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ASN Wikibase Occurrence # 187659
Last updated: 7 August 2020
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Date:10-JUL-1994
Time:07:05
Type:Silhouette image of generic H500 model; specific model in this crash may look slightly different
Hughes 369HE
Owner/operator:Helisport Ltd
Registration: G-HSAA
C/n / msn: 1090203S
Fatalities:Fatalities: 0 / Occupants: 3
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Location:Old Stratford, Northamptonshire -   United Kingdom
Phase: En route
Nature:Private
Departure airport:Redhill Aerodrome, Redhill, Surrey (EGKR)
Destination airport:Silverstone Motor Racing Circuit, Towcester, Northamptonshire
Narrative:
Written off (damaged beyond repair) 10-7-1994 when crashed at Old Stratford, Northamptonshire. According to the following extract from the official AAIB report into the accident:

"Towards the end of a flight from Redhill to the Silverstone motor racing circuit, whilst in the cruise at 1,000 feet agl., the helicopter started to yaw rapidly from side to side. The pilot initially suspected a tail rotor problem and lowered the collective lever. However, the helicopter then pitched nose-down, and he realized that the engine power was fluctuating.

The pilot lowered the collective lever fully and started to look for a suitable landing area. There was a lot of air traffic locally, due to the presence of a helicopter feeder site supplying the nearby racing circuit, and he was therefore constrained into conducting a downwind landing in a field straight ahead in order to remain clear of traffic.

A run-on landing was made, but during the final stages the right skid entered a shallow depression which turned the helicopter through 90 degrees. This caused the main rotor to completely sever the tail boom. However, the helicopter remained upright and the occupants, who were uninjured, were able to evacuate via the doors.

During the subsequent investigation the only component from the helicopter's fuel system that appeared to be completely non-functional was the double check valve (DCV). This is an 'on condition' item located in the pneumatic line between the PT governor and the FCU. It is connected to a 6 cubic inch accumulator (essentially just an empty chamber) and the purpose of the assembly is to modify the output pressure signal of the PT governor to the FCU. This is intended to damp out engine RPM instability that could result from the PT governor attempting to compensate for the minor RPM excursions arising from power train torsional transients which occur in flight.

A rig test showed that theassociated valves were apparently seized; thus the unit probably was not capable of performing its damping function, with an attendant risk of engine RPM instability, or 'hunting', which in turn could have resulted in the helicopter experiencing 'twitching' in yaw. The engine manufacturer has however indicated that an inoperative DCV is 'unlikely to have a violent effect on engine operation'.

Damage sustained to airframe: Per the AAIB report "severe damage; tail plane chopped by main rotors". as a result, the registration G-HSAA was cancelled by the CAA on 23-2-1995 as "Permanently withdrawn from use"

Sources:

1. AAIB: https://assets.digital.cabinet-office.gov.uk/media/5422fc26ed915d1374000869/Hughes_369HE__G-HSAA_12-94.pdf
2. CAA: https://siteapps.caa.co.uk/g-info/rk=HSAA
3. http://www.griffin-helicopters.co.uk/accidentdetails.aspx?accidentkey=14734


Revision history:

Date/timeContributorUpdates
26-May-2016 22:12 Dr.John Smith Added

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