On 6 November 2015, a Boeing 737-900 (PK-LBO) being operated by Batik Air on a scheduled domestic passenger flight from Jakarta Soekarno-Hatta to Yogyakarta as BTK 6380 overran landing runway 09 at destination by just over 80 metres after making an ILS approach in day VMC. The aircraft stopped to the left of the extended centreline with its nose landing gear collapsed. The 168 occupants were uninjured and a doors-only evacuation was subsequently completed.
The aircraft in its final stopping position [Reproduced from the Official Report]
An Investigation was carried out by the Indonesian National Transportation Safety Committee (NTSC/KNKT). Data from the FDR and 2 hour CVR were successfully downloaded. The FDR providing data on 1,265 parameters over approximately 53 hours of aircraft operation which included 31 flights including the accident flight.
It was noted that the 45 year-old Captain, who had been PF for the accident approach, had a total of 3,628 flying hours which included 2,661 hours on type. The 22 year-old First Officer had a total of 1,787 flying hours of which all except 191 hours were on type.
It was established that the flight proceeded uneventfully until it was on final approach. Reference Speed (Vref) for the ELW of 63,900kg was 141KIAS. On the basis of the ATIS weather report, the Captain decided that the landing on runway 09 (LDA 2,200 metres) would be with flaps 40 and auto brake 3 but after subsequently observing magenta returns on the weather radar over the airport, he decided to use Flap 30 instead as recommended in the FCOM for situations where wind shear may occur. The aircraft was positioned on the ILS approach to runway 09 and soon after transfer to the TWR frequency, the controller advised that the runway was wet and so it was decided to change the autobrake setting from 3 to Maximum. Landing clearance was accompanied by advice that the surface wind was calm.
FDR data showed that the AP and A/T had been disconnected at approximately 700 feet agl and the speedbrake armed at 500 feet agl. Stabilised approach criteria specified by the Operator were not met at 500 feet agl or thereafter. Passing 381 feet agl, the speed was Vref + 16 and from 200 feet to 10 feet, there was a 6 knot tail wind component. 50 feet agl was passed at Vref + 12 and the aircraft subsequently floated above the runway at 10 feet agl for 6 seconds before touching down 730 metres beyond the threshold at 154 knots (Vref + 13). TWR "provided the landing time and instructed the aircraft to exit the runway via taxiway N3 and proceed to parking stand number 2".
During the landing roll, maximum auto brake was disconnected with the aim of increasing deceleration using manual braking but the applied pressure was much reduced from that applied with autobrake maximum and as a consequence the rate of deceleration decreased. Despite developing concern at the length of runway remaining, the thrust reversers, which had already been reduced from maximum passing 91 knots, had been stowed at 76 knots compared with the recommended <60 knots and this too reduced the rate of deceleration at a time when the length of runway remaining was evidently problematic. Shortly after the aircraft deviated left near the end of the paved surface and crossed onto grass (see below). The nose gear then collapsed and soon afterwards the aircraft came to a stop. The controller "noticed that the aircraft had overrun and pushed the crash bell to inform the Airport Rescue and Fire Fighting (ARFF) Station.
The ground track of the aircraft over, on and beyond the runway [Reproduced from the Official Report]
Two seconds after FDR data showed that the aircraft had come to a stop, the First Officer transmitted "attention, attention crew on station" and the Captain transmitted "BRACE, BRACE, BRACE". Two and a half seconds after that, the First Officer said "Captain, Shutdown Captain" and after a further 10 seconds the Captain again transmitted "BRACE, BRACE, BRACE". Subsequently, the Captain asked the Cabin Crew to check outside for any signs of fire and the First Officer asked the TWR the same. No such signs were reported. Contrary to the QRH Checklist for evacuation, the APU was then started and approximately three and a half minutes after the aircraft had stopped, the Evacuation Checklist was reviewed. The CVR record showed that the evacuation was initially envisaged as taking place without use of the escape slides but it was then decided that they should be used. This evacuation, began approximately nine minutes after the aircraft stopped using only the four doors and was completed in approximately eight minutes.
It was noted that "the decision to land or go around basically rests on an assessment by the pilot in command of the possibility of a critical condition on landing". It was considered that "the CRM principle requires the PM to call out any deviation and to take any action if there is no acknowledgement from the PF" whereas in this particular approach, there had been "no discussion between the pilots concerning the landing distance following the change of the landing configuration to use flaps 30 for the existing condition and no call out from the PM when the speed was 13 knots above the approach speed". The speed being maintained was considered to be "an indication that one of the specified elements of a stabilised approach had not been achieved and that a go around was therefore required".
