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Old 29th Apr 2012, 00:44   #401 (permalink)
 
Join Date: Apr 2005
Location: Southeast USA
Posts: 748
Quote:
Originally Posted by PukinDog
1. From the report: "The Federal Aviation Regulations are very specific, requiring that "no person may take off an aircraft when frost snow or ice is adhering to the wings, control surfaces, or propellers of the aircraft." The crew knew they had a contaminated wing with frozen precip adhering, yet they took-off it anyway.
Once again – I’ll take the time to point out that both the regulation and persons reading the regulation continually pointed to the word “adhering” with an impression of its meaning that obviously differs from yours. Clearly, you are one of those persons who believe that if snow is on a surface, that fact alone is sufficient verification for you that the snow is “adhering” – but even then you seem to have “widened” the door to allow some other possibilities to sneak through. In one of your earlier posts you said …
Quote:
If its not wet and glossy but turned opaque, and especially if there's snow present on the fluid surface, the solution has lost the ability to melt frozen precip and absorb/suspend/depress the freezing point of the water. Unless other procedures have been approved in the Ops Specs, the general rule for U.S. air carriers (121.629) if HOT has been exceeded there must be pre-takeoff contamination check accomplished within 5 mins before T/O, and it must be done from outside the aircraft.
While most the above quote is accurate – you haven’t provided any information as to when this language first appeared in the section you cite … and, in a difference from your quote, the actual rule language describes that a takeoff may be made if the maximum holdover time does not exceed that found “in the certificate holder's holdover timetable” – suggesting quite strongly that differing time periods are not only acceptable, but that they do exist – even in the current environment – which, as you know, is substantially more knowledgeable in these areas than what existed 30 years ago.

I’ll also point to your description of some snow where you certainly imply it be allowed on an airplane’s surface…
Quote:
In any case, no matter how you're trying to parse it, if it's not a dry, feathering snow readily sliding off a cold-soaked wing but is accumulating on it instead, then it must adhering somewhere...
I read that as saying “…if it IS a dry, feathering snow that is readily sliding off a cold-soaked wing … then THAT snow would be allowed to accumulate because it would not be “adhering”… is that what you meant?

Quote:
…accumulated on de/anti-ice fluid, the fluid has failed (and) this "accumulation" of snow … doesn't meet the criteria "free of" (therefore it is considered) contaminated.
So, by your description, my question would be … just exactly how long after a snow flake falls on a surface that has had a coating of anti-ice fluid applied would that snow flake be rendered to a state of a harmless fluid? Equally important, does the rate of snow fall have any impact on this process? I’m just wondering, under your conception of the process, how it is that an airplane is allowed to takeoff during a falling snow?

Quote:
Originally Posted by PukinDog
2. The Air Florida company Ops Manual mirrored that same Reg, but with relief granted for dry snow if the Captain and person releasing the aircraft agreed conditions precluded adhering. That relief was never sought, and the mod-heavy wet snowy conditions weren't of that nature anyway. So with regards to "clean wing"/contamination", there's no question the crew didn't follow their own Ops Manual either as it existed in 1982. Ignorance of his own Manual?..or disregard for it.

And

3. Inspection after de-icing. From the Report: "Neither the Air Florida maintenance representative who should have been responsible for proper accomplishment of the deicing/anti-icing operation, nor the captain of Flight 90, who was responsible for assuring that the aircraft was free from snow or ice at dispatch, verified that the aircraft was free of snow or ice contamination before pushback. Ignorance of his own Manual? or disregard for it.
You “say” that relief was never sought … you say that no one verified that the aircraft was free from snow or ice … obviously you are not aware that it was the Captain (in coordination with the company maintenance supervisor on duty ... to some degree) who was responsible for “releasing” the aircraft? According to the Accident Report (page 3) “…the same American Airlines mechanic that had inspected both engine intakes upon completion of the deicing/anti-icing operation performed another general examination of both engines. He stated that he saw no ice or snow at that time. Air Florida and American Airlines Personnel standing near the aircraft … stated that they did not see any water, slush, snow, or ice on the wings.”

Quote:
Originally Posted by PukinDog
4. Use of reversers. The Air Florida Ops Manual at that time also included Bulletins warning of possible clear ice formation on leading edge devices while using reversers on the ground with snow present. There were also a series of Bulletins and avisories regarding rotation/pitch and roll issues with contamination on the leading edges, and recommended procedures for takeoffs into icing conditions or where contamination may be present. The Captain used the reversers for 30 to 90 seconds at the gate, after de-icing. Ignorance of his own Manual? or disregard for it.
And you admonish me for “cherrypicking?” Come on, sir … let’s be fair. While it is correct that the Ops Manuals very likely discussed the kinds of things you say – did you possibly check to see where in the manual such statements were made. For example, in discussing the arrival of a flight into a terminal area during snow conditions, that same manual said the following – also quoted from the Accident Report:
Quote:
A buildup of ice on the leading edge devices may occur during ground operations involving use of reversers in light snow conditions. Snow is melted by the deflected engine gases and may refreeze as clear_ ice upon contact with cold leading edge devices. This buildup, which is difficult to see, occurs in temperature conditions at or moderately below freezing. Crosswind conditions can cause the ice buildup to be asymmetrical, resulting in a tendency to roll at higher angles of attack during subsequent takeoffs.
I’m sure you know of the problems that may be caused by landing on a snow-covered runway, stopping with the use of up to and possibly including full reverse thrust (which as you know throws anything on the ground – like water or snow – forward of the airplane and likely impinges on that airplane as it moves forward. Additionally, taxiing in to the gate after landing, a flight crew may well use reverse thrust to assist braking effectiveness. The quote you provided is almost always read in the context of a “between approach – through the landing – taxi in – and parking sequence.” This why the quote you provided clearly describes problems that may be encountered with “subsequent takeoffs.”

In your incessant arguments that this situation was complicated by a couple of bafoons to knew little and cared less. You continue to cite what you believe was a deliberate maneuvering of their aircraft to be “deiced” by the jet blast of a preceding airplane. I hope to goodness that you are never recorded, in a moment of utter frustration, uttering a hyperbole (such as “I’d sell my oldest child for a parking place!) because someone with your penchant for not understanding the potential uses of such parts of speech in, at least the Americanized version of, the English language is going to think you more than just a bit nuts – when those of us here have come to recognize that you are certainly not nuts.

