SBD dive bombing procedures

[AZRailwhale]

Thanks! Looking forward to any illumination.

To expand a bit: I'm a recently retired former attack guy (A-4/AV-8) who suddenly has plenty of time to catch up on my guilty pleasure of WWII historical reading. Thumbing through Shattered Sword, I saw several apparently widely accepted revisions to the familiar Midway narrative. But some of the specifics seem to me questionable, or at least not what I'd assumed, and some of it is in the most critical part of the battle.

For example, the description of the attack on Akagi has two claims I find hard to credit: 1) Best's section bombed in close formation; 2) we know who dropped the bomb that scored the fatal hit. On the first point, I've never even heard of anybody dive bombing in formation, and Best's after action says "The first section of the first division joined up immediately after pull-out from the dive." Which implies they'd separated. On the second point, the rationale from Shattered Sword was his backseater's quote "Nobody pushed his dive steeper or held it longer than Dick." In fact, in standard dive-bombing, a steep fast dive held to lower than planned altitude will always result in a long hit, and many duds.

However, it is possible for this to be a correct description. There are modern gunsights that rely on angle change to the target (e.g., ARBS), and with enough practice, and a relatively slow and low delivery, the human eyeball could probably come up with a comparable solution. In that case, there is no hard release altitude, you just have to pull out in time to avoid ground impact, and hope the bomb has time to arm. On that point, there are also contemporary reports of armorers spinning bomb fuze vanes prior to loading (to reduce bomb arming times). And while all this strikes me as ridiculously nonstandard and dangerous (especially loading partially armed bombs on carrier aircraft), there may have been various cowboy solutions to a procedures vacuum.

Anyway, I'm stuck with two incompatible interpretations, and I'd love any input on which was correct.

Well we absolutely know from history that Best flew when he knew he had damaged lungs from contaminated oxygen in the first attack, so encouraging a "cowboy" attack aid seems like a risk he would take, he had to know the second sortie would be his last attack ever.

 

[Retattack]

It's an Occam's Razor thing. Of course, I'm no pilot, so your apparent disagreement, informed by your personal experience, is one more datum for me to take into account. Thanks for speaking it.

You're welcome. And to be clear, I'm not at all sure that interpretation is wrong . . . I'm just not convinced you can draw it from the available evidence. The main point here, elided in the various descriptions, is that in dive bombing (and in fact bombing in general), you can either fly formation: looking at your lead and dropping when he drops (or some prearranged signal), or you can aim your own bomb. Doing both at the same time isn't possible (and even less so when we're talking about a bomb sight that's a glorified rifle scope).

The description in the book appeared to suggest the former, and used that to draw conclusions. I was struck by that particular passage because, in my experience and for many reasons, the latter is the only thing that made sense. I'm now convinced the latter is in fact what occurred, and any conclusion drawn from the incorrect inference are suspect. YMMV, and no disrespect to those who choose to interpret the data differently.

 

[GrauGeist]

As an aside, a family friend, who was attached to VSB-6 (USS Enterprise), mentioned that he and other SBD pilots used the Hinomaru (Rising Sun emblem) or elevators on the Japanese carriers' flight deck, as aim points.

If they were attacking other ships, they would focus on features that stood out and offered the best possible strike results, like smoke-stacks (funnels), superstructures and such.

Their objective was to inflict as much damage as possible and if the ship sank, that was a bonus.

 

[pirate_smee]

Does anyone have the specific dive procedures followed by Dauntless pilots in the beginning of the war (Coral Sea and Midway)? I'm particularly interested in release height, target airspeed and dive angle, and whether the sight had a fixed depression or was adjustable, and what the assumptions were for the sight.

Are there any training manuals, ballistics tables or the like?

(I'm trying to make sense of various accounts of Midway, and having a hard time reconciling them . . . first time poster, apologies for inadvertent gaffes.)

