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?
It took about five minutes from failure to crash. They fought all the way down.
You may not have 6 minutes in that situation.
A commercial aircraft does not utilize direct input to control surfaces. Hydraulics & mechanics - in some cases electronics, aka ‘fly by wire’ - move control surfaces based upon pilot input. Some older models still utilized cables, but in the case of the elevator, depending upon the model the elevator is primarily controlled by a mechanism called the jackscrew, a mechanism with no manual override.
In the case of the 737 MAX - from which I presume your question originates - a single sensor inputs to the computer to determine angle of attack, prompting the computer to override manual input to move the elevator to push the nose down corresponding to sensor readings of the nose angle. The reason for the pitching up & down is rooted in pilot attempts to override the computer, for which it’s now asserted that there are 1 or 2 switches.
If the jackscrew were to jam - as in the case of Flight 261 - the aircraft is doomed. There’s a good video of jackscrew operation at this source I hate to reference:
https://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261
That’s the simple explanation if I understand the nature of your question. The mechanics are the same, T-tail or not.
I’ve mistakenly neglected to click ‘chat’ as well; just ping the moderator to change it.
Ok, why do we pay people to sit in the cockpit if the auto pilot computer is going to kill us like a HAL 9000? Are pilot’s that lazy? I don’t think so.
Flying an aircraft is tiring work. The aviator is constantly in need of adjusting trim to keep the aircraft in level flight. Having an automated system adjust the trim relieves the aircrew from this mundane task and does it far better than a human because it adjusts several times per second whereas humans take several seconds to make one adjustment.
The takeoff, approach, and landing phases of flying are almost universally automated, especially considering heavily congested airfields like Dulles, Reagan National, Atlanta, O’Hare, LaGuardia, LAX, Tokyo, Heathrow, Berlin, etc. where flights arrive every 30-60 seconds. Pre-defined departure and approaches are programmed and executed on command. Far more efficient, but any problem is potentially catastrophic.
Hmmm. Not really buying that one. Auto trim is great but that can be turned off right?
I also have a question. They say that the 737MAX has more powerful engines which are HEAVIER and MOUNTED farther FORWARD than the previous 737’s. They say THAT is what causes the nose of the MAX to tilt up.
HOW does having more WEIGHT moved farther FORWARD cause the NOSE to tilt up ?
Should call the auto pilot the Kamikaze switch?
Everything CAN be turned off, but having to adjust trim manually every couple of seconds over a multi-hour flight takes brain processing power away from routine and safety of flight issues.
What about that is causing you a problem?
I guess at full throttle it is over engined to boot causing a natural rotation around the y axis. At cruise I GUESS the plane is safe. But who the hell knows?
Gee we all have to work for a living. How about fly the damn plane.
To expand, the pilot’s input in the case of the 737 MAX is conflicting with the computer, which was inputting a nose down configuration with the trim motor, if I understand correctly.
Thus pilot input was being offset by the computer. Hence the reports about disabling the MCAS system and cutting power to the trim motor.
If these mechanisms fail, the aircraft is doomed. I understand your concerns, but aside from maintenance considerations, modern aircraft design for commercial travel has proved to be incredibly-reliable. The MCAS system was designed to eliminate the potential for stalling based upon the one variable engineers cannot overcome with aircraft engineering: The pilot. In this case they failed miserably by relying upon a single sensor with no redundancy.
I am incredibly critical of Boeing for this major engineering failure and the consequent investigation will conclude a new chapter in aviation...a chapter which should never have been opened. Before this crash, I was unaware of the severe dichotomy in training between US pilots and foreign pilots.
To your point, I would never willingly fly upon a foreign aircraft without US pilots, but have no bones about flying with US pilots. Of course, I may never fly again commercially due to the TSA, but that’s another matter altogether...
The pilots do fly the plane, but much of the flight can be automated, like the terminal phase where the aircraft MUST meet certain gates in order to be allowed to continue on an approach.
There are probably YouTube videos of commercial flights filmed on the flight deck. You can see exactly how confusing and busy it gets at various stages of flight. We live by checklists and approach and departure procedures.
Aviators must learn how to communicate in a very precise language and listen to specific calls from ATC. Violating a directive from ATC can cost a pilot their wings. Pilots are responsible for the safety of their aircraft but ATC is responsible for the safety of all aircraft on their scope. It is a VERY congested airspace and pilots must be aware of all that is going on around them.
I have never read of such a report. The simple answer is that won’t happen, but the aircraft will handle differently. The change in balance on this model changes the aircraft’s flight characteristics. Apparently the simulators were not programmed for this handling change and a single faulty input to the computer at slow speeds and angles such as during takeoff trigger the computer to force the nose down at low altitude, which basically caused both crashes.
One crash was avoided by a deadhead Ethiopian pilot who knew what to do and saved that aircraft; the consequent flight was not so lucky to have had such a trained pilot either at the controls or in the jumpseat.
Thrust...Lots of it. Perhaps too much?
I am a pilot too. I have flown an SEL with no help what so ever and have on many occasions flown in controlled airspace and have no problem doing that. Hell, I can do it all day long. It’s actually fun. I guess I am weird.
This is the problem. The pilots are not being trained enough on this aircraft on the procedures to disable this functionality. They have to override but are in a panic as to how to accomplish it.
This is a systemic failure. It is a failure of design. A failure of the review process. A failure of the certification process. A failure to train appropriately.
As usual with modern aircraft crashes, it requires a string of circumstances for a crash to occur.
Frankly, somebody gets paid an awful lot to oversee this industry and was asleep at the wheel. There needs to be a formal review, no other aircraft should be attaining certification until we understand, completely, how this aircraft was allowed to go to production.
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