Posts about: "AI171" [Posts: 73 Pages: 4]

Reported to be AI171 - LGW Bound

this one here

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.

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."

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.

"On 12th June, 2025, Air India B787 Aircraft VT-ANB, while operating flight AI-171 from Ahmedabad to Gatwick, crashed immediately after takeoff from Ahmedabad. There were 242 people on board the aircraft, consisting of 2 pilots and 10 cabin crew," said a senior DGCA official.

The aircraft was under the command of Captain Sumeet Sabharwal with First Officer Clive Kundar. Captain Sumeet Sabharwal is an LTC with 8200 hours of experience. The copilot had 1100 hours of flying experience, the official further added. The officers gave a mayday call to ATC minutes after taking off. However, they didn't respond to ATC's reply.

I have read around 90% of this thread, and I have a few questions, after using the Search function.

Is a METAR available ? Ahmedabad has been experiencing exceptional heat for the last few days.

What type preceded AI171 on the runway ? How much separation was there ? Is there any possibility of an unusual Wake Turbulence effect in very hot, still wind, conditions ?

Is there Any genuine evidence of Bird impact ? I didn't see any Smoke from either engine.

Plane crash near Ahmedabad.. for the Metar

Much conjecture about flaps. I grabbed this image from one of the widely-circulating videos. Looks clear to me that LE slats are extended and at least 5 probably 15 on flaps.

AI171

Could that be deflected ailerons and not flaps? ( not familiar with 787 wing)

There has been much discussion here about RAT deployment. Various claims either way have been made, based on individual perspectives of available video and audio.

I am very mindful of just how awful a tragedy this is, and have significant misgivings about disproportionate interest in others misfortune where it carries no purpose, but also recognise that for some people knowing and learning what happened ASAP could be very important, particularly given the present circumstances.

Thus while I sincerely hope that early detail from investigators will give some clarity, in an effort to reduce needless speculation regarding RAT deployment I have taken:

(1) an audio sample from the video of AI171 passing by in which people claim to hear a RAT
(2) an audio sample from a 787 video with RAT deployed on test by Boeing
(3) an audio sample from a JAL 787 video with RAT deployed

And passed these through a FFT in order to gain a more quantitative view of the noise spectra from each event.

A spectrogram of the results is presented below. I hesitate to make any conclusions per se, but observe that there are similarities as well as divergences between them. In all three samples there is a relatively consistent signal roughly centered in the range 113-146Hz that could be what gives the characteristic 'buzz' sound of (apparently) a RAT in operation.

JAL ~141Hz
Test ~146Hz
AI171 ~113-134Hz (prob doppler variation here)


Spectral comparison AI171, B787 with RAT, JAL 787 with RAT



Spectral comparison #2 AI171, B787 with RAT, JAL 787 with RAT


These frequencies seem consistent(ish) with what I got from this video [[url]https://www.youtube.com/watch?v=O1r3CuRwjPc] in which a 787 RAT is being tested - albeit in this case the blades are hydraulically powered and not driven as a turbine. This test showed a fundamental frequency of 135Hz with relevant harmonics above (the second harmonic at 270Hz is higher SPL, no weighting):




It's important to note that the initial recordings are necessarily different; these are not controlled conditions, the recording equipment is probably quite diverse and almost certainly not ideal, and the environmental conditions will also be different. Moreover all of these audio samples have come from video files referenced here, one has no way of determining the provenance or veracity of these sources and, crucially, I have no prior experience of analysing/extracting RAT acoustic fingerprints (nor have I sampled 'control' audio of a 787 passing by /without/ RAT!).

Additionally it's been quite a long time since I did any work with [turbine] noise so given these and other variables I'm not prepared to make any declarations per se, but perhaps more knowledgeable people could. That said, my feeling from what I see is that RAT deployment is not dis proven, and that the apparent fundamental frequency difference between the samples may be explainable by - amongst other things - difference in a/c airspeed, bearing in mind that AI171 was on TO, the others were landing.

Ultimately what I've done here is extremely rudimentary and while it would be possible to go into much more depth I'd hope that more definitive answer would be forthcoming by then, however if anyone wants to discuss specific methodology etc off-line please PM, no wish to add to noise on this thread.

FP.

AAIB (UK) Update: Air India flight AI171

People really need to stop using FR24 data if they don't understand it.
This FR24 recording of AI171
https://www.flightradar24.com/data/f.../ai171#3ac3097
only consists of 4 unique ADS-B data messages. The first two were on the apron/taxiway. Then one at the runway intersection. And the fourth and last one just after the aircraft became airborne. That's all.

