King George V class - Anti-Aircraft Armament

(How many Pom Poms can we fit on one ship?)

(1/24)

While the dual-purpose 5.25-inch guns would suffice to break up incoming air attacks, a dedicated anti-aircraft weapon would be needed closer in to try and shoot down enemy aircraft.

(2/24)

As designed the King George V class had the following anti-aircraft weapons:

- 4 x Octuple Pom Poms. Two of these were fitted on each beam, atop the hangar.
- 4 x Quad 0.5in machine guns. Two were mounted on the boat deck, one on 'B' turret, and one on 'Y' turret.

(3/24)

As it happens, the Quad 0.5in machine guns were never carried, so I won't go into detail on them. They saw widespread service throughout the Fleet but were not particularly effective against modern aircraft.

(4/24)

The mainstay of the KGV's anti-aircraft defence was the Octuple Pom Pom.

The '2 Pounder Pom Pom' was a relatively old weapon although still pretty effective. Development started in the early 1920s although the first didn't enter service until 1930.

(5/24)

The Pom Pom had a calibre of 40mm (1.575"). Eight barrels of this calibre strapped to the same mount was a hefty weapon and weighted 15 tons.

Rate of fire was 96-98 rounds a minute using controlled firing gear, or 115 under full automatic - per barrel.

(6/24)

On mount ammunition supply was 140 rounds per gun, allowing over a minute of continuous fire without reloading.

Each mounting had a separate director for fire control. This directors later gained radar.

(7/24)

In 1938 a 'High Velocity' version was introduced, which according to Navweaps increased effective range by 40%. Tracer rounds were carried from 1941 onwards.

A good video on the Pom Pom is from @ArmouredCarrier



(8/24)

The Pom Pom had its share of issues, but it was an important part of any RN ship's anti aircraft defence.

It's primary drawback was the low velocity compared to other weapons (even in the High Velocity version). But it's still 8 x 40mm cannon with director control.

(9/24)

During construction the Quad Machine Guns were eliminated from the design and the required number of Pom Poms increased to 6 - the KGVs would now carry them on 'B' and 'Y' turrets.

(10/24)

However, these extra two mounts were not ready for KGV and PoW carried the 'Unrotated Projectile Launcher' instead.

This was a rocket launcher which fired aerial mines on parachutes. The idea was that aircraft would hit the wires and draw the mines upon themselves.

(11/24)

There's a good 1 minute video on the system here:



Designed as an interim system while Pom Pom production caught up, nonetheless it was terrible, and all UP mounts were quickly removed. The Pom Poms were fitted quickly afterwards!

(12/24)

While the Pom Pom proved a good inner layer defence, war experience proved more was needed. 20mm Oerlikon cannons was thus fitted anywhere there was room as they became available.

(13/24)

The 20mm Oerlikon was introduced as a modern 'point defence' weapon, to complement the director controlled Pom Poms. A mix of single and twin mounts were used. It had a bigger punch than the 0.5in machine gun and could fire at abour 300rpm.

(14/24)

By 1945 it was considered that the 20mm lacked the punch to stop modern aircraft, although the KGVs still carried them in large numbers in a combination of mounts:

- KGV had 38
- DoY had 54
- Anson had 46
- Howe had 42

(15/24)

From 1944 the class underwent large refits to prepare them for service with the British Pacific Fleet.

This added yet more 20mm, a further 2 Octuple Pom Poms (for a total of 8), Quad Pom Poms (in some), as well as the famous 40mm Bofors.

(16/24)

Each ship received 2 Quad Bofors mounts, of USN fame, with their associated Mk 51 directors. Some ships also received single mounts as well.

The 40mm Bofors was a highly successful autocannon and very effective. The same calibre as the Pom Pom, but a much newer weapon.

(17/24)

Muzzle velocity was about 20% greater than the High Velocity Pom Pom, which lead to a short time of flight and higher impact.

No 8 barrelled version though! (Although a Sextuple mount was developed for Vanguard!)

(18/24)

Some wonder why the British stuck with the Octuple Pom Pom so long. But there was nothing really comparable to it until the Quad Bofors - the prototype of which first went to sea in July 1942!

At the time RN losses to aircraft were at their worst, it did not exist.

(19/24)

For all the criticisms Royal Navy ships get for their anti-aircraft armament, they arguably had the heaviest light anti-air of any Treaty battleship as designed.

(20/24)

And despite the low velocity of the Pom Pom it was still a very useful weapon.

There were better guns out there, but not in Quad or Octuple mounts tied to a director.

(21/24)

HMS Prince of Wales was sunk with 48 x Pom Poms (40mm), 1 x Single 40mm Bofors and 8 x 20mm Oerlikons.

The only advantage the US fast battleships had at the time was in 20mm, where the greater production capacity of the US was paying dividends.

(22/24)

When HMS Duke of York sailed into Tokyo Bay in 1945 for the Japanese surrender, she carried 150 barrels of light anti-air:

- 88 x 40mm Pom Pom (8 x VIII, 6 x IV)
- 8 x 40mm Bofors (2 x IV)
- 54 x 20mm Oerlikon (8 x II, 38 x I)

This compared well to any similar ship.

(23/24)

There are certainly criticisms you can level at the anti-aircraft batteries on the KGVs, but I don't think you can ever say that the RN took the air threat less seriously than their contemporaries.

For their time, they pretty much always carried respectable AA fits.

(24/24)