Take off with snow on wing
Well done AirRabbit! Your interpretation of Air Florida 90 catastrophe reminds me of the theories put forward by the legendary captain Dudley; inoffensive and convincing, inter alia. Capt Gann would describe it as verbal magic.
Nevertheless, for anyone interested more in history than alternate history, NTSB report provides better value-for-time-spent-reading. Especially CVR transcript.
Back to topic: issue with pilots not understanding where lies the problem with taking off with contaminated wings was well understood by a certain gentleman of yesteryear:
Replace "mechanics" with "aerodynamics and statistics" and there you have it.
Here comes winter refresher; a bit of talk what is new, a lot of talk of what we should all already know, compulsory video of Dryden or Palm ninety in front of mixed audience, from grey-haired veterans to greenhorn effohs. Some young ones learnt their aerodynamics by rote and forgot most of it after passing the exam. All they hear is "Blah, blah, blah... you will die if you don't de-ice.... blah, blah, blah". Then one day they get paired with captain of similar background but earlier "joined" date who is not concerned with a bit of snow on wings as it will all blow off and anyway and skipping the de-icing will save company time & money. Our young hero is a bit scared as he still remembers the educational videos but while he weighs whether to believe ground instructor of couple of weeks ago or the capt sitting with him here and now, vee one has passed. Then rotation. Then "POSITIVE RATE" and aeroplane flies. And flies. Now there is no doubt who was right, is it? So the "de-icing gives false feeling of security" and "it satisfies the feds" attitude towards ground de-icing continues its spread among the pilots. One day our young hero will be captain. Experienced captain.
If you're not much into flying: point is that very little percentage of aeroplanes that take-off with contaminated wings end up as tangled wreckage near the runway's end; any contamination will eat up into stall margin but if that margin is not completely taken away, aeroplane will fly. However, even that little percentage is both easily manageable and unacceptably high in public air transport. Pilots failing to get to grips with basic aerodynamics are main source of old-wives-tales, refuting the standard op procedures. Not just on cold wx ops.
Nevertheless, for anyone interested more in history than alternate history, NTSB report provides better value-for-time-spent-reading. Especially CVR transcript.
Back to topic: issue with pilots not understanding where lies the problem with taking off with contaminated wings was well understood by a certain gentleman of yesteryear:
Originally Posted by "Rio de Janeiro Pratt & Whitney representative, as quoted by EK Gann
The problem with most pilots is that you are spoiled. And lazy. You have never taken the trouble to learn mechanics properly.
Here comes winter refresher; a bit of talk what is new, a lot of talk of what we should all already know, compulsory video of Dryden or Palm ninety in front of mixed audience, from grey-haired veterans to greenhorn effohs. Some young ones learnt their aerodynamics by rote and forgot most of it after passing the exam. All they hear is "Blah, blah, blah... you will die if you don't de-ice.... blah, blah, blah". Then one day they get paired with captain of similar background but earlier "joined" date who is not concerned with a bit of snow on wings as it will all blow off and anyway and skipping the de-icing will save company time & money. Our young hero is a bit scared as he still remembers the educational videos but while he weighs whether to believe ground instructor of couple of weeks ago or the capt sitting with him here and now, vee one has passed. Then rotation. Then "POSITIVE RATE" and aeroplane flies. And flies. Now there is no doubt who was right, is it? So the "de-icing gives false feeling of security" and "it satisfies the feds" attitude towards ground de-icing continues its spread among the pilots. One day our young hero will be captain. Experienced captain.
If you're not much into flying: point is that very little percentage of aeroplanes that take-off with contaminated wings end up as tangled wreckage near the runway's end; any contamination will eat up into stall margin but if that margin is not completely taken away, aeroplane will fly. However, even that little percentage is both easily manageable and unacceptably high in public air transport. Pilots failing to get to grips with basic aerodynamics are main source of old-wives-tales, refuting the standard op procedures. Not just on cold wx ops.
