Microbursts - Fremdeles en killer - Curt Lewis

UN-chartered CRJ downed by microburst: inquiry

International investigators believe a severe microburst during an attempted go-around pushed a Georgian Airways Bombardier CRJ100ER into a fatal dive at Kinshasa.

The aircraft (4L-GAE) had been approaching runway 24 while operating a domestic service from Kisangani on behalf of the United Nations.

Just one individual, a passenger, from the 33 occupants of the twinjet survived when it struck the ground - some 170m to the left of the threshold - skipping and inverting as it broke up.

In an inquiry published by the Democratic Republic of Congo's ministry of transportation, the investigation team states that Kinshasa had been subject to a low cloud-base squall line and severe thunderstorm activity at the time of the 4 April 2011 crash.

The crew had been cleared to conduct a straight-in localiser approach to the runway, and had discussed options for skirting around the thunderstorms indicated on the aircraft's weather radar.

As the CRJ descended towards the runway it remained to the left of the localiser path. The inquiry says that, less than 10nm from the threshold, the aircraft adjusted its heading further away from the path, before the crew sighted the runway and manually aligned the jet at a distance of 2nm.

The aircraft, below the minimum descent height of 472ft above ground, encountered rain as it reached short final. Its pilots had lost sight of the runway as the jet descended to 224ft and they opted to execute a go-around.

"During the process of go-around, a positive rate of climb was established with appropriate airspeed," says the inquiry, which has ruled out the possible effect of somatogravic illusion in the subsequent crash.

As the aircraft approached 400ft above ground, it met a "severe weather phenomenon" which the inquiry believes was "probably" a microburst, triggering a windshear alarm. The aircraft pitched from 4-5° nose-up to 7° nose-down in a "very short time", the probe states, and rapidly lost height.

"Before the crew could react to the pitch down and recover from the steep descent, the aircraft impacted the terrain," it adds. It struck the ground at 180kt, at 10° nose-down pitch, and was destroyed, coming to rest inverted some 400m beyond the initial impact point.