Why was the SBD such an effective aircraft?

[michael rauls]

Nice. Thanks for providing. FWIW, the SBD-3s and 5s had no problem carrying a 1000# bomb, and that's just a fact, and I've the bombing practice logs on both those as source for that.

Ya, that's what I've always read, that 1000 pounders were pretty commonplace for SDBs in all but the earliest versions but hey I'm no expert so I'm just reading the posts of everyone with an open mind.

 

[Shortround6]

The SBD-3 was limited to 1,200 max. bombload (1,000 centerline and 100 lb. under each wing) but the SBD-5 had a max. of 2,250 bombload (1,600 centerline and 325 lb. under each wing).

I believe it has been mentioned before but the 1600lb bomb was only slightly rarer than hen's teeth. An Essex class carrier might only have 20 in the magazines. An unless you were attacking a battleship it was pretty useless (it's HE filling was less than a 500GP bomb) Of course the 2000lb GP bomb was just about as rare.
The navy also had no 325lb bomb, they had a 325lb depth charge so the famous 2250lb total makes no sense (at least to me) as I have no idea what kind of mission calls for a bomb capable of going through 5-7in of armor deck and yet requires depth charges which won't penetrate much of anything? They won't even land in the same place if dropped together.

This is the load out for the Essex at some point in 1942, the loads changed over the years, so I will include the Enterprise in Oct 1943
ship........................Essex....................Enterprise
100lb GP..............504..........................504
500lb GP..............296..........................288
500lb AP..............---...........................288
1000lb GP...........146..........................378
1000lb SAP.........129..........................378
1000lb AP............110.........................378
1600lb AP.............19............................18
2000lb GP.............19............................18
325lb DB..............296.........................288
100 INC................296.........................288
Torpedoes............36...........................36.

I don't know if there aren't a few typos in that table. Carrying 378 of each different type of 1000lb seems a bit suspicious. Carrying 378 total 1000lb bombs seems a lot more likely.

Just as the much ballyhooed 2250lb load for the SBD seems rather suspect so does the Helldiver claim of carrying twice the bomb load. There are darn few 2000lb bombs compared to the 1000lb bombs for the SBD, the trick reported above for dropping a pair of 1000lb bombs only covers AP and Semi AP bombs and not the GP bombs.

Yes the Hell diver could carry twice the load of GP bombs using the 2000lb bomb but without it the bomb loads become rather similar, although he Helldiver could carry a pair 500lb GP bombs inside.

 

[GrauGeist]

The navy also had no 325lb bomb

Actually, they did.

The Mk 17 was 325 lb. overall with 234 lb. of TNT with either a contact or hydrostatic fuse. Used primarily for ASW, they were also effective against troop transports.
The Mk 41 was a flat-nosed version (same weight, same application).

 

[Shortround6]

It was a depth charge. It may have been effective against troop transports or unarmored in ships (destroyers and escorts) but then the 1600lb bomb would have gone through them without exploding. This weapon was 74% explosive by weight and the GP bombs were about 50% by weight, they had thicker casings but they often broke up on thick armor before exploding. The thin case depth charge needs either an instantaneous fuse (and luck) or a rather weak structure.

They each have their place, just not being carried by the same plane at the same time.

 

[GrauGeist]

As we know, the max. loadout designed into an aircraft is rarely used, but it's there.

Case in point: the B-17 had the ability to carry a maximum of 20,000 pounds of bombs by utilizing it's external racks to augment it's internal stores. This would greatly reduce it's range of course and I don't recall a mission where the B-17 took advantage of this overload.

But the fact remains that it could by design.

 

[RCAFson]

I believe it has been mentioned before but the 1600lb bomb was only slightly rarer than hen's teeth. An Essex class carrier might only have 20 in the magazines. An unless you were attacking a battleship it was pretty useless (it's HE filling was less than a 500GP bomb) Of course the 2000lb GP bomb was just about as rare.
The navy also had no 325lb bomb, they had a 325lb depth charge so the famous 2250lb total makes no sense (at least to me) as I have no idea what kind of mission calls for a bomb capable of going through 5-7in of armor deck and yet requires depth charges which won't penetrate much of anything? They won't even land in the same place if dropped together.

This is the load out for the Essex at some point in 1942, the loads changed over the years, so I will include the Enterprise in Oct 1943
ship........................Essex....................Enterprise
100lb GP..............504..........................504
500lb GP..............296..........................288
500lb AP..............---...........................288
1000lb GP...........146..........................378
1000lb SAP.........129..........................378
1000lb AP............110.........................378
1600lb AP.............19............................18
2000lb GP.............19............................18
325lb DB..............296.........................288
100 INC................296.........................288
Torpedoes............36...........................36.

