MCAS is not supposed to work with the AP on, it is only intended to keep control forces within certified limits for the PILOTS (50lbs. IIRC) under specific conditions.

If the AP is on, it can do it's own trimming.

The issues reported AFTER engaging the AP may well be some sort of glitch (software possibly), but should not be MCAS normal function.

With Lionair, MCAS appeared to operate correctly, it was just given bad data from the AoA. It should not have been operating but it didn't know that. It did what it was supposed to do.

My understanding is that MCAS will stop if manual trim is used. HOWEVER... if MCAS is still being told a stall/high AoA condition exists it will start trimming again in 10 seconds.

That last is potentially very insidious and confusing, especially if you have lots of things going on in the cockpit. You use trim, correct the problem, and note that trim condition is stable. Then you start looking at other alarms, and then MCAS starts again.

Typically a actual high AoA would be resolved within ten seconds. The designers did not really account for bad AoA data.

Can real Max 8 pilots help us here with these question?

1. If AP is on, will MCAS kick in from your experience or your training? From report of 1st crash, AP is on till end of flight.

2. Vertical speed oscillation per satellite tracking data shows similar pattern for both crashes. I would assume “climb” is from pilot override and “descent” is from either AP or MCAS? In both cases, computer trumped human intervention. Is this correct?

Thanks.

I agree.

If you read FAA statement yesterday, they argue they stick with their principal and the decision is data driven. That is why they are the last to ground 737 Max.

On the contrary, the company and FAA knew something for months after 1st crash. They have the best info among all parties in the world. This is common sense.

So can we say all others who grounded 737 Max earlier are not as data driven as FAA?

The inaction from FAA is not something I can understand.

No, not supposed to. And there's not much experience or training available, that's part of the problem :rolleyes:

I recall the AP was off for Lionair, at least after they got into trouble.

Suspicion is that the MCAS interfered with human intervention. The intervention was hand-flying, which cannot be "trumped" by automation, but a slow and intermittent runaway trim could be very confusing.

NYTimes reporter hoping to speak w Max pilots
 

Hi all, I’m a reporter at the New York Times and am hoping to speak with any Max pilots. Feel free to reach out at 01 212 556 1287, 01 510 292 9576 or [email protected]

Thanks

If the autopilot is engaged with some kind of altitude dialed in and the 'nose-down mechanism' kicks in (whether it is supposed to be engaged or not) and pitches the nose down the autopilot may attempt to climb again only to have the nose-down mechanism pitch the nose down again.

I flew a new twin that had a similar problem. The signal from the attitude indicator that was supposed to be cancelled when the aircraft leveled off and replaced with a signal from the altimeter never was cancelled resulting an a (mild) pitch up and down motion. Had to take the airplane back to Bendix to find the problem.

That 200 hr F/O was probably climbing around the cockpit like a child on a playground. That's the connotation media tries to create. Some parts of the industry are actually that poor yet never mentioned.

For the 1st crash, below is pilot/FO (PIC/SIC) info from the preliminary report (https://reports.aviation-safety.net/...RELIMINARY.pdf). Their flight lasted 11 min, about 2x of 2nd crash.

Pilot in Command
Gender : Male
Age : 31 years
Nationality : India
Date of joining company : 25 April 2011
License : ATPL
Date of issue : 28 July 2016
Aircraft type rating : Boeing 737
Instrument rating validity : 31 May 2019
Medical certificate : First Class
Last of medical : 5 October 2018
Validity : 5 April 2019
Medical limitation : Pilot shall wear corrective lenses
Last line check : 19 January 2018
Last proficiency check : 7 October 2018

Flying experience
Total hours : 6,028 hours 45 minutes
Total on type : 5,176 hours
Last 90 days : 148 hours 15 minutes
Last 30 days : 81 hours 55 minutes
Last 7 days : 15 hours 45 minutes
This flight : About 11 minutes

Second in Command
Gender : Male
Age : 41 years
Nationality : Indonesia
Date of joining company : 31 October 2011
License : CPL
Date of issue : 15 May 1997
Aircraft type rating : Boeing 737
Instrument rating validity: 31 August 2019
Medical certificate: First Class
Last of medical : 28 September 2019
Validity : 28 March 2019
Medical limitation : Pilot shall possess glasses that correct for
near vision
Last line check : 4 July 2017
Last proficiency check : 25 August 2018

Flying experience
Total hours : 5,174 hours 30 minutes
Total on type : 4,286 hours
Last 90 days : 187 hours 50 minutes
Last 30 days : 32 hours 55 minutes
Last 7 days : 20 hours 20 minutes
This flight : About 11 minutes

https://www.cnbc.com/video/2019/03/1...el-elwell.html


Similar track data between the 2 flights drove the FAA's decision to ground the fleet. Took a few days to run enhancement program to decipher ADS-B raw data.

With rest of world taking opposite position, FAA has no choice but to capitulate (if not for technical/safety reason, but for other reasons), regardless of what satellite data and their enhancements say.

However, within 48 hours post 2nd crash, I thought Boeing/FAA was trying quite hard to convince public that it is safe to fly with 737 Max.

We told German that their car have emission problems, we told Chinese their telecom equipment can spy you on mobile networks. For our own planes, we told the world that you need to wait for us as we are data driven. To me this sounds like a convenient excuse.

When I read the NASA reports from other pilots, I wonder if this is all about MCAS. The reports seem to indicate that the MAX issues came into play with the autopilot engaged during climb out, but they were able to stop the decent when they switched the auto pilot off and flew manually. This is not indicative of an MCAS problem as I understand MCAS. My current understanding is that MCAS only functions during manual flight control and therefor would not be engaged during use of autopilot. If this understanding is correct, then it leads me to wonder if there is an issue with the autopilot as well as the MCAS - because I cannot imagine why any pilot would not disconnect autopilot in the Lion Air situation. Yet, NASA reports are saying the issue corrected once the autopilot was disconnected and they flew manually. These two are counter to each other and seems to leave open more than MCAS as cause.

