An aircraft with more than 200 people on board was involved in a serious incident at Dublin Airport when its wing passed over a tractor lawnmower moving along the runway, with the driver oblivious to the landing jet.
The crew of the Canadian-registered Boeing 757-200, a Thomson Airways flight from the Sharm-el-Sheikh resort in Egypt spotted the lawnmower as the plane landed on May 29th last.
An initial report carried out by the Air Accident Investigation Unit (AAIU) of the Department of Transport was published today.
Just after the aircraft landed at 1.53am, the flight crew reported they had seen ground equipment "right at the runway lights at the edge-lighting here".
"The flight crew elaborated that what they had seen was a lone tractor lawnmower," the report said.
The incident investigator established that a "small ride-on grass mower was moving eastwards along RWY [runway] 10 a number of metres inside the runway-edge lighting at the time that the aircraft landed".
"The driver of the mower was unaware that an aircraft was landing and he did not see the aircraft before it passed his vehicle," the AAIU report said.
"It is probable that the starboard wing of the Boeing 757 passed over the ride-on mower during the landing roll."
Grass-cutting involving the tractor mower and other vehicles had been going on in the vicinity of the busy main runway. However, these operations were "stood down" by air traffic control at 1.47am due to "deteriorating visibility".
Air accident investigators were informed by the Irish Aviation Authority, which is responsible for air traffic control, that a new control system for all aircraft and other vehicles on the ground is currently being commissioned for use at Dublin airport.
It is expected to be "fully operational" by September of this year but is still only being tested. Test images recorded on the system on the night of the incident showed the tractor mower “clearly visible” and moving across the runway.
The test recording also showed that the system flashed a warning on its display indicating the "potential conflict" between the landing aircraft and the man on the mower.
A spokeswoman for the Irish Aviation Authority said it had been indicated to air traffic controllers on the night by those involved in the grass-cutting that the three vehicles involved in the operation were clear of the runway.
Because of the poor visibility, the controllers were not in a position to see the vehicles on the runway for themselves, she said.
“From the controller's perspective, all vehicles were reported clear, which is the only reason he would have given a landing clearance to that aircraft."
Other sources indicated, however, that those involved in the grass cutting - a routine operation - may not have been aware an aircraft landing was imminent.
In its safety recommendations, the AAIU said the Dublin Airport Authority should ensure that all vehicles required to operate on or near active runways should have airband VHF radios capable of picking up the ground control and control tower frequencies.
Such vehicles should also have flashing yellow beacons and transponders, the investigators said.
The DAA said it had already implemented these safety recommendations and that all vehicles on the ground now had beacons and the relevant radio equipment.
The authority said safety was of “paramount importance”.
“As well as cooperating with the Department of Transport inquiry, the DAA has carried out its own thorough investigation into the incident in question," a statement said.
“Thankfully incidents such as this are extremely rare at Dublin Airport and the DAA will continue to work closely with the Irish Aviation Authority and the Department of Transport to ensure that the highest safety standards are maintained at all times.”
A final report will be published in due course, the AAIU said.