How The Autopilot Works

(Captain SS Panesar retired from Indian Airlines as Director of Flight Safety and Director of Training. He has logged more than 24,000 hours on flying Airbus A-300, Boeing-737 and many other aircraft. He was also involved in investigation of aircraft incidents and accidents while on deputation to the DGCA.)

It has been nearly four months since the ill-fated Malaysia Airlines Boeing-777 aircraft disappeared. It was carrying 227 passengers and 12 crew members.

Australian Deputy Prime Minister Warren Truss has said that it was "highly, highly likely that the aircraft was on autopilot before it crashed. Otherwise it could not have followed the orderly path that has been identified through the satellite sightings".

Let me explain autopilot in detail. Autopilot once coupled with the flight management system follows the route of the flight - in this case Kuala Lumpur to Beijing.

Autopilots do not replace a human operator, but assist them in controlling the aircraft. They allow the pilot to control the aircraft's height, direction and speed.

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Autopilots generally divide a flight into taxi, takeoff, climb, cruise, descent and landing. Not all passenger aircraft flying today have an autopilot system, but most countries do not allow aircraft to fly over their skies if they are not fitted with autopilots.

Also, if the pilot wants to change the route, he can do so using the flight management system (FMS) - without having to switch off autopilot.

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The advantages of the autopilot are that it reduces pilot fatigue especially during long-haul flights and also makes an aircraft fly smoothly and helps fly in stormy weather, since it is more steady. It is very important in case of engine failure.

But an autopilot can be dangerous if it malfunctions. If any gadget in the system fails, it sends a warning signal and the pilot immediately switches to manual mode. Every pilot is trained to fly safely with autopilot and to take necessary action in case it malfunctions. 

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In 2009, the autopilot malfunctioned in Air France flight 447. All 228 passengers and cabin crew aboard were killed. In 2013, a UPS cargo jet crashed in Alabama, Birmingham because of autopilot malfunction.

I believe that in the case of MH370, either of these three things could have happened: the pilot might himself have changed the route; or a hijacker might have forced or overpowered the pilot to change the route; or the flight might have crash landed or was forced to land in the sea because of shortage of fuel.

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But it is still a mystery why the pilot could not transmit or press the transponder to indicate an emergency or hijacking alert. If there is an emergency, pilots enter the frequency 7700. All stations within 200 miles are immediately alerted and can track the plane's height, speed and direction. If a hijacker or anyone else switches off the transponder, the ground control will only get information about the direction of the aircraft, not the speed and height.

No trace of the plane has been found despite an extensive search deep in the Indian Ocean. It's impossible to conclude what happened to the plane without the recovery of the black box - the flight's data and voice recorder.

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