Alaska Airlines flight forced to make an emergency landing (Part II)... 26

[3DDave]

"In many cases trying to reengage the autopilot is probably a good idea as many things are made worse by manual intervention."

Autopilot is not a stall recovery system. If the plane is giving a stall warning, real or false, the autopilot isn't to be used.

"Runaway trim as a single issue is almost certainly a lot easier to figure out and the trim motors get cut out if you pull against it normally, but not in MCAS."

Yes, and the second step is that if it doesn't stop from pulling, disable the motors, which is why those switches are right there and the Emergency AD emphasized that fact.

"As I recall the second flight, the aircraft was trimmed nose down and the second pilot was finding it hard to keep the nose up with all that trim. So he tried something which didn't work."

The second accident flight - it was trimmed nose down because the captain did not trim back to neutral before the F/O had the bright idea to shut off access to the simple to use trim button. They didn't monitor any instruments, at least not in any effective way. As airspeed steadily increased no one noticed the engines were still at full take-off thrust even though they were in level flight. Whatever they learned it was in one ear, out the other, likely because the autopilot did all the flying for them.

The MCAS is a variation of how Speed Trim works. An automatic movement of the horizontal stab to feed back to the pilots. Since MCAS is to discourage pilots from pulling harder on the controls, it cannot cutout when pilots pull harder on the controls. This may have caught out the Lion Air crash pilots; it did not catch out the captain from keeping the plane stable. It was emphasized to the Ethiopian crew.

No one said, inside Boeing or outside, "What if a pilot just ignored their training and did all steps the opposite of the manual? Would that cause a problem?" No kidding. It causes a problem when pilots do that.

Boeing employees human beings. Pilots are human beings. How would Boeing employees know more about pilots than pilots do?

As soon as the Emergency AD was issued it became not-a-Boeing responsibility. What made things complicated was the airline and CAA saying the ET-302 pilots followed the Emergency AD instructions perfectly, no mistake was made. A lot of people believed that statement. That Boeing and the FAA had produced a procedure that failed. We don't know if it would or not because ET-302 didn't try it.

 

[Alistair_Heaton]

To note the trim system is different on the max to the NG.

On the NG there are two switches, one allows you to kill the automatic systems input to one motor , the other the electric power to both screw jack motors. No power your into turn the trim wheel manually.

Max both switches are wired in series and kill the power to the one and only trim motor. Use either of them and your into manual mode.


No sim session does 10 seconds of flight, it will have been dead aircraft on the ramp, start up, taxi out and departure and at some point something will have happened.

Anyway the subject is pretty much dealt with now. Public opinion isn't going to change the process.

I am extremely doubtful they will get the MAX 10 certified any time soon in the next 5 years.

Littleinch your grasping the edges of the human factors side of things when something happens.

 

[3DDave]

"On the NG there are two switches, one allows you to kill the automatic systems input to one motor , the other the electric power to both screw jack motors. No power your into turn the trim wheel manually."

This is not worth mentioning as the guidance on the NG was to always disable both rather than for the pilots to puzzle out which was the problem source.

"No sim session does 10 seconds of flight, it will have been dead aircraft on the ramp, start up, taxi out and departure and at some point something will have happened."

Already discussed and I think you don't know anything about software. There is no reason the sim software cannot be initialized at any possible condition if the makers of the sim software make that function available. But, even if it starts at the ramp, the real "test" can be to do all the same stupid things that were done up to the last 10 unrecoverable seconds.

Unless the point is that no pilots will ever follow procedures. That is scary.

 

[LittleInch]

As I said before 3D Dave, you have been pretty consistent in your views - it's just I don't agree with them so not much point saying the same things.

The issue is that when you read the AD it continually emphasises set the trim switches to cut out. Only right at the end it say you "can" use the trim switches to stabilise the airplane, not that you MUST or even SHOULD. But it say set the trim switches to CUT OUT seven times , all of them in CAPITALS.

Also doesn't mention Auto throttle at all.

If this was ever going to be a "memory" item that's what would stick in my mind. Hence why lots of people said the pilots did (at least initially) exactly what they were asked to do by the AD and the plane still crashed. Also the "trim the aircraft manually" turned out to be physically impossible because they had reduced the size of the trim wheel, plus doing it at higher speeds needed more force than they could physically apply. Hence the AD was asking them to do something which couldn't be done in many circumstances. Not to mention that it would take something like 100+ turns to get it back toneutral trim.

I also think as the 737 grew over time, the control surfaces of the trim system could over power the elevators, which wasn't true of the first 737s or even possibly the NG.

Boeing are supposed to know more about the airplane than pilots do and have a duty to design their airplane not to do things which cause pilots to lose control. In my opinion and others, they failed in that duty. You clearly have a different opinion and that's fine. We have a MCAS/DISAGREE.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[AZPete]

Jumping into this with perhaps an overly simplistic POV, but this has been a raging topic for a long time now.

It is not supportable to argue that a crew is inadequate to the task if they perish in a rare cockpit scenario, especially in a novel technology scenario. The mere fact that there are so few occurrences does not clear nor assign the fault automatically. By definition, it is novel, so it bears investigation with a clear conscience and no bias.

The tried and true practical inquiry would run a slathering of crews through a simulation and see how the spaghetti sticks to the wall. If your typical crew response is a negative outcome, then your choices are 1) poor fleet training, or 2) poor technology.

As an outsider looking it, this has all the smell of a technology failure--which redounds to the manufacturer and regulator as primary responsibility to deliver an end product which the 99th percentile of trained crews can operate without negative consequence.

