Posts about: "MEL" [Posts: 29 Pages: 2]

The AC wasn't working while at the gate on the previous leg, so it may be that they APU was broken. Been on several filghts where this has occurred, so the APU presumably isn't on the MEL.

If it isn't listed in the MEL then it can't operate the flight.

Without getting into how an MEL actually works, here's an excerpt from an actual 787 MEL.



AGCU = APU Generator Control Unit, VFSG = Variable Frequency Starter Generator. IDK what exactly the AGCU does nor why the left one is important.

Firstly, condolences to all those involved.

Secondly the above is a load of rubbish, as someone who also 'trains and checks' pilots and also has many years of Safety Investigation within large airlines it is a semi regular occurrence to depart with incorrect or no data.

Tiger took off in Sydney with NO data in the FMGC,
Singapore had a tail strike in AKL after inserting the ZFW as the TOW
Emirates almost crashed in MEL for similar reasons.

Not saying that this happened here

Air NZ a few years ago almost put a 787 in the water out of Rarotonga as they had 100' in the FCU, took off, engaged autopilot and the aircraft pitched down and thrust came off, pilots recovered it at 60agl.
Emirates has done similar, so these things happen.

Clearly we don't know what happened here but I think it fair to assume it went wrong at rotate given the gear stayed down which would suggest a distraction at that point.

That is the opposite of how an MEL works. Is it school holidays?

This aircraft has got airborne well within the requirements of FAR 25 under which it was certified. It has over 1250m ahead of it passing around 35' based on the video from behind, so the FMC data was not incorrect, the thrust up until after TO was not incorrect, and the CG is not out of range, the time to rotate is within expected range, and the attitude at liftoff is not excessive, the plane is not heavier than expected. This is not Emirates, Tiger or SQ, it may have a resemblance to AFR out of Nigeria, or ANZ out of Raro, or UAL out of Hilo. Unlikely but there are similarities.

A low altitude in the MCP can become pretty interesting, as will a TAT probe failure to the ATR thrust limit. Both cases will have the thrust levers moving back rapidly. There is no obvious failure of the engines at this point save the question that the RAT may be deployed. A transient electrical fault tripping the logic for the RAT is hard to imagine, but that would possibly end up with an ATR fault and power coming back to idle. Fuel contamination is not impossible, but it is improbable, the engines would have been on their TO configuration from the engine start, and the taxi and turnaround takes enough time to flush the fuel lines, being longer than the selected tank sampling time that sits behind the SOPs. Boeing aircraft are easier for the crew to detect anomalous thrust commands compared to the Airbus, however, if the RAT is out... then more was happening.

The flaps are in the correct position, we are looking at a time critical failure for the crew, they appear to have around 10 seconds between onset and impact, and they have rotated the aircraft in the later stages, as any reasonable pilot would do, and that certainly does not indicate a crew initiated problem on the available information. Unlawful interference is unlikely, given the RT calls that have been made.

The IDGA AAIB is not known for rapid response, this event is of international importance, it appears that it is being treated as such by the authorities involved. The EAFRs on the 787 will tell all soon, and we need that information, this is a globally important aircraft type.



early doors then after a certain time they close. Or gear left down for brake cooling in the MEL

TCMA is on both the Trent 1000 and GEnx-1B 'basic' - it was required for certification. There is no reason for TCMA to be listed in the MMEL as the only 'functional' portion is the via the electronic overspeed protection system (which is required for dispatch - no MEL relief) - the rest is software resident in the FADEC.

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.

Others have been asking if there were potentially a number of deferred items on the MEL, not the most outlandish possibility given some of the AI stories on here and elsewhere. But as you\x92ve said, a failure mode that goes from blocked pitots to a dual engine failure at takeoff sounds like the plot of a bad film

2008, a Spanair MD-82 crashed in a similar way after liftoff in Madrid. Final report Spanair .Main cause: The pilots did not configure the airplane according to checklist and took of with zero flaps and slats. Contributing: previous maintance was disabling RAT heating (MEL if not flying into icing conditions) which somehow inhibited electrically the takeoff configuration warning. I am not implying in the least that such a thing happended to this Air India crash. I just mention it as a proof that some *minor* quirks can contribute to an accident (i.e. disturb FADEC, TCMA logic, you name it) . Modern aircraft software logic is even more complex than the wired logic of an MD-82. But still: all "IF so and so THEN so and so " code can produce weird results if the conditions are corrupted or delayed by data communication lags. And according to a witness, there were some electrical quirks on the previous flight and possibly some maintenance thereafter. Again not implying any wrongdoing.

