Greenland DH8B at Nuuk on Dec 29th 2014, runway excursion

Last Update: January 29, 2015 / 17:58:55 GMT/Zulu time

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Incident Facts

Date of incident
Dec 29, 2014

Classification
Report

Flight number
GL-421

Aircraft Registration
OY-GRK

ICAO Type Designator
DH8B

An Air Greenland de Havilland Dash 8-200, registration OY-GRK performing flight GL-421 from Nuuk to Paamiut (Greenland) with 5 passengers and 3 crew, had aborted the flight to Paamiut due to runway conditions at Paamiut and decided to return to Nuuk. The aircraft landed on Nuuk's runway 23 in light snowfall and calm winds at 12:34L (15:34Z), but veered left off the runway and came to a stop with all gear on soft ground about 30 meters/100 feet off the left runway edge and about 835 meters/2740 feet down runway 23.

Denmark's HCL released their preliminary report reporting that a preliminary post flight examination by the HCL revealed a defective micro switch at the right hand power lever, part of the beta range protection circuitry.

The HCL reported that the captain was pilot flying and the first officer pilot monitoring. The aircraft landed on runway 23 following a visual circling, flaps were set to 35 degrees. After touchdown the commander selected reverse (beta) on both engines and noticed that the aircraft unexpectedly began to veer left, disengaged reverse and used wheel brakes as well as nose wheel steering in an attempt to keep the aircraft on the runway, the aircraft however continued to veer left and exited the runway. The crew assessed the situation, noticed no apparent damage and no injuries, and decided to not evacuate the aircraft. The crew requested an immediate runway inspection suspecting the runway conditions did not match the reported conditions.

The HCL reported that the runway inspection at 15:46Z measured runway 05 friction coefficients 19/21/21, the runway was covered 100% by 1mm of dry snow and 50% of 1mm ice. At 13:40Z the runway 05 friction coefficients were reported at 40/48/50.

Examination of the defective micro switch showed that it was no longer spring loaded and the plunger moved freely disappearing inside the switch housing.

The HCL made following preliminary analysis:

A divergence between reported (measured at 13:40 hours) and effective (measured at 15:46 hours) braking action coefficients on runway 23 in combination with a momentary failure of the right hand power lever micro switch causing a momentary activation of the right hand propeller beta backup protection deemed to have had a negative effect on the flight crew’s ability to maintain directional control, which resulted in the aircraft running off the side of the runway (runway excursion).
Incident Facts

Date of incident
Dec 29, 2014

Classification
Report

Flight number
GL-421

Aircraft Registration
OY-GRK

ICAO Type Designator
DH8B

This article is published under license from Avherald.com. © of text by Avherald.com.
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