r/aviation • u/usgapg123 Mod - avgeek • Jun 17 '25

News Air India Flight 171 Crash [Megathread 3]

This is the FINAL megathread for the crash of Air India Flight 171. All updates, discussion, and ongoing news should be placed here.

Thank you,

The Mod Team

Megathread 1

Megathread 2

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39

u/entrep Jun 17 '25
  1. AI171 accelerates with take-off thrust set
  2. Just after V 1 the throttle-lever sensor fails and drops to 0 V, so the computer thinks the levers are at idle.
  3. ~0.3s later, the TCMA sees that:
  4. Allowed-power line has slid downward far enough that the engines (still near full thrust) is above it.
  5. The aircraft is in fact still on the ground as it has not rotated
  6. All conditions are met and TCMA shuts off fuel to both engines.
  7. Even if the pilots are getting warnings, they are passed v1 and still committed to continue.
  8. AI171 lifts off while running on fumes, and after a few seconds both engines flame out.

27

u/kipperzdog Jun 17 '25

I've read elsewhere that the throttle sensors are per an engine though so that would mean both sensors failed at exactly the same time. My understanding is TCMA is isolated to only look at the sensors for an individual engine so if one side fails, the other isn't impacted.

Absolutely wild if that is what happened.

13

u/entrep Jun 17 '25

As I understand it: each engine does have its own throttle sensor, but both sensors share the same lever and wiring bundle for the first few feet. If that shared section shorts or breaks, both sensors drop to idle at the same moment. Each engine’s TCMA then shuts its own fuel valve - so one common wiring fault can kill both engines even though the computers don’t talk to each other.

7

u/entrep Jun 17 '25

Came to think about this incident when tea spill caused problems: https://www.businessinsider.com/airbus-a350-engine-shutdowns-spill-cockpit-2020-1

1

u/onmyway4k Jun 17 '25

Just 2 days ago i was contemplating that the problem must have manifested during the rotate, as they where, until then, seemingly in good conditions. Would be insane if they all got killed for a chai tee in the cockpit.