Vehicle / B773, Singapore, 2013

Vehicle / B773, Singapore, 2013


On 3 October 2013, a vehicle entered an active runway without clearance after partial readback of a potentially confusing clearance was not challenged by the controller. A different controller then cleared a Boeing 777-300 to land without taking all available action to ensure that the runway was clear. The aircraft crew saw the vehicle near the edge of the runway after touchdown and manoeuvred their aircraft away from it, although the aircraft wing still passed over it. At the time of the incident, vehicles with clearance were permitted to cross red stop bars, a policy which has since been changed.

Event Details
Event Type
Flight Conditions
On Ground - Normal Visibility
Flight Details
Type of Flight
Public Transport (Passenger)
Intended Destination
Actual Destination
Take-off Commenced
Flight Airborne
Flight Completed
Phase of Flight
Inadequate ATC Procedures
ATC clearance error, ATC Unit Co-ordination, Inappropriate ATC Communication, Procedural non compliance
ATC error, Near Miss, Phraseology, Vehicle Incursion, Visual Response to Conflict, R/T Response to Conflict
Damage or injury
Non-aircraft damage
Non-occupant Casualties
Off Airport Landing
Causal Factor Group(s)
Air Traffic Management
Airport Operation
Safety Recommendation(s)
Aircraft Operation
Air Traffic Management
Investigation Type


On 3 October 2013, the crew of a Boeing 777-300 (9V-SWG) being operated by Singapore Airlines on a scheduled passenger flight in daylight and normal ground visibility, and which had just landed on Runway 20C at Singapore, saw a vehicle operating as 'Rover 39' ahead and were able to manoeuvre to avoid it although the aircraft left wing still passed over the moving vehicle.


An Investigation was carried out by the Singapore AAIB. The Investigation was not able to access recorded data from the Flight Data Recorder (FDR) and Cockpit Voice Recorder (CVR) of the aircraft involved because neither was de-activated after the aircraft had reached the gate contrary to the aircraft operator's requirements. Quick Access Recorder data was available. Advanced Surface Movement Guidance and Control System and ATC recordings were available.

It was established that the vehicle involved was being operated by a runway maintenance company contracted by the aerodrome operator and at the time had been occupied by a driver who held an appropriate permit which included R/T use and an assistant who did not hold one (and was not required to).

The First Officer was PF on the aircraft; both pilots reported not having seen the vehicle until after touch down when the aircraft was decelerating through approximately 100 knots. As a result of the sighting, well to the left of the runway centreline, the aircraft commander had taken control, substituted manual braking for autobrake to increase the deceleration rate and made a deviation to the right to ensure clearance so that only the outer left wing passed over the vehicle.

The vehicle, operating as 'Rover 39' was instructed by the controller "responsible for the movement of ground vehicles on Runway 02/20C" to proceed to a designated holding point and "to wait for three or four minutes". The TWR controller responsible for issuing aircraft clearances to land verified visually that the vehicle had arrived at the holding point. About a minute later, a third controller "in a supervisory role", who was unaware of the earlier clearance issued by the ground vehicle controller but aware that the vehicle needed access to the runway to remove a bird carcass, instructed the vehicle to "proceed for (the runway), prepare to enter (the runway) to pick up a bird carcass". This transmission was answered by the vehicle driver's assistant with the words "Roger Tower 39 runway (20) thank you" and this read back was not challenged. Following this clearance, the vehicle entered the runway, crossing the red stop bar in accordance with prevailing practice at the time which only required it to be switched off when a corresponding aircraft clearance was issued.

Eight seconds after the incursion occurred, the TWR controller issued a landing clearance to the 777. This controller advised that he had visually scanned the runway prior to issuing this clearance but that he had not checked the A-SMGCS. It was noted that the incursion would have generated both a visual and an aural warning of the incorrect presence of the vehicle on the runway. The Investigation noted that it was normal practice not to refer to the A-SMGCS display to help assess whether a runway was clear "when visibility is good" and that controllers were able to vary the volume at which audio warnings were broadcast through the associated speakers.

The Investigation concluded that "had there been a more systematic approach to utilise the full capabilities of the (A-SMGCS) system, the controllers might have been alerted by the aural and visual warnings of Rover 39’s runway incursion".

The A-SMGCS recording showing the Runway Incursion at the exact time the Boeing 777 was issued with a landing clearance (reproduced from the Official Report)

The Conclusion of the Investigation was that the direct cause of the incursion was "a miscommunication between (the supervisory) controller and (the vehicle occupants)". The latter had apparently heard only half of the controller's message and had interpreted the partial message as a clearance for their vehicle to enter the runway. Their incomplete read back was not challenged by the controller.

Safety Action taken as a result of the Investigation findings was noted to have included procedural safety improvements by both the ANSP and the aerodrome operator.

Three Safety Recommendations were made as a result of the Investigation as follows:

  • that The Air Navigation Service Provider adopt a more systematic approach to utilise the full capabilities of the A-SMGCS, even in good visibility conditions, to assist the controllers in performing their duties. [R-2014-001]
  • that The Airline Operator review its procedures to ensure that flight recorders are deactivated at the end of a flight following a significant occurrence. [R-2014-002]
  • that The Regulatory Authority ensure that the Singapore Air Operator Certificate holders have procedures implemented to meet the requirement in paragraph 37(4) of the Air Navigation Order regarding deactivation of flight recorders upon completion of a flight following an accident or a serious incident. [R-2014-003]

The Final Report was published on 25 March 2014.

Further Reading

SKYbrary Partners:

Safety knowledge contributed by: