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Berichtdoor Tandorini » 18 jan 2009, 21:31





Trial installation of a Helmore Turbinlite in the nose of an early production Mosquito II (W4087)

The Helmore/GEC Turbinlite was a 2,700 million candela (2.7 Gcd) searchlight fitted in the nose of a number of experimental radar equipped Douglas Havoc night fighters by the British during the early part of World War II and around the time of The Blitz. The light was intended to be used to illuminate attacking enemy bombers for defending fighters accompanying the Havoc to then shoot down.

At the time, the then state-of-the-art metre-wavelength AI RDF (radar) equipment was bulky and due to the operator workload required unsuited to carriage by single-engined fighters, so it required a twin-engine design. However, the early radar-equipped Bristol Blenheims lacked the necessary performance advantage over the German Heinkel 111s and Dornier Do 17 bombers then raiding the UK to be truly effective. In addition, there was some doubt as to the best way to find, intercept and shoot down attacking bombers at night, and the idea was put forward for an aircraft that carried its own onboard searchlight that could light up the attacking bombers so that non-RDF equipped single-engined fighters could then see them to shoot down, the single-engine fighters having a considerable performance advantage over the German twin-engine bombers.

At around this time the new Douglas Havoc then entering limited service as an intruder offered an alternative to the Blenheim, also having a considerable performance advantage, and it was decided to conduct experiments with these. The searchlight was based on the work of Air Commodore William Helmore and built by GEC, and was fitted into the nose of the Havoc behind a flat transparent screen with power for the light coming from heavy lead-acid batteries fitted in the Havoc's bomb bay. The radar fitted was the AI Mk.IV, with broad "arrow head" aerials protruding from the both sides of the aircraft nose with additional side-mounted, and upper- and lower-wing mounted, dipoles. The modifications were carried out at Burtonwood Aircraft Repair Depot and the resulting aircraft was known as the Havoc I Turbinlite. The aircraft itself carried no guns.

The unarmed Havoc Turbinlite was intended to find the enemy bomber using its RDF equipment and then use the Turbinlite to illuminate the target for the accompanying Hurricanes to find and shoot down. The Havoc Turbinlite was itself unarmed because the searchlight took up all the space in the nose and was powered by heavy batteries which occupied the only other space available for installing armament, i.e., the Havoc's bomb bay.

The Turbinlite Havoc was known alternatively as the “Hunter," but it was more frequently known at least in the early days of its development (1941), simply as the “Helmore." the derivation being obvious. In point of fact, no Boston I or III aircraft were converted as Turbinlites. The Mk. Is were all trainers, and the Mk. IIIs either day bombers or night intruders. All the early Turbinlites were converted Havoc I or “L.A.M." night fighters. These aircraft were all originally Boston II. The later Turbinlites were converted Havoc II (DB-7A) aircraft, which never had a Boston designation.

As a matter of historical interest, the ex-Havoc I Turbinlites converted at the Burtonwood Repair Depot were serially numbered as follows:-BB 898;BB 909, BD III, BJ 460. BJ 461. BJ 467, BJ 469, BJ 470. AX 923. AW 400, AW 406 and AW 407.

The ex-Havoc II Turbinlites were numbered thus: AH 432. AH 434, AH 436, AH 445, AH 446, AH 447, AH 450, AH 451, AH 452, AH 453, AH 460, AH 470, AH 472. AH 473, AH 478, AH 479, AH 481. AH 483, AH 491. AH 497 and AH 503. At least three Boston III airframes were converted at Heston.

Approximately 31 Havoc I Turbinlite were so modified, using the Havoc I or Havoc L.A.M. (Long Aerial Mine), which had themselves originally been Boston II's, before the advent of the Havoc II Turbinlite, of which a further 39 were built, this time as conversions from the Havoc II. Turbinlite-Havocs served with No. 530, 531, 532, 533, 534, 535, 536, 537, 538 and 539 Squadrons during 1942-43.

They only managed to destroy 1 Heinkel 111, -- 1 probable - and 2 damaged, losses were 31 aircraft. During period September 2, 1941 to January 1943 they lost 31 aircraft, some crews, also 1 of RAF’s own Stirling bombers was shot down.

1451 Flight was formed also at Hunsdon, May 22, 1941 - operational July 21, 1941 which soon became 530 Squadron operating together with the Hurricanes of 3 Squadron.

538 Flight formed September 29, 1941 to become 538 Squadron under command of Squadron Leader J. B. Nicholson ( the only Battle of Britain VC) ----killed in an accident May 2, 1945 while flying as passenger in a 355 Squadron Liberator after a raid on Rangoon.

The concept behind the Turbinlite-equipped Havoc was rendered obsolete with the introduction of centimetric radar along with suitable high-performance night fighters such as the Bristol Beaufighter and the later de Havilland Mosquito, although one of the latter, the Mosquito II, W4087, was itself experimentally fitted with a Turbinlite installation. The Mosquito Turbinlites were built in September 1942, but stopped on negative reports from Wing Commander John 'Catseyes' Cunningham.

The tactic of using single-engined non-radar-equipped fighters at night was later utilised with some success by Germany against RAF Bomber Command later in the war, the tactic being known to the Luftwaffe as 'Wilde Sau' (Wild Boar), however the illumination provided by the much larger-scale fires created by the British allowed visual attacks to be carried out from much longer ranges than had been possible in 1940, rendering the additional illumination that was to have been supplied by an aircraft such as the Havoc Turbinlite superfluous.

Other use.
The Turbinlite was later considered in the search for a method of illuminating surfaced enemy U-boats at night, but lost out to the competing Leigh light.

William Helmore.
Earlier Air Commodore (the title was an honorary one) William Helmore had also been involved in the development of aerial refuelling and was to make the first 'live', (recorded live onto transcription disc for transmission later), broadcast from over the D-Day invasion fleet on 6 June 1944, reporting overhead from an RAF Mitchell bomber. He was also Conservative MP for Watford between 1943 and 1945.
NEC JACTANTIA NEC METU ("zonder woorden, zonder vrees")

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