Why did they want us to maintain altitude
Vp= Vs×n^0.5 where n is the limit load
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.
Last edited by zzuf; 8th Aug 2018 at 05:47.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,404
Likes: 0
Received 0 Likes
on
0 Posts
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
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.
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.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,404
Likes: 0
Received 0 Likes
on
0 Posts
Most (probably all) certificated aircraft do not pitch up uncontrollably when stalled.
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.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,404
Likes: 0
Received 0 Likes
on
0 Posts
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.
Join Date: Sep 2015
Location: North
Posts: 65
Likes: 0
Received 0 Likes
on
0 Posts
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.
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.
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?
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?
Last edited by RetiredBA/BY; 8th Aug 2018 at 20:41.
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
Vilas that was how I was trained for approach to stall DP Davies style but I haven't flown commercially since 2005
Last edited by Pugilistic Animus; 8th Aug 2018 at 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?
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?
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.
Moderator
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_poli...mentID/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.
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_poli...mentID/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.
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.
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.
At low altitude, we were told to keep the AP in and add full power, period.
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.
Last edited by Judd; 10th Aug 2018 at 02:38.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,404
Likes: 0
Received 0 Likes
on
0 Posts
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.
Join Date: Oct 2003
Location: If this is Tuesday, it must be?
Posts: 651
Likes: 0
Received 0 Likes
on
0 Posts
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.
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.
Last edited by BizJetJock; 10th Aug 2018 at 09:47. Reason: Spelling
Moderator
“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.
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.
Join Date: Jun 2007
Location: Wanderlust
Posts: 3,404
Likes: 0
Received 0 Likes
on
0 Posts
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.