Posts about: "EAFR" [Posts: 153 Pages: 8]

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

Yes - conflicting data issuing a warning when the system being controlled has no fault. That's a problem at considerable expense for a rare occurrence.

Literally covering all the bases with a video would not only show what the switch status was but also how it got there, if it has an immediate effect, which a second line would not do.

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

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 Mods have stuck to this principle, which I shall try to adhere to.
This preliminary report is just that, but maybe consider the issues the Indian AAIB have had to address in publishing it. They will have a similar concern to the pP mods, maybe more so since any apparent accusations directed at the pilots may lead to physical retribution.
I therefore conclude great care has been taken to "sanitise" what the AAIB know, or at least strongly suspect, (from EAFR) into the report. They have conspicuously failed to identify which of the pilots was each half of the conversation they have not repeated the exact words, there's a lot missing (was positive rate ever called, was rotate ever called, any discussion about putting FC back to Run, who/how flying aircraft meanwhile). As a result we, the reader, should step back and not over-interpret this sanitised report.

Secondly, given the mod statement above, if a criminal act is suspected by the AAIB, this will likely trigger all sorts of 'primacy' issues in the investigation i.e. police? AAIB? or joint? and all the history that involves (SAS Linate?) - in Europe we have 996-2010 Article 12 para 2, but India?

Summary : For good reason I believe this report has been very carefully worded, sanitised with great care, and as such easy to inappropriately speculate what went on.

Was the RAT deployed manually?
The report says, This was 5 seconds after the fuel was cut off.

It suggests to me that the RAT deployment was initiated while the engines were still above idle and generating electrical power. Obviously one of the pilots could have done it via depressing the switch, as it's a "dual engine failure/stall" memory item (see Air India Ahmedabad accident 12th June 2025 Part 2 ) that won't hurt anything.

Is there a way for the RAT to deploy while the engines are still above idle?

I believe the fuel cutoff switches are one of the exceptions to this. They are direct wired. Stab trim may well be too.

I think they're called remote data concentrators - in many cases it is a conversion from a direct digital input to a bus signal; electronics would not call it an 'analog' input unless it was actually measuring a quantitative value.

I think I have seen a previous reference that the generators are disconnected when you select the switches to cutoff (or very shortly afterwards), not when the engine actually drops below idle. That could account for a few seconds of spool down time.

That is a very good question IMHO.

Loss of hydraulics or electrics will auto deploy the rat. The timing to me however seems to match up with when the engines were selected off.

If the thrust levers were found in idle but, according to the EAFR, were set to TO thrust until the end, doesn\x92t that also raise further questions? I mean: Of course, the impact causes compression at the nose, but the centrifugal forces act in the opposite direction. So, if there is an objective inconsistency here, and we have a pilot who says he did not operate the fuel cut-off switches, while the EAFR indicates otherwise, then we have yet another inconsistency.

Relevant section in the preliminary report

probably whatever bent the reverser levers also moved the thrust levers backwards, this is certainly no big mystery

On the "at *most* 1s apart" comment: no, that's incorrect. This has been stated above already but to recap: if the recording interval is 1 second, then having two events recorded on consecutive samples would mean that the gap between them was more than 0 and less than 2 seconds. You can say no more than that.

Regarding your second point: it has been noted by multiple posters that "the actual position" of the switch is a fairly meaningless concept for the EAFR data if you want to exclude the electrical signal arising from the switch itself. So I have to ask: what would you regard as a measurement of the "actual position of the switch", in this context?

You can generally sort out the voices based on the earlier chatter, pre-flight and during takeoff roll. This flight was short enough to capture all of that.

Industrial electrician here.

I have only seen a diagram for I think the 737. I remember there being a listing of what each pole did, but I can no longer find the post.

My expectation/speculation, though, is this:

The EAFR gets its information on cutoff switch position from the FADECs via data buses, similar to almost all other engine data. We have N2 information in the report after the engines were switched off, so clearly there are no concerns about this data not being captured.
This means that the FADEC's data of where the switches are is almost certainly the EAFR's data.

There are other poles on the switches that do other things - I think it was opening/closing the LPSOV and enabling the generators. The fourth pole in the 'cutoff' position was IIRC not used because the generators don't get a disable signal, whereas the LPSOVs are powered open in the run position and powered closed in the cutoff position.

If the switches were physically operated and in good electromechanical condition (not counting the possibly faulty gates), we would expect all four poles to operate essentially simultaneously, with the four 'run' contacts opening and the four 'cutoff' contacts closing. Not only would the EAFR pick up that the FADECs were commanded off, but also that the LPSOV closes after a short delay, and the generators drop offline before N2 drops below idle.

When the switches are moved back to run, we would likewise see the position of each LPSOV return to open.

(this does not necessarily mean that a person intentionally operated them, but that the lever actually moved).

