Posts about: "Preliminary Report" [Posts: 277 Pages: 14]

So here's what it is known so far. It really narrows it down.

1. Aircraft took off
2. At a few hundred feet AGL all engine power was visibly lost and aircraft crashed.
3. No airworthiness directive was issued for weeks after the crash.
4. Prelim report states that main fuel cuttof switches were moved to the off position immediately after take off, one after the other with one second difference . (YGBFSM)
5. Switches were moved to on position 10 secs after, one by one, but it was too late unfortunatelly.
6. WSJ reported that "there aren’t any recommendations for Boeing, engine-maker GE Aerospace or operators of the aircraft at this stage of the investigation"
https://www.wsj.com/business/airline...ident-2c0b1c3e (paywall)
6. WSJ also reported that "Indian officials have released little information to the public about the investigation, fueling some frustration among American government and industry officials since the June 12 crash, some people familiar with the matter said. U.S. government and industry officials have also been frustrated by what they perceived as the slow pace of downloading, analyzing and sharing the contents of the plane's black boxes, these people said"
https://www.wsj.com/business/airline...article_inline (paywall)

Baffled, as probably all of us. But 10 seconds between \x93cut-off\x94 and \x93run\x94 is not excessive imo:

08:08:42 - max speed
08:08:43 - cut-off eng 1
08:08:44 - cut-off eng 2; run-down eng 1
08:08:45 - run-down eng 2
08:08:46 - startle moment
08:08:47-48 - instruments, levers and switch scan
08:08:49-50 interrogate other pilot why he moved switches
08:08:51: other pilot denies
08:08:52: eng 1 fuel switch to \x93run\x94
08:08:53: it\x92s both fuel switches that were cut off
08:08:56: eng 2 fuel switch to \x93run\x94

Timeline of known events with source attribution from the preliminary report:

08:07:33 ATC: Takeoff clearance
08:07:37 A-SMGCS: Aircraft starts rolling
08:08:33 EAFR: V1 153kts
08:08:35 EAFR: Vr 155kts
08:08:39 EAFR: Gnd-Air mode transition
08:08:42 EAFR: Max IAS 180kts, Eng 1/2 Cutoff switches activate within 1 second of each other
08:08:42 CVR: "Why did you cut off", "I did not" (exact time not specified)
08:08:42 A-SMGCS: RAT deployed (exact time not specified)
08:08:47 EAFR: Both engine N2 below min idle. RAT hyd pwr commences
08:08:52 EAFR: Eng 1 cutoff to RUN
08:08:54 EAFR: APU inlet door opens (auto start logic)
08:08:56 EAFR: Eng 2 cutoff to RUN
08:09:05 ATC: Mayday call
08:09:11 EAFR recording stops

Fuel cutoff switches operated within 1 second of each other suggests to me that the locking mechanism wasn't working as per (SAIB) No. NM-18-33. Any loose item could have accidentally (or not) operated the switches (including hands).

The preliminary Report states 01 seconds (without the decimal point).

It seems like people are jumping to conclusions about the pilots and letting Boeing off the hook without proper investigation. Instead of providing a professional, detailed transcript of the cockpit voice recorder (CVR), we\x92re just getting casual comments about what the pilot allegedly said. Critical information\x97like the timing of transmissions, the checklist items completed before takeoff, and other key details that should be on the CVR\x97are essential for understanding what happened in the cockpit, especially since the crash occurred so soon after takeoff. In my view, the preliminary report feels too convenient for certain parties involved.

Can someone with the engineering knowledge build a timeline/timeframe for fuel cutoff switch RUN to CUTOFF -> fuel stops -> engine flameout -> N2 drops to ? -> VFSGs quit -> RAT deployment starts -> RAT full power -> APU deployment start?
Does the RAT really start providing power in 4 seconds from the E2 fuel cutoff switch RUN -> CUTOFF?


Timeline from AAIB and the public CCTV video:

08:08:33 v1 153 kts
.
08:08:35 vr 155 kts
.
.
.
08:08:39 Liftoff, A/G Air Mode, rotation at 00:18 in public CCTV video
.
.
08:08:42 E1 Fuel Cutoff Switch RUN -> CUTOFF, 180 kts
08:08:43 E2 Fuel Cutoff Switch RUN -> CUTOFF
.............? N1 N2 begin to decrease
.............? "Why did you cutoff", "I didn't"
.............? Airport CCTV shows RAT
.............? N2 < idle speed
08:08:47 RAT hydraulic power
.
08:08:49 Public CCTV video: visible loss of thrust, Alt < 200ft using wingspan
.
.
08:08:52 E1 Fuel Cutoff Switch CUTOFF -> RUN, CCTV video: visible descent
.
08:08:54 APU inlet door begins opening
.
08:08:56 E2 Fuel Cutoff Switch CUTOFF -> RUN
08:09:05 MAYDAY
08:09:11 EAFR Recording stops
08:14:44 Crash Fire Tender leaves airport

Nothing in the report suggests that the engines began to run down before the fuel was selected to cutoff. The report states a sequence of events for power loss which begins with the switches being moved to cutoff. The maximum airspeed was immediately before the switches were moved, so there had not been a power rundown prior to that:

This is a preliminary report. It is quite detailed for a preliminary report.

