Posts about: "Mayday" [Posts: 144 Pages: 8]

Can anyone familiar with the 787 built in overspeed protections comment on what could possibly override a pilots TOGA button command or fire walling the throttles?

I am presuming that at some point just prior to the mayday call the pilots would have just commanded \x91full\x92 thrust and received no or a significantly mild response.

I don\x92t think fuel contamination, birds or anything else external to the aircraft affected this crash. There is no evidence of it.

could some combination of already MEL items and one or more faulty inputs to the computers cause the aircraft to \x91protect\x92 itself into the ground? Regardless of throttle position?

I am thinking - ground/air logic, faulty airspeed sense, faulty AoA sense or other.

At this point in time, I'm not sure we can rely on what was reportedly said in the mayday call. There are conflicting reports about what was actually said, even before we get on to transposition / interpretation of the contents - see, for example, Auldlassie's recent post (which may have crossed with your own) - and I still haven't seen a reliable source offered up for the original transcript.

There is at least one other. RTO? Who was flying. At V1 the tension can be too much for an inexperienced FO who is flying. The mayday may have been spoken by the FO, after Captain tried to snatch controls back. It would explain an inexperienced left hand on the levers, and a non concert close of the throttle(s)

Unless....Captain was guarding the throttles, Initiated abort, and rethinks. Engines run, and run, and run.... They die of thirst.

Praying for an unbiased investigation and report ... Somebody needs to learn how to keep the lights on

I agree. It is intriguing that we have none of the radio communication released. As a result, we do not have confirmation of what was actually said during the Mayday call, and no ability to deduce who was the PF and PM.

Unless the mics are closed, it's in the CVR
For me, I don't need to know.

Like many (most?) here, I really don't have a theory/guess that I would call 'high confidence'. Among those who do, many of them seem to rely in part on RAT deployment. I can't say whether it was or not. I do not believe any of the available pictures and video confidently attest to the situation from a visual standpoint. Regarding 'RAT clearly audible' I would say that we do not know that either. That audio is taken from camera phone video. It seems entirely possible to me that the sound in question could very well be a scooter, or some other ground vehicle that is much closer to the camera than the plane is. So anyone who is confident of RAT deployment has to be equally confident that the sound we hear (I agree there is a sound) could not possibly be anything other than a RAT. That seems a bit of a heavy lift to me. Any number of audio sources not visually captured on the video could have produced that sound. I am certainly not intimately acquainted with the sound of every tuktuk, scooter, piece of construction equipment, etc. that are common on the ground in Ahmadabad. We'll know soon enough but the evidence we have only weakly suggests a deployed RAT.

The Mayday specified loss of control and engine failure.

Alternatively, it could have been exactly what was stated...loss of control and engine failure.

It takes some neck to accuse a veteran captain of panicking.

There have been conflicting reports about the call to ATC. Original reports quoted the Captain saying "Mayday...no thrust, losing power, cannot lift". But I've seen reports today stating the call was simply "Mayday, Mayday" and then no further response.

Difficult to confirm so I wouldn't put too much weight behind it until something more official is released.

It would also depend on how much is allowed? Surely the investigators will be allowed to hear it? No? Would think it a prerequisite to a full understanding of the flight

2 separate calls ? Last one just mayday mayday ? In this context reporting of power failure is engines not electrical , an electrical failure at that point would be of little interest compared to engines providing no thrust . My thoughts only but if he knew what had caused engines to stop producing thrust he\x92d not be on the radio . I think he\x92d be trying to reverse the cause ? Unlikely an experienced LTC would not see two handles / switches off ?

Several hundred posts ago, a link to a PPrune thread re 787 RAT deployment was posted. I am sure everyone posting has at least seen if they have read the thread....

I apologise, if my thoughts have already been posted - please delete if this is the case, I cannot find them in the main thread though

None of us know if there was no engine failure, single engine failure or double engine failure.

If RAT was deployed, we do not yet know whether it was automatic or manually deployed by a very experienced captain because "We have no power. What harm can it do now?" (Electrical power, not thrust) Would the Captain also elect to start the APU in the few seconds he had?

In the thread re 787 RAT deployment, some one states that a single engine failure, due to the small rudder size on 787-8, automatically throttles back the remaining engine as the rudder will not be able to correct the course. I am not clear about the guards around this - be they height restrictions, speed restrictions or % of power delivery. If there are any guards in the software. It may have been stated and I missed it or didn't understand.

However, as someone involved with critical software design & development, if the generators were "playing up", which is highly possible given passenger observations on previous flights, could there be a window, if the aircraft experienced a problem with say no 1 engine ( suggested in video "analysis" despite the aircraft tracking right ) whereby the loss of electrical power triggered the software to "throttle back" No 2, and that again limiting any recovery of No 1, if the generators on 2 didn't perform/react as planned. Software always has holes.

The primary flight deck screens have battery backup - but do they lose power when the main buses go offline - and/or again when the RAT delivers? Or is it seemless? Previous posts mention both scenarios but with no answer. Are there flickers, resets, reboots? All distracting at best and time limiting at worst.

I think a pertinent point posted earlier, was that the problems seems to have begun with "gear up", a lot of load on the electrically driven, hydraulic pumps.
Seemingly started, but obviously not completed.

I believe the 2 guys sitting in row 0 dealing with this, were just passengers from the moment it left the gate - for whatever reason. The mayday call, by whichever pilot - although no transcript officially published - was probably a last ditch attempt to alert ATC asap to a situation with a clear outcome. Very sad. It is bad form to point the finger before any useful facts are confirmed.

So, I suspect generator problems & a hole in the software and/or logic due to timing issues caused by generators appearing to be on/offline -maybe rapidly - restricting thrust by design..

If the apparent asymmetry of thrust caused the yaw right seen in the video, a Mayday call would be in there somewhere.

SLF here. Nothing to add but I am impressed by whoever made the mayday call in those extenuating circumstances. Aviate and navigate are no longer an option but it takes calm presence of mind, fortitude and professionalism to do that.

The mayday reports are so unreliable / inconsistent that you simply cannot base any theory on these alone. It is best to focus on some other aspect at this time.

Some have questioned whether a solitary 'communication' was optimal, given the timings, circumstances and the prioritisation of aviation & navigation. I see both sides of that particular argument. But the idea of making a second call during a flight that was airborne for less than 30 seconds to repeat a mayday? I find that hard to believe.

I agree that it has been inconsistent, but for what its worth, the most recent version which seems to have come from a press conference on Saturday and being quoted by the likes of CNBC and News18, is that there was a single call lasting 5 seconds from the Captain which read:

\x93MAYDAY\x85 MAYDAY\x85 MAYDAY\x85 NO POWER\x85 NO THRUST\x85 GOING DOWN\x85"

I think there is uncertainty about contents of mayday call. Most media mention the word mayday with no reference to thrust etc. I wonder if conjecture has become fact.

No evidence of engine failure - Not true. No engine noise on video where you would expect TO or TOGA power to be in use. Mayday call stating No Power

No evidence of RAT deployment from a poor image . - You can argue Not from the Image but...: 2 independent audio analysis of the video audio shows the sound comes from a deployed RAT plus JB's video. Plus the guys who live in SEA having heard 100's of RATs deployed during test flight have stated that the sound is a RAT.

No evidence of electrical failure . - Not true. Reported cabin emergency lights going off, FR24 feed stopped just as in the 737 South Korea incident in December. APU intake door partially open at crash scene, suggesting an APU autostart.

Now you can call into question the above evidence but to state there is none, is simply not true.

So one thing to keep in mind, the RAT can be deployed manually, but also comes automatically when certain conditions arise, everybody here is assuming it\x92s only on dual engine failure but there are 4 more conditions that trigger the RAT,

- all three hydraulic system pressures are low

- loss of all electrical power to the captain and first officers flight instruments

- loss of all four EMP\x92s (electro motor driven pump) and faults in the flight controls system occur during arrival

- loss of all four EMP\x92s and an engine fails during take off.

This all comes directly from B787 FCOM,



If we assume that what our survivor saw is correct, maybe it was an electrical failure, the aircraft had electrical issues in Delhi during departure and I checked the crash video again, I don\x92t see the strobe lights (neither wing or tail) and also no Anti collision light either. this might also explain the self starting APU on loss of the electrics (engine driven generators). That could also result in a loss of situational awareness with the speed, because of no indication, even the HUD would not work. The mayday call would still be doable because the radios work from the battery.

Can we focus on theories explaining the facts? Specifically:

• Aircraft used almost the whole runway (3500m)
• Flaps found on the ground in setting 5
• RAT deployed
• Mayday that they lost power

this rules out flap up instead of gear up , selecting wrong autopilot setting, gear up causing electrical faults (as problems started earlier - using up all runway). Something must have happened on the runway (after v1?) that led to loss of electrics (and dual engine failure, maybe later?)