ASN Wikibase Occurrence # 270861
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| Date: | Tuesday 2 March 2021 |
| Time: | 11:00 UTC |
| Type: |  Aerospatiale AS355F Ecureuil 2 |
| Owner/operator: | Helicopter and Pilot Services Ltd |
| Registration: | G-BOSN |
| MSN: | 5266 |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Minor |
| Location: | Hedsor House, Bourne End, Buckinghamshire -
 United Kingdom
|
| Phase: | Landing |
| Nature: | Passenger - Non-Scheduled/charter/Air Taxi |
| Departure airport: | Hedsor House, Bourne End, Buckinghamshire |
| Hedsor House, Bourne End, Buckinghamshire | |
| Confidence Rating: |  Information verified through data from accident investigation authorities |
AAIB investigation to Aerospatiale AS355F Ecureuil 2, G-BOSN: Engine fire due to exhaust clamp failure, Hedsor House, Bourne End, Buckinghamshire, 2 March 2021. The AAIB report into the incdent was published on 16 December 2021, and the following is the summary from it:
"Whilst hovering at 20 ft agl smoke was observed coming from the engine exhaust. A member of the operational team on the ground informed the pilot, who then landed immediately. A fire warning subsequently illuminated, and the pilot activated the fire extinguishing system. The fire was determined to have been caused by the loss of retention of the right engine inboard exhaust nozzle, which was released because of the failure of its securing clamp. The released nozzle had blocked the overboard exhaust outlet and allowed hot exhaust gases to impinge on the engine cowlings leading to local overheating.
The clamp failure was attributed to a combination of an incorrect locking washer being fitted during maintenance and elevated engine vibration which caused the clamp to loosen. A crack then propagated in low-load high-cycle fatigue until final rupture of the clamp.
The helicopter manufacturer is taking safety action to amend the Aircraft Maintenance Manual (AMM) highlighting the correct installation of the clamp.
=AAIB Conclusion=
The engine bay fire was caused by the loss of retention of the right engine inboard exhaust nozzle which, when released, blocked the overboard exhaust outlet and allowed exhaust gases to impinge on the engine cowlings.
Elevated engine vibration, in combination with the fitment of an incorrect locking washer on the exhaust nozzle clamp screw, was sufficient to allow the screw to back off and allow the clamp to vibrate. The vibration was sufficient to cause a fatigue crack to propagate, ultimately causing the clamp to fail and allow the release of the exhaust nozzle".
The crash location of Hedsor House is an Italianate-style mansion in the United Kingdom, located in Hedsor in Buckinghamshire. Perched overlooking the River Thames, a manor house at Hedsor can be dated back to 1166 when the estate was owned by the de Hedsor Family
Sources:
1. AAIB Report: https://assets.publishing.service.gov.uk/media/61b9d6d8d3bf7f055c4b7891/Airbus_Helicopters_AS355_F1_G-BOSN_01-22.pdf
2. https://www.flightradar24.com/data/aircraft/g-bosn
3. https://www.helis.com/database/cn/44302/
4. https://en.wikipedia.org/wiki/Hedsor_House
History of this aircraft
Other occurrences involving this aircraft
| 4 October 2023 | G-BOSN | Helicopter Services | 0 | Near Gunnersbury Park, Chiswick, West London | |
min |
Media:
Whilst hovering, smoke was observed from the engine exhaust of an Airbus Helicopters AS355 F1. After landing fire was observed, a fire warning illuminated and the pilot activated the fire extinguishing system, 2 March 2021. Safety action has been taken. https://t.co/cOQ6wRe9s6
— AAIB (@aaibgovuk) December 16, 2021
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 17-Dec-2021 17:04 | Dr. John Smith | Added |
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