Lionair 610 crash

[AviatorInsight]

Im putting an MCAS question here rather than the Ethiopian 737Max8 thread because we dont know what happened to ET302

Boeing says MCAS electrical trim can be turned off - just like the procedure for a Runaway trim.
However, MCAS does not present as a runaway trim, rather it pushes trim nose down 2 deg then stops then keeps doing 2 deg every few seconds. (But it still would be an Pilot uncommanded trim).

Is it possible therefore because it does not look like a runaway trim, the pilots are not thinking to use the runaway trim procedure as a fix (remembering the fight deck would at this time be quite chaotic and startling)

I'm not reading that at all.

If the aircraft is actually approaching the stall with no other erroneous data, then MCAS is designed to trim nose down, great, crisis averted. However...if in conjunction with an unreliable airspeed/altitude/AoA/plus a couple of others and you get an uncommanded nose down trim, that to me would be a runaway. The nose down trim can last up to 10 seconds (that's a lot of trim!!). I then trim back via the electrical switches while still fighting the thing. If I then let go of the electrical trim and 5 seconds later it starts trimming forward again (uncommanded) that's a runaway trim. This cycle will continue to occur until the system is deactivated by BOTH the STAB CUTOUT switches.

 

[Quickstatus]

Yes, it can be.



Where are you reading that it stops after 2º? From what I recall of the Lion trim input graph there were sustained inputs that only stopped when trimmed against.

And 2º of what? Pitch change? That's enough for a couple of thousand feet per minute of altitude change. Pitch trim setting...the effect would be large, far out of proportion for such a seemingly small number.



Hard to say, but given that it does not respond to the normal initial actions, it may well be a case of too late.

Thanks, Actually, 0.27 deg stabiliser up per second for up to 10 seconds and up to 2.5deg stab change, then stops and resumes after 5 seconds.

For a while at least the LionAir pilots managed to counteract the uncommanded trim by electrically trimming - they managed to do it several times but were unable to apply opposite trim at the last 4-5 MCAS inputs.

 

[jb747]

2.5º of stab movement is a lot.

 

[Quickstatus]

Understand.

I think the reason the final series of MCAS inputs were not successfully reversed was because the PF did not completely reverse it with enough trim input, so the subsequent MCAS trim input just added to the previous until it was nose down

 

[Quickstatus]

MCAS - Deja -vu?
From pprune - LSAS
http://www.md-11.org/md11/AFS Panel.pdf

 

[jb747]

MCAS - Deja -vu?
From pprune - LSAS
http://www.md-11.org/md11/AFS Panel.pdf

Apart from the fact that it's so well written, I could have been reading an Airbus flight manual. That's close to the AB's protection systems.

But, I'll also bet that the MD-11 had a triplicated AoA system. That's a stumbling block that Boeing has to get past.

 

[OZDUCK]

Boeing, itself,has now recommend grounding the B737 Max fleet. According to the article evidence from the Ethiopian crash site has caused the change of mind. Boeing grounds entire crash aircraft fleet

 

[Quickstatus]

At least it defines the limit of pitch attitude to 10 deg ND or 30deg NU

 

[ermen]

Posting the link here (Bloomberg via the SCMP)
Off-duty pilot saved second-last Boeing 737 MAX 8 flight from crashing

As the Lion Air crew fought to control their diving Boeing 737 MAX 8, they got help from an unexpected source: an off-duty pilot who happened to be riding in the coughpit.

That extra pilot, who was seated in the coughpit jump seat, correctly diagnosed the problem and told the crew how to disable a malfunctioning flight-control system and save the plane, according to two people familiar with Indonesia’s investigation.

The next day, under command of a different crew facing what investigators said was an identical malfunction, the jetliner crashed into the Java Sea killing all 189 aboard.

Basically talks about how a jumpseat pilot who was flying on the flight preceding the ill-fated Lion Air 7M8 crash correctly diagnosed the failing MCAS system.

My question is - is the checklist to switch off this system meant to be committed to memory?

 

[drron]

And why wasn't that told to the pilots the next day-ie how to react to that problem.

