Ethiopian 737 Max 8 crash and Fallout

[jb747]

Such low retraction makes very little sense...but then you only have to look at Air Asia out of Melbourne to see some strange flap retractions....

It would seem that a number of the holes in the cheese need to have lined up before MCAS activation...but once it does, at low level, then that would seem to be the end of the game. It’s a safety system that has probably killed more people that it ever would have potentially saved. The fact that Boeing are fiddling with the edges of it, instead of removing it, says a lot about the airworthiness of the MAX. Not airworthy without it....and not all that good with it.

 

[MEL_Traveller]

I guess it's possible that the MCAC kicked in - in error - regardless of the altitude or flap setting? If there's an error, the error could be outside the normal intended criteria and scope.

 

[Quickstatus]

I guess it's possible that the MCAC kicked in - in error - regardless of the altitude or flap setting? If there's an error, the error could be outside the normal intended criteria and scope.

Both Max crashes unfortunately has MCAS were outside the normal intended criteria which was to present a new aircraft with flight characteristics identical to the old design such that pilots won’t notice the difference.
......

Can autopilot be activated with flaps down while in Climb in a 737?

Maybe MCAS not involved here. There have been pitch trim related accidents before occurring immediately after take off on other aircraft.

 

[jb747]

Can autopilot be activated with flaps down while in Climb in a 737?

I presume so. In everything that I’ve flown to can be engaged down to 100’ (or so) on take off.

But, engaging the autopilot so low is not a cure for the woes of MCAS. It is very useful in poor weather though.

 

[Quickstatus]

But an AP ON condition prevents MCAS activation?

I’m thinking some Pitch trim issue outside of the MCAS domain is involved

Does the AP turn off in the 737 and give the aircraft back to the human pilot if it can’t manage the aircraft?

The other bit I don’t understand:
If MCAS is designed to alleviate pitch up tendency during high thrust settings shouldn’t MCAS be active during takeoff irrespective of Flap and autopilot setting?

 

[MEL_Traveller]

But an AP ON condition prevents MCAS activation?

Maybe an error is that auto pilot 'on' doesn't prevent MCAS activation.

Interesting to read back on the Lauda Air 004 crash. Apparently Boeing insisted thrust-reverser deployment was not possible in flight. Boeing designed tests and the FAA accepted the outcomes of those tests. This was back in the 1982.

 

[Quickstatus]

Maybe an error is that auto pilot 'on' doesn't prevent MCAS activation.

Interesting to read back on the Lauda Air 004 crash. Apparently Boeing insisted thrust-reverser deployment was not possible in flight. Boeing designed tests and the FAA accepted the outcomes of those tests. This was back in the 1982.

Cant rule that one out either. Or perhaps there was a pitch trim issue outside of MCAS. Has happened before.

While there may be similarities with the JT crash there are differences not alluded to in various reports

 

[jb747]

But an AP ON condition prevents MCAS activation?

I’m thinking some Pitch trim issue outside of the MCAS domain is involved.

That's possible, but then it would most likely present as a normal runaway trim, and that should stop simply by pulling against it. As far as I know the basic trim system has not changed at all...MCAS is the only new item.

Does the AP turn off in the 737 and give the aircraft back to the human pilot if it can’t manage the aircraft?

Autopilots disengage for all sorts of reasons...so basically yes. Even if your cup of tea isn't strong enough.

The other bit I don’t understand:
If MCAS is designed to alleviate pitch up tendency during high thrust settings shouldn’t MCAS be active during takeoff irrespective of Flap and autopilot setting?

MCAS is inhibited by design during take off, and with flap extended. Inhibits are a very normal part of aircraft design. The pitch up tendency is not being caused by thrust, but rather the forward mounted engine nacelles are producing lift at high alpha. If allowed, MCAS would probably activate on all take offs....

Maybe an error is that auto pilot 'on' doesn't prevent MCAS activation.

Engaging the autopilot is NOT a cure for an aircraft that is not in stable flight. They won't even engage unless you're in trim, with zero control inputs. Ethiopian lost another 737 a few years back, when the pilots lost control after taking off at night. An attempt was made on that occasion to engage the a/p... as the pilots had lost the plot.

Interesting to read back on the Lauda Air 004 crash. Apparently Boeing insisted thrust-reverser deployment was not possible in flight. Boeing designed tests and the FAA accepted the outcomes of those tests. This was back in the 1982.

There are generally three different defence mechanisms to guard against in flight deployment. In the Lauda case, one had been u/s for quite some time, and they continued flying the aircraft. Later another played up, and the reverser attempted to deploy, a number of times (and if I recall correctly, over multiple flights). Now, only one line of defence. It was probably only a matter of time for an attempted deployment to occur, and for that last system to miss it.

