Posts about: "EICAS" [Posts: 79 Pages: 4]

Tell me you've never been an airline pilot without telling me...

An unresolved difference in TLA between the channels is quite unlikely - the fault detection algorithm is quite good (sine squared plus cosine squared) - but it can happen. In the old days, we'd default to the higher TLA, but since the feds became preoccupied with Uncontrollable High Thrust, we tend to select the lower value. Worst case would be to default to idle. The fuel switch discrete doesn't really get used except for engine start - if it falsely indicates shutdown (on one or both channels), the FADEC won't do anything if the engine is already running. All this will set maintenance faults - and associated EICAS Status messages (L/R ENGINE CONTROL or ENGINE C1). I doubt that would be recorded on the DFDR - it would go to the QAR but that's unlikely to survive a crash. It would also be logged in the FADEC NVM - but again no guarantee that would survive either (although when the Lauda 767 crashed due to the thrust reverser deployment, the DFDR was destroyed but the FADEC NVMs both survived - much of what we know about that crash came from the FADEC NVM.)

Again, not familiar with the specifics of the 787, but on the 747-400/-8, one pole of the fuel switch feeds EICAS - which uses it in various message logic - and sends it out to any other aircraft systems that use it. There is "Digital Flight Data Acquisition Unit) DFDAU (pronounced Daff Du) that takes all the various system digital signals, sorts them and provides them to the DFDR and QAR. The 787 has something similar to the DFDAU but I don't recall what it's called.

Sorry if my wording was not precise here - I meant the fuel cut off switches that more or less caused this accident.

It was stated earlier that 2 of the poles in the switch are wired to separate Remote Data Concentrators. The RDCs feed data into the Common Data Network (essentially an Ethernet LAN).

The EAFRs simply sniff the required data from the CDN, so there's no DFDAU as such.

For some parameters, including the fuel cutoff switches, the EAFRs also record a "Source Index." For the fuel cutoff switches, there are 4 sources numbered 1 through 4 as well as a valid/invalid flag. I don't know what the sources are, but perhaps they're the 2 RDCs plus the 2 channels of the EEC/FADEC. It appears that source 1 (the default) is not the EEC.

787 has RDC's - Remote Data Concentrators. Doing the same function. Two of the switch pole-sets go each to one of 2 different RDC's, that feed the EAFR's / QAR, and the common core network so that any system that wants to know, can. The wiring is positive voltage from the RDC's to the switch and to GND through the common pin. So the RDC's would be able to detect anomalies such as both contacts open, or both contacts closed. The EAFR will see two independent channels per switch.
The other 2 contact sets feed latching relays (again driven each coil independently by dropping to GND at the switch) that then drive spar valves and reset signals to the FADEC Channels. (and more).

So - for the benefit of those that hang on to the 'possibility' of electrical gremlins and 'ghost' switch signals.

Each switch has 4 mechanically separated 'channels' - 2 of which do electromechanical things to the engines through separate paths, the other 2 feed through independent paths the FDR and the rest of the computer systems. The results of the electromechanical actions also feed back to the FDR.

Thus the readout from the EAFR will PROVE that the switches MUST have been PHYSICALLY MOVED.

And - I'm nervous to challenge you tdracer - there's quite the authority gradient and I know I'm at the bottom end, but I can't let this fly...
Its 'Deefer Doo'. Fight me.

Well this is probably why it took 10 seconds, whole right side of the flight deck would be blacked out. My guess is that the EICAS messages that you see during sim engine fires/relights training helped. Don't have the post but it exists earlier upthread but there is an fuel cutoff EICAS message that happens when fuel switches move. Obviously can never count out a side vision of the PM, especially if its not a traditional movement in that stage of flight.

