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GB-1

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GB-1
TypeGlide bomb
Place of originUnited States
Service history
In service1943–1945
Used byUnited States Army Air Forces
Production history
Designed1941–1943
ManufacturerAeronca Aircraft
Specifications
Wingspan12 feet (3.7 m)
Warhead2,000 lb (910 kg) M34 GP bomb
Operational
range
20 miles (32 km)
Maximum speed230 miles per hour (370 km/h)
Guidance
system
Preset azimuth
Launch
platform
B-17 Flying Fortress

The GB-1, also known as the "Grapefruit bomb" and as XM-108,[1] was a glide bomb produced by Aeronca Aircraft for the United States Army Air Forces during World War II. 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

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The U.S. Army Air Corps – which would later become the U.S. Army Air Forces – initiated development of a glide bomb design in March 1941.[2] Intended to allow bombers to stand off outside the range of enemy flak 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 designated GB-2, the Timm Aircraft-designed GB-3, and the Wright Field Equipment Laboratory GB-4.[3]

The GB-1 mated a 12-foot (3.7 m) wing and twin-tail empennage of conventional small-aircraft design to a standard M34 2,000-pound (910 kg) bomb.[2] A gyrostabilizer-based autopilot controlling azimuth was used,[2] allowing the bomb to be set to a specific course following release at a specific altitude and target distance;[1] gliding at a speed of 230 miles per hour (370 km/h), range from a release height of 15,000 feet (4,600 m) was 20 miles (32 km).[3]

Operational history

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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;[2] arriving in the combat zone in September, operational use was delayed due to the limited bombload the glider imposed – a B-17 Flying Fortress 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.[3] On 28 May 1944, 42 of 113 glide bombs released hit Cologne, after being released 18 miles from the Eifeltor marshaling yard in the city at 195 miles per hour (314 km/h); many failed to hold an electrical charge in their batteries, causing their autopilots to fail.[4] German gunners mistook the bombs for aircraft they were shooting down, claiming over 90 kills.[1] Due to the inaccuracy the bombs demonstrated, the Eighth Air Force did not use the glide bombs again;[1] however other units would go on to use over a thousand GB-1s before the end of the war.[3]

Development Of GB-1 Based Devices

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During the war, variants of the GB-1, a self stabilized device without any additional capabilities was adapted for a panalopy of active and passive guidance systems. These systems appeared under one or more names and even under radically different designations. For this reason they sometimes had different MX designations. See Wikipedia: MX designations.

using a contrast seeker for anti-shipping use (GB-5 (MX-611) Originall,[5] This was also known as GB-5A with a Fairchild photo-electric seeker. There were also the GB-5B with a Hammond flare seeker.

GB-12 (MX-615) originally GB-5C. The GB-12 was hampered by an inability to deal with a mixed cloud siruation. GB-12 was resonably uccessful witn either clear skies of a consistent layer of clouds. It failed whan broken clouds were prsent. The use of GB-12 was also considered as an air-to-air weapon. Five of 25 built were tested at Tonopah jn May 1944 before the GB-12 1as abandoned.[6] heat seeking

GB-6 (MX-612),[5] semi-active radar homing

GB-7 (MX-613) originally GB-7A,[5] radio command guidance, there was also the GB-7B later designated as the GB-14 (MX-616) and there was a GB-7C designed to home in on enemy radars and destroy them of which 5 were made. The goal remained beyond the technology available until the late 1960s.

GB-8 (MX-645), was a radio controlled waepon. GB-8 had several limitations.It was difficult to track,GB-8 required 5 radio channels to achive it's mission limiting the number of bombs that could be deploed at the same time. A flare carrying GB-6 was developed. A number of flare dispensing GB-8 could illuminate an ares three miles long. Though GB-8s were sent to Europe the daylight bombing which was standard 8th Air Force policy had no use for illumiination. An anti-personnel version was developed which dispensed anti-personnel bomblets, development of the GB-8 ended September 1945.[5] television guidance

GB-9 (MX494)

GB-10,[3] a flare seeker

GB-11 (MX-614)

GB-13 (MX-619) originally GB-5D, was a flair seeking weapon. It had a nose fairing with a Fairchild B-3 photocell which had a 70 degree homing cone. The GB-13 was intended for use as a skip-bomb which would be dreopped by a low flying aircraft with intent for it to skip off the ground and slide into the target. Testing of the GB-13 ended in late spring of 1945.[6]

GB-15 (MX-717)

[6] and active radar homing were developed, however none progressed beyond the testing stage.[3]

A version for use in dispersing chemical agents, the GB-11, was also trialled but cancelled due to the end of the war;[6]

The GT-1 torpedo-delivering glider was also derived from the GB-1.[7]

Production of the GB-1 was terminated in January 1945;[2] following the end of the war, the bomb was taken out of service.[3]

References

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Citations

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  1. 1 2 3 4 379th 2000 p.39.
  2. 1 2 3 4 5 Ordway and Wakeford 1960, p.119.
  3. 1 2 3 4 5 6 7 Parsch 2003
  4. ↑ Johnson 1995, pp. 105–108
  5. 1 2 3 4 Ordway and Wakeford 1960, p.120.
  6. 1 2 3 4 Ordway and Wakeford 1960, p.121.
  7. ↑ Ordway and Wakeford 1960, p.122.

Bibliography

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  • William Wolf (2021). OfffTarget America’s Guided Bombs, Missiles and Drones 1917-1950. London, United Kingdom: Fonthill Media Limited.
  • 379th Bombardment Group (H) WWII Association (2000). 379th Bombardment Group (H) Anthology, Volume One: November 1942-July 1945. Paducah, KY: Turner Publishing. ISBN 978-1-56311-578-3.{{cite book}}: CS1 maint: numeric names: authors list (link)
  • Johnson, Richard Riley (1995). Twenty Five Milk Runs (and a few others): To Hell's Angels and back. Victoria, BC: Trafford. ISBN 1-4120-2501-X.
  • Ordway, Frederick Ira; Ronald C. Wakeford (1960). International Missile and Spacecraft Guide. New York: McGraw-Hill. ASIN B000MAEGVC.
  • Parsch, Andreas (16 February 2003). "GB Series". Directory of U.S. Military Rockets and Missiles, Appendix 1: Early Missiles and Drones. Designation-Systems. Retrieved 14 December 2017.
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  • Wikimedia Commons logo Media related to GB-1 at Wikimedia Commons
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