Clandestino I am seriously confused about what you are trying to say and what it has to do with the original thread. Are you saying AirRabbit does not understand aerodynamics and is telling old wive's tales?
Flying jets is a team activity, both pilots are involved. I can certainly remember when I was a co-pilot telling a captain at the holding point after a heavy snow shower that we needed to de-ice and us going back and doing so. I expect and encourage my co-pilots to do the same.
Flying jets is a team activity, both pilots are involved. I can certainly remember when I was a co-pilot telling a captain at the holding point after a heavy snow shower that we needed to de-ice and us going back and doing so. I expect and encourage my co-pilots to do the same.
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"Jets can power out of stalls and still climb when buffetting"
Yea right, pity AF447 went straight down, and they were saying exactly the same as you, right to the end.
Sounds like utter b..ll x to me, especially in a deep stall.
Yea right, pity AF447 went straight down, and they were saying exactly the same as you, right to the end.
Sounds like utter b..ll x to me, especially in a deep stall.
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Originally Posted by 8sugarsugar
Jets can power out of stalls and still climb when buffetting.
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I guess what I was trying to say, if your two options are in Air Florida
1. not advancing power levers in fear of pitch up moment and crashing anyway
2. advancing power levers, accepting increased pitch up moment and praying to god you get at least 500 ft.
At least with #2, you hit terra firma softer and save some lives.
what would you do?
1. not advancing power levers in fear of pitch up moment and crashing anyway
2. advancing power levers, accepting increased pitch up moment and praying to god you get at least 500 ft.
At least with #2, you hit terra firma softer and save some lives.
what would you do?
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Originally Posted by lederhosen
Clandestino I am seriously confused about what you are trying to say and what it has to do with the original thread. Are you saying AirRabbit does not understand aerodynamics and is telling old wive's tales?
Just one example (and there are others): in the report, on page 9, there is “grainy” photo of the accident airplane at the gate prior to departure. This photo was reportedly taken between 15:19 and 15:24, by a passenger on an arriving flight that was holding for gate space near the accident airplane. The photo shows snow accumulated on the top and right side of the fuselage. This photo was used to present the case that the airplane had accumulated snow or ice prior to departing the gate, further condemning the flight crew for taking off under such conditions. However, in the referenced photo, the forward cargo door (below the windows) is clearly open and baggage carts and a catering van are positioned adjacent to that open cargo door. Statements acquired of the crew that actually deiced the airplane indicated that they accomplished the deicing after all baggage had been loaded and the airplane had been catered and that after the deicing, no additional baggage was loaded and no additional catering was completed. These statements did not make it into the report. Why? It’s only my opinion, but, if someone wanted to provide evidence that the airplane was “covered with ice and snow,” the photo certainly validates this truth. However, if the photo was taken prior to the deicing process – that piece of evidence no longer contains valid information relative to the condition of the airplane when it left the gate, and therefore becomes meaningless. The timing of the photo was an estimate provided to the investigators by the passenger who took the photo from the window of a flight inbound to the gate.
Anyone reading the CVR transcript can see that it starts at 15:30 – meaning that 15:30 would be after the passengers and crew had boarded the airplane; after all the all the commotion that accompanies boarding the airplane; after the flight crew had competed their cockpit checks; after the engines had been started the first time; after the first aborted attempt to push back; after the second aborted attempt to push back; after the engines had been shut down; and after the call for another, larger tug to push back. In fact, at 15:34 the Captain is noted as saying “Here comes the chain tractor” (meaning the tug with chains on the tires to facilitate the push-back process). Again, look at the photo. Could the baggage have been loaded, the catering completed, and then the deicing/anti-icing process completed on the entire airplane (whether or not the mixture was adequate to do the job intended), for all of the above to have taken place, including the accumulation of ice and snow indicated in the photo – and have that all accomplished in 6 - 12 minutes? Give me a break!
