then it may be too late. Maybe because manufacturer's are pragmatic and from reading accident reports have little faith in pilots basic manual flying ability nowadays?
Mind you, I can understand the manufacture's sentiment; especially as it is well known that manual flight is actively discouraged by many airlines. A colleague was talking to the chief test pilot involved with the certification of the Boeing 787 some years ago. He was told that Boeing designed the 787 around the premise that it would be flown by incompetent pilots around the world. Hence all the protections built into it.

vilas
10th Aug 2018, 07:53
What we are discussing here is what really the manufacturer's latest recommended procedure means in terms of execution. As far as Airbus is concerned there is a video on the subject also a few discussions in conferences. So there is nothing to add. Low level real stall not merely stall warning is a misfortune if happened environmentally and poor flying if happens without external factors. Some height will be lost. Unstalling first then controlled increase in required thrust not necessarily TOGA (it will be if gear and flaps are down) and recovery of flight path again smoothly avoiding secondary stall. Do it in a hurry and not recover at all, do it at leisure and have ground contact. Take your pick. In Airbus one is lucky, in normal law you can't stall and even in alternate law with reduced protection it is difficult to stall.

BizJetJock
10th Aug 2018, 10:26
My understanding is that the whole "power out of the stall with no height loss" idea came from the misguided assumption that if you recover at the warning you do not actually stall the aircraft. When I first moved on to jets after many years of advanced instruction and aerobatics, I was highly sceptical of this principle. Now it has sadly been proved to be invalid by several fatal accidents.
The fudamental flaws are that:
1. Environmental factors, e.g windshear, turbulence, icing can increase the angle of attack beyond the stall very rapidly. Even Airbus state that their aircraft can be stalled in normal law by this.
2. A crew that is sufficiently distracted, tired, or poor handlers to reach the warning are probably not sufficiently on top of the situation to fly a neat recovery from the warning and by trying to do so may actually induce the full stall (Colgan)
3. For many years high altitude stalls and the lack of thrust to fly out of an approach to stall were not even mentioned in training, resulting in no realisation that it was not possible to power out of the warning. (Pinnacle)
So the changes in recent years are entirely the training system realising that they have been teaching it wrong. The physics have not changed.

john_tullamarine
10th Aug 2018, 10:41
“the way we have done it all these years is wrong. From now on, do it this way”.

Afraid so, to a greater or lesser degree depending on the Type and the circumstances. A case of the left and right hands not always talking to each other and different perceived priorities between certification and operations. However you might like to look at things, if you do it differently to what was investigated by the OEM during the certification .. then don't be surprised if you get a surprise. Maybe the surprise will be nice .. then, again, maybe it won't be ? We need to be very cognizant of the raft of OWTs out there in the greater Industry. Hence the subsequent comment, above .. So the changes in recent years are entirely the training system realising that they have been teaching it wrong.

Perhaps it might be wiser to hang on to a few basic principles and keep in mind that the atmosphere and the aircraft haven’t read the manuals, nor are they concerned with any revisions to them.

Problem is if the basic principles don't match up with the particular certification standards applied to the particular aeroplane. Unfortunately, the atmosphere knows naught of the certification while the aircraft has read the certification stuff courtesy of the certification program. The problem is with us out there in the wider Industry who don't always know which particular book to read. See above OWTs.

What we are discussing here is what really the manufacturer's latest recommended procedure means in terms of execution

Providing that we make sure that we are reading the right bit from the OEM's wise words. We need to make sure that the particular aeroplane in which we have an interest is covered by the particular words. That is to say, one-size-doesn't-necessarily-fit-all. At the end of the day, I think it is a safe bet to suggest that the AFM and related stuff is the preferred guidance.

vilas
10th Aug 2018, 11:11
Environmental factors, e.g windshear, turbulence, icing can increase the angle of attack beyond the stall very rapidly. Even Airbus state that their aircraft can be stalled in normal law by this.Sure! The protection limits AoA to alpha max only to pilot input. but environmental factors can and when that happens the computer uses the flight controls to lower the AOA back to the permissible alpha max without pilot intervention which doesn't happen in nonprotected aircraft. So even here the protection helps. Even many airbus pilots have not given a thought to this.

Pugilistic Animus
10th Aug 2018, 15:17
Sorry PA, my last dealing with Vp was concerning aquaplanning, I have no idea of the lastest definition, thanks.

Vp is listed in Hurt's text as " The maneuver speed". I don't have Aerodynamics for Naval Aviators before me at this time but the Formula Vp= Vsn^.5 is listed in his book.

Zzuf would you please go into Vp and aquaplaning sounds very interesting...Although Vp is probably only for the Navy and may not exist in the FARs. The FARs may differ than in HHH's text with respect to definitions

john_tullamarine
11th Aug 2018, 02:30
Vo (operating manoeuvring speed) was introduced at A/L 23-45 in 1993 ref FAR Part 23 Sec. 23.1507 effective as of 09/07/1993 (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/0/2A0AA756267EFE8F85256687007232CC?OpenDocument)

AC 23-19A (https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_23-19A.pdf) has this to say -

48. What is the design maneuvering speed VA ?

a. The design maneuvering speed is a value chosen by the applicant. It may not be less than Vs√n and need not be greater than Vc, but it could be greater if the applicant chose the higher value. The loads resulting from full control surface deflections at VA are used to design the empennage and ailerons in Part 23, §§ 23.423, 23.441, and 23.455.

b. VA should not be interpreted as a speed that would permit the pilot unrestricted flight-control movement without exceeding airplane structural limits, nor should it be interpreted as a gust penetration speed. Only if VA= Vs √n will the airplane stall in a nose-up pitching maneuver at, or near, limit load factor. For airplanes where VA>VS√n, the pilot would have to check the maneuver; otherwise the airplane would exceed the limit load factor.

c. Amendment 23-45 added the operating maneuvering speed, VO, in § 23.1507. VO is established not greater than VS√n, and it is a speed where the airplane will stall in a nose-up pitching maneuver before exceeding the airplane structural limits.

zzuf
11th Aug 2018, 03:54
Vp is listed in Hurt's text as " The maneuver speed". I don't have Aerodynamics for Naval Aviators before me at this time but the Formula Vp= Vsn^.5 is listed in his book.

Zzuf would you please go into Vp and aquaplaning sounds very interesting...Although Vp is probably only for the Navy and may not exist in the FARs. The FARs may differ than in HHH's text with respect to definitions

It is just the standard aquaplaning speed calculated by:The hydroplaning speed, VP, may be estimated by the equation VP= 9√푃, where VP is the ground speed in knots and P is the tire pressure in lb/in2.

Pugilistic Animus
11th Aug 2018, 05:17
Thank you Zzuf also J_T for providing those links, really crystallize my understanding.

Pugilistic Animus
14th Aug 2018, 17:34
Sorry this is the wrong place but my PMs still don't work .. J_T I gave OS your email address via Facebook. Delete this post as necessary.

wiedehopf
14th Aug 2018, 18:03
Sorry this is the wrong place but my PMs still don't work .. J_T I gave OS your email address via Facebook. Delete this post as necessary.

Pugilistic Animus has exceeded their stored private messages quota and cannot accept further messages until they clear some space.


This is what i get when i send you something. You probably only deleted messages in your inbox folder but forgot to delete them in you "Sent" folder.

Below the red bar there is an option "Jump to folder". Use that to go to "Sent Items"
Empty that.

Cheers i hope :)