Peter wrote:
There is a lot of precedent for that sort of thing. For example the various CJs up to CJ4 are under the same TR
Yes but there is a requirement for differences training, which is quite considerable. The CJ4 is a totally different thing to fly from a “Classic” 525. I do not believe airline pilots are jumping out of 737-200 and into a 737 Max8 without any additional training.
There are several notable differences between the NG and the Max which start to appear. The one which hit me in the face with a sledgehammer is that they got rid of a stabilizer trim brake which stopped the trim if you moved the control column the other way. That of course is the instinctive thing any pilot will do. On the Max, you can only stop the trim only with the cut off switches (permanently) or with the electric trim thumb switches, which will stop them temporarily but then they will start again.
So the way I see this whole thing is that any trim malfunction, be it triggered by the MCAS or something else, has to be handled very differently on the Max.
So imagine the situation in an NG.
You take off and at about 1000 ft AGL, the stab trim, for what reason ever, starts trimming nose down. You pull on the yoke and that stops it. Now you figure out what is going on and take appropriate action, be it via thumb switch or cutting the trim out.
Picture the same situaation in a Max.
You pull on the yoke to arrest the nose down movement, but that doesn’t do anything, on the opposite, the “system” which ever it is, will reckognize that it is not achieving the result it is looking for and will add MORE nosedown trim, until either someone tries to stop it with the thumb switches or cut off, or they end up in a steep descent without the elevator authority to arrest it.
Add to that, that obviously in the Max the failure of one sensor (AOA) can lead into a situation where the system thinks it is in a stall and begins to trim nose down with increasing energy. This was the reason why the Lion Air plane crashed. Initially they managed to get it under control, but lacking the clear understanding on how to stop the situation, they eventually loose. In the sequence there, the situation at first was brought back under control by selecting flaps 1. Then they apparently retracted the flaps again or they got retracted due to overspeed and they lost control. We don’t know yet about the Ethiopian plane, but the sequence of events appear to be similar.
Add to that that out of trim 737’s who go nose in due to unintended trim conditions are not exactly new. In recent years, 2 NG’s and one 500 came to grief like that. Granted, the reason why this happened is massively different but in the end, the condition the planes were in were similar, in a steep nose down descent with full forward trim on.
So obviously grounding the Max was more than necessary until this is sorted out both on a training and technical level. From where i am sitting, the first thing which needs to change is that the trim brake needs to come back. Then they have to figure out a way for the system to behave in a more controllable manner and, first and foremost, reckognize it is going to kamikaze the plane into the ground. This is not something which will happen overnight. And Boeing appears to have some other issues to resolve too, such as that since the NG, there is an “Option” to have a AOA disagree message, which not every airline paid money to get. Sorry, a warning like that should NEVER be a paid option.
I don’t know. I still have a feeling this is a bit over blown. Two AOA sensors may be more than enough, if they also get some other indication to compare with. Gyros for instance. This system surely is some kind of multi input Kalman filter thing I would think. If I’m not remembering incorrectly, the F-16, which is full FBW, only has two dedicated AOA sensors also, and have had so for 40 years without anyone objecting. It is flyable even when loosing both of them. There maybe something in the software/hardware that fails in certain particular circumstances, but to say it’s a design flaw is a bit over the top IMO.
I reckon you are probably right, although an F16 pilot would be a lot more switched on than some of those who end up flying passenger jets, especially in some airlines around the world.
Some of the routes into a jet cockpit are “interesting” e.g. starting with writing sections of the ATPL QB on the back of the Jepp airway chart (ask anyone who runs an FTO) all the way to being given a free ATPL if you have served as an F4 pilot in the air force (just the TR course is needed; this is reportedly in Turkey, and came out when they deposited one 737 in Amsterdam).
In the news now. Boeing will be installing a software update in 10 days (according to some un-named source at Boeing).
Peter wrote:
Whoops… I knew it!
Smart pointers and valgrind for memory profiling 
, tough in a company as large as Boeing the software code will be buggy as hell (it has to work as management/regulator want it 
)
Articles today on Avweb and The Seattle Times.
Especially this statement in the The Seattle Times article is, um, interesting …
Both Boeing and the FAA were informed of the specifics of this story and were asked for responses 11 days ago, before the second crash of a 737 MAX last Sunday.
Late Friday, the FAA said it followed its standard certification process on the MAX. Citing a busy week, a spokesman said the agency was “unable to delve into any detailed inquiries.”
The fallout from this at both Boeing and the FAA is likely to be substantial.
