RN Destroyers' AA Gunnery 1930-70

[dunmunro]

Abstract of a talk given by Mark Brady:

At the Explosion! museum in the UK, on Oct 18 2009.


"RN Destroyers' AA Gunnery 1930-70

Herewith an abstract, with a few asides thrown in:

The British Admiralty decided in the late-1920s that future Destroyers must
protect Capital Ships against air attack with their main-armament guns, and
during the 1930s procured a suitable anti-aircraft fire-control system [in
which the predictor was the so-called 'Fuze-Keeping Clock' in the 'Tribal'
class - very similar in concept to the contemporary HACS Mk III]. This
equipment, and destroyers’ gun-armament generally, was much-criticised
because many RN destroyers were themselves sunk by air attack during 1939-41
but such criticism was misplaced – given contemporary technological
limitations destroyers’ gunfire alone could not defend them against the
prevailing air threat. After 1941, however, wartime improvements [notably
Type 285 radar, and later Type 275] made destroyers’ gunfire increasingly
effective against aircraft [it also helped that the air threat during the
second half of the war was predominantly from fast low-fliers rather than
dive-bombers]; and steps were also taken to develop (or procure from the
USA) new AA fire-control systems [i.e the home-grown Flyplane Control System
and the US Navy GFCS Mk 37 - both of which turned out to be rather
disappointing]. During the ‘Cold War’ that effort continued until the
late-1950s [firstly with the 'MRS 7' programme, in which late-war destroyers
had FKC itself replaced by an electronic predictor, and later with the
introduction of MRS 3 - whose low number in the 'MRS' scheme was due to its
having been under development over 10 years] when it was finally apparent
that for Anti-Air Warfare roles future destroyers must principally be armed
with medium/long-range guided missiles. Even so Type 42 destroyers retained
a self-defence anti-aircraft capability using their 4.5” gun – only after
the Falklands Conflict was this recognized as no longer cost-effective."

[RF]

My first reaction on reading this was to wonder whether the staff who thought up these ideas between the world wars considered that destroyers main guns used against aircraft could only work in flat calm seas.....

[Dave Saxton]

This is a very interesting and it echoes some of Louis Browns points about the problems that came to the fore during the war. It's interesting that the RN didn't find the Mk37 director very satisfactory. Brown also reports that the MK37 and the MK4/22/12 radar systems did not deal with the late war Kamikaze attacks all that well. The Japanese soon learned that it had problems dealing with low flying aircraft and changed their tactics.

Howse reported that the RN did not find any naval flak control systems satifactory late war. Empirical data indicated that the VT fuze wasn't quite the panacea that it is often described as. Indeed it wasn't until the MRS systems came on line in the 50's that they got more of what was wanted in terms of flak control, based on the war experience.

Type 285M had lobe switching in one axis only. Either for bearing or for elevation, but not both at the same time. Coupled that with the range accuracy of 150 yards, and although obviously better than purely optical direction, it wasn't much better than optics.

Type 275 was probably the best shipboard flak control radar actually deployed before the end of the war, provided there was a director equal to the task to go with it. It used a conical scan.