British Anti-Aircraft Artillery in WWII

Here’s a video the  British released during World War II explaining AAA duty.

 

Recall of course that Britain was under nearly continuous air attack for much of the war. That meant a much larger investment in fixed and semi-fixed batteries than the US made. The mount shown appears to be the Vickers 4.5” QF gun, itself an adaptation of a dual purpose naval gun. The predictor appears to be the Vickers Type 10. The narrative alludes to radar, but for security reasons, doesn’t specify it.

Interestingly, while the 4.5” QF was an excellent gun, it began the war with rather sub-par ammunition. The Type 199 had an igniferous time fuse. That is, a burning powder train was used for the time delay. But since altitude effects burn rate, it was a less than wholly satisfactory fuse. A later mechanical time fuse and fuse setter were adopted as soon as possible. Oddly, it doesn’t appear a VT proximity fuse was ever adopted for the 4.5” QF, though VT fuses were used in other similar British AAA guns.

The US and most other nations pretty much abandoned AAA guns as soon as guided missiles became available in the 1950s.

The Russians and their client states, however, did not. I was chatting with a friend about this, and since whenever I go to the effort of writing, I think you should benefit, here’s part of the conversation:

The commies sure loved them LOTS of AA guns. I mean, LOTS.

Why the affinity for them?

They’re relatively cheap. And quite effective. Look at airplane losses in Vietnam, guns were far and away deadlier than SAMs.

I’d have to double check, but I think guns even took down more planes in Desert Storm than missiles.*

Lots of medium caliber guns (23-57mm) effectively deny the airspace below 10,000ft. Which incidentally means you’re pushed into the prime SAM engagement envelope. Which, you then have to spend a good part of the initial air campaign suppressing the SAM systems, and not striking the targets you want.

The first two nights of Desert Storm, the Navy and AF and RAF used low level tactics to avoid SAMs. And the losses were quite heavy. And virtually all to guns. They switched to medium altitude after that, reasoning it was easier to jam, suppress and avoid SAMs than to give up a $40 million jet to a cheap ass gun.

*Our friend Robin has an analysis of lost and damaged coalition aircraft in Desert Storm.

The T-231- an odd approach to Air Defense

The other day, friend o’ the blog Craig steered me to this post on Facebook by the Manassas National Battlefield Park:

On Saturday, May 23, a visiting family made a most unusual discovery at Manassas Battlefield. They found what appeared to be an unexploded 20th century shell while out hiking and brought it to the Visitor Center. Park law enforcement staff called in the state police bomb squad and subsequently evacuated the Visitor Center and Henry Hill. The bomb squad later confirmed the shell was inert and harmless.

First and foremost, if you find anything that even remotely resembles unexploded ordnance, do not touch it. Note the location and inform the authorities.

As it turns out, the EOD detachment was able to discern the projectile was a T-231 rocket. Which got me digging, what the heck is a T-231? Well, it was a 2.75 inch diameter (70mm) rocket projectile, sometimes referred to as HEAA.

T-231 1

t-231 2

Forgive us for not having a lot of concrete information on this, but it appears that not more than a relative handful were constructed. We infer that HEAA stands for High Explosive Anti-Aircraft. That is, in spite of the notation in the Facebook post that it was an air to air weapon, it was in  fact intended as the ammunition for a ground based anti-aircraft gun system.  What’s that, you say? How does a rocket work in an anti-aircraft gun? Well…

You may recall we’ve occasionally addressed anti-aircraft artillery and fire control here.

 

One of the challenges in anti-aircraft gun fire control is the lengthy time of flight for the shells to reach the target area. The longer the time of flight, the greater the chance the target will maneuver away from the aimpoint selected as much as an entire minute before. Remember, while a projectile fired from a cannon might have great velocity as it leaves the muzzle, it immediately begins to decelerate due to both gravity and air resistance. Thus, the closer to maximum effective range, the slower and slower the shell is moving.

If there were a way to have the velocity of the projectile remain constant over the course of its time of flight, or even just significant portion, that would simplify the fire control problem.  A rocket, of course, accelerates as long as its motor continues to burn, until it reaches its maximum possible aerodynamic speed.  Rockets of those days were, however, somewhat inaccurate weapons.

And so it appears the Army tried an intriguing approach to combining both a gun and a rocket into one weapon. The T-231 was packed inside a recoilless rifle shell casing. That is, it had an open end and was fired from a recoilless rifle. The firing charge imparted a relatively modest muzzle velocity of about 1000 feet per second to the round. The initial charge also served to ignite the round’s rocket motor, which then boosted it to a velocity of about 3000 feet per second, roughly on par with the muzzle velocity of existing anti-aircraft guns. But the small size of the projectile meant there was a correspondingly small rocket motor (and less size for a warhead as well) and that limited the burn time for the motor.

in flight

Launcher

T-231 3

The program never really went beyond a handful of test firings, mostly to gather data. The performance wasn’t significantly better than existing anti-aircraft artillery, and the first generation of guided missiles was just reaching operational status at the time, rendering the project obsolete.

Craig did point out one mystery yet to be solved. The test firings apparently took place at Wallops Island. So how did the projectile find its way to Manassas? We may never know. 

Early Anti-Aircraft Artillery

Even by the middle of the First World War, the threat military aircraft posed to ground forces was recognized, and adaptations of existing artillery pieces were made to fulfill the anti-aircraft artillery (AAA) role. This Signal Corps film, produced in 1935, shows the status of US Army AAA in the interwar years.

[youtube https://www.youtube.com/watch?v=Ca1U1-HBp-c]

The level of sophistication in control is impressive. Predictive director control for guns ranging from 3” down to the multiple .30cal mount. Acoustic locators used to control searchlights.  Of course, during World War II, radar would replace the acoustic locator. But it is important to recognize that the basic architecture behind the organization was already well thought out.

Speaking of acoustic locators, as a long range sensor, Britain built several arrays of very large “sound mirrors” for long range detection to protect the home isles from air raids in the years immediately after World War I. Their remains can still be seen in the southeast.