Was the Air India crash caused by pilot error or technical fault? None of the theories holds up ... yet

Over the weekend, the Indian Aircraft Accident Investigation Bureau released a preliminary report on last month's crash of Air India flight 171, which killed 260 people, 19 of them on the ground.

- BY GUIDO CARIM JUNIOR Senior Lecturer in Aviation, Griffith University

The aim of a preliminary report is to present factual information gathered so far and to inform further lines of inquiry. However, the 15-page document has also led to unfounded speculation and theories that are currently not supported by the evidence.

Here’s what the report actually says, why we don’t yet know what caused the crash, and why it’s important not to speculate.

What the preliminary report does say

What we know for certain is that the aircraft lost power in both engines just after takeoff.

According to the report, this is supported by video footage showing the deployment of the ram air turbine (RAT), and the examination of the air inlet door of the auxiliary power unit (APU).

The RAT is deployed when both engines fail, all hydraulic systems are lost, or there is a total electrical power loss. The APU air inlet door opens when the system attempts to start automatically due to dual engine failure.

The preliminary investigation suggests both engines shut down because the fuel flow stopped. Attention has now shifted to the fuel control switches, located on the throttle lever panel between the pilots.