Look at this websites:

SB Dive Bomber

www.globalsecurity.org

DIVE BOMBING

A blog to correct misunderstanding of the technique of World War II dive bombing, offered by a dive bomber pilot and endorsed by surviving veterans.

divebombingnavy.blogspot.com

Dive Bombing: The Naval Air War In The Pacific

www.daveswarbirds.com

 

[PStickney]

Not exactly. The central hit and the two near-misses were about 300 or so foot from each other to either side lengthwise, and also separated abeam -- the bow near-miss over, the central hit, and the stern near-miss an undershot.

Given the low release altitude, I doubt there's so much windage that Best's bomb and either of his wingmen's crossed paths to that extent, unless they were themselves flying different dive courses. But they were all coming in from starboard abeam, if I remember rightly. What are the odds that their dives are that divergent, that bombs go both long, short, and askew?

It's an Occam's Razor thing. Of course, I'm no pilot, so your apparent disagreement, informed by your personal experience, is one more datum for me to take into account. Thanks for speaking it.

There's the thing, though - Of you don't have the slip/skid ball centered, the bomb isn't going to fall straight. At those speeds, it doesn't take a lot of rudder to get the nose out of line. That will push the bomb's trajectory off.
Check out the evolution of gun/bomb sights as they progressed through the 1940s through today - they've put a lot of effort into (From the '40s to the '60s) making sure that the sight picture is better at telling you when to drop (Depressed Reticle) - 1950s, to aircraft attitude - The sights of the F-4 and F-105, (And maybe the A-4, Not quite my area) - to the CCIP of the A-7 and later, which shows you where your bombs hit the ground, no matter what you're doing.
A bomb dropped outside of coordinated flight goes where Newton and Bernoulli send it.

 

[AZRailwhale]

As an aside, a family friend, who was attached to VSB-6 (USS Enterprise), mentioned that he and other SBD pilots used the Hinomaru (Rising Sun emblem) or elevators on the Japanese carriers' flight deck, as aim points.

If they were attacking other ships, they would focus on features that stood out and offered the best possible strike results, like smoke-stacks (funnels), superstructures and such.

Their objective was to inflict as much damage as possible and if the ship sank, that was a bonus.

Judging from the hits on the RN's ABH carriers, the Luftwaffe used the elevators as aiming points. I don't know if they realized the elevators were lightly armored or not, but they made decent aiming points based upon the bomb damage,

 

[SaparotRob]

Look at this websites:

SB Dive Bomber

www.globalsecurity.org

DIVE BOMBING

A blog to correct misunderstanding of the technique of World War II dive bombing, offered by a dive bomber pilot and endorsed by surviving veterans.

divebombingnavy.blogspot.com

Dive Bombing: The Naval Air War In The Pacific

www.daveswarbirds.com

View attachment 766213View attachment 766211

The second article stated that neither the Val nor the Stuka could dive as steeply as the SBD. Is that correct or half correct?

 

[GrauGeist]

The second article stated that neither the Val nor the Stuka could dive as steeply as the SBD. Is that correct or half correct?

Incorrect.

The SBD dove (typically) at 70 to 75 degrees.
The D3A dove (typically) at 65 degrees, sometimes steeper, depending in circumstances.
The A-36 was limited to a max. 70 degree dive.

The Ju87 dove at angles from 60 degrees to 90 degrees.

Unlike the A-36, D3A and SBD, the Stuka had an autopilot that pulled the aircraft out of the dive and restored level flight while the pilot was "grayed out".

The resulting G-forces from steep dives increased the steeper the dive was. A 90 degree dive would actually create a "black out" which would be fatal if not for the Ju87's autopilot.

 

[SaparotRob]

Incorrect.

The SBD dove (typically) at 70 to 75 degrees.
The D3A dove (typically) at 65 degrees, sometimes steeper, depending in circumstances.
The A-36 was limited to a max. 70 degree dive.

The Ju87 dove at angles from 60 degrees to 90 degrees.