I have never flown the 737, I moved from the 320 to the 777. But I cannot imagine why the FAA feels there is minimal training and they can call the MAX the same or nearly the same as the NG. I have JS on both and other than the archaic overhead panel, they seem vastly different to me - then toss in the MCAS and no training, or even awareness of the system from initial deployment of the aircraft into service.... wow, just wow. The FAA and Boeing should be ashamed of themselves for doing such a thing.

As I stated earlier in the thread, I have JS prior on the MAX, but generally if I can, I will try to go on the Bus just for comfort. That said, post these two events, I would avoid the MAX for an abundance of caution, as I do not want to be a first hand witness to the fight with MCAS (or whatever is going on with the control system). Glad that the US finally came to ground them until this can be sorted out.

It is a shame really, the 737 is such a durable workhorse and Boeing seems to have damaged its reputation immensely; will take years to recover from the bad press if this keeps going for too long.

NASA report is also similar to prior flight experience (which landed safely) of the 1st crashed 737 Max last year per preliminary report:

The aircraft departed at 1420 UTC (2220 LT) at night time, the DFDR showed the stick
shaker activated during the rotation and remained active throughout the flight. About 400 feet,
the PIC noticed on the PFD the IAS DISAGREE warning appeared. The PIC handed over
control to the SIC and cross checked the PFDs with the standby instrument and determined
that the left PFD had the problem. The PIC noticed the aircraft was automatically trimming
AND. The PIC moved the STAB TRIM switches to CUT OUT and the SIC continued the
flight with manual trim without auto-pilot until the end of the flight.

The remainder of the flight was uneventful and the aircraft landed Jakarta about 1556 UTC.
After parking, the PIC informed the engineer about the aircraft problem and entered IAS and
ALT Disagree and FEEL DIFF PRESS problem on the AFML.
The engineer performed flushing the left Pitot Air Data Modul

This is exactly what has been puzzling me. The two pilots on the previous flight were familiar with the CUT OUT switches and the two on the accident flight were not? The earlier two even proved the problem by activating the switches again which initiated the AND condition again before shutting them off for the rest of the flight. If you look at the DFDR graph on the initial report, the accident crew looked to be fighting the automation to the end.

I think this is related to the phase of flight they were in. As I recall the first crew had the issue occur in cruise, so they had altitude, energy and time to figure things out. The second crew had everything go to hell on them right after rotation.... stick shaker, trim wheels spinning, stall warnings, etc. They didn't have a lot of energy or altitude to play with.

Doesn't really sound like that's the case. Read two posts above.


The aircraft departed at 1420 UTC (2220 LT) at night time, the DFDR showed the stick shaker activated during the rotation and remained active throughout the flight. Etc, etc.

Thanks, I missed that.

An MCAS malfunction won’t exactly present itself as a runaway trim situation, which makes it even more dangerous (especially considering the pilots aren’t even briefed on the system).

Unlike a typical stab trim runaway, MCAS trims for 10 seconds at a time and then takes a 5 second break. So the trim isn’t running away nonstop and it can also be stopped by activating electric trim. You can’t really fault the late pilots for not running the memory items for a stab trim runaway because not all the signs of a stab trim runaway were present; indeed, they were faced with the malfunction of a system they didn’t even know existed.

Part of my puzzlement remains, why did the crew on the previous flight know how to do a cut off on the MCAS and this crew didn't.

They didn’t cut off the MCAS, they prevented the MCAS from operating the trim. It sounds like the first captain just happened to notice the trim driving nose down and turned it off. Perhaps there weren’t as many bells and whistles going off. If they knew what the MCAS was and how to cut it off they were amongst a very small minority.

Link Fixed. It is of interest, need to copy/past URL.

Sorry - tried posting a link above but not sure why it is not working.:confused:

vBulletin didn't like that URL for some reason, I changed it text so you can copy/paste.

Great, thanks rickair7777. Sorry for the confusion.

All 737 Max's grounded?
 

I was munching on some lunch yesterday at SLC and watched a DAL Max takeoff into the blue yonder. Aren't they grounded?

This is why eyewitness accounts are unreliable.

Sorry Winston. I did casually post without researching first. I was unplugged for the last few days, just catching up on the news.
It must have been an 737-8 with an APB winglet. Thanks.

They can also be ferried with no passengers, per the FAA grounding order.

DAL has no 737 maxes.

They flew an hour and a half with the stick shaker going off?

Maybe they pulled the CB. Or else they just flew with it. Either way pretty crazy considering there were multiple alarms and failures.

Ca observed the trim. Decided on his own to turn off cut out switches. Training. Insight. Luck. Fate. Another flight where something similar happened. Experience. It wasn’t because he suspected MCAS.

Repo with no pax allowed.

He decided to perform the memory item for Runaway Stabilizer because the trim was moving when it shouldn't have been. Training. period.

Better tell Delta they own the MAX because everyone who works there knows we don’t operate a single one.


GP

No MAX at DL. Look for scalloped engine nacelles to ID a MAX.

Bad link.

They found the jackscew, it was in full nose down trim, that was the key evidence that changed minds at Boeing/FAA

I was replying with mild sarcasm to the guy I quoted. I’m a guppy driver for DL.


GP

Oh yeah! I grabbed the wrong quote..
It's hard to tell em all apart now days, 737s that is.

Why does the MAX aircraft need a stick shaker and this new system?