 

[Himeno]

So PK-LQP had an issue the evening prior to the crash. Issue corrected with help of off duty jump seat pilot.
Tech issue presumed fixed by maintenance overnight, so no mention of any problem to new crew the next morning.

 

[OATEK]

So PK-LQP had an issue the evening prior to the crash. Issue corrected with help of off duty jump seat pilot.
Tech issue presumed fixed by maintenance overnight, so no mention of any problem to new crew the next morning.

Not the sort of handover you would have in most professions where safety is such a key part of their business.

 

[ermen]

ok another report on the events in the Lion Air coughpit before it crashed.

Pilots were basically trying to find the procedure in the manual that could solve their problem. Would it be a hard thing to do (I have no idea)?


coughpit voice recorder of doomed Lion Air jet depicts pilots' frantic search for a fix

 

[AviatorInsight]

My question is - is the checklist to switch off this system meant to be committed to memory?

Pilots were basically trying to find the procedure in the manual that could solve their problem. Would it be a hard thing to do (I have no idea)

As I have mentioned here before, the memory items for a runaway stabiliser would have turned off the system and even if by some means the stabiliser still kept trimming, the memory items continue to say to “grasp and hold the trim wheel”.

Because these items are committed to memory, there is a quick action index at the front of the quick reference handbook (QRH) where all the memory item checklists are housed.

 

[Quickstatus]

As I have mentioned here before, the memory items for a runaway stabiliser would have turned off the system and even if by some means the stabiliser still kept trimming, the memory items continue to say to “grasp and hold the trim wheel”.

Because these items are committed to memory, there is a quick action index at the front of the quick reference handbook (QRH) where all the memory item checklists are housed.

@AviatorInsight , presumably the trim wheel has a massive mechanical advantage - the disadvantage there is many turns are required to move the Stabiliser a small amount. I understand that airspeed affects the pitch attitude outcome of the stabiliser position. However how many manual turns of the wheel is required to re-trim the aircraft if the Stabiliser has been pushed 2.5 deg nose down?

Is there an indicator near the Stabiliser trim wheel of the actual Stabiliser trim position?

 

[AviatorInsight]

@AviatorInsight , presumably the trim wheel has a massive mechanical advantage - the disadvantage there is many turns are required to move the Stabiliser a small amount. I understand that airspeed affects the pitch attitude outcome of the stabiliser position. However how many manual turns of the wheel is required to re-trim the aircraft if the Stabiliser has been pushed 2.5 deg nose down?

Is there an indicator near the Stabiliser trim wheel of the actual Stabiliser trim position?

Perhaps for the Max? Whenever we have done manual trim it’s only really been a small amount of movement of the wheel or at least it doesn’t feel like a lot of rotations.

As to where the indicator is? It’s very close to the wheel.

 

[Quickstatus]

How does such a small diameter wheel move a very large (by comparison) stabiliser?. Where is the mechanical advantage?

......

Reuters reports that CVR/FDR recordings from JT610 showed that Stall warnings were audible.
PF (captain) handed over controls to FO.
Captain then tried to consult the quick ref manual in the final moments of flight.
FO control inputs for nose up was not as strong as Captain

 

[oz_mark]

Final report from Indonesia is here

http://knkt.dephub.go.id/knkt/ntsc_aviation/baru/2018%20-%20035%20-%20PK-LQP%20Final%20Report.pdf

 

[jb747]

Extremely interesting reading.

A single burst of MCAS would have the effect of putting the aircraft out of trim, but when it stopped the load would still be well within what could be flown. The fact that it stopped, would tend to redirect people away from the runaway trim checklist, because that's not the behaviour of runaway trim. The natural reaction to get rid of the trim load would be to re-trim the aircraft using the thumb switches. That then had the effect of resetting the MCAS, and so setting it up for continuous inputs until it overpowered the pilots.

 

[AviatorInsight]

Wow...There was a lot of indications even during the take off roll at 80kts that things weren't right. It was very messy by the captain but things got really bad when the FO took control.