USAAF WW2 Unguided Glide Bomb GB-1 (and guided developments by USAAF/Navy)

H

HoHun

ACCESS: Top Secret
Joined
9 October 2021
Messages
796
Reaction score
796
Hi everyone,

I just came across this current video on the unguided glide bomb GB-1 experimentally used by the USAAF in WW2:

View: https://www.youtube.com/watch?v=4ij1FjUwi-E


It wasn't very successful, but I think it shows an interesting technical approach to the problem, and the video also makes mention of (possibly only planned, it's narrated from the WW2 or immediate post-war perspective) further developments:

  • GT-1: Unguided gliding torpedo
  • GB-4: TV-guided glide bomb
  • GB-6A: Heat-seeking bomb
  • GB-8: Direct-sight radio-controlled glide bomb
  • GB-12: Marine light-contrast homing glide bomb
  • GB-13: Flare-seeker (implied: otherwise like the GB-12)
  • GB-14: active radar guided bomb ("radar-homing bomb in which both transmitter and receiver are in the missile")
Regards,

Henning (HoHun)
 
Here is my old article about the GB-series bombs (on Russian):

https://fonzeppelin.livejournal.com/111692.html

HoHun said:
GB-13: Flare-seeker (implied: otherwise like the GB-12)
Click to expand...
Frankly, I think the GB-13 was the most promising design in all series. It was truly accurate - on testing, they several times directly hit the target flare itself - and fully autonomous after launch. They could be used efficiently in large salvoes, to home on flares, dropped by "pathfinder" fast bomber (usually Mosquito) over target at night.

In OTL, there weren't much need for such weapon - the British nighttime bombardment systems, like "Oboe" and H2S radar bombsight were good enough - but in case German air defense somehow got increased (say, by SAM's), they would be a perfect answer.
 
Hi Dilandu,

Dilandu said:
Here is my old article about the GB-series bombs (on Russian):

https://fonzeppelin.livejournal.com/111692.html


Frankly, I think the GB-13 was the most promising design in all series. It was truly accurate - on testing, they several times directly hit the target flare itself - and fully autonomous after launch. They could be used efficiently in large salvoes, to home on flares, dropped by "pathfinder" fast bomber (usually Mosquito) over target at night.
Click to expand...

Great article, fantastic that you included some threeviews too!

The "composite" use for night bombing is quite an interesting idea as it gives the bulk of the bombers a stand-off capability. Sounds weird at first, but it makes perfect sense.

Regards,

Henning (HoHun)
 
HoHun said:
Great article, fantastic that you included some threeviews too!
Click to expand...
Thank you!
HoHun said:
The "composite" use for night bombing is quite an interesting idea as it gives the bulk of the bombers a stand-off capability. Sounds weird at first, but it makes perfect sense.
Click to expand...
Basically it's a further development of the idea, already used by British with "Oboe" blind navigation system. It was precise enough for "blind" bombardment - without actually seeing the target - but due to limited number of control channels, it could work only with several planes at once. So RAF used "Oboe" to guide "pathfinder" aircrafts (usually Mosquito) to the target at night. Guided by "Oboe" toward the target, the "pathfinders" released parachute flares, that formed a big bright circle of lights in air - directly over the target. And the approaching bomber stream just targeted those circles of light with their optical sights (they could not see the darkened target itself, but the circle of flares over it was perfectly visible).
 
It was used in combat in the ETO exactly one time. On 28 May 1944, 59 B-17 of the 41st Bombardment Group attacked Cologne with each plane carrying 2 GB-1 glide bombs. Due to various reasons, few of the crews had more than the most rudimentary instruction in the use of these bombs.

The bombers released their bombs at 20 miles from the target point. Out of 118 bombs, 81 were claimed to hit Cologne--the city--somewhere. 44 were claimed to hit within 3.5 miles of the aiming point. Many of the hits were observed in rivers, parks, open space, or similar locations. Just 3 hits were claimed on targets within the aiming point area.

