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B739, Pekanbaru Indonesia, 2011
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|On 14 February 2011, a Lion Air Boeing 737-900 making a night landing at Pekanbaru overran the end of the 2240 metre long runway onto the stopway after initially normal deceleration largely attributable to the thrust reversers was followed by a poor response to applied maximum braking in the final 300 metres. Whilst performance calculations showed that a stop on the runway should have been possible, it was concluded that a combination of water patches with heavy rubber contamination had reduced the friction properties of the surface towards the end of the runway and hence the effectiveness of brake application.|
|Actual or Potential
|Human Factors, Runway Excursion|
|Flight Conditions||On Ground - Normal Visibility|
|Type of Flight||Public Transport (Passenger)|
|Origin||Jakarta/Halim Perdanakusuma International Airport|
|Take off Commenced||Yes|
|Location - Airport|
|Tag(s)||Inappropriate crew response (automatics),|
|Tag(s)||Overrun on Landing,|
Significant Tailwind Component,
Landing Performance Assessment
|Damage or injury||Yes|
|Causal Factor Group(s)|
On 14 February 2011, a Boeing 737-900 being operated by Lion Air on a scheduled domestic passenger flight from Jakarta to Pekanbaru overran landing runway 36 onto the stopway in normal night visibility after a standard touchdown on a surface wet with water patches after unexpectedly poor deceleration. There were no injuries to the 219 occupants who were subsequently disembarked by airstairs and the aircraft sustained only minor damage.
An Investigation was carried out by the Indonesian NTSC with access to recorded data from the SSFDR but not from the 30 minute SSCVR which was left running after the aircraft stopped so that the relevant period was overwritten. It was noted that Lion Air had not provided the total and aircraft type pilot hours for either pilot to the Investigation.
It was found that the arriving aircraft, with the aircraft commander as PF, had delayed its approach until the worst of some convective weather had moved away from the aerodrome and had then commenced an ILS approach to runway 36 for which the LDR calculated from the FCOM was 1700 metres and thus comfortably within the 2240 metres available. During the approach, TWR gave a spot wind of ‘calm’ but the FDR recorded that on short final, there had actually been a consistent tailwind component of between 8 and 10 knots. This effect of this unknown factor was to increase the required landing distance previously calculated by a further 250 metres.
It was note that the official weather report for the time at which the aircraft touched down gave the wind as calm, the surface visibility as 3000 metres and the cloud base as Cb/Sc at 1500 feet aal.
The FDR recorded that the aircraft touched down with an ELW of 66 tonnes at the prescribed touchdown point with flaps 40 and auto brake 3 armed after a stabilised approach had been flown. Speed at touchdown was recorded as 155 knots in the present of an 8 knot tailwind component. This speed was 17 knots above the target speed and this excess had the effect of adding a further 264 metres to the previously calculated LDR. With the addition of a further 20 metres on account of the ISA+6 surface temperature, the LDR calculation was now 2234 metres compared to the 2240 metre LDA.
Advice was received from Boeing that the preselected rate of longitudinal acceleration with auto brake 3 set was - 0.224g which FDR data showed had been achieved during the high speed part of the landing roll largely because of the effect of the thrust reversers applied with the engine N1 reaching 80% so that only a small amount of brake pressure being applied. This rate of deceleration was observed from the FDR to have remained “relatively constant” until maximum manual brake pressure was applied at approximately 70 knots ground speed and with approximately 300 metres to go till the end of the runway. The thrust reversers were stowed at approximately 50 knots by which time their effect on the rate of deceleration had become minimal.
It was concluded that absence of the normally expected effectiveness of the applied maximum braking below 70 knots ground speed was indicative of runway friction not being sufficient for normal deceleration. Inspection of the runway following the overrun found that significant rubber deposits were present on the runway between the 18 threshold and the 18 touch down marker located at 300 metres from the threshold. The examination also found some water spots. It was noted that the combination of the rubber deposit and water spots would significantly reduce both the runway friction and brake effectiveness.
