Norwegian B738 at Helsinki on Jul 11th 2017, runway excursion on landing

Last Update: June 29, 2018 / 17:37:42 GMT/Zulu time

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Incident Facts

Date of incident
Jul 11, 2017

Classification
Incident

Flight number
DY-4287

Aircraft Registration
LN-NHF

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

Airport ICAO Code
EFHK

A Norwegian Air Shuttle Boeing 737-800, registration LN-NHF performing flight DY-4287 from Stockholm (Sweden) to Helsinki (Finland) with 166 people on board, landed on Helsinki's runway 04L in heavy rain at about 19:06L (16:06Z) but overran the end of the runway and while attempting to steer the aircraft onto the last high speed turn off skidded right off the paved surface of the runway end safety area and came to a stop on soft ground. There were no injuries, the aircraft sustained minor if any damage.

The airport reported the aircraft was pulled off the soft ground by a tug, the passengers subsequently disembarked normally.

On Jun 29th 2018 Finland's Onnettomuustutkinta (AIBF, accident investigation board) released their final report in Finnish (Final report in English) concluding the probable causes of the incident were (editorial translation from Finnish kept below):

- The aircraft was 53 minutes late when leaving Stockholm due to late arrival into Stockholm.

- The captain decided to not vacate the runway via high speed turn off WK due to the high speed of the aircraft and opted for taxiway WD at the end of the runway about 1200 meters further down the runway. The captain stowed spoilers and reversers in order to taxi to WD as quickly as possible.

- Information about runway length remaining is provided by different colours of runway lights. The captain applied brakes too late to slow the aircraft sufficiently for the turn into taxiway WD. He did not anticipate the effects of the wet runway and the lack of spoilers onto the braking distance.

- There was lack of crew communication during the roll out.

- The actions of the crew and crew cooperation during roll out did not comply with company standard operating procedures.

- The first officer was new in the organisation and did not voice his own concerns about runway adequacy. On personal initiative he warned the cabin of a possible collision.

- The aircraft exited the runway at low speed and no injury occurred.

The AIBF analysed that the 53 minutes delay on departure put pressure on the flight crew to make up as much of the delay as possible. It is problematic for pilots if their flights are often delayed due to circumstances outside their control, in particular on short haul flights where they have little chance to catch up with delays. The captain thus used higher speeds than normal in accordance with company manuals.

The AIBF continued analysis that the aircraft made a very soft touch down on runway 04L at Helsinki, the crew did not immediately recognize they were already on the ground, the spoilers did not deploy automatically and auto-brakes did not engage. The captain deployed the spoilers manually which activated the auto-brakes at the same time, the devices were thus activated with a delay resulting in too high a speed while the aircraft was approaching high speed turn off WK, so that the captain decided to pass the exit and remain on the runway. The captain stowed the spoilers and released auto-brakes in order to proceed the remaining 1200 meters to next and last exit WD as quickly as possible, the aircraft's speed was still at 90 knots. The company handbook did not state any procedure or call outs for stowing the spoilers and released auto-brakes under such circumstances, however, it would be good practise to call out the plan to permit the other pilot maintain situational awareness. The speed of the aircraft reduced slightly during further roll out, light braking was initiated by the captain 850 meters before the runway end at 80 knots. 570 meters before the runway end he applied increased braking at 74 knots, the aircraft did not hydroplane, however the runway friction was decreased by the water layer on the runway, with the spoilers stowed this had adverse effect on the braking distance. The captain had not called out the stowing of the spoilers and the first officer, a very inexperienced pilot, did not react to the fact the spoilers were stowed. The disengagement of auto-brakes should also have been announced with positive feedback by the pilot flying to brake manually. The first officer's inexperience probably affected his unresponsiveness, he trusted the captain's experience and skills although he felt the flight's safety had been compromised. In the last stage however the first officer warned the cabin of a possible collision.

About 350 meters before the runway end the captain applied maximum braking and deployed the thrust reversers again, the thrust reversers deployed with delay. Spoilers were not deployed. The speed was about 60 knots at that point. The captain turned the steering wheel into the direction of exit WD, the aircraft however drifted off the runway and came to a soft stop on soft ground. There were no injuries.

Metars:
EFHK 111820Z 12013KT 9999 FEW003 BKN004 OVC006 16/15 Q1003 BECMG 6000=
EFHK 111750Z 11013KT 9999 -RA SCT004 OVC006 16/15 Q1003 BECMG 6000 BKN003=
EFHK 111720Z 12014KT 7000 -RA FEW004 BKN006 BKN020 16/15 Q1003 BECMG 8000=
EFHK 111650Z 13010KT 090V160 6000 -SHRA FEW004 BKN007 BKN020CB 17/16 Q1004 BECMG 8000 BKN009 BKN020=
EFHK 111620Z 17012KT 5000 -SHRA FEW004 BKN009 BKN020CB 16/16 Q1004 BECMG 8000 BKN009 BKN020=
EFHK 111550Z 10012KT 060V120 5000 SHRA FEW004 BKN009 BKN025CB 16/15 Q1004 BECMG 8000 NSW BKN012 BKN020=
EFHK 111520Z 09012KT 050V110 4000 SHRA FEW005 BKN009 BKN030CB 16/16 Q1005 BECMG 8000 NSW BKN012 BKN020=
EFHK 111450Z 10016KT 5000 SHRA FEW015 SCT020 BKN040CB 17/15 Q1006 TEMPO 2500 BKN014=
EFHK 111420Z 10011KT 9999 -SHRA FEW027 SCT040CB BKN060 19/14 Q1006 TEMPO 5000 SHRA=
EFHK 111350Z 09012KT 9999 -SHRA FEW030 FEW040CB BKN075 19/15 Q1006 TEMPO 5000 SHRA=
EFHK 111320Z 10012KT 9999 -SHRA FEW030 SCT040CB BKN080 19/15 Q1007 TEMPO 5000 SHRA=
Incident Facts

Date of incident
Jul 11, 2017

Classification
Incident

Flight number
DY-4287

Aircraft Registration
LN-NHF

Aircraft Type
Boeing 737-800

ICAO Type Designator
B738

Airport ICAO Code
EFHK

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