While we are looking more carefully at the contents of that company’s Ops Manual, it might interest you know that the following was contained in that manual as well – as prescribed by the airplane manufacturer (again, from the Accident Report, page 37)
Quote:
Section 3A-7, page 2, of the August 20, 1973, issue of the B-737 Operations Manual, Supplementary Procedures, Ice and Rain Protection, “Wing Anti-ice,” states: There are two methods recommended for operating the anti-icing. The primary method is to use it as a deicer, by allowing the ice to accumulate before turning it on. This procedure will provide the cleanest airfoil surface, the least possible runback ice formation, and the least thrust and fuel penalty. Normally, it will not be necessary to shed ice periodically unless extended flight through icing conditions is necessary (holding). Ice less than 3 inches thick will have little effect on airplane handling, therefore, the ice accumulation may be allowed until the icing condition has been passed. The secondary method is to turn the wing anti-ice switch on when wing icing is possible and use the system as an anti-icer.
I’ll just leave that manual paragraph alone for anyone’s contemplation.

You can – and you have – criticized these crewmembers quite heavily – they and their families paid – quite heavily for any mistakes they may have made – certainly relying on what and how they were trained, relying on a competent ground crew to deice and anti-ice their plane – doing what everyone else that day appeared to be doing – wasn’t all a mistake.

Do I have an agenda? You bet. And I thought I made that perfectly clear in my first post on this thread. The reason I interjected my original comment into this thread was not to start an unwanted argument about what should have been done or what the flight crew should have known and did know. My original comment was to correct what I saw as an incorrect impression that it was a the low engine takeoff power that caused the accident. The NTSB officially, and at least one NTSB participant (quoted by one of the posters here) collectively agreed that the engine power setting did not cause that accident. The NTSB reached the conclusions they reached. Some of us in the aviation world disagree with those conclusions … welcome to the world of individuality. There will inevitably be doubts and incomplete knowledge in almost any accident scenario … and I sincerely believe THAT is the primary reason that the NTSB does not publish “Accident Causes.” They publish “Probable Causes” of accidents. Do I expect the conclusions reached in this accident to be changed? …not hardly! Does that mean I agree with all that was said in that report? …again, not hardly!

One thing I hope I am never caught doing is besmirching the reputation of fellow aviators that have experienced unfortunate turns of events. I’ll leave the allegations of “lack of awareness;” of “providing Laissez faire ‘non-answers’ to questions;” and the like to others. I would hope that any professional on this or any other forum, or in any other exchange of philosophy or ideas or questions, will examine all there is to examine – including the concerns, opinions, and beliefs of others – not to the exclusion of facts, but perhaps to bring slightly differing highlights to those facts … to better understand and appreciate what happened …and then do all they can to learn from what those actions have provided.
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Old 29th Apr 2012, 00:55   #402 (permalink)
 
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Quote:
Originally Posted by Clandestino
They were not idiots in the medical sense but that they were ignoramuses is beyond doubt.

How could pilots be so ignorant to perform such a hazardous act ? IMHO, first: they have to be ignorant of aerodynamics and meteorology, second: gaps in their knowledge have to be filled by someone delivering his dead wrong message with great detail, patience and perseverance. Higher he be on the airline totem pole, it's easier for him to get the messages such as: "it will be blown off anyway" or "de-icing is useless but satisfies the authorities" across.

Unrealistic theory? Have a look at the last couple of pages on this thread.
I'm going to side-step the opportunity to respond in "like manner" ... as I've made the points that I believe are relevant and I'm quite comfortable in having done so. It's up to each reader to determine the level of competence and accuracy they wish to attach to each. I wish you all a comfortable coming week!
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Old 29th Apr 2012, 05:49   #403 (permalink)
 
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Thumbs up @AirRabbit

I have carefully read your contributions and your analysis of the Air Florida crash and I took the time to read (parts of) the NTSB report. Your knowledge about this case is impressive and so is the polite language that you use while telling your side of the story. Not that it matters, but just for the record: you have convinced me. What you are saying is very plausible indeed. I would however respectfully like to suggest you to stop arguing with some of the members on this topic, simply because it's a waste of time. You said what you needed to say and did it very well.
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Old 29th Apr 2012, 18:50   #404 (permalink)
 
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Quote:
Originally Posted by sabenaboy
I ... respectfully ... suggest you stop arguing with some of the members on this topic, simply because it's a waste of time. You said what you needed to say and did it very well.
Thank you for the very kind remarks ... and for the excellent advice ... which I had previously considered doing ... but will now adopt.
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Old 29th Apr 2012, 19:38   #405 (permalink)
 
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Air Rabbit

For my two cents.. (or kopeks)

A well reasoned discussion is always welcome. I appreciated your comments.
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Old 30th Apr 2012, 13:44   #406 (permalink)
 
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Quote:
Originally Posted by AirRabbit View Post
I’ll just leave that manual paragraph alone for anyone’s contemplation.
The manual paragraph you have quoted is referring to inflight icing. What it has to do with attempted takeoff with ice contamination of the upper wing surface, accrued during ground operations, which happens to be the subject of the thread?

Quote:
Originally Posted by AirRabbit View Post
My original comment was to correct what I saw as an incorrect impression that it was a the low engine takeoff power that caused the accident. The NTSB officially, and at least one NTSB participant (quoted by one of the posters here) collectively agreed that the engine power setting did not cause that accident.
There is no dissenting opinion included in the NTSB report. NTSB is pretty clear that too low power did not cause the accident on its own but that without it, the catastrophe would not have happened:
Quote:
Originally Posted by NTSB AAR82-08
The aircraft could not sustain flight because of the combined effects of
airframe snow or ice contamination which degraded lift and increased
drag and the lower than normal thrust set by reference to the erroneous
EPR indications. Either condition alone should not have prevented
continued flight.
The story about NTSB member disagreeing with it comes from the anonymous poster on the anonymous forum where every post comes with caveat:
Quote:
Originally Posted by PPRuNe staff
As these are anonymous forums the origins of the contributions may be opposite to what may be apparent. In fact the press may use it, or the unscrupulous, or sciolists*, to elicit certain reactions.
Quote:
Originally Posted by AirRabbit View Post
The NTSB reached the conclusions they reached.
As presented, it is a perfect tautology. However, NTSB has quite comprehensively documented the method of getting to conclusions, while on the other side...

Quote:
Originally Posted by AirRabbit View Post
Some of us in the aviation world disagree with those conclusions … welcome to the world of individuality.
...most of those disagreeing with NTSB conclusions just say it-was-not-so, without further reference or with unverifiable reference at the best. Every individual is entitled to his own opinion but in my humble opinion that no one is entitled to his own set of facts should not be debatable.

Quote:
Originally Posted by GSLOC
We all know that stall warning won't occur (in ice-contamination case) when actual stall happen because system does not measure disturbed air flow and contamination on wings.
Actually, we shouldn't be knowing that. The effect of ice contamination is dependent on so many variables that it is impossible to quantify it except in the postmortems. In Air Florida 90 case, Cd was affected far worse than AoAcrit, so the crew got the stickshaker before stalling - which combined with misplaced belief that stall always comes before stickshaker when wing is contaminated resulted in some wrong theories. What you referred to is worst case scenario while the best case contamination scenario happens any given snowy day; certification margins are not entirely eaten up at half-the-wingspan height and aeroplane happily flies away.

Quote:
Originally Posted by GSLOC
Can they for instance command pitch that is in excess of reduced critical AOA?
They can command the pitch that would lead to flight path that would lead to AoA exceeding AoAcrit of contaminated wing, however, chances for such adverse contamination combined with low V2 are very slim. "Pilots" have to determine how lucky they feel. Pilots de-ice and anti-ice if needed but do their best to ensure nothing except de-cing fluid is on their wings as they push the thrust levers far forward. Wordgames such as the exact meaning of "adherence" and "takeoff" don't come into play.
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Old 30th Apr 2012, 13:44   #407 (permalink)
 
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Frankly, I find AirRabit's analysis and comments very persuasive. I appreciate them very much.

Question: Given that most accidents involve a chain of causal elements ("but for ..." the accident wouldn't have happened), why elevate one (or more) to be the "probable cause" and relegate the rest to "contributing to"?

I know the NTSB may be charged by statute to do this, but does it really make sense? I believe that other jurisdictions (Canada?) just identify the causal elements and don't attempt to elevate any to being "THE Cause"?

Last point. It is called the "probable cause", not the "proven cause". So why the vitriol when someone posts a dissenting opinion?

Last edited by Crabman; 30th Apr 2012 at 13:56. Reason: Changed punctuation of a question to "?". Duh!
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Old 30th Apr 2012, 22:08   #408 (permalink)

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Quote:
There is no dissenting opinion included in the NTSB report. NTSB is pretty clear that too low power did not cause the accident on its own but that without it, the catastrophe would not have happened:
So how do you answer AirRabbit's conjecture that the B737 characteristic for alarming and uncontrollable behaviour with leading edge contamination possibly occurred and all that greater thrust would have achieved would have been that the aircraft and its occupants would have reached the point where the tragedy was inevitable marginally quicker?

Addressing that one point would be appreciated, my apologies if I have missed where you have addressed it.
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Old 1st May 2012, 18:54   #409 (permalink)
 
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Quote:
Originally Posted by Clandestino
There is no dissenting opinion included in the NTSB report. NTSB is pretty clear that too low power did not cause the accident on its own but that without it, the catastrophe would not have happened
With my respectful apologies to sabenaboy after having agreeing to take his very appropriate and very worthwhile recommendation … I feel one last rebuttal may be in order.

Of course there is no “dissenting opinions included IN the NTSB report … that’s not what NTSB reports do … but that doesn’t mean that there are NOT a large number of aviation professionals who have dissenting opinions about what that report says. As the investigation revealed (and referenced here) the “low power setting” of the engines did not cause the accident” … but the only way an airplane could have continued flight – even with all the power both engines were capable of producing - would have been if the attitude of the airplane was such that the engines – even at Max Thrust – could have pushed the airplane through the air at the attitude achieved at that time. Recall the video of the F-100, with the afterburner lit? Recall it wallowing through the air prior to impact? … this was THE specific event that generated the term “Sabre-dance.” That F-100 SuperSabre was at a pitch attitude that even with the A/B blasting everything under it into small dust particles – there was insufficient thrust to push that airplane in the direction opposite to that thrust. So too was that B-737 … the pitch attitude of that B-737 – caused by the uncontrolled pitch-up caused by the incorrect deicing/anti-icing procedures applied – was such that all the thrust of both those engines – and I don’t care what power setting they could have selected – would have resulted in exactly the same end … just like what occurred to that F-100 SuperSabre. Just in case you forgot, jet engines produce thrust to push the airplane in the direction opposite to that thrust vector – nothing more – nothing less. With any thrust, an airplane would be able to be pushed only in the direction opposite to that thrust direction. In both of these cases, the F-100 and the B-737 … there wasn’t enough thrust capable of being generated even with the added thrust of the A/B in the F-100 case … even with full power, maximum power, throttles-bent-over-the-fire-wall power in the B-737 case – there wasn’t enough thrust to push the airplane “forward” sufficiently to achieve sufficient lift to maintain flight. And, before someone points out that "they did it in a simulator." Yeah. I know something about simulators as well ... and given the right knowledge and time at the simulator's input keyboard, I can make a Cessna 152 simulator "fly" just exactly like the space shuttle.

Quote:
Originally Posted by M.Mouse
So how do you answer AirRabbit's conjecture that the B737 characteristic for alarming and uncontrollable behaviour with leading edge contamination possibly occurred and all that greater thrust would have achieved would have been that the aircraft and its occupants would have reached the point where the tragedy was inevitable marginally quicker?

Addressing that one point would be appreciated, my apologies if I have missed where you have addressed it.
This is probably the “question of the thread,” thanks, M.Mouse!

