Overloading, ‘bird hit’ among probable causes of air crash: experts

Investigation into A1-171 flight crash in Ahmedabad reveals potential causes like overloading, bird hit, and engine failure.

While the causes of the A1-171 flight crash in Ahmedabad are being investigated and information from the flight data and cockpit voice-recorder was awaited, aviation experts theorise — judging from videos of the plane’s short flight — that overloading, a potential bird hit and the rare instance of both engines failing could have prevented the air-plane from getting sufficient ‘lift’ to ascend.

The 787-Dreamliner has maximum take-off weight of 227.9 tonnes and a fuel capacity of 126,206 litres. The twin engines are equipped, even under the worst scenario, to operate for up to 330 minutes on a single engine. “The odds of both engines failing simultaneously during take-off are quite small or about one in a billion,” Abhay Pashilkar, Director, CSIR-National Aerospace Laboratories (NAL), which designs civilian planes, told The Hindu.

A plausible scenario was the plane being overloaded, he explained. This meant an incorrect estimate of the combined weight of the loaded airplane and the quantity of available fuel. This along with the external temperature determines the speed at which the plane must attain to keep rising and a misjudgment on that can cause the plane to stall and drop. “High temperatures on a hot day can thin out the air, meaning you get less lift from the same speed. Weight, temperature altitude all affect lift. Prior to take-off, the pilots have charts and are informed of the weights and the necessary speeds for specific altitudes,” said Mr. Pashilkar. “If the pilot didn’t hit the appropriate speeds, it would reflect in the flight recorder and we will know.”

Aviation expert Capt. Mohan Ranganathan told The Hindu that a ‘bird hit,’ or birds being sucked into both engines couldn’t be ruled out. He explained that growth of grass near the runway during the monsoon season attracts a lot of insects, which in turn, attract birds.

“I suspect bird ingestion may have happened. And from the footage that we have seen, the landing gear did not retract. If that happened, the aircraft could have climbed higher and travelled further and possibly would crossed the residential areas,” said Capt. Ranganathan.

In January 2009, an Airbus A320, taking off from the LaGuardia airport, New York city, encountered a flock of birds that caused both engines to malfunction. This led to the pilot taking the unusual decision to land the plane on the Hudson River but in the process, also successfully rescuing all the 155 passengers on board.

The Ahmedabad air crash has once again brought the spotlight back on safety with regard to Boeing aircraft, including the Dreamliner. Though this is the first time a Dreamliner has crashed, the aircraft has faced safety issues earlier.