Posts about: "FlightRadar24" [Posts: 88 Pages: 5]

The FR24 track is extremely limited , but it appears to show the aircraft not backtracking to use the full length of runway 23. If correct, it attempted to take off with only 1,800 metres (\xb16,000 feet) of runway.

Ground tracking on FR24 is often not accurate, taxing aircraft can often disappear and the software simply joins the dots when they turn up again.

FR24 coverage (and any other ADS-B system) is poor at VAAH. Attached a 24h coverage plot. You'll note that the backtrack section of the runway has practically nil coverage, so they may well have backtracked but it didn't show up on ADS-B.

Don't rely on the FR24 trace. A look at the last few AI171 departures off 23 all show the same - no use of full length - strongly suggesting that that is an FR24 artefact.

BBC reckons
The last signal was received seconds after take-off, according to Flightradar24, when the plane was at 625 feet (airport altitude is about 200 feet).

Needs to be corrected for a QNH of 997; so barely a few hundred feet AAL.

Airfield elevation 190 feet
Max barometric ALT on FR24 625 feet ( probably unreliable). Is that where media are getting information?

According to FR24 on bluesky, the aircraft used the full runway length:

"We are continuing to process data from receiver sources individually. Additional processing confirms #AI171 departed using the full length of Runway 23 at Ahmedabad. RWY 23 is 11,499 feet long. The aircraft backtracked to the end of the runway before beginning its take off roll."

QNH, 1001, right?

12hPa = 324 feet overstated altitude.
Airport 189 feet.
Sum = Should show 513feet on ground so 500 or 525 from the ADS-B.

Max altitude shown = 650 feet.

FR24 Shows zero on ground but adopts to ADS-B atitude after takeoff.

I am not familiar with the 787, but to achieve only a few hundred feet from an 11500 feet runway does not sound good. Even an engine fail at V1 should give you screen height at the end of the TODA, followed by a further rate of climb, but that would require the gear to be up.

I'm glad FR24 clarified that. FR24 isn't always accurate. Only yesterday I was on a flight out of Milan. For fun I followed it on FR24 with my sons. At first it was normal but soon we taxyed across the main road and into the forest before returning to the taxyway and taking off from it. Clearly it can't be trusted.
So it should not be relied on.

Possible timeline (all timing after brake-release)

Rotation +33s
Mayday call +44s, circa 300 ft altitude (ADS-B)
Peak altitude +49s, 625 ft (Flightradar24)
Impact +58s, crash site 1.6 km from runway

FR24 update rate is poor - 4 min between the datapoint at the hold and the aircraft being in the air. Plenty of time to backtrack for a full length departure.

I think people on the ground have confirmed that the plane took off from the end of the runway, not the middle. So this is likely FR24 incorrect data.

Air India is not allowed to use intersection departure by their SOP. I think that should clear any doubts on this theory.

No, the FR24 ADS-B data is accurate.

It's the conclusions that people have jumped to while ignoring the fact that there's a 4\xbd minute gap in the data that have turned out to be incorrect.

And the way FR24 presents that data.

Would not be the first time that an accident has uncovered unintended consequences of a particular fallback configuration that was never able to be checked by either/any of Airbus, McDD or Boeing developmental test-pilots. Thinking of the automatic thrust augment/restoration on the MD81 (regn OY-KHO) that crashed 27Dec91 near Gottrora in Sweden (double engine failure). Design Boffins failed to realize that ice-sheet ingestion (sliding off the wings to be ingested by both rear-mount engines) would not benefit at all from each engine hiccup causing a continual uprating of the other (and vice-versa). To be found/uncovered in a simulator you would have to be testing various pilot inadvertencies (rather than rote expected actions). Then again, don't always believe the outcomes to be seen in a simulator. They don't necessarily faithfully emulate what would happen systems-wise in an aircraft... particularly when it comes to complex materiel failure modes or illogical sequiturs (e.g. MCAS)

So, if such an untestable circumstance were to happen to a competent crew and they were to inadvertently shut-down the wrong engine (and then/were in "clean-up mode":

a. The residual hyds would break the downlocks - but not retract the gear (and it would appear to be still selected down)
b. The alternate flaps might start to retract (gear downlocks not being now "made") once selected, but the slats remain out.
c. the RAT would deploy

The point at which all thrust ceases (and the climb vector flattens/reverses) is easily seen
in the video shot from the 6:30 clock position from about a km away. It's readily apparent.