As I pointed out … way back on April 17th in post #276 …
Quote:
I believe that once this crew pushed the throttles forward with the intent to takeoff, they were doomed. The only way that an accident could have been avoided at that point, was to have kept the airplane on the ground until a sufficiently higher airspeed was reached prior to initiating the rotation. Unfortunately, not only did the crew not know that this would be necessary, they wouldn’t have known the “magic” airspeed number. Even if they had pushed both throttles all the way to the firewall from brake release, and then rotated at the computed rotation airspeed (as they did) the airplane would have performed in exactly the same way. It would have uncontrollably pitched up to at least the 22 – 24 degree attitude; likely more given witness statements … where some said they saw “the aircraft was flying at an unusually low altitude with the wings level at a nose-high attitude of 30 degrees to 40 degrees before it hit the bridge.” It would have entered the same deep aerodynamic stall. The flight crew would have been unable to bring the nose down aerodynamically. Unfortunately, in that condition, full thrust on both engines would have been insufficient to maintain flight. All who were affected by this tragedy were victims of longitudinal differential lift. The flight crew did not have the luxury of time to analyze, consider, and choose accordingly.
Had this B-737 flight crew kept the airplane on the ground until achieving a forward speed sufficiently high to have produced lift even somewhat evenly along the entire length of both wings – the asymmetrical longitudinal lift components may have been small enough that the pilots could have maintained control. However, when the F/O brought the control column back to a neutral position – in anticipation of rotating at the computed "rotation" speed (however he was planning to rotate – to whatever attitude he planned to rotate) – the airplane took over … snatching the pitch control completely away from that pilot and taking that airplane up to an attitude that achieved a rather severe stall buffet only 3 seconds after having all three gear (the nose and both mains) on the runway. THAT was the reason the Captain was recorded as saying - at THAT specific time ... "Easy!" Conservative estimates say that the stall buffet wouldn’t have been reached until the pitch of the airplane achieved something like 24 degrees – so, the pitch attitude was at least that high. Some witnesses (forming angles with their hands when specific numbers made no sense to them) indicated to investigators that the airplane may have been at an attitude of more than 40 degrees nose up. Think about that for a minute … 40 degrees nose up! With the airplane's forward momentum (which is what got it from the runway to the 14th Street bridge - it certainly didn't "fly" there) it’s almost anyone’s guess as to what Angle of Attack was actually achieved. So ... was it possible for that crew to make that B-737 "fly" at that pitch attitude ... with that AoA ... with a measley additional 15-20% thrust? Not at that kind of airplane attitude – talk about “son-of-Sabre” … as I said previously, an Atlas Booster would have had problems getting that airplane to "fly."

For Reference:
Aviation Video: F-100 test flight crash (Sabre Dance) | Patrick's Aviation

Last edited by AirRabbit; 1st May 2012 at 20:10.
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Old 2nd May 2012, 14:52   #410 (permalink)
 
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Quote:
Originally Posted by M.Mouse
So how do you answer AirRabbit's conjecture that the B737 characteristic for alarming and uncontrollable behaviour with leading edge contamination possibly occurred and all that greater thrust would have achieved would have been that the aircraft and its occupants would have reached the point where the tragedy was inevitable marginally quicker?
How could I possibly answer that? I am not an aerodynamicist familiar with 732. Heck, I'm not even rated on her, but I can easily find an expert opinion on the matter:

Quote:
Originally Posted by NTSB AAR82-08, page 54
The Safety Board concludes that neither the low thrust used during the takeoff
nor the presence of snow or ice on the aircraft, alone, would likely have led to the crash.
In most other reported incidents in which B-737’s have pitched up during takeoff, the
flightcrews had sufficient control authority with forward control column force and
stabilizer trim to overcome the pitching moment, reduce the pitch attitude, accelerate
to a lower angle of attack, and climb out successfully. The Safety Board believes that if
the proper thrust level (that for 2.04 EPR) had been used for the takeoff this flightcrew
could have recovered from any difficulties caused by the contamination - induced
aerodynamic performance penalties.
Furthermore, based upon the engineering simulation, the Safety Board
concludes that even with the low thrust during the takeoff roll and the aerodynamic
penalty of the snow or ice contamination, the accident was not inevitable as the aircraft
lifted off. However, both immediate recognition of the situation and positive effective
actions by the flightcrew to both counter the noseup pitching moment and add thrust were
required. With these actions, the aircraft should have been capable of continued
acceleration and achieved a sufficient performance margin for climbout.
Quote:
Originally Posted by NTSB AAR82-08, page 68
The engineering simulation of Flight 90’s flight profile disclosed that the aircraft’s rate of acceleration after liftoff, below normal
because of the reduced thrust, was further impaired by a high noseup pitch attitude attained during the takeoff rotation.

Consequently, the aircraft did not reach an airspeed
safely above the stall speed. The high pitch attitude occurred because the flightcrew
failed to, or was unable to, react quickly enough to counter the aircraft’s longitudinal trim
change produced by the wing leading edge contamination. The reports since 1970 by other
operators who have experienced abrupt pitchup or rol off immediately after liftoff of
B-737 aircraft indicate that the B-737 may have a greater known inherent pitchup
characteristic than other aircraft in this regard a result of small amounts of frost, snow,
or ice on the wing leading edge. The Safety Board could not determine whether the
aerodynamic design makes the B-737 more sensitive to pitching or rolling moments when
the wing is contaminated, or whether more frequent operation of these aircraft in
environmental conditions conducive to snow or ice accretion during ground operations,
coupled with the near to the ground wing placement, accounts for the higher number of
reported B-737 pitchup/rolloff incidents, Regardless, the Safety Board concludes that the
pitchup tendency of the aircraft because of leading edge contamination contributed to the
accident. However, to place this contributing factor in perspective, the Board notes that no
aircraft design requirements include the ability to perform with snow or ice
contamination and that any known contamination, regardless of the amount or depth, must
be viewed as potentially critical to a successful takeoff. For this reason, flightcrews are
not only dissuaded, but are prohibited, from attempting a takeoff with such
contamination.
Hope this helps. The report goes into great detail how the conclusions were made.

