Posts about: "Maintenance Error" [Posts: 12 Pages: 1]

That would require deep dive in the maintenance records of that bird, and it's ludicrous to think we'll be able to figure it out. To cause dual engine failure at "gear up" callout (everybody's nightmare, unrecoverable) - that needs to be either drastic, super weird, or malevolent. And that hole goes too deep for us to guess.

In less than a month we'll have a preliminary report.

I'm not quite sure that one counts as a design flaw? If we were to try to list all the times that cocked-up maintenance/repair led to an accident we'd probably run afoul of the character limit...I tried to keep the list down to things in the design that actively increased the probability of or exacerbated the outcome of an accident (like the DC-10 cargo door loss being able to collapse the cabin floor). In any case the grounding came two weeks after the accident, no? Pretty quickly, but not exactly three days.

This accident too could well be down to a maintenance error, but given that the investigators are not magicians, I don't see how they'd be able to say so with confidence after just a few days. Surely they'd need to review logs, do some lab analysis, etc for that? Perhaps worth noting that an inspection of Air India's 787 fleet has been ordered, but I've seen it dismissed as a CYA move. Might not be...

I must admit I'm confused. If there was a maintenance error involved in this accident (which is what I said would take some time to uncover), how exactly would either flight data or cockpit voice recordings tell the investigators this? Please correct me if I'm wrong but every maintenance screw-up leading to an accident that I can think of was surfaced by actually examining the wreckage and logs, the former sometimes using quite sophisticated lab methods.

Pilot error still seems to me like the only thing that could be conclusively ruled in after only a few days, and it may well be the case here, I'm not contesting that. But that does not mean that other factors can be ruled out after a few days - absence of evidence is not evidence of absence and all that.

Let's postulate that engine rollback and subsequent complete electrical failure coincided with selection of gear up. The recorders will tell you that happened, and in consequence that the flight was unrecoverable, but they probably won't tell you why, especially if the event was the result of an interaction between a latent design weakness, a maintenance error or errors, and/or an unusual control input. The recorders will clear up the control inputs, most importantly whether the engines were deliberately shut down. If there was no unusual control input the cause must be a design weakness, a maintenance error, or more likely a combination of the two, the error exposing the weakness.

That is exactly what I am saying - that the only cause that can be positively identified at this point is pilot action whether accidental or deliberate. It's the only thing that can be conclusively ruled either in or out by now. However the tone of several of the messages here is that everything else has conclusively been ruled out because it has been three days, which makes no logical sense to me.

To put it another way: if pilot action isn't the root cause, then what exactly is the investigation supposed to say right now other than the utterly redundant "well this is a headscratcher, and we're going to take a while to figure it out"? Are they supposed to turn into Chicken Little screaming that the sky is falling with no evidence-based justification? To be fair, you could perhaps argue that they should come out and "clear" the pilots' names, but that implies an obligation to social media hucksters and mobs that I don't think should exist.

Also we should be wary of treating it like an either/or; poor crew response to a manageable fault stemming from a design weakness or maintenance issue is also an option. See e.g. the Swirijaya crash that was initiated by a faulty autothrottle, but the resulting upset was quite preventable and also recoverable even after it had developed.

I recall an extremely pissed-off Freddie Laker expressing his view that it was a maintenance error and that "the last thing you should do is graunch the engine up there with a forklift."

There is a possibility that doesn\x92t get much air time on this forum that satisfies all the \x91facts\x92 ( pprune facts mind you), and requires less mental gymnastics to believe than many of the theories put forward. I\x92m not saying it\x92s what happened at all but it seems much more likely than a TCMA fault to me.
This link is to a Japanese report on a Jetstar 787-8 with GE engines that had both engines drop below idle while airborne due to magnesium salts effecting the operation of the FSV spools. The Magnesium salts came from a biocide dose by maintenance two days earlier.
For some reason I can\x92t paste the link but if you google JTSB the report number is AI2020-2.
I think it\x92s quite easy to imagine that a simple maintenance error ( 1000ppm instead of 100ppm) combined with extremely bad luck on timing lead to this accident.
I think I\x92m favouring a theory like this for its simplicity and the fact that fuel is the elephant in the room when you are dealing with a dual engine failure.

That’s really interesting, I’d not heard of that incident. The report does say though that particular biocide had been withdrawn due to other engine thrust occurences.

In that report, the factual conclusion is:

4. PROBABLE CAUSES
In this serious incident, it is highly probable that, when the Aircraft was descending for
landing, there occurred oscillation in rpm of each engine causing both engines to temporarily fall
below idle at separate times because Residue primarily composed of magnesium salts accumulated
in spools impeded movement of spools that involved in fuel metering of both engines.
(emphasis added)

and the narrative taken from the pilots is that while they happened in short order, the engine issues were not simultaneous. Not to say they couldn't be simultaneous, but they weren't. Also, the problems arose in the descent, as the engines were throttled back. Again, not to say it couldn't happen in the take-off, under full power.

What you are pointing to is a maintenance error, in terms of "switch not catching/functioning properly" but (for some reason, pick one of many) not replaced.
On both switches.
The above is also, consistent with your caveat, a speculation.

Absolutely, if the correct "catch" is part of regular maintenance; is it? Besides this: It\xb4s all about errors, isn\xb4t it?

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?