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The Leigh Light (abbreviated L/L) was a British World War II era anti-submarine device used in the Battle of the Atlantic. It was a powerful (22 million candela) carbon arc searchlight of 24 inches (610 mm) diameter fitted to a number of the British Royal Air Force's Coastal Command patrol bombers to help them spot surfaced German U-boats at night. It was used from June 1942 onwards to attack U-boats recharging their batteries on the surface at night, which had previously been relatively safe from attack at night. The aircraft would approach the submarine using its ASV (Air-to-Surface Vessel) radar and only switch on the searchlight beam during the final approach. The U-boat had insufficient time to dive and the bombardier had a clear view of the target. 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. Germany introduced the Metox radar warning receiver (later replaced with Naxos when Britain introduced centimetric radar) in an effort to counter the combination of ASV and Leigh Light. Metox provided the submarine crew with early warning that an aircraft using radar was approaching. Because the radar warning receiver could detect radar emissions at a greater range than the radar could detect vessels, this often gave the U-boat enough warning to dive. ==Development== Early air-to-surface radar sets, namely the ASV Mk. II, had a fairly long minimum detection range. Thus as the aircraft approached the target, it would disappear off the radar at a range that was too great to allow it to be seen by eye at night without some form of illumination. At first aircraft solved this problem by dropping flares to light up the area, but since the flare only lit up the area directly under the aircraft, a string (a number of flares in succession) would have to be dropped until the submarine was spotted. Once it was spotted the aircraft would have to circle back to attack, the entire process giving the submarine a fair amount of time to dive out of danger. 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. Wing Commander Humphrey de Verd Leigh, an RAF personnel officer, came up with his own solution after chatting with returning air crew. This was to mount a searchlight under the aircraft, pointed forward and allowing the submarine to be spotted as soon as the light was turned on. He then developed the Leigh Light entirely on his own, in secret and without official sanction—even the Air Ministry were unaware of its development until shown the completed prototype.〔''The Secret War'', by Brian Johnson, Pen And Sword Military Classics, 1978, ISBN 1-84415-102-6 pages 216 - 217)〕 At first it was difficult to fit on aircraft due to its size. Leigh persisted in his efforts to test the idea, and garnered the support of the Commander-in-Chief of Coastal Command, Sir Frederick Bowhill. In March 1941 a Vickers Wellington DWI that conveniently already had the necessary generator on board, (it had been used for anti-magnetic mining operations using a large electromagnet) was modified with a retractable "dustbin" holding the lamp, and proved the concept sound. 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 nighttime 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.〔(Death of Jack Savage ) ''Flight'' September 27th 1945, page 350. Accessed October 2010〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Leigh light」の詳細全文を読む スポンサード リンク
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