Barit 1:
Initially posted by barit1
Here's a bit of enlightenment for you: The airplane was cert. to continue TO w/50% thrust AFTER V1. However, that's a very different situation from a TO w/ 75% of calculated thrust at brake release, coupled with contaminated wing surfaces and who-knows-what on the runway. He didn't reach V1 until he was on the far-end upside-down numbers. I don't have the report at the ready, but I don't think he ever reached Vr. This accident could have also happened with a gross TOGW error, or dragging brakes, as well as the EPR error. That crew sensed the slow acceleration in the seat of their pants but didn't abort when their common sense told them to.
Uhh …. Thanks for the regulatory update that you believe should have been enlightenment for me, sir, but I assure you, your efforts were not necessary.
The difference between accelerating with both engines to V1, losing an engine, and continuing the takeoff with one engine operating at 100% and the case you and I have been bantering about, and the ONLY differenced between them, would be the distance down the runway when rotation occurred. At, and after, that point, the accident airplane should have had 50% MORE thrust and able to fly quite well, thank you very much.
You seem to be very impressed with the NTSB accident report. Well, read it carefully and you’ll find some very interesting “facts” that are just not considered in the final conclusions. I’ll confess that I have no idea about the meaning of your statement “…until he was on the far-end upside down numbers.” I think that if you refer to the report (which you indicate you do have; it just wasn’t at the ready at your last post) you’ll see several things. Among them are the following:
The airplane immediately following the accident airplane in the takeoff queue, took off after the accident airplane with no apparent problems. Consider, if you will, that this airplane had been “exposed to the elements” just as the accident airplane was exposed, and for the same time period of time after being de-iced. Why, I would ask, did this airplane not have similar problems?
You will note the FDR tracing shows that the accident airplane went from a 3-point attitude (all 3 gear on the ground) beyond the stick shaker and into the stall buffet within just over 2 seconds! If you consider that the stall buffet wouldn’t have been encountered until about 22 – 24 degrees of pitch up at that airspeed, this would have made for a lightning quick rotation rate, on the order of 11 to 12 degrees per second. I remind you of two things; normal rotation rate is approximately 3 degrees per second, AND the F/O, who was at the controls, had indicated he was going to “takeoff the nose gear and then just the airplane fly off by itself.” Does that indicate anything inconsistent to you? A F/O wanting to deliberately limit the rotation to just getting the nose gear into the air, the normal rotation being 3 degrees per second – why, then, would the airplane rotate at 12 to 14 degrees per second?
You will also note the time-lapse between when the accident airplane was cleared onto the runway and when the throttles were advanced for takeoff. You will also note that there was an Eastern B727 on final approach to that runway at the same time – the distance out from landing of that B727 was only 2 and a half miles when the accident airplane crossed the hold-short line and was rapidly decreasing as the accident airplane taxied onto the runway and slowly, and deliberately, turned to line up for takeoff. How close did the two airplanes come? Well, estimates differ, but calculations from the tower tape, FDR and CVR recordings from both airplanes indicate that they BOTH were on the runway at the same time! Had the accident airplane aborted on the runway – there was, at least, a very good chance that both airplanes would have been accident airplanes!
You will also note that the “deicing” that took place in “the chocks” was accomplished with an improperly maintained Trump Deicing truck – that provided an incorrect mixture of heated water (to 160 degrees) and glycol – to the point that at high volume flow from the nozzle provided a whopping 3% glycol solution, NOT the 30% that was expected! Just a quick question, since you know so much about airplane performance, and such, what do you think the aerodynamic changes would be with a very smooth coating of clear ice all along the leading edge of a B737 wing? So that you won’t strain too much, let me help you, just a little. With very little deformation of the leading edge, the outboard portion of the wing will not produce lift until reaching a much higher airspeed than if there was no deformation. The wing roots will produce lift, although slightly less than with no deformation. Since the wing roots are farther forward, ahead of the cg, as soon as the flight crew relaxed forward control column pressure, the inboard portion of the wings, generating lift, rotated the airplane, and rotated it quickly to a pitch attitude of 22 – 24 degrees. The only thing that could have saved them at that point, and there was and is absolutely NO guarantee about that, was by moving the horizontal stabilizer to a more nose-down position. But since the airplane was airborne for just a bit over 15 seconds, it is doubtful that any stab movement would have been successful.
And finally, for this post, and in reference to my comment in my earlier post about why the PT2 probes were clogged with ice, but not from what most people believe … the PT2 probes were probably clogged with ice, but it was from the 160-degree water sprayed on them about an hour and 12 minutes earlier. Just enough time, in 22-degree weather, to allow the water filling those probes to freeze and provide inaccurate engine pressure ratio readings.
No sir, the accident did not happen because of a “gross takeoff weight error.” There were no “dragging brakes.” The airplane did reach V1; it is just that due to the error in the deicing procedures, the airplane became airborne beyond the control of the flight crew. And here’s a bit of interesting, and perhaps enlightening, news for you, sir. On the same day, SAS experienced almost the identical problem with one of their B737s operating out of Oslo, Norway. The difference was that the leading edge ice build-up was Mother Nature’s doing, not man’s, and as such, it was asymmetrical. The resulting pitch-up, equally uncontrollable, was also a rolling pitch (due to the asymmetry). Even thought the crew slammed the throttles to the firewall, input full opposite aileron and full opposite rudder, they were unable to control the pitch/roll of the aircraft. Fortunately, the advanced throttles began to accelerate the airplane as the nose dropped back down toward the horizon because of the radical bank angle. As the airplane accelerated, lift was produced over the outboard portions of the wing, including the ailerons, and that allowed the crew to roll back to level flight – but this happened below 100 feet AGL! Had they not had this bit of inconsistency from Mother Nature, the world would have seen B737s on opposite ends of the world crash on the same day from the same problem.
If I sound a bit “exercised” over this event – that is because I was, and I still am. I was, shall we say, "very close" to the operations of that company and their training/checking program. The accident investigation was, in my opinion, very loosely conducted and, again in my opinion, willing to over-look key pieces of information that didn’t fit with the conclusions ultimately reached. For what its worth, I am grateful that the issue of deicing procedures and hold-over times have been significantly overhauled and are much better understood and respected today – at least that knowledge has been of benefit to this industry.
And, by the way, I would whole-heartedly support a measured acceleration method (from an INS or any other unaffected source) as you have suggested, in the hope that it would deter or reduce such accidents. The reason I don’t say “cure” such accidents, is that as long as we have humans in the loop, I believe we’ll be prone to suffer human failings.