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

Musician
2025-06-17T09:56:00
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Post: 11904155
Bird strike ruled out

Originally Posted by OldnGrounded
It seems pretty unlikely that a bird strike that took out both of those very big engines simultaneously would not have been fairly obvious in ways that nearby observers (e.g., the crew, ATC, airport personnel?) would have noticed. Possible, of course, but I don't think we've seen any evidence that points in that direction.
Agreed.
Also, I expect the airport would've sent a car out to check the runway for evidence. Since we agree that the engine failure occurred near rotation, and that rotation occured well inside the runway ( see e.g. fdr here , or the granular ADS-B data), that car would've encountered a bloody mess, and we'd all know about it by now.

Also, for what it's worth, the Times of London June 15 story " New clues point to engine failure for cause of Air India plane crash " cited here in the closed thread includes this:
The Indian authorities indicated that a bird strike has been ruled out.
A poster in the closed thread pointed out, properly I think, that the Times shouldn't be relied upon for presentation or interpretation of technical information. Like most general news organizations, their reporters and editors (mostly) just don't have the background to assess, filter and explain complex processes and technology. Unlike many, though, the Times can generally be relied upon to seek appropriate sources and report accurately what those sources say. I think it's very likely that Indian authorities have ruled out a bird strike, and I also think those authorities are competent to make that decision.
The problem with these reports is that the Indian AAIB and DGCA websites ( aaib.gov.in www.dgca.gov.in ) are mute on the subject of this crash, so even the DGCA inspection mandate quoted above is shakily sourced. On Friday, AvHerald had already updated with "On Jun 13th 2025 the DGCA reported, that initial preliminary findings rule out a bird strike as no bird carcasses have been found." I searched for a source for this, and found an "exclusive" which read, "The initial probe report of the Ahmedabad Air India crash, accessed by CNN-News18, reveals key findings from the Directorate General of Civil Aviation\x92s assessment led by the director of security." Other media simply quoted News18. There are two reasons to be skeptical here:
\x95 first, we have seen fake reports circulating;
\x95 secondly, News18 rates badly on mediabiasfactcheck.com: "Launched in 2005, CNN-News18 (formerly CNN-IBN) is an English-language Indian news television channel based in India. We also rate them Questionable based on a poor fact-checking record with numerous false claims."
That leads me to consider that this "exclusive" might be sloppy reporting based on a fake\x97I have no way to know whether it is legitimate or not.

At this point, I feel we can only rely on information being official if it's published through an official website, or if there's independent reporting or a video clip from an official press briefing.

I do believe the accident was not caused by an animal strike, for many reasons.
But I wouldn't believe it based on unsourced reporting alone.

Subjects: AAIB (All)  AAIB (IDGA)  ADSB  Bird Strike  DGCA  Dual Engine Failure  Engine Failure (All)

4 users liked this post.

Musician
2025-06-17T10:08:00
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Post: 11904163
Fuel temperature

Originally Posted by FlightsofFancy
you mention temperature - got me thinking. Not a pilot (yet) but I am an engineer. A packed 787 sitting out on the tarmac engines running for 3 hours in 41 degree heat with no AC - filled with potentially very warm fuel - what\x92s the chances the fuel could heat up to 49 degrees? Celsius not Fahrenheit. Just wondered what the chances were that it was vapour lock in the fuel lines?
The AC does not cool the fuel tanks.

Quoting MR8, 15th Jun 2025 21:54 from the other thread:
With an ambient temperature of 42 to 46 deg C, it is doubtful if any GA aircraft could fly from this airfield, as AvGas suffers from Vapour Lock at 38 deg C.

Jet-A is not so easily affected, but I hope the temperature of the loaded fuel was recorded when uplifted.
Fuel temperature is not the issue. Max Fuel temperature on our Airbus is 53˚C, the B787 will have a similar limitation. Summer in the Middle East is hotter than this without any issue.

Subjects: None

3 users liked this post.

Musician
2025-06-17T10:51:00
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Post: 11904195
Enhanced Airborne Flight Recorder (EAFR)

Originally Posted by Squawk7700
How could the CVR have been "read out" if the CVR hasn't yet been located?
The flight recorder on the 787 is called "enhanced airborne flight recorder" (EAFR), and it's a combination unit with CVR and FDR functionality. There are two on the aircraft, the one in the front has battery backup.
Since it has been reported that the "FDR" was found, they also have the "CVR".

