B738 / AT46, Jakarta Halim Indonesia, 2016
B738 / AT46, Jakarta Halim Indonesia, 2016
On 4 April 2016, a Boeing 737-800 crew taking off in normal night visibility from Jakarta Halim were unable to avoid an ATR 42-600 under tow which had entered their runway after ambiguity in its clearance. Both aircraft sustained substantial damage and caught fire but all those involved escaped uninjured. The Investigation concluded that contributory to the accident had been failure to use a single runway occupancy frequency, towing of a poorly lit aircraft, the potential effect on pilot detection of an obstruction of embedded approach lighting ahead of the displaced landing threshold and issues affecting controller traffic monitoring effectiveness.
On 4 April 2016, a Boeing 737-800 (PK-LBS) being operated by Batik Air Indonesia on a scheduled domestic passenger flight from Jakarta Halim to Makassar as ID 7703 was accelerating for take-off on runway 24 in normal visibility at night and already at high speed when the crew realised that there was an obstruction ahead. Despite deviating to the right away from the centreline, they were unable to completely avoid it and a collision occurred. Fires began in the damaged left wings of both aircraft and an emergency evacuation of the 737 was ordered and successfully accomplished with no injuries to the 56 occupants. The two occupants of the other aircraft and the two occupants of the towing vehicle were also uninjured. The other aircraft was subsequently found to be an out of service Avions de Transport Regional ATR 42-600 (PK-TNJ) being operated by TransNusa Aviation and under tow. Both aircraft sustained significant impact damage to their structures but the RFFS arrived within 2 minutes and were able to quickly extinguish both fires, which minimised further damage.
An Investigation was carried out by the Indonesian National Transportation Safety Committee (NTSC) - the Komite Nasional Keselamatan Transportasi (KNKT). A Preliminary Report was published on 9 May 2016. Data from both the FDR and CVR of the 737 were successfully downloaded and used to support the Investigation. The towed aircraft was found to have been without electrical power so its FDR and CVR contained no data relevant to the accident. A recording of communications on the TWR frequency was available but communications between the TWR and the tow vehicle took place on a different frequency which was not subject to recording and it was noted that this was contrary to regulatory requirements.
The 55 year-old Captain of the 737 had 18,765 hours total flying experience which included 1,825 hours on type. The 26 year-old First Officer, who was PF for the accident take-off prior to the Captain taking over when the risk of collision became apparent, had 368 hours total flying time which included 215 hours on type. The 36 year-old Controller, 25 year-old Assistant Controller, 52 year-old ATC Supervisor and 25 year-old Flight Data Officer on duty in the TWR at the time of the collision all held valid Air Traffic Controller Licences endorsed with Halim Aerodrome Control Ratings.
Two licensed aircraft maintenance engineers were on the flight deck of the ATR 42 solely to apply the aircraft brakes when required. The 45 year-old driver of the towing vehicle had 15 years’ experience of ground handling tasks and had been employed by Jasa Angkasa Semesta, the Ground Services contractor providing towing service to TransNusa, since 2012. He held a Ground Support Equipment Licence which included an 'Aircraft Towing Pushback Tractor' Rating. However, it was noted that there was (explicitly) no regulatory requirement for the drivers of airside vehicles to have access to a radio nor were there "requirements for the drivers of vehicles towing aircraft to understand the geography of the aerodrome; aerodrome signs, markings and lights and radiotelephone operating procedures".
The repositioning of the out of service ATR 42 was pre-planned to be a tow from one side of the only runway to the other, entering from taxiway C and travelling along the runway before exiting onto taxiway G and all those involved in the operation were aware of this. It was found that in accordance with local 'custom and practice', the ATR 42 had been towed without an engine running and with no electrical power to any aircraft systems which meant that neither the radio communication or aircraft lighting systems were functioning. Communication between the driver of the towing vehicle and Halim TWR was achieved using handheld radios which used a discrete frequency not documented in the AIP and took place in Bahasa (the local language). In place of illuminated aircraft navigation lights, portable red and green commercial strobe lights with dimensions of approximately of 8 × 3 cm were routinely put on each wing tip instead. These lights were approximately of 8cm x 3 cm in size and their use was found to be "in accordance with a TransNusa Engineering Instruction" which had been accepted by Jasa Angkasa Semesta. In addition, the towing vehicle was fitted with an anti-collision light above the driver’s compartment and this and the vehicle headlights were illuminated during the towing process.