 

[1503-44]

"As an outsider looking it, this has all the smell of a technology failure--which redounds to the manufacturer and regulator as primary responsibility to deliver an end product which the 99th percentile of trained crews can operate without negative consequence. "

If it was not, this whole problem would have been cleaned up and flying quite a while ago.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[Alistair_Heaton]

because the sims are wired to the actual hardware you can't jump in on a level D sim...

You can get it to the point of the weight on wheels moving everything to air mode then slew.

 

[Alistair_Heaton]

BTW there are heap of issues with the fact that they took the piss with the NG certification. Which they grandfathered to the MAX,

The electrical system is causing issues with certification.

And now the level D sims need actual MAX hardware and software... Its really not pretty.

Has Boeing paid out for the sim training requirement? I am told in EASA its now 16 hours to fly it. And that's at 5000$ an hour for 2 crew plus trainer not including wages. 1 sim every 12 months on the NG and MAX every 12 months to stay current.

A220 level D is 5 million and a new airframe is 60 million to give you a price comparison.

to note I have zero clue what my boss has bought the next 30 A220 airframes we are getting. A220 SIMs are like rocking horse shit with a 3 year lead time from ordering.

 

[AZPete]

If you can't SIM it, you can't train it. If you can't train it, you can't fly it.

 

[Alistair_Heaton]

Brilliant post AZ, and utterly spot on...

 

[3DDave]

What is the first sentence of the AD?

Use Main Electric Trim as required.

"Auto throttle" is part of the stall warning procedure, which happened before they reconfigured to enable MCAS.

They passed the Bridge Out sign, drove around the Bridge Out barrier, and gave it the beans right into the ravine.

 

[Alistair_Heaton]

As soon as you turn off one of the isolation switches on a max it kills the power to the stab trim motor. Which there is only one of instead of two on a Ng...

3 seconds later it's over 25kg out of trim.

 

[3DDave]

"because the sims are wired to the actual hardware you can't jump in on a level D sim..."

Really. So if I cycle power mid flight, the actual hardware will be unable to operate the plane? Not only is that terrifying but I don't believe that for a second about computer hardware. You wake it up, give it inputs that it is at 550 knots, 5000 feet, and full nose down trim. What is that hardware going to do about that? Complain there wasn't a pushback?

Again - it doesn't matter. If they follow a crap script to get to an unrecoverable situation then that does not represent what a pilot should have done to not get to that unrecoverable situation.

There is so much straw in that argument it is becoming a fire hazard.

This is suggesting that since Eastern put a plane into a swamp over a failed light bulb that the present state of pilots is so much worse that given a simple script to follow it is acceptable to not only not follow the script but to make even worse ad libs to it?

 

[Alistair_Heaton]

A full power recycle in flight I have zero clue about.

We have the DC battery's and RAT. It's down below 7th redundancy level.

I have zero training or knowledge below what happens after the RAT is out and the electrics go.

 

[Alistair_Heaton]

Btw on the Ng and max you only have level
4 redundancy which is one of the many certification issues on the post Ng 737.

We need level 6 min because of the electric brakes.

 

[Alistair_Heaton]

Btw the computer hardware on an A220 is single thread single core 486 processor

 

[3DDave]

"If you can't SIM it, you can't train it. If you can't train it, you can't fly it."

This is true. Ethiopia had 2 Max simulators with which to try the Lion Air scenario against the AD. AFAIK there is no separate input to the simulator for alpha, so they would know they could not train for it, but decided to fly anyway. They could have requested and then awaited an updated sim software that would allow for a deviation in the AoA sensor reading from alpha or waited for Boeing to produce new flight software.

That is an airline and CAA decision. They made a financial and political decision to fly their national pride of the skies in a way reminiscent of the Teacher in Space Shuttle launch that the US President planned a speech around leading to the management ignoring the danger of a cold-soaked launch.

They could also have re-calibrated an AoA sensor on an actual plane, just like Lion Air had, and prepared to pull power to the SYMD associated with it to return function to the autopilot by automatic fail-over, but they did not do that either.

They didn't try to train. There is no record they held classes, meetings, in-person reviews, spot tests to see if they recalled the memory items. They put a new guy as FO when the previous accident aircraft went down because a new guy FO didn't trim the plane.

They could even have just disabled the electric trim and hand cranked the flights until the new software arrived.

 

[Alistair_Heaton]

I agree nobody is faultless.

Its always the case with an accident.

I don't think you can plan to hand crank the trim for the whole of the flight due to the MEL and the other things that need to be running under the MEL. There will also be operational limitations to do with rvsm airspace.

 

[1503-44]

Five years ago Forbes looked into their crystal ball.


--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[LittleInch]

"They didn't try to train. There is no record they held classes, meetings, in-person reviews, spot tests to see if they recalled the memory items. "

That might well be true, but how many other airlines actually did do that?

Also "What is the first sentence of the AD?
Use Main Electric Trim as required."

Err no, the complete sentence says "Disengage autopilot and control airplane pitch attitude with control column and main electric trim as required."

So the clear main instruction is to control the pitch using the control column. The "as required" bit makes this an optional thing to do the way I read it.

The big thing they don't tell the pilot is that if this is a MCAS runaway, the control column won't cut out the trim command in the same way as runaway trim does. To me its a very confusing directive, but the clear instruction is set the trim switches to CutOut. The fact you're then trying to control an aircraft with loads of force on the column isn't really considered.

For me they missed a big change not emphasising that the thing to do was use the electric trim FIRST, then set cutout switches within 5 seconds of getting nearly level flight.

It would be interesting to know if using manual trim is something that has fallen out of favour or fashion given that the FCC / trim system seems to use it all the time. So is that something the pilots forget they could do and just lets the autopilot or trim system control?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.