What happened
On 10 August 2017, an accident occurred at Parham Airfield in West Sussex involving a HPH Glasflugel 304 eS glider, registration G-GSGS. The incident prompted an investigation into the safety of Front Electric Sustainer (FES) systems used in various sailplane and microlight models.
The investigation
The investigation focused on the potential for fire or other hazardous conditions within the battery compartments of aircraft equipped with FES technology. The AAIB examined the risks associated with the battery packs used in several different aircraft types, including those operating under EASA Restricted Type Certificates and Permits to Fly. The inquiry looked into the lack of pilot notification regarding thermal or chemical hazards within the propulsion system's battery housing.
Findings
It was determined that aircraft equipped with FES systems lacked an adequate warning system to alert the pilot to fire or other hazards within the battery compartment. This deficiency was identified as a critical safety gap for several manufacturers and aircraft models.
Safety action
Following the investigation, several safety recommendations were issued:
- A recommendation was made to EASA to require all powered sailplanes with FES systems to be equipped with a warning system for battery compartment hazards. In response, an Emergency Airworthiness Directive (EAD) was published, requiring the removal of battery packs or approved modifications to the battery design and software.
- A recommendation was issued to Alisport Srl to modify the Silent 2 Electro microlight to include a fire warning system. The manufacturer has since developed a fire warning system and new battery cases.
- A recommendation was issued to Albastar d.o.o. regarding the AS13.5m FES microlight to incorporate similar fire detection capabilities.