The agreement between Jasa Angkasa Semesta and TransNusa for the former to provide ground handling at Halim airport "did not mention the specific technical procedure for towing or pushback". However, the ATR 42 towing procedure was described in the AMM and there was a corresponding 'Job Instruction Card' which described towing making use of the electrical system with one engine running without the propeller rotating ('hotel mode'). There was no AMM or other manufacturer-approved procedure allowing towing of an ATR 42 aircraft at night without an engine running - although it was noted that there was a modification available for the ATR 72 which could facilitate this. However, the contractor's Ramp Handling Manual, without reference to any specific aircraft types, was found to state simply that any aircraft being towed at night or in low visibility conditions "should be adequately illuminated so it can be seen". It also included the statements that "prior to the commencement of any towing operation a check should be made that the communications link between the tractor operator and the aircraft flight deck crew is functional" (when in fact there was no such communication channel) and "in the event that the communications link between the tractor operator and the aircraft flight deck crew is broken during the tow the operation should be immediately stopped". The Investigation could find no evidence of any documented ATC procedure which covered off-ramp aircraft ground movement other than in the course of a flight. It was also noted that it "could not find a Standard Operational Procedure [in which the Airport Operator] required the operator of a vehicle towing an aircraft to communicate with the controller on the same frequency as that used for aircraft movement".
It was established (see the aerodrome chart below) that after the 737 had been cleared to pushback and taxi from Stand B2 by the TWR controller on the designated TWR frequency 118.6 MHz, a tow vehicle driver had requested permission to reposition the ATR 42 from the adjacent stand B1 to the south apron using a handheld radio on discrete frequency - 152.7 MHz. He was cleared by the Assistant Controller to follow the 737 and to "report when on taxiway C". The (runway) Controller was aware of this communication but because of the different frequency used, the 737 crew were unaware that they were being followed. There was no evidence that the two controllers had agreed how to co-ordinate their simultaneous use of the two radio channels.
By the time the towed ATR 42 had begun to move forward along the apron, the 737 had reached taxiway C, where it was instructed to hold clear of the runway until a landing aircraft had passed. As the 737 continued taxiing onto the runway, the towed ATR42 was about to enter taxiway C and the Assistant Controller instructed the tow vehicle driver to "expedite the towing and follow (the 737)" and the instruction was correctly acknowledged. It was noted that this clearance "was given without a specific route to be followed and explicit clearance to cross or to hold short of the runway". Three further communications between the Assistant Controller and the tow vehicle driver were reported by the latter to have occurred but this was denied by the Assistant Controller who admitted that he had not monitored the progress of the towed aircraft on taxiway C.
On reaching the end of runway and entering the turning area, the 737 reported ready for take-off and, since the Controller stated that he had not seen any vehicle or object on the runway, he then issued take-off clearance. The pilots did not discern anything ahead on the runway but noted that glare from (approach) lighting ahead of the displaced landing threshold had "affected forward vision for a short time".
