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What happens if almost all of a plane’s vital navigation instruments suddenly fail simultaneously, just as the aircraft is coming in to land? It happened on an international flight carrying 370 people last week.

The crew of an Air India B777-300, operating flight AI-101 from Delhi to New York JFK, faced a sudden, seemingly inexplicable problem – multiple instrument failure.

The flight started in the northern Indian city of Ahmedabad. The Ahmedabad Mirror reported panic among passengers as the crew brought the plane in for a safe landing under emergency conditions at another airport than scheduled, having diverted to Newark Liberty International Airport, New Jersey.

The flight was on final approach at JFK in reduced visibility when the crew decided to go around and attempt the landing again, the Aviation Herald reported.

As the crew began the final landing approach, multiple instruments suddenly ceased to function. The crew advised they had lost the localiser (which provides horizontal guidance), the radio altimeter (an electronic device that measures altitude immediately below the aircraft), two other altimeters and the Traffic Collision Avoidance System – which does exactly what it sounds like.

The crew advised they could not make an instrument landing and sought a nearby airport where the weather would permit them to land manually, using the one radio altimeter and one basic altimeter that were still working.

After checking, Air Traffic Control advised the crew to try Newark New Jersey, which is less crowded and had just released a weather report indicating overcast with cloud cover at 400 feet (120 metres). The crew decided to divert to Newark.

At that point, the crew reported they had just 7200kg of fuel left, at the tail end of the 14-hour flight. That’s generally less than an hour’s flying time, though it varies, and they had almost 40 minutes to go. Newark Airport advised emergency equipment was standing by for their arrival.

The Aviation Herald reports: “On final approach tower advised they were getting low on the approach and advised altimeter was 30.12. The aircraft continued for a safe landing on Newark’s runway 04R about 90 seconds after the low altitude alert and about 38 minutes after the go around at JFK. The crew advised no further assistance was needed.”

According to the Ahmedabad Mirror online, the emergency landing caused panic among passengers, “however, security officials were on board to comfort the passengers till the time of deboarding” at Newark.

The airline is looking into the incident.

An Air India B777-300ER

Written by Peter Needham