Conclusion: The photo provided visual confirmation of the facts only if interpreted in one way. The statements provided by the deicing crew would have conflicted with this interpretation of facts. However, by relying on this photo and disregarding the statements made by the deicing crew, one would have to conclude that what is seen in the photo is not the baggage door open and there are no baggage carts or a catering vehicle at the airplane visible in the photo; OR that catering and baggage loading occurred after the deicing process was completed. Also, one would have to presume that the photo was taken sufficiently long enough after the deicing was completed to have had that kind of accumulation occur, and that all of the above cited events would have had to have taken place in the 6 to 12 minutes between when the photo was taken and the CVR transcript beginning. Does that make sense to you? Not in my book! The only logical conclusion that can be made is that the photo was, indeed, taken by a passenger on an arriving flight – but it was taken much earlier than described – well before the deicing / anti-icing process was conducted. So why include it? I think the answer is obvious.
Last edited by AirRabbit; 18th Apr 2012 at 16:04.
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Originally Posted by 8sugarsugar
I guess what I was trying to say, if your two options are in Air Florida
1. not advancing power levers in fear of pitch up moment and crashing anyway
2. advancing power levers, accepting increased pitch up moment and praying to god you get at least 500 ft.
At least with #2, you hit terra firma softer and save some lives.
what would you do?
1. not advancing power levers in fear of pitch up moment and crashing anyway
2. advancing power levers, accepting increased pitch up moment and praying to god you get at least 500 ft.
At least with #2, you hit terra firma softer and save some lives.
what would you do?
Originally Posted by lederhosen
Clandestino I am seriously confused about what you are trying to say
Originally Posted by lederhosen
Are you saying AirRabbit does not understand aerodynamics and is telling old wive's tales?
Originally Posted by AirRabbit
Opinions differ as to what pitch angle would have been required to get into the stall buffet – but they range from 22 to 24 degrees of pitch.
Originally Posted by AirRabbit
the airplane should have been able to fly on one engine at 100% power
Originally Posted by AirRabbit
In that any additional weight due to ice accretion seems not to be the answer, why did the airplane stall at 24 – 30 knots above stalling speed?
Originally Posted by AirRabbit
In my opinion it was because of the pitch attitude of the airplane.
Originally Posted by AirRabbit
the outboard portion of the wings sufficiently deformed by leading edge ice accretion
Originally Posted by AirRabbit
I believe that once this crew pushed the throttles forward with the intent to takeoff, they were doomed.
I suspect there still isn’t a consensus.
Don't trust NTSB blindly but at least make an effort to understand what they are saying. You'll find their analyses correct far more often than not.
Thank you Clandestino for taking the time to clarify what you meant. But I cannot see what we are arguing about. AirRabbit has suggested that the AirFlorida aircraft pitched up sharply after takeoff. One thing we can all agree on is that it was snowing heavily as apparently with the Aeroflot aircraft getting back to the original thread. There is no way of knowing how an aircraft covered in contaminant will behave. Ice and snow on the horizontal stabilizer for instance could also significantly change the flying characteristics. It is the luck of the draw if you get away with it. The message is don't do it. Even if you do not crash you can expect to be confronted with the evidence on youtube!
AirRabbit, interesting take on the Air Florida case.
All wings are unstable in pitch, the centre of lift moves forward as the aircraft pitches up. If it moves too far forward on a less stable wing, especially one with a wide chord, it can exceed the pitch authority of the elevator:
(Perhaps especially if a close taxi to an aircraft in front melts some of the ice on the inboard wing and not the outboard sections?)
... it would be interesting to see some research on the amount of pitch up moment a 737 could develop under those conditions for me to be convinced, though. I think it's certainly worth that research.
All wings are unstable in pitch, the centre of lift moves forward as the aircraft pitches up. If it moves too far forward on a less stable wing, especially one with a wide chord, it can exceed the pitch authority of the elevator:
(Perhaps especially if a close taxi to an aircraft in front melts some of the ice on the inboard wing and not the outboard sections?)
