Occurrence
On 27 September 2017, at 17:26 UTC, an Airbus A320-216, registration EC-LVQ, was involved in a serious incident during a pushback and pull forward manoeuvre at Dublin Airport (EIDW). The aircraft, operated by a commercial air transport operator, was being prepared for departure to Madrid Barajas Airport (LEMD), Spain. The pushback crew consisted of a tractor driver, a headset operator, and an observer (wing-walker).
After obtaining Air Traffic Control approval to push and start to Tug Release Point November (TRP 'N'), the aircraft was pushed off Stand 318R at 17:21 hrs. The manoeuvre involved an initial pushback followed by a pull forward onto Apron Taxiway 5, to TRP 'N'.
During the pull forward, the flight crew received clearance from the headset operator to start the starboard engine. As the tractor turned right to align the aircraft onto the taxiway, the aircraft's nose began to overtake the tractor. The headset operator immediately instructed the flight crew to shut down the starboard engine. The tractor driver attempted to stop, but the tractor was pulled and rotated as the aircraft continued forward. The aircraft then turned slightly right and came to rest with the tractor wedged against the right-hand side of the starboard engine cowling. The aircraft's brakes were set after stopping.
Aircraft and Damage
The aircraft, an Airbus A320-216 with two CFM56-5B6/3 engines and serial number 5590 (year of manufacture 2012), had a mass of 67,927 kg during the pushback. The starboard engine cowling sustained substantial damage; no other damage to the aircraft or engines was reported. The tractor sustained no damage. The shear-pin in the head of the towbar was found to have sheared, leaving just the head of the pin in place.
Personnel and Conditions
The commander, aged 32, held an ATPL issued by AESA and had 6,082 total flying hours (5,882 on type). There were 6 crew and 179 passengers on board; no injuries were reported. The pushback was performed by a ground handling company. Their manual (dated 1 May 2017) prohibited towing with engine(s) running. At the time, the ramp was wet from rain, with no evidence of surface contamination other than water. A survey indicated a downhill slope of approximately 1% over the area where the event occurred.
The tractor was a 14,000 kg, four-wheel-steerable vehicle, coupled to a towbar with an appropriate shear-pin. The aircraft was within IATA Category 2 (less than 150,000 kg), requiring a minimum tractor weight of 12,000 kg. During the pull forward, the tractor was driven in reverse.
Engine Data
Flight data indicated the starboard engine was being started during the pull forward. Maximum rotation speeds recorded were 54.9% N2 and 16.5% N1, at which point the start was aborted. The engine manufacturer stated that ground idle conditions are approximately N2 60% and N1 19%, producing thrust below 800 lbf; for the peak values recorded, actual thrust was expected to be less than 700 pounds.
Visibility
Examination of A320 cockpit visibility cut-off angles indicated it was unlikely the flight crew would have seen the event or the impact. With nose wheel steering de-activated, the maximum steering angle is ±95 degrees. Visual markings on the aircraft warn pushback operators when the maximum steering angle is reached.