Leigh Light
The Leigh Light (L/L) was a British
Early night operations with the new Air-to-Surface Vessel radar (ASV) demonstrated that the radar's minimum range of about 1 kilometre (0.62 mi) meant that the target was still invisible when it disappeared off the radar display. Efforts to reduce this minimum were not successful, so Wing Commander Humphrey de Verd Leigh hit upon the idea of using a searchlight that would be switched on just when the target was about to disappear on radar. The U-boat had insufficient time to dive and the bombardier had a clear view of the target. Introduced in June 1942, it was so successful that for a time German submarines were forced to switch to charging their batteries during the daytime, when they could at least see aircraft approaching.[2]
Germany introduced the
Development
Early air-to-surface
Eventually, time-delayed flares were developed that allowed the attacking plane time to circle. The flare was fired into the air from a buoy previously dropped by the plane. The surfaced submarine could then be seen in silhouette as the plane approached.
At this point the Air Ministry decided that the idea was worthwhile, but that they should instead use the Turbinlite, a less effective system which had been originally developed as an aid for night-time bomber interception. After trials they too eventually decided to use Leigh's system, but it was not until mid-1942 that aircraft started being modified to carry it. Development assistance and production was by Savage and Parsons Ltd. of Watford led by Jack Savage.[5]
Operation
Two types of Leigh Light entered operational use:[6]
- The Turret type, fitted on Wellington aircraft, was a 24-inch (610 mm) searchlight mounted in a retractable under-turret controlled by hydraulic motor and ram. The maximum beam intensity was 50 million candelas without the spreading lens and about 20 million candelas with the lens. Total weight was 1,100 lb (500 kg).
- The Nacelle type, fitted on Catalinas and Liberators, was a 20-inch (510 mm) searchlight mounted in a nacelle 32 inches (810 mm) in diameter slung from the bomb lugs on the wing. The controls were electric and the maximum beam intensity was 90 million candelas without the spreading lens and about 17 million with the lens. Total weight was 870 lb (390 kg).
By June 1942, aircraft equipped with ASV radar and the Leigh Light were operating over the Bay of Biscay intercepting U-boats moving to and from their home ports on the coast of France. The first submarine to be successfully sighted was the Italian submarine Torelli, on the night of 3 June 1942,[7] and the first confirmed kill was the German submarine U-502, sunk on 5 July 1942 by a Vickers Wellington of 172 Squadron, piloted by American Wiley B. Howell. In the previous five months not one submarine had been sunk, and six aircraft had been lost. The Leigh Light turned the tables, and by August the U-boats preferred to take their chances in daytime when they had some warning and could fight back.
At least one
Training
The observation post and concrete indicator arrow at Putsborough were built for Leigh Light training. A buoy anchored in Morte Bay was used as a target. Two other sites at Woolacombe and midway along the bay provided triangulation to assess the accuracy of the bombing attempt.[10]
Effectiveness
Before the Leigh Light, not a single enemy submarine had been sunk in over five months, but in combination with radar, it was so overwhelmingly effective that many German submarine crews chose to surface during the day so that they could at least see the aircraft attacking them and have a chance to fire their anti-aircraft weaponry in defense.[11][12]
References
- ^ Peter Clare (22 July 2009). "Leigh Light Operation". rafb24.com. Archived from the original on 11 November 2009.
- ISBN 978-1-78383-196-8.
- ISBN 978-1-78346-897-3.
- ISBN 1-84415-102-6pages 216–217)
- ^ Death of Jack Savage Flight 27 September 1945, page 350. Accessed October 2010
- ^ Peter Clare (22 July 2009). "The Leigh Light For Night Anti-Submarine Operations". RAF Liberator Squadrons, PC. Retrieved 14 August 2013.
- ISBN 8804505370.
- ^ Brown, Eric Wings on my Sleeve
- ISBN 037000065X.
- ^ "Second World War bombing range indicator and observation post". Historic England. 30 August 2019. Retrieved 4 October 2020.
- ISBN 8804505370.
- ISBN 1-84415-102-6