Subjects: CVR  DFDR  EAFR  FDR

6 users liked this post.

Musician
2025-06-17T19:23:00
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Post: 11904582
Originally Posted by 604driver
A query I have is, do later Gen aircraft like the 777/787/747 A330/A350/A380 constantly send Airframe/Engine data home to ops/engineering/oem\x92s. Is it likely the data is out there?
Here's an answer from the other thread: Sailvi767 , 14th Jun 2025 18:00
Engine parameters are generally data linked in bursts. Usually every 30 minutes. If an engine parameter goes out of limits normally an alert will be sent immediately but in this case I doubt the alert would have been sent before the power interruption. The black box will tell the story.

Last edited by Musician; 17th Jun 2025 at 20:54 .

Subjects: Parameters

3 users liked this post.

Musician
2025-06-18T04:34:00
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Post: 11904895
Question climb rate

Originally Posted by EDML
Regarding the momentum: As the first few seconds of the climb were normal compared to previous T/Os of the same flight (speed & altitude, confirmed by comparison of the RAW ADS-B data) I don't believe the engine failure happened before or on lift-off.
Could you please elaborate on that?

FR24 did do that raw ADS-B data comparison. Remember the GPS position and barometric altitude are sent by the aircraft itself. The altitude is sent in 25 ft intervals, so a shallow curve that is smooth in reality looks janky in the data, due to the rounding of the numbers. From https://www.flightradar24.com/blog/f...rom-ahmedabad/ :
We’ve taken data from AI171 departures for the month prior to the accident flight—including two previous operations by VT-ANB—and overlaid their departure paths on the data from AI171 on 12 June. The accident flight is in red, while all other flights are the blue paths. The data shown here is the uncalibrated barometric altitude, so the data is not above ground level, but it is consistent to itself.
The red line is the accident flight, and it covers approximately 4.3 seconds.
Obviously the altitudes are all uncorrected for barometric pressure, which would've varied with the weather on that day; you kind of have to mentally shift the lines vertically downward. Now I looked for, but couldn't find, the post in the old thread where the rotation was triangulated\xb9, but I remember that it was near the turnoff to the high-speed taxiway, so a few seconds ahead of this ADS-B capture. We only have the video to show us what occurred then.

That means the ADS-B data doesn't really tell us whether the first few seconds of the climb were normal or not.

When we compare the red line to the blue lines, the data tells us the climb rate had already decayed significantly before the accident aircraft passed over the end of the runway, because the red flight path is much more shallow than the blue flight paths.

Please correct me if I'm wrong: to my eye, the data alone does not show that the engines must have failed after rotation, because the data does not demonstrate a normal climb rate.

But likewise, the engines can't have failed much before rotation:
Originally Posted by fdr
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.
For completeness' sake: you can look at the CCTV video, consider the 787's wingspan a flying 200 ft yardstick, and hopefully agree that the aircraft did not get much higher than 200 ft AAL, if that.

-----
\xb9 I found one of them, anyway. The reference is the CCTV video:
Originally Posted by dragon6172
You can triangulate the camera location using the aircraft holding short for takeoff and the road sign. Then draw a line from there just to the right of the instrumentation building and you'll find the aircraft rotated with about 4000 feet of runway remaining (11000+ runway length).

Last edited by Musician; 18th Jun 2025 at 17:43 . Reason: footnote 1

Subjects: ADSB  AI171  CCTV  EDML  Engine Failure (All)  Engine Shutdown  FlightRadar24

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Musician
2025-06-19T04:40:00
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Post: 11905712
Air India Radar Altimeters are reported to be 5G-safe

Here's a source to (hopefully) put the 5G speculations to rest:

As 5G telecommunications technology rapidly expands, India's Directorate General of Civil Aviation (DGCA) has issued a directive requiring airlines to upgrade their aircraft's radio altimeters (RAs). This directive avoids potential interference between the new 5G telecommunications technology and the existing aviation equipment.

For example, Air India, a fleet comprising 39 % 787s and 777s, stated that retrofitting an RA is an overnight process that would not disrupt flight schedules. These models in Air India's fleet already possess the new RAs.


Source: https://simpleflying.com/indian-auth...eter-upgrades/ (and others)

Last edited by Musician; 19th Jun 2025 at 04:54 .