Switching off the engines would cut power. (the RAT deployed before they overflew the end of the runway) The HUD would go blank. As would most of the display units. The lighting would change. The hissing of conditioned air would stop. Various 'noises' would cease. The engines sound would change dramatically, and they would feel the deceleration. The one EICAS screen remaining would be generating all sorts of messages. It would be obvious that power was lost.
I cant speak for how long it would take to connect the dots though.

Not a B787 pilot but many hours on its wide body predecessors.

It is conceivable that you could notice hand movement around the throttle quadrant in your peripheral vision (noone's hands are on the thrust levers between V1 and shortly after takeoff), however even if you didn't, you'd immediately notice the loss of performance. The instinctive reaction is big loss of performance -> quick glance across at instruments -> why are they winding back? Also if the fuel control switches were moved to cutoff you'd suddenly get EICAS messages saying the engines were shutdown. So there are immediate clues and it's only a minor head movement to see where the fuel control switches are because they're right down there behind the thrust levers. Then the immediate action for a dual engine failure, which would by then likely be obvious with both sets of instruments showing everything winding back, is "fuel control switches cutoff, then run". There is no significant pause in that action because it's only to reset the electronic engine controls, so the 10 second gap between setting them back to "run" is not explained by the dual engine failure procedure but perhaps by a startle factor. One way or another, your eyes are going to end up checking where those switches are.

Display and Crew Alert (DCA)/EICAS would indeed receive signal about Fuel Cutoff switches (L&R) position and written to EAFR (source:
https://data.ntsb.gov/Docket/Documen...man-Master.PDF )

Having seen it today, fuel control switch to cut off produces a L/R ENG SHUTDOWN EICAS message almost immmediately or ENG SHUTDOWN if both. No aural warning. Generators instantly off line therefore it is likely all FO instruments blanked. Definitely a startle event for the PF in this case.

I've been 'arm chair' flying this scenario and I imagine (for me) the sequence would go something like this.

I'm pilot flying, so my gaze and attention is firmly out the front rotating to the planned takeoff attitude.

Initially and in no particular order:
- I would feel the loss of thrust as a sudden loss of acceleration.
- There would be a significant nose down pitch trim change that I would feel through the yoke.
- There would be lots of audio cues: Changes in engine and air conditioning noises. Lots of click-clacking as electrical relays change state with the loss of electrical power.

My eyes would be drawn inside. I would notice blanking of some of the displays and then look to the EICAS display. My first thought would be probably that we have suffered a major electrical malfunction. There would be lots of messages. I'm not B787 endorsed, but presumably close to the top of the messages would be ENG SHUTDOWN. This message is shown when 'Both engines were shut down by the fuel control switches or the engine fire switches.'

I think I would then look at the fuel control switches and seeing them both in the cutoff position I would say 'why did you cutoff' or stronger words to that effect.

After that it all depends on the response of the other pilot. If they are uncooperative, I would be putting the fuel control switches back to run. All whilst frequently checking and adjusting my flight path.

With all the ‘experts’ swimming about on this thread, I’m very loathe to dip my toes in the water for fear of sharks but…

Having read the vast majority of postings here on this accident, plus the prelim report, I can’t see how anyone could dispute that ‘someone selected both FCS’s to cutoff Immediately after lift off and before gear retraction’. Which, as all have said, begs the question, was it intentional? A brain fart? Or a “I gotta do this now because of a perceived problem”? I can’t think of any other option.

Like all Boeing pilots (current or retired) we’ve all had a quick and dirty education on a system called MCAS - which is of course a 737 Max issue, but…one does wonder.

The accident aircraft had a stabilizer snag on the previous flight. The accident crew would’ve noted it in the log. Is there a chance that, just at lift off the EICAS stab warning/caution reappeared and the PM thought it would be pre-emptive to turn off the stab trim switches? BUT…muscle memory, startle factor, etc, he grabbed the wrong (but more familiar) nearby switch(es) and selected them. In the ensuing maelstrom, the gear was forgotten, the PM desperately tried to put the FCS’s back to RUN, the PF was struggling with a blank panel but it was too late airspeed and altitude were heading south and… they flew directly to the crash site.

