Bomber vs fighter

Shortround6 said:

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No country was rich enough to fire thousands of rockets for each enemy aircraft brought down.
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Maybe I'm doing wrong by quoting a single sentence from a post, but: wonder whether this has any bearing to the Flak shells fired?

tyrodtom said:

Or they could have shot at some intact allied aircraft structures on the ground, and try to guess at how many hits would cause structural failure in flight.

IHO, that 20 rounds of 20mm to bring down a B-17 was just a SWAG.

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could be but since they were were in the best position to eventuate wreckage, in the best position to conduct tests on captured examples ( crash landed or low altitude crash) and had the highest interest in what worked and what didn't their SWAG was probably the best you were going to get. That 20 rounds was also an average, not a minimum. 5-6 rounds into the cockpit would probably do the trick.

pilot claims a heavy / no combat with escorts.

ground crew counts number of shells left.

repeat many times.

Not perfect but would give some idea on how many were needed.

tomo pauk said:

Maybe I'm doing wrong by quoting a single sentence from a post, but: wonder whether this has any bearing to the Flak shells fired?

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well, in this case we are talking about 5" HVAR rockets which used 23.9lbs of propellant, weighed 140lbs apiece and have to be carried aloft (4-12 at a time) by rather expensive fighter aircraft. And this was in 1944, a time when the rounds per AA gun fired per kill were dropping due to radar aiming and in the allied case proximity fuses.

For the Germans and from wiki the 12.8cm flak gun ( shell weight about the same as warhead on the 5in HVAR) and 1125 made " Compared with the 88mm FlaK 18 36, the 128 used a powder charge four times as great which resulted in a shell flight time only one-third as long. This made aim against fast-moving targets much easier" now this may not be strictly true but even if the time of flight to B-17 height was only 25% less you are working in 3 dimensions which means the "hit" rate goes up considerably.

For the US or British a 4.5in or 5in AA gun with radar tracking and proximity fuses would have much better success (using essentially the same "projectile/warhead) and use less propellant (US Navy post war 5in/54 used 19lbs or less) than the unguided, contact fused rockets.

Milosh said:

pilot claims a heavy / no combat with escorts.

ground crew counts number of shells left.

repeat many times.

Not perfect but would give some idea on how many were needed.

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That shows how many were fired, not how many hit. Germans swaged a 2% hit rate for average pilots. which is why they turned against the 20mm gun. a single engine fighter could not carry enough guns and ammo (1000 rounds?) to ensure one kill per flight.

It's plenty if you put them on target and a B-17 is a relatively easy aerial target. However you are likely to run out of ammo after downing a couple aircraft.

Sounds like video game talk.

Greyman said:

Sounds like video game talk.

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Video games/combat sims try to emulate real life and situations.

There may be parallels, but the reality is, a fighter had to get within effective range and still avoid defensive fire. If the fighter loitered too long, he ran the risk of being hit by his target's defensive fire or defensive fore from the other bombers in the group. If the fighter got too close to the bomber while landing hits, it also ran the risk of getting damaged by debris being cast off of the stricken bomber.

At those altitudes, the aircraft was not perfectly stable so the aiming was difficult and your window of effective fire was brief. There was also the problem of limited ammunition per gun, less for cannon. So landing effective hits on a target was not an easy task.

If you watch those videos I posted earlier (especially the second one), they demonstrate the situation pretty well.

Were B-17s more vulnerable from above?

There is only the upper turret protecting that section. Take him out and the upper section is basically undefended.

About turrets - how well could they track fast moving fighters? I suppose it depends how fast and how close.

davebender said:

It's plenty if you put them on target and a B-17 is a relatively easy aerial target. However you are likely to run out of ammo after downing a couple aircraft.

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Again, it would be great to see some facts and figures to back up these claims: do you have concrete evidence that the Japanese were able to shoot down lots of B-17s in 1942, assuming that 60 rounds of 20mm were enough to shoot down at least 2 of them?

wuzak said:

Were B-17s more vulnerable from above?

There is only the upper turret protecting that section. Take him out and the upper section is basically undefended.

About turrets - how well could they track fast moving fighters? I suppose it depends how fast and how close.

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The Bendix chin turret could track from 1/2 degree per second to 33 degrees per second; there doesn't seem to be much info on the speeds of the other turrets:




This is the Bendix 250 series upper turret, which was electrically operated; the B-17 upper turret was a Sperry unit, which (I think) used a hydraulic system:

GrauGeist said:

Very little armor aboard a B-17 or B-24. The only substantially armored B-17 was the YB-40 and with the armor plating and up-gunned configuration, but it was too slow to keep up with the bombers after they delivered their bombs.

The head-on attacks by the Luftwaffe was to kill or incapicitate the pilot/co-pilot and that didn't require tremendous cannon fire, or even lighter caliber MG strikes, as the flight crew were only "protected" by the windscreen and aluminum skin. Add to that, the nose of the B-17 and B-24 had large plexiglass noses that allowed MG/cannon rounds very little resistance.

