Take off with snow on wing

[Clandestino]

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:

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.

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.

[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?

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.

[up_down_n_out]

"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.

[AirRabbit]

Originally Posted by 8sugarsugar

Jets can power out of stalls and still climb when buffetting.

The Airborne Express DC-8 flight crew ... who were conducting a post-maintenance flight test on the night of December 22, 1996 in Narrows, Virginia, that included an approach-to-stall maneuver entered at 17,000 feet, repeatedly attempted to recover by simply “powering out” of the condition as you suggest ... might want to differ with that opinion, and probably would, except they are no longer with us to voice that difference, as they all died in the ensuing crash.

[Lightning Mate]

[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?

[stepwilk]

Air Florida had absolutely nothing to do with the crew fearing a pitch up.

[AirRabbit]

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?

I’m also confused about what Clandestino is saying. But, if I'm interpreting it correctly, I differ with his opinion that my post is an “alternate history,” providing a “verbally magic” rendition of the “real” history as contained in the NTSB report. I agree that everything in the NTSB report is based on fact but is not necessarily factual. Unfortunately, the analysis of those facts is, at best, incomplete – and in some cases, the facts presented are either dismissed or overlooked in the development of the final position … and in other instances, facts or statements from witnesses were omitted from the report.

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.

[AirRabbit]

Originally Posted by stepwilk

Air Florida had absolutely nothing to do with the crew fearing a pitch up.

…and you absolutely know this because …??

[AirRabbit]

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?

I have said from day one that had the flight crew pushed the throttles to the firewall at brake release … and initiated the rotation at the computed rotation speed – exactly the same thing would have occurred … except – as you note – because of the aircraft attitude, the downward thrust vector may have (no guarantee … but may have) allowed the airplane to miss hitting the bridge and the 4 lives lost on that bridge would likely have not been lost. However, the location of the eventual impact (and there would have been an impact) would more likely have been closer to the middle of the Potomac River, although more upstream, making rescue of those who were rescued a lot more problematic. Who is to say what would have been the most advantageous decision? What I suspect is that throughout the entire 28 seconds they were airborne, they were trying to figure out what to do to fly the airplane – heck, here we are some 30 years (!) after the fact … and I suspect there still isn’t a consensus.

[Clandestino]

Originally Posted by lederhosen

Clandestino I am seriously confused about what you are trying to say

That's because you have never met captain Dudley or anyone of his ilk... smooth-talking, very convincing and stupefyingly ignorant if you happen to know a bit about issue being discussed.

Originally Posted by lederhosen

Are you saying AirRabbit does not understand aerodynamics and is telling old wive's tales?

How in the world could I possibly know whether AirRabbit understands aerodynamics? 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 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.

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

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?

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.

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

...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.

They could have aborted. The B727 you are so concerned about would have gone around. Happens every day. Very seldom makes headlines.

I suspect there still isn’t a consensus.

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.

[lederhosen]

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!

[Checkboard]

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:

F-4 Phantom Stall & Crash - YouTube

(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.

[lomapaseo]

Clandestiono

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,

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

[stepwilk]

…and you absolutely know this because …??

Because I read the NTSB report.

[AirRabbit]

Originally Posted by stepwilk

Because I read the NTSB report.

My appologies ... I must have missed that information in the report ... do you have a page reference?

[AirRabbit]

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.

Of course it is true that the CVR contained “evidence” of what you refer to as the “derision” of de-icing procedures maintained by the flight crew. My contention is that such conversations were more routine than scarce among aviators at that time … not due to the scorn felt, but, to the contrary, due to an attempt to present an attitude of fearlessness and “macho-ism” that airline pilots were historically supposed to exhibit. However, when “push-came-to-shove,” I think it was rather routine to find everyone eager to participate in whatever was the “science of the day.” It’s just that the science of that day is not the science of today. The conversation between the two flight crew members wasn’t omitted from my comments in a “convenient” attempt to hide what was happening, but was omitted because it was irrelevant to the points I was attempting to make.

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.

I guess you are one of those guys who read the specific words and responds only to those words, not bothering with what one can glean from those words. OK, I’ll go with that approach. If it makes a difference, I do understand the difference between “pitch” and “AoA” and I’m fully aware of the fact that an airplane can be stalled in any position relative to any particular reference. I’ll accept the criticism for not being more specific with respect to the differentiation between“pitch” and “AoA,” I just thought it might be easier to understand my position by referring to the attitude of the airplane, (“pitch”) in that no one really knows the specific AoA that was achieved … and with a lack of information as to the actual flight path of the airplane, even a good guess is not terribly likely.

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.

