The Leigh Light (abbreviated L/L) was a British World War II era anti submarine device used in the Second Battle of the Atlantic. It was a powerful 22 million candela searchlight of 24 inches (610 mm) diameter fitted to a number of Britain's Coastal Command patrol bombers to help them spot surfaced German U-boat submarines at night. World War II was a truly global conflict with many facets: immense human suffering, fierce indoctrinations, and the use of new, extremely devastating weapons like the atom bomb. ... The Second Battle of the Atlantic was the longest continuous military campaign of World War II, running from 1939 right through to the defeat of Nazi Germany in 1945, and was at its height from mid-1940 through to about the end of 1943. ... The candela (symbol: cd, Latin for candle) is one of the seven SI base units. ... A searchlight is an apparatus with reflectors for projecting a powerful beam of light of approximately parallel rays in a particular direction, usually devised so that it can be swiveled about. ... Coastal Command was an organization within the Royal Air Force tasked with protecting the United Kingdom from naval threats. ... A patrol bomber, or patrol aircraft, is an airplane designed to operate for long times over water in an anti-shipping or anti-submarine role. ... U-boat is also a nickname for some diesel locomotives built by GE; see List of GE locomotives October 1939. ... USS Los Angeles A submarine is a specialized watercraft that can operate underwater. ...

It was successfully used from June 1942 onwards to attack U-boats recharging batteries on the surface at night. The aircraft would approach the submarine using its radar and only switch on the searchlight beam during the final approach. The U-boat would not have sufficient time to dive and the bomb aimer would have a clear view of the target. It was so successful that German submarines were forced to switch to daytime battery charging when they could at least see aircraft approaching. After its introduction allied shipping losses from U boats dropped from 600,000 to 200,000 tons per month. This article is about the year. ... Four double-A (AA) batteries In science and technology, a battery is a device that stores energy and makes it available in an electrical form. ...

Development

Early air-to-surface radar sets, namely the ASV Mk. II, had a fairly long minimum detection range. 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. 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 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. This long range radar antenna (approximately 40m (130ft) in diameter) rotates on a track to observe activities near the horizon. ...

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.

Squadron Leader Humphry de Verde Leigh suggested that an even better solution was to mount a searchlight under the aircraft, pointed forward and allowing the submarine to be spotted as soon as it was turned on. At first it was difficult to fit to 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 that had been used for anti-mining operations was modified with a retractable "dustbin" holding the lamp, and proved the concept sound. A Squadron Leaders sleeve/shoulder insignia Squadron Leader is a commissioned rank in the Royal Air Force and the air forces of many other Commonwealth countries. ... The Vickers Wellington was a twin-engine, medium bomber designed in the mid-1930s at Brooklands in Weybridge, Surrey, by Vickers-Armstrongs Chief Designer, R.K. Pierson. ... A dustbin is a container used to store refuse which can be made out of metal or plastic¹. Other names include trash can, garbage can and trash bin. ...

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 nightime 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. The Air Ministry was formerly a department of the United Kingdom Government, established in 1918 with the responsibility of managing the affairs of the (then newly formed) Royal Air Force. ... A bomber is a military aircraft designed to attack ground targets, primarily by dropping bombs. ...

Operation

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. In the five months prior 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 at least had some warning and could fight back. ESA photo, phytoplankton bloom along the Bay of Biscay Not to be confused with the North American Biscayne Bay. ...

External link

Technical details of the Leigh Light