737 Max - oh crap!

[Adam the Akrodude]

Perhaps I'm jumping the gun a little (so what's new you chant!) but it's looking like that MCAS software could be the cause of those Lion Air and Ethiopian Airlines crashes. This is appearing to be a classic case of a string of errors/decisions resulting in disaster. We sure are a imperfect species. That large impact crater in Ethiopia is shocking.

Software that commands a pitch down to near vertical from low altitude - not a great feature! This is another example of how endless mod's can so drastically change the flight characteristics. I recall how the Mk.1 Spitty was near perfect below 250 kts. Later marks became heavier and heavier and more than doubling the horsepower and yet the wing stayed much the same (not including that laminar flow wing on the last type). I was once advised that the early 737s were the nicest to fly and particularly land. By the time the 737-8 appeared, it's landing is more like a "arrival" apparently - just plonks down. Some big changes with the 737 Max - bigger engines mounted further forward and angled up, all helping efficiency, but it appears flight characteristics have changed significantly.

Of course there are other factors including crew currency on type and experience in general. Perhaps a more switched on crew would have avoided these accidents - who knows until the final report comes in. If this report is true, Boeing is in for a world of hurt over this. My thoughts go out to all those onboard those two flights.

https://www.seattletimes.com/business/boeing-aerospace/failed-certification-faa-missed-safety-issues-in-the-737-max-system-implicated-in-the-lion-air-crash/?fbclid=IwAR1NpQ6K-qWCpbpSXvDoNhiqTdq4bEeMnEGd5qUw_twKl3IMvq7Y7uXY2_M

[erussell]

This is the most reasonable analysis I have seen...........

THE EXPECTED CHANGES TO MCAS SOFTWARE ON BOEING 737MAX
Following the two crashes of MAX 8 jets, Boeing is back with the software developing team to update the MCAS software. MCAS (Maneuvering Characteristics Augmentation System) software was designed to swivel the horizontal stabiliser to push the nose pitch down to avert a stall.
The updated MCAS software, will now give the system input from both angle-of-attack sensors. Currently it takes only from one angle of attack sensor) – MCAS will limit how much it moves the horizontal tail. Currently it moves four times faster than was stated in the initial safety analysis document. The new software will limit MCAS to kick in only for one cycle, rather than multiple. Currently it kicks in multiple times as long as it senses AoA change) Flight data retrieved after the Lion Air crash indicated a faulty AoA sensor, that triggered MCAS multiple times during the flight before it crashed. Like all 737s, the MAX actually has two AoA sensors, one on each side of the fuselage, but MCAS was designed to take a reading from only one of them. A software engineer said in a trail of tweets, the crashes were an “Economic problem. Boeing sells an option package that includes an extra AoA vane, and an AoA disagree light, which lets pilots know that this problem is happening. Both 737 MAX that crashed were delivered without this option. No 737 MAX with this option has ever crashed.

Here is an analysis of what has happened from Dave Kammeyer who’s a pilot, software engineer and deep thinker

Bottom line don’t blame software - that’s the band aid for many other engineering and economic forces in effect. Some people are calling the 737MAX tragedies a software failure. It's not a software problem. It is a series of related problems

ECONOMIC The 737 lost out to Airbus for some contracts as 737 engines used too much fuel, so they decided to install more efficient engines with bigger fans and make the 737MAX.

AIRFRAME They wanted to use the 737 airframe for economic reasons, but needed more ground clearance with bigger engines. The 737 design can't be practically modified to have taller main landing gear. The solution was to mount the engines higher and further forward.

AERODYNAMIC The airframe with the engines mounted differently did not have adequately stable handling at high AoA to be certifiable. Boeing decided to create the MCAS system to electronically correct for the aircraft's handling deficiencies.

SYSTEMS ENGINEERING. Boeing wanted the simplest possible fix that fitted their existing computer systems architecture, so that it required minimal engineering rework and minimal new training for pilots and
aintenance crews. The easiest way to do this was to add some features to the existing Elevator Feel Shift system. Like the EFS system, the MCAS relies on non-redundant sensors to decide how much trim to add. Unlike the EFS system, MCAS can make huge nose down trim changes.

SENSOR The AoA vane on the 737MAX appears to not be very reliable and gave wildly wrong readings. On the LionAir flight this was
compounded by a maintenance practice problem. The previous crew had experienced the same problem and didn't record the problem in
the maintenance logbook. This was further compounded by a pilot training problem. LionAir, pilots were never even told about the MCAS! By the time of the Ethiopian flight, there was an emergency AD issued, but no one had done sim training on this failure. This was compounded by another economic problem. Boeing sells an option package that includes an extra AoA vane, and an AoA disagree light, which lets pilots know that this problem was happening. Both 737 MAXes that crashed were delivered without this option. As noted above no 737MAX with this option
has ever crashed.

PILOT EXPERTISE If the pilots had correctly and quickly identified the problem and run the stab trim runaway checklist, they would not have crashed. Nowhere in here is there a software problem. The computers & software performed their jobs according to specifications without error. The specification was just shitty.

The quickest and cheapest way for Boeing to solve this mess is to call on the software guys to come up with another band-aid. Software engineers are sometimes called on to fix the deficiencies of mechanical or aero or electrical engineering, because the metal has already been cut or the moulds have already been made or the chip has already been fabricated so that the basic problem can't be solved. But the software can always be pushed on to the update server! When the software band-aid comes off in the wind, it's tempting to just blame the band-aid!

[erussell]

A bit more.............
https://www.nytimes.com/2019/04/08/busi ... -max-.html
I don't think I would go in one even with the latest band-aid!

[F-27pax]

The possibilities of dying in an airliner crash are so slight that I nornally wouldn't think twice about flying. But the problem of the MAX seems to me to be, in some ways, similar to the problem when jet airliners started flying and Comet's started falling out of the sky - the result of trying to break new ground without quite understanding all the problems involved. The MAX problems seems be in using software to overcome an aerodynamic problem, which might be alright for military aircraft in which instability is a good thing, but not so good in airliners. This is probably the end of the 737 story and I imagine that the folks at Boeing are rapidly rethinking their 797 plans to bring on a 737 replacement. Meanwhile, the folks at Airbus must be jumping up and down with glee. I've forgotten it, there's a word for taking pleasure in the misfortune of others.

[Ansett A330]

I've forgotten it, there's a word for taking pleasure in the misfortune of others.

Of course it's a German word (DON'T MENTION THE WAR!) :

https://en.wikipedia.org/wiki/Schadenfreude

[scotty100368]

The recent events leading to this have cost over 300 innocent lives. Schadenfreude would be most disrespectful in this instance.

[Ansett A330]

Schadenfreude would be most disrespectful in this instance.

But that's just it - the type of person that Schadenfreude appeals to would not have any respect for anybody (de-humanisation) or anything (ideology) other than the worst examples of both in human nature.

So it may be a fair bit over the top to label personnel in Airbus and Airbus as an Organisation as possibly experiencing this feeling.