On 28 March 2018, a Boeing 767-300 (4X-EAK) being operated by El Al on a scheduled international passenger flight from Tel Aviv to Rome as LY 385 and a Boeing 737-700 (D-ABLB) being operated by Germania on scheduled international passenger flight from Tel Aviv to Berlin Tegel as ST4915 were both being pushed back from adjacent gates in reduced normal (in excess of 5km) night visibility in rain on a floodlit manoeuvring area when they collided which resulted in significant damage to both aircraft but no injuries. All 367 occupants of the two aircraft were disembarked to buses and returned to the terminal building and after an initial accident site examination by members of the assigned independent investigation team, the aircraft were then separated. Damage to both aircraft was subsequently classified as severe with the 767 declared a hull loss.
The two aircraft tail sections intertwined after the accident. [Reproduced from the Official Report]
An Accident Investigation was carried out by the Israeli Aviation Accidents and Investigation Office (AIAI) of the Ministry of Transport and Road Safety in accordance with the provisions of ICAO Annex 13. The factual part Investigation was based on a range of relevant recorded ATC data and on visual evidence from other airport sources as well as evidence obtained during the almost immediate on-site preliminary attendance of AIAI investigators.
The Flight and Ground Personnel Involved
- The 53 year-old Boeing 767 Training Captain in command had a total of 15,000 hours flight experience and was accompanied by a 57 year-old Captain undergoing type conversion who had 7 hours on type. The 32 year-old Boeing 737 Captain had a total of 4,700 hours flight experience all of which except 300 hours were on type.
- The 35 year-old GND Controller involved was a former Israeli Air Force controller who had since had 8 years experience as a civil controller of which the first 5½ years had been as a TWR controller at Eilat airport and the most recent 2½ years in the same role at Tel Aviv airport.
- The 43 year-old 767 tug driver had been employed by El Al for 10 years of which 8 had been in the ground equipment where he had been trained on all the company’s operational vehicles and was qualified for pushback but not airside R/T communication. The 24 year-old 767 wing walker was a former Israeli Air Force and El Al mechanic who had been employed by the ground handling company for 18 months as a tow crew supervisor.
- The 51 year-old 737 tug driver had been employed by the Laufer Group Ground Handling Division for 18 months and was qualified to tow all aircraft types (it was noted that although “not directly related to the accident”, he had resigned from this employment during the Investigation). The 25 year-old 737 wing walker had been employed by the same company for almost 7 months as a ramp supervisor/agent and qualified for small and narrow body aircraft.
The two involved aircraft were parked at adjacent gates near Terminal 3, the 767 at gate C9 and the 737 at gate C8 (see the illustration below). The 767 called the GND west frequency to request a departure clearance and was transferred by them to frequency 129.2 MHz for clearance. Whilst they were off the frequency, an arriving flight called and was cleared to taxi to gate C7 but hold before the intersection with taxiway M1, due to other traffic.
The accident site showing the initial positions of the 767(yellow) and the 737(purple) as well as gate numbers and starting positions (SP). North is at the top of the illustration. [Reproduced from the Official Report]
The 737 then called and requested pushback from gate C8 and the controller asked them to standby for clearance due to traffic due to pass behind. The inbound aircraft was then cleared to continue all the way to gate C7 which involved passing behind the 737 on taxiway ‘M’. The 767 crew returned to the frequency and requested pushback from gate C9 and after being initially instructed to standby for clearance, this was then followed about a minute later by clearance to push back to start-up position 37, facing east.
Whilst the 767 was being turned to face eastwards as it joined taxiway ‘M’ from M1 towards start-up position 37, the 737, which had been standing by pushback clearance for about five minutes, was given clearance to push back to start-up position 48, facing east with (significantly) the exchange not mentioning the aircraft gate number. Then, about 90 seconds after obtaining this clearance with the aircraft already approaching taxiway ‘M’, the controller changed its start-up position to position 47 facing west.
This meant that the 767 was being pushed back along taxiway M from the east at the same time as the 737 was being pushed back towards taxiway M in order to line up on it facing west before being towed forwards to start-up position 47. When the 767 had just 14 metres remaining to reach start-up position 37, the tails of the two aircraft collided and both stopped with their tails intertwined with the 767 horizontal stabiliser and elevator penetrated the 737’s vertical stabiliser and rudder.
