This story released by Bureau of Aircraft Investigation Investigation (AAIB) in Ahmedabad Report It is based on which flight 171 tries to convince the cause of the crash of 171. Let us understand it in a systematic way so that the developments are clear.
Air India Flight 171 accident: Events
1. Start of flight (before 1:38:42 pm)
Air India flight 171 generally started the takeoff process. The aircraft achieved the maximum air speed of the required speed for takeoff, ie 180 knots (about 333 km/h). By this time everything was normal. The flap handles of the aircraft were in a 5-degree position, which is a general setting for takeoff. Thrust liver (which control the power of the engine) were also in a position of takeoff, ie on full power.
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2. Sudden closure of engines (1:38:42 pm)
Around 1:38:42 pm, the fuel cutoff switch of both engines (engines 1 and engine 2) of the aircraft, which are normally in “run” (current) position. One after the other went into a “cutoff” (closed) position. This change took place in a interval of 1 second. The closure of the cutoff switch stopped the fuel supply to the engines.
Due to which the speed of both engines (N1 and N2) started decreasing rapidly. In the cockpit voice recording, a pilot was heard asking why did you do the fuel cutoff? The second pilot replies that I did not. This shows that both the pilots were surprised by this incident. They did not understand how the switches were closed on their own.
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3. Lowering speed of engines and active of RAT (01:38:47 am)
Due to the closure of fuel supply, the speed of both engines also went below the minimum speed (minimum Idol speed). As a result, RAM air turbine (RAT) hydraulic pump started automatically to provide strength to the aircraft’s hydraulic system. This RAT pump became active at 01:38:47, which gives the aircraft emergency hydraulic power when the main engine would not be working.
4. Response of pilots: Rewrinking fuel switch (01:38:52 pm)
The pilots understood the situation and took immediate action. At around 01:38:52 pm, the fuel cutoff switch of the engine 1 was brought back to “run” from the “cutoff”. Two seconds later, at 01:38:54 pm, the inlet door of the Automatic Power Unit (APU) began to open, indicating the APU’s automatic start. APU provides additional power to the aircraft.
Subsequently, the fuel cutoff switch of the engine 2 on 01:38:56 UTC was also brought to “run” position from “cutoff”. When the fuel cutoff switch is brought into a “run” position, the Full Authority Digital Engine Control (FADEC) system of the aircraft begins the process of automatically re -starting engines. In this, the supply of ignition and fuel starts again.
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5. Release of engines (01:38:56 to 01:39:05 pm)
Exhaust gas temperature (EGT) for both engine 1 and engine 2 began to grow, indicating that the engine was in the process of restarting. The core speed (N2) of the engine 1 stopped. Slowly started recovering. The engine 2 was also released, but there was difficulty in stabilizing its core speed. The FADEC system was trying to increase the speed of the engine 2 by repeatedly adding fuel, but it could not succeed completely.
6. Made Call and Accident (01:39:05 pm)
At around 01:39:05 pm, a pilot broadcast the emergency message “Mede Mede Mede”, which indicates a serious emergency in aviation. Air Traffic Control (ATCO) asked about the call sign, but no response was received from the pilots. Soon after, the aircraft crashed out of the airport border. EAFR data recording stopped at 01:39:11, which can be considered time for accident.
7. Emergency response (01:44:44 pm)
The air traffic controller saw the aircraft crashing. Immediately initiated emergency response. 01:44:44 pm Crash fire tender (special vehicle for fire extinguishing and rescue) left for rescue and fire fighting work. Fire and rescue services of the local administration also participated in this work.
8. Status of the residue of the aircraft
Investigations found that many important parts of the aircraft were severely damaged by fire …
- Flap Handle: It was in a 5-degree position, which is normal for takeoff. EAFR data also confirmed this.
- Thrust Lever: Both the thrust liver was damaged by the fire and found in the idol (minimum power) position. But according to EAFR data, they were in a position of takeoff thrust until the accident.
- Fuel control switch: Both switches were found in “run” positions.
- River Lever: They were bent, but were in “stoved” (closed) position.
- Landing Gear Lever: It was in “down” position.
- To/GA and Autothrole Discanect switch: Their wires were visible, but there was a lot of damage.
9. Flight data and cockpit voice recorder
The aircraft had two enhanced airborne flight recorders (eafr), one near the tail and the other in the front. Both of them recorded flight data and cockpit voice recording simultaneously. Downloaded data contained 49 hours of flight data and 6 flights, including the accident flight. The cockpit voice recording was 2 hours. The entire incident was recorded in it.
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What did the Pilot Association say on this investigation report
Airline Pilots Association of India has responded to the preliminary report of India’s Air India Flight 171 on the accident of Air India Flight 171 on June 12.
“The tone of the investigation and the direction suggests that it has an inclination towards blaming the pilot’s mistake. We completely dismiss the notion and demand that the investigation be fair and based on facts.”
“This report was leaked in the media without a responsible officer’s signature or source. The investigation lacks transparency, as the investigation process is being kept secret, which is keeping its credibility and public confidence. Eligible and experienced personnel, especially line pilots (real flying pilots) are still not being included in the investigation team.”
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