} The GB-1, also known as the "Grapefruit bomb" and as XM-108,379th 2000 p.39. was a

glide bomb A glide bomb or stand-off bomb is a standoff weapon with flight control surfaces to give it a flatter, gliding flight path than that of a conventional bomb without such surfaces. This allows it to be released at a distance from the target rat ...

produced by

Aeronca Aircraft Aeronca, contracted from Aeronautical Corporation of America, located in Middletown, Ohio, is a US manufacturer of engine components and airframe structures for commercial aviation and the defense industry, and a former aircraft manufacturer. F ...

for the

United States Army Air Forces The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...

during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

. Intended to allow bombers to release bombs from outside the range of enemy defenses, over one thousand GB-1s were used in combat before the end of the war.

Design and development

The

U.S. Army Air Corps The United States Army Air Corps (USAAC) was the aerial warfare service component of the United States Army between 1926 and 1941. After World War I, as early aviation became an increasingly important part of modern warfare, a philosophical ri ...

– which would later become the U.S. Army Air Forces – initiated development of a glide bomb design in March 1941.Ordway and Wakeford 1960, p.119. Intended to allow bombers to stand off outside the range of enemy

flak Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...

while releasing their bombload, while also potentially allowing for more precise targeting due to the shallow glide path the bomb would follow, the design resulted in three prototypes; one developed by Aeronca designated GB-1; a design by

Bellanca AviaBellanca Aircraft Corporation was an American aircraft design and manufacturing company. Prior to 1983, it was known as the Bellanca Aircraft Company. The company was founded in 1927 by Giuseppe Mario Bellanca, although it was preceded by p ...

designated GB-2, and the

Timm Aircraft The O.W. Timm Aircraft Company was an American aircraft manufacturer founded by Otto William Timm, based in Los Angeles, California. History Between 1911 and 1922 O.W. Timm built several aircraft with varying success before he founded, in 1 ...

-designed GB-3.Parsch 2003 The GB-1 mated a wing and twin-tail

empennage The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow.Crane, Dale: ''Dictionary of Aeronautical Terms, third ed ...

of conventional small-aircraft design to a standard M34 bomb. A

gyrostabilizer A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rota ...

-based

autopilot An autopilot is a system used to control the path of an aircraft, marine craft or spacecraft without requiring constant manual control by a human operator. Autopilots do not replace human operators. Instead, the autopilot assists the operator' ...

controlling

azimuth An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematicall ...

was used, allowing the bomb to be set to a specific course following release at a specific altitude and target distance; gliding at a speed of , range from a release height of was .

Operational history

Selected for production over the competing GB-2 and GB-3 due to its simpler control system and its proving more practical for bomber carriage, production of the GB-1 began in May 1943; arriving in the combat zone in September, operational use was delayed due to the limited bombload the glider imposed – a

B-17 Flying Fortress The Boeing B-17 Flying Fortress is a four-engined heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). Relatively fast and high-flying for a bomber of its era, the B-17 was used primarily in the European Theater ...

bomber could carry only two GB-1s on a mission, one on a rack under each of the bomber's wings – and the accuracy of the GB-1 proving to be significantly worse than that of ordinary bombs. Despite this, by May 1944 the first releases of GB-1s were undertaken. On 28 May 1944, 42 of 113 glide bombs released hit

Cologne Cologne ( ; german: Köln ; ksh, Kölle ) is the largest city of the German western States of Germany, state of North Rhine-Westphalia (NRW) and the List of cities in Germany by population, fourth-most populous city of Germany with 1.1 m ...

, after being released 18 miles from the Eifeltor marshaling yard in the city at ; many failed to hold an electrical charge in their batteries, causing their autopilots to fail.Johnson 1995, pp. 105–108 German gunners mistook the bombs for aircraft they were shooting down, claiming over 90 kills. Due to the inaccuracy the bombs demonstrated, the

Eighth Air Force The Eighth Air Force (Air Forces Strategic) is a numbered air force (NAF) of the United States Air Force's Air Force Global Strike Command (AFGSC). It is headquartered at Barksdale Air Force Base, Louisiana. The command serves as Air Force ...

did not use the glide bombs again; however other units would go on to use over a thousand GB-1s before the end of the war. During the war, variants of the GB-1 using a

contrast seeker Optical contrast seekers, or simply contrast seekers, are a type of missile guidance system using a television camera as its primary input. The camera is initially pointed at a target and then locked on, allowing the missile to fly to its target b ...

for anti-shipping use (GB-5,Ordway and Wakeford 1960, p.120. GB-12),Ordway and Wakeford 1960, p.121. heat seeking (GB-6),

semi-active radar homing Semi-active radar homing (SARH) is a common type of missile guidance system, perhaps the most common type for longer-range Air-to-air missile, air-to-air and surface-to-air missile systems. The name refers to the fact that the missile itself is ...

(GB-7),

radio command guidance Missile guidance refers to a variety of methods of guiding a missile or a guided bomb to its intended target. The missile's target accuracy is a critical factor for its effectiveness. Guidance systems improve missile accuracy by improving its P ...

(GB-8),

television guidance Television guidance (TGM) is a type of missile guidance system using a television camera in the missile or glide bomb that sends its signal back to the launch platform. There, a weapons officer or bomb aimer watches the image on a television screen ...

(GB-10), a flare seeker (GB-13), and

active radar homing Active radar homing (ARH) is a missile guidance method in which a missile contains a radar transceiver (in contrast to semi-active radar homing, which uses only a receiver) and the electronics necessary for it to find and track its target aut ...

(GB-14) were developed, however none progressed beyond the testing stage. A version for use in dispersing chemical agents, the GB-11, was also trialled but cancelled due to the end of the war; the GT-1 torpedo-delivering glider was also derived from the GB-1.Ordway and Wakeford 1960, p.122. Production of the GB-1 was terminated in January 1945; following the end of the war, the bomb was taken out of service.

References

Citations

Bibliography

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External links

* {{US WWII guided bombs World War II guided missiles of the United States Guided bombs of the United States Weapons and ammunition introduced in 1943