About 45 seconds after the collision, a ‘Follow Me’ car arrived at the accident site. The 737 crew called GND to say that they had “stopped the pushback due to an aircraft behind them” and the controller asked for confirmation that the pushback could not be continued which was given. After two minutes had elapsed following the collision, no party had yet reported that a collision had occurred, even the driver of the ‘Follow Me’ car who was at the accident site. The controller “informed the 737 crew that the traffic to their east is not a factor, but if they had a problem, he would assign another start-up position” and the 767 crew called to say that they “were not yet at their assigned start up position and had stopped because of a tow truck problem”. The controller then instructed the 737 to stop which the crew acknowledged and added that they were waiting for further instructions. At last, about 3 minutes after the accident had occurred, the 767 crew called to say that according to their ground crew they had hit another aircraft but the controller did not respond until the 737 also reported the collision at which point he asked the 737 crew “if they wished to return to the gate”. The airport duty manager then consulted the airport manager on the telephone and it was decided not to declare an emergency and the passengers of both aircraft were eventually disembarked by mobile airstairs and transferred by buses to the terminal.
The accident was immediately reported to the AIAI Chief Investigator by El Al’s Director of Aircraft Maintenance and within a short time, investigators from his office arrived at the accident site and commenced surveying and documenting. Once this initial on-site work was complete, the Chief Investigator approved the separation and repositioning of the two aircraft to allow normal operations in the area to be resumed.
Why It Happened
The Investigation looked at similar pushback conflicts which had occurred at other airports and noted that, as in the collision under investigation, the towing crew(s) did not see the other aircraft and did not stop the pushback until the impact, in some cases even when a wing walker was present. In some cases, the GND controller also did not recognise the emerging conflict and in at least one case where they had done so, they had failed to prevent it. It was noted that “control of push-backs is challenging and complex even under excellent visibility conditions” and because the flight crew cannot see what is happening they do not have complete situational awareness whilst the pushback driver is relying on other elements involved in the process. The consequence of this was considered to be that “the factors affecting such cases beyond the specific circumstances of each accident are ground infrastructure, environmental conditions, operating and towing procedures, along with the competency of the tug crews”.
The Investigation’s analysis of its factual findings was divided into four parts which, in edited summary, were as follows:
Procedural and Technical Solutions
A cornerstone of aviation safety is cross/double checking. Significant parts of pushback crew procedures were not performed in the investigated event and are apparently not being complied with at all. Changing a start-up position during a pushback as occurred was not prohibited but it means the initial tug crew briefing is no longer necessarily valid and it effectively cannot be re-run. This means that this briefing should include reference to any possible changes so that the crew are prepared to execute them and recognise any associated hazards.
The Overall Accident Scenario
This was dominated by the mental fixation by the ground controller, beginning with his pushback clearance, throughout the process and even for several minutes after the collision has occurred. This fixation led to him issuing the conflicting clearance he gave to another aircraft not directly involved in the accident. During the five minutes the 737 was awaiting pushback clearance, he failed to maintain adequate situational awareness and continued to provide inaccurate and inefficient instructions and information. Both pushback crews operated in a way which did not comply with and in some instances actively violated airport procedures, company procedures and the requirement for pushback safety. Neither crew sought to verify that the pushback routes were clear of obstructions and assumed that the clearances they got from the controller via the flight crews were evidence that the routes were clear.
The origin of the accident was clearly the human factors performance of both the ground controller and the two push back crews placed in a context of the airport and operating company organisation and administration and the absence of effective regulatory oversight. A long history of errors in planning and execution which was not prevented by routine process oversight was apparent with many (but not all) barriers against unacceptable outcomes being ineffective. It was noted that “the final safety barrier of visual detection should have worked and should have prevented the accident”.
Infrastructure, procedures and examples of apron management
The complex structure of the airport, in particular the Terminal 3 area, is in need of a strategy which will effectively address its current situation and future development and can be translated into a comprehensive programme by ground services companies. Such a strategy should provide both a procedural and a technological solution and be informed by the successful management methods at other airports worldwide.
Technology to assist accident prevention during taxiing, towing and pushback
A number of aviation and other systems could be adapted for surveillance and control of aircraft and airside vehicular traffic on aprons at the airport by, for example:
- Fully leveraging the possibilities of the A-SMGCS system already operated for the taxiways and runways which have not yet been implemented in apron areas.
- A system similar to FLARM GPS system could be installed in aircraft towing vehicles, to warn when they are on a collision course.
