Low levels of precision led to massive amounts of damage in Germany and Japan in World War II. The military measures precision in a complex term called "circular error probable," or CEP. That means the distance from the intended point of impact that at least 50 percent of munitions can be expected to land within.
The CEP of bombs dropped from the WWII-era B-17 was 3,300 feet. Only half of the bombs dropped were expected to land within 3,300 feet of their intended target. "If you wanted to have a high probability of destruction of a target of 60 (feet) by 100 feet, you'd need about 1,500 airplanes and about 9,000 bombs," Crowder said. ( Not sure how ACCURATE those numbers are ? )
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Taken from some notes made by a B29 Bombadier.
Part One: What is CEP?
In order to qualify as a bombardier, a bombardier in training dropped a
total of 100 single releases from varying altitudes to establish his
"Probable Circular Error" (CEP). His CEP had to be less than 200 feet to
qualify him as a visual bombardier.
Before he began to drop bombs for official scoring, he was given ground
training on a simulator and in the classroom, then was allowed to drop 10
practice releases (during a series of three practice missions), to "familiarize"
him with the task. His CEP for the practice missions had to be within 500
feet before he was allowed to drop bombs for qualification.
If it was not, he was given a check ride and intensive training for 10 more
releases during a series of practice missions, then was given another check
ride. He faced elimination (was "Washed Out" of the course) if his CEP had
not been reduced to below 500 feet for the total of 20 practice releases.
After qualifying as a bombardier, every release he made was figured into his
CEP for his entire career.
This CEP enabled the mission planners to predict his performance as a
bombardier making his own aimed drops, and additionally gave them planning
factors to predict the damage that could be expected on a given target from
any altitude of release, thus helping to select the drop altitude for that mission.
It also helped them to plan formation size for the "Toggleers" who dropped
on that lead bombardier's release; and how many formations of planes to send
over a given target; as well as what bomb load to put on them.
So you see, CEP was a very important planning factor, for based on it,
planners were able to select the lead bombardiers; size of the formations;
number of formations; altitude of release; bomb load; aiming point(s) and
intervalometer setting, in order to destroy a given target.
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