Lionair B739 at Pekanbaru on Feb 14th 2011, runway excursion on landing

Last Update: July 22, 2013 / 15:34:56 GMT/Zulu time

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Incident Facts

Date of incident
Feb 14, 2011

Classification
Incident

Cause
Runway excursion

Airline
Lion Air

Aircraft Type
Boeing 737-900

ICAO Type Designator
B739

The NTSC released their final report concluding the probable causes of the incident were:

The aircraft was decelerated according to the preselected value until the thrust reversers stowed which was known at the last 1000 feet of the runway available and the aircraft speed approximately 70 knots. According performance calculation the aircraft should be able to stop on the remaining runway available. The failure of the aircraft to stop most likely due to the significant deterioration of both the runway friction and brake effectiveness as result of the existing of the combination of the rubber deposit and water spots.

The NTSC reported the aircraft was on approach to Pekanbaru when the crew observed a cumulo nimbus cloud forming over the holding point for Pekanbaru, weather information was heavy rain with visibility of 1km at the aerodrome. The crew therefore decided to enter a hold and wait for the weather to improve. After flying two racetracks the weather improved and the crew decided to commence an ILS approach to runway 36. The aircraft broke out of cloud just before intercepting the glidepath, tower reported winds were calm and cleared the aircraft to land, at that point the crew observed about 11-12 knots tailwind on their flight management computer. Flaps were set to 40 degrees and autobrakes were set to 3.

Following touchdown the crew performed normal landing procedures, deployed thrust reversers, checked spoilers had extended and auto brakes had engaged. However, no significant deceleration was felt by the crew, the flight data recorder showed however that deceleration occurred on target of -0.224G as commanded by autobrakes. The crew began to apply maximum manual braking below 90 knots and stowed the thrust reversers below 70 knots. Below 70 knots the deceleration according to FDR reduced to -0.1G.

About 1000 feet short of the runway end the aircraft slowed through 50 knots, normally that distance would be sufficient to stop the aircraft, the lack of braking efficiency however suggested a problem with the braking coefficient of the runway, the NTSC later analysed: "The maximum manual braking, according to the Boeing manual may produce longitudinal acceleration more than -0.435 G. The manual brake applied up to maximum; however, the rate of deceleration was decreasing. Boeing data retrieved from the DFDAU also found that Calculated Airplane Braking Coefficient was decreasing to average of -1.5. This indicated that the runway friction, which was one of the factors of stopping distance, was ineffective for aircraft deceleration."

The runway was covered by spots of water up to 3cm (more than one inch) deep as well as rubber deposits seriously degradating braking action.

The aircraft went past the runway end and came to a stop on the paved runway end safety area, however the right main gear had gone off the right hand side of the pavement. Immediately after the aircraft came to a stop the commander ordered "all crew on station", after assessing the situation he instructed "aircraft is under control" cancelling a possible evacuation. The passengers disembarked via mobile stairs about 20 minutes later.

The NTSC reported that the flight data recorder revealed the aircraft experienced a tail wind component of 8 knots at the time of touch down and analysed: "Prior to land the pilot received information from the Tower controller that the surface wind was calm. The pilot saw on the FMC that the wind was around 11 knots. The FDR data retrieved that the surface wind condition was tail wind up to 8 knots. The discrepancy of the surface wind data might arise from the fact that the location of the anemometer was surrounded by vegetation and building which might generates turbulence that might cause reading inaccuracy. Based on this condition it can be concluded that the wind speed report from the Tower controller might be incorrect. The incorrect wind information to the pilots may affect to the pilot decision and flying technique."
Incident Facts

Date of incident
Feb 14, 2011

Classification
Incident

Cause
Runway excursion

Airline
Lion Air

Aircraft Type
Boeing 737-900

ICAO Type Designator
B739

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