What happened
On 23 May 2005, a British Aerospace ATP, registration G-JEMC, operated by Emerald Airways, was performing a scheduled flight from the Isle of Man (Ronaldsway) to Liverpool. Shortly after departure, a mechanical failure occurred within the aircraft's airstairs operating mechanism. A seal in the retraction line failed, causing hydraulic fluid to escape as a fine mist into the forward section of the passenger cabin.
Because the cabin crew perceived this mist as smoke, they initiated emergency procedures by moving the 33 passengers from the forward section toward the rear of the aircraft. This mass redistribution of weight caused the aircraft's centre of gravity to shift beyond the operator's permitted aft limit. The flight crew declared an emergency and returned to Ronaldsway Airport. During the approach, the crew received an alert from the EGPWS regarding an incorrect flap setting. Upon landing, the aircraft experienced nosewheel steering difficulties, forcing the commander to stop the aircraft before reaching the terminal. One passenger required medical attention at a local hospital due to asthma but was later released.
The investigation
The AAIB investigation focused on the technical cause of the hydraulic leak and the subsequent crew responses. Investigators examined the airstairs UP switch and the door safety microswitch, finding that both had malfunctioned. Specifically, a jammed switch and a stuck microswitch prevented the system from de-pressurising the line in flight. The investigation also reviewed the aircraft's centre of gravity calculations and the crew's adherence to standard operating procedures during the emergency.
Findings
- A faulty door safety microswitch and a jammed airstairs switch kept hydraulic pressure applied to the actuators during flight.
- The failure of a hydraulic seal resulted in the discharge of hydraulic fluid mist into the cabin.
- The movement of passengers to the rear of the aircraft to avoid the mist caused the centre of gravity to exceed the aft limit.
- The flight crew did not strictly adhere to standard operating procedures and checklists during the incident.
- There were no requirements for cabin crew to seek flight deck approval before redistributing passengers, though the commander was notified in this instance.