mike scholl 1 -> RE: Did Japanese employ skip-bombing? (11/15/2011 5:50:06 PM)
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ORIGINAL: sandman455 Ok, boys and girls have a seat, class has begun. Today we shall examine the problem of dropping bombs on ships from low altitude when you have to do it from a platform that is limited by that inconvenient invention known as the bomb bay. Bomb bays were invented for the sole purpose of giving the aircraft a more aerodynamic profile so as improve range and performance. In exchange for that, they give you almost no flexibility in delivery despite what the engineers at Curtiss wanted you to believe. When you open them, the drag they create is far worse than just a bomb/rack/pylon sitting out on the wing or fuselage of an aircraft. Due to the dynamic loads related to opening them, they are frequently subject to jamming, overspeeding, overstressing, and just a PITA for their crews. I'm talking about modern aircraft here. So you can just imagine how much fun they were back in the 40's. Bomb bays also had the nifty characteristic of actually having a bomb lose INSIDE your aircraft for a brief moment. This really was a game changer. Here is the attack profile of an aircraft with a bomb bay. straight-level-1G-straight-level-1G-straight-level-1G-straight-level-1G-straight-level-1G "Sounds really easy teacher. Is this why the allies skip bombed their way to Tokyo?" What did you say. . . . SKIP BOMB?? Buwhahahahaha. Recording history is always full of surprises. Just take skip bombing as an example. Invented by an Italian (sounds ominious already) today if you wiki "skip bombing" or read the few chapters left behind by the 2-3 folks who so graciously left us with their impressions, you will be lead to believe it was something wonderful. "Hey guys, lets skip some bombs into the enemy today." Honestly, "bounce bombing" has a much more informational entry in wikipedia, but that phrase never caught on because everyone thought it was crazy and the results supported the conclusion. If you check out that wiki entry you will see that there was much theory behind it, but in practice it never really got ironed out and folks were dying enough from the enemy. No need to add to the scrolls with crazy ideas. Lets stay on the subject of bombers skipping bombs. The surprising part is that the tactic most likely had it's name coined from something that was actually very bad. Crews would be watching their fellow avaitors and start screaming over the radio - OMFG, YOUR SKIPPING - everyone climb up! It is a generally accepted concept that you never ever intentionally skip ordnance. Remember that class, it will be on the test. It's pretty simple really - an unretarded bomb comes out of the bomb bay (even a retarded one if down on the deck), it flies right under your aircraft as gravity takes it down. When it hits, it will do a varity of things. As one might suspect, when a bomb is dropped low, it doesn't really have the opportunity to start moving more vertical than horizontal. It might stop or start penetrating, or much more likely, with such a shallow impact angle it will have a high propensity to deflect along the motion of travel. You could call it a "skip." Doesn't really matter if it impacts dirt, sand, concrete or water, the effect is the same. And it is here we can surmise our first clue about the merits of skip bombing. If it works just as well on land as it does on water why was there never anyone evangilizing the merits of skip bombing on land? Hmmm. . . Could it be possible that skipping is bad? Well, think about it. If you did your job during the delivery, a skip means your bomb is now sailing by the target. A very short fuse will help to compensate for this and make the bomb more effective. Only problem is the platform that delivered the bomb is not very far away. The "bounce bomb" wiki page has a nice GIF showing the effect. Now keep in mind this is a bomb traveling beneath you. A 500lb bomb will throw fragments in pretty pattern out to about ______ (google it, I can't tell you) and that is if you don't hit anything. A hit will do the same but with bigger pieces in same radius. Clearly our heros are going to need some extra time to avoid the impending boom! No problemo, just stick a long fuse on the bomb, hit the pickle switch (early or on time, your choice) and go like hell. Too bad those bomb bay doors are slowing you down, huh? Oh and just one more tiny detail: Skipping isn't exactly predictable. Go out to any pond and skip some stones at a raft. Yes they seem to go every which way and that is on a glassy pond. But did you notice that some actually go higher into the air than the height from which they were thrown? Yes, students, planes have not only been blown out of the air, they have actually run into their own bombs. I'm not making this it up. Since the days of WWI, strike aircraft have been shooting themselves down, with some alarming consistency. Skip bombing was correctly identified as just begging for this to happen and never really made it's way into normal bombing tactics. It was conceived in the wardrooms of some gungho crews that were tired of missing naval targets from 10000 feet. The more knowledgeable members of their air groups were wise enough to select ordnance, targets and conditions that would minimize the losses. And for the most part they still dropped their ordnance well off the deck, just