Automatic Gun-Laying Turret facts for kids
The Automatic Gun-Laying Turret (AGLT) was a special gun system used on some British bomber planes during World War II, starting in 1944. It was also known as the Frazer-Nash FN121. This system used radar to help aim and fire the guns from the back of the plane.
AGLT had a small tail warning radar and a fire-control system. This meant it could find enemy fighters coming close. It could then aim the machine guns and even fire them automatically. This was very helpful, especially in total darkness or thick clouds. The radar warning and fire-control system had code names like Village Inn and "Z Equipment", or its serial number TR3548.
The plan was for all Royal Air Force (RAF) bombers to have a special IFF infra-red light on their nose. This light would help gunners avoid shooting down friendly planes by mistake. However, this didn't always work perfectly. Sometimes Allied planes without the lights flew near AGLT planes. Even with the lights, gunners couldn't always see them. Because of this, the Village Inn system was mostly used as an early warning system. It would tell the gunner that an enemy plane was nearby. Gunners rarely used the fully automatic "blind-firing" feature.
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How the AGLT System Was Developed
The idea for the AGLT system came from a team led by Philip Dee. The main design work was done under Alan Hodgkin. They started working on it in early 1943 after the Air Ministry asked for such a system.
Testing the New System
The system was tested by the Telecommunications Research Establishment (TRE) at RAF Defford. They used several Lancaster bomber planes for these tests. After successful testing, the system went into production.
How the Radar Worked
The AGLT system had a transmitter and a receiver unit. This unit was usually in the navigator's part of the plane. It sent out radar signals using a special antenna shaped like a dish. This dish was attached to the rear gun turrets.
The radar worked by sending out radio waves at a wavelength of 9.1 centimeters (3 GHz). These waves would bounce off enemy planes. The system then sent a signal back to the gun turret. There, the gunner saw the enemy plane's signal on a screen called a cathode ray tube (CRT). This screen was next to the gun sight. The image from the screen was projected onto the gun sight.
Aiming and Firing
At first, the gunner had to be told the enemy's distance over the plane's intercom system. The gunner would then use foot pedals to set this distance on the gun sight. Later, this process became automatic. The distance information was sent directly to the gun sight electronically. The gunner just had to move the guns to put the "blip" (the enemy's signal) in the middle of the gun sight. When the enemy was close enough, the gunner would open fire. The gun sight automatically figured out things like wind and how much bullets would drop.
Squadrons Using AGLT
The first RAF squadron to use Village Inn in real missions was No. 101 Squadron RAF in the autumn of 1944. Soon after, No. 49, No. 156, and No. 635 Squadrons also started using it.
Different Versions of AGLT
Village Inn was made in four main versions, called "Marks":
- AGLT Mark I — This was the first design.
- AGLT Mark II — This was an improved Mark I, but it was stopped soon after.
- AGLT Mark III — In this version, the radar antenna was separate from the turret. This meant the radar could scan even if the turret wasn't moving.
- AGLT Mark IV — This was another improved version.
The AGLT system was also put on some other planes, like the Avro Lincoln bomber. A similar system was also developed in the United States by the Emerson Electric Company. However, their system was not found to be better than the British one, so it was not used further.
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