It was considered that notwithstanding the failure to use braking and the thrust reversers to best effect when attempting to stop the aircraft, "external factors contributed to the reduction in the deceleration rate" and that these included the effect of runway condition on braking action. In this connection, discrepancies in the procedures for friction testing between the Aerodrome Manual and the specified Runway Friction Test SOP were noted as was the absence of any documentation of daily runway inspections for the last month prior to the accident and particularly therefore any observations of standing water. It was evident that the prescribed emergency procedures for evacuation following the overrun had not been performed appropriately by the crew. Specifically:
- there had been an unacceptably slow response following the aircraft coming to a stop - the Captain had to be prompted to commence engine shutdown, the use of the Evacuation Checklist was not prioritised and an evacuation was not commenced until nine minutes after the aircraft stopped.
- the 'BRACE BRACE BRACE' instruction must be given in advance of the risk not after the aircraft has stopped as in this case.
- starting the APU was contrary to explicit instructions in the QRH Evacuation Checklist which directs that if it is running, it should be shut down when the engines are shut down since running it may increase the risk of fire since there is a possibility of system damage.
The Findings of the Investigation included the following in respect of the performance of the flight crew:
- A combination of the absence of both an updated landing distance calculation when the landing configuration was changed to flap 30 and callouts of speed above the Vref might have resulted in lack of pilot awareness of the landing distance required prior to and after touchdown and to the decision to continue landing.
- Had the aircraft been on the proper landing profile and achieved touchdown in the touchdown zone (TDZ), it would have been able to stop on the runway with braking action good or medium.
- The fact that the speed at touchdown was 13 knots above the applicable Vref and touchdown occurred late resulted in the available runway not being sufficient for the aircraft to stop with medium braking action. With good braking action the runway available would have been sufficient albeit with a relatively small margin which might have been exceeded by the improper application of brakes and thrust reversers.
- Four conditions which affected the landing distance were:
- the aircraft floated for about 6 seconds and touched down at the end of the touchdown zone, 427 metres beyond the aiming point after bouncing once;
- the airspeed at touchdown was 13 knots above Vref and there was an average tailwind component of 6 knots;
- the thrust reversers were stowed at a higher than recommended speed and there was little braking for about 305 metres after the autobrakes were disconnected;
- the wet runway conditions resulted in a reduction in deceleration.
- The actions of the Captain following the overrun were contrary to those prescribed by the Aircraft Operator in a number of respects and indicated the inadequacy of crew evacuation training.
Other Findings included the following:
- Weather data for the Airport was provided by the Air Force Meteorological Unit using an AWOS but the only sight of the AWOS monitor display available to ATC was via a CCTV link which was not always of useable quality so that the TWR controller then had to call the Met Unit to obtain the latest AWOS information.
- The information in the Jeppesen publication available to the crew in relation to the provision of runway Stopway, Clearway and RESA was different to that in the AIP.
- Regulations require the airport operator to conduct runway friction checks to a regular schedule but the last runway friction check was performed in 2009.
- The absence of runway friction level information for aircraft operators might reduce the accuracy of the landing distance calculation, either for dispatch planning or for the pilot in flight prior to landing.
- The Airport Operator had not carried out any hazard identification, risk assessment or risk mitigation in respect of the runway surface condition awareness.
- The DGCA Airport Certification renewal process had not recorded a finding in respect of runway inspections including the required period runway friction check.
- The DGCA had issued an exemption for the absence of a RESA for runway 27 by referring to the mitigations performed by airport operator.
- The Investigation could not find any Directorate General of Civil Aviation approval certificate for the Yogyakarta ANSP.
Two Contributory Factors were formally identified as follows:
- The absence of a landing distance calculation following aircraft reconfiguration for landing and the excessive approach speed with no reminder callout might have resulted in the pilots deciding not to continue with the landing.
- The conditions which led to the aircraft floating and eventually touching down at the end of the touchdown zone 13 knots above Vref with an average 6 knot tailwind followed by low brake pressure for 305 metres and then the disconnection of the autobrakes and removal of the thrust reverser application at a higher than recommended speed along with medium braking action extended the landing distance.
A further Safety Issue was also identified as "the external factors such as runway condition which might have contributed to the reduction in the rate of deceleration whilst brake pressure and thrust reversers were (still) close to maximum."
