Science of flying; how heat, humidity pose challenges

The moments after Air India flight 171 took off from Ahmedabad airport at 40 seconds past 1.38 pm were routine for any flight: A massive Boeing 787 Dreamliner barrels down runway 05/23, its nose pointed skyward in the classic climbing posture.

- Binayak Dasgupta

NEW DELHI: Soon, its nosewheels raise off the ground, followed by the pair of heavier rear landing gears; the hulking wide body jet now aloft by the physics of aerodynamics.

But soon, that starts to change: instead of gaining altitude, it begins sinking. For 33 seconds, the aircraft maintains this contradictory orientation—nose up, yet sinking—before disappearing behind trees and erupting into flames.

This haunting video captures a fundamental breakdown in the physics that governs all flight: the delicate equilibrium of forces—of thrust, that propels the jet forward to overcome drag so that the giant wings generate lift enough to overcome weight.

The root cause for this breakdown is now the subject of a multi-agency, multi-country investigation led by India's Aircraft Accident Investigation Bureau (AAIB), with Air India, plane-maker Boeing and engine manufacturer GE Aerospace helping uncover technical clues, with help from air crash investigators from UK and US.

Experts analyzing the video—now crucial to the investigation—were struck by how the plane was doomed at a flight stage governed by simple laws of physics, as opposed to being done in by a more dramatic outcome, such as being knocked off its path by a strong gust of wind or incurring what is known as a tail strike when takeoff is too aggressive.

Understanding these forces is crucial as investigators determine whether engine failure, incorrect wing configuration, miscalculation of weights, environmental factors—or, in fact, a combination of any of these played a role.