ASN Aircraft accident Swearingen SA227-AC Metro III OY-NPB Oslo-Gardermoen Airport (OSL)
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Status:Accident investigation report completed and information captured
Date:Wednesday 2 March 2011
Type:Silhouette image of generic SW4 model; specific model in this crash may look slightly different
Swearingen SA227-AC Metro III
Operating for:Air Norway
Leased from:North Flying
Registration: OY-NPB
MSN: AC-420
First flight: 1981
Total airframe hrs:24833
Engines: 2 Garrett TPE331-11U-612G
Crew:Fatalities: 0 / Occupants: 2
Passengers:Fatalities: 0 / Occupants: 9
Total:Fatalities: 0 / Occupants: 11
Aircraft damage: Damaged beyond repair
Location:Oslo-Gardermoen Airport (OSL) (   Norway)
Phase: Landing (LDG)
Nature:Domestic Scheduled Passenger
Departure airport:Ørland Airport (OLA/ENOL), Norway
Destination airport:Oslo-Gardermoen Airport (OSL/ENGM), Norway
Flightnumber: 990
A Swearingen SA.227AC Metro III, OY-NPB, sustained substantial damage in a runway excursion accident at Oslo-Gardermoen (OSL), Norway. None of the eleven occupants were injured.
The airplane operated on scheduled flight M3990 from OLA (Ørland) to OSL. During roll-out following a normal landing, when the aircraft's speed had decreased to less than 60 kt, the aircraft started an uncommanded turn to the right. The nose wheel steering system was activated. The course could not be corrected, and the aircraft veered off the side of the runway where it became stuck in hard-packed snow one meter deep.
The investigation has shown that the loss of control was most likely caused by a fault in the nose wheel steering. The same problem had occurred six days earlier, but the commander then managed to disconnect the nose wheel steering in time and regained control. The fault could not be reproduced, and the aircraft was released to service after inspection and testing without remarks.
The nose wheel steering system on this aircraft type is relatively complex, and over time several improvements have been made to improve its reliability. The Flight Manual has a caution related to activation of nose wheel steering at speeds higher than normal taxi speed.

There was some freezing rain/freezing fog at the time of the accident.

Probable Cause:

Comprehensive technical examination of the nose wheel steering on OY-NPB uncovered no single causal factor, but some indications of unsatisfactory maintenance. Irregularities that alone or in combination could have caused a temporary fault with the steering were present. The Accident Investigation Board believes that a temporary fault caused the nose wheel to unintentionally lock itself in a position towards the right. No other defects or irregularities that could explain why the aircraft veered off the runway were found.

Accident investigation:

Investigating agency: AIBN (Norway)
Status: Investigation completed
Duration: 1 year and 4 months
Accident number: SL 2012/06
Download report: Final report

Runway excursion (veer-off)

» AIBN Norway

METAR Weather report:
02:41 UTC / local time:
280241Z 19003KT 7000 FEW009 BKN025 M05/M06 Q1027


photo of Swearingen-SA227-AC-Metro-III-OY-NPB
accident date: 02-03-2011
type: Swearingen SA227-AC Metro III
registration: OY-NPB
photo of Swearingen-SA227-AC-Metro-III-OY-NPB
accident date: 02-03-2011
type: Swearingen SA227-AC Metro III
registration: OY-NPB

This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Ørland Airport to Oslo-Gardermoen Airport as the crow flies is 394 km (247 miles).

This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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