... it would be interesting to see some research on the amount of pitch up moment a 737 could develop under those conditions for me to be convinced, though. I think it's certainly worth that research.
Clandestiono
By the time of Air Florida it was common practce for the CVR analysis group to consider water fall chart analysis of the CVR traces to track the N2 frequency signal from each engine to assess actual engine power vs time.
It's easy for some to suggest that wing contamination might have played a part (after all the evidence melts immediately after a crash).
However the validated contributions are covered in the NTSB report hence the recommendations regarding engine power set "check'.
The Forum thread we are burried within is an equally important opportunity thread to discuss wing ice as a prime consideration on its own without mixing it up in a controversial message about Air Florida in the Potomac
First issue with QH90 was very primitive (but legal at the time) FDR, which did not record attitude or power. In AirRabbit's alternative view on the accident, holes left by primitive recording equipment are filled by conjecture,
It's easy for some to suggest that wing contamination might have played a part (after all the evidence melts immediately after a crash).
However the validated contributions are covered in the NTSB report hence the recommendations regarding engine power set "check'.
The Forum thread we are burried within is an equally important opportunity thread to discuss wing ice as a prime consideration on its own without mixing it up in a controversial message about Air Florida in the Potomac
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Originally Posted by Clandestino
I don't know (and don't care either) who AirRabbit is, all I have and have referred to is his alternative analysis of QH90 accident. Some of the points he made are so out of sync with the real world that it would be tragic if real pilots hold them to be true. First issue with QH90 was very primitive (but legal at the time) FDR, which did not record attitude or power. In AirRabbit's alternative view on the accident, holes left by primitive recording equipment are filled by conjecture, yet that CVR recorded both pilots clearly pouring their derision on the de-icing procedures during taxi-out is conveniently omitted.
Originally Posted by Clandestino
Such a blatant mix-up of pitch and AoA I find hard to comprehend but then I was the lucky one, flying unstalled at +90° pitch and being stalled at -60° before my TT went into three digits.
Originally Posted by AirRabbit
the airplane should have been able to fly on one engine at 100% power
Originally Posted by Clandestino
With clean wing, it would. NTSB is pretty clear on that.
Originally Posted by AirRabbit
In that any additional weight due to ice accretion seems not to be the answer, why did the airplane stall at 24 – 30 knots above stalling speed?
Originally Posted by Clandestino
Weight of the ice being significant factor is myth dispelled during first hour in winter ops groundschool. so far so good.
Originally Posted by AirRabbit
In my opinion it was because of the pitch attitude of the airplane.
Originally Posted by Clandestino
Wrong!!!! Issue is not pitch but lesser Cl max, higher Cd and lesser AoAcrit which is not due to...
Originally Posted by AirRabbit
the outboard portion of the wings sufficiently deformed by leading edge ice accretion
Originally Posted by Clandestino
...but rather upper wing skin contaminated by ice! Top of the wings is the most critical surface for contamination on any aeroplane!
Originally Posted by AirRabbit
I believe that once this crew pushed the throttles forward with the intent to takeoff, they were doomed.
Originally Posted by Clandestino
They could have aborted. The B727 you are so concerned about would have gone around. Happens every day. Very seldom makes headlines.
Originally Posted by AirRabbit
I suspect there still isn’t a consensus.
Originally Posted by Clandestino
How do you make consensus with someone obviously unable to understand the accident report? Why would there have to be consensus with such a personae?
Don't trust NTSB blindly but at least make an effort to understand what they are saying. You'll find their analyses correct far more often than not.
Don't trust NTSB blindly but at least make an effort to understand what they are saying. You'll find their analyses correct far more often than not.
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Checkboard,
The video of the Phantom pitching up was taken of an early test hop at the McDonnell factory. They apparently did not have any stabilator control at all and it was stuck full nose up.
The video of the Phantom pitching up was taken of an early test hop at the McDonnell factory. They apparently did not have any stabilator control at all and it was stuck full nose up.