The Sikorsky S-61N is a twin-engine medium utility helicopter with a sealed hull for amphibious operations
that can accommodate a basic crew of two and up to 26 passengers. The Sikorsky S-61N is based on the military
Sikorsky SH-3A/S61B Sea King series originally developed in the late 1950s for all-weather operations. The Sikorsky S-61B
prototype flew on 11 March 1959 and the type entered service with the U.S. Navy as the SH-3A Sea King in 1962.
The Sikorsky S-61N and its non-amphibious configurated variant Sikorsky S-61L are based on and essentially a commercial equivalent of
the militairy S-61B incorporating a number of changes, including a longer fuselage. The Sikorsky S-61L was flown for the first time on 6 December
1960 and received its FAA Type Approval on 2 November 1961. The S-61L entered production the same year. The Sikorsky S-61N with sealed hull and
stabilising SH-3's floats flew first on 7 August 1962. The S-61N version is optimized for overwater operations, particularly
oil rig support. The initial production S-61s were fitted with two 1250shp General Electric CT58-110-1 turboshafts. Both the S-61L and S-61N were
subsequently updated to Mk II standard with more powerful CT58-140 engines giving better hot and high performance and
other improvements and detail refinements. Production of the commercial Sikorsky S-61s ended in 1979.
The 1974-built Sikorsky S-61N c/n 61752 was test flown as N4024S. The helicopter was registered VH-CRU in Australia
but was restored to the US registered as N4042S with Evergreen. In February 1979, the aircraft was noted as VH-CRU at Sydney-Bankstown
and finally the aircraft was restored to the Australian register as VH-CRU with Commercial Aviation on 21 December 1979
and delivered to Australia. After the registration VH-CRU was cancelled the Sikorsky was registered N8511Z in the US.
On 9 January 1981, the aircraft was registered G-BIMU in the UK with British Caledonian Helicopters Limited at London (Gatwick) Airport.
BCHL - British Caledonian Helicopters Limited operated the G-BIMU "Loch Fyne" on the
Gatwick-Heathrow Airlink Helicopter Service that was operated in the period
1978-1986. In autumn of 1987, BHCL was sold to Bristow Helicopters, with
the sale completed in November 1987. Sikorsky S-61N G-BIMU was
registered with Bristow Helicopters, Aberdeen, on 22 May 1990. In
service with Bristow, the G-BIMU 'Stac Pollaidh' was operated and maintained on behalf of the UKMCA UK Maritime and Coastguard Agency on the HM Coastguard
services and stationed at MRCC Sumburgh. After being replaced on 1 October 2007 in HM Coast Guard services at Sumburgh by the new Sikorsky S-92 helicopters,
the G-BIMU was leased to CHC Scotia and relocated to MRCC Stornoway in the Hebrides as an interim aircraft while waiting for the CHC Scotia S-92s
to be delivered. After Sikorsky G-BIMU returned from the lease early 2008, Bristow Helicopters directed the aircraft to Den Helder in the Netherlands.
At Den Helder the G-BIMU is used by Bristow in company with Sikorsky S-61N MkII
G-BDOC on their offshore SAR contract.
On 1 January 2010, Bristow replaced Sikorsky S-61N MkII G-BDOC on the
SAR contract by Sikorsky S-61N G-BPWB. Sikorsky G-BIMU was one of the participant of the SAR-meet at Leeuwarden AFB and was photographed during an exercise at the airbase on 27 May 2009.