Most accurate divebomber

[Shortround6]

The idea of the dive brakes was to slow the rate of decent so that more time could be taken to aim or correct aim, that a lower altitude drop could be used ( pulling out at say 240mph/knts instead 350 or more) also increasing accuracy and that at the lower speed the controls were still effective.

 

[GregP]

In a 90° dive, you have to release the bomb in coordinated flight, with no slip or skid or pull-up or push-over, or you will miss rather widely. In a 60° dive you can use very minor corrections, reacquire the target, and resume coordinated flight quickly. In a 90° dive, you have to use gross corrections because there is so little room for error, and reacquiring coordinated flight is more difficult while remainiing on target. Going straight down, a 20° bank won't doo much for you in the way of moving the impact point. In a 60° dive a 20° bank for a couple of seconds will move the aim point a few degrees.

If you actually try to hit a target from directly above, you will have a real CEP (circular error of probability). In a 60° dive, they are almost always on or very close to target left and right, and usually have either overshoot or undershoot if they miss. The CEP is more oval and most pilots, in the USA anyway, learned how to narrow the oval with practice so the error was quite small. The Germans and Japanese were pretty good at it, too, and there was likely little to choose between good dive bomber pilots of any nationality.

The real trick was to not get shot down by your target if the target happened to be a heavily-armed ship and then avoiding the single engine fighters that were always looking to shoot you down. In that regard, the SBD was probably the dive bomber best suited to fighter tactics for survivial once the bomb had been dropped. It gave a very good account of itslef in the war in the Pacific and was used as a fighter on several occasion with relatively good results.

If you open the dive brakes in an SBD while in level crusing flight, it feels like you just flew through Elmer's Glue and you lose speed RIGHT NOW ... feels like you just deployed a parachute! I have several friends at the museum who have experienced just that in our SBD, and they were all taken by surprise at the g-foprce deceleration despite being warned the dive brakes were about to be deployed. The camera plane leapt ahead like a Cheetah on full sprint and the SBD pilot had to close the dive brakes rather quickly to avoid losing more than 40 knots in an instant. I have heard the terminal speed of the SBD in conversation, but can't recall it just now. I'll ask this coming weekend.

 

[tyrodtom]

In any form of bombing, from vertical drops, to level drops , the bomb has to be released while in coordinated flight, or where you're aiming with the bombsight means nothing.

 

[GregP]

That's true for dumb bombs in WWII.

If you have smart bombs, then it really doesn't matter since they guide themselves after release. Still, I'd think that even with smart bombs, you'd want to be at least closely coordinated just to get a good separation from externally-mounted ordnance. If it comes from a bomb bay, it might not matter much these days with smart weapons.

My point, as I'm sure you know, is that making small corrections while going straight down is tougher than in a steep but not vertical dive. Why make it harder on yourself and the aircraft?

Good pic of the SBD above, Shortround. Shows the dive brakes and bomb trapeze very well.

 

[tyrodtom]

I can see in a vertical or near vertical drop, you'd have to start your dive very close to straight over the target, because you can't toss the bomb from a vertical dive, and your ability to move the aircraft laterally, or steepen or lessen the dive to line up in that way can only do so much.
But early war Stuka pilots were supposed to be the cream of the crop, more elite than fighter pilots.

I know smart bombs have changed things greatly, but they still have to be dropped within certain parameters, even a smart bomb can be stalled.

 

[Shortround6]

The SBD pilots description is a little confusing to me but then I am not a pilot. He describes the fight path as a 70 degree dive but the plane as being vertical. A chart from the pilots manual shows that with the dive flaps open in a terminal velocity dive about 4.75 degrees of nose down angle of attack is needed for a 70 degree angle dive. For 80 degree dive angle about 5.2 degrees down angle is needed.

This may be a reason true 90 degree dives were not done. From the chart a true 90 degree flight path requires the plane to be 5.6 degrees beyond vertical.

The plane may certainly have felt vertical

 

[Aozora]

While the U.S Navy refined the principles of dive bombing (the original concept was devised by the British during WW1) and developed the bomb crutch, the USN pilots didn't want the automatic pull-out:

Interesting comment on pilots misjudging the dive angle, so having the guidelines painted on the side of the canopy must have helped. Another factor not mentioned is that at dive angles greater than about 65 deg pilots felt as though the aircraft was diving beyond the vertical

(from Peter C. Smith, Douglas SBD Dauntless, Crowood 1997, pages 9 10)

Some more reading...

(Smith 1997 page 46)

 

[VBF-13]

If anybody is curious the actual training in the SBDs took about two months, then they went off for their carrier-quals. Total time, over 100 hours. Different characters on the flights, ranging from familiarity and practice, to gunnery and bombing, instruments, night flying, you name it. On many days, they went up two or three times. Here's a blown-up scan of a 35mm negative of the old man and his gunner, probably over the Atlantic. I just recently found it stuck in between the pages of his scrap book, and I don't even know if he ever even saw it. I've been meaning to take it to Walgreen's, but I don't know if they even know how to develop these, anymore, and I'd really hate like heck to freak them out, lol. But, anyway, here's my contribution to the snapshots. Great information, here, too, I learned a lot...

 

[Ascent]

These next few quotes are from a pilot on 110 Sqn in India flying Vengances, taken from this thread Gaining An R.A.F Pilots Brevet In WW11 - PPRuNe Forums

The first is about learning to bomb in the Vengance (he was expecting Spitfire's) one about the vengance generally and the last is from his first sortie. The whole thread is an interesting read but these are relevant to the thread.

1."Training started at once. Really it was simple, we had to learn to dive-bomb and to fly any position in a box-of-six which was to be our normal tactical formation. A range was set up on a big sandbank (it was the dry season) on a bend in the river Damodar, about 30 miles from Madhaiganj. Who supplied the observers, and what equipment they had, I do not know. There must have been two of them at a safe distance, with lines of sight at right angles and some form of theodolite.

We went to work on this range right away. All we were concerned about was results, and with practice these became quite good. Four 11 1/2 lb smoke bombs were carried on a rack under the left wing, and dropped one per dive. The trip to the range took about 15 minutes, and by then you'd climbed to bombing height of 10 - 12,000 ft.

The trick was to fly up to the target in such a way as to be vertically above it when you rolled over. The best method was to keep it in view, running along tight against the left side of the fuselsge from the nose back until it slid under the wing, count ten and go over, crouched, standing on your rudder pedals on the way down.

The steeper the dive, the better the result. You "throw" your aircraft at the target much as a darts player "throws" his wrist at the board. You must not forget to (a) use the dive brakes and (b) pull out in good time. As to what constituted "good time" we experimented, pulling out high to start with and then reducing until we'd established the lowest safe height. This was reckoned to be when the altimeter passed 3500 ft above ground, although the aircraft would be lower at this point, as the instrument lagged by several hundred feet.

Having planted your first bomb and swung round to see where it had gone, you climbed up and dived three more times, then home. As such a climb and repositioning took you ten to fifteen minutes, two or three aircraft could space themselves out and use the range together.

These sorties lasted little more than an hour and formed the greater part of our training. We improved with practice: at the end almost all bombs would go in a 100-yard circle."



2."Incredibly, the lockable tailwheel also retracted - an unnecessary complication in an aircraft with absolutely no need for it ! (Neither the Spitfire nor Hurricane had them). Hydraulics also powered flaps, bomb doors, cowl gills and the dive brakes.

These last are the most important fitments on a dive bomber, and the Vengeance had splendid ones. Massive grids extended above and below the wings * On the upper surfaces the grid was hinged on the front,* so airflow would tend to force it shut. On the lower, the hinge was at the rear, with the opposite effect. Top and bottom were coupled, so the forces cancelled out.

These brakes could be opened at any speed, partially or completely, and when fully open restricted the terminal velocity to about 300 mph (knots did not come in till much later). They did not interfere with control or trim in any way, for they were well clear of the wing surfaces when fully extended and so did not obstruct the airflow over or under them. This low terminal speed gave us plenty of time in the dive to draw a bead (in our case the yellow line) on the target.

Two unique design features improved dive stability. The angle of Incidence was zero, the Vengeance being AFAIK the only dive bomber designed from the outset to dive vertically. The side effect was a comical tail-down "sit" in the air in level flight. A Vengeance "dragging its a###" could be recognised miles away.

Flying slowly, as in coming in to land, this combination of tail-down attitude and long nose meant no forward vision. We had to put up with that, after all the Spitfire had been almost as bad. In the same way the fin was fitted without the usual small offset to compensate for the gyroscopic effect of the propeller.

With powerful dive brakes and these novel features, the Vengeance made an excellent dive bomber. In a vertical dive, it was smooth and stable (with only 20 seconds to line up, you don't want your nose swanning about round the target). Judged purely as a flying machine, it was useless. Ponderous, awkward and slow, all was forgiven for the sake of that dive. One-trick pony it may have been, but it did its one trick very well indeed, and that was all that mattered to us."

 

[Ascent]

3."I've said that we normally put up only six aircraft at a time. On this single occasion, we scraped up twelve - six from 110 and six from 82 Sqdn. 82 ("Out of the blue came Eighty-Two!") were to go in first. As a new boy on 110, I flew the 6 position, which would mean I would be the last man of all to go down. As I never flew in a 12-ship strike again, this was the only time I was able to watch all the action from the air.

Topper was leading our six. We came in from the North at 12,000 ft with 82 ahead. It was afternoon. As we reached the island, the heavies opened up. Our two formations were "weaving", flying a slow zig-zag with a course change every twenty seconds or so. This confuses the gun predictors, so the flak bursts were 2-300 ft off to the side, but uncomfortably accurate for height. We overflew the island, then turned left in a wide sweep over the mainland, flying right round until we reached Akyab again, but this time coming out of the haze and gloom of the eastern sky.

It was a clever ruse (if it was a ruse - perhaps the 82 leader had simply misjudged his first run-up). Later intelligence confirmed that the Jap had put out an air raid warning the first time. But as we didn't bomb, they assumed that we were going on somewhere else and sounded the all-clear. Second time round, we caught them napping, sitting with their evening rice.

The jail was a bomber's dream target. Built on the cart-wheel plan, I suppose it was 2-300 ft across. It was unmissable. It must have been the largest building on the island. As the last man on the line, I could allow myself room to watch the action. 82 were a mile ahead, so I watched them all go down. They were like beads sliding down a string, three spaced out at a time. I could see the bomb flashes dead on target, billowing up in smoke and dust.

Then it was our turn. Topper waggles his wings. This is the signal for the rear "vic" to drop back and move into echelon starboard. A few seconds later, he waggles again and opens his bomb doors. All open theirs. 3 and 6 (me) swing across into echelon on 2 and 5 respectively. Now we're all in a diagonal line like a skein of geese. (This formation change is made only at the last moment, for although it looks nice on the newsreels, it leaves you practically at the mercy of an attacker - and it advertises your imminent attack to any watcher on the ground).

Mechanically I go through my drill: Canopy shut, check bomb doors open, bomb switches "live", trims neutral, 2100 rpm, mixture rich, gyros caged, cowl gills closed, straps tight.

The first three go down. A few seconds later 4 goes over, settles in the dive and puts his brakes out. 5 puts his out as he rolls over. I put mine out, throttle back to a third and then roll. This gives us an extra bit of spacing for safety.

After that, it's simply "doin' what comes nacherly". Rolling over, I throw my head back and look straight down on the dust cloud over the jail - or what's left of it. Then it's just a matter of sighting down the yellow line and "flying" it onto the target. Feet braced on my big fat rudder pedals, I sense the dive is as near vertical as dammit - you can feel it with practice. Topper has done us proud, for this is a follow-my-leader operation, and if he's off vertical, then the whole thing will be a mess.