Unlike the A-36, D3A and SBD, the Stuka had an autopilot that pulled the aircraft out of the dive and restored level flight while the pilot was "grayed out".

The resulting G-forces from steep dives increased the steeper the dive was. A 90 degree dive would actually create a "black out" which would be fatal if not for the Ju87's autopilot.

That's what I thought.

 

[GrauGeist]

I should add that.when the SBD "pushed over", there would be a point in time where it might have been in a 90° position for a few moments, until the pilot acquired the target, adjusted the blower and lowered the dive flaps, then adjusted the dive angle to 70 (or so) degrees.

But it was not a true or sustained 90° dive.

 

[pirate_smee]

Check out the evolution of gun/bomb sights as they progressed through the 1940s through today - they've put a lot of effort into (From the '40s to the '60s) making sure that the sight picture is better at telling you when to drop (Depressed Reticle) - 1950s, to aircraft attitude - The sights of the F-4 and F-105, (And maybe the A-4, Not quite my area) - to the CCIP of the A-7 and later, which shows you where your bombs hit the ground, no matter what you're doing.
A bomb dropped outside of coordinated flight goes where Newton and Bernoulli send it.

That's not quite correct. CCIP is a great help but until the 1990 / 2000 you still had to compensate for wind also on most systems you had to fly with the wings level.
In some Aircraft like the Viggen you could manually set the wind direction and speed for the sight, but was not practical on moving targets.
These early computers needed a few seconds to recalculate the sight.
Also most of them used still the barometric height over the target, not an radar altimeter.
The A-4 had a very early CCRP , give it a try in DCS and the freeware A-4E-C Mod.

View: https://www.youtube.com/watch?v=Qpe-xaXsx8g&themeRefresh=1
Dive bombing needs a lot of training and under battle conditions with flak it's a hole another story, as it's deadly to fly straight and alone.
If you attack in a team you have to look out that you don't crash into each other.
Flight sims like IL-2 BOS and DCS can give you some insight in dive bombing, sadly no SBD since IL-2 1946.

View: https://www.youtube.com/watch?v=CZK65tb2qIU

View: https://www.youtube.com/watch?v=65Jw-CkRq3w
Me-410 Stuvi (Sturzvisier / dive sight)

View: https://youtu.be/lLjHhWehB8w?feature=shared&t=347

 

[Retattack]

Look at this websites:

SB Dive Bomber

www.globalsecurity.org

DIVE BOMBING

A blog to correct misunderstanding of the technique of World War II dive bombing, offered by a dive bomber pilot and endorsed by surviving veterans.

divebombingnavy.blogspot.com

Dive Bombing: The Naval Air War In The Pacific

www.daveswarbirds.com

View attachment 766213View attachment 766211

This is fantastic, and with the website, gives a great overview of the mechanics. I've seen about five different variants of this picture, and in each the details are slightly different. In most cases they don't matter much (e.g., accounts agree the Midway bombers climbed to 20,000' initially, and VB-6 descended to 15,000' because of oxygen problems . . . but whether the initial altitude is 14K', 15K', or 20K', is largely irrelevant to the outcome). But the numbers on the bottom do matter, at least for accuracy's sake, and are remarkably difficult to nail down.

With a fixed sight, there is one correct total trajectory drop (basic ballistics). So if 70 deg/240KIAS/3000' gives a bullseye for a particular type of bomb, any steeper, faster, or lower release will be long--and shallower, slower, or higher, will be short. I'm not sure what those numbers should be, but they can't be both 3000' and 1000' for the same speed and angle, which is where most of the variance comes in. (Caveat: later models may have had variable sights, which could.)

