OT 737 Max Really interesting


https://www.youtube.com/watch?v=H2tuKiiznsY

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Yes why? What who where? Brian
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On Sat, 20 Apr 2019 08:19:34 +0100, "Brian Gaff"

Oddly enough there aren't any Brian.
Difficult to believe is it not?
Anyway, an interesting clip and it's difficult to believe how in such a safety oriented industry a software fix like that should get through.
You would also expect multiple fail scenarios to be tested for on transducers, possibly the weakest link in any control system.
AB
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On 20/04/2019 08:39, Archibald Tarquin Blenkinsopp wrote:

As they fitted much larger engines the CofG moved non optimally forward. The SW fix was meant to compensate. The new design is flawed. I'm guessing it will have lower efficiency as well being way out of balance. The A320 was built from the ground up so will always be the superior plane.
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On 20/04/2019 08:56, Andy Bennet wrote:

Moving the CofG forward would cause the nose to dip rather than to rise leading to a stall. However if the centre of forward thrust is below the centre of drag then use of more powerful engines on full power would cause the nose to rise more than before. I think it was that that MCAS was intended to stop.
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Michael Chare

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On 20/04/2019 15:34, Michael Chare wrote:

Well, yes and no.
A forward C of G requires up trim to compensate which means power on nose up is the order of the day. However I dont think this was the issue. Thg issue was that the engines were angled up for ground clearance
However if the centre of forward thrust is below the

And the angled thrust line
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Not ANGLED up, mounted higher so that the top of the engine is actually above the top of the wing.

There is no angled thrust line.
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wrote:

No it wasn’t. The A320 neo is identical in concept, the original A320 with new bigger engines. The difference is that it has longer legs so it fits in the same position on the wing without scraping on the ground. https://en.wikipedia.org/wiki/Airbus_A320neo_family
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Well I have now viewed it and it says nothing not already reported widely does it. I guess as we hear all too often it takes people to be killed for 'lessons to be learned' Until the next time of course. Many many years ago there was a cartoon in Computer Shopper of a plane hurting toward the ground the pilot and co pilot having ejected with the caption saying. I told you those curly brackets were important. Brian
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Been like that for a long time now in that industry. The Airbus will only do what you tell it to do when the software has decided that it is a sensible thing to do in the circumstances.

Don't need fail scenarios to realise that using just one of the angle of attack sensors makes no sense then there are two.
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Actually I was poking fun at Harries eternal tendency to put no explanitory text whatsoever on his links. I still don't know what is on the end of the link since I do not click them without some knowledge that for a start it has sound and is safe. Brian
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On Saturday, 20 April 2019 18:24:55 UTC+1, Brian Gaff wrote:

Well then you'll never know will you, so stop whinging on.
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On 20/04/2019 07:59, harry wrote:

I wasted 5 minutes of my time watching this video, which said absolutely nothing that hasn't been in the newspapers in recent weeks. It totally failed to raise important issues such as:
* The FAA has pretty much abandoned inspecting planes itself, relying on self-certification by the manufacturers. That's working out well isn't it?
* It seems amazing that a single sensor failure could be allowed to cause a plane crash and that not a single engineer at Boeing thought about this. Someone working there *must* have noticed but, presumably, the company squashed their concerns.
* The Boeing response is, apparently, to wire both sensors (there have always been two) to both flight-control computers, so that if they disagree a warning light comes on (plus some other minor software changes to make it slightly easier to disengage the MCAS). This seems wholly inadequate to me. Surely such sensors should be at least triplicated so that if one sensor disagrees with the majority then the computers will be able to work out which ones are accurate?
* These failures have some similarities to the crash of AF447 in the Atlantic off Brazil a few years ago, except in this case it was the pitot tubes which failed. Here there were two of them, but both of them iced up and therefore failed around the same time, so even a duplicated sensor system was no help. There are other ways of estimating airspeed without pitot tubes but the manufacturers didn't bother to program them in - their solution to the problem was for the autopilot to refuse to work, on the assumption that all pilots are competent to take over in emergency. The relevance of this to self-driving cars must also be obvious to most people, since they are, apparently, also being programmed to simply give up and hand over to a human when they encounter a situation that they can't handle, even if that human has just been woken up from deep sleep.
So, Harry, what in particular made you think that this trivial and superficial video would be interesting to this group?
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Clive Page

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Clive Page wrote:

But harry likes the pretty pictures ...
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wrote:

Not that I'm normally interested in the rubbish harry posts, I find it sums up the position that certainly wasn't covered in the stories I read.
The keen competition with Airbus for one.
The push to get things through before a proper engineering test and appraisal is common in all industries, they do compensate for a lack of Engineering standards with reams and reams of useless paperwork though : -)
I did think that the aircraft industry was immune, with multiple fail scenarios being tested. Hence the ban on mobile use and certain electronic items on aircraft.
Boeing policing itself was covered all right, but I think the video puts things neatly into perspective.
Nothing like a bit of light touch regulation to advance industrial progress what?
At least post Brexit Airbus can have full access to a country where they can compete on a level playing field.
AB
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wrote:


https://www.youtube.com/watch?v=aoNOVlxJmow

shows two commercial pilots in a 737 simulator trying to cope with the situation both crews in the crashed aircraft faced and the manual effort required to try to overcome the two aircrafts ultimately successful attempt to destroy themselves. For once newspaper reports of "wrestling with the controls" appear to be much more accurate then normal.
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Peter Parry wrote:

Supposedly those two "stab trim" switches remove all electrical power from the jack screw, so would stop the plane from fighting ...
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wrote:

No, the aerodynamic force on the elevator and stabiliser effectively locks the jackscrew and manual wheels. This is a separate problem with the 737 which has been known about since the early 1980's. The remedy for runaway trim is the "roller coaster" manoeuvre where the aircraft controls are relaxed to allow the aircraft to go where it wants so removing the aerodynamic force on the elevator and stabiliser and allowing the trim wheel to be turned a bit. The manual trim wheel is then held by one pilot while the other pulls back on the control column to regain a bit of height before repeating the process several times to allow the trim to get back to a more normal position (assuming you don't hit the ground first).
The electrical trim switches are disabled when MCAS is turned off and unfortunately if turned back on to try to use electrical power to trim the aircraft also turn MCAS back on. This has greater mechanical authority than the control column.
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Peter Parry wrote:

The ops manual says if you have to use the stabiliser trim cutout switches during a flight, you should never turn them back on during that flight, apparently the Ethiopian Airlines pilots made that mistake.
This chap has flown 727, 737 (but not max), 757 and 777, he has several videos on the 737-max which are worth a watch ...
<
https://www.youtube.com/watch?v=9Ts_AjU89Qk

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wrote:

It would appear they had little choice if the manual trim was (as far as they were concerned) jammed. It takes several dozen turns of the trim wheel to go from full extension to neutral flight and as the airspeed increased the force on the jackscrew would increase. Failing to fully fix the trim before MCAS is deactivated can make it physically impossible for pilots to control the plane. Remember even the existence of MCAS didn't appear in any manuals.
The switch operation was also altered, with the 737NG autopilot cutout switch, you could have turned off autopilot and retained electric trim via yoke switches. However, on the 737 MAX, they changed the cutout switches into primary and backup, and the instruction is to switch both, which means for MCAS runaway, you lose electric trim altogether whereas on the earlier aircraft you could keep trim power operation and only lose the autopilot.
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