by Peter Marland
HMCS Haida - Weapon System, 1943-49This note covers the weapon system of HMCS Haida, a Canadian Tribal class destroyer completed in 1943, through to her updating in 1949.
As built, the ship had three 4.7" twin mountings in A, B and Y positions, plus a twin 4" mounting in X position. The 4.7" guns had a maximum elevation of 40 degrees, whilst the 4" could elevate to 80 degrees. The ship had a single fire control system, with separate predictors for low angle (LA) firing at surface (SU) targets, and another for high angle (HA) anti-aircraft (AA) fire. The main compartment was the transmitting station (TS), though other ships with AA-only systems called this space the High Angle Control (or Calculating) Position (HACP).
Apart from the museum ship itself which was modified beyond its WW2 state, there are several sources to reconstruct the likely wartime configuration:• Technical Handbooks (Books of Reference, BR's) and Confidential (or Charge) Books, CB's, that describe individual equipments. In the 1940-1950 period these do not include good system overviews, and often just describe the circuitry involved. Coverage is often fragmentary, and limited to a particular electronic unit, rather than the complete system. In the UK these references are largely held by the Collingwood and HMS Excellent museums, plus The National Archive (TNA) at Kew.
• Drill Books are BR's that cover the sequence of orders & actions to make a weapon system function. Neither Collingwood or Excellent have a drill book for Haida's system, but TNA hold one for a later destroyer with a Fuze Keeping Clock based system (see ADM 234/165). Ref would have