Air India Ahmedabad crash probe: 5 things to know from the preliminary report | Mint

A month after the horrific crash of an Air India Dreamliner at Ahmedabad, the AAIB (Aircraft Accident Investigation Bureau) has released its preliminary report to the public. While analysts have been vocal about the preliminary report, the report only dwells over the fact and in most cases does not point to the WHY and HOW of the crash, rather looking at WHAT. The rest is part of the investigation which takes longer.

The Annex 13 of Chicago Convention, to which India is a signatory, mandates that states in charge of an investigation must submit a preliminary report to ICAO (International Civil Aviation Organisation) within thirty days of the date of the accident. Preliminary reports can be marked confidential and it depends on the investigation state’s discretion if they should be made public. ICAO also mandates that the final report should be made publicly available as soon as possible and if possible within twelve months.

However, these are advisories and not rules. Recently China is reported to have refused making the crash report of China Eastern flight MU5735 public citing (it could) “endanger national security and societal stability”.

The last two crashes in India have been the Air India Express crash at Kozhikode on 7 August 2020, with the final report submitted on 13th January 2021 and the Mangalore crash on 22 May 2010, when the final report came out in November that year. These two crashes were in the landing phase, while the Air India crash at Ahmedabad was within seconds of lifting off from the runway.

The preliminary report throws light on these five things

Last words

There has been quite a lot of speculation on what were the last words from the pilots of the AI171, with various sources being cited by each one. Turns out the last words were only “Mayday, Mayday” and the pilots did not speak about loss of power or anything else.

No previous issues

The aircraft which crashed, VT-ANB did not have any critical items under MEL or Minimum Equipment List. The entire MEL list was within the timeline limits. In aircraft, a Minimum Equipment List (MEL) is a document that outlines the minimum equipment required for an aircraft to legally operate with certain inoperative systems or components.

It allows for safe operation even when some equipment is not fully functional, provided specific conditions are met and the aircraft complies with the MEL’s limitations.

The MEL is specific to an aircraft type and operator and is derived from a Master Minimum Equipment List (MMEL) provided by the aircraft manufacturer.

Both engines were starved of fuel

Immediately after take off, AI 171’s Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF, one after another. In the cockpit voice recording, one of the pilots is heard asking the other why he cut off. The other pilot responded that he did not do so.

Reignition tried

The AAIB preliminary report mentions how the fuel cutoff switches again transitioned from CUTOFF to RUN with efforts made to relight the engine, one after another.

As per the EAFR (Enhanced Airborne Flight Recorder), the Engine 1 fuel cutoff switch transitioned from CUTOFF to RUN within seconds of pilots talking about cut-off.

The APU Inlet Door began opening thereafter, consistent with the APU Auto Start logic. Thereafter the Engine 2 fuel cutoff switch also transitions from CUTOFF to RUN.

When fuel control switches are moved from CUTOFF to RUN while the aircraft is inflight, each engine’s full authority dual engine control (FADEC) automatically manages a relight and thrust recovery sequence of ignition and fuel introduction.

The EGT (Exhaust Gas Temperature) was observed to be rising for both engines indicating relight. Engine 1’s core deceleration stopped, reversed and started to progress to recovery.

Engine 2 was able to relight but could not arrest core speed deceleration and re-introduced fuel repeatedly to increase core speed acceleration and recovery.

No action for Boeing or GE

The preliminary report on Air India plane crash does not point to any recommendations for either Boeing, the manufacturer of the plane type or GE, the manufacturer of the engines which powered the plane.

Where is the focus now?

With the preliminary report out, the focus will shift on what led to the movement of switches of the Air India AI171 plane that crashes moments after take-off in Ahmedabad. If it was manual, why did that happen and which of the two pilots did it along with ways to ensure this does not repeat again.

Both the government and Air India have been criticised for the way the crash was handled. From a single press conference and lack of regular briefings to suspense over where the Black box is and the time taken to get it from Ahmedabad to Delhi, a lot could have been handled professionally. The airline on the other hand started on the wrong foot with the speech from the Chief Executive Officer being accused of plagiarism from the American Airlines incident earlier this year.