WWII Anti-Aircraft Gun Questions

Watching old footage of WWII I often see anti-aircraft guns shooting wildly into the sky… and subsequent explosions all around attacking aircraft. I’m talking about long range bombers mostly.

While the object is clearly to hit a plane if possible, are the shells being fired set to detonate after a certain amount of time, or at a certain altitude, if they haven’t hit something first, hence the random explosions around the planes? But how can the ammunition be adjusted to match the altitude of incoming aircraft?

And if you are in a bomber that is being fired upon what can you do to avoid being hit by anti-aircraft fire? Change altitude to confound the enemy gunners? Fly higher than their guns can shoot? Use overwhelming numbers to improve the odds of some getting through?

The shells had fuses on them that would detonate at certain altitudes (or certain times after firing?).

It is very hard to hit a plane that is flying very high with a little shell. So you put up shells that exploded and spread shrapnel (akin to a grenade but bigger).

The gunners would need to guess the height of the planes to set the shells appropriately. This of course was an inexact science so you would have gunners guessing high/middle/low. That is why you see the little poofs going off all over the place.

One flak gun is near useless. Several dozen could put up a wall of trouble for incoming planes.

As for the bombers there was little they could do. They are not nimble and air defense were all over the place. Since the AA fire was a bit inaccurate and WW2 bombers could absorb silly amounts of damage they just flew straight and level and prayed and kept going. Some planes would be shot down but many would make it.


Wow…cool. I (vaguely) knew the idea was there during WWII but had no idea they could get them into AA shells.

Still, as mentioned in the article, getting the shells close enough to planes even with this tech was not trivial. As a result weight of fire mattered (put up 100 shells/minute and hope a few get lucky).

Earlier in the war, flak relied on time or altitude fuses. I understand that gunners had charts and mechanical computers that would solve for the correct time for a given target, and the resulting time would be fed into an automatic fuse setter. Obviously this required a great deal of precision to work well, and it wasn’t always effective.

Shells later in the war were dramatically improved with proximity fuses. These used a radio transmitter, and listened for the sort of radio echo that bounces off of metal airplanes. Sort of a crude form of radar.

Wow. I had no idea. Thanks for the quick answer!

a tactical dillema for b-17s over germany. attacking german fighter planes forced them to fly level in close formation to allow several .50 cal weapons to bear. but flying level in tight formation made them vulnerable to ac-ac.

Nothing spurs innovation like someone trying to kill you, or vice versa.

This was so top-secret that for a long time, these shells were only allowed to be used over water, where unexploded ones could not be retrieved by the enemy and analyzed. It can be argued that the proximity fuze and Radar were more important to winning the war than the Manhattan project.

Patently, since the Manhattan project had nothing to do with winning the war. Ending the war against Japan more quickly and economically, arguably, but by the time it produced anything usable the war was already won.

The truly amazing thing is that some of those relied on vacuum tubes.

The formations were designed to provide overlapping fields of fire for protection against fighters. AIUI, fighters didn’t like to fly through flak – which the bombers had to. The bombers had to fly a straight-and-level bombing run on the target. So the anti-aircraft gunners had a fairly good idea of where to shoot.

I understand the need back then to fly straight and level to bomb but how long did they have to fly that way? Seems to me you should be able to weave and wobble and dive and climb and do whatever you want till within a few minutes of the bombing target.

For those few minutes you are stuck but for the other 99.99% of the flight you should be pretty free yet it seems they still flew close formations level and straight the whole way.

Tight formations provided several benefits: The planes were too close together for a fighter to fly though, they had mutual fields of fire, navigation was easier, if you got shot down your buddies could report you position, and bombing was more accurate.

I remember in Catch 22, Yossarian was kind of a proto-Rincewind, so intent on saving his own skin that the whole bomber crew listened and took advantage of his screams to go up, go down, or go around to avoid where he sensed the incoming flak would be, and the pilots bobbed and weaved accordingly. Was that poetic license?

I always wondered about mutual fields of fire.

I get that it was better at shooting down incoming fighters.

But it also seems restrictive and dangerous to each other.

Mutual fields of fire sounds to me like you have a good chance of accidentally strafing a fellow bomber. In the heat of battle particularly so.

For more info there’s Tachymetric anti-aircraft fire control system, Gyro Rate Unit Box and High Angle Control System.

In addition to the fuel and time on target considerations, radical maneuvers introduce the very distinct possibility of midair collisions. You were typically better off taking your chances with the flak. Also, a lone bomber simply begged for the Germans to attack it, whereas a tight formation had overlapping fields of fire.

While “friendly fire” hits from Air Gunners undoubtedly happened, and no doubt a few of them caused casualties, AGs were highly trained, and would have been constantly aware of the need to avoid hitting their own side.

That’s particularly true of USAAF gunners, who were usually over enemy territory during daylight. RAF Bomber Command usually flew night missions, which made identifying a target a lot more difficult.

While being on a bomber crew would have been terrifying, the Luftwaffe didn’t have it all their own way, and many Luftwaffe planes were brought down by Air Gunners; there were AG “aces” in both the USAAF and RAF.

It was regularly pointed out that bombers would have been faster/lighter/more manoeuvrable/cheaper without the air gunners, but aircrew always insisted on keeping their gunners. The ability to shoot back is a big morale boost.

ok, people here explained the trade-offs between flying level and maneuvering, in groups or alone. these dictate your vulnerabilities to AA and fighters, everything else equal.

there was a lone b-17 mission in the solomons requiring recon photos to be taken over a japanese-held island in preparation for an invasion. the island had AA, and it had an entire zero wing protecting it.

the mission was strictly on a voluntary basis.

one pilot volunteered. a misfit, a lot like boyington’s black sheep squadron. his crew took an old b-17, numbered 666, and proceeded to modify it. they mounted a total of 19 browning .50 caliber machine guns on it, including one that fired along the pilot’s line of sight. there were spare browning machine guns on board in case the mounted guns jammed or were shot away.

when they flew over the island, they were met by 17 zero fighters. the zeros ringed the bomber in a wide circle, respectful of the .50 calibers. one by one the japanese fighters did frontal firing attacts (the b-17’s most vulnerable part.) the nose gunner shot down the first zero. the pilot shot down the second. but the third finally threw enough cannon shells at the nose, killing the nose gunner and wounding the pilot.

then the wounded pilot began flying in an ‘S’ pattern so as to minimize the time an oncoming zero can shoot at the nose. eventually, they took the needed photos and maneuvered out to safety.

the “old 666” crew became the most decorated american air crew in world war 2.