I don't know if there aren't a few typos in that table. Carrying 378 of each different type of 1000lb seems a bit suspicious. Carrying 378 total 1000lb bombs seems a lot more likely.

Just as the much ballyhooed 2250lb load for the SBD seems rather suspect so does the Helldiver claim of carrying twice the bomb load. There are darn few 2000lb bombs compared to the 1000lb bombs for the SBD, the trick reported above for dropping a pair of 1000lb bombs only covers AP and Semi AP bombs and not the GP bombs.

Yes the Hell diver could carry twice the load of GP bombs using the 2000lb bomb but without it the bomb loads become rather similar, although he Helldiver could carry a pair 500lb GP bombs inside.

In the above examples, neither carrier was equipped with SB2Cs.

Enterprise and Essex could only use the 2000lb bomb via their TBFs, ditto for the 1600lb bomb. SB2C Bomb loads varied more than SBD loadouts because of the greater variety of stores that the SB2C could carry. So, for example, on some missions they would carry 1x 1000lb internally, 1 x 500lb bomb externally and one DT.

During the Yamato sortie at Okinawa here's a partial list of SB2C sorties and bomb loads, according to Smith:

Essex - 12 x 2x1000lb
Yorktown - 13 x 2x1000lb

 

[Shortround6]

In the above examples, neither carrier was equipped with SB2Cs.

ship.......................Bennington 1944 (ship did not see combat until 1945)
100lb GP..............508
500lb GP..............292
500lb AP..............292
1000lb GP...........147
1000lb SAP.........128
1000lb AP............110
1600lb AP.............18
2000lb GP.............18
325lb DB..............292
100 INC................292
Torpedoes............50
3.5 AR...................366
5.0 HVAR.........4,006

!600lb and 2000lbs bombs still constitute a rare payload, The small carriers are even worse.

 

[Conslaw]

ship.......................Bennington 1944 (ship did not see combat until 1945)
100lb GP..............508
500lb GP..............292
500lb AP..............292
1000lb GP...........147
1000lb SAP.........128
1000lb AP............110
1600lb AP.............18
2000lb GP.............18
325lb DB..............292
100 INC................292
Torpedoes............50
3.5 AR...................366
5.0 HVAR.........4,006

!600lb and 2000lbs bombs still constitute a rare payload, The small carriers are even worse.

Shortround, thanks for the useful information. Do you have any statistics on the ordinance carried by escort carriers? especially in the Pacific?

 

[GrauGeist]

I don't have my books for reference at the moment (they're all packed up - did I mention that moving sucks?) but the scouting SBDs would carry at least two bombs on the wings (typically the Mk 17) during their advanced sweep ahead of the fleet, during wartime, they would also carry a 500 lb. GP bomb and would attack any enemy vessel (after reporting) they encountered.

 

[VBF-13]

I don't have my books for reference at the moment (they're all packed up - did I mention that moving sucks?) but the scouting SBDs would carry at least two bombs on the wings (typically the Mk 17) during their advanced sweep ahead of the fleet, during wartime, they would also carry a 500 lb. GP bomb and would attack any enemy vessel (after reporting) they encountered.

This is the point in this thread in which someone brings up these VSB units did glide bomb, as well. Just a different angle at letting these 500s go, but they did train at that, too.

 

[pinehilljoe]

ship.......................Bennington 1944 (ship did not see combat until 1945)
100lb GP..............508
500lb GP..............292
500lb AP..............292
1000lb GP...........147
1000lb SAP.........128
1000lb AP............110
1600lb AP.............18
2000lb GP.............18
325lb DB..............292
100 INC................292
Torpedoes............50
3.5 AR...................366
5.0 HVAR.........4,006

!600lb and 2000lbs bombs still constitute a rare payload, The small carriers are even worse.

Could this load be representative of the mission in 1945? After Yamato was sunk off Okinawa, Nagato was the only heavy ship in the entire IJN. The mission for the carrier wings was support for the landings, and the several raids on the Home Islands. Also by '45 the Carrier Air Wing make up was more fighters than bombers. Bennington's air wing had 74 fighters, 15 SB2Cs, and 15 TBFs. So it makes sense to have larger numbers of ordnance the fighters would normally use.

 

[fliger747]

Vrs Japanese carriers would the AP bombs be better or GP bombs? Enterprise took an AP bomb or two which penetrated or even exited right back out of the hull, but didn't really disrupt flight operations to any serious degree. Some of the CVE's off Samar had 18" AP shells go right through without exploding.

 

[Shortround6]

The 1600lb bomb was designed to go through 5-7 in of deck armor depending on drop conditions (speed and altitude) which is two to three times the thickness of most carrier deck armor. (often the hanger floor was the armored deck?)

the 1000lb AP bomb was supposed to go through a 5in deck if released at 6500ft in a 300kt/60 degree dive. The busting charge was about 150lbs. it was about 12in diameter. the SAP bomb of 1000lbs was 15in in diameter and carried a bursting charge of about 300lbs. The 1000lb MK 44 GP bomb was 18.6 in diameter and used a 595lb filling of TNT.