If there was a wiring fault, contamination, or internal switch failure, we would probably not see this. Instead, you might see the LPSOV remain open despite the engine shutting down, or perhaps the FADECs trying to keep the engine running while the LPSOV has closed and shut off fuel, or the two FADEC channels receiving different run/cutoff signals - and all of this would probably happen differently on each engine (if it affected both engines at all). There is no indication of this in the report.

These are not your basic light switch where the load is either powered or not powered. They're four switches ganged together and operated in unison, and each channel powers either thing A or thing B. If you have both or neither A & B powered (for longer than the ~50ms that the switch takes to move between positions), this is a fault that should be visible in the EAFR data in some/many cases. Think valves being displayed in orange as 'position unknown'.

If all run contacts opened, and all cutoff contacts closed, the switch moved from run to cutoff .

I don't know whether they analysed the EAFR data in this much detail yet, but coupled with a potential click sound on the CVR, I think there's going to be very very little doubt at the end of the investigation whether the switches physically moved or not, and I strongly expect they did.

Does the EAFR record the electrical / physical contact of the RUN / CUTOFF switch or, does it record a software 'EVENT' which has the same 'signature' as the RUN / CUTOFF switch being toggled. My thoughts are that the RUN / CUTOFF switch never moved but, the underlying software / hardware system mal-functioned triggering a scenario similar to both RUN / CUTOFF switches being triggered

Some Boeing SB's describe circuit board failures triggering all sorts of unexpected / unpredictable failures

An answer to this is just a few posts back. Each switch has 4 sections which control different functions. It is not a single switch with software behind it. Multiple simultaneous separate failures would be needed if the switch itself did not move.

The short answer is that we wouldn't have CVR recordings if that was possible.

Basically, the cockpit voice recorder records the pilots incriminating themselves. It was only possible to get pilots to agree to have a CVR in the cockpit by assuring them it would only be used in accident investigations. For example, on the 787's EAFR you can read out the data on a laptop connected to the onboard network, but you can't read out the CVR unless you physically access the device.

Air accident investigations must safeguard that status. Their success depends on the guarantee that the investigation results can't be used to incriminate the pilots legally. But while courts cannot subpoena the CVR recording from the accident investigation, they wouldn't have to if the board released a full recording or even just a full transcript.

In my opinion, that is why this preliminary report is vague on who said what, and what exactly was said.

The CVR must not become a constant "anything you say can and will be used against you in a court of law" in the cockpit.

I'd be happy if any lawyers in the thread (e.g. WillowRun 6-3 ) could correct or confirm.

I think you're off track. In all jurisdictions in which I have professional expertise and qualifications, there are strict statutory limitations on the uses to which the content of on-board recording devices may be put.

I understand, to some extent, the reasoning for not publishing the actual recording as a general rule, but from my perspective the usual outcome is speculation that can be just as critical of the actions and skills of the crew, and be just as inviting to 'ambulance chasers' keen on litigation, as ripping the band aide off the sore and dealing with the truth. I remain of the view that the least bad way to get to the awful truth - whatever it may be in the circumstances of this tragedy - includes publication of the raw recordings of the cockpit and ATC. As many have already pointed out - correctly in my view - so much depends on the nuances of the language spoken, who said what, in what order, the cultural or other status of those in the conversation, the other sounds in the environment, all assessed in the context of the timeline of flight data recorded.

All one needs to do is consider the different meanings of "yeah nah" or "yeah right" in the Australian vernacular, which meanings depend, crucially, on context and tone and inflection and emphasis. Without that level of detail, paraphrasing or even quotes in transcripts are more often the source of increased speculation rather than the resolution of uncertainty.

So the board affected all the functions of both switches simultaneously and then restored all functions on both sides about 10 seconds later? I find that just as unlikely as the constant posts about a A350 suffering a single engine shutdown due to a liquid spill. For those advocating the liquid theory please take a close look at how the fuel control switches are mounted by Boeing verses Airbus. The Airbus design is very vulnerable to a liquid spill. The Boeing design by virtue of where and how it’s mounted is not.

While IMO the Air India 171 preliminary report ( PR ) in some aspects leaves ample room for speculation rather than soothing it, let’s not loose sight of a straight forward assumption that what is presently known to AAIB India beyond what is explicitly stated in the PR , at least to AAIB India’s judgement (and I presume amongst others NTSB's as well), shouldn’t lead to any significantly different preliminary observations and conclusions than those made in the PR at this stage.

In other words, there shouldn't be at present other major known/established facts based on the EAFR readouts (2000+ parameters!), but for now not published, that could immediately lead to other observations/qualifications than those made in the present PR .

If there would be, this would actually mean the end of authority of air safety incident investigation and reporting around the globe as we have known it for the past decades.

You make a fair point, my head supports your position. However my heart says the families of the 229 passengers, 12 crew and 19 on the ground who were killed either through a cruel quirk of fate or deliberate intention over which they had absolutely no control deserve to know which it was at the earliest opportunity. They have suffered enough anguish. Full transparency is essential or mutterings of cover up will soon get louder.