- Installation of towing vehicle guidance systems would reduce driver workload, reduce risk of errors and free the drivers' attention for peripheral scanning.
- Installation of peripheral cameras on aircraft which would allow the flight crew to see the pushback route and might enable the flight crew to intervene in case of conflict - although such an installation would have to be certificated and may not be compatible with the common practice of starting engines during a pushback.
The Main Causes of the Accident were formally documented as:
"The event began with a wrong instruction in the pushback clearance for the 737 aircraft issued by the Ground Controller, a pushback which evolved into an accident under the prevailing local visibility and environmental conditions as a result of the pushback supervisors of the two pushed-back aircraft failing to perform safe pushbacks and detect hazards and obstacles on the pushback routes."
The Primary Contributing Factor to the Accident was formally documented as:
"The Ground Controller's error in giving the 737 aircraft a pushback clearance which was in inherent conflict with both the clearance he had previously given to the 767 aircraft and with the actual location of the 737. It is highly probable that the controller did not notice his error throughout the process due to fixation and partial situational awareness, acting as if the 737 had been parked on gate C7, when it was actually parked at and pushed back from gate C8."
A further 14 Other Contributing Factors to the Accident were, in summary, listed as follows:
- The Ground Controller did not construct a situational picture of the aircraft under his responsibility, by either technical or visual means even when this was possible. Even after the aircraft collided in an area which was clearly visible from the Tower, he did not see or understand the picture and continued to provide inappropriate instructions.
- The Ground Controller did not specify the parking gate upon giving the pushback clearance to the 737, especially when considering that his previous communication with that flight crew has occurred 5 minutes earlier when the clearance was requested. When the clearance was given without mentioning the gate, the pilots reading it back also refrained from mentioning the gate.
- The 737 towing crew did not perform risk management or conduct an adequate briefing before beginning the pushback. They should have anticipated the potential consequences, both at the beginning of the pushback and throughout its duration, of the location and direction of movement of the 767 which had been pushed back from the adjacent gate just before their pushback was authorised.
- The change of the 737 final pushback position by the Ground Controller whilst it was in progress did not anticipate the evolving conflict and thus made it harder for the towing crew to adjust to the new towing route. The towing crew did not stop briefly to assess the associated risks and to brief accordingly.
- The accident occurred in darkness and rain and the ramp area was wet and illuminated by lights which substantially reduced the visibility from the pushback tug cabins. Because of the rain, both tow escorts of the two aircraft joined the drivers inside the cabins, in violation of procedures and safety rules. The visibility conditions on the wet ramps led the drivers to focus on searching for the yellow lines on their routes and adversely affected the extent of their scanning of both the direction of pushback and the wider visible area.
- Beyond the Ground Controller's responsibility for setting the stage for a collision, most of the residual responsibility for the accident falls on the two towing crews, who had become used to relying solely on the controllers' instructions, believing that the controller can see everything and always retains complete situational awareness. As a result, they did not anticipate the possibility of encountering another aircraft in their area. Both the routine approach to the pushback task and the specific difficulties encountered that morning combined so that the pushback crews failed to act with sufficient regard to their responsibility to conduct safe pushbacks and detect each other in a timely manner.
- At the Ground Controller's position in the Tower and elsewhere at the airport there are insufficient technological means for presenting an up to date situational picture of aircraft positions and for warning of ground conflicts at the aprons. The A-SMGCS system did not provide a situational picture of Terminal 3 and its gate area and did not generate alarms regarding impending collisions in that part of the airport.
- The complexity and variations of managing the various Tower Controller positions necessitates controllers being highly professional, competent and fully familiar with any type of control position. In the current situation, let alone in the future when airport traffic will increase, the requirement for Tower Controllers to work in multiple positions could lead to reduced control effectiveness and to more mistakes.
- The complexity of the Terminal 3 layout and of the infrastructure on the parking ramps and routes to the taxiways and in particular the concourses, contributes to pushbacks being typically associated with long and complicated manoeuvres amongst obstacles, making it difficult to generate a situational picture and also difficult for tug drivers and their escorts to follow the authorised pushback route. The potential for error was increased significantly in darkness and with wet surfaces given that the crews were not equipped with any technological means of ground navigation or collision warning.
