MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

[patplan]

And so on..., there are 322 pages of the Final Report.

You can download the Full Report here:

- http://knkt.dephub.go.id/knkt/ntsc_a...l%20Report.pdf

[OldnGrounded]

Originally Posted by DaveReidUK

Somebody please correct me if I've missed something in the report, but the evidence for the KNKT's finding that the installed AoA sensor was misaligned appears to be entirely circumstantial.

I think that's correct. The Indonesian report appears to say that it could not establish that the vane was correctly installed and tested, rather than that there is evidence that is was not.

[patplan]

[patplan]

[Takwis]

It's been a year, with lots of conflicting information. But I seem to remember Boeing (and many hotshot pilots) insisting that if the Airspeed Unreliable checklist had been done, they would have been home free. Is that correct?

[patplan]

[Tomaski]

Originally Posted by Takwis

It's been a year, with lots of conflicting information. But I seem to remember Boeing (and many hotshot pilots) insisting that if the Airspeed Unreliable checklist had been done, they would have been home free. Is that correct?

It's not really quite that simple. There are a couple significant issues with the Airspeed Unreliable NNC. First, being somewhat generic it does not provide a lot of specific guidance on how to execute this procedure during takeoff - particularly in regards to guidance on when to retract the flaps. Second, there is little information regarding all the various annunciations and warnings that can occur with a bad AOA or airspeed input. As we have seen, there are a bunch of them. Finally, I seriously doubt that the accident crews ever had a chance to practice this malfunction in the sim. An analogy would be the likely performance of an aircrew that experienced a V1 engine failure with a balanced field and high terrain consideration if they never practiced this maneuver in the sim.

If the accident crews had regularly been exposed to takeoff Airspeed Unreliable (and Runaway Stab, for that matter) malfunctions during training, then there is a reasonable argument that the outcome may have been different. However, it seems that some "memory items" are not considered to be as important than others.

[gearlever]

IMHO it's bad system design not to have a totally independent stall warning like older types e.g. B727 or A300 had.

[Takwis]

Let me rephrase my question. I don't think that following that particular checklist would get them "home free"...I was asking about the assertions of the "hot shots". I seem to remember a whole lot of people (to include Boeing) insisting that if they had only followed that checklist, all would be well. I suppose I could go back through something like 14 closed posts and 10,000 plus comments, and figure it out myself. I was just wondering if anyone else remembered it that way.

[Water pilot]

The issue with the checklists is that none of the proposed checklists actually involve identifying and resolving the problem. The fault was a sensor/software error in an automatic system that could not be deactivated. Every proposed "if only they had done this..." solution involves actions that would have only coincidentally reset or disabled MCAS, a system about which they knew nothing. Even the runaway trim checklist did not disable MCAS, it was still waiting offstage to take charge if the electric trim happened to be turned back on. (And I note that even the runaway trim checklist is not the correct solution, since a true runaway trim would involve turning off the electric trim as soon as possible rather than attempting to use it to correct the erroneous stabilizer inputs.)

Reading the CVR brings this point home in a very painful and tragic way. The pilots were following a checklist that they thought would help, but ultimately all that it did was to distract them from the real problem. There might be a larger safety issue here but I'm not quite sure how to express it.

[Maninthebar]

So far as I remember the (sometimes heated) discussion there were those who maintained, and probably still maintain, that the memory drill for Runaway Stabiliser Trim would have saved both crews AND that this was the common sense 'airmanship' response to the situation in which the crews found themselves.

[Takwis]

Originally Posted by Water pilot

The pilots were following a checklist that they thought would help, but ultimately all that it did was to distract them from the real problem.

Absolutely agree. What I have read of this report hammers that home. My question was, basically, "Hey, where are all those hotshots, the 'fly the f*ing airplane' crowd? I think this pretty well disproves their machismo."

[Takwis]

Originally Posted by Maninthebar

So far as I remember the (sometimes heated) discussion there were those who maintained, and probably still maintain, that the memory drill for Runaway Stabiliser Trim would have saved both crews AND that this was the common sense 'airmanship' response to the situation in which the crews found themselves.