An engine failure just off the runway after V1 in a fully loaded 787-8 in high ambient temperatures would assuredly have a crew thinking about a "toute suite" shutdown of a misbehaving donk. That's human nature. When the PERF is quite sluggish you will be thinking that a quick clean-up of the situation is certainly called for. That's just human nature unfortunately, particularly when you are under the time compression of dire circumstance (and the airframe is performing like a lame dog, just due to the environmentals and the early failure). I think that what the pilot reportedly said to ATC in his Mayday bears that out as being his instant mindset (quite clearly). Been in that "fools rush in" circ myself. You just have to "sit on your hands" and fly the beast.
But then again, if the RAT was NOT found deployed, then it's a case of the right seat mistakenly sucking in the flaps and slats... and that will do it... whatever the power/TOGA might be.
https://tinyurl.com/4zzkeeud
Rotation +33s
Mayday call +44s, circa 300 ft altitude (ADS-B)
Peak altitude +49s, 625 ft (Flightradar24)
Impact +58s, crash site 1.6 km from runway

184kts - 21'AGL
179kts - 46'AGL
177kts - 46'AGL
177kts - 71'AGL
174kts - 71'AGL
172kts - 71'AGL

I can't post the image of the FR24 data, but the granular data points show a 14kt loss of speed from 21' to 71'. With all engines operating, or even with one engine failed, the speed would be increasing or at least remain constant through this period.

Additionally, the CCTV footage from beside the runway shows a ballistic flight trajectory from liftoff to impact.

184kts is a very high rotate speed (a common OPT output) and the aircraft has a lot of excess energy at that point. With Flaps 5 and no thrust it could trade airspeed for altitude at approx 14kts per 50' until about 250'AGL before running out of puff.

Again, that is consistent with the video.

It looks to me like it lost all thrust at some point in the rotation.

There isn't enough clarity on numerous issues, and without answers to the following, zero conclusions can be made as to a possible cause. This is definitely one that could go in numerous directions. Anyone claiming to have the definitive answers must have the FDR data, and I'm assuming that shouldn't take too long to be located and analysed.

1a. Were flaps deployed at start of take off roll?
1b. Were flaps retracted coinciding with climb rate reduction?
2. Did the RAT definitely deploy? The videos are grainy low quality. AI improvement surely isn't reliable.
3. If the RAT deployed, would that indicate complete power loss?
4. Was there any other audio indicating thrust loss or variations during departure?
5. Can we confirm the pilot Mayday indicating thrust loss? If so, that needs investigation as a first priority. The pilot was telling us the cause. Unless we have alternative information he should be believed.
6. Why was the gear not retracted? Distraction, hydraulic failure, flap instead of gear, intentionally, the possibilities are endless.
7. If complete thrust loss occurred, other than a severe fuel issue, what could cause simultaneous flameout? That would be almost unimaginable, yet this is what the pilot allergy said happened. It would have massive ramifications if that gets confirmed.

I don't think the video clips we have are clear enough to say anything at all at this stage. Flaps are hard to see on 787 imo for departure settings. All I can say is it appeared to climb well in the first seconds, then coinciding with the point that gear would usually be retracted, lift appears to very quickly be lost. That indicates sudden speed loss, or lift loss. Speed loss would be thrust, lift loss would be flap retraction if thrust was still available.

The pilot allegedly reported thrust loss, that should be highest on the list of causes imo. In the case of double engine failure without any apparent outside influence visible on videos, that would be quite something for investigators to fathom.

I don't know if anyone has data to show speed trend at the point the aircraft starts to descend, or a better audio for thrust variations at that point. I'm guessing that the update frequency on FR24 would be too slow to show that sudden change at the highest point achieved.

We'll have the answers soon enough, all I can say is there appears to be no clear answers here without the data recorders or clear improved information. Indeed no conclusions whatsoever can be made as to crew actions either.

RIP crew and passengers, condolences to the families.