Posts by user "Musician" [Posts: 35 Total up-votes: 112 Pages: 2]

two different engines with different maintenance histories, affected pretty much simultaneously via a long-term process?
The question is moot because the likelihood of it happening is miniscule.

We've discussed this before; the simplest explanation is that it's dust from the side of the runway swept up by the wake vortex, which strengthens as the wing starts generating lift.
The 787 is very wide, and the wing tips are pretty much at the edge of the paved surface; the vortex would extend beyond.

That's good info on the triangulation!

That's ~950m (3100 ft.) from the threshold, and 2.5 km from the accident site.

I like that we have a picture now, and that Hoover illustrates how he made the determination.

Looking at this diagram, I don't understand why certain media are concerned with fuel filters. Every filter here seems to have a bypass valve which opens if the filter clogs up. What am I missing?

3. The AAIB looked into crew rostering; this is a routine part of air accident investigations (maybe not in India? but they have NTSB and UK AAIB sitting in this time). The AAIB found irregularities; this is a safety issue, so they notified the DGCA. The DGCA would've told Air India, "we can pull your operator license over this, but we won't if you fire those responsible".

It's a speculation, but I'd be surprised if it didn't fit the facts.
Also, we can't draw any conclusions about the accident crew; the discovery could've been incidental, or the accident crew might be affected, but the investigation is ongoing, so that's not public yet. It will be in the report, perhaps in the preliminary report even. (I expect NTSB and UK AAIB insist on a preliminary report, but who knows.)

Not quite.
https://mode-s.org/1090mhz/content/ads-b/1-basics.html :

When the aircraft is on the ground (or on the water), it does not transmit altitude.

VHF L is on emergency power, the EAFR are not ( see Air India Ahmedabad accident 12th June 2025 Part 2 ). The front EAFR has its own battery (RIPS) for that reason, the back EAFR has not. (The number of 787 events where this mattered is zero so far.)
Different (older) aircraft, the flight recorders there did not have backup power iirc.

MCAS wasn't "under the radar". The designers thought:
* all MCAS can do is affect the trim
* if something goes wrong with the trim, the crew works the "runaway trim" checklist
* this cuts MCAS off from the trim
* therefore, MCAS failure of any sort is going to be contained

It just turned out that if a crew is stuck, shortly after takeoff, in an aircraft that wants to go down, and they have no clue why because "AOA disagree" indicators are considered a luxury item for Boeing and Boeing also did not want to train crews for this, the crew may not be in the right mindset to prioritise that checklist.
Today, everyone is aware, so it's no longer an issue.

TCMA was motivated by a similar observation: that crews can fail to shut down an engine that no longer follows command input. So the FAA requires aircraft to detect that condition and do it automatically when on the ground, where an engine running at significant thrust is a danger to people and movable objects in the vicinity. The safety consideration here is, if you're on the ground and the thrust reverser is not deployed, you're not going to need the engine that badly. (I think there are actually two more conditions that I don't remember right now.)

In safety, you kinda need to weigh the consequences of having this system (with a chance that it might malfunction) vs not having it. Also consider that the benefit of having it, all of the occasions where it correctly shuts an engine off, don't get reported in the press.

If a TCMA bug caused this accident, the investigation will find out.
But right now, we don't have any evidence that that's what happened.

I had thought consideration for the preservation of truth might underlie India's reluctance to send the flight recorders across the Pacific Ocean. But it could simply be that the foreign accident boards and India have different opinions on how trustworthy India's flight recorder lab is. Negotiations ensue? Anyway, this is idle speculation on my part.

While impatient media might lament the delay, I think it is right that some time is spent on ensuring that the end result of the investigation is trustworthy. Even if that involves diplomacy.

The EAFR has that functionality. From the GE brochure:

Can you point to a single incident where this would have made a difference?

Quote:

Another debate that should now be had is real time telemetry. Given the number of airlines contracting with Starlink for internet services onboard their fleets uploading the data stream fed to FDR's wouldn't put a dent on the available bandwidth and the search and recovery process for FDR's would be a thing of the past.

You'd still have to search for the CVR, so...

The obstacle is that it's illegal.

A few days ago, I created a "wiki post" at the top of this thread, where I hoped we could collect "must-read" information. If you don't have the requisite 90 days/90 posts to edit it, feel free to PM me with what you'd like to have added.
https://www.pprune.org/recentforumwikiposts.php

Searching the web, I found out that regulations concerning new FDR require parameter 35g "fuel cut-off lever position" to be recorded. I also found that for a 2003 event with a 757, this was recorded (as was fuel flow).

I expect that this is also true for the 787. Can anyone confirm this?

Two points:

1) I had seen the "50 feet below runway" referenced as well, and double-checked on Google Earth, and could not confirm this. The terrain looks reasonably level. I'd be happy to see evidence for this claim, but until I do, I'll think it's false.

2) The maximum L/D is given for optimal speed, which remains constant throughout the glide. In the AI171 case, drag is balanced not just by loss of altitude (as it is in the optimal glide), but also by loss of speed. The speed decline provides energy, and I suspect that makes up the shortfall you assign to thrust.

Note that kinetic energy is proportional to v\xb2, i.e. a speed loss of 50 knots from 180 to 130 vs 50 to 0 provides 15500 vs 2500 units of energy, i.e. 6 times as much. If you hypothetically hurl a unpowered aircraft into the sky with a catapult (and if there was no drag), hurling it at 180 knots makes it go 6 times as high by the time its speed decays to 130 knots than it could ever go if you hurled it at 50 knots. Of course there's drag in reality, and that also varies with v\xb2, so this is a very theoretical consideration intended to calibrate your expectations.

I remember that someone used some kind of tool to confirm that the aircraft could've gone unpowered for as long as we assume it did, but of course I can't find it again now. :-(