In a head-on attack, the rate of closure between the fighter and the bomber meant that the defensive armament aboard the bomber had very little time to aquire the inbound fighter, increasing the chances of the fighter successfully scoring hits on the bomber. Chasing in on the bomber's 6 meant a longer rate of closure to get in range, by which time the gunners of the bomber have had more time to aquire the fighter.

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Armor on the B-17F:

davebender said:

It's plenty if you put them on target and a B-17 is a relatively easy aerial target. However you are likely to run out of ammo after downing a couple aircraft.

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I have a book titled "Zero - A6M" by HP Willmott that disagrees with this. It quote flight trials undertaken by ltcdr Kofukuda and lt Kono, with a zeke and B-17C in 1942. These officers, in their final report stated "with only 60 rounds per cannon, and only rifle calibre MGs to support the main armament, the navy type O fighter does not have the firepower to deal with the US bomber adequately." These officers further reported that the limited oxygen and ammunition supplies, the Japanese officers reported that the zeke could only make about 5 or 6 runs on a high flying B-17. These officers were among the first in the japanese camp to recognize the inherent weaknesses of the Zeke. They recommended frontal attacks, increasing the ammunition supply and oxygen supplies, which were incorporated into the A6M3.

For the Japanese, however, the B-17 was a relatively rare beast. From mid 1942 onward, the princiap long range heavy bomber in the Pacific was the B-24, into whioch approximately 6000 were deployed. Only about 200 fortreses were ever deployed into the PTO

Juha said:

Yes, over 22 missions in 1943, from March 13 to Dec 24. Ki-43s were most successful on Dec 1 when they got 5 B-24s while losing one Oscar and least successful on Oct 27 when they failed to shot down any B-24s but lost 3 Oscars.

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22 missions over 9 months - does it say specific squadrons or groups? In reality that may not seem that bad statistically (1.5 bombers lost to fighters per mission). It would also be interesting to know how many bombers were sent out, this would paint a real picture of this "duel."

If you look at the diagrams of the B-17's armor you'll notice that it's mostly situated to protect from attacks from the rear only, some of it could be worse than useless if the attack was from the front.

Shortround6 said:

Trouble is the range won't be long if you want any real hope of a hit. No country was rich enough to fire thousands of rockets for each enemy aircraft brought down. the 5in HVAR (introduced after D-Day) used 23.9lb of propellant for a 1375 ft/sec velocity which is actually rather poor for an air to air weapon. Both the .50 cal and 20mm Hispano had velocities of around 2850-2880fps.

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but the R4M was only a little bit faster than HVAR (525 m/s vs 419 m/s) and it was used for air to air, even the Werfer-Granate 21 with the speed of only 320m/s was used for air to air about 15% accuracy and most German fighter ( BF-109 ) can only carry 2 of them
and while it may be impractical to fire HVAR from 2-3km i thik it ok to fire them from 400-600 m where the turret gun of the bomber is not very effective

mig-31bm said:

but the R4M was only a little bit faster than HVAR (525 m/s vs 419 m/s) and it was used for air to air, even the Werfer-Granate 21 with the speed of only 320m/s was used for air to air about 15% accuracy and most German fighter ( BF-109 ) can only carry 2 of them
and while it may be impractical to fire HVAR from 2-3km i thik it ok to fire them from 400-600 m where the turret gun of the bomber is not very effective

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Germans weren't firing Werfer-Granate 21 a single bombers but at formations. And even then it was not with the expectation of hitting a bomber (they were using time fuses) but of coming close enough to damage one or more while breaking up the formation/s so that gun attacks would be more effective.

The R4M wasn't a long range stand off weapon either, despite what Wiki says. lets look at it shall we?

"The anti-aircraft version of the R4M used a large warhead of 55 mm. with 520 g. (17.6 ounces) of Hexogen explosive charge, nearly guaranteeing a fighter kill with one hit. Each R4M weighed 3.2 kg and was provided with enough fuel to be fired from 1000 m., outside the range of the bomber's defensive guns."

Now that certainly sounds like a stand off weapon but one line later;

"A battery typically consisted of two groups of 12 rockets and when all 24 were salvoed in an attack, they would fill an area about 15 by 30 m. at 1000 m., a density that made it almost certain that the target would be hit. The R4Ms were usually fired in four salvos of six missiles at intervals of 70 milliseconds from a range of 600 m"

So what was the range?
And then we have this line "The Luftwaffe found the R4M missiles to have similar trajectory to the 30 mm MK 108 cannon in flight, therefore the standard Revi 16B gunsight could be utilized."

Now the 30 mm MK 108 had a MV of 500 m/s and the Luftwaffe gave an absolute maximum combat range of 900 meters at 3000 meters altitude and 1100 meters at 6000 meters altitude (thinner air) and an effective range of just 400 meters against bombers( it would be shorter against fighters) for the 30 mm MK 108.

