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CEDeaton -> What it takes to put the pickle in the barrel (7/16/2003 5:09:23 AM)
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At the bottom of this message is an excerpt, straight from the B-17 Pilot Training Manual found at [URL=http://www.stelzriede.com/ms/html/mshwpmn1.htm#bomb][/URL] that hopefully will suffice for even the most stubborn grogs. It's a bit long to read, but it is very illuminating on this subject if you take the time to understand a bit about the physics of the task at hand.
It's clear that B-17's can - and did - hit shipping targets both while underway and while in port during the course of the war. It wasn't easy to get a hit, especially on a target at sea where there is much less available with which the bombardier can estimate crosswinds that affect both bomb drift and speed over ground(or sea) because of lack of good ground references. Getting the target speed right might still have been the easiest part since you'd know about how long a Maru, etc. is so you could get pretty close on this one. Proper altitude settings are also critical to accurate bombing. For the non-pilots in the group, in those pre-GPS days, you mainly calibrated your altimeter based on a known altitude at the home field and a with Barometric pressure reading taken at ground level. These are provided shortly before takeoff and sometimes updated in-flight when the data is known. Since there weren't generally going to be friendly weather reports coming out of "Injun Country", in-flight updates while over the target are very unlikely or innaccurate at best so a big swing in the weather between takeoff and tarhget really is a problem.
BUT if you are dropping a bomb every 1/10th of a second in a salvo mode, for instance, at a cruise speed of 170mph, then you are letting one go every 25 feet traveled. Thus, eight 500lb bombs dropped "in a vacum in space" should land in a string that is roughly 200 feet long. Therefore, getting the windage, altitude and airspeed calibrated correctly is still important, but the bomb pattern provides a "cushion" against any bad settings. Keep in mind that in UV we are also generally talking about raids carried out at well under the 20,000 feet assumed in the example below, so modify the circural error probability proportionately for an idea of what the pilot and bombardier were really up against at a given altitude and then draw your own conclusions. (This ought to be good for another 5000+ posts from a few of the whiny posters, but at least this time they'll actually have some real info to work with. :D)
If there was an area where we might realistically degrade Level bomber performance, I personally think it might be against overwater targets that are further from friendly bases and most particularly when the weather is marginal/bad and Barometric pressures would have been literally and figuratively "all over the map". So....
[QUOTE]Here's the straight dope from the USAAF[/QUOTE]
"Consider the following conditions which affect the bomb dropped from an airplane:
ALTITUDE: Controlled by the pilot. Determines the length of time the bomb is sustained in flight and affected by atmospheric conditions, thus affecting the range (forward travel of the bomb) and deflection (distance the bomb drifts in a crosswind with respect to airplane's ground track).
TRUE AIRSPEED: Controlled by the pilot. The measure of the speed of the airplane through the air. It is this speed which is imparted to the bomb and which gives the bomb its initial forward velocity and, therefore, affects the trail of the bomb, or the distance the bomb lags behind the airplane at the instant of impact.
BOMB BALLISTICS: Size, shape and density of the bomb, which determines its air resistance. Bombardier uses bomb ballistics tables to account for type of bomb.
TRAIL: Horizontal distance the bomb is behind the airplane at the instant of impact. This value, obtained from bombing tables, is set in the sight by the bombardier. Trail is affected by altitude, airspeed, bomb ballistics and air density, the first three factors being controlled by the pilot.
ACTUAL TIME OF FALL: Length of time the bomb is sustained in air from instant of release to instant of impact. Affected by altitude, type of bomb and air density. Pilot controls altitude to obtain a definite actual time of fall.
GROUNDSPEED: The speed of the airplane in relation to the earth's surface. Groundspeed affects the range of the bomb and varies with the airspeed, controlled by the pilot. Bombardier enters groundspeed in the bombsight through synchronization on the target. During this process the pilot must maintain the correct altitude and constant airspeed.
DRIFT: Determined by the direction and velocity of the wind, which determines the distance the bomb will travel downwind from the airplane from the instant the bomb is released to its instant of impact. Drift is set on the bombsight by the bombardier during the process of synchronization and setting up course.
....HOLDING ALTITUDE AND AIRSPEED: As the bombardier proceeds to set up his course (synchronize) , it is absolutely essential that the pilot maintain the selected altitude and air- speed within the closest possible limits. For every additional 100 feet above the assumed 20,000-foot bombing altitude, the bombing error will increase approximately 30 feet, the direction of error being over. For erroneous airspeed, which creates difficulty in synchronization on the target, the bombing error will be approximately 170 feet for a 10 mph change in airspeed. Assuming the airspeed was 10 mph in excess, from 20,000 feet, the bomb impact would be short 170 feet."
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