Irish authorities are warning pilots of a potentially hazardous optical illusion at Dublin Airport whereby the obstacle lighting on top of a tall building could be mistaken for runway approach lights.

The illusion has emerged as a possible contributing factor behind a Flightline-operated Boeing MD-83's deviation from the approach path to runway 34 while attempting a night landing at Dublin on 16 August.

Ireland's Air Accident Investigation Unit (AAIU) has determined that lights on a building, around 52m (170ft) tall and situated in the Santry Cross district of Dublin south of the airport, could have triggered the error.


runway lights 

Building at Santry Cross

The building is located around 1.8km (1nm) to the left of the runway 34 centreline, and a similar distance ahead of the threshold. It has four red obstacle lights stationed on its roof.

AAIU investigators, in an interim statement on the incident, say that the aircraft - arriving from Lisbon with the first officer flying the jet - started to deviate to the left about 5nm from touchdown.

 runway lights

Building at Santry Cross under night conditions

"The aircraft continued to descend below the minimum descent altitude without proper visual identification of the runway in use," says the interim statement.

Air traffic controllers instructed the MD-83 to make a right turn and climb to a safe altitude before directing the aircraft to make a new approach to runway 16. The jet landed without further incident.

"It was found that lighting from a 16-storey building situated at Santry Cross appeared, at night, to resemble the red and white lights of a runway approach-light system," states the AAIU.

Investigators subsequently recommended that the Irish Aviation Authority should warn pilots and operators of the possible risk of confusion, and "review the suitability" of obstacle lighting such as that installed on the building in question.

Earlier this month the authority issued an operations notice on the matter which requires that, when runway 34 is in operation, all automatic terminal information service broadcasts will warn of the lights' potential to disorientate flight crews.

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Source: Flight International