Posted on 03/20/2019 6:17:38 AM PDT by central_va
I have about 200+ hours in single engine and some instrument time though I never got that ticket. VFR for ever.
Ok, let me ask you pro's: Even if the elevator trim is jammed nose down (FOR WHATEVER REASON!) in a commercial jet and cannot be neutralized ( FOR WHATEVER REASON) can human strength overcome that and pull the nose up anyway?
Can someone please answer that question?
If the above is true then if somehow locked in the nose down attitude then I can see how manual inputs would not work. Do I have that right?
The slot shows total trim adjustment. So if you imagine the whole horizontal stabilizer leading edge up then you can imagine how little the full back on the yoke elevators trailing edge up can do to counter it.
Probably just creates a pocket of turbulence.
Ok, so the whole huge honking thing is moved to trim. No separate trim tab. So manual inputs are overridden by the trim mechanism and the in flight computer. Probably the manual inputs pulling the nose up were forcing the nose down even further. The opposite of the desired attitude.
I think the leading edge of the horizontal stabilizer moves up and down with a jack screw.
Thanks, but that was just gleaned from multiple sources.
See #59 for more accurate detail (an excellent outline).
Thanks for that, VTenigma.
logi_cal869, you have made a very important point that is missing in almost all analysis on TV or the internet, although, I disagree as to why Boeing implemented the MCAS system into the 737 MAX.
MCAS is a stall prevention system. Normally, stall prevention systems are only implemented in aircraft that exhibit bad stall characteristics. For example, the F-104 had a stick pusher because when the aircraft stalled, the airflow over the wing blanked the horizontal stab and the aircraft could not recover. The pilot's only option was to eject.
Other aircraft have stall prevention systems because they are so aerodynamically clean that they don't exhibit any classic stall indications as the aircraft approaches stall, such as wing buffet, wing rock, nose rise, or nose slice. The only indication of stall is when the aircraft departs controlled flight.
So, the first question I would ask Boeing is: Why did you have to put a stall prevention system into the MAX? And the second question is: When did you discover the need for a stall prevention system in the MAX?
My guess is that the MAX has excellent aerodynamics and does not exhibit the classic stall characteristics and this is why MCAS was added. I also believe this was discovered late in the program, probably during flight test.
I am incredibly critical of Boeing for this major engineering failure
I could not agree more...but I also believe upper management dictated the lowest cost solution to the problem and therefore shares in the blame.
Season 1 Episode 7—Dr. David Banner attempts to land a 747 only to find he must partially transform, calling upon the strength of the Hulk to overcome a damaged hydraulic system.
Perhaps the new engine placement alters airflow around wing under high angle of attack? How would flaps affect center of lift?
Driving truck all night, then attempting some humor (when severely fatigued) while posting a comment (#13), sometimes is regrettable. Especially in light of the recent tragedy. My apologies to whoever.
Yes commercial aviation has a great safety record. “But for the loss of the nail the shoe was lost....”. It only takes a small failure (mechanical or human, or both) to cause a big disaster.
I’m glad that I survived my “adrenaline junkie” years. There is something about becoming a father that changed my mindset over 38 years ago. It was as if I was looking at things through a whole other set of eyes.
(I suppose my mother’s passing last month has reinforced my focus lately on what is REALLY important. And it’s not some silly hobby of mine.)
God bless
Everything I’ve read is rather anecdotal, as is my experience. My first calling was aeronautical engineer and F15 driver, but neither happened. Still, the interest kept me keen to the evolution of aeronautical design.
When I read that the 737 MAX was NOT a new plane but a redesign - smaller wing and bigger engines on the same airframe - I was not alarmed. The fact that the pilots I know are not concerned demonstrates a distinct dichotomy between what we know of the planes here in the US (no reports that I’m aware of filed with the FAA regarding MCAS problems) vs. the experience of these foreign pilots in the same aircraft.
A technical article I read early on stipulated that there was a single AOA sensor feeding data to the MCAS system and it is that engineering that I cited as a failure. If there are two sensors as another FReeper cited, then certainly there are more serious issues at hand. Everyone interested in aircraft knows of the problems they had with stable flight in the early F22s (oscillation from pilot input); this could be a similar scenario. However, what concerns me are the repeated citations of “training”.
If a pilot has to disengage a safety system which was installed for reasons that remain unclear, well...you aptly-outlined the concerns and I agree.
My hunch is that the wing is too small (designed for fuel efficiency) and that the engineers were afraid the planes would be prone to stalling...harkening to your other question.
Certainly ‘something’ showed up in flight testing which prompted the addition of MCAS.
Still, I’m not aware of a single incident in the US as described overseas other than pertaining to the autopilot alone; that’s a curiosity.
I never want to fly in a commercial airliner again. This is crazy.
Bada bing, bada boom!
I have a buddy is a FAA controller since Reagan fired the slackers. The entire shutdown from 9-11 and gradual rebuild and overtaking of the traffic volume before 9-11...so many people. I watch em zooming over the plains every day.
I’m good right here.
A good test for me would be if you can fly a commercial aircraft from take off to landing with all auto pilots, computer assistance etc. off with only human input then you have an aircraft. If you can’t then what you have is a contraption.
That is possible.
How would flaps affect center of lift?
How do you measure center of lift ?
How many aircraft have had the original 'engines' replaced with more powerful 'engines' throughout history ????
Do pilots simply jam the pedal to the metal during takeoff , or do they use the proper amount of 'thrust' to achieve takeoff ?
When you drive a high performance car, do you just floor it on takeoff, or do you use a reasonable amount of 'thrust' ? Do jet engines just automatically go to maximum thrust on takeoff or does the pilot control that, based on the 'weight' (amount of passengers and fuel) and wind speed/wind direction/altitude of airport, etc. ???
If the engines provide TOO much thrust (regardless to pilot input), why doesn't every 737MAX crash upon takeoff ?
If being 'over-engined' was a problem, there would have been millions of air-crashes over the past 200 years. Usually, higher powered engines are installed in aircraft to increase fuel efficiency.
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