The towed ATR 42 had by now entered the runway from taxiway C and begun to move along it in the direction of taxiway G. When the tow vehicle driver saw that the 737 was lining up at the runway full length, he reported asking ATC (on 152.7 MHz) whether the 737 was "initiating take off" but received no reply. This reported transmission was one of the three which the Assistant Controller claimed did not occur. In the reported absence of any communication from ATC, the tow vehicle driver increased speed and began to move to the right hand side of the 45 metre-wide runway. As the 737 accelerated through approximately 80 KIAS with the First Officer as PF, the pilots reported seeing "an object which they could not identify" ahead and the Captain took control and steered the aircraft towards the right side of the runway centreline to track between it and the north side runway edge. Impact occurred a few seconds later as the RAAS auto callout of "V1" occurred approximately 850 metres from the beginning of the runway and approximately 100 metres beyond the runway intersection with taxiway G. The 737 crew immediately initiated a rejected take off and their aircraft came to a stop approximately 400 metres further on having been returned to the runway centreline. An emergency evacuation was made with all slides deployed. FDR data showed that the 737 had reached a maximum speed of approximately 140 knots. The left wings of both aircraft were severed as was most of the empennage of the ATR 42. The 737 pilots did not realise that the aircraft they had collided with was under tow until they had evacuated their own aircraft using all exits. The RFFS arrived at the accident site within two minutes and used foam to quickly extinguish the fires in both aircraft.
The Investigation was told by the AirNav Indonesia Halim management that there were typically more than 100 aircraft and vehicle movements across the runway between the north and south aprons each day.
The effect of the glare reported by the 737 Captain before beginning take off from the full length of the displaced landing threshold runway (see the diagram below) was investigated and considered in the context of the time needed for the human eye to adjust from bright lighting to a significantly darker night environment immediately afterwards. It was concluded that the reported glare was likely to have hindered the pilots' early perception of the dimly-lit towed aircraft - or any other similar obstruction - on the runway ahead.
The effect of lighting within the TWR cabin on the ability of controllers to observe externally was also considered. It was noted that the reflection of the internal lights on the glass windows "reduced contrast differences to external objects" and had made it more difficult to detect the towed aircraft prior to the issue of the take-off clearance to the 737. However, quite separately from the failure of the Assistant Controller to monitor the progress of the ATR 42 on Taxiway C, it was found that various procedures related to the towing of aircraft between the two airport ramps via the runway which had been in use a the time of the collision were inadequate, in particular relevant air traffic procedures and the training and qualification of those permitted to undertake aircraft towing.
The Investigation formally identified three 'Contributing Factors', defined as defined as "actions, omissions, events, conditions, or a combination thereof, which, if eliminated, avoided or absent, would have reduced the probability of the accident or incident occurring, or mitigated the severity of the consequences of the accident or incident" as follows:
- The handling of two movements in the same area with different controllers on separate frequencies without proper coordination resulted in the lack of awareness to the controllers, pilots and towing car driver.
- The communication misunderstanding of the instruction to follow ID 7703 most likely contributed the towed aircraft enter the runway.
- The lighting environments in the tower cab and turning pad area of runway 24 might have diminished the capability to the controllers and pilots to recognise the towed aircraft that was installed with insufficient lightings.
A total of 20 Safety Recommendations were made in the course of the Investigation.
On 7 April 2016, the 4 were issued on the basis of the initial findings of the Investigation as follows:
- that AirNav Indonesia Halim should develop a procedure for all aircraft movements on the manoeuvring area including aircraft movement without aircraft own power which requires communication with air traffic control on the same frequency. [04.A-2016-51.1]
- that AirNav Indonesia Halim should evaluate the current lighting of the Tower cab to prevent glare that may distract controllers' (external) view. [04.A-2016-52.1]
- that AirNav Indonesia Halim should remind ATC controllers to maintain continuous watch on the aircraft movement on the manoeuvring area, especially when an air traffic control clearance has been issued. [04.A-2016-53.1]
