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Old 3rd May 2012, 19:41
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AirRabbit
 
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When M.Mouse asked about the B737 characteristic for alarming and uncontrollable behaviour with leading edge contamination, you answer with …
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??

(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?

(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
“…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
”… 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
”… 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
”…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:
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:
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.
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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