What aircraft was involved and where did it happen?

The accident on null involved a aircraft, registration N449J, at IE.

What was the probable cause of the accident?

The primary cause was the helicopter pilot's failure to adhere to the conditional ATC clearance, compounded by the difficulty in identifying the small, dark-colored Learjet in low-light conditions.

Near Collision at Dublin Airport Avoided by Evasive Maneuver

A helicopter crossing an active runway at Dublin Airport narrowly avoided a mid-air collision with a departing Learjet after a misunderstanding of ATC instructions.

What happened

In the early morning hours of 17 December 2007, a serious incident occurred at Dublin Airport involving an Agusta Westland A109 helicopter, registration N449J, and a Learjet 31A, registration EI-MAX. During a period of low light following sunrise, the helicopter was hovering near the control tower while awaiting clearance to cross the active runway 10. At the same time, the Learjet was cleared for takeoff to proceed to Zurich.

After the Learjet became airborne, the helicopter pilot crossed the runway ahead of the departing jet. The commander of the EI-MAX observed the helicopter crossing the centerline directly in his flight path. To prevent a collision, the pilot immediately took control of the aircraft, pushing the nose down and banking left at an altitude of approximately 200 feet. This maneuver successfully prevented a mid-air collision and avoided contact with the ground.

The investigation

The investigation focused on the communication between Air Traffic Control (ATC) and the helicopter pilot. Records revealed that the controller had issued a conditional clearance, instructing the helicopter to cross the runway behind the "rolling traffic." The helicopter pilot confirmed he had the aircraft in sight; however, he later admitted to misidentifying the target. The pilot believed the controller was referring to a Boeing 737 taxiing toward the runway, rather than the departing Learjet.

Investigators also examined the visibility of the aircraft. The Learjet 31A was a small, dark grey aircraft, which made it difficult to distinguish against the grey runway surface in the low light of dawn. While the pilot of the helicopter failed to verify the specific aircraft type before crossing, the investigation noted that the lack of visual contrast was a significant factor.

Findings

The helicopter pilot failed to comply with the conditional clearance issued by ATC.
The pilot of the helicopter misidentified the departing aircraft due to a misunderstanding of the controller's instructions.
The dark grey color and small size of the Learjet contributed to the difficulty in identifying the aircraft during the low-light conditions.
The pilot of the EI-MAX demonstrated excellent airmanship by executing immediate evasive action.

Safety action

Following the incident, ATC procedures at Dublin Airport were updated. To prevent similar occurrences, controllers are no longer permitted to issue conditional clearances to helicopters for crossing active runways. Helicopters must now be held in a position clear of the runway and are only cleared to cross once the runway strip is confirmed to be unoccupied.