Grasping at straws, I toss this hypothetical scenario into the pool - probably because I just can’t get my head around the ‘intentional’ option.

Now…where did I put the shark repellant.

There is no way any pilot would be touching the stab trim switches right after rotation. It would go against every aspect of training. If the aircraft is flying ok you would never touch anything trim related until after cleanup and working the appropriate QRH or EICAS. I know some will bring up the Delta flight at LAX however that occurred above a 1000 feet and was in compliance with company policy and Boeing at the time where you got one free punch to reset the EEC.
It would also have been a data point on the FDR and in the preliminary report.

bluemic

How\x92s the water in that shark infested sea?

When I read that on the previous sector the aircraft had a stab issue written up I wondered the same thing. It\x92s a fanciful theory but they all are. I\x92m leaning towards the action slip \x93brain fart\x94 although why might always be the subject of speculation. Assuming that the captain did place the fuel control switches to cutoff just after rotation then whatever the explanation will most likely defy logic.

Incidentally this tragic accident wasn\x92t discussed that much in my company even though it operates the 787. I think there\x92s a realisation that it would be pointless speculation until there is the final report. What was noticeable early on is that we\x92re no maintenance actions mandated by Boeing, GE, the FAA etc. Equally nothing from a flight ops perspective.

This has been discussed to death previously. I suggest looking for tdracer's excellent insights into FADEC design and implementation. From the beginning we've been discussing various very rare types of circumstances. Based on the preliminary report we can now lay most of those to rest.

Which actually brings me to this one because I would like to ask for a bit of clarification: By "fuel switch discrete" are you referring to the Fuel Control Switches discussed in the preliminary report?
I would assume from your statement, that if a mismatch in the NC/NO signal on the switch was detected the FADEC would not direct the Fuel Cutoff Valves to close (as far as the types you are familiar with are concerned), is that correct?

The report states:
So this would then mostly preclude the possibility of one or both switches being faulty electrically.

The report then states:
There is a 10 second gap between cutting fuel and re-enabling it and a 4 second gap between switches during re-enabling. Is there a mechanical reason why these switches would be slower to operate in either direction? There are obviously reasons such as startle factor and stress that might negatively affect the speedy operation of switches by anyone, but I am nonetheless curious if this might not be a pointer to some sort of mechanical issue after all, such as asymmetric wear or FOD.

does the ORDER in which the switches were operated give us any clues which seat operated them? I would suspect that most pilots always go left switch then right switch, or the right then left each and every time when switching off. We are creatures of habit.

I haven't seen it mentioned it yet that if the stabiliser cut out switches had been left in the wrong position from the previous maintenance, when would EICAS or some other system alert the pilots to this? Would the alert be in close proximity to when the fuel switches were moved?

As others have said I think what this episode has revealed is it's too easy to turn off the engines in flight, and that the fuel cut-off switches should only operate when the relevant throttle is at idle? or should have a 10 second pause when no WOW signal

and a definite yes to cockpit video, protected so only accident investigators can access it. I can guarantee the third MCAS event wouldn't have happened if the 2 Lion Air MCAS events had been caught on video. It still shocks me after the first Lion Air near miss where the jump seater saved the day that the plane was released to service "nothing found". And as/when found cockpit video would solve the mystery of MH370.

Generally modern Boeing philosophy is left to right for either pilot.

The displayed EICAS messages are very different when an engine is shut down via the fuel cutoff switch vice other reasons. The EAFR records those messages. I am quite sure they have eliminated the TCMA as a problem in this accident.

Indeed, there are dedicated parameters for TCMA:

Eng1_TCMA_Shutdown_Local_EEC_A
Eng1_TCMA_Shutdown_Local_EEC_B
Eng2_TCMA_Shutdown_Local_EEC_A
Eng2_TCMA_Shutdown_Local_EEC_B