History of the Flight
The flight, a charter from Biggin Hill to Leeds Bradford Airport, was uneventful until after landing on Runway 14. While decelerating below 70 kt, the master caution sounded with an inverter 1 fault, followed by a master warning for electrical smoke. The co-pilot reported smelling smoke, and the commander agreed. The aircraft was brought to a stop on the runway with the parking brake set. ATC was informed, and the fire service was requested.
The commander contacted the senior cabin crew member, who initially reported no smoke in the cabin. After walking through the cabin, he confirmed the smell. There was no visible smoke. The fire commander reported no external smoke or hotspots. The smell began to dissipate. The commander decided to initiate a rapid disembarkation on the runway to avoid panic, rather than taxiing to a stand. Both propellers were feathered, the propeller brake engaged, and the left engine was shut down. The right engine was kept running in Hotel mode to power cabin lights due to darkness. Passengers and cabin crew disembarked onto the runway and were transported to the airport. The pilots remained on board for towing. No injuries were reported.
Aircraft Information
The aircraft, G-CMFI, is an ATR 72-212 A. Its electrical system includes two static inverters that provide constant frequency AC power. Inverter 1 normally supplies AC bus 1 and standby bus. In case of failure, the standby bus is supplied by inverter 2. The Hotel mode allows the right engine to operate as an auxiliary power unit with the propeller held stationary by a brake, subject to limitations including tailwind less than 10 kt and a flight crew member remaining on the flight deck.
Source of Fumes
The operator identified the source as static inverter number 1, which had 6,617 flight hours, below its guaranteed mean time between unexpected removal of 15,000 hours. Further investigation revealed that the inverter model (1-002-0102-2173) had experienced similar events. A Vendor Service Bulletin (VSB) had been issued to modify specific serial numbers by replacing capacitors, but the operator was unaware of it. Both inverters on G-CMFI were affected. The manufacturer reported 42 prior events of smoke or smell from static inverter failures. The operator replaced inverter 2 with a unit not affected by the VSB and updated maintenance procedures to treat Airworthiness Operator Messages like service bulletins.
Operational Procedures
Emergency procedures in the Operations Manual describe planned and unplanned evacuations. A rapid disembarkation uses normal exits only and is conducted when a full evacuation is not warranted. After the event, the operator planned to update guidance for rapid disembarkations to clarify the distinction between evacuation and rapid disembarkation.
Meteorological and Aerodrome Information
Weather at Leeds Bradford Airport was clear skies, light wind from the southeast at 8 kt, temperature 13°C. The concrete runway 14/32 is 2,250 m long with a landing distance available of 1,801 m.