Leigh light
The Leigh Light (abbreviated L / L) was an extremely powerful searchlight developed by the British officer Humphrey de Verd Leigh between 1940 and 1942 (during World War II) , which was used to spot enemy submarines from a great distance in the dark can.
development
The Royal Air Force's Coastal Command was founded in 1936 and had grown considerably in the course of the anti-submarine campaign since the beginning of the war. Patrols of the Sunderland flying boats and Hudson bombers used here forced the German submarines to dive during the day, but were of little use against submarines operating at night. Navy submarines often appeared for hours at night to charge the batteries for underwater travel with the diesel engines running. The Coastal Command urgently needed radar technology on board its aircraft in order to be able to counter the submarine danger.
Night submarine hunt
ASV (Air-to-surface vessel) , a system that was mounted on some machines in early 1940, made it possible to locate battleships at night, but did not capture the submarines with their small silhouette. The more powerful ASV Mark II system, which was then developed, did not allow the RAF to produce the number requested by the Coastal Command, and so by the end of 1940 only 49 aircraft were initially equipped with these radar systems. Instead, the RAF decided to give the RAF Fighter Command preferential radar equipment to equip its fighters for combat with the German night bombers. However, the ASV Mk. II had a fairly large “minimum detection range”, so it could no longer perceive an object from a certain proximity. When the aircraft approached the target, the target disappeared from the radar screen at a distance of 1.8 km - so early that the approaching submarine could easily descend in time after the alert from the attentive bridge watch. Meanwhile, the plane had to approach virtually blind. A submarine could only be seen with the naked eye on particularly moonlit nights or when the sea was particularly smooth. Before they had the Leigh Light, planes threw so-called flares , light bombs on parachutes, then turned around and hoped to see the target in their glow. In the meantime, the submarine, which only needed a little more than 20 seconds for the alarm dive, was already under water. Finally, flares with a delay mechanism were developed. The aircraft dropped a special buoy and turned to attack, only then did the light work of the buoy, which had been converted into a flare , and in the glow of which one could discover the submarine.
Wing Commander de Verd Leigh's idea
After speaking to a crew that had just returned from the mission, Wing Commander Humphrey de Verd Leigh, an officer at Coastal Command headquarters, came up with a solution to the problem. His idea was to put a forward looking searchlight under the plane. De Verd Leigh then developed this headlight on its own initiative and without any official support - even the Aviation Ministry only learned of this development when the complete prototype was presented. At first it was difficult to find an airplane of the appropriate size. Leigh, in his constant efforts to realize his idea, eventually won the support of the head of Coastal Command, Sir Frederick Bowhill. In March 1941, a test with a Vickers-Wellington bomber , which had the necessary generator on board - this was originally used to feed an electromagnet to ward off magnetically ignited sea mines - proved the value of the concept. It took a total of 18 months of development time, not only because of technical difficulties, but also because of the clumsiness and indifference of the bureaucracy, before the Leighlights could be used. The L / L had a diameter of 610 mm (= 24 inches) and was attached to some patrol bombers of the Coastal Command of the Royal Air Force. A carbon arc lamp known from its use in marine searchlights since World War I produced 22 million candelas in the first version .
commitment
The Leigh Light was not used until June 1942; until then, submarines had been relatively safe from night attacks. The RAF felt submarines now means "ASV radar" in ( A ir-to- S urface V essel radar ) and turned off the Leigh Light a late. The submarine then did not have enough time for diving or alarm diving . This procedure was so successful that the German submarines charged their batteries for a while during the day during overwater travel - this gave them more time between sighting the aircraft and its overflight.
German countermeasures
When Karl Dönitz , commander of the submarines, heard about the searchlight, in an overreaction that was rather untypical for him, he ordered that he only sail submerged at night in the Bay of Biscay . This slowed down the march of the boats through this area of the sea considerably. Since the speed possible with electric motors when driving underwater was significantly lower than driving above the water with diesel engines, the travel time of a boat during an operation was extended by up to five days. As a result, the Navy equipped the submarines with a passive radar detector made in France called Metox . A wire-covered wooden frame that was attached to the submarine tower served as an antenna for this. This construction was called the Biskayakreuz by the crews of the boats in reference to the area of operation and was not very popular, because it had to be dismantled for each diving process and was often broken due to its light construction. The antenna also had to be rotated by hand at regular intervals and a cable leading through the tower hatch into the interior of the boat had to be hauled in for every dive. Metox had a longer range than British radar; this often gave the submarines enough time to submerge. When the British later used shorter-wave radar beams, Metox was replaced by the Naxos radar detector .
variants
According to De Verd Leigh's specifications, the headlights were designed in the company of the British aviation pioneer and RAF pilot of the First World War, Jack Savage, in Watford . There were two types of Leigh Lights. The heavy, hydraulically controlled version was installed in place of the bow machine-gun turret of a Wellington bomber . These headlights, weighing over 500 kg, generated a light intensity of 20 or 50 million candela , depending on the lens used . A smaller, electrically controlled variant, weighing a little more than 400 kg, hung on a bracket below one of the - usually the right - wing of Catalina flying boats or B-24 bombers . These Leigh Lights produced a beam of light up to 90 million candelas.
Quotes
"Entry into service of a device so important was inexcusably slow, ... (It took an inexcusably long time until this device of such importance was used, ...)"
"[...] the" Leigh Light ", the airborne searchlight which pinpointed a surfaced enemy submarine at night like a rabbit in a headlamp beam ([...] the Leigh Light, a searchlight that pegs a surfaced enemy submarine from the air, like a rabbit in the beam of the car headlight) "
Others
There was a search light called "Turbinlite" (2,700 million candelas, mounted on some US Douglas A-20s ).
Web links
Footnotes
- ^ Peter Clare: Leigh Light Operation . rafb24.com. July 22, 2009. Archived from the original on November 11, 2009. Retrieved on October 29, 2009.
- ↑ Clay Blair : The Submarine War. Volume 1 The Hunters. Heyne, Munich 1996, p. 266.
- ↑ The Wing Commander is a lower staff officer rank in the Royal Air Force and roughly corresponds to the German major .
- ^ Brian Johnson: The Secret War. Pen And Sword Military Classics, 1978, ISBN 1-84415-102-6 , pp. 216-217.
- ↑ Clay Blair : The Submarine War. Volume 1 The Hunters. Heyne, Munich 1996, p. 267.
- ^ Bernard Ireland: Battle of the Atlantic. Naval Institute Press, Annapolis, Maryland 2003, p. 93.
- ^ Peter Padfield: The U-Boat War 1939-1945. Bechtermünz, Augsburg 1999, p. 261.
- ↑ "We called it the Biscay Cross because it was used for the first time by our boats in the Biscay," quoted from: Herbert A. Werner: Die iron coffins. Heyne, Munich 1970, p. 125.
- ↑ Jack Savage's obituary
- ↑ Jack Savage is also considered to be the inventor of heavenly writing .