For various reasons, I suspect the correct release altitude was probably close to what ThomasP calculated above (i.e., 3000-2500'). A modern GP bomb throws shrapnel up to about 3000' and I'd expect the older bombs to be slightly less energetic. Some of that is absorbed into the target and the aircraft effectively outruns some of the effects, but the arming time on the bomb is designed to keep the aircraft from fragging itself, so that'd be the ballpark to avoid a dud. Release numbers less than 2000' strike me as dubious, but again, I'd love to see any authoritative reference on the ballistics.

 

[Retattack]

That's not quite correct. CCIP is a great help but until the 1990 / 2000 you still had to compensate for wind also on most systems you had to fly with the wings level.
In some Aircraft like the Viggen you could manually set the wind direction and speed for the sight, but was not practical on moving targets.
These early computers needed a few seconds to recalculate the sight.
Also most of them used still the barometric height over the target, not an radar altimeter.
The A-4 had a very early CCRP , give it a try in DCS and the freeware A-4E-C Mod.

Yes, and there are lots of different systems out there solving basically the same problem different ways, and they all change over time, even in the same aircraft. I flew A-4Ms in the early 80's, and they were in transition from baro bombing to ARBS (the pilot selected the desired bombing system). The HUD showed airspeed and altitude, and had a gyro stabilized sight, so you could drop in a minimal angle of bank. In basic baro, the pilot inputs target elevation and release height and sight depression angle, and the aircraft cues when release altitude is reached (at predetermined airspeed and dive angle). In baro CCIP, the computer accounts for speed, dive angle, and current (baro) altitude . . . the pilot selects target altitude and wherever the diamond is, is where the bomb should hit . . . but it doesn't account for wind or target motion. The radar altimeter was available for very low dive angles, and was slightly more accurate over level terrain.

With ARBS, the pilot designated the target with a dual mode tracker (laser and contrast), and with a target lock, the aircraft effectively calculated relative motion, and theoretically accounted for steady state windspeed and target motion (everything except acceleration). The problem with the A-4 is that it had an Air Data Computer that actually had wheels in it, so the bombing system was dealing with so much garbage input that it wasn't very reliable, and the contrast seeker was limited to day VMC. Later the same system was on early (pre-radar) AV-8Bs with INS and digital ADC data, with vast improvement. GPS came along about 1990, which effectively removed INS drift (which the aircraft interprets as wind and has a minor but noticeable effect on accuracy).

I'm not really up on the modern stuff . . . they were just getting radar and JDAMs when I retired . . . but even modern bombing systems need some input on the target, usually by locking with radar or targeting pod. Anyway, bombing accuracy is getting less critical with the trend toward smarter bombs and longer slant ranges. AFAIK, all GP bombs now have the bolt-on JDAM guidance kits, so slinging dumb bombs is becoming a useless skill.

 

[GrauGeist]

We've come a long way in the past 100 years and it all started by dropping hand grenades and mortar shells from the cockpit!

 

[special ed]

Still dropping grenades, without a cockpit in Ukraine

 

[GrauGeist]

Still dropping grenades, without a cockpit in Ukraine

Yep, it almost seems that all the elements (and idiotic follies) of warfare in the 20th century are being replayed in Ukraine.

BTW, not only grenades, but mortar shells are being dropped by drones.

 

[Retattack]

The resulting G-forces from steep dives increased the steeper the dive was. A 90 degree dive would actually create a "black out" which would be fatal if not for the Ju87's autopilot.

Just to be clear, the G-forces are in the pullout, not the dive. And it's correct that for any particular release height, the required pullout forces increase (and it's more pronounced at steeper dive angles and higher airspeeds, because you're eating up a lot of altitude in the first part of the recovery while the nose is buried). But the G force on any diving aircraft starts close to zero in a pushover, and gently increases as the acceleration slows due to air friction. And the G for any steady-state dive is exactly 1. (Some component of it just happens to be eyeballs-out or negative, which is generally uncomfortable.) As the old saying goes: "it's not the fall that kills you, it's the sudden stop at the end." If you really wanted more dive angle, you could always just increase the release height to give more room for the pullout . . . it just might end up with an impractical slant range.