I can see 4 and 5 ahead for a few moments, then 4 pulls away from my field of vision. Bomb flash. I'm snatching quick glances at my altimeter, which is spinning like a broken clock, one sweep of the "big hand" every two or three seconds. 5 pulls away, keep line on target, bomb flash, 5000 ft, check line, 4000, check, 3500, press button (on throttle grip) and pull, pull, pull for dear life - literally - five seconds too late and you're dead.

Things go dark and I'm crushed down in my seat by "G" for a few moments, then I relax a bit and vision clears. Brakes in, we're in a 40-degree dive from a thousand feet, still with most of the 300 mph we picked up on the way down.

The sky looks like a dalmation dog, for light AA has been pumping away merrily for a minute or two. Surprised, it dawns on me that they're still firing at us. I feel quite indignant. Poor little me, what have I done to deserve being shot at at like this?

This dangerous reverie exasperates the battle-hardened Robbie behind. "Get weaving, Skipper", he roars, sees a gun position on the ground and gives it a long burst to distract the gunners from their aim. That wakens me up.

No time to ruminate - jink and get down on the deck as fast as you can! At this point I should explain that aircraft come out of the dive heading every which way, depending on where they were facing when they pressed the button, and that has been affected by the amount of "weathercocking" which they'd had to do on the way down. It was rather like a Red Arrow "bomb burst", only in sequence.

So you had to pick up your bearings, decide which way was home, and pull round onto it. It must have life more difficult for the AA, as no two of us were following the same path, and this was all to the good.

Now I'm sailing over the tree tops and out of most harm's way. Not entirely, any Jap with a rifle or LMG is going to try a potshot if he sees me in time and in range. It was not uncommon for aircraft to come back with small arms hits.

Dive bombers are a very hard target for AA. Before diving, they can weave as we did to keep out of trouble. Diving, they are well nigh impossible to hit. Pulling out, they are going so fast and low that aimed fire is ineffective. All the gunners can do is to put up a barrage through which they hope we might fly. If they get one it's pure luck. Having said that, I must admit there were cases of people just not pulling out of a dive. No one could say whether they'd been hit or not. The probability is that they were concentrating too hard and left the pull-out too late. The margin for error was tiny.

Once level, you can open your canopy and close bomb doors to reduce drag - but not while you're still pulling "G" in the turn onto the home straight! In a dive, the two internal 500 lb bombs, if simply dropped from the racks, might hit the front wall of the bay, or drop into the arc of the prop. Either way would be disastrous.

To avoid this each bomb is carried in a fork pivoted at the front of the bay. Round the bomb is clamped a "trunnion band" which carries the two "trunnions" - projections which engage in slots on the ends of the forks. Released, the bomb flies out and then off - safely - for you! (the Stuka used the same idea).

On pulling out, centrifugal force will continue to hold these forks out against the pull of "bungee" cords, even after the bombs have gone. There's always one who's too keen to pull in his doors - and traps them against the forks! Everything about a VV is massive - no damage is done. Following crews enjoy the spectacle of a big daddy-long-legs, slowed down by the dangling forks and half-open doors. It can take quite a while before the penny drops in the cockpit concerned."

Incedentally the yellow line he mentions was a line painted on the cowling which was what they used as a bomb sight.

 

[VBF-13]

Enjoyed this very much. A few observations. Going in groups of six was pretty much standard all around from what I understand. You'll note the five planes in my negative, and that you see five in many such photos. The sixth was operating the camera from the second seat. On the accuracy of a vertical dive, again, I don't know that it was any the more accurate. If you'll look at how this pilot describes his virtual immunity from fire while in the vertical dive, yeah, that's probably one of the reasons, one of the advantages of those dives, over the more lateral dives. Or, such would make sense. Finally, on the pulling out, that's quite literally a "pull" (hence, the characterization). Those vertical dives had to be the most demanding, though, not only on the pilot and crew, but on the plane, we'll definitely give them that.

 

[stona]

Is an aircraft that dives at 90 degrees inherently more accurate than one that dives at 60 degrees?

