High Alt Bombers vs Dive Bombers

[comiso90]

The Japanese used both high altitude bombers and dive bombers on the Pearl Harbor raid.

Why?

It seems to me that dive bombers would offer greater accuracy, penetration and pilot survivability why then use high altitude bombers?

Could the high alt bombers carry greater loads?

Was it just part of a coordinated attack and gave the enemy one more thing to worry about?

.

 

[HoHun]

Hi Comsio,

>Why?

Because the Nakajima B5Ns were part of the standard carrier complement and not capable of dive bombing.

They were capable of torpedo bombing though, which was important in anti-ship operations, even at Pearl Harbour.

The Imperial Navy would not have left the B5N out of the complement for more dive bombers because they might still have been needed if the surprise failed and the US fleet would have been met at sea.

Regards,

Henning (HoHun)

 

[drgondog]

The Japanese used both high altitude bombers and dive bombers on the Pearl Harbor raid.

Why?

It seems to me that dive bombers would offer greater accuracy, penetration and pilot survivability why then use high altitude bombers?

Could the high alt bombers carry greater loads?

Was it just part of a coordinated attack and gave the enemy one more thing to worry about?

.

The latter. The primary strike force was the Torpedo and IIRC the level bombing was designed to split air defense (had it really existed) reaction or, best case draw from the Torp strike. I think the horizontal bombing was done below 5,000 feet

Exceptional planning and execution by the Japanese - thank God the carriers were out of town.

 

[comiso90]

Thanks for the answers..

was the TBF ever used as an antishipping high alt bomber?

.

 

[drgondog]

Thanks for the answers..

was the TBF ever used as an antishipping high alt bomber?

.

It sure wasn't common practice.. the SBD and SB2C were primary bomb carrying a/c for the navy. The TBF could carry iron bomds and did so when the mission was beach suppression - so it is entirely possible a japanese ship was caught in between as a target of opportunity... but a strike against Jap ships would be a torp mission for TBF.

I don't think 'high altitude' meant the same to USN as it did to USAAF. The Navy had land based patrol bombers capable of higher altitude strikes but that wasn't their primary mission either. As far as I know, until nucs came into the inventory the USN never considered any level bombing from medium or high altitudes... even the A4 was primarily a 'toss bomb' type with a nuc to stay under radar cover.

The USN was all about 'up close and personal' with precison strikes.

 

[comiso90]

It sure wasn't common practice.. the SBD and SB2C were primary bomb carrying a/c for the navy.

If the Japanese thought there was value to using the Nakajima B5Ns as a high alt bomber I wonder if the US had similar thoughts for the TBF.

 

[syscom3]

The Japanese "Val" dive bombers only carried a 500 pound payload. That's pretty poor compared to the SBD that could carry a 1000 pounder.

The Kate torpedo bombers COULD carry the 1600 pound AP bombs, so they were pressed into service for the horizontal bombing role.

Also remember, many of the capital ships at Pearl were double moored or protected by drydocks and port facilities. Adding more torpedo bombers wasn't going to add any more to the damage that already had been done.

 

[syscom3]

If the Japanese thought there was value to using the Nakajima B5Ns as a high alt bomber I wonder if the US had similar thoughts for the TBF.

George Bush #1 was shot down in his TBF while on a horizontal bomber mission.

 

[davparlr]

The inboard row of battleships at Pearl would have been protected from torpedo attacks leaving only vertical bombing, either high altitude or dive. As reported by syscom3, the dive bombers did not have the hitting power of the high altitude bombers. I am sure the Japanese wanted to get the heavy armor piercing bombs the Kates could carry onto the decks of the inboard ships. It turns out that high alitude bombers could be quite effective on moored ships, like the Tirpitz. Their plan worked quite well.

 

[kool kitty89]

I'm not sure "High Altitude Bomber" would be the correct term for this comparison. Level bomber, yes, but all the aircraft mentioned would be (almost always) performing at medium altitudes. (~10-15,000 ft)

 

[syscom3]

I'm not sure "High Altitude Bomber" would be the correct term for this comparison. Level bomber, yes, but all the aircraft mentioned would be (almost always) performing at medium altitudes. (~10-15,000 ft)

Yes, the torpedo bombers were employed as "level bombers" at low altitudes, occasionally medium, as a regular part of their ops.