The two last ADS-B data messages are more than 4 minutes apart. It was 8:04 UTC when they entered the runway at the intersection. The next and last data point was received at 8:08 UTC.

The map view connects these dots, so it looks like a proper track. But in reality the ADS-B receiver barely received anything. It's therefore silly to argue the aircraft stopped transmitting ADS-B data based on this poor recording. The only thing you can say with certainty is that FR24's ADS-B receiver at Ahmedabad has really, really poor coverage...

There are more data messages than that, which FR24 shared on the day of the accident and which have been posted a few times in this thread. I'm pretty sure there's also been a comparison of this + previous flights posted in this thread that shows that while the coverage at the airport itself is spotty, it's reasonable to expect further messages to have been received before impact.

Not sure how permanent the content at this URL is, but here's a link to FR24's update which has a CSV with all frames received https://www.flightradar24.com/blog/f...rom-ahmedabad/

Somebody on this forum did some analysis with FR24 data of this flight and other AI171 B787 flights.
See this article for an overview of all scenarios. It all looks very like to an commanded dual engine shutdown. Why nobody knows.

The comments that you are criticising are based on a subsequent release of ADS-B data from FR24 containing 113 unique messages.

While those still have the 4\xbd minute gap while the aircraft was presumably backtracking, they resume during the latter part of the takeoff roll where reception is clearly better.

There is little doubt that when they abruptly cease after the aircraft is airborne it's because the plane has stopped transmitting.

Flightradar24 published the CSV with all received data. It had EIGHT datapoints of the aircraft after its rotation showing its altitude. https://www.flightradar24.com/blog/f...rom-ahmedabad/

TCMA independently monitors each engine and automatically reduces engine power when it detects the failure of an aircraft engine to throttle down when idle or low thrust is selected. TCMA will only cut fuel to an engine if the aircraft is on the ground and it detects an anomaly between the high power condition of the aircraft's engine when the thrust levers are set for idle or low thrust. There is no evidence in the video of the takeoff roll for AI171 to indicate that its thrust levers were set at idle or low thrust.

A Qantas 747-438 suffered an 'Electrical System Event' when on approach to Bangkok airport on 7 January 2008. The following extracts are taken from the report:

"System malfunctions

Between 0846 and 0852, 4 after passing FL 100 and when the aircraft was turning
onto an extended left downwind leg for runway 01 Right (01R), the EICAS, flight
displays and automated systems showed faults of numerous electrical and other
aircraft systems, including:
\x95 AC buses 1, 2 and 3 not powered
\x95 autothrottle disconnected
\x95 autopilot disengaged
\x95 some fuel pumps not operating
\x95 weather radar not operating
\x95 automatic cabin air conditioning and pressurisation system not operating
\x95 right (FO\x92s) displays blanked
\x95 between three and five pages of messages on the EICAS display
\x95 lower EICAS display blanked.
The CSM contacted the flight crew and advised that the cabin lighting had failed."

"Origin of Generator Control Unit (GCU) faults

Post-incident examination of the GCUs revealed corrosion of the internal circuit
boards in all three of the GCUs that shut down. Analysis of the corrosion materials
observed in GCU 3 showed evidence of long-term exposure to water, including
evidence of acids and carbohydrates that are present in beverages such as coffee,
fruit juice and soft drinks. Those findings indicated a fluid source originating from
the aircraft\x92s galley drains or from spilt liquids in the cabin, and also suggested that
liquid ingress had been occurring over an unknown, but extended period of time."

https://www.atsb.gov.au/sites/defaul.../ao2008003.pdf

This link to the report includes diagrams of where the 747 forward galley was located, directly above the Main Equipment Centre and the E1/E2 racks.

The phtographs show how ineffective the dripshield was in protecting the electrical equipment and the extent of corrosion and damage.

The aircraft was 17 years old at the time of the incident and had completed a C-check approximately three months before the incident.

As FDR notes, this issue seems to have carried over to the 787-8 with Airworthiness Directive AD 2016-14-04 ( https://drs.faa.gov/browse/excelExte...A0058AF6B.0001 )

"We are issuing this AD 2016-14-04 to prevent a water leak
from an improperly installed potable water system coupling, or main cabin water source, which could
cause the equipment in the EE bays to become wet, resulting in an electrical short and potential loss
of system functions essential for safe flight"

AD 2016-14-04 mirrors precisely what occurred to the Qantas 747 on 7 January 2008. It is possible something similar may have occurred on take-off of AI171, with water causing the equipment in the EE bays to become wet resulting in electrical short and potential loss of system functions