to give them plently of run-like-hell time. Just the same, you won't catch me sitting in the tail gunners seat watching the festivities. As you can see skip bombing isn't so cool after all. AND WE HAVEN'T EVEN GOTTEN TO THE BAD PART. "But teacher, the good guys did kill the bad guys with the tactic. . .no? What about Bismark Sea???" The engagement in the Bismark Sea has became a legendary example of "skip bombing." Sounds wonderful and all, but there's more to the story than meets the eye. What were the targets? Where did they come from and what was their location when attacked? What was the weather? How many times had the targets been previously attacked? Yes, yes, yes. All relevent stuff and amazingly, we find that almost every example of successful low level bombing attacks on ships by 2E aircraft was conducted in confined waters (land nearby), on targets that have been attacked for days if not weeks by conventional means (very little AA ammo was left as suggested by the photographs) and by groups of strike aircraft sent into a target rich environment (target diversity/opportunity). Each of these details play a huge role in the survivability of our lumbering 2E's. You see class, You can't really roll in hot with a big 2E aircraft without getting noticed from miles out by your target when you are over open water. Over land, coming in low is actually an effective means of avoiding some of the air defenses when you are at the mercy of a bomb bay (see Polesti raid). This is not the case over water. All you can do is pray for a nice cloud or go insanely low and hope they don't spot you until 5-10 miles. That way the AA crews will be limited to only going #1 instead of #2 before you come into range. To add a measure of difficulty to the problem, you really can't use the mass attack formations of the torpedo 2E carrying crowd. Those guys were stuck with bomb bays too (Japanese 2E's would go so far as to pull the damn doors off before takeoff) but had the luxury of dropping 3000-6000 feet out from their target. This gave them plenty of room for multiple attack angles and more overloading of the target's defenses. If you got to drop a bomb out of a bomb bay, you are going to have to fly right over that target. Having multiple aircraft attack simultaneously on a single target is just asking for mid air collisions, and don't forget those pretty frag patterns. Either we find lots of targets so we can each can have our own, or we will need to take turns running in one at a time. Ugh, doesn't that sound like fun. But wait students, the class is not over. We've been talking about bombing ships down low, lets look at the problem from the target's point of view. Does anyone in class remember the Battle of the Atlantic - the war between U-boats and allied ASW assets? The ultimate weapon of that war were 4E patrol aircraft that could range far and wide looking for U-boats to sink. What few realize is that these 4E's were regularly getting owned by U-boats who chose to fight instead of dive. The ratio was better than 1 to 1 on the sub taking down the aircraft before it could drop its almost always lethal load of ordnance. (Not sure where this number came from but I spotted a few internet references that had loss rates of 1 to 1 after Donitz order his boats to stay up and fight for a few weeks in 1943. There is little doubt that this order resulted in a lowering of the Uboats' success rate as the 4E's got smart) The 50-50 was not a good exchange for the Uboats, but very acceptable for the 4E. Keep in mind that the U-boats were doing this with a single 20mm mount that was unprotected. The 4E's fifty caliber gun in the nose had good ballistics and could do a decent job of suppressing this single exposed mount if the ride down low wasn't too choppy. Having flown down low a little bit I feel obligated to tell you it's often choppy. And for our 4E crews this was bad, because if that 20mm didn't get surpressed for any reason, things weren't looking good. Big plane, bomb bay, long run in. Oh no, I can't look . . . gives me the willies just thinking about it. And just think about how difficult the targeting solution would be for the 20mm gun crew as you ran in from a mile out. Yeah, stand by for a bomb bay bad day. It was going to be ugly. So much so that when those evil U-boats stuck another 37mm mount on a few select U-boats, the SOP for 4E's who came across these "flak boats" was to stand off and call in naval support. No kidding - A solitary U-boat, doing maybe doing all of 17 knots with no real gun crews and no director - who would have guessed. Anyways, the bell is about to sound, so I shall leave you to ponder the horror of attacking a SCTF or CVBG down low with your B-25/A-20/etc. And yes, the kamikaze pilot's worse possible attack profile looked exactly like that of a heavy twin engine aircraft trying to skip bombing, or at least 1/2 of it. In our next class we shall discuss the subtle differences between level bombing at 3k versus 10k. And we will find out how really hard it is to hit a moving target when your bomb has to travel for at least 10 seconds before it hits. RIGHT! It was so difficult that the Allies built 1,000's of "gunship" sub-varients of the B-25, A-20, etc just to sit around not being used for this oh-so-difficult attack profile. Sorry "Sandman", but your rationalizations don't hold water.
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