Are you trying to blow up the hanger and flight deck or get into the engine rooms/magazines?

 

[VBF-13]

I just have a quick question. I don't want to hijack this thread but we have a lot here who know a thing or two about dive bombing. I've seen a lot of footage of the Stukas over Poland, and I'll be darned if many of those don't seem like 80-90 degree dives. The USN I believe had a way of measuring the angles in the training exercises, and I'm pretty sure they wanted them right at around 60. I'm wondering how one comes out of an 80-90 degree dive. Were these Stukas as good as they say? I guess they must have been, unless I'm mistaken about that angle.

 

[Shortround6]

Be careful you are actually comparing the same thing.

there are two angles in dive bombing.
1, the Angle of the plane in relation to the ground. Several dive bombers could adopt a 90 degree attitude.
2. the angle of the flight path in relation to the ground. The wing never stopped producing lift so the dive bomber displaces "upwards" in relation to the planes axis as it dives.

there are a couple of charts in the SBD-3 pilots manual that show this. In a steep dive with the airbrakes out the plane has to have an attitude of around -5 degrees to the line of flight.
At a 90 degree dive the plane actually has to be at 95.5 degrees to the ground. At 60 degrees the plane needed to be at 64.5 degrees.

The steeper the dive the more room/altitude is needed to pull out.

 

[GrauGeist]

The Stukas were designed to dive at a true 90° - the pilot acquired the target and entered his dive and deployed the dive brakes.
At this point,the brake on the Jericho Trumpet(s) was released and then, when the pilot released the bomb and pressed a button on the column, which activated the automatic dive pull-out system.

 

[VBF-13]

L

Be careful you are actually comparing the same thing.

there are two angles in dive bombing.
1, the Angle of the plane in relation to the ground. Several dive bombers could adopt a 90 degree attitude.
2. the angle of the flight path in relation to the ground. The wing never stopped producing lift so the dive bomber displaces "upwards" in relation to the planes axis as it dives.

there are a couple of charts in the SBD-3 pilots manual that show this. In a steep dive with the airbrakes out the plane has to have an attitude of around -5 degrees to the line of flight.
At a 90 degree dive the plane actually has to be at 95.5 degrees to the ground. At 60 degrees the plane needed to be at 64.5 degrees.

The steeper the dive the more room/altitude is needed to pull out.

So I think I see what you're saying. Check me on this if you think I got it wrong, as I'd like to know. The plane's nose in relation to the ground could be 90 degrees. But that's at the start of its dive, high and away from its target. The wings of the plane in that attitude are actually pulling the plane laterally, which is how it ends up in that 90 degree attitude, at its drop point. Is that about the size of it?

 

[Shortround6]

yes.

The plane, in order to fly a 90 degree flight path, actually has to have over a 90 degree attitude.

A 90 degree attitude will result in a mid 80 degree flight path.

This doesn't quite explain what you are seeing in the film footage.

I can speculate and say that a 60 degree dive allows for a lower release point than a 90 degree dive and perhaps the German pilots at times were using the shallower dive for that reason.
Lower altitude allowed for better target identification? or perhaps better aiming of specific target in the target area?

 

[BiffF15]

yes.

The plane, in order to fly a 90 degree flight path, actually has to have over a 90 degree attitude.

A 90 degree attitude will result in a mid 80 degree flight path.

This doesn't quite explain what you are seeing in the film footage.

I can speculate and say that a 60 degree dive allows for a lower release point than a 90 degree dive and perhaps the German pilots at times were using the shallower dive for that reason.
Lower altitude allowed for better target identification? or perhaps better aiming of specific target in the target area?

The steeper the dive angle the the more you reduce it as a variable in the equation. I did bombs (BDU-33s) in the AT-38 and OV-10. We were taught something called tiger errors when we went through AT-38s by the Vietnam era ground instructors (retired fighter pilots). At pickle if you are 1 degree steep (steeper than planned) your error is less than 1 degree shallow. If you are 1 knot fast your error is less than 1 knot slow. Steep, fast and press was the slang catch phrase.

If you were to drop a marble into a pickle barrel from 20 feet directly above it, would it be easier than tossing it in from 20' laterally? How about 100 feet up versus 100' out? When you come straight down you take dive angle out, and to some degree speed as well leaving only wind correction as a variable. The higher the speed the the smaller the impact of the wind due to a reduced time of flight.

Cheers,
Biff

 

[michael rauls]

Those pickle barrels just can't catch a break. First everyone was trying to drop a bomb into one, now marbles as well.