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Would it be overly cautious to avoid flights on Boeing 737 MAXs? edit: of course with the downvotes for an honest question. this site can be ridiculous.
Now, that doesn't mean I didn't double check the aircraft types for some upcoming flights flights...
Would it be overly cautious to avoid flights on Boeing 737 MAXs? edit: of course with the downvotes for an honest question. this site can be ridiculous.
Yes. This is a very specific failure mode, and given the publicity of this event, it's not going to catch anyone else out. Now, that doesn't mean I didn't double check the aircraft types for some upcoming flights flights...
Okay, I've never sat in the cockpit of an aircraft, but the one thing I don't understand - if the nose of a plane suddenly drops, isn't the pilot's first instinct to pull back on the controls to raise it? From what I've read, in Boeing aircraft at least, the pilot's controls can always override the automatic systems.
Pulling back on the controls moves small control surfaces (elevators) on the horizontal stabilizer (the "tail wing"). The way the anti-stall measure works on the MAX (and many other planes, to be fair) is by adjusting the pitch trim. Adjusting the trim changes the angle of the entire horizontal stabilizer. https://en.wikipedia.org/wiki/Stabilizer_(aeronautics)#/medi... It's very possible for the effect of the extreme…
So essentially, trim changes the relative 'zero point' of the elevator, and if past a certain angle, even if the pilot applied full nose-up elevator, the altered airflow over the smaller control surface would be unable to counter the altered airflow by the stabiliser itself having been adjusted. I now see why recovery is so dependent on quickly disabling the trim system and resetting the stabiliser to 'true zero'.
Was that three previous flights of the same aircraft? And if so, why was it still in service?
Okay, I've never sat in the cockpit of an aircraft, but the one thing I don't understand - if the nose of a plane suddenly drops, isn't the pilot's first instinct to pull back on the controls to raise it? From what I've read, in Boeing aircraft at least, the pilot's controls can always override the automatic systems.
Pulling back on the controls moves small control surfaces (elevators) on the horizontal stabilizer (the "tail wing"). The way the anti-stall measure works on the MAX (and many other planes, to be fair) is by adjusting the pitch trim. Adjusting the trim changes the angle of the entire horizontal stabilizer. https://en.wikipedia.org/wiki/Stabilizer_(aeronautics)#/medi... It's very possible for the effect of the extreme…
In theory then, solving the stabilizer problem that caused the crash is as simple as flipping both switches to cutoff, then using the wheel to set the stabilizer back to a sane value. Handling a stabilizer runaway is a standard part of US 737 training, and the updated Emergency Airworthiness Directive just says to follow the stabilizer runaway checklist. Again, in theory, this should have been a no-brainer, "common" emergency, and following the usual checklist would have fixed the issue.
However, pilot's mental model of the aircraft has been broken. In the previous generation of 737's, there were exactly two things outside the wheel that could control the stabilizers - the cockpit trim switches, and the autopilot, and each had it's own cutoff switch. Now we have three systems that can control the stabilizer wheels, and the new one doesn't have a labeled switch, nor was anyone told it existed.
Earlier quoted context omitted.
Pulling back on the controls moves small control surfaces (elevators) on the horizontal stabilizer (the "tail wing"). The way the anti-stall measure works on the MAX (and many other planes, to be fair) is by adjusting the pitch trim. Adjusting the trim changes the angle of the entire horizontal stabilizer. https://en.wikipedia.org/wiki/Stabilizer_(aeronautics)#/medi... It's very possible for the effect of the extreme…
That's very informative, I didn't realise the whole horizontal stabiliser itself can be a moving part - I always thought they were fixed and trim was done using the elevator surface. Thanks for the links. So essentially, trim changes the relative 'zero point' of the elevator, and if past a certain angle, even if the pilot applied full nose-up elevator, the altered airflow over the smaller control surface would be una…
On most, if not all, supersonic aircraft they are like that. It was found that the traditional design didn't work well at supersonic speeds, there is debate as to who developed it but the Miles M52 is a likely candidate.
I've had a quick look for a decent video demonstrating it. This one shows it fairly clearly in the 5-10 second segment.
Earlier quoted context omitted.
Pulling back on the controls moves small control surfaces (elevators) on the horizontal stabilizer (the "tail wing"). The way the anti-stall measure works on the MAX (and many other planes, to be fair) is by adjusting the pitch trim. Adjusting the trim changes the angle of the entire horizontal stabilizer. https://en.wikipedia.org/wiki/Stabilizer_(aeronautics)#/medi... It's very possible for the effect of the extreme…
A 737 and a 737 MAX has big wheels in the cockpit that move as the stabilizer trim changes. This lets the pilots see what the autopilot is doing with the stabilizer, and/or override stabilizer changes by grabbing and holding the wheel or rotating it. You also have two switches to disallow control of the stabilizer, one for blocking other stabilizer controls in the cockpit, and one for blocking control by the autopilo…
It doesn't take anything away from what you've said really but there is at least one other system which can control pitch trim. The Mach trim system counteracts changes in the centre of pressure due to speed by making adjustment to the trim.
> Now we have three systems that can control the stabilizer wheels, and the new one doesn't have a labeled switch, nor was anyone told it existed.
Just to add to this point, I believe the reason this was done this way was an attempt to keep the control behaviours of the new aircraft as similar as possible to the old (despite having more powerful lower slung engines) for the sake of maintaining training consistency.
Okay, I've never sat in the cockpit of an aircraft, but the one thing I don't understand - if the nose of a plane suddenly drops, isn't the pilot's first instinct to pull back on the controls to raise it? From what I've read, in Boeing aircraft at least, the pilot's controls can always override the automatic systems.
Earlier quoted context omitted.
>Because jumping to conclusions is not helpful. Let the NTSB do their job and find out what went wrong We are used from previous cases that aircrafts will get grounded until we are sure the airplane is not at fault. So why in the past this happened before the investigation was complete but in this case the risk is considered t be minimal? I am not saying that it is right or wrong but I want to understand the algorith…
We are used from previous cases that aircrafts will get grounded until we are sure the airplane is not at fault. To be clear: you're suggesting that grounding an entire type of aircraft, either worldwide or even just within US airspace, is a common response to accidents? I ask because the last general grounding of a type was in 2013 to remedy the 787 battery issues. Prior to that , the last such grounding was the DC-…
Anyway the question still stands, who and how decides if we should ground some airplanes?