According to the 8th AF the answer is yes.

Despite this a compromise dive angle of 60 degrees was generally adopted.

Cheers

Steve

 

[tomo pauk]

Great contribution, many thanks, people

 

[VBF-13]

The Navy pilots I know trained at 60 but it wasn't uncommon once they got the hang of it to dive at 70 when the situation dictated. As Ascent showed us, the steeper the dive, the harder they were to hit.

 

[VBF-13]

Steve, maybe that's because the P-47s were "adapts?" Maybe that's the only way they knew how to get the bomb on target in those things, i.e., letting go of it going straight down. I'm just speculating.

 

[stona]

Steve, maybe that's because the P-47s were "adapts?" Maybe that's the only way they knew how to get the bomb on target in those things, i.e., letting go of it going straight down. I'm just speculating.

The P-47 was of course not a "natural" dive bomber,but I think the principal applies to dive bombing in general.

As early as 1934 the Flygvapnet (Royal Swedish Air Force) had conducted dive bombing tests with three Hawker Harts,purchased from the RAF. In this biplane they established an 80-85 degree dive angle to be the most accurate.

The Luftwaffe too discovered that "near vertical" dives gave the best results but most attacks by Ju 87s appear to have been delivered in a dive of about 70 degrees. There is a diagram in a Junkers handbook,which has been variously reproduced,illustrating different pull outs with or without dive brakes which shows an angle closer to 80 degrees. Unfortunately I can't scan it at the moment.

Cheers

Steve

 

[VBF-13]

Steve, but think it out. There could be any number of reasons for the facts you just related. For one, the biplanes wouldn't want to come in broad. At that snail's pace under any kind of fire encountered they'd likely get torn to pieces before they got anywhere near their drop point. The P-47s, they didn't train in dive-bombing for two months, and neither was that aircraft suited to brake, as were the SBDs, to maneuver into position for the broader drops. The Navy pilots, by contrast, did train for two months, and in every aspect, imaginable. By the time they were dive-bombing, which consisted of some 15 or so days of that training, they were going up two-hours at a hop, and making five runs and drops at their targets. It's all in the release, right? You want to throw strikes, for the curveball, that's different than for the fastball? The same logic, here. It's just different drop points. You're trained on a 60 degree dive and you want to combat on a 70 degree dive, it's mathematics, that's all, and you're there.

Respectfully, don't accept everything you read, just because it's from a good source. Scrutinize the substance of it, then draw your inferences. A 60 degree dive is just a different drop point. That's all. Put another pitcher in there, he's unfamiliar with that pitch, fine. Throw it the way he wants, so long as he gets it there. But don't discredit two months of putting those bombs on the nose just because he never had it. People unfamiliar might believe him. That's what's wrong with that.

PS: Then it might get into Wikipedia, and everybody will believe it.

 

[J.A.W.]

Although design-capable of divebombing, the Do 217 was the 1st aircraft to sink a battleship at sea [the Roma, which was located/examined recently] using diabolical Nazi smart-bomb [Fritz-X] technology, Stukas did n't quite get there with capital ships..

the Hellcats had no trouble smothering the Yamato et al with bombs rockets , seemed to make the Helldiver [but not the torpedo Grummans]somewhat redundant..

 

[VBF-13]

J.A.W., the Hellcats were crackerjack dive-bombers, and the pilots got a lot of training in that aspect, too. EDIT: They were bombing-fighting aircraft, by design.

 

[tyrodtom]

Although design-capable of divebombing, the Do 217 was the 1st aircraft to sink a battleship at sea [the Roma, which was located/examined recently] using diabolical Nazi smart-bomb [Fritz-X] technology, Stukas did n't quite get there with capital ships..

the Hellcats had no trouble smothering the Yamato et al with bombs rockets , seemed to make the Helldiver [but not the torpedo Grummans]somewhat redundant..

You're forgetting about the HMS Prince of Wales, a battleship sunk at sea by the Japanese airpower alone on Dec.10th 1941, several years before the Roma.