28 bombs failed to enter glide and head to the target, many of these doing wild gyrations and acrobatics on the way down. Accompanying P-38 reconnaissance planes filmed the whole debacle.

The post mission assessment was so scathing that the GB-1 was never used again, and it faded back into obscurity.
 
 
T. A. Gardner said:
The post mission assessment was so scathing that the GB-1 was never used again, and it faded back into obscurity.
Click to expand...
Essentially there were no need to use it. German anti-air guns were always considered much less threatening, than German fighters. GB-1 allowed plane standoff range against flaks - qhich weren't a big threat - but make plane slower and more vulnerable to interceptors. Which were a a much bigger threat.

P.S. The problem may be lessened if GB-1 was given a folding wing, so it could be carried inside bomb bay and lowered into stream just before launch.
 
Grzesio said:
But they could have been fooled by German decoy sites as well and home on them instead of the actual target.
Click to expand...
Introducing additional light sources during blackout is generally NOT a good idea for defenders) If decoy sites would be too far from actual targets, the bombs would not detect them. If decy sites would be too close - they would only help to illuminate main target. Not to mention that by using color flares and filters on bomb's seekers we could make them fairly unpredictable.
 
Dilandu said:
Essentially there were no need to use it. German anti-air guns were always considered much less threatening, than German fighters. GB-1 allowed plane standoff range against flaks - qhich weren't a big threat - but make plane slower and more vulnerable to interceptors. Which were a a much bigger threat.

P.S. The problem may be lessened if GB-1 was given a folding wing, so it could be carried inside bomb bay and lowered into stream just before launch.
Click to expand...
That and the plane could only carry two. For launching from a B-17, the pilot had to enter a shallow dive to pick up enough speed to launch the bombs without stalling. This couldn't be done in the normal, tight, bomber box formation so the planes had to fly further apart and lost mutual support of their defensive weapons.

It didn't help on the one mission they were used that few of the crews had more than introductory training on using these bombs. Originally, the 41st BG had their crews train extensively at Elgin Field in Florida. Those crews had practiced with the bombs and done multiple live drops. On arrival in the ETO, they were initially used as regular bombers. By the time of the Cologne mission, few of the crews that trained in Florida remained with the group, and those that were still there hadn't used the GB-1 since training in Florida. That meant that accuracy in the drops suffered, crews didn't know how to ensure the bombs were dropped correctly, etc.

Also, the kits for the GB-1's were often not precisely balanced aerodynamically, being essentially a field strap-on thing. If improperly fitted even slightly, the bomb could veer off course or fail to enter glide. Fitting the kits correctly required skilled ground crew who knew how to ensure the wing assembly was fitted and balanced, another thing the 41st lacked by the time Cologne was carried out.
 
Last edited:
T. A. Gardner said:
That and the plane could only carry two. For launching from a B-17, the pilot had to enter a shallow dive to pick up enough speed to launch the bombs without stalling. This couldn't be done in the normal, tight, bomber box formation so the planes had to fly further apart and lost mutual support of their defensive weapons.
Click to expand...
Yep. Essentially, GB-1:

* Limited the bomber load to just two 2000-pdr bombs - about a half of normal short-range load
* Decreased max speed for such limited load - due to increased drag of winged bombs on external garriage
* Required special preparation to launch - first flying at straight launch to set the gyros, and then shallow dive to gain enough speed
* Forced bombers to spread - due to abovementioned need of launch maneuver
* Wasn't accurate even in compairson with usual "dumb" bombs - due to much higher wind influence

For all those disadvantages, GB-1 could offer only standoff range against flaks - which wasn't really needed much, because AA guns were more an annoyance than serious problem by 1944.

It's not that GB-1 was totally useless - in case of German AA defenses drastically improving (for example, if Germans managed to get their SAM in service before the war ended), they could provide the standoff capability for bombers, and quite cheaply. But in OTL, there were simply no need for much standoff.
 

Similar threads

Please donate to support the forum.

Back
Top Bottom