It was found that the airport operator had a regular schedule for rubber deposit removal every six months with the most recent removal prior to the overrun being on 31 December 2010 at the TDZ for runway 18 (i.e. the end of runway 36). It was also established that the most recent runway resurfacing had been carried out in 2010 following which runway friction measured by Mu meter had found skid resistance to be between 0.55 and 0.59. This was compared with the content of a DGCA Advisory Circular issued after the investigated event which stated that the minimum skid resistance should be 0.6. In this respect, the Investigation noted that a routine runway inspection using the “sand patch” method on 1 January 2011 had found that the condition of the surface in the vicinity of the runway 18 TDZ was “smooth”.
After the overrun, the runway was examined for the presence of standing water and it was found that there were several slight depressions in the runway surface containing water up to a depth of 3 cm.
The disparity between the consistent tailwind component recorded on the FDR during the final approach and the spot wind of ‘calm’ given by the TWR controller at the same time was considered. It was concluded that this was, in the light of the probable effect on wind speed measurement of vegetation and buildings surrounding the source anemometer, attributable to the unrepresentative readings available to the controller.
The formal statement of Probable Cause concluded that “the aircraft was decelerated according to the preselected value until…..the last 1000 feet of the runway available….(and thereafter)….the failure of the aircraft to stop (was) 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 (patches)”.
Ten Safety Recommendations were made as a result of the Investigation as follows:
- that the Directorate General of Civil Aviation should ensure that all airport operators conduct periodic runway friction tests to ensure the runway friction is within the approved value
- that the Directorate General of Civil Aviation should ensure that all airport operators conduct rubber deposit removal (using) an approved method and personnel in a period according to the DGCA Advisory Circular number SE.04 issued in 2012
- that the Directorate General of Civil Aviation should ensure that weather observation sensors (are) put in a location that (is) free of any possible disturbance according to the ICAO Annex 3, section 4.5 ‘Observing and reporting of surface wind’
- that the Directorate General of Civil Aviation should ensure all aircraft operators conduct proper flight crew training on Approach and Landing Accident Reduction (ALAR) and include the criteria for a stabilised approach in simulator training
- that [the Department of Transport Agency which oversees the management of airports and ATS in western Indonesia] Angkasa Pura II should conduct periodic runway friction testing to ensure (that) the runway friction is within the approved value
- that [the Department of Transport Agency which oversees the management of airports and ATS in western Indonesia] Angkasa Pura II should conduct rubber deposit removal (using an) approved method and personnel (at the maximum intervals specified in) the DGCA Advisory Circular number SE.04 issued in 2012
- that [the Department of Transport Agency which oversees the management of airports and ATS in western Indonesia] Angkasa Pura II should ensure that weather observation sensors (are located) free of any possible disturbance according to the ICAO Annex 3, section 4.5 ‘Observing and reporting of surface wind’
- that Lion Air should emphasise flight crew training on Approach and Landing Accident Reduction (ALAR) and ensure that the criteria for (a) stabilised approach are included in simulator training
- that Lion Air should ensure that pilots calculate the landing distance required based on the actual runway condition
- that Lion Air should introduce a comprehensive procedure to ensure (that) the electrical power to the CVR (is) disconnected immediately after a (reportable event) to prevent automatic overwriting of (relevant) information
It was stated in the Final Report of the Investigation published in mid 2013 that, as a result of the occurrence of the investigated event and a second similar overrun which had occurred at the same airport the following day, a meeting had been held on 3 May 2011 attended by representatives of the DGCA, PT Angkasa Pura II and the Pekanbaru Airport Authority. It was noted that this meeting had agreed that Safety Action would be taken by the Pekanbaru Airport Authority as follows:
- revise the scheduled interval for cleaning to remove rubber deposits from six months to ‘on condition’ based on inspection findings.
- carry out repairs to the runway surface to ensure the elimination of standing water patches
- issue a Notice To Airmen to advise that the runway skid resistance was 0.55 and was below the minimum requirements of 0.60 and that this condition may result in poor braking action when the runway is wet.