MD-82 crash probe may focus on engine

Published 3:42 pm Thursday, August 21, 2008

BRUSSELS, Belgium — Takeoffs are considered one of the most precarious stages of flight, when an aircraft is accelerating down a runway with its engines at high thrust and the aerodynamic stress on the plane at its greatest.

But crashes of planes with two or more engines — such as the Spanair MD-82 that went down in Madrid on Wednesday — are rare during takeoffs, in part because pilots are trained to succeed, even if one of the engines fails.

The runway at Barajas airport also would have been long enough for the Spanair pilots to abort the flight, if they had found out about an engine failure soon enough.

That is why as investigators in Spain try to determine what caused Madrid’s Spanair MD-82 crash that killed 153 people, aviation experts are speculating that it may have been a combination of several factors.

“There may have been some unknown complication (of technical factors) that we are not yet aware of, and which could have been beyond the crew’s control,” said Patrick Smith. He is a former pilot of the MD-80, a slightly shorter version of the Spanair type plane, and an aviation author based in Boston.

An engine failure on a single-engine aircraft during takeoff is likely to be disastrous, leaving the plane without the power or speed needed to remain airborne. But multiengine passenger airliners are built to continue flying, even if one of the engines fails. In fact, crews are trained to safely handle such emergencies.

Experts say that is why accidents on takeoff are rare for commercial carriers.

“All commercial aircraft are certified to perform a normal takeoff at maximum weight, even if they lose an engine,” said Joao Moutinho, a technical director of the European Cockpit Association, an umbrella group in Brussels, Belgium, that represents 38,000 European pilots and flight engineers.

“If they have two, three or four engines, they (the pilots) must all pass this test,” he said. “They have to be able to perform a safe takeoff and safely return to the airport, if they lose an engine.”

The Spanair plane that crashed Wednesday was on its second takeoff attempt. The first one was abandoned because of an air intake gauge that showed overheating. But the airline has said it doesn’t know what caused the accident.

Spanish media reports have said that one of the two engines failed and may have caught fire during takeoff. Witnesses saw the plane’s left engine explode and catch fire before the aircraft went down, according to the newspaper La Vanguardia.

Before departure, pilots in multiengine planes calculate the velocity at which they can safely abort a takeoff in an emergency — given the size of the runway they are using — and the speed at which they can get airborne, even if one engine fails.

Safety regulations require runways to be long enough for aborted takeoffs, and runway 36L at Barajas airport is one of the world’s longest commercial runways.

Smith said it’s likely that a combination of factors caused Wednesday’s crash.

“It’s possible that a catastrophic engine failure — such as an explosion or fragmentation of internal parts — could have affected hydraulics, flight controls, etc.,” he said.

“You’re making the transition from ground to flight, and an aircraft is at that point inherently more susceptible to an incident or accident, should something go seriously wrong,” he said.

If that happened in Madrid on Wednesday, the Spanair MD-82 simply may have been beyond the pilots’ control, said Smith.