Ethiopian Airlines Crew Followed Procedures Before Boeing Max Crash, Early Report Says (latimes.com)

The pilots of a doomed Ethiopian Airlines jet followed all of Boeing's recommended procedures when the plane started to nose dive but still couldn't save it, according to findings from a preliminary report released Thursday by the Ethiopian government. From a report: The plane crashed just six minutes after taking off from Addis Ababa, killing all 157 people on board. The report, based on flight data and cockpit voice recorders on the Boeing 737 Max 8, was not released in full. Boeing declined to comment pending its review of the report on the March 10 crash. The Max 8 has been under scrutiny since a Lion Air flight crashed off the coast of Indonesia under similar circumstances in October. Thursday's revelations raise questions about repeated assertions by Boeing and U.S. regulators that pilots could regain control in some emergencies by following steps that include turning off an anti-stall system designed specifically for the Max, known by its acronym, MCAS. Investigators are looking into the role of MCAS, whose functions include automatically lowering the plane's nose to prevent an aerodynamic stall. The Max has been grounded worldwide pending a software fix that Boeing is rolling out, which still needs to be approved by the Federal Aviation Administration and other regulators. Further reading: Flawed Analysis, Failed Oversight: How Boeing, FAA Certified the Suspect 737 MAX Flight Control System.

Comments

Boeing Deserves to Pay for This

[EndlessNameless]

So, to summarize:

1. Boeing self-certified that pilots certified in type did not require additional training. (Prior to the recent deregulation, they weren't allowed to self-certify.)

2. Pilots had to break out the manual during an emergency to properly control a system they were not trained to use.

3. The system either did not disengage properly, or else it reengaged automatically, contrary to well-established norms for this aircraft type.

Boeing screwed up, but it also happened because of relaxed oversight. The previous level of oversight seems more appropriate.

Perhaps the FAA Administrator who made these changes should be forced to resign. This administration has had enough turnover that the President should be capable of appointing new leadership quickly.

Re:Boeing Deserves to Pay for This

[Anonymous Coward]

There seems to be a lot of confusion around how the MCAS system is "disabled" in the case of problems. The MCAS system itself can't be disabled. The procedure for dealing with runaway trim adjustment, a larger umbrella under which problems with MCAS fall, is to turn off power to the electric motors that turn the trim adjustment wheels. These are physical switches that can't be turned on or off without physical contact by someone in the cockpit. The plane can't restore this power, only a person can flip the switches.

Removal of power to the motors prevents MCAS from being able to continue to add more nose-down trim. Unfortunately, most 737 pilots do not turn the trim adjustment wheels by hand when flying, because it is slow and awkward process. They usually use a small thumb joystick on the control yoke to adjust trim, which is carried out by the same electric motors used by MCAS. My guess is that with a bunch of nose-down trim, the pilots turned the power back on so they could make a large trim adjustment with the thumb joystick. But as the pilots add nose-up trim with the electric system, MCAS was again able to counteract that with nose-down trim.

Basically, MCAS can add so much nose-down trim, and do it so rapidly, that even disabling the system leaves the plane in such a nose-down trim that it is unrecoverable. The pilots can't crank the trim wheels fast enough by hand, and turning the electric motors back on gives MCAS the advantage again.

Re:Boeing Deserves to Pay for This

[Anonymous Coward]

Here is an article that states that when the jackscrew that adjusts the horizontal stabilizer is under load from aerodynamic pressure, the manual trim requires too much force to adjust trim. https://leehamnews.com/2019/04/03/et302-used-the-cut-out-switches-to-stop-mcas/

They turned the electric trim back on because the manual trim could not be used.

Re:Boeing Deserves to Pay for This

[slacktide]

The Speaker of the House was Dennis Hastert (R–Illinois). The change which greatly expanded delegated certification was mandated by Congress, not the FAA. It was a part of HR 2115 "Vision 100--Century of Aviation Reauthorization Act" in 2003. Refer to section 227 - DESIGN ORGANIZATION CERTIFICATES. https://www.congress.gov/bill/...