I guess I didn’t make myself perfectly clear. Obviously something caused the pitch attitude (read that as AoA if you prefer) that was achieved. That attitude was due to either the flight crew placement of flight controls or some other aerodynamic force. Given the concession that it was not likely the flight crew that pulled back on the controls to the extent that would result in the pitch attitude (AoA) eventually achieved – it must have been some aerodynamic issue. Also, one of the contentions was that the reason for the crash was the fact that the flight crew used less than full power. Of course, they used less than full power – and that was an error – but it did NOT cause the accident. Under normal circumstances (as you correctly point out) the airplane would have flown on two engines producing 75% of maximum thrust of each engine. The point I was driving to is the fact that there was another reason that the crash occurred. It was the ice that was present on the wings … but … (and this is why I made such a point about the airplane preceding and the airplane following the accident airplane) all 3 airplanes were deiced at about the same time … all 3 airplanes were exposed to the same elements for about the same time span … yet it was only the middle airplane that crashed. What was different about this airplane? The difference was the deicing procedure used on this airplane – only this airplane. This is the reason I went into the detail that I did regarding the equipment that was used to “de-ice” the airplane. The aerodynamic force that was responsible for the resulting attitude (AoA) was a result of the ground crew de-icing the airplane with hot water – and then going back to “over-spray” the entire airplane with that same hot water. The reason the PT2 probes were blocked (likely with ice) is due to the fact that the de-icing crew sprayed hot water all over the engine intakes and then went back and lightly misted those intakes with that same hot water. It is my contention that this caused a very thin, transparent film of water on the lifting surfaces … which then froze into clear ice – probably barely detectable and certainly not able to be seen from the cockpit – probably not able to be seen unless very close to the contaminated surface – if then. Yet, the deformation it produced was significant enough to cause an unwanted and unexpected change in the aerodynamics affecting the flight of that airplane. I also went into some detail about asymmetrical lift on the wings – both laterally and longitudinally. It was this longitudinal differential lift that caused the unwanted and unexpected pitch-up, and did so to an unwanted and unexpected attitude – placing the airplane in an unwanted and unexpected AoA from which recovery was not possible under the circumstances.

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.

Thanks for that.

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!

We can discuss whether or not the change in lift characteristics of the accident airplane was due to leading edge contamination or wing surface contamination if you care to … but I’m going by Boeing’s own reports of the B-737 being susceptible to “pitch-up, roll-off tendencies when exposed to areas of freezing precipitation encountered in flight during the original flight testing of the airplane.” As you would recognize, ice buildup due to inflight encounters does not occur on the wing’s top surfaces as much as it does on the wing leading edge … but, deicing a wing with hot water is as likely to deform the wing surfaces as much as the wing leading edges … and, as I said, this particular discussion may be appropriate at a later time. The fact is that the wing was deformed – not by the falling precipitation (recall the other two airplanes in line … one preceding and one following the accident airplane – all of which were exposed to the same falling precip), but rather by the “de-icing” procedures completed at the gate.

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.

Of course they could have aborted, and I’m acutely aware of the number of rejected or aborted takeoffs that occur – and I’m also aware that “go-arounds” are quite common. However, these kinds of activities when occurring together are not routine, particularly when the weather conditions are as poor as they were on this fateful day. If the B-737 had aborted at the first question raised by the F/O and had that information been relayed immediately to the tower and the approaching B-727 crew had been listening intently, understood the meaning, and executed a missed approach – there is a chance that there would have been no problem. But given that the visibility was “el stinko” (tower quoted the runway 36 visual range to be 2800 feet with the sky completely obscured) AND the fact that the B-727 was very, very close behind the B-737 (some witnesses said both airplanes were ON the runway at the SAME TIME!) it is highly unlikely that everything would have worked out in a pristine manner – and, while it may not be a universal suspicion, the suspicion is certainly held by more than a few aviation professionals, that had that B-737 aborted on the runway, it would likely have been hit by the landing B-727, either on the ground or during the attempt to go around … and that is what I think was on the mind of the Captain of the B-737.

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.

Come on Clandestino … I’m trying to go out of my way to keep from insulting you … don’t you think that a little more restraint might be in order? I was responding to “8sugarsugar” when he asked if I would add power or not add power were I in the same situation. Because of the notoriety of this particular accident … because it is one of the few accidents ever to occur in the US capital … because every news outlet on the planet had consistent news coverage of this event for weeks afterward … I would be shocked to see that more than just a couple of people could ever find a consensus on more than a few areas with respect to this accident. It may be proven wrong in some circles, but as of now, at least I think I can read the English language as well as most everyone in this country – and I think I am reasonably familiar with aviation and how it works. I think I’m also familiar with accident investigation and as I said at the outset of the posts I made yesterday, my motivations have NOT included an intent to impugn the fine reputation or the integrity of the NTSB or of the dedicated and professional employees at the Safety Board; rather my intent was, as I stated … a continuing effort to describe the actions of the flight crew from a slightly different perspective while providing what I believe to be clarifying information regarding the cause of the accident to the best I am able. Now, if you tell me that I’m not authorized to post my opinions on something – that’s a completely different issue. As anyone on this or any other forum is always free to do … you are free to disagree and argue with my opinions if you desire – but they ARE my opinions.

[stepwilk]

My appologies ... I must have missed that information in the report ... do you have a page reference?

I'm not gonna do your work for you.

[AirRabbit]

Yeah ... that's what I thought.

[Machinbird]

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.