Vim B735 at Riga on Feb 17th 2017, runway excursion during rejected takeoff

Last Update: September 27, 2018 / 14:08:06 GMT/Zulu time

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Incident Facts

Date of incident
Feb 17, 2017

Classification
Incident

Departure
Riga, Latvia

Destination
Ufa, Russia

Aircraft Registration
VP-BVS

Aircraft Type
Boeing 737-500

ICAO Type Designator
B735

A Vim Airlines Boeing 737-500, registration VP-BVS performing charter flight NN-9945 from Riga (Latvia) to Ufa (Russia) with about 40 passengers and 7 crew, was about to accelerate for takeoff from runway 18 at about 12:00L (10:00Z) when the aircraft began to yaw right turning about 90 degrees off the runway center line, skidded sideways, departed the right hand runway edge, collided with runway signs and a RVR sensor and became disabled on the runway. There were no injuries, the right hand engine (CFM56), right hand wing leading edge and the left hand engine inlet received damage.

The airport reported the aircraft skidded sideways on the runway. There were no injuries, the runway was closed for about 2 hours.

The aircraft was about to carry the Icehockey Club HC Lada Tolyatti to the next match.

Ground observer Aleksandrs Cubikins reported that there appeared to be a problem with the right hand engine, the aircraft veered right, went off the runway onto soft ground and subsequently managed to re-enter the runway.

On Sep 27th 2018 Latvia's TAIIB released their final report concluding the probable causes of the serious incident were:

Proximate Cause

The flight crew operation was not coordinated in accordance with the take-off procedure.

Root Cause

- The FO (copilot) didn’t act upon the aircraft Flight Manual requirements in the takeoff procedure.
- Insufficient training skills of the flight crew in the Standard Operational Procedures.
- The flight crew didn’t report of any technical failures in the previous flight.

Contributing causes

- Short-term technical failure of the thrust control system.

- The rejected takeoff (RTO) procedure wasn’t initiated immediately after the technical abnormality.

- Erroneous decision to continue the moving after the run off from the runway surface.

Primary cause

Human Factor in an abnormal flight situation.

The TAIIB summarized the sequence of events: "The charts of FDR data after decoding show following: shortly after the takeoff was initiated, the aircraft began a slight left turn followed by a sharp right turn."

Subsequently the TAIIB reported more details based on the FDR:

The FDR data shows that:

LH engine N1 was about 87% while RH engine N1 was about 66% therefore the difference was about 21%. The left engine N1 spooled up faster than the right engine which caused aircraft to deviate slightly right of centerline. Small amounts of left rudder were commanded to correct the heading.

The crew returned the rudder to neutral position shortly before time 640 seconds. Simultaneously, reverse thrust was commanded on only to the left engine which caused the airplane to continue turning left.

Taking into account the results of borescope inspection, which confirmed the impurity of both engines with mud, grit and grass, it was not possible to carry out the engines operation tests in different regimes and the comparison with the technical characteristics of the engine manufacturer's manual.

The TAAIB analysed:

During the early stages of the takeoff roll and well below Vmcg (Minimum control speed on the ground) the engines’ thrust asymmetry occurred suddenly that caused the aircraft movement to the right. The PIC [aircraft pilot] attempted to counter the right yaw with full left rudder pedal input but unsuccessfully. The pilot hadn't start immediately RTO, as a result the aircraft left the runway and after colliding with the airport navigation equipment damaged its fuselage and both engines became unserviceable.

...

According to the CVR conversation recordings, the Pilot Monitoring hasn’t undertaken his duties and hasn’t warned the Pilot Flying of the abnormal engine operation, as well as in the Pilot Monitoring interview it is not mentioned about of any abnormal indications in the takeoff rolling phase.

It was therefore possible that neither of the pilots had the necessary awareness of the engine thrust indications because the crew attention was directed on the aircraft deviation.

This diversion of attention could be a reason why the Pilot Flying hadn’t any information about the thrust asymmetry during the start of the takeoff and therefore he wasn't aware of the reason for the difficulty in maintaining of the directional control of the aircraft.

From the Pilot Flying interview and CVR recordings it has been established that, the Pilot Flying believed the difficulty was based on problems with the nose wheel steering.

...

But the FDR data and CVR recordings show that the Pilot Flying hadn't decided to start the Rejected takeoff procedure when the airplane deviated heading more than 20 degrees and the aircraft was from the runway.

Metars:
EVRA 171220Z 24006KT 8000 OVC006 04/04 Q1011 R18/290195 NOSIG
EVRA 171150Z 24005KT 210V280 8000 OVC005 04/04 Q1011 R18/290195 NOSIG
EVRA 171120Z 24006KT 210V280 9000 -RA OVC004 04/04 Q1011 R18/290195 NOSIG
EVRA 171050Z 24007KT 210V270 7000 -RA OVC004 04/04 Q1011 R18/290195 NOSIG
EVRA 171020Z 23008KT 5000 -RA BR OVC004 04/04 Q1011 R18/290195 NOSIG
EVRA 170950Z 23007KT 210V270 8000 -RA OVC004 03/03 Q1011 R18/290195 NOSIG
EVRA 170920Z 23008KT 6000 -RA OVC004 03/03 Q1011 R18/290195 NOSIG
EVRA 170850Z 23008KT 9000 -RA OVC005 03/03 Q1011 R18/290195 NOSIG
EVRA 170820Z 23008KT 9000 -RA OVC003 03/03 Q1011 R18/290195 TEMPO 4000 BR
EVRA 170750Z 23007KT 200V260 5000 -RA BR OVC003 03/03 Q1011 R18/290195 TEMPO 4000
EVRA 170720Z 23007KT 4100 -RA BR OVC003 03/03 Q1011 R18/290195 NOSIG
Incident Facts

Date of incident
Feb 17, 2017

Classification
Incident

Departure
Riga, Latvia

Destination
Ufa, Russia

Aircraft Registration
VP-BVS

Aircraft Type
Boeing 737-500

ICAO Type Designator
B735

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