Cant rule that one out either. Or perhaps there was a pitch trim issue outside of MCAS. Has happened before.

While there may be similarities with the JT crash there are differences not alluded to in various reports

There are now four recent examples of Boeing aircraft suddenly diving into the the ground, from low level. The two MAX, the Fly Dubai 737, and the Texas 767. Curious.

 

[Berlin]

A really good and laymen-friendly summary (I think) of all that has been going on to bring the Max to life:

The emerging 737 MAX scandal, explained

 

[JB expat]

The Dangerous Flaws in Boeing’s Automated System

 

[Berlin]

I don't know that it has been quickly programmed. They have been working on it since LionAir.

Well, even Boeing now admits it was a bit too quick:

Boeing Fix for 737 Max Software Is Delayed

 

[oz_mark]

Well, even Boeing now admits it was a bit too quick:

Boeing Fix for 737 Max Software Is Delayed

Probably a few reasons for that:
1) Possibly some learning's from what happened with Ethiopian that needs to be incorporated
2) Boeing really only have one shot at this - if another one goes down in a way that looks in any way similar, it won't end well
3) The FAA have their issues - remember this is the mob that issued a 'Continued Airworthiness Notification' in the aftermath of ET. What was that about? So, they are going to be going over the changes in great detail

 

[MEL_Traveller]

2) Boeing really only have one shot at this - if another one goes down in a way that looks in any way similar, it won't end well

... and I wonder if it will have any paying passengers on it? (I dunno how many pax will be willing to fly even with a 'fix' - at least until the aircraft has a proven record.)

 

[codash1099]

Probably a few reasons for that:
1) Possibly some learning's from what happened with Ethiopian that needs to be incorporated
2) Boeing really only have one shot at this - if another one goes down in a way that looks in any way similar, it won't end well
3) The FAA have their issues - remember this is the mob that issued a 'Continued Airworthiness Notification' in the aftermath of ET. What was that about? So, they are going to be going over the changes in great detail

And China and Europe will want to do their own assessments. I don’t think they will want to rely on the FAA.

 

[amaroo]

The plane is a dud in my books .... simples

 

[Berlin]

And China and Europe will want to do their own assessments. I don’t think they will want to rely on the FAA.

Luckily so. It will give me much greater confidence once they've also approved the "fix".

 

[JinbaIttai]

Pilots at the controls of the Boeing Co. 737 MAX that crashed in March in Ethiopia initially followed emergency procedures laid out by the plane maker but still failed to recover control of the jet, according to people briefed on the probe’s preliminary findings.

After turning off a flight-control system that was automatically pushing down the plane’s nose shortly after takeoff March 10, these people said, the crew couldn’t get the aircraft to climb and ended up turning it back on and relying on other steps before the final plunge killed all 157 people on board.

The sequence of events, still subject to further evaluation by investigators, calls into question assertions by Boeing and the U.S. Federal Aviation Administration over the past five months that by simply following established procedures to turn off the suspect stall-prevention feature, called MCAS, pilots could overcome a misfire of the system and avoid ending in a crash.

The pilots on Ethiopian Airlines Flight 302 initially reacted to the emergency by shutting off power to electric motors driven by the automated system, these people said, but then appear to have re-engaged the system to cope with a persistent steep nose-down angle. It wasn’t immediately clear why the pilots turned the automated system back on instead of continuing to follow Boeing’s standard emergency checklist, but government and industry officials said the likely reason would have been because manual controls to raise the nose didn’t achieve the desired results.

After first cranking a manual wheel in the coughpit that controls the same movable surfaces on the plane’s tail that MCAS had affected, the pilots turned electric power back on, one of these people said. They began to use electric switches to try to raise the plane’s nose, according to these people. But the electric power also reactivated MCAS, allowing it to continue its strong downward commands, the people said.


Ethiopian Airlines Pilots Initially Followed Boeing’s Required Emergency Steps to Disable 737 MAX System

 

[Quickstatus]

How many manual trim wheel rotations are required to move the trim tab indicators from full down to full up?

 

[AviatorInsight]

How many manual trim wheel rotations are required to move the trim tab indicators from full down to full up?

A lot! But you’d never go from one extreme to the other. One pilot will fly and the other (usually the FO) will move the trim wheel with what the Capt wants.

 

[Quickstatus]

If true the pilots might have thought a manual trim was taking too long - too many rotations to make a difference while they were unstable, then thought electrical would help and turned the motors back on?