I remember that each* of those checklists, Airspeed Unreliable and Runaway Stabilizer Trim were touted as the 'magic bullet', at times, depending on which failure of the aircraft or of the accident pilots was under discussion at the moment.

* separately, not together.

[Maninthebar]

"Following the Lion Air accident, Boeing convened a Safety Review Board (SRB) to reconsider whether the absence of the AOA DISAGREE alert from certain Boeing 737-8 (MAX) flight displays presented a safety issue. That SRB confirmed Boeing’s prior conclusion that it did not"

The minutes of this Board will provide interesting reading in the light of our knowledge that the original implementation of MCAS depended on the input from one AoA but not the other

[Aihkio]

So the poor pilots were put into a situation where only good luck would have saved them. And maybe the odd pilot with paranoia about the aircraft trying to kill him would have cleared it without luck.

[BDAttitude]

I do also see some significant shortcomings of the fault isolation procedures and the SMYD BITE. Maintenance ran it three times without result. Fault logging in the air was also vacuous.
So the one cannot work comprehensively on ground because vanes show anything.
The other did not provide anything meaningful presumably because no reference from the other vane is used.
So an AoA error which is not SNA or out of rang but „only“ drift seems to be practically non-diagnoseable.
Or am I missing something?

[Takwis]

Originally Posted by BDAttitude

So an AoA error which is not SNA or out of rang but „only“ drift seems to be practically non-diagnoseable.
Or am I missing something?

I don't think you are. The next question is, how can you base something as overwhelmingly powerful as MCAS on that?

[OldnGrounded]

Originally Posted by Takwis

Originally Posted by BDAttitude

So an AoA error which is not SNA or out of rang but „only“ drift seems to be practically non-diagnoseable.
Or am I missing something?

I don't think you are. The next question is, how can you base something as overwhelmingly powerful as MCAS on that?

Exactly. It continues to be, literally, mind-boggling that such an obvious major design error made it all the way through to production.

[568]

Originally Posted by derjodel

In isolation, that sounds like a good argument. In context, that this pilot was experiencing something that should not be happening in the first place, quite literary the plane (trying to) kill him by a non-documented system, this sounds like victim blaming to me. The event was not a simple unreliable speed. It was an unreliable speed with repeatable unexplained nose down trims and the Earth approaching you, fast. And ultimately, if a checklist should have been done but wasn't, isn't that on the captain?

On a technical note, would the AP engage under those conditions??

For autopilot engagement the aircraft must be trimmed properly so maybe the autopilot (s) would not be available to the crew.

[Maninthebar]

Originally Posted by 568

For autopilot engagement the aircraft must be trimmed properly so maybe the autopilot (s) would not be available to the crew.

From the report

(F/D) Autopilot Engagement Criteria

The Boeing 737-8 (MAX) Auto Flight Director System (AFDS) is a dual system consisting of two individual FCC and a single mode control panel.
The autopilot (A/P) functionality is provided by the FCC. The A/P for captain side is controlled by the FCC A and the A/P for first officer side is controlled by the FCC B. Each A/P can be engaged by pushing a separate CMD (command) engage switch. A/P engagement is inhibited unless the following flight crew–controlled conditions are met:
• No force or very low force is being applied to the control wheel
• The STAB TRIM cut out switches is at NORMAL.
• Neither pilot main electric trim switches is activated.
• The Mode Control Panel (MCP) disengage bar is not activated.

Except during approach, only one A/P can be engaged at a given time.

Autopilot Disengagement During single channel operation,
A/P automatically disengages when any of the following crew-controlled conditions occurs:
• Pushing either A/P disengage switch,
• Column or wheel force override,
• Pushing either Takeoff/Go-around (TO/GA) switch: - With flaps not up or, - Glide Slope (G/S) engaged,
• Pushing an illuminated A/P ENGAGE switch,
• Pushing the A/P DISENGAGE bar down,
• Activating either flight crew control main electric trim switch,
• Moving either STAB TRIM cutout switch to CUTOUT.