Subjects: DGCA

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Musician
2025-06-19T11:21:00
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Post: 11905944
Originally Posted by Europa01
I\x92ve had a look at the Honeywell spec sheet for TL type switches.
How many cycles are they rated for?

Subjects: None

Musician
2025-06-19T13:38:00
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Post: 11906027
Originally Posted by LGB
It is noteworthy that the point that thrust is lost, is very close to 400' AGL,
No, it's not. You got that value from ADS-B, which is barometric altitude at standard pressure, and when you correct for that, the highest value is ~100 ft. AAL.

Instead, look at the CCTV video, and consider that the wing span of the aircraft is ~200 ft. I hope you'll agree AI171 didn't come close to 400 ft. AAL at any point.

Last edited by Musician; 19th Jun 2025 at 13:53 .

Subjects: ADSB  AI171  CCTV

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Musician
2025-06-19T16:03:00
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Post: 11906148

Draw your own conclusions.
Personally, I trust there were no issues.

Subjects: None

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Musician
2025-06-19T21:50:00
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Post: 11906413
Originally Posted by That lights normal!
Could water and/or chafing in the wiring loom \x93convince\x94 the \x93system\x94 that the AC was on the ground?
Then adjust the thrust accordingly.
You may be surprised to learn that aircraft sometimes need full thrust on the ground.
TCMA requires that the pilot pulls the thrust levers back to idle, and that the engine fails to spool down to idle as commanded. Only then will it shut off the engine (on the ground).
Pilots try to avoid pulling the thrust levers back to idle when they're taking off.
For that reason, TCMA has never triggered during take-off before.

Subjects: TCMA (All)

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Musician
2025-06-20T05:30:00
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Post: 11906603
TCMA things, imagination and evidence

Originally Posted by neila83
You may be surprised to know that TCMA doesn't require that, it just requires a differential between commanded and actual thrust.

It has never triggered during takeoff until now. Maybe it still hasn't been. We'll see. Given there is an actual example of a 787 in the wild shutting down both of it's engines when it shouldn't (ANA), I'm surprised how complacent people are that this couldn't be the cause..Software can always have weird corner failures that could never have been thought of or tested.
Yes. I simplified. The point stands that the throttle needs to be pulled back, as it was in the ANA event, because that was a landing and not a take-off.

Originally Posted by user989
V. Shutdown of engines by TCMA
A parallel is drawn to the ANA incident. However, this would require not only a fault in the air/ground logic but also a sensed discrepancy between T/L position (not necessarily idle) and thrust output on both engines simultaneously.
First, you posted a good summary. I'd have added "unanticipated hardware fault" and "unanticipated software fault" as generic causes.

Note that the thrust lever actuators are wired to the FADECs, and that the TCMA gets the T/L position from that. For TCMA to trigger, it has to determine that its FADEC (on that engine) failed to achieve a commanded reduction in thrust. So we're either looking at a weird, unprecedented edge case, or a FADEC failure, or both.


Originally Posted by Lead Balloon
Just so I have this clear, are you saying that the implementation of the TCMA functionality involved no new components being added to the pre-existing FADEC? Are you saying, in effect, that the two switch relays described in the TCMA patent application, which relays and their configuration achieves the described two channel redundancy, were already there as components or are mere depictions of what the software does itself?
It has been mentioned before that this capability existed as part of the N2 overspeed protection: the FADEC would shut down a runaway engine by cutting its fuel before it disintegrates.
Originally Posted by Lead Balloon
I am not suggesting you are wrong and, as I've said before, the descriptions and schematic in the patent application are just 'big hands / small maps' concepts. However, if TCMA functionality "is simply a bit of software in the FADECs", merely sending a 1 or 0 or other signal into a point in the pre-existing FADEC that already had control over fuel cutoff (with the TCMA software merely monitoring data busses, rather than direct sensor outputs, to work out thrust lever position and whether or not the aircraft is 'on the ground' for TCMA purposes) I for one would really like to know that for sure and get my head around the implications.
The thrust lever sensors are wired directly to the FADEC (and hence the TCMA). No data bus is involved with this item.

With a MCAS crash, it required a hardware problem with an AOA sensor, used as input to a correctly working MCAS, to cause the aircraft to behave erratically. With a correctly working TCMA, I believe it'd require two hardware problems to get TCMA to shut down the engine, as there'd have to be an implausible thrust lever reading, and a FADEC/engine failure to process it within the TCMA allowed range ("contour"?). On both engines, separately and simultaneously.

