skybluesea

delete

5mm

skybluesea

delete

robsaw

"How many" is an irrelevant question without going back to root cause analysis.

100 crashes with 100 different root causes would be extreme but far less rationale for fleet grounding than 10 crashes with 10 similar root causes.

Aviation safety is a science and the issues with the 737MAX need to be addressed scientifically not emotionally.

RangerNS

True, when considering permanent grounding.

That depends on the root cause, then. If there are 100 different design and build related root causes then the fleet should be grounded because the engineers and builders are grossly sloppy. If there is one design failure that was resolved, and 99 failures related to maintenance, then that is a situation entirely.

If in the 10/10 cases were bad maintenance, and it turned out to be simply sloppy maintenance, then that is different then it turned out to be unclear maintenance manuals.

5mm

No, the AF flight crew did not loss control of the aircraft. They got false air speed reading because of icing and cut back the power to the engines to slow the aircraft down. This caused the aircraft to loss elevation and crash into the ocean. This crash should have never happened if the pilots were on the ball.

Also, only one A330 was lost this way. Just like the MAX, the aircraft was not grounded. It was only ground after the second aircraft crash.

WildcatYXU

The loss of AF447 is classified as "Loss of control" . They never cut the engine power. The PF started to climb despite the PM telling him not to. They eventually stalled the aircraft and never realized it. And yes, the Pitot tubes on the accident aircraft were about to be replaced. Just the replacement program slowed down for some reason.

More info and the investigation report can be found here: https://aviation-safety.net/database...?id=20090601-0

expert7700

Airplanes and cars are both designed by humans working at for-profit companies. Subjected to management demands, customer demands, competition, and regulators issuing certification.

Boeing stripped out MCAS from the user/training manuals, and got FAA certification for only 0.6 degrees of MCAS trim but later setting it to a value of 2.5 degrees (repeats quickly to become 5 degrees).

A little bit like Dieselgate where Volkswagen and Bosch engineers colluded and hid code within millions of lines. (researchers later found they named it acoustic mode when it really sensed if the car was being emission tested and was only compliant during that one scenario instead of regular driving.)

If my car analogies are no good here is someone else's They posted in light of the frightening news that ET pilots actually DID disable the cutoff switches per Boeing's tech bulletin.

from pprune user @memberberry
https://leehamnews.com/2019/04/03/et302-used-the-cut-out-switches-to-stop-mcas/#more-29790

This throws the notion that Western pilots would not have crashed, or that Air Canada 737 pilots would not have crashed because they were trained only on the MAX (not the 737NG) out the window.

I suspect that if one of the ~100 North American MAX planes had an AOA sensor fail, they would have crashed as well. In fact, some have questioned if the FAA's approval of repositioning / ferry permits were an unreasonable risk.

RatherBeInYOW

When it was posted it was baseless speculation. The only people who acted on any evidence for grounding the MAX was the FAA and TC, and that was after several days. But people were ready to hang the plane out to dry before anything was known at all. Just because some people happened to be right doesn't mean it was baseless speculation, it was by definition exactly that.

For ET we know MCAS was engaged, what combination of issues caused the crash isn't known by anyone. There isn't even a preliminary report issued yet, let alone a final report. Every single bit of this is baseless speculation. But go ahead and keep running around like chickens with your heads cut off.

canopus27

I'm still waiting for more news to drop about the sensors. Keep in mind that the Indonesian plane had the physical AOA sensors changed prior to the incident flight, so it seems very unlikely that the fault was in the physical sensor.

There's some interesting speculation on pprune that the problem could be electronic signal interference of some kind; there's an early (and thus unverified) report that the Ethiopian flight had a very similar failure mode in the AOA sensor - both sensors were off by "about 22 degrees". ref: https://www.satcom.guru/2019/03/ethi...s-to-lion.html

If that turns out to be true, and there is a systemic cause to the AOA failure, then it will require even more work to correct (in addition to the MCAS s/w fix) -- and it would be indicative of at least two distinct design flaws that escaped into production.

One design flaw escape is an unfortunate occurrence. Two is indicative of a systemic testing failure, and opens the door to there being other flaws in the plane which are as yet undiscovered.

Yes, there's a lot of "ifs" and speculation involved here .... but it may well be the case that MCAS is not the only problem with the MAX.

CZAMFlyer

Does anyone recall a time when 30" seat pitch, mini ovens and some tiny lavs were the only problems with the Max worth mention?

yulred

WildcatYXU

Well, according to Bjorn Fehrm they didn't really have a chance to save the day. They were fast due to completed checklist, they shut off the electric trim after MCAS kicked in and trimmed the aircraft down. Apparently hand trimming is very difficult at high speeds.
https://leehamnews.com/2019/04/03/et...-to-stop-mcas/

yulred

The Lev

[the Seattle times does a good job of explaining what Bjorn Fehrm is getting at in layman's terms...
https://www.seattletimes.com/busines...iopian-flight/