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Originally Posted by warbirdfinder
(Post 10422566)
VESBOT states:
You're mistaken, "climbing" (or, put more precisely) elevator/AOA control always controls speed. Of course, under the likely MCAS scenario discussed, they did not have AOA control and the airspeed was running away from them. And thrust always controls vertical flight path, so if they reduced thrust they would have only hit the ground sooner. In a desperate fight for altitude, "piloting" would dictate maximum thrust. If the above is true, when you are ready for take off, try this: Pump the elevators up and down until you has reached VR, then when you reach VR, shove the throttles to maximum to rotate. |
Does anyone know ETs procedure for Airspeed Disagree? Experiencing that error due to AoA vane failure, would they have simply gone for ex 80% N1, and then Flaps Up to keep bits from coming off? At which point they’re soon rocketing along, MCAS kicks in, and they can’t climb? |
Originally Posted by Chesty Morgan
(Post 10422512)
Yes but reducing thrust on the 737 creates a large nose down moment (pitch/power couple) so as Vessbott stated they would have just hit the ground sooner.
My experience of this is unusual attitude recovery during manual reversing air tests. Reducing thrust, if you're already using everything you have to keep the nose up, WILL result in a further nose down moment and no reduction in speed. They'd have been better off sticking the speed brakes up. And in fact Boeing DO publish this in the QRH. |
Originally Posted by Vessbot
(Post 10422572)
You ever try taking off at idle thrust?
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Originally Posted by Sailvi767
(Post 10422570)
They were at high speed, reducing thrust would have had almost no effect on pitch. It’s done every single day on every airline flight. The stabilizer at high speeds is extremely powerful in control of pitch. Engine thrust is negligible. Are you aware of the relationship between excess thrust and climb angle? How much do you suppose they had if they hit the ground? Pulling the power from takeoff power to cruise power for 250 would not even be noticed. In normal ops maybe 1 click of trim moving the stab .01. I think you are getting confused with recovering from flight near stall with a nose up attitude and high AOA. In that specific situation slamming the power to max will cause the nose to pitch up further because the stabilator has far less control authority. |
Slowing from 320 to 250 at reduced thrust and reduced climb angle is beneficial over slowing from 320 to 250 at full thrust and a steep climb angle,... Why? What is the benefit? When did altitude stop being our friend? Especially when struggling to maintain control and maintain altitude when close to the ground?
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Originally Posted by Ian W
(Post 10422502)
But more speed when your stab trim is too nose down is your enemy. Reduction in speed would reduce the force to counter the nose down trim so 'piloting' would dictate reducing speed.
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Originally Posted by Ian W
(Post 10422582)
In fact the forward and higher placement of the engines that required MCAS because of their aerodynamic lift at high AoA, has also significantly reduced the pitch/power couple as the engines are closer to the vertical midline. In any case the idea is not to get to the full thrust position in the first place. As stated up thread the aircraft might have been controllable in pitch at a reduced speed.
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BEA press release confirming the earlier announcement of the successful recovery of the FDR and CVR data:
https://cimg4.ibsrv.net/gimg/pprune....dec9db8b57.jpg |
Originally Posted by Vessbot
(Post 10422587)
Slowing from 320 to 250 at reduced thrust and reduced climb angle is beneficial over slowing from 320 to 250 at full thrust and a steep climb angle,... Why? What is the benefit? When did altitude stop being our friend? Especially when struggling to maintain control and maintain altitude when close to the ground?
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Originally Posted by Sailvi767
(Post 10422608)
I just realized you’re not a pilot. If they had the ability to get the nose up and trade airspeed for altitude they certainly would have done so. In fact if they had that ability they would have simply climbed out at 250 and never got fast. Your all hung up on thrust causing pitch changes because you read news articles by reporters with zero knowledge. Thrust changes are a non issue at normal speeds! If you have a trim runaway you need to slow down to reduce the effectiveness of the stab and reduce control column loads. L/D max or probably about 215 knots would have been my target airspeed with trim issues. |
Originally Posted by Ian W
(Post 10422594)
Where did the steep climb angle come from? That was their problem
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Originally Posted by FCeng84
(Post 10422616)
Don't forget that slowing to about 250 knots also allows the control system to use full elevator travel. At speeds above that "blowdown" or "blowback" (choose your desired label) occurs and the system is not able to push the elevator to its full travel limits.
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Apologies if already posted
Sensor cited as potential factor in Boeing crashes draws scrutiny March 17 at 7:47 PM https://www.washingtonpost.com/busin...=.b9df74af9cb0 |
Sounds like they were stuck between a rock and a hard place
Reduce thrust - immediate reaction is a slight reduction in pitch due to thrust coupling but maybe they would slow down and recover enough elevator authority to begin a stable climb eventually vs. Maintain / increase thrust - maybe a slight pitch increase to start with but they will gain speed with limited elevator travel and no chance of overcoming the nose down moment from the stab Option 1 probably works nicely at when you have altitude on your side... |
Question for all the pros: if MCAS is supposed to AVOID stalls by putting the nose down, does anyone know how many times it actually DID this on all airlines since it was introduced? Is there some sort of log of when it was activated, and is there any analyses of valid/invalid activation? Or, is this asking too much? Seems to me this would be extremely relevant history.
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"Prosecutors, Transportation Department Scrutinize Development of Boeing’s 737 MAX" https://www.wsj.com/articles/faas-73...d=hp_lead_pos1 |
Originally Posted by Running Ridges
(Post 10422679)
Sounds like they were stuck between a rock and a hard place
Reduce thrust - immediate reaction is a slight reduction in pitch due to thrust coupling but maybe they would slow down and recover enough elevator authority to begin a stable climb eventually vs. Maintain / increase thrust - maybe a slight pitch increase to start with but they will gain speed with limited elevator travel and no chance of overcoming the nose down moment from the stab Option 1 probably works nicely at when you have altitude on your side... |
Automation has been taking over cockpits for decades. Flight engineers have all but disappeared and the second officers filling their seats are gone too, along with the high time, well seasoned first officers who were often more experienced than their captains due to mergers and takeovers. These days, it must feel pretty lonely up there on a bad night with a copilot new to the airplane and the game. Automation, now so essential but not always cooperative or fully understood, only adds to the percentage of recent accidents due to confusion over who or what had control of the airplane.The writing is clearly on the wall. According to at least one source, Boeing believes eighty five percent of all accidents are due to pilot error, and there are those who think the sooner the day comes when the AI does the all work and the pilot does all the cross checking, the better.
The flying public are unlikely to accept security guards and night watchmen minding the machinery however, so real pilots will be with us for the foreseeable future.. Despite the shift in perception, away from the status and prestige of airline pilots in previous generations, they need to be a lot smarter in ways we old stick and rudder guys would never have dreamed of. Know your airplane is as important now as it ever was, but training is apparently too expensive and the task is not made any easier when the builders don’t think the pilots are up to it. Until they can design airplanes with pilots completely out of the loop, they need to be completely within it. Right up until the last one out of the cockpit turns out the lights. |
Originally Posted by Sailvi767
(Post 10422717)
They had a much easier choice, comply with the QRH for runaway trim, disconnect the trim system, manually trim and fly to destination as airline crews have been doing since the invention of electric trim. The billion $ question is: Why went two crews into that deadly trap? |
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