737 Max

[tim]

Rev, earlier today.

[NotoriousREV]

Actually, I was naked, but otherwise spot on.

[IanF]

We've definitely nearly reached agreement on this.

We’re not arguing Simon. We are talking about an accident with limited information.

Thanks for that Rev. Unfortunately, all that proves was the MCAS was trying to do its job correctly. The issue was the erroneous AoA on one side and as Tim said, with only two inputs, it can’t vote one system out. I’m still struggling to understand why they didn’t follow the Recommended procedures.

Boeing’s statement:

“Boeing’s 737 MAX Flight Crew Operations Manual (FCOM) already outlines an existing procedure to safely handle the unlikely event of erroneous data coming from an angle of attack (AOA) sensor. The pilot will always be able to override the flight control law using electric trim or manual trim. In addition, it can be controlled through the use of the existing runaway stabilizer procedure as reinforced in the Operations Manual Bulletin (OMB) issued on Nov. 6, 2018.“

[IanF]

A senior VP Airbus once bollocked my mate for failing some ‘stan pilots; he said Airbus isn’t there to train pilots, but to sell aircraft. If they crash, the airline will need new aircraft plus more “training” for its new pilots.

Boeing keeps its manuals light on info for the same reason probably.

[NotoriousREV]

We’re not arguing Simon. We are talking about an accident with limited information.

No we're not. We're arguing over whether MCAS is a new system to the 737MAX, nothing else. It is, and you're wrong.

[IanF]

We’re not arguing Simon. We are talking about an accident with limited information.

No we're not. We're arguing over whether MCAS is a new system to the 737MAX, nothing else. It is, and you're wrong.

[Jackleg]

Fuck, Rev's gone full Dinny...

[unzippy]

This is the data from the Lion Air crash. Note Autopilot is not engaged and that every time manual trim is set, auto trim does the opposite:

What's with green line on the last graph - did the plane bounce?

[NotoriousREV]

Fuck, Rev's gone full Dinny...

Don’t be so fucking stupid.

[Jackleg]

Fuck, Rev's gone full Dinny...

Don’t be so fucking stupid.

Apologies Rev, but you are arguing with someone who does this for his day job.

[JLv3.0]

I’m really not sure who I should be aiming “aviatiown3d” at yet.

Can someone let me know when things pan out a bit more clearly?

I don't think we're getting any closer, tbh. Can someone just tell me who's right so I can mock the other one for a mumbloid, then move on?

[dinny_g]

[scotta]

Fuck, Rev's gone full Dinny...

Don’t be so fucking stupid.

Apologies Rev, but you are arguing with someone who does this for his day job.

[NotoriousREV]

Fuck, Rev's gone full Dinny...

Don’t be so fucking stupid.

Apologies Rev, but you are arguing with someone who does this for his day job.

He doesn’t fly 737s and he’s saying the manufacturer is wrong.

[Gwaredd]

I really hope Ian is right on this one, else that means a fat man on the internet knows more about planes than an actual pilot.

[Simon]

Could it be somewhere in the middle? Maybe Boeing are saying that it's a 'new feature' in the same way that the start button was 'new' in Windows 8.1. It was there before but it did something quite different.

See also: "New and Improved". Is it new or is it improved?

[NotoriousREV]

Could it be somewhere in the middle? Maybe Boeing are saying that it's a 'new feature' in the same way that the start button was 'new' in Windows 8.1. It was there before but it did something quite different.

See also: "New and Improved". Is it new or is it improved?

New.

Ian claimed that it was previously called something else (Minimum Speed Reversion Mode). MSR mode only works when autopilot is engaged and will adjust pitch up or down, and apply throttle to maintain the aircraft speed above minimum speed x 1.3 based on the current flap configuration. As Ian says, it's an Autopilot mode so does not work if Autopilot, or Autothrottle is switched off.

MCAS activates under the following circumstances (when working correctly): High angle of attack, Autopilot is off, Flaps are up, the aircraft is tightly turning (but not only during tight turns), airspeeds are approaching stall.

The superficial similarities between the 2 systems are that they both adjust trim based on information about speed and angle of attack. But MCAS is a hidden system that activates automatically under certain circumstances, whereas MSR is an Autopilot mode that triggers under a different set of circumstances.

https://www.seattletimes.com/business/b ... air-crash/

https://www.flightglobal.com/news/artic ... te-453716/

Edited to change wording on when MCAS operates.

[mik]

Do the trim wheels (3m50s in tbe earlier vid) spin like billy-oh when MCAS intervenes? If yes, then there is at least a clear indication of what is going on? Even if you dont know why?

[NotoriousREV]

Do the trim wheels (3m50s in tbe earlier vid) spin like billy-oh when MCAS intervenes? If yes, then there is at least a clear indication of what is going on? Even if you dont know why?

Yep. There's some discussion about why the pilots didn't appear to twig what was happening, given a crew the day before on the same plane had the issue but immediately fixed it. Ian will know far better than me but from what I've read they should have followed the "runaway stabiliser trim" process but "runaway" is when the trim just runs to its maximum constantly regardless of what the pilots do, whereas (at least in the Lion Air crash) they could change the trim to where they wanted it to be, but the system would just adjust it back so it may be that they didn't recognise it as runaway trim.

[Jimmy Choo]

So... The moral of this story is to only fly with BA, Virgin or to interview the pilot before take off?

Oh, and that Rev will argue with anyone, about anything at any time.