Did A Hydraulic Failure Doom Air India Flight 171?

The Boeing 787, which for 15 years had a stellar accident record, has two types of flaps: forward flaps called leading edge slats, and large flaps on the back of the wing. Flaps change the curvature of the wing, which allows the wing surface more air underneath the wing for lift. Commercial pilots say that if the flaps are not deployed on takeoff the plane will not get airborne, or will not stay airborne once it clears the runway.

There is a photo of a part of the Boeing wing that appears to show the leading edge flap in a deployed position. Whether this was because it had been hydraulically deployed or that it came loose in the crash, isn't known.

There is video of the plane taking off. The video shows the landing gear deployed. It may show the leading edge flaps deployed, although that isn't certain. More definitively, the large rear flaps are not deployed.

What is visible on the video is the landing gear, which is deployed (down). There are two reasons why a landing gear might be down; either the pilot kept them down expecting a crash landing, or the gear was not retracted by the crew.

Typically on takeoff the landing gear retraction process starts just after the plane is airborne. The reason for this is to reduce drag on the aircraft and improve airspeed just when the plane needs as much airspeed as possible.

On takeoff a plane is at maximum power. As it climbs the pilot will reduce engine speed as it climbs to its assigned altitude.

There was a Mayday distress call from the Boeing. We do not know the exact moment the distress call was made.

The fact that the aircraft appeared to need the entire runway for takeoff, and then did not climb very high (around 425 feet) before it started to“sink” in the air, raises many questions, one of which is why the pilots did not abort the takeoff?

There has been talk about a dual engine failure that could have been caused by a bird strike or possibly because of fuel contamination.

There were no reports of birds either above or at the end of the runway, which does not rule out the possibility but makes it appear to be an unlikely explanation. There also is no visible event, an engine on fire or debris coming out of the engine, suggestive of a bird strike.

Some form of contaminated fuel or fuel starvation potentially could have shut down both engines, but mitigating against this possibility is that all other aircraft were operating normally if refueled at the airport. and a fuel issue would have triggered sensors warning the pilots while on the ground.

There are ways a plane's computers regulating fuel flow could be tampered with, but there have been no such incidents reported in commercial aviation. Once when a commercial plane, TWA 800 , crashed, the plane's fuel tank exploded because of a short circuit in the wing area that triggered a fuel explosion.

The plane had recently been through an overhaul, but what was actually done still needs to be explained. In any event, the aircraft was on a turnaround flight from London, so it was obviously airworthy. Both pilots on the Flight AI-171 (that crashed) were experienced. Captain Sumeet Sabharwal, a line training captain with 8,200 hours of flying experience, commanded the flight. The first officer was Clive Kundar, who had accumulated 1,100 hours of flying experience.

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One possibility that has not been discussed but should be explored is whether the pilots deployed the flaps but the flaps never actually deployed. That could mean an electronic or hydraulic failure.

On the video of the dying aircraft it appears that the Ram Air Turbine (RAT) flap was open, suggesting the auxiliary turbine sensed that there was a hydraulic failure and began operating to provide the missing power that would move the landing gear, flaps and other systems needing backup power. Whether the pilots would have known this in the frantic seconds before the crash is uncertain. This is a critical issue.

Aboard the plane are two crash-proof black boxes, as they are called, that are both voice recorders and aircraft data recorders. These are situated in the aft section of the aircraft – and from photos of the crash scene it appears that most of the rear part of the plane survived, leading to a possible early recovery of the black boxes.

Investigators may be able to learn what happened on board AI-171.

Stephen Bryen is a special correspondent to Asia Times and former US deputy undersecretary of defense for policy. This article , which originally appeared on his Substack newsletter Weapons and Strategy , is republished with permission.

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