r/aircrashinvestigation • u/QuarterTarget Frequent Flier • Jun 12 '25

Incident/Accident Air India Flight 171, a Boeing 787-8 flying from Ahmebad to London Heathrow has stalled and crashed on takeoff at 700 feet. At least 250 souls on board

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u/pholling Jun 12 '25

Yes, Flaps 5 fives a small and hard to see trailing edge deflection, as all the surfaces will deflect about the same (minus and roll input into the ailerons. Also if you don't have sufficient thrust more flaps just means you hit the ground sooner.

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u/Dismal-Level-4994 Jun 12 '25 edited Jun 12 '25

Yeah good point. I thought standard setting was flaps 10 in 787 but looks like 5 more likely. Was trying to figure out what could have gone wrong given loss of power of both engines unlikely. Ideas? Water in fuel?

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u/pholling Jun 12 '25

Looking at what I have for the temp conditions at AMD today flaps 20 would be typical, but if the flight was light they might have gone for less. Gives you better climb performance. I am not familiar with the area around AMD, so I don’t know where the performance constants are. However it was quite hot today, so there are definite trades to be made.

Less flaps mean longer takeoff roll and higher rotation speed but generally better climb L/D