Thank you George. Found a handy youtube video YouTube where a 737 pilot (oddly using a model 747 for illustration) explains it and shows a little video of them spinning. He mentions trim runaway there and scratches the surface of the Boeing design philosophy in that you can see what the autopilot is doing all the time and spot issues before they go non-linear.
Most fascinating for me was how he discussed that you add trim by feel on the column as it was something I had never even thought about. The concept of delicately balancing 70 odd Tonnes flying at 450knots by touch is going to take a little while for me to get my head around
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Most fascinating for me was how he discussed that you add trim by feel on the column as it was something I had never even thought about. The concept of delicately balancing 70 odd Tonnes flying at 450knots by touch is going to take a little while for me to get my head around
.In your link, there is a link to a FAA directive, FAA Emergency AD 2018-23-51 -, on the subject.
Based on the FAA directive, my read of it is the FAA (and Boeing would have to be involved) acknowledges a problem with the MCAS system which can be caused by a faulty AOA reading.
BTW, extracted from the FAA directive
"and possible impact with terrain"
But it doesn't actually mention the Lion Air incident. So maybe a smoking gun, but doesn't blame Lion Air on MCAS and AOA.
Thank you George. Found a handy youtube video YouTube where a 737 pilot (oddly using a model 747 for illustration) explains it and shows a little video of them spinning. He mentions trim runaway there and scratches the surface of the Boeing design philosophy in that you can see what the autopilot is doing all the time and spot issues before they go non-linear.
Most fascinating for me was how he discussed that you add trim by feel on the column as it was something I had never even thought about. The concept of delicately balancing 70 odd Tonnes flying at 450knots by touch is going to take a little while for me to get my head around
Great link - thanks Bill... except he seems to have a lot of interesting videos! Another time burner! Interesting: YouTube
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Most fascinating for me was how he discussed that you add trim by feel on the column as it was something I had never even thought about. The concept of delicately balancing 70 odd Tonnes flying at 450knots by touch is going to take a little while for me to get my head around
Its all a matter of scale. I did the same flying my 1000 pounds ultralight at 90 knots ;-)
Jan
Most fascinating for me was how he discussed that you add trim by feel on the column as it was something I had never even thought about. The concept of delicately balancing 70 odd Tonnes flying at 450knots by touch is going to take a little while for me to get my head around
This is precisely the reason that control feel is so important - it must work as expected, by feel - tactile feedback. In the case of the 747 it's the hydraulic 'feel computer' that's making the yoke react the way the pilot expects, where in Jan's aircraft it's actual control cables and the flying surfaces themselves.
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Unbelievable!!!
I hope this safety feature is a built-in one in future, otherwise the control software makes no sense and should be disabled. As i read, there was no clear description in the handbook to handle this task.
Life depends on an optional extra!! Thanks Boeing
Reminds me of some of those accidents on Air Crash Disaster where the ILS systems at airports were down because they were being repaired. There was one case - one of the Pacific Islands - that had a particularly difficult landing approach but the ILS was turned off. The approach required the aircraft to clear a ridge. A plane load of people on a late night flight slammed straight into the ridge. Final conclusion: ILS not available and pilot disorientation.
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A smaller scale, but still important, is the feel of the lines and wing when paragliding... Immense fun though...
AOA sensor
AOA sensors have been problematic for many years, bug strikes can make them
read incorrectly, icing, etc. Relying on two and picking one randomly seems
to me to be a bit reckless without disconnecting or giving a warning when there are extremely different readings.
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A former Collins Aerospace employee
AOA sensors have been problematic for many years, bug strikes can make themread incorrectly, icing, etc. Relying on two and picking one randomly seems
to me to be a bit reckless without disconnecting or giving a warning when there are extremely different readings.
.
A former Collins Aerospace employee
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What about this then?
May have been some bug that wasn't completely ironed out? At any rate, it seems a recurring problem on that particular aircraft.
Lion Air Report Analyzes Pilot Struggle With 737 MAX Trim System - Avionics
May have been some bug that wasn't completely ironed out? At any rate, it seems a recurring problem on that particular aircraft.
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I remember the early Apollo flights where the flight computer was triplicated. Results from computations were compared continuously, and if one of the three disagreed with the other two, that one was taken off line.
Not 100% fail-safe, but a good step forward.
Jan
Same as I described a few pages back:
That is why I just can't understand why this system would be designed to rely on the validity of one data source.
Well we don't really know whether that is the case, do we? What inputs are used to decide there is a stall danger? Presumably, air speed also is an input, for instance.
Jan
Because if it fails you turn off the trim motors and move the wheel by hand.
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