So how come some PPRuNers get convinced by the theories that are at odds with the expert analysis and have no traceable source? PukinDog nicely analyzed one such contribution:

Quote:
Originally Posted by Pukin Dog
You make decent enough arguments on a few points, food for thought anway, but wrapping them in a suggestion that this crew's actions and words represent anything like a barometer of "what was known", done, and disseminated (including to them) re winter ops/contamination/ etc 1982 is a gross misrepresentation. This crew was nothing of the kind, and you whitewashing this crew's inexperience and non-compliance for the sake of focusing on the de-icing issue hints of an agenda.
The picture certain poster has painted has some true details, some true yet grotesquely exaggerated, some completely irrelevant, some that are so-pulled-out-of-the-thin-air they cannot be verified at all and some brazenly false. When the details are put together the composition reveals what was the message (original term was "the truth") that the contributor wanted to get through: the poor, hapless crew was tragically betrayed by almost everyone. They were betrayed by the de-icing crew that poured water instead of glycol mixture on their wing. They were betrayed by FAA by not having developed the holdover times at the time. They were betrayed by the Boeing co designing the aeroplane that would pitch-up when stalling with iced leading edge. They were betrayed by the ATCO using too little spacing between them and landing Eastern. Basically, it was everyone else's fault, they were just the one who died. There was nothing they could do. They were doomed.

Realistic picture, eh? Not at all. So how come it is believable? Basic HF: people are convinced of something because they want to be convinced. If reading the accident report pages where crew's mistakes are neatly explained fills you with horror and, despite the facts, you want to believe that QH90 (or any other) crew did their best but it was tragically insufficient, to sooth your anxiety you would do well to listen to alternative theories of e.g: de-icing with water, composite fins being weaker than metal ones or Airbus cockpit being a deathtrap by design.

However, if you are into learning something from mistakes of others, lest you repeat them, it's far better to read and understand what is written in the official accident report. Stress is on understanding as it will help you recognize skewed reports produced under undue political pressure or when the good report is unduly smeared as false.

Whatever suits you, terms of the PPRuNe use do not preclude going whichever path you choose. Outcomes might differ, though.
Clandestino is offline  
Old 2nd May 2012, 16:19   #411 (permalink)

DOVE
 
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I cannot refrain from intervening because it can be deadly for your seeds to sprout.
"Quousque tandem abutere, AirRabbit, patientia nostra?"
You know me and the pulpit my words come from.
Can I say the same of you?
I don’t think you’ve ever been (sitting at the front row of a plane and not in front of a 6-Drawer Oak desk) in such a situation:
Typical winter night in Europe, about to leave from an airport during a dreadful snowstorm.
In addition to the usual procedures we had to:
- Take a place in the queue for the de-icing
- Wait every few tens of minutes for the runway in use and taxiways to be cleared from snow.
- Based on the estimated time of completion of the aforementioned procedures, request a slot for departure.
- Calculating the synchronization of all of that to determine if and when to surrender to the pressure of ramp agent who wanted the passengers to be embarked.
I had long since given up the scheduled departure time.
It's obvious that it was wishful thinking to have all the above operations completed all together.
If the runway had been cleared, the plane was not yet being deiced / anti-iced, or vice versa, or the slot provided had expired and reassigned half an hour later, and then we had to go back to the starting point.
If the passengers had boarded, we had to invite them to remain on board for not losing the priority acquired; maybe we prayed the flight attendants to serve a refreshment.
Finally everything was ready to start (there was a tyrannical "holdover time"), but not without having alerted the Purser not to hesitate to advise if he saw some snow on the wings.
And then:
There were conditional procedures to apply: special operations, "Cold Weather Operations" and "T.O. and Landing on Contaminated Rwys ".
They had to be performed, with the contribution of PF and PNF; a flight controls test at the beginning and at the end of taxi, a test of extension and retraction of the flaps / slats, the activation of Engine Anti-ice (with engine run-up every ten minutes to remove any ice formed on the intake of the engines and on PT2 probes), and the predisposition of the Airfoil anti-ice, after start.
After rotation we were expected to cycle the “retraction / extension / retraction” of the landing gear in order to shake any slush from it.
It's absolutely clear that avoiding all of this fuss would make life much more easy, and I confess that more than once I found myself in the embarrassing
position to explain to a passenger of mine stating: "That guy did not perform the deicing and is going, while we are having such a delay ... "
My answer: "Safety is our first goal."
CONTAMINATION ON ANY PART OF THE AIPLANE: NO GO!
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Old 2nd May 2012, 21:52   #412 (permalink)
 
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"It's absolutely clear that avoiding all of this fuss would make life much more easy, and I confess that more than once I found myself in the embarrassing
position to explain to a passenger of mine stating: "That guy did not perform the deicing and is going, while we are having such a delay ... "
My answer: "Safety is our first goal."

If anything is going to be learnt from the vid of the flight from SVO its that us passengers are far more likely to accept your explanation than was so even a few months ago.
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Old 3rd May 2012, 19:41   #413 (permalink)
 
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When M.Mouse asked about the B737 characteristic for alarming and uncontrollable behaviour with leading edge contamination, you answer with …
Quote:
Originally Posted by Clandestino
How could I possibly answer that? I am not an aerodynamicist familiar with 732. Heck, I'm not even rated on her, but I can easily find an expert opinion on the matter:
…and you come up with the following??

Quote:
(NTSB AAR82-08, page 54) “In most other reported incidents in which B-737’s have pitched up during takeoff, the flightcrews had sufficient control authority with forward control column force and stabilizer trim to overcome the pitching moment, reduce the pitch attitude, accelerate to a lower angle of attack, and climb out successfully.”
The NTSB’s words (not mine) … “in most other reported incidents … the flightcrews had sufficient control authority…” Most? What about the other incidents? Just how many “other incidents” were there? Did any of those other incidents include an absence of control authority? What happened in THOSE cases?

Quote:
(NTSB AAR82-08, page 54) “The Safety Board believes that if the proper thrust level (that for 2.04 EPR) had been used for the takeoff this flightcrew could have recovered from any difficulties caused by the contamination – induced aerodynamic performance penalties.”

and

(NTSB AAR82-08, page 52) “If the flightcrew failed to, or was unable to, counter the pitchup moment of the aircraft with sufficient forward control column force, the aircraft could become airborne at an excessively high pitch attitude. The aircraft would not accelerate and it would retain a high angle of attack and high drag.”
So the “expert opinions” you settle on are these? Do you have an opinion on which of these diametrically opposite expert opinions is the one you care to believe? … which is it? …The crew could have recovered but failed to do so … or … the crew was unable to recover? Did you flip a coin … or are you prejudiced and don’t want anyone to know?