600 meters is within the effective range of .50 cal machine guns mounted in power turrets.

I am not sure where the 15% accuracy figure for the Werfer-Granate 21 comes from as the math doesn't work quite right. Best case from the Wiki entry "While a single fighter's payload of two or four such rockets was extremely unlikely to score a hit, a mass launch by an entire fighter squadron (12-16 aircraft) as it arrived to intercept the bombers would likely score two or three hits, about 15% accuracy" is 12 aircraft at 2 rockets apiece (24 rockets) getting 3 hits which would be 12.5%. 16 fighters firing 2 apiece and getting two hits would be 6.25%. Please note that blast radius of 15meters from the 40.8 (90lb) warhead helped.

And " The low launch velocity also meant accurate aiming was difficult, as it was for the attacking pilot to accurately judge the distance to the target. As a result most of the rockets fired exploded either in front of or behind the bomber target. However, they did often achieve the effect of opening up the bomber formations enough for fighters to attack with conventional weapons."

The rockets sound cool but in actual fact never quite lived up to the hype, and this goes for the American, British, French and Soviet rockets of the 1950s too, Despite much money, time and effort.

See: http://www.ww2aircraft.net/forum/stories/battle-palmdale-20533.html#post1114130

mig-31bm said:

if a well armed B-17 meet a fighter light armor and weak weapon like P-51H or A6M zero in 1 vs 1 situation then which one do you think more likely to get shotdown ?
it obvious that fighter will fly , climb , turn alot better but the B-17 have 13 � .50 in (12.7 mm) gun which mean it can basically attack the fighter from any direction , and also with 4 engine it seem like it really hard to be shotdown , not to mention very thick armor on a bomber
btw : can the rocket be used to shot down bomber ??

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Thought you might be interested in this version of the B-17:
https://en.wikipedia.org/wiki/YB-40_Flying_Fortress

Aozora said:

Armor on the B-17F:

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And that illustration gives a good idea of how little the B-17 was actually protected. The flight deck was afforded some protection *if* the attacking fighters followed Boeing's design, but they didn't. The windscreen wasn't armored glass, the nose dome was plexiglass, the side windows and observation dome just ahead of the cockpit wasn't armored.

Add to that, the gunner's positions afforded little protection and the tail gunner had little or no protection until the "Cheyenne Hood" was adopted and even then, the only real armor was a reinforced plate of glass. If you've ever read any accounts (or spoke with veteran crewmembers) of missions, there's plenty of stories retelling how schrapnel or MG/cannon fire ripped through the fuselage of the bomber, and the projectiles rarely passed through harmlessly.

And the larger the caliber, the more the damage, plus no amount of armor aboard the B-17 protected the crew from the 30mm minengeschoss round of the Mk103/108 cannon.

We've seen the effects of up-armor in the way of speed penalties with the YB-40 project.

And just to clarify, the chin turret wasn't incorporated into the B-17 until after the failure of the YB-40 project in 1943, the last of the B-17Fs being outfitted with the modification nefore the switch to the B-17G production.

FLYBOYJ said:

22 missions over 9 months - does it say specific squadrons or groups? In reality that may not seem that bad statistically (1.5 bombers lost to fighters per mission). It would also be interesting to know how many bombers were sent out, this would paint a real picture of this "duel."

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There is the info in the book but I don't have the time to reread it but the B-24 units were 7th 308th BGs. E.g. on 24 Aug 43 14 B-24s/308BG were to bomb the a/f at Hankow but the 7 planes of the 373rd BS were forced to abort because of the weather and the 7 B-24Ds from the 425th BS pressed on to the target escorted by 6 Warhawks. After bombing the B-24s were attacked by Ki-43s from 33rd and 25th Sentais, which shot down four of the seven B-24s while probably losing one Oscar and the CO of the 33rd Sentai to the defensive fire and 25th Sentai lost 2 of its Oscars to the P-40s. I chose the day only because the artwork described that combat. During the summer B-24 attack formations seems to have had 9 - 18 planes.

the 22 missions were those where there was combat between B-24s and Oscars during 1943 in the CBI.

Juha said:

There is the info in the book but I don't have the time to reread it but the B-24 units were 7th 308th BGs. E.g. on 24 Aug 43 14 B-24s/308BG were to bomb the a/f at Hankow but the 7 planes of the 373rd BS were forced to abort because of the weather and the 7 B-24Ds from the 425th BS pressed on to the target escorted by 6 Warhawks. After bombing the B-24s were attacked by Ki-43s from 33rd and 25th Sentais, which shot down four of the seven B-24s while probably losing one Oscar and the CO of the 33rd Sentai to the defensive fire and 25th Sentai lost 2 of its Oscars to the P-40s. I chose the day only because the artwork described that combat. During the summer B-24 attack formations seems to have had 9 - 18 planes.

the 22 missions were those where there was combat between B-24s and Oscars during 1943 in the CBI.

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Great info, thanks!!!