Safety Action by Batik Air as a result of this event and known to the Investigation at the time of completion of the Investigation included the following:
- issue of a series of 'Notices to PiIots' requiring strict adherence to existing SOPs and the addition of both new ones and the introduction of new 'recommended practices'. The latter included the use of flap 40 for Boeing 737 landings on any runway with an LDA of less than 2500 metres regardless of whether it is wet or dry.
- issue of a caution in respect of the beginning of runway 27 at Yogyakarta being "slippery when wet" accompanied by an instruction that in such conditions, auto brakes should not be disengaged or thrust reversers stowed until the aircraft is at taxi speed.
- request to Jeppesen to check discrepancies in the information on stopway, clearway and RESA at Yogyakarta compared to the AIP.
- enhancement of pilot simulator training in respect of evacuation procedures and introduction of joint CRM training for flight crew and cabin crew in order to improve crew coordination during an emergency.
Eighteen Safety Recommendations were made at the conclusion of the Investigation as follows:
- that Batik Air should improve crew member emergency training to ensure that all crew members perform the evacuation according to the company procedures. [04.O-2016-20.1]
- that the Yogyakarta Airport Operator should perform daily inspections of the movement area as specified in the Aerodrome Manual (AM) and the Airport Standard Operating Procedure (SOP). [04.B-2016-22.1]
- that the Yogyakarta Airport Operator should develop a procedure for the measurement of water depth on runways and taxiways as required by Chapter 4.5 of Appendix 1 to Civil Aviation Safety Regulation (CASR) Part 139 Volume I. [04.B-2016-23.1]
- that the Yogyakarta Airport Operator should update the AM and SOP to implement runway friction measurement according to the specification in Advisory Circular (AC) and CASR Part 139-23. [04.B-2016-24.1]
- that the Yogyakarta Airport Operator should develop a reporting system which enables the dissemination of significant information on runway condition to the Air Traffic Service (ATS) unit and allows that Unit to provide the necessary information to arriving and departing aircraft without delay as required in ICAO Annex 14 Chapter 2.9.1. [04.B-2016-25.1]
- that the Yogyakarta Airport Operator should review the possibility of developing an instrument approach procedure for runway 27. [04.B-2016-51.1]
- that the AirNav Indonesia District Office Yogyakarta should provide the Tower Controller with adequate access to current weather information by installing an AWOS display monitor at the Tower control desk. [04.A-2016-26.1]
- that the AirNav Indonesia District Office Yogyakarta should review the possibility of developing an instrument approach procedure for runway 27. [04.A-2016-51.2]
- that the Directorate General of Civil Aviation should emphasise to all aircraft operators that they must comply with stabilised approach criteria. [04.R-2016-1.2]
- that the Directorate General of Civil Aviation should ensure that all aircraft operators' procedures for assessing the landing distance required in prevailing conditions provide an adequate figure for comparison with the landing distance available. [04.R-2016-27.1]
- that the Directorate General of Civil Aviation should emphasise to all aircraft operators that they must implement a standard callout procedure for approach. [04.R-2016-28.1]
- that the Directorate General of Civil Aviation should emphasise to all aircraft operators that they must conduct emergency training which will ensure that crew members take appropriate action during an emergency. [04.R-2016-29.1]
- that the Directorate General of Civil Aviation should ensure that Airport Operators Manuals contain the requirements specified in the CASR Part 139, AC CASR Part 139-23 and Manual of Standards CASR Part 139. [04.R-2016-30.1]
- that the Directorate General of Civil Aviation should ensure that all airport operators conduct inspections of movement areas according to the approved manuals. [04.R-2016-22.2]
- that the Directorate General of Civil Aviation should ensure that all airport operators implement the runway friction measurement according to the procedures specified in the AC CASR Part 139-23. [04.R-2016-24.2]
- that the Directorate General of Civil Aviation should include in the Indonesia Civil Aviation Safety Regulations, a requirement for a reporting system from the airport operator to the ATS unit which will enable the dissemination of significant information on runway condition to arriving and departing aircraft without delay as required by ICAO Annex 14 Chapter 2.9.1. [04.R-2016-25.2]
- that the Directorate General of Civil Aviation should issue approval certificates for the Air Traffic Services providers. [04.R-2016-31.1]
- that the Directorate General of Civil Aviation should review the possibility of developing an instrument approach procedure for runway 27. [04.R-2016-51.3]
The Final Report was released on 13 June 2016.