What happened
On 19 November 2018, an AW109SP GrandNew, registration G-FRRN, was preparing for a private flight from London Heliport (Battersea) to Denham Airfield. Following a previous arrival at the heliport, the pilot moved to the right-hand seat to prepare for the return leg. Due to an upcoming scheduled closure of the heliport, the pilot aimed to depart quickly to avoid a 30-minute delay.
After receiving clearance to start, the pilot initiated the start sequence for the number one engine. As the rotors began to rotate, both the air traffic controller and the ground marshaller observed smoke emanating from the rotor head. The pilot immediately responded by shutting down the engine, fearing an engine fire. Upon inspecting the aircraft, the pilot discovered that the rotor brake was still engaged.
The investigation
The investigation established that the helicopter had arrived at the heliport under the command of a different pilot, who typically left the rotor brake engaged after shutdown. The pilot of the incident flight, however, usually disengaged the brake once the rotors stopped.
During the investigation, it was noted that the pilot performed the pre-start checks from memory rather than using a written checklist. Because the pilot was not expecting the brake to be engaged, and because the brake handle is partially obscured by engine control levers when viewed from the right-hand seat, the error went unnoticed. The aircraft lacks a mechanical or electronic interlock to prevent engine starts while the rotor brake is applied.
Findings
- The pilot performed pre-start checks from memory under time pressure to depart before the heliport closed.
- The rotor brake handle is difficult to observe from the right-hand seat due to obstruction by the engine control levers.
- The rotor brake was left in the on position, causing friction and smoke as the rotors began to turn.
- The AW109SP is not equipped with a system to prevent engine ignition while the rotor brake is engaged.
- Prompt action by the pilot, alerted by ground personnel, prevented significant damage to the aircraft.