 

[davparlr]

I'm not sure "High Altitude Bomber" would be the correct term for this comparison. Level bomber, yes, but all the aircraft mentioned would be (almost always) performing at medium altitudes. (~10-15,000 ft)

I would agree that "level bombing" would be more appropiate.

 

[JoeB]

TBF's were equipped with Norden bombsights for medium altitude level bombing. The radio operator/belly gunner operated it acting as bombardier when it was used. However they relatively seldom did use such a tactic. One example is Battle of the Eastern Solomons in August '42 when TBF's made some 10+ k ft bomb runs on Japanese warships. They missed, and that's the reason the tactic was seldom used. TBD's had also carried bombsights.

When TBF's glide bombed, which they did a lot more often than they actually dropped torpedoes, especially considering land targets too, the pilot was the bombardier, and did it by eye.

In contrast to US air arms, the Japanese got more than a few hits on moving ships with medium altitude level bombing. Type 97 Carrier Attack Planes ('Kate') did it v US and Dutch DD's in NEI, merchant ships there and in Indian Ocean in April 1942 raids, etc. Type 1 Land Attack Planes ('Betty') sank the seaplane tender, ex-carrier Langley that way, and 'Rikko' also scored bomb hits, though not critical, in the attacks on Repulse and PoW. US a/c did it more rarely, eg. B-17's sank one moving merchant ship in prelude to Battle of Bismark Sea with medium altitude attack, but most or all other such hits by US were v anchored or otherwise stationary ships (eg. Japanese DD stopped to pick up survivors near Guadalcanal sunk by B-17's).

Joe

 

[timshatz]

One reason the Japanese might've used Kate's in the horizontal role (beyond the abilitiy to carry the 1600lb bomb, beyond the ability of the Val-and that may be the only reason but I'll go out on a limb anyway) could be the penetrating ability of a 1600lb bomb dropped at 5K feet vs a 800lb bomb dropped at 1500 ft from a dive bomber.

I'm not an engineer, but the penetrating capabilities of the larger bomb coming from a higher altitude might be greater against armor than the bomb coming from a dive bomber.

Anybody know the math on such a situation?

 

[drgondog]

One reason the Japanese might've used Kate's in the horizontal role (beyond the abilitiy to carry the 1600lb bomb, beyond the ability of the Val-and that may be the only reason but I'll go out on a limb anyway) could be the penetrating ability of a 1600lb bomb dropped at 5K feet vs a 800lb bomb dropped at 1500 ft from a dive bomber.

I'm not an engineer, but the penetrating capabilities of the larger bomb coming from a higher altitude might be greater against armor than the bomb coming from a dive bomber.

Anybody know the math on such a situation?

1. For the dive bomber (in a vertical dive to simplify the math)
V^^2= Vdb^^2+2*g*s

s=1/2*(Vdb+Vt)t

where Vdb = dive velocity at release, g=acceleration of gravity, s=altitude, Vt= terminal velocity.

2. For level bombing the above still works except that Vdb=0 as the a/c is flying level and the initial vertical velocity = zero.

Level bombing at 5000 feet example
If you know the altitude of the level bomber you can solve for the time of the bomb in flight

s= .5*g*t^^2 where s = altitude and t=time

t=sqrt(s/.5g)

This assumes no drag for precision but close enough for low to say 5000 feet

at 5000 feet ---> t= 17.63 sec for bomb to hit for level drop

In 17.63 sec, the bomb reaches a velocity of 566 ft/sec = 385 mph

Dive bombing in Vertical dive at 385mph
For a dive bomber at 385 mph in a vertical dive at 5,000 feet drop
V^^2 = Vdb^^2+2*g*s
V= sqrt(566^^2 + 2*32.107*5000) = sqrt(566^^2+321,070)= 801 ft/sec
V= 546mph

This ignores drag of the bomb but for that altitude it won't be off too much (if I did the math correctly) as most bombs were more areodynamically sound in transonic than aircraft so the drag rise would not be as much in the 400-550mph range.

This demonstrates for medium altitude at same release point altitude that the dive bomb is at significantly higher velocity as the horizontal bomb release - thereby having a lot more kinetic energy at impact

Edit - Tim if I had paid more attention to your example I would have solved for both cases.

