The mystery of Ethiopian Airlines Flight 409

By Charles Bremner | TimesOnline

Stormy weather or sabotage are being cited in the aviation world as possible factors in the crash of Ethiopian Airlines flight 409 off Beirut.

There is no evidence yet to suggest what caused the modern Boeing 737-800 airliner to hit the Mediterranean minutes after take-off. But attention focused on powerful thunder storms in the area and the possibility that an explosion could have caused the sudden end to the flight.

The crew were talking to the area “departure control” which was handling their flight when their transmissions stopped. This could mean that the aircraft suddenly broke up or that the crew were too busy handling an emergency to transmit a message.

The airport was under heavy rain and a line of thunderstorms were positioned off the coast, along the route of the Boeing as it climbed out of Beirut. The pilots would normally avoid the violent “cells” in the cumulonimbus thunder clouds, but these have brought down airliners in the past.

Most recently, in May 2007, a Kenyan Airways Boeing 737 crashed after a night take off in thunderstorms and heavy rain from Douala, Cameroon, killing all 114 on board. The cause of the crash has still not been determined, but the bad weather is thought by experts to have played a big role.

The explosive turbulence inside a cumulonimbus can upset even the biggest airliners. Such storms were an element in the crash last June 1 of Air France flight 447 off Brazil, according to the preliminary findings.

Lightning strikes are not normally a danger to airliners but dense rain can occasionally cause jet engines to “flame out” and stop. In this case, the crew would normally report their predicament to controllers, telling them that they were gliding and attempting to restart.

It is too early to rule out sabotage, as the Lebanese Government did, unless it holds information that it has not released.

If the pilots did not reported any problem, an explosive or other foul play cannot be excluded, aviation experts said. Speculation over possible sabotage or terrorism is natural, given Beirut’s position in the Middle East and Ethiopia’s support for the government of Somalia in its conflict with Islamist insurgents.

Eye-witness reports of a mid-air explosion should not be taken at face value. Such reports are common whenever a night-time crash is witnessed. The usual reason is the much higher speed of light than sound. The witness sees the fire of a distant crash before the noise, giving the false impression of preceding it.

Simple pilot error has sometimes caused airliners to crash after night take-off.

In January 2004, an Egyptian Boeing 737 hit the Red Sea shortly after taking off from Sharm el-Sheikh, killing all the 148 aboard, most of them French tourists. It was found that the automatic pilot was not connected and the pilots, flying in pitch dark, let the aircraft fly almost on to its back before they lost control.

Ethiopian Airlines is viewed as one of the best on the African continent and the Boeing 737 is one of the world’s most reliable aircraft. The last fatal incident involving the airline was in November 1996. A hijacked Boeing 767 crashed-landed off the Comoros Islands after running out of fuel. Fifty of the 175 people aboard survived.

The Boeing 737 has been manufactured since 1967 with over 6,000 aircraft delivered. On average there are 1,250 737s airborne at any given time.