The aircraft had just taken off when the fire warning for the centre (No. 2) engine activated. The crew carried out the engine fire drill, shut down the engine and commenced a right hand circuit for a landing back on runway 23. A distress phase was declared by the tower and emergency services alerted. On downwind, the crew advised that a fire was no longer evident.
The aircraft landed without further incident and the passengers were evacuated through the front doors. Subsequent investigation revealed that a weld in the bleed air "Y" duct for the de-icing system of the engine intake had suffered a fatigue failure. This allowed hot bleed air into the engine compartment which activated the fire warning system. This type of failure has occurred before and there are Service Bulletins addressing the problem.