Loganair SF34 at Stornoway on Jan 2nd 2015, runway excursion

Last Update: October 8, 2015 / 16:57:49 GMT/Zulu time

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Photo of Loganair G-LGNL, SAAB 340 — Loganair G-LGNL, SAAB 340 (Photo credit: markyharky / Flickr / License: CC by)

Incident Facts

Date of incident
Jan 2, 2015

Classification
Accident

Cause
Runway excursion

Airline
Loganair

Flight number
BE-6821

Departure
Stornoway, United Kingdom

Destination
Glasgow, United Kingdom

Aircraft Registration
G-LGNL

Aircraft Type
SAAB 340

ICAO Type Designator
SF34

Airport
Stornoway Airport, Stornoway

Airport ICAO Code
EGPO

A Loganair Saab 340B on behalf of Flybe, registration G-LGNL performing flight BE-6821 from Stornoway to Glasgow,SC (UK) with 25 passengers and 3 crew, was accelerating for takeoff from Stornoway's runway 18 at about 08:33L (08:33Z) when the aircraft veered left off the runway and came to a stop on soft ground with the nose gear collapsed. Two passengers were taken to a hospital with minor injuries, two other passengers reported minor injuries, too, but declined assistance.

The British AAIB have dispatched investigators on site and opened an investigation.

The airport confirmed the outgoing aircraft operated by Loganair went off the runway at about 08:33L. Efforts to move the aircraft off the runway area are under way in order to resume normal airport operations later the day.

The flight was cancelled.

On Oct 8th 2015 the AAIB released their bulletin reporting that the aircraft taxied for a departure on runway 18 from taxiway A1. Tower reported the winds from 270 at 27 knots.

The first officer, pilot flying, lined up for takeoff applying nearly full right aileron consistent with crosswind, the captain (46, ATPL, 3,880 hours total, 3,599 hours on type) advanced the power levers, first officer instructed "autocoarsen high", and the engines accelerated symmetrically reaching 100% torque as the aircraft accelerated through 70 knots. During the early stages of the takeoff roll left rudder was applied and the aircraft maintained heading. With increasing speed the rudder was more and more centralised after which the aircraft made a slight turn to the left followed by a slight turn to the right, then a rapid change of heading to the left occurred, which was countered by right hand rudder which resulted in a slight heading change to the right however could not prevent the aircraft from exiting the left side of the runway leaving the paved surface at about 80 knots. The power levers remained at full power as the aircraft went over a disused runway and back onto grass, the nose gear collapsed in that process. The aircraft came to a stop about 38 meters off the left edge of the runway and about 250 meters past the point the aircraft had exited the runway.

Both propellers were still turning, the first officer used the fire handles to shut the engines down.

A passenger shouted the emergency exits should be opened immediately after the aircraft came to a stop, the propellers were still turning, cabin crew stopped the passengers because the propellers were still turning. As soon as the right hand propeller stopped a passenger opened the right hand overwing exit and the passengers left the aircraft through the exit, the left hand propeller was still turning.

The AAIB summarized crew reported that during the initial stages of the takeoff roll the nose wheel steering was used to maintain the runway center line. When the captain felt they had sufficient rudder authority he moved his hand from the nose wheel steering wheel and the aircraft began to violently veer to the left. The captain could not recall whether takeoff was rejected and power levers were retarded.

The AAIB analysed:

During the attempted takeoff, the rudder was central from 40 kt and remained so until approximately 65 kt. Between approximately 52 and 65 kt, the aircraft turned right slightly before it turned left sharply at approximately 65 kt (Figure 3). Given that the rudder was central, this change of direction might have been caused by one, or a combination of the following factors:

a. Differential braking
b. Asymmetric thrust
c. A change in wind speed and direction
d. A NWS input

Data from the FDR showed that thrust was applied symmetrically throughout the takeoff run, and the manufacturer did not consider that the data for longitudinal acceleration and indicated airspeed supported the use of differential braking.

The crew reported that the swing to the left took place at the handover of control, as the commander released the NWS control and moved his hands to the control yoke, and there might have been a change in NWS input as the nosewheel began to caster. However, because the rudder was in the neutral position and would have had no effect, any NWS input prior to the swing was probably in the ‘turn left’ sense, to oppose the weathercock effect tending to turn the aircraft into the crosswind. In that case, any change in NWS input would have been in the wrong sense to cause a sharp swing to the left.

It was possible that, immediately before the commander released the NWS control, there was a marked drop in the wind speed. In this case, the extant left NWS input would probably have been more than that required to counter the lower crosswind and the aircraft would have begun to turn left. However, this possibility could not be confirmed as there was no data to show whether or not the aircraft had actually experienced a marked change in wind speed or direction.

As the aircraft moved towards the edge of the runway, the pilot applied right rudder in an attempt to return to the runway centreline. Figure 2 shows that, with the aircraft still on the runway, the nose of the aircraft began to turn right in response to the rudder input but the main landing gear maintained their track towards the runway edge. The track of the nose landing gear moved towards that of the right landing gear, indicating that the aircraft was skidding left as it departed the paved surface.

Metars:
EGPO 021020Z 26021KT 9999 VCSH FEW015CB SCT020 04/01 Q1010
EGPO 020950Z 26017KT 9999 VCSH FEW015CB SCT020 03/01 Q1010
EGPO 020920Z 27022G33KT 9999 VCSH SCT015CB BKN020 05/01 Q1009
EGPO 020850Z 26018KT 9999 VCSH FEW015CB SCT018 05/01 Q1009
EGPO 020820Z 27022G33KT 9999 VCSH FEW015CB SCT040 05/01 Q1008
EGPO 020750Z 27019KT 9999 VCSH FEW015CB SCT042 05/02 Q1007
EGPO 020720Z 27024G36KT 9999 VCSH FEW015CB 05/00 Q1006
EGPO 020650Z 27022KT 9999 VCSH FEW015CB 07/02 Q1005
EGPO 020620Z 27021G32KT 9999 VCSH FEW015CB SCT041 05/02 Q1005
EGPO 020550Z AUTO 27022KT 9999 FEW036/// 05/02 Q1004
EGPO 020520Z AUTO 26027G41KT 9999 FEW024/// 04/02 Q1003
EGPO 020450Z AUTO 26026G44KT 7000 -SHRA FEW019/// 04/02 Q1003
EGPO 020420Z AUTO 26016KT 9999 -SHRA FEW014/// SCT026/// 04/02 Q1002
EGPO 020350Z AUTO 26018KT 9999 NCD 04/01 Q1002