- that AirNav Indonesia Halim and the Halim Airport Operator should develop a procedure for vehicles and aircraft on the manoeuvring area which requires them to be equipped with serviceable lights visible by the air traffic controller. [04.B-2016-54.1]
On 26 April 2016, a further 3 were issued also on the basis of the initial findings of the Investigation as follows:
- that AirNav Indonesia Halim and the Halim Airport Operator should inform aircraft operators to initiate take-off from the displaced threshold of runway 24. [04.B-2016-57.1]
- that the Directorate General of Civil Aviation should review a requirement for all aircraft movement on the manoeuvring area including the movement of aircraft under tow to communicate with the air traffic controller on the same frequency. [04.R-2016-55.1]
- that the Directorate General of Civil Aviation should develop a procedure for vehicles and aircraft on the manoeuvring area which requires them to be equipped with serviceable lights visible to the air traffic controller. [04.A-2016-56.1]
These Recommendations were all included in the Preliminary Report but were not repeated in the subsequent Final Report. A series of Safety Actions taken by the recipients of these Safety Recommendations whilst the Investigation was being completed were noted, as was action by Avions de Transport Regional (ATR) who have developed a procedure which allows operators of both ATR 42 and ATR 72 aircraft to supply anti-collision and navigation lights with battery power when towing by night without engines running. In respect of the Recommendation to AirNav Indonesia Halim that aircraft operators should be required to begin take-offs from runway 24 from the displaced threshold rather than the full runway length, it was noted that since then, some aircraft had continued full length take offs. It was also specifically noted that on 22 June 2016, there had been a similar runway incursion event between a towed aircraft and an aircraft taking off in which an aircraft under tow in the opposite direction had been cleared to cross the runway soon after an aircraft had also been cleared to take off from it. However after prompt intervention by ATC and an early rotation by the departing aircraft, there had been no actual risk of collision and so there had been no investigation by the NTSC/KNKT because the event "did not meet the definition of a Serious Incident in the ICAO 'Manual on the Prevention of Runway Incursion' Doc 9870".
On completion of the Investigation, a further 13 Safety Recommendations were issued as follows:
- that Batik Air Indonesia enhances the FCTM Chapter 3.24 text on the Rejected Takeoff Decision to add that the PIC should announce the abnormality simultaneously. [04.O-2017-7.1]
- that Batik Air Indonesia reviews the evacuation procedure and considers the area (that) can be observed through the viewing windows. [04.O-2017-7.2]
- that TransNusa Aviation Mandiri ensures that aircraft are adequately lighted during night operation in accordance with CASR 91.209. [04.O-2017-7.3]
- that TransNusa Aviation Mandiri considers risk assessment, compliance with regulations and the specification required prior to the issue of any Engineering Instruction. [04.O-2017-7.4]
- that Jasa Angkasa Semesta (the Ground Services contractor providing towing service to TransNusa) reviews the requirement of personnel licensing for towing car driver as required by the regulation standard, including the language requirement. [04.L-2017-7.5]
- that Jasa Angkasa Semesta (the Ground Services contractor providing towing service to TransNusa) ensures that the SOP for the towing procedure is properly implemented. [04.L-2017-7.6]
- that AirNav Indonesia Halim updates SOPs to accommodate controller coordination to assure the safe conduct of aircraft and vehicle movement on the manoeuvring area. [04.A-2017-7.7]
- that AirNav Indonesia Halim ensures that all taxi or towing clearances issued contain explicit instructions for crossing or holding short of any runway as required by the Manual of Air Traffic Services Operational Procedures. [04.A-2017-7.8]
- that AirNav Indonesia Halim and the Halim Airport Operator reinforce the implementation of the Safety Recommendation made earlier in this Investigation (04.B-2016-57.1 on 26 April 2016) in view of occurrences since its issue of the operational practice which it was recommending should be avoided. [04.B-2017-7.9]
- that the Directorate General of Civil Aviation reviews the procedure for aircraft movement on the manoeuvring area for the airport operator and the air navigation provider to accommodate the requirement of CASR 91.209. [04.R-2017-7.10]
- that the Directorate General of Civil Aviation reviews the requirements for licensing of personnel as driver of an aircraft towing vehicle to meet the corresponding ICAO standard. [04.R-2017-7.11]
- that the Directorate General of Civil Aviation reviews the contents of CASR 179 Air Traffic Rules subpart 170.039 to ensure its clarity [04.R-2017-7.12]
- that the Directorate General of Civil Aviation updates the current published AIP to reflect the total runway length at Halim was reduced from 3,000 metres to 2,800 metres. [04.R-2017-7.13]
The Final Report was published on 10 April 2017.