BAD AD

[ghoul]

The AD which went out after the Lion Air Crash said disable the MCAS using cutoff switches. What it did not consider is that if the plane is already nose down then the aerodynamic forces are too strong to use the manual wheels to make it nose up. The AD should have specified use your electric trim yoke switches to make the trim up and then cut out the electric trim so MCAS cannot make it nose down again.
Also why is the MCAS triggering 6 minutes into a flight. Takeoff by definition is close to stall. It should be off during takeoff. If this plane cannot takeoff without MCAS then this plane is not safe. This is not a fighter jet where the pilot can eject if the software screws up or the plane goes unstable.

Re:BAD AD

[wired_parrot]

The AD which went out after the Lion Air Crash said disable the MCAS using cutoff switches. What it did not consider is that if the plane is already nose down then the aerodynamic forces are too strong to use the manual wheels to make it nose up. The AD should have specified use your electric trim yoke switches to make the trim up and then cut out the electric trim so MCAS cannot make it nose down again..

This is a good explanation of the difficulty in trimming the aircraft in a mistrim condition by a former senior Boeing engineer. The short of it is that in the mistrim condition encountered by ET302, with stab nose down and the pilots pulling elevator nose up, the combined tail loads would've produced high jackscrew load opposing nose stab up trim that would be impossible to overcome with manual trim.

Boeing did publish guidance for older 737 models on recovering on a severe nose out-of-trim condition, which would have required taking the aircraft into a roller-coaster maneuver to relieve the horizontal stabilizer loads. But given that they were already close to the ground, this was not an option. The other suggestion was to extend flaps, but given that the aircraft was above the minimum flap speeds, this was also not possible.

In short, it looks like the fix to the problem was as much to blame as the problem itself

Re:Where is the link

[Xylantiel]

Yeah, some the articles don't really give the necessary details. The one I found that really discussed it is this.

Basically it is possible for the MCAS, in combination with other things, to put the airplane in a situation that is not easily recoverable without turning the system that the MCAS is part of back on. This is because the system that bypasses the MCAS isn't strong enough to turn the tail back to the right position. But when the electrical stabilizer system is turned back on, the MCAS just kicks in again and puts it right back in nose-down. There are ways to work it out but they require "non-checklist actions" as the article says. There is no way pilots can figure this out in less than a minute while the MCAS is driving them into the ground. So basically the whole idea that "they could just switch it off" only works in some circumstances. So now we see that it appears even the instructions to pilots were not properly tested.

Re:Terrible plane

[michelcolman]

AF 443

Pilot error, and a hair raising one at that

Simultaneous overspeed and stall warnings (making the pilots believe they were in a high speed stall). Stall warning that shut up at low speed (below 60 kts) but came back on precisely when the pilots were temporarily taking the correct action, making them believe that pushing the stick was the wrong thing to do. Pilots that cannot feel what the other pilot is doing with the stick. With all the simultaneous warnings and inconsistent indications, they had no idea what information to trust anymore. Sure, with perfect hindsight it's easy to see what they did wrong, but it wasn't as clear cut as some seem to believe.

The Paris Air Show lawnmower, AF 296

Ah, I see, you are a conspiracy nut. The envelope protection saved almost all lifes back then when the pilot actively tried to kill everyone by stalling the aircraft. Without the protection the plane would have fallen from the sky like a bloody brick, not slowly gliding on the top of the trees.

They were actually trying to demonstrate the stall protection, by flying extremely slowly right at the edge of the stall (which no pilot would ever attempt in a regular plane). The big problem was that the engines did not spool up as quickly as the pilots had expected. The conspiracy theory is about why the engines took so long to spool up: some say they got into ground idle due to a programming error, some say it was because the pilots had pulled certain circuit breakers, some say flight data recorder info was falsified, etc... I have never really dug in to the whole story, but the theories are not as nutty as they would seem at first sight.