FCeng84, thanks for the very useful aerodynamics lessons. Joining others, we may be jumping ahead somewhat in our assumptions about the Ethiopian and indeed Lion crash but I personally believe that having now turned-over the MCAS stone the issue must be addressed, regardless of it's (non) role in recent accidents. Some (random) questions/observations:

Before the pilot world knew about MCAS, how would an MCAS failure have been manifested? Should it have been an 'MEL' Item? In other words, if it was not visible/known to pilots, how would anyone have known the system was working? Consequently, was it just looked upon as a sticking plaster necessary to get over a certification requirement and something that didn't need to be monitored or even in place for real world operations? I'm reminded of VW diesel engines and emission tests.

What was the rationale behind only using a single data source to the MCAS?

I think it has already been addressed but, does the flight regime mean that MCAS will activate at/before/about the same time as the stick shaker?

How did Boeing come to the conclusion that a 5 second pause after pilot trim inputs was the MCAS reset period?

Sorry for the thread drift, but as it is mentioned very often in this thread for obvious reasons and I can't find the original thread, can I ask - was the cause of the Lion Air crash actually determined or are definitive answers still awaited? Apologies again.

Last night's Rachel Maddow show on MSNBC quoted reports on the Aviation Safety Reporting System, with US pilots reporting uncommanded nose-down problems with the MAX just after take-off, solved by switching off AP.

It's been happening in the US too.

Edited to add: she reports that there was a five-week delay in implementing the software fix...because of Trump's government shutdown. Also, there's still an 'acting' head of the FAA, because that's yet another role that Trump hasn't filled. He wanted his personal pilot to get the job, but didn't get his way. The FAA seems to have issues.

"NEW: https://twitter.com/Boeing CEO Dennis Muilenburg spoke by phone with TRUMP this a.m., urging him not to ground 737 Max 8s after Sunday’s crash. * Muilenburg has tried to cultivate Trump. He visited Mar-a-Lago after AF1 dust-up, & Boeing donated $1M to Trump inaugural.'

Once bitten, twice shy... or NOT?


We pointed earlier ( post no 899 ) that Amsterdam and Lion Air accidents were in part due to single channel/sensor.

In fact on 31 July 2009, Boeing informed airlines about a future Service Bulletin that they are going to rectify the situation in regard to Amsterdam rad alt problem by a comparator function between the measured heights of the left and right radio altimeter systems.

https://books.google.com.tr/books?id...terdam&f=false

P.S. related page 130 bottom part.

Bear in mind that ADS-B altitude granularity is 25ft, you won't see smaller increments than that. So it may only have dropped by a few feet but that is rounded to -25ft.

Also the altitude reported in ADS-B depends on the message type being parsed; some use the barometric pressure from the Mode-C source to calculate altitude per 1013hPa*, whereas others use the GNSS height corrected to WGS84. There's no AMSL data from ADS-B.

* aircraft at my local airport regularly land at -200ft per message type 7

Now those with long memories may recall another overstretched aircraft, the MD-11. That, too, got a "clever" bit of software to overcome design aspects. LSAS. Longitudinal Stability Augmentation System. Even the name sounds similar to MCAS. Did one of the onetime McDD engineers who stayed on after the Boeing takeover have anything to do with the more recent concept.

And again, those with long memories will recall that the MD-11 had a hull loss rate substantially out of kilter with norms, and was well known for ending up on its back and burned out alongside the runway on landing, exactly at the point where LSAS had been designed to kick in.

There were even discussions about it on PPRuNe at the time. One who seemed to understand its technicalities wrote "I seriously wonder if the FAA would be as accommodating now". Hmmm ...

https://www.pprune.org/tech-log/406681-md-11-lsas.html

Yes, although AFAIK the altitudes on FR24 always come from Airborne Position messages, which in turn always contain baro alt.

And of course if you know the QNH and altitude, as we do in this case, it's straightforward to apply the appropriate pressure correction to work out AMSL.

I think I remember forgetting this before... but as it appears that some of the problems with the 737 Max 8 seem to stem from overextending/overevolving an old-ish plane with short legs, why didn't Boeing develop the 757 instead. More modern plane, longer legs (taller u/c) etc?
Genuine question.

I wasn't thinking about the Amsterdam crash (which had a lot of other factors) but had a similar train of thought, given that a failed AoA sensor appears to cause serious trim issues, why not have a comparator between left and right AoA. If values are outside parameters, set trim to neutral, maintain AT (Reducing thrust will reduce nose up moment but pilots are familiar with this on 737) and climb which isn't perfect but seems to be a damn sight better than the current situation.

Where are the recorders at this very moment? Seems the US want them for their NTSB from AAIB?

Because this means your total architecture needs to be different, with computers comparing signals and reverting to different flight laws with failures, as in FBW on Airbus and newer Boeing types (777, 787). This would require the entire system to have to be recertified and it no longer being type compatible with older 737's.

My guess would be Paris. The NTSB will probably have someone there while recovering the data.

The public search engine on the ASRS is dire (hopefully airline safety departments have better access), so I've only been able to find one of those incidents so far:

https://cimg1.ibsrv.net/gimg/pprune....b88a89ec56.jpg

By my understanding that's a bit of a simplification... and most T tailed aircraft tend to have that characteristic, as with the Comet and fatigue, the 1-11 just happened to be the first to fly in that regime.