- There is routinely no effective means of communication between tug drivers and the walking escorts who are in communication with aircraft pilots during pushbacks - such communication is mainly achieved by shouting and hand signals which can require the escorts to be nearer than desirable to drivers and reduce their ability to monitor the route being taken.
- Tel Aviv airport has not utilised an integrated apron management approach. The airport's accelerated development and the significant growth of traffic volume had led to the addition of parking and start-up positions which were not accompanied by any revision to the concept of ground operations to ensure compatibility with the increasing scale of activity.
- The Tel Aviv airport management did not execute sufficient control over the airlines and ground services companies in respect of their responsibility for the professional competency of their employees in general and for their ability to perform safe aircraft pushbacks. Amongst other findings, it was discovered that the airport’s documented aircraft towing procedure is not internally consistent and includes a number of contradictions and conflicts as well as non-applicable procedures which are no longer being enforced. This situation has led to disrespect and to a wider culture of procedural non-compliance. (Note: Ground services companies are not obliged to have a SMS.)
- National and international regulation of ground services and ground traffic management is still insufficient despite an increasing awareness of the need to improve it.
- Pilots cannot monitor the pushback process from their flight decks without adequate means such as cameras.
A total of five Urgent Safety Recommendations were made in a Preliminary Report issued on 18 April 2019 and a further one (the sixth one below) followed after the issue of this Report:
- that the Israel Airport Authority/Ben Gurion should, until completion of the Investigation and issuance of final conclusions and recommendations, continue ground operations in accordance with the airport's Temporary Order for night and low visibility conditions.
- that the Israel Airport Authority/Ben Gurion should, in the formation of the concept and model for apron management procedures of both the airport and relevant companies, define the roles and responsibilities of towing crew members, the means of communication between the various participants, briefings, pushback route familiarity, wing walkers and an emphasis on the individual responsible for the overall safety of the process.
- that the Israel Airport Authority/Ben Gurion direct Ground Controllers to mention the relevant aircraft parking position when responding to pilots' clearance requests and if a pilot has not done the same, the controller must require that the location is confirmed.
- that the Israel Airport Authority/Ben Gurion assess all existing start-up positions in terms of utilisation, need and location and then cancel unused positions and ensure all retained or new positions are located where safe access is feasible. All parking gates’ entry and exit routes should be modified as necessary to reduce prerequisites and conflicts associated with their use.
- that the Israel Airport Authority/Ben Gurion consider transferring the responsibility for ramp management from the Tower Ground Control position to a dedicated Apron Control position or an equivalent alternative in order to create a more focused and professional control of aircraft movements on the ramps, from the movement planning stage until the stage of handover to the Ground Controller. Appropriate physical and procedural interfaces should be defined in support of such an arrangement and regulatory approval obtained.
- that the Israel CAA recommend to ICAO and IATA that they require controllers to mention the parking position in all relevant communications with the pilots of aircraft about to be pushed back, particularly if some time has elapsed since the pilot's request and the parking position was mentioned.
Six further Safety Recommendations were then made in the Final Report issued at the conclusion of the Investigation:
- that the Israel Airport Authority/Ben Gurion identify warning systems for preventing ground accidents, desirably systems which are operational worldwide, study them before procuring a suitable system.
- that the Israel Airport Authority/Ben Gurion establish a team which will examine the various topics involving apron management, will gather data about the various methods and will develop alternatives for review and determination of a concept for managing the aprons by an advanced and efficient model, applicable to Ben Gurion.
- that the Israel Airport Authority/Ben Gurion establish and lead an Apron Safety Team with participation of representatives from the Israeli airlines, the ground service providers and the office of the Chief Investigator. This team shall convene regularly (at least twice a year) for professional discussions and exchange of information regarding ongoing safety issues.
- that the Israel Airport Authority/Ben Gurion conduct a full and comprehensive program for managing safety, based on SMS principles including professional training, examinations and checking tasks and their accomplishment according to SMS methodology.
- that the Israel Airport Authority/Ben Gurion engage an appropriate organisation to conduct a comprehensive audit of the ground service companies at the airport.
- that the AIAI Chief Investigator suggests to manufacturers of large airliners that they consider the installation of aft-looking cameras at the wingtips and on the empennage and possibly also at other positions and display the images on flight deck screens to enable the pilots to see and understand what is going on and in extreme cases even be able to take over control of a push back to prevent a collision.
The Final Report presented in the definitive Hebrew language was completed on 25 June 2019 and an English language translation was subsequently released in May 2020.