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Flight 507's last moments
11/05/2007 20:21 - (SA)
Douala - Three jetliners sat ready for takeoff at Douala International Airport, their crews waiting for a massive thunderstorm to move away.
Just a few minutes past midnight, all three radioed air traffic control to check the weather report. They were told the storm would take another hour to dissipate, and the Cameroon Airlines and Royal Air Maroc crews opted to wait it out.
But Captain Francis Mbatia Wamwea of Kenya Airways Flight 507, already delayed for an hour and carrying scores of passengers with onward connections to catch, judged the weather had improved sufficiently to permit departure for Nairobi, Kenya.
It was a fateful decision that investigators believe may have cost the lives of the nine crew and 105 passengers of Flight 507, which was ensnared in the raging storm this past Saturday and crashed into the jungle less than a minute after takeoff.
After Wamwea gave the go-ahead, the Kenyan Airways crew radioed the tower, pulled away from the gate and taxied toward Runway 12, heading roughly southwest from the airport.
Cleared for takeoff
Douala tower cleared the flight for takeoff at 01:00, instructing it to report on reaching 1 500m.
It was not clear what time that final voice transmission was received from the Boeing 737-800.
The plane nose-dived into a swamp just 30 seconds after becoming airborne, killing all aboard.
The passengers included Cameroonian merchants, an American AIDS expert, businesspeople from China, India and South Africa, a Tanzanian returning from peacekeeping duties in Ivory Coast, a UN refugee worker from Togo. Anthony Mitchell, a Nairobi-based correspondent for The Associated Press, was among the victims.
The six-month old plane was of the newest generation of the world's most popular airliner and has an excellent safety record. This is only the second time a 737-800 has crashed with the loss of all on board. Last September, an airliner belonging to Brazil's Gol airline collided in mid-air with an executive jet over the Amazon jungle.
One Cameroonian investigator and a government pilot assisting the probe, both speaking on condition of anonymity, said Wamwea's decision to depart into one of the violent tropical storms that regularly ravages parts of equatorial Africa during the rainy season was most likely the pivotal factor in a sequence of events that led to the crash in which all 114 aboard perished.
In Kenya on Friday, Kenya Airways chief executive Titus Naikuni said investigators would have to make the final assessment. The probe was likely to take months.
"We don't want to start speculating here," he said. "So whether the pilot did the wrong thing or the right thing, I cannot answer that."
Stormy weather takeoff 'routine'
Flight crews are responsible for the decision whether to take off or land in bad weather, usually depending on guidelines prescribed by their airline. And while air traffic control can take measures to prevent flights, including closing down airports, such drastic measures are highly unusual outside the northern hemisphere where heavy winter snows can block runways and bring traffic to a standstill.
Douala airport is not equipped with weather radar, but the 737-800 is. Pilots routinely take off into stormy weather and then rely on radar to guide them around the towering cumulonimbus thunderheads that can cause structural damage to airframes.
Wamwea, 53, was an experienced flyer with about 8 500 hours on jets. He had joined Kenya Airways 20 years ago and enjoyed the reputation of a diligent and professional pilot.
The co-pilot, Andrew Kiuru was only 23. He joined the airline a year ago after completing flight school in South Africa.
The cockpit voice recorder has not yet been found, so no details of the final exchanges between Wamwea and Kiuru are available. It remains unclear which man was flying the plane at the time, but Wamwea would have been the ultimate authority.
The flight data recorder has been recovered.
Distress message
Two minutes after Flight 507 would have been expected to reach 5 000 feet, the point at which it had been instructed to check in, Douala Area Control Centre issued a distress message. This is normal practice by air traffic control when unable to immediately establish contact with an aircraft, a fairly frequent occurrence.
But controllers, who had lost sight of the plane fairly quickly because of the storm, were not unduly worried because the plane had fuel for six hours flying time.
A search was launched at 02:44 when a French radar station sent in a message that an airplane distress signal had been picked up. A Cameroonian air force plane and two helicopters first flew over a region far to the south, basing their search on the distress signal which was in fact hundreds of kilometres away from the actual crash.
It is unclear why the signal was so far off the mark, but it appears the plane's emergency locator beacon's final signal was garbled - indicating a false position.
And although the crash site is virtually directly beneath the flight path for planes taking off from Douala, nobody saw it because of the jungle canopy that covers the area.
The wreckage was found 40 hours after takeoff by a local hunter who chanced upon it in a mangrove swamp and reported it to the air force. It was located just 5.4 km from Runway 12. Using speed calculations, experts estimate the plane had been in the air for just 30 seconds and had never climbed over 914.4 meters.
'A loud boom'
Commercial jets regularly fly over the area, one of several standard departure routes from Runway 12. Villagers living near the swamp said they heard planes passing overhead during the night, and a particularly loud boom which sounded like a thunderbolt.
Since there were no witnesses to the crash itself, investigators have pieced together the known facts and formulated several theories on what could have happened.
The wreckage in the thick jungle indicated the plane flew nose-first into the ground at a nearly 90 degree angle. It was found buried deep in a crater of reddish-brown muck with only tiny bits of the rear fuselage and wings left above ground. Trees nearby were smashed, but otherwise the jungle canopy remains intact, making the site almost invisible from the air.
Investigators said the nose-dive indicated that a violent gust of wind within a thundercloud may have flipped the airliner over, throwing it into a fatal dive. Although modern jets can usually fly through storm clouds, storms in Africa are particularly violent at this time of the year, investigators said.
The location of the wreckage also indicates the pilot was manoeuvring at the time, banking sharply to the right. This would have exposed the raised left wing to the gust, investigators said.
The low altitude, would have made it impossible to recover from the resulting dive.
Investigators said they cannot yet discount other factors, including mechanical failure, pilot disorientation or even sabotage. But no sign of a blast or fire has been found so far by the search teams, which include seven experts from the US National Transportation Safety Board and two Boeing representatives.
Investigators say it will likely take months to collect and analyse the evidence. They said a final report on the crash would probably not be completed this year.
- AP
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