While I will stop way short of claiming to be an aerodynamic expert on the B-737-200, I am rated on the B-737 and I do have considerable time in the -200 series aircraft (even more in other makes/models … despite some here, like Mr. Doves, who choose to disbelieve my “profile” information – which, of course, is their – his – individual choice – even if, however self-serving it may seem to others to be, I will continue to believe that I am my own best judge of my own knowledge and experience.) … it is my contention that the NTSB selected a “middle-of-the-road” response by saying (see NTSB AAR82-08, page 68) “The reports since 1970 by other operators who have experienced abrupt pitchup or roll off immediately after liftoff of B-737 aircraft indicate that the B-737 may have a greater known inherent pitchup characteristic than other aircraft in this regard a result of small amounts of frost, snow, or ice on the wing leading edge. The Safety Board could not determine whether the aerodynamic design makes the B-737 more sensitive to pitching or rolling moments when the wing is contaminated, or whether more frequent operation of these aircraft in environmental conditions conducive to snow or ice accretion during ground operations, coupled with the near to the ground wing placement, accounts for the higher number of reported B-737 pitchup/rolloff incidents, Regardless, the Safety Board concludes that the pitchup tendency of the aircraft because of leading edge contamination contributed to the accident.”

It sounds as though the NTSB recognizes that it’s not as damning to accuse a system or design feature of an airplane as having contributed to an accident as it is to say that particular system or design feature actually caused an accident. Libility … cost … reputation … etc., get to be really stupifyingly large issues that no one in a political arena would be willing to challenge. Now, I suppose you’re going to tell us that government officials don’t protect themselves and their organizations when they believe that is the proper or prudent thing to do … sure … we all know that.

Contrary to Clandestino’s claim that “a certain poster” (could he possibly have meant someone other than me?) has submitted “…some true details, some true yet grotesquely exaggerated, some completely irrelevant, some that are so-pulled-out-of-the-thin-air they cannot be verified at all and some brazenly false.” With the amount of information I’ve posted – I’ll not offer an all-encompassing denial … but I will – and I do – deny that anything I’ve posted is knowingly wrong, knowingly inaccurate, knowingly exaggerated, knowingly irrelevant, and certainly NOT “brazenly false.” To the contrary – everything I’ve posted has been relevant – or I wouldn’t have posted it (still don’t understand that accusation) … some of what I posted is directly from our friends at the NTSB – everything I posted is, to the very best of my professional knowledge and training, is true … at least as the facts that support them are true, without any exaggeration or limitation – and nothing – absolutely nothing in any of my posts was “pulled-out-of-thin-air” – and were I not trying to keep this discussion on a civil level (for everyone and everything concerned) that kind of comment could have been taken in a way that, had it been offered personally in the local pub – there is at least a reasonable chance that both of us would have been taken away – one to a local medical facility and the other to a local constabulary – and I would have hoped he had resilient recuperative abilities. While some here may think lying to be an acceptable, perhaps even an expected, part of this business, but I don’t … I don’t lie, I don’t expect others to lie, and I particularly don’t appreciate being accused of doing it. If anyone here can point to anything that I’ve posted about which you have legitimate concerns as being untruthful or inaccurate in any way… please let me know and I’ll do my very best to provide whatever additional facts, theories, reports, or other information that may be appropriate to rectify that issue – but, as many of you know here, I’ll stop short of providing information that may give away my identity. As I’ve repeated here often … if my employers knew of my participation, I’d likely get an opportunity to refer to them as my “former” employers – and that is a step I’m not quite ready to make – it also requires me to be a bit more informative in my posts – as you would then either agree or disagree based on the merits of what I post and not be tempted to agree or disagree with me because of the positional authority I may hold. For example if I were a senior NTSB investigator – you might tend to believe me more – but my bosses on the Board might think I’ve overstepped my agreed-to responsibilities and other oaths I may have taken.

What I continue to find hard to believe is that throughout history professional aviators have not appreciated the label of “pilot error” that gets affixed to more than a fair share of difficult to analyze accident or incident situations. Sure pilots make errors – even very good pilots make errors – I’ve certainly made my fair share – perhaps more than my fair share. Sometimes errors wind up contributing to or causing accidents or incidents - sometimes they do not. Sometimes accusations are true and accurate … sometimes they are not.

Mr. Clandestino alleges that I (he uses the term “contributor” – hmmm … wonder if there is a sinister concern for being caught in a slander?) believe that the crew “was betrayed” by a whole series of people and events – concluding by stating that “…people are convinced of something because they want to be convinced…” and even describes the flight crew as “poor and hapless … tragically betrayed by almost everyone.” An aside here, for a moment … it is clear that Mr. Clandestino understands, or at least rather easily uses, “figures of speech” in his communications … where the particular figure of speech he chooses to use here, described as “irony,” is used in his description of the crew here … where, clearly, he says one thing but the intent is clearly to convey the opposite thing - that the crew members are not “poor and hapless” and were not “tragically betrayed by almost everyone.” For everyone’s benefit, the use of an “ironic” statement, as defined in most English textbooks, is the following: “Irony - the use of word/sentence in a way that conveys a meaning opposite to its usual meaning.” Some here may recall the allegation made that the flight crew deliberately taxied behind a preceding airplane to “get his wings deiced.” And they based that on a CVR transcript that read, as I recall “Don’t do that Apple, I need by other wing done.” Is it so out of bounds to even remotely consider that the intent of this statement would also be an ironic statement? As the definition says … “the use of word/sentence in a way that conveys a meaning opposite to its usual meaning.” As an exercise, try tape recording your next departure from engine start to level off and see if, or how many times, you and your “mates” use Ironic statements to punctuate or add to the conversation. It just might scare you to realize that what you said, would be what everyone would hear if you were to die in a subsequent crash of that airplane.

He apparently does not believe that the flight crew was
Quote:
“…betrayed by the de-icing crew that poured water instead of glycol mixture on their wing.”
Well – what did the de-icing crew pour all over the airplane? According to the NTSB report the airplane “…was deiced with 100 percent water and the final overspray was applied with a 20 to 30 percent deicer to water solution selected. Subsequent tests of deicing fluid/water solution taken from the Trump vehicle showed that the mixture dispensed differed substantially from the mixture selected. The percent of deicing fluid in solution was about 18 percent rather than 30 percent.” A fact that was also revealed during the tests conducted on the Trump vehicle but not included in the NTSB report, was that the mixture of 18 percent (rather than 30 percent when that value was selected) was measured at nominal, or close to zero, flow rate. The content with any additional flow rate was extracted almost exclusively from the water tank and virtually none from the glycol tank. The specific numbers were not available as the flow rate “pulsed” with the RPM of the drive pump and there was the residual amount of glycol present at the nominal flow rate. At the completion of the test, it was evident that the volume in the water tank was lowered by approximately the amount calculated for the time additional flow rates were used, but the volume in the glycol tank was not appreciably changed during this period of increase flow rate.

