Description

On 10 January 2008, an Airbus A380 was damaged during push back at Singapore Changi International airport when the aircraft right wing undercarriage became stuck in soft ground adjacent to the taxiway.

Synopsis

"The Airbus A380 was scheduled for a passenger flight to Sydney on 10 January 2008. At 8.46 p.m. the aircraft was pushed back from Bay A4 at Singapore Changi Airport by a Schopf air tug. It was to be positioned on Taxiway WA facing south.

However, during the pushback, the right hand wing landing gear departed from the paved taxiway and went over a concrete airfield lighting transformer box onto the grass verge adjacent to Taxiway WA. Part of the right hand body landing gear also left the paved taxiway. When the air tug driver realised that the aircraft had gone onto the unpaved ground, he tried to pull it back onto the taxiway. During the pulling, the fuse pins attaching the towing pin to the nose gear of the aircraft sheared."

Cause

The Air Accident Investigation Bureau of Singapore included the following findings in the report:

• "Owing to the orientation of Bay A4 with respect to Twy WA and the space restriction, pushing an A380 from the bay to face south on Twy WA required skill and good judgment in maneuvering the aircraft along the yellow lead-in line.
• The lighting of Bay A4 area was adequate to enable the yellow lead-in lines to be seen from the bay up to where the two curved yellow lead-in lines intersect.
• The taxiway centreline at Bay A4 area was not reflective and was difficult to see.
• The air tug driver failed to exercise proper judgment in adhering to the lead-in line when pushing back an A380 aircraft from Bay A4.
• The air tug driver did not stop the pushback to assess the situation when he had deviated from the lead-in line and could not see the taxiway centreline.
• The air tug driver’s company had assigned a driver who was pushing out an A380 aircraft for the first time.
• The head set man was not assertive enough to stop the air tug driver when he noticed the aircraft had deviated from the lead-in line."

The following facts were categorized as ‘other issues’:

• "The shear bolts on the tow bars were at much lower torque values than that stipulated.
• The shear bolt distance on the tow bar was wider than that specified by the aircraft manufacturer. This could have affected the shearing characteristics of the shear bolts.
• The torque wrenches were calibrated in imperial units and there were no conversion tables for their conversion to metric units for use by the equipment maintenance personnel.
• The equipment maintenance personnel apparently lacked knowledge of proper maintenance of tow bars.
• The elbow connector on the air tug was removed without prior permission of the AAIB investigators. The towing pin in the tow bar clamp had been disturbed."

Recommendations

The following recommendations were made as a result of the investigation:

• "The air tug driver’s company review the training of its air tug drivers to handle new aircraft types. The air tug driver’s company review the training of its maintenance personnel on proper maintenance of tow bars.
• The aerodrome operator consider painting the taxiway centrelines with reflective material in order to enhance their conspicuousness and to avoid such incident recurring on other taxiways."

Related Articles

• Ground Operations
• Aircraft Towing
• Pushback
• Wing Tip Clearance Hazard

Further Reading

• AIB/AAI/CAS.046 - Final Report, Air Accident Investigation Bureau of Singapore