That leaves a software problem; it's not hard to imagine. The issue is, at this point it's just that: imagination. I could detail a possible software failure chain, but without examining the actual code, it's impossible to verify. We simply don't have the evidence.
I could just as well imagine a microwave gun frying the electronics on both engines. An escaped hamster under the floor peeing on important contacts. A timed device installed by a psychopathic mechanic. There's no evidence for that, either.

This process is a way to psychologically cope with the unexplained accident, but because it lacks evidence, it's not likely to identify the actual cause. We've run the evidence down to "most likely both engines failed or shut off close to rotation, and the cause for that is inside the aircraft". Since the take-off looked normal until that failure, we have no clues as to the cause hidden inside the aircraft. We need to rely on the official investigation to discover and analyse sufficient evidence. The post-crash fire is going to make that difficult.

"Both engines failed or shut off close to rotation" explains all of the evidence : it explains an unremarkable take-off roll, loss of lift, absence of pronounced yaw, loss of electrical power, loss of the ADS-B transponder, RAT deployment, the noise of the RAT banging into place and revving up, emergency signs lighting up, a possible mayday call reporting loss of thrust/power/lift, and a physically plausible glide from a little over 200 ft AAL to the crash site 50 feet (?) below aerodrome elevation .
It explains what we saw on the videos, what the witness reported, where the aircraft ended up, and the ensuing sudden catastrophe.

I don't believe we have evidence for anything else right now—I'd be happily corrected on that.

-----
Edit: the evidence of the crash photo with the open APU inlet door, and the main gear bogeys tilted forward, are also explained by the dual engine failure/shut off.

Last edited by Musician; 21st Jun 2025 at 06:48 . Reason: more evidence

Subjects: ADSB  APU  Dual Engine Failure  Engine Failure (All)  Engine Shutdown  FADEC  Fuel (All)  Fuel Cutoff  Mayday  RAT (All)  RAT (Deployment)  TCMA (Air-ground Logic)  TCMA (All)  TCMA (Shutdown)  Takeoff Roll

17 users liked this post.

Musician
2025-06-20T09:15:00
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Post: 11906759
EAFR documentation

Originally Posted by xetroV
Do both EAFRs run on emergency power? Could it be possible that only ONE (if any) EAFR unit was recording after the supposed loss of thrust on both engines? If the other one is severely damaged we might as well end up with NO EAFR data from the critical last part of the flight. Perhaps both units are severely damaged? I\x92m not convinced your optimism is entirely warranted.
Both EAFR run on standby power, yes. In addition, the forward EAFR has its own battery backup. However, the number of devices that still send valid data to the EAFR during a power outage is diminished, of course.

The black rubber cap protects a multi-pin connector.

The white cylinder is an underwater location transmitter.

The forward EAFR has its own backup power.

Source: https://www.geaerospace.com/sites/de...rder-3254F.pdf

Subjects: EAFR

7 users liked this post.

Musician
2025-06-20T09:25:00
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Post: 11906769
Originally Posted by Capn Bloggs
The bleeding obvious didn't work on the Jeju Air 737.

The 787s recorder/s have obviously been damaged so much/missing data they are being taken to the US.
The Jeju Air recorders survived the crash, and their data was successfully downloaded. They simply stopped recording when the power failed. (And those recorders were also much damaged.)

Here, at least one EAFR has its own power source, and we're likely to see a record of the engine failures if those caused the power loss on AI171, so that's going to be more helpful.

Subjects: AI171  EAFR

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Musician
2025-06-20T09:51:00
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Post: 11906786
Originally Posted by MaybeItIs
Isn't "close to rotation" a little broad? "Close to" can be before or after. If before, and with about 4,000 feet of runway remaining, why did they take off at all? How did they take off, for that matter?

Can anyone do the Momentum / Energy calculations to work out how high the plane would have travelled at the normal climb gradient purely on the momentum it had at rotation? I'll try, see how far I get. A stone, fired into the air at an upward angle, begins to slow down and curve towards the earth the moment it leaves the catapult. It appears to me that the plane climbed at approximately a steady speed until about the 200 ft mark, so I submit that it had adequate climb thrust up to "about" that point.
It would definitely be nice to narrow that down; I can't do it, and your method is not convincing me.
The ADS-B datagrams sent by the aircraft show a much diminished climb rate with decaying speed, betraying insufficient thrust in that phase of the flight. That somewhat contradicts your assertions.

