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ASN Wikibase Occurrence # 199952
Last updated: 23 February 2020
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Time:11:21 UTC
Type:Glasflügel 304 eS
Registration: G-GSGS
C/n / msn: 059-MS
Fatalities:Fatalities: 0 / Occupants: 1
Other fatalities:0
Aircraft damage: Minor
Location:Parham Airfield, Pulborough Road, Cootham, Storrington, West Sussex -   United Kingdom
Phase: Landing
Departure airport:Parham Airfield, Storrington, West Sussex
Destination airport:Parham Airfield, Storrignton, West Sussex
Investigating agency: AAIB
The pilot had fully charged both Front Electric Sustainer (FES) batteries of his Glasflügel 304 eS (a powered sailplane with electrical motor) on 4 August 2017, after which they were disconnected from the chargers for storage. He installed them in the glider on the morning of 10 August, with the intention of flying the glider that afternoon. He initiated the FES battery self-checking procedure before conducting a daily inspection of the glider, after which the self-checking procedure had completed with no faults indicated on the FES Control Unit (FCU). He then fitted the FES battery compartment cover and applied tape around the edges of the cover.

The pilot conducted a ground run of the FES propeller, which operated normally. He then switched the Power Switch OFF, and also turned the FCU OFF, which was contrary to his normal practice of leaving the FCU switched ON.
The pilot launched from Parham Airfield by aerotow at 1021 hrs and flew in ridge lift for a period of 38 minutes before encountering a rain shower. He decided to use the FES propulsion system and turned the Power Switch ON. He then noticed that the FCU was switched OFF, so he switched the FCU ON without moving the Power Switch position.

After waiting a few seconds for the FCU green LEDs to show that the FES propulsion system was available, he operated the FES motor which responded normally and operated for 4 minutes. The pilot did not recall observing any fault messages on the FCU during the motor operation.

After stopping the FES motor the pilot noticed that the propeller did not realign itself correctly against the nose of the glider. The pilot had experienced this problem previously and did not consider it to be a significant issue, so he did not attempt to realign the propeller. He switched the Power Switch OFF, leaving the FCU switched ON and continued in soaring flight for a further 1 hour 15 minutes before positioning the glider to land on grass runway 04 at Parham Airfield. The circuit was flown normally to a smooth touchdown, however at the moment of touchdown the pilot heard an unexpected noise.

As the glider slowed during the ground run, the pilot smelled burning and the cockpit filled with smoke that was moving forwards from behind the pilot's head. The pilot did not report observing any warning messages or illuminated LEDs on the FCU, although his attention was drawn outside the cockpit during landing. He vacated the cockpit normally, without injury, and observed that the FES battery compartment cover was missing and that smoke, followed shortly by flames, was coming from the battery compartment. The airfield fire truck arrived promptly and an initial attempt was made to extinguish the fire using a CO2 gaseous extinguisher, but this proved unsuccessful. Aqueous film-forming foam (AFFF) was then sprayed into the FES battery compartment and the fire was extinguished.

The FES battery compartment cover was found close to the glider's touchdown point. The cover's rear carbon fibre catch was fractured, consistent with a vertical load acting on the inside of the cover. The cover did not exhibit any overheating damage.

On September 25, three safety recommendations were issued as the AAIB was concerned that existing FES battery installations did not provide sufficient warning to a pilot of a fire or other hazardous condition (such as high pressure) occurring within the FES battery compartment.

13-sep-2018 AAIB Final report:

During a normal touchdown following an uneventful flight, the glider’s forward FES lithiumpolymer battery ignited due to an electrical arcing event. The pilot was unaware that theglider was on fire and the battery continued to burn, generating smoke and fumes which entered the cockpit during the latter stages of the landing roll. The pilot was not injured and the fire was extinguished using foam retardant, although the glider’s fuselage battery boxand surrounding structure was extensively fire-damaged.

A detailed examination of the forward FES battery did not determine the cause of the battery fire. The G-GSGS battery fire was the second of three such FES battery fires that have occurred to date.
A survey of other FES batteries from the in-service fleet revealed the presence of metallic debris in a significant proportion of those batteries examined. Vibration testing conducted by the AAIB showed that the presence of metallic debris can cause battery cell pouch fretting although this was not sufficiently severe to cause an internal short circuit and electrical arcing As a result of this investigation the sailplane manufacturer and FES system manufacturer have implemented a number of safety actions intended to prevent recurrence, or to mitigate
the effects of a battery fire should such a fire occur.

See complete report below ->


4. Final report AAIB :

Safety recommendations:

Safety recommendation 2017-018 issued 25 September 2017 by AAIB to EASA
Safety recommendation 2017-019 issued 25 September 2017 by AAIB to Alisport
Safety recommendation 2017-020 issued 25 September 2017 by AAIB to Albastar

Accident investigation:
Investigating agency: AAIB
Status: Investigation completed
Duration: 1 year 1 month
Download report: Final report

Revision history:

25-Sep-2017 19:54 harro Added
10-Nov-2017 21:53 Dr. John Smith Updated [Location, Departure airport, Destination airport, Source, Narrative]
13-Sep-2018 17:11 Iceman 29 Updated [Source, Embed code, Narrative]
13-Sep-2018 19:09 harro Updated [Time, Embed code, Accident report, ]

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