He apparently does not believe that the flight crew was
Quote:
”… betrayed by FAA by not having developed the holdover times at the time.
I’m not sure of this reference, as there is no mention of “holdover times” or “HOT” in the Accident Report anywhere that I can find. Perhaps he could provide all of us with a reference for his thoughts on this issue?

He apparently does not believe that the flight crew was
Quote:
”… betrayed by the Boeing co designing the aeroplane that would pitch-up when stalling with iced leading edge.”
Let’s see about this one:
NTSB Report Page (ii) “…the known inherent pitchup characteristics of the B-737 aircraft when the leading edge is contaminated with even small amounts of snow or ice…”
NTSB Report Page 1 “…the known inherent pitchup characteristics of the B-737 aircraft when the leading edge is contaminated with even small amounts of snow or ice…”
NTSB Report Page 34 “…Since 1970 there have been a number of reports by operators of B-737 aircraft, who have experienced an aircraft pitchup or rolloff immediately after takeoff in weather conditions which were conducive to the formation of ice or frost on the wing leading edges. The Safety Board is aware of 22 such reports during the period.”
NTSB Report Page 35 “…The continuation of reports of pitchup/rolloff occurrences prompted The Boeing Co to examine further the B-737 aircraft sensitivity to leading, edge contamination. In 1977 plans were formulated for wind tunnel and flight tests. Even before conducting these tests, The Boeing Co. on February 23, 1979, issued Operations Manual Bulletin 79-2 to advise flightcrews of a possible inadvertent pitchup/rolloff after takeoff due to ice accumulation on leading edge devices. The bulletin stated that several operators of B-737’s had reported pitchup and/or rolloff after takeoff caused by ice accumulations on leading edge devices and that such incidents had usually occurred following the application of reverse thrust while taxiing on snow-covered taxiways.
NTSB Report Page 35 As part of its investigation of the reported incidents, The Boeing Co. flight tested a B-737-200 advanced airplane in the fall of 1980 to quantify the aerodynamic effects of contaminated leading edge slats. The leading edge slats were coated with an epoxy potting compound and the surface was roughened with a paint roller to simulate a coating with corn ice. A series of stalls was conducted with flaps up, and at flap positions of 1, 15, and 40. The stall characteristics with both symmetric and asymmetric leading edge contaminations were characterized by a very apparent pitchup, yaw rate, and rolloff. These characteristics were more pronounced at flap settings less than 5…

OK. OK. I think you get the picture. Betrayed? Maybe? If YOU were flying an airplane that had these kinds of “known” tendencies … and knew that they had occurred more than 20 times … would you like to know?

He apparently does not believe that the flight crew was
Quote:
”…betrayed by the Air Traffic Controllers using too little spacing between them and landing Eastern.”
Well, it is true that the accident flight was cleared onto the runway at 1558:58. Subsequently, they were cleared for takeoff at 1559:24. Those times don’t look too “pushed” until you realize that there was moderate snow falling throughout this time – and the taxiways and the runway had some accumulation. Do you taxi from a snow-covered taxiway onto a snow-covered runway using the same techniques you would use if the taxiway and runway were clear and dry? Of course not! Is everyone aware that the tower controller could not “see” the approach end or the departure end of the runway at that time? So, maybe we can see if they were “betrayed” by looking again at the CVR transcript:

1600:03 LC Eastern fourteen fifty-one, the wind Is zero one zero at one one you're cleared to land runway three six, the visual range touchdown two thousand elght hundred rollout one thousand six hundred/
1600:04
1600:05 CAM-2 Ah, that's not right
1600:06
1600:07 CAM-2 (Well) ---
1600:08
1600:09 CAM-1 Yes It is, there's eighty
1600:10 CAM-2 Maw, I don't think that's right
1600:11 E451 Fourteen fifty-one cleared 'to land over the lights

Now, I should point out (not that you weren’t aware of it – just reminding everyone) that one of the difficulties in reading a CVR transcript and understanding what took place just prior – during – or just after any point on that transcript is not recognizing that some things are said in a second or less … other things take a bit longer to say … for example … the Local Controller’s clearance to EA1451. It’s on the CVR Transcript as having been said at 1600:03. Try reading that statement and see how long it takes. Also, you have to know that controller had to view his “bright” scope, the indications for wind speed and direction … and … make that radio call. Was all that done in 1 second? I doubt it … in fact, I suspicion that as the Local Controller unkeyed his microphone after issuing the landing clearance, the Eastern pilot immediately responded – even though the time of that radio call is shown to be at 1600:11 – fully 8 seconds after the Transcript indicates the time of the clearance being issued. Throughout this Eastern-Tower exchange the accident flight crew was busy making a takeoff.

Don’t let me put thoughts into your head – you decide. You’re the Captain on the B-737. You’ve received clearance onto the runway, taxied out, begun the line-up turn, pushed up the throttles to get the engines spooled … the F/O takes control of the airplane. He further spools the engines up toward TO EPR setting – what are you watching? The throttle position? … the engine EPR gauges?… the centerline of the runway? Your F/O sets what he believes is or is close to TO EPR and you prepare to take over monitoring of the throttles. At that time, he says something like “Geeze – look at that thing? That don’t seem right, does it?” Where do you look to see what he’s talking about? … remember, you’re blasting down a snow-covered runway, with the windshield wipers on – unable to see very far ahead … do you care what progress you’re making? … do you care what your airspeed is now? By the time you ask yourself those questions, he again says “Ah … that’s not right” All this while you’ve heard the tower controller issuing landing clearance to that guy behind you … You look at the airspeed … 80 knots … and you decide to let the F/O know where you were and your airspeed … so you say in a calm and clear voice, “Yes it is, there’s eighty” … and just as you get those words from your mouth, you hear the landing traffic over the tower frequency respond to the tower controller’s clearance by saying, “1451 cleared to land over the lights.” WHAT?!?!? OVER THE FRIGGIN LIGHTS!?!?!? What do you do, now … abort?

It would seem that Mr. Clandestino is “hoisted by his own petard.” By way of example he states:
Quote:
Originally Posted by Clandestino
“…people are convinced of something because they want to be convinced. If reading the accident report pages where crew's mistakes are neatly explained fills you with horror and, despite the facts, you want to believe that QH90 (or any other) crew did their best but it was tragically insufficient, to sooth your anxiety you would do well to listen to alternative theories of e.g: de-icing with water…”
Or … perhaps this could be said somewhat differently … “people are convinced of something because they want to be convinced. If reading the accident report pages where crew's mistakes are neatly explained fills you with satisfaction and comfort because you never make those kinds of errors, and, because of these facts, you want to believe that you are insulated from similar potentialities of crew error or confluence of other apparently dissimilar circumstances such that your anxiety may be soothed, you would do well to read only the report and not challenge any aspect regardless of how familiar that aspect may sound.

Again, a worthwhile quote:
Quote:
Originally Posted by Clandestino
Whatever suits you, terms of the PPRuNe use do not preclude going whichever path you choose. Outcomes might differ, though.
One additional quote from the Accident Report - once again leading interested readers to the conclusion that the airplane was "auto-rotated" to an unrealisitc and unrecoverable pitch attidue due to the wing contamination caused by impropter deicing/anti-icing procedures and equipment.
Quote:
Ground witnesses generally agreed that the aircraft was flying at an unusually low altitude with the wings level and had attained a nose-high attitude of 30 degrees to 40 degrees nose up before it hit the bridge.
A slight tendency to pitch up - slight tendency - 30 to 40 degrees nose up? Really?

Last edited by AirRabbit; 4th May 2012 at 13:16.
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Old 3rd May 2012, 21:29   #414 (permalink)
 
Join Date: Feb 2005
Location: Correr es mi destino por no llevar papel
Posts: 1,263
Quote:
Originally Posted by DOVES
I cannot refrain from intervening because it can be deadly for your seeds to sprout.
Don't worry, chances are they won't. Pilots who know a bit about aerodynamics can have good laugh at some propositions aired here. Those who don't, probably won't look up to PPRuNe to expand their knowledge. Those who are ignorant of matters aeronautical, yet easily influenced into accepting as true the lethally wrong theory, when appeal to their emotions is made, are very unlikely to have any chance of putting the wrong theory into practice. Main reason being the lack of piece of paper, unequivocally showing that relevant authority deems them capable of safely slipping the surly bonds of earth.

The fellow plays his own tune for his own audience.

No need too feed him.
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Old 3rd May 2012, 21:43   #415 (permalink)
 
Join Date: Sep 2001
Location: Third planet from the sun
Posts: 289
@AirRabbit

Well, great post once again. You convinced me -and many others, Im sure- even more!
But... I still think you should have followed my advice and stop responding.

He said it himself: "No need to feed him" (He's not worth the trouble and he's just harassing you. Don't take the bite.)


(English is not my mother tongue. I apologise for not being able to respond as eloquently as you can.)
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Old 6th May 2012, 06:36   #416 (permalink)
 
Join Date: Feb 2005
Location: Correr es mi destino por no llevar papel
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Got away with the snowy wings - again!

Interestingly, when you open the video on YouTube, first suggested similar video is:


It's about AirFlorida 90. Recommended if your Russian is better than English.
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Old 6th May 2012, 09:37   #417 (permalink)
 
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Posts: 2,821
rainbow100,
Interesting, but would not alter my operation one bit.
That snow should have been removed.

Only exception to my mind would have been overriding military requirement.
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Old 14th May 2012, 08:48   #418 (permalink)
 
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Posts: 1,472
Maybe its time the FAA updates its FARs?
According to FAR 121 ,Aeroflot did not break any of its rules..as reckless as its pilots actions may have been..

Quote:
(d) A certificate holder may continue to operate under this section without a program as required in paragraph (c) of this section, if it includes in its operations specifications a requirement that, any time conditions are such that frost, ice, or snow may reasonably be expected to adhere to the aircraft, no aircraft will take off unless it has been checked to ensure that the wings, control surfaces, and other critical surfaces are free of frost, ice, and snow. The check must occur within five minutes prior to beginning takeoff. This check must be accomplished from outside the aircraft.

[Doc. No. 6258, 29 FR 19222, Dec. 31, 1964, as amended by Amdt. 121–231, 57 FR 44942, Sept. 29, 1992; Amdt. 121–253, 61 FR 2615, Jan. 26, 1996]
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Old 14th May 2012, 13:59   #419 (permalink)
 
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@de facto

How on earth do you conclude that aircraft could possibly have complied with:

Quote:
it has been checked to ensure that the wings, control surfaces, and other critical surfaces are free of frost, ice, and snow.
Never mind that conducting an inspection from outside the aircraft within 5 mins of takeoff at a Russian airport is probably impossible without the security guys getting very excited.
Mad (Flt) Scientist is online now  
Old 14th May 2012, 15:36   #420 (permalink)
 
Join Date: Sep 2007
Location: new jersey
Posts: 32
Quote:
Maybe its time the FAA updates its FARs?
According to FAR 121 ,Aeroflot did not break any of its rules..as reckless as its pilots actions may have been..

I don't think the reg you quoted means what you think it means. All that says is IF a part 121 operator does not have an approved ground deicing/anti-icing program, they may still take off when weather conditions could create structural contamination on the aircraft if they do a pre-takeoff contamination check within 5 minutes of takeoff from the exterior of the aircraft. If there is no ice or snow adhering, they may take off.

If the airline does have an approved ground deicing/anti-icing program, then that program must be adhered to.

Basically, if I had a little commuter operation out of San Juan, it might not be worth it to me to come up with a ground ice program in my ops specs. If a freak snowstorm hit the Caribbean, I could still take off if I was able to perform the pre-takeoff contamination check AND the airplane was clean. If anything was adhering to the wings, or any other critical surface, no takeoff.

With that in mind, from that video the Aeroflot plane would have been in violation.
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