I was somewhat surprised to see the chart showing the Dauntless had a negative AOA (4-5 deg nose down) in the dive. AFAIK, all modern aircraft would have a similar nose up AOA, which makes it a lot more comfortable. The perceived dive would be about 10 degrees steeper (with corresponding increase in the negative G component). And even if you aren't approaching the structural limit, many aircraft have a zero or negative G time limit (usually to keep gravity fed oil and fuel pumps from sucking air).

At steeper dive angles, there are problems with aircraft separation and interbomb colllisions. A modern bomb rack has a CAD that activates an ejector foot and pushes the bomb away from the aircraft. The Dauntless had a "trapeze" rack for the same basic purpose, but it obviously needs some positive G force to work (and to avoid dropping the bomb through the propeller). Not sure if it was true in WWII, but modern ordnance deliveries are generally limited by what was tested (i.e., if it hasn't been tested, you aren't allowed to do it).

 

[GrauGeist]

When the SBD "pushed over", there was actually negative Gs.

Several accounts by rear-gunners stated that loose gear in the cockpit was observed "floating about" until the dive angle was acquired.

Other types of Dive-bombers used different dive profiles like the Ju87, which would wing-over at a parallel point to their target (or close to it) and enter their near vertical dive.

As for my earlier statement about G-forces from steep dives: I stated "resulting G-forces from steep dives", meaning the effects experienced during the dive pull out proceedure.

I didn't realize that some may have thought otherwise...

 

[PStickney]

Incorrect.

The SBD dove (typically) at 70 to 75 degrees.
The D3A dove (typically) at 65 degrees, sometimes steeper, depending in circumstances.
The A-36 was limited to a max. 70 degree dive.

The Ju87 dove at angles from 60 degrees to 90 degrees.

Unlike the A-36, D3A and SBD, the Stuka had an autopilot that pulled the aircraft out of the dive and restored level flight while the pilot was "grayed out".

The resulting G-forces from steep dives increased the steeper the dive was. A 90 degree dive would actually create a "black out" which would be fatal if not for the Ju87's autopilot.

It wasn't an autopilot - It was a switch set to trip when the airplane reached a certain altimeter reading. Tripping the switch initiated retracting the dive brakes, and moved the elevator trim tab from teh position that the pilot had set it to maintain the dive. The natural stability of the re-trimmed airplane would then pitch the nose up.
G Forces aren't a function of your dive angle, but how hard you're hauling back on the stick. If you're pulling out at the proper height - As in you don't want to be blown up by your own bomb, or become every AAA Gunner's favorite target, you start your pullout at a height pre-figured to have you bottoming out at a sufficient altitude. Normal pullouts were on the order of about 4 Gs, although the temptation to pull harder is strong.

 

[GrauGeist]

It wasn't an autopilot - It was a switch set to trip when the airplane reached a certain altimeter reading. Tripping the switch initiated retracting the dive brakes, and moved the elevator trim tab from teh position that the pilot had set it to maintain the dive. The natural stability of the re-trimmed airplane would then pitch the nose up.
G Forces aren't a function of your dive angle, but how hard you're hauling back on the stick. If you're pulling out at the proper height - As in you don't want to be blown up by your own bomb, or become every AAA Gunner's favorite target, you start your pullout at a height pre-figured to have you bottoming out at a sufficient altitude. Normal pullouts were on the order of about 4 Gs, although the temptation to pull harder is strong.

The Automatic Dive Recovery System also opened the throttle and levelled off on the horizon - all activated by the switch on the control column.

Since we weren't discussing the Ju87 in detail, autopilot was good enough. Especially since the Automatic Dive Recovery System was in control of the aircraft during the pilot's inability to maintain control.

And the steeper the dive, the greater the G-force on recovery. The Stuka crews experienced up to 6 Gs from their near 90° dives, which would be much greater than a D3A's 65° (+/-) dive recovery.