I also do not have faith in anyone's ability to watch the cctv video and confidently determine through mere eyeballing that the climb rate did not decay by 15% within the first 100 feet or so. (The ADS-B data suggests the speed diminished 7% for ~50 ft of climb.) Other than your stone, even a glider can convert speed to altitude.

So, "close to rotation" is the best I (personally) can do, based on what I know right now; or that I would trust myself to be able to convince others of.

Subjects: ADSB

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Musician
2025-06-20T10:56:00
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Post: 11906831
Originally Posted by soarbum
At that point, the total energy of the system would have comprised of the kinetic energy of the aircraft travelling at Vr, the rotational inertia of the engines and the potential energy of whatever fuel is beyond the cutoff valves.

Q5: Would this total energy have been sufficient to get the aircraft 100ft into the air?
Assume an object travels at 200 knots and its speed decays to 120 knots (100m/s to 60m/s). The kinetic energy lost thereby suffices to elevate that object by ~1000 ft. (320m) in a vacuum, i.e. disregarding drag. In other words, if 75% of the kinetic energy was lost through air resistance (drag), the aircraft could still climb more than 200 feet.

Subjects: Total Energy

Musician
2025-06-20T12:13:00
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Post: 11906909
Flightradar24 and ADS-B

Thank you for your reply! There's a lot we agree on; unfortunately, I'll be cutting that from my response here.
Originally Posted by MaybeItIs
Sure, actual data is usually more accurate than eyeballed stuff. But not always. In fact, it's often the eye that determines that something measured or calculated is "Off". How accurate is ADS-B data? I've seen FR24 tracks go way off course then suddenly get corrected / interpolated, frequently. The erroneous data seems to be "removed" by their algorithm, but where are the errors arising? Why this inaccuracy, and therefore, how accurate are the datagrams referred to? I know there were no datagrams received during the backtrack that I accept actually occurred, but that's completely different from receiving erroneous ADS-B data.
Right. ADS-B is transmitted via radio, so reception can be patchy, or obstructed by someone else transmitting on the same frequency (e.g. other aircraft), so not every datagram that the aircraft sends gets received. When that happens, the live display of FR24 assumes the aircraft kept doing what it did, and when another datagram eventually comes in, it corrects the position. It also connects the locations of these datagrams, regardless of whether the aircraft actually went there. For example, in the AI171 there's a 4-minute gap between a datagram sent on the taxiway, and the next datagram sent when the aircraft was off the ground towards the departure end of the taxiway. FR24 then connected these points via the shortest route; but we know that the aircraft actually used the intervening 4 minutes to taxi to the approach end of the runway, where it then started its take-off run. So that was false. (Another source of errors is when different FR24 receivers don't have synchronised clocks, so a mixture of data from these can have weird artifacts as a result.)
However, the datagrams that FR24 actually received were correct. They contain the GPS position of AI171 and its unadjusted barometric altitude, as determined by its onboard instruments. This data is as reliable as the instruments themselves are. (An example here is that the NTSB wasn't sure that the altimeter on the Blackhawk that crashed at Washington-Reagan was accurate; if that is the case, the ADS-B data would also be affected.)

On their blog post at https://www.flightradar24.com/blog/f...rom-ahmedabad/ , FR24 have published the data that they actually received.

Sure, the CCTV footage I've seen is very poor, a video, moved about and zoomed, of the CCTV screen. Not easy to judge, but still useful and could be analysed frame-by-frame to compensate for all the extraneous input. Anyway, it's obvious to me that the rate of climb dropped abruptly just before the flight attained its apex, as if thrust was suddenly cut off.
Have you ever seen a parabolic trajectory from "the short end"?
Knowing the momentum to altitude conversion, it might be possible to estimate whether that's true or not. The evident RAT deployment supports engine shutdown, not just engines to Idle, doesn't it? In that case, it would be useful to know at what altitude the engine shutdown took place.
Yes.

(The ADS-B data suggests the speed diminished 7% for ~50 ft of climb.)
Okay, didn't know that, I guess suggests means it's uncertain? Can you tell me from what height to what height it suggests this?
It's uncertain because the 787 rounds all altitudes it sends to the nearest multiple of 25. The altitudes sent were from 575 ft to 625 ft., but that's MSL and not adjusted for the weather: low air pressure makes that number higher than the actual altitude. FR24 adjusted this to 21ft climbing to 71 ft, but it could've been 30 to 60 or maybe 10 to 80, as it's rounded. I think it's fairly close to 50 feet of climb, though.

And why all the wrong figures for the height attained, quoted in previous thread? Can't all be the atmospheric conditions.
1) people taking the MSL altitude literally (625 ft)
2) people adjusting for airport elevation (189 ft), but not for pressure: 437 ft
3) people adjusting for pressure, some adjusting for temperature, get 71 to ~100 feet for the last recorded altitude.
But while ADS-B reception was lost then (or the transmitter lost power), the aircraft continued climbing; examine the cctv video, knowing the wingspan is ~200 feet, we see that the aircraft reached 200 feet but not much more.

One fact that alters things substantially is whether the survivor's impression is correct that possibly the engines started to spool up again just before impact.
The survivor likened the sound to a car engine revving up. If you've listened to a good version of the phone video, you'll have noticed the "vroom" sound at the start that some likened to a motorcycle. That sound is the RAT in action, and you can imagine what that would sound like when it rapidly spins up: like a driver stepping on the throttle with their car engine in neutral.
If that's the case then what does that do to the possibility or otherwise that the TMCA system caused a dual engine shutdown?
The RAT deploying is a consequence of a dual engine shutdown. It says nothing about whether the TMCA was involved.

[Now I just hope your post is still there as I post this. ]

Last edited by Musician; 20th Jun 2025 at 12:26 .

Subjects: ADSB  AI171  CCTV  Dual Engine Failure  Engine Failure (All)  Engine Shutdown  FlightRadar24  Fuel (All)  Fuel Cutoff  NTSB  RAT (All)  RAT (Deployment)

3 users liked this post.

Musician
2025-06-20T12:31:00
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Post: 11906925
Originally Posted by Capn Bloggs
In this case, not being a 787 jock, my WAG would be a V2 of 165, so they'd be at ~180, and Vref would be at least ~160 (422,000lb, at flap 5). Once those engines cut, it wasn't going much higher at all. Bit of a zoom of possibly 100ft max, IMO. So I doubt the engines stopped at liftoff.

Having done many a takeoff sitting with the nose pointed skyward after liftoff, you just know that if both engines stopped, you would almost immediately stop going up. When you lose only one you have to be quick getting the nose down to keep the speed. If you lost both, you're not going much higher.
For comparison, the ADS-B data show the ground speed dropping off from 184 knots to 172 knots over 4.3 seconds as the aircraft climbs.

Subjects: ADSB  V2

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Musician
2025-06-20T15:12:00
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Post: 11907045
Parabola

Originally Posted by OPENDOOR
In the CCTV footage the aircraft's flight path appears to be a parabola. If there was any thrust remaining following rotation it would be very different.
How did you determine that the path was parabolic?
By eyeball, did you measure something, did you have something to compare it to?

Subjects: CCTV

Musician
2025-06-20T19:32:00
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Post: 11907237
Originally Posted by hans brinker
Emirates 521 touched down at 162kts, presumably idle power, lifted off 8 seconds later, climbed to 85' and touched down 12 seconds after lift off. My best guess would be at least partial power after T/O for AI to get that high and far.
\x95 The aircraft was a 777 configured for landing (flaps 20 for the G/A attempt)
\x95 The crew pushed TOGA, but it didn't take, because the aircraft had technically landed already. This delayed pushing the throttle forward.
\x95 AI171, starting from 184 knots or more, had substantially more energy to work with.

Subjects: AI171  TOGA

Musician
2025-06-20T19:44:00
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Post: 11907252
electric circuits

Originally Posted by old dawg
To explore the electrical system further see p. 86 of this document. I decided to trace out some electrical paths to equipment and do a few simple calculations.
https://fliphtml5.com/quwam/qhdw/Boo...cs_Electrical/
That's a very useful document, and it answered some questions for me.


The area microphone connects to both EAFRs. The EAFR are normally powered via the left and right main 28v buses.

The RAT powers the backup bus.

The main L and R 28v buses do not receive backup power.

After electric power is lost, the aft EAFR is unpowered, and the front EAFR has 10 minutes power off its internal supply.

Subjects: EAFR  RAT (All)

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