For you to do the solution you need to assume a vertical dive velocity (easier to assume vertical) for the dive bomber
at 1500 feet.. then when you get the terminal velocity multiply the terminal velocity of the 1600 pound bomb (385mpg) times the mass of the 1600 pound bomb and compare with the terminal velocity and mass of the 800 pound bomb.

KE =1/2* m*V^^2. You can see that the velocity of the 800 pound bomb dropped at 1500 feet has to be at 1.414 times the velocity of the 1600 pound bomb to have the same KE at impact (ignore the explosive amount).

 

[syscom3]

The AP bombs dropped by the IJN level bombers were converted AP shells used by their BB's.

 

[comiso90]

TBF's were equipped with Norden bombsights for medium altitude level bombing. The radio operator/belly gunner operated it acting as bombardier when it was used. However they relatively seldom did use such a tactic. One example is Battle of the Eastern Solomons in August '42 when TBF's made some 10+ k ft bomb runs on Japanese warships. They missed, and that's the reason the tactic was seldom used. TBD's had also carried bombsights.



Joe

Thanks for that

 

[Timppa]

The AP bombs dropped by the IJN level bombers were converted AP shells used by their BB's.

Reminds me of the quote of "Good Morning, Vietnam":
"Adrian Cronauer: "Excuse me, sir. Seeing as how the V.P. is such a V.I.P., shouldn't we keep the P.C. on the Q.T.? 'Cause if it leaks to the V.C. he could end up M.I.A., and then we'd all be put out in K.P. "
<Sorry, totally off- topic >

PS. I know the abbreviations, just funny

 

[No_Nickname]

Wasn't it a japanese high alt bomber that hit the Arizona's turret which caused the chain reaction that sunk it?

 

[timshatz]

1. For the dive bomber (in a vertical dive to simplify the math)
V^^2= Vdb^^2+2*g*s

s=1/2*(Vdb+Vt)t

where Vdb = dive velocity at release, g=acceleration of gravity, s=altitude, Vt= terminal velocity.

2. For level bombing the above still works except that Vdb=0 as the a/c is flying level and the initial vertical velocity = zero.

Level bombing at 5000 feet example
If you know the altitude of the level bomber you can solve for the time of the bomb in flight

s= .5*g*t^^2 where s = altitude and t=time

t=sqrt(s/.5g)

This assumes no drag for precision but close enough for low to say 5000 feet

at 5000 feet ---> t= 17.63 sec for bomb to hit for level drop

In 17.63 sec, the bomb reaches a velocity of 566 ft/sec = 385 mph

Dive bombing in Vertical dive at 385mph
For a dive bomber at 385 mph in a vertical dive at 5,000 feet drop
V^^2 = Vdb^^2+2*g*s
V= sqrt(566^^2 + 2*32.107*5000) = sqrt(566^^2+321,070)= 801 ft/sec
V= 546mph

This ignores drag of the bomb but for that altitude it won't be off too much (if I did the math correctly) as most bombs were more areodynamically sound in transonic than aircraft so the drag rise would not be as much in the 400-550mph range.

This demonstrates for medium altitude at same release point altitude that the dive bomb is at significantly higher velocity as the horizontal bomb release - thereby having a lot more kinetic energy at impact

Edit - Tim if I had paid more attention to your example I would have solved for both cases.

For you to do the solution you need to assume a vertical dive velocity (easier to assume vertical) for the dive bomber
at 1500 feet.. then when you get the terminal velocity multiply the terminal velocity of the 1600 pound bomb (385mpg) times the mass of the 1600 pound bomb and compare with the terminal velocity and mass of the 800 pound bomb.

KE =1/2* m*V^^2. You can see that the velocity of the 800 pound bomb dropped at 1500 feet has to be at 1.414 times the velocity of the 1600 pound bomb to have the same KE at impact (ignore the explosive amount).

Thanks Dragon, I appreciate the math.

So the dive bomber gives it more speed, imparting more energy at the hit point. But the projectile is smaller (talking the Pearl Harbor bombing here) so the 1600lb bomb might hit with about the same amount of energy as the 800lb bomb.

What about weight against armor and penetrating ability. Will a heavier bomb retain more penetrating ability once it penetrates the deck armor and allow it to penetrate the magazine armor? Does the deck armor take more energy away from a smaller bomb than a large one?