What happened
On 23 May 2005, a British Aerospace ATP, registration G-JEMC, operated by Emerald Airways, was performing a flight near the Isle of Man. Shortly after departure, a seal within the hydraulic retraction line for the forward left door airstairs failed. Due to a jammed airstairs UP switch and a stuck door safety microswitch, the line remained pressurized, allowing hydraulic fluid to escape as a fine mist into the passenger cabin.
The cabin crew, perceiving the mist as smoke, alerted the flight crew. To minimize exposure to the substance, the crew moved passengers toward the rear of the aircraft. This redistribution caused the aircraft's centre of gravity (CG) to shift to an estimated 30% to 31% MAC, exceeding the operator's specified aft limit of 29%.
Following the hydraulic low-level warning, the commander declared an emergency and returned to Ronaldsway Airport. During the approach, the crew received an EGPWS alert regarding an incorrect flap setting, which they subsequently corrected. Upon landing, the aircraft experienced nosewheel steering difficulties, forcing the commander to stop the aircraft short of the terminal buildings. One passenger with asthma required hospital treatment but was later discharged.
The investigation
The AAIB investigation examined the mechanical failure of the hydraulic seal and the operational responses of the crew. Investigators found that the hydraulic leak was caused by a combination of a stuck microswitch and a jammed selection switch, which prevented the de-pressurization of the airstairs line. The investigation also reviewed the crew's adherence to Standard Operating Procedures (SOPs) and the impact of passenger movement on the aircraft's stability.
Findings
- The primary cause of the hydraulic leak was a combination of a stuck door safety microswitch plunger and a jammed-on airstairs UP switch.
- The movement of passengers to the rear of the cabin caused the aircraft's CG to move beyond the permitted aft limit.
- The flight crew did not follow established checklists or SOPs regarding smoke in the cabin, the use of emergency radiotelephony phrases, or the management of the hydraulic low-level condition.
- The crew did not verify the new CG position or address the implications of the passenger redistribution.
- The commander did not follow the requirement to minimize taxiing after landing, which increased the occupants' exposure to the hydraulic mist and potential fire risks.
Safety action
Following the incident, the CAA suspended the operator's Air Operator's Certificate on 4 May 2006. The company subsequently ceased trading.