What happened
On October 20, 2020, a Sikorsky S-92A, registration LN-OMI, operated by Bristow Norway AS, was performing a flight from Stavanger Airport Sola to the Ekofisk Kilo oil and gas platform. Approximately one hour into the mission, the crew received a fire warning for engine 1.
Following emergency protocols, the crew transitioned to single-engine operation and shut down the affected engine. To combat the perceived threat, the crew deployed both available fire extinguishing bottles. Despite these actions, the fire warning persisted. The crew noted a lack of secondary indicators, such as smoke, flames on tail-mounted cameras, or erratic engine parameters, leading them to believe the alert was erroneous.
After several minutes of continuous warning, the commander issued a Mayday call to air traffic control, requesting a descent to 1,000 feet and a diversion to the Ekofisk Lima platform. After the warning signal eventually ceased, the crew restarted engine 1 and landed safely on the platform. A subsequent inspection of the engine compartment confirmed that no fire had occurred.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the flight data, cockpit voice recordings, and the aircraft's maintenance history. The investigation focused on why the fire warning remained active despite the deployment of extinguishing agents and the lack of physical evidence of fire. Investigators also looked into the frequency of similar incidents involving this helicopter type and the adequacy of the crew's training and checklists for handling persistent false alarms.
Findings
- The crew was aware of a high frequency of intermittent false fire warnings on the S-92A model.
- The specific warning in this incident was unusual because it remained constant for an extended period, unlike typical intermittent alerts.
- The crew lacked secondary indications of an actual fire, such as visible smoke or flames on external cameras.
- The deployment of both fire extinguishing bottles left the crew with no remaining extinguishing agents for the engine or the APU.
- The decision to continue to the platform rather than returning to land was driven by the proximity of the platform compared to the longer flight time back to Sola.
- The investigation noted that the crew had not received specific training for managing continuous false warnings, forcing them to rely on their own judgment and existing checklists.