Early in the climb out ATC informed the crew that their aircraft had left debris on the runway. The flight crew was later advised by the cabin crew that panels were missing from the engines. As the fan cowl doors detached they caused secondary damage to the airframe and aircraft systems. The symptoms seen by the flight crew included: engine thrust control degradation, the loss of the yellow hydraulic system, and a significant fuel leak. After the loss of the yellow hydraulic system the crew declared a PAN, with the intention of returning to Heathrow once they had fully assessed the situation. ATC provided radar vectors for the ILS to Runway 27R.  

During the approach to land, an external fire developed on the right engine. An engine fire warning on the flight deck prompted the crew to declare a MAYDAY. Although both engine fire extinguisher bottles were discharged and the right engine was shut down, the fire was not completely extinguished. The left engine continued to perform normally throughout the flight. The aircraft landed safely and was brought to a stop on Runway 27R at Heathrow. The airport fire service attended and quickly extinguished a small fire on the right engine. The passengers and crew evacuated via the escape slides on the left side of the aircraft, without injury.  

Examination of the aircraft revealed that the inboard and outboard fan cowl doors from both engines had detached. Remnants of the doors were recovered from Runway 27L. The detached fan cowl doors had struck and damaged the inboard leading edge slats, left and right fuselage skin close to the wing roots, over wing fairings, inboard flaps and left belly fairing. In addition, the right engine outboard fan cowl had struck the right wing leading edge at the outboard end of Slat 3, damaging this slat and the inboard end of Slat 4. The outboard flap track fairing on the right wing was punctured and the left horizontal stabilizer leading edge and lower skin were damaged. Debris had also struck the left main landing gear, damaging the leading edge of the landing gear door and a hydraulic brake pipe. 

The right main landing gear outer tire was damaged during the landing and had fully deflated. The right engine was extensively fire damaged. The damage was concentrated in the left and right thrust reverser ‘C’ ducts and common nozzle assembly. A low pressure fuel pipe was punctured by the remnant of the inboard fan cowl that remained attached to engine. The source of ignition that led to the in-flight fire is still under investigation. 

The engine fan cowling is composed of two semi-circular composite fan cowl doors. The doors are fastened by four latches attached to the lower edge of the right door. Each latch operates a hook that engages with an eye bolt on the lower edge of the left door. Due to the low ground clearance of the nacelle, fastening the fan cowl door latches usually requires maintenance personnel to lie on the ground to access the latches. The fan cowl door latches are difficult to see unless crouched down so that the bottom of the engine is clearly visible. 

The fan cowl doors can be propped open by two stays mounted on the inside of each door, to allow access for servicing. When the doors are lowered from the propped open position, a ‘hold open’ device on the bottom of the fixed engine inlet cowl prevents the fan cowl doors from closing fully under gravity. In this condition the fan cowl doors stand slightly proud of the nacelle to provide a visual cue that the doors are not latched. AAIB Safety Recommended Airbus formally notifies operators of A320-family aircraft of the fan cowl door loss event on A319 G-EUOE on May 24, 2013, and reiterates the importance of verifying that the fan cowl doors are latched prior to flight by visually checking the position of the latches.