Examining the before-takeoff checklists seems like it would be akin to examining the re-arrangement of the deckchairs before the titanic even hit the iceberg.

The engines were switched off. Unlike Embraer, B & A have no protections stopping you switching an engine off inadvertently. From everything in the report, everything operated exactly as designed. I am not certain of how long the relight window is without windmilling speed, but +- 10 seconds seems entirely reasonable.

The outstanding question that presumably requires much more in-depth investigation of the wreckage items and CVR audio is whether:

• the cutoff switches were operated deliberately (and by who)
• the cutoff switches were operated inadvertently (and by who)
• the cutoff switches were bumped (by what) and the guards failed or weren't installed
• some electrical failure perfectly mimicked both many-pole switches being operated, then being operated again (seems unlikely)

The Service Bulletin (link below) referenced on page 6 of the preliminary report describes just that...fuel control switches without detents or what the bulletin describes as a "locking feature" that can be "disengaged" and still allow the switch to function. It's somewhat of a glaring omission that the report did not state the status (detent or not) of the switches on this aircraft. Presumably if no-detent switches were found then an emergency AD would already have been issued.

https://ad.easa.europa.eu/blob/NM-18...SIB_NM-18-33_1

Wouldn't they already know if the detents were missing in this case? They recovered the switches and told us what position they were in at impact.

The Preliminary Report clearly states that the co-pilot was the Pilot Flying (PF).

Right.
I want you to think about what you just posted very carefully,

They would say that, wouldn't they?
But is it a fact?

Maybe it is, and maybe it isn't. (And I honestly don't know).

I offer you MH 370 and the various punting that the Malaysian government did as a point of reference, as well as China Eastern Airlines Flight 5735 as a point of reference.
Yes, I confess to you, I tend to be cynical.

I haven\x92t seen this question asked and answered so apologies if I\x92ve missed it.

What observation(s) would or could have alerted either pilot to the fact that the fuel cutoff switches had been set to CUTOFF?

Not on the take-off roll. It was 3 seconds after liftoff.

If there was some kind of Stabiliser error message during the timeline of this accident it would certainly be mentioned in the preliminary report. I am sure that the investigators would have noted it and arrived to similar conclusion you did. A Stabiliser error message would be too relevant piece of information to ignore it in the preliminary report.

I hope this isn't too far off-topic, but a question raised a few times in the days after the crash was why we only had cell-phone video and foreshortened security camera footage from buildings near the airport. Why didn't the airport save 4K video of every takeoff? (I think this came up for Jeju too.)

The preliminary report includes a hi-res image of the aircraft shortly after takeoff. The airport _had_ good video. I would guess many do, and in this case the investigation team thought it was useful to release a still from it.

Thanks for your comment. Agreed, but why did the report make mention of the Stabiliser fault on the previous sector? If this is completely irrelevant, why was it mentioned at all? There a quite a few specifics that are missing from this initial report, such as specific CVR information (what was actually said by the pilots and which pilot said what)? The report also says "...The EAFR data downloaded from forward EAFR is being analyzed in detail..." This indicates that more is known than is in the report. I suspect that the initial report was put out to meet the "30 day rule" and there will be further interim reports before the final.
Fly Safe
PJ88

Um, the flap and gear levers are a totally different design and they look, feel, operate differently. They are not even co-located, and occasionally people confuse them, withstanding decades of design efforts.
The fact that EICAS messages were recorded does not mean that they were provided in the preliminary report.

The notion is that around liftoff EICAS reported an error related to an error logged on the previous flight, that the PM felt it prudent to remedy the problem by cutting the stab cutoff switches, inadvertently cutting fuel. Action-slip, as mentioned countless times in these threads.

Really? It suggests to me and I would imagine the vast majority of us who have flown modern Boeings that they were physically moved, by one of the crew, one at a time, the question is why.

The accident aircraft was written up for a status message of ”STAB POS XDCR” on the previous flight, which is a message relating to implausible data from the stab trim switches. It was released from maintenance (according to the preliminary report) at 06:40UTC ahead of an 07:40UTC departure (the crash flight) with ”no fault found”.

On the 787-8, as all modern planes, switches are not cabled as dry closing contacts all the way from the switch poles to the affected end devices (FADECs in the case of fuel cutoff switches), but rather connect locally to an analogue/digital converter to encode the switch position data onto the digital comms bus ARINC629 which allows all aircraft systems to talk to one another.

Are the fuel cutoff switches, which are positioned adjacent to the stab trim switches, connected to the same ADC module which produced the error message on the previous flight, which maintenance was unable to resolve before the accident flight took off? I do not know, but it must be worthy of being looked into.