I’m an ex-787 pilot. There are a number of defects on the 787 where you can dispatch under the MEL with an operational procedure that requires the gear to be left down for varying amounts of time after takeoff. You probably saw an aircraft that was carrying one of these defects. Routinely leaving the wheels out to cool the brakes isn’t really a thing on the 787, despite lots of spotters thinking it is. In normal operations if you see a 787 with the wheels left out after takeoff it’s almost certainly dispatched legally under the MEL and carrying out the associated operational procedure.

Why is that required for certification? Slamming the brakes and cutting fuel should do and has always sufficed in pre FADEC era. Going full power when the throttle cable brakes has been considered the safe state.
Where does that piece of software reside by the way?

TCMA is on both the Trent 1000 and GEnx-1B 'basic' - it was required for certification. There is no reason for TCMA to be listed in the MMEL as the only 'functional' portion is the via the electronic overspeed protection system (which is required for dispatch - no MEL relief) - the rest is software resident in the FADEC.

Firstly, condolences to all those involved.

Secondly the above is a load of rubbish, as someone who also 'trains and checks' pilots and also has many years of Safety Investigation within large airlines it is a semi regular occurrence to depart with incorrect or no data.

Tiger took off in Sydney with NO data in the FMGC,
Singapore had a tail strike in AKL after inserting the ZFW as the TOW
Emirates almost crashed in MEL for similar reasons.

Not saying that this happened here

Air NZ a few years ago almost put a 787 in the water out of Rarotonga as they had 100' in the FCU, took off, engaged autopilot and the aircraft pitched down and thrust came off, pilots recovered it at 60agl.
Emirates has done similar, so these things happen.

Clearly we don't know what happened here but I think it fair to assume it went wrong at rotate given the gear stayed down which would suggest a distraction at that point.

the answer to that was already provided earlier

One comment here, and maybe I am mis-understanding your comment, but the landing gear only operates via the center hydraulics. It does not matter whether the Left/Right engine driven hydraulic systems are operative or not. The RAT will only pressurize the primary flight control portion of the center hydraulics.
No idea. I only got that info from the Master MEL on the FAA website. According to the MMEL the aircraft can be dispatched as long as there is one of each type sensor working on each main gear. (AIs MEL could be more restrictive)

Thanks again. Yes, I checked the MMEL too. It also says that the aircraft may be dispatched with one of two TCMA functions operational . Edit: dragon6172 has pointed out that the cited MMEL entry for TCMA applies to Rolls Royce engines, so not relevant here.

If this happens, and hasn\x92t yet led to a fatal accident, is it possible over say incorrect or no data could lead to a fatal accident (not saying it happened here).

Could incorrect or no data coupled with other issues (eg hydraulics, electrical or engine failure) lead to a situation that might have been recoverable with the correct data being unrecoverable?

To continue with some more speculation (hopefully not idle!) one of the areas I haven\x92t seen much discussion on is maintenance errors. Clearly all aircraft are under a continuous regime of maintenance, whether scheduled or unplanned. In my time long ago we had many specialist technicians on hand to deal with most eventualities, time was always of the essence, but there was a strict process of checking and sign-offs for every bit of technical work carried out. OK, it was the military, but I can\x92t imagine it\x92s much different today in the civil world.

But of course mistakes happen occasionally, leading generally to nothing worse than a cancelled sortie, or less commonly for the aircraft\x92s built-in redundant systems to \x91kick in\x92 or be switched in. On the ground the fault might be on the MEL, in the air a diversion might be necessary. And this was decades ago. What I\x92m leading to is this; on an ultra modern commercial airliner such as the 787, what possible maintenance error could cause such a catastrophic event as happened to AI 171?

We understand the right engine was replaced 3 months ago, and doubtless there have been other regular, routine activities necessitating disturbance of engine, avionic and other systems. One could imagine perhaps an electronic piece of equipment (we called them LRUs) not being fully located in its housing, ditto for plugs and connectors, and such equipment apparently working correctly at the time but failing at a later time. There are anecdotal stories of AirIndia 171 on earlier flights having air conditioning and in-flight entertainment issues. And we don\x92t know what, if any, maintenance/repairs were done immediately before the last flight.

But isn\x92t all this irrelevant, given that, we are told, the 2 engines and controls are uniquely independent of each other and will continue to work in the presence of aircraft major electrical and hydraulic system failures?

In summary, and assuming accidental rather than deliberate, there seems to be no way that double engine failure could result from maintenance error?