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.