What happened
An investigation was launched by the AAIU into a serious incident involving a Eurocopter AS 350 helicopter, registered as G-JESI. The investigation sought to determine the circumstances surrounding the event and evaluate the safety of the procedures in use at the time of the occurrence.
The investigation
As the investigation progressed, investigators discovered that a standard refuelling bowser was being utilized for the practice of "hot" refuelling. This procedure involves adding fuel to turbine-engined helicopters while the engines remain operational.
Technical analysis revealed that the bowser in use was equipped with a standard nozzle intended only for use when engines are shut down. Unlike specialized equipment, this standard nozzle allows fuel to displace vapor within the tank, forcing that vapor out through the filling point. Because the filling point on this aircraft type is positioned high on the fuselage near the engine, the escaping flammable vapor is at high risk of ignition from hot engine exhaust or engine ingestion.
Findings
- The use of a standard refuelling nozzle during hot refuelling creates a significant fire hazard.
- The lack of a vapor-sealing nozzle allows flammable vapors to exit near the engine area.
- Specialized nozzles are designed with a seal that prevents vapor from escaping the filling point, instead directing it through a fuel tank vent located safely away from the engine heat sources.
Safety action
In response to these findings, the AAIU issued an interim safety recommendation (SR 15 of 2007). The recommendation calls for the Irish Aviation Authority (IAA) to release an Aeronautical Information Circular (AIC) to warn operators of the hazards associated with standard nozzles. This notice should also prohibit the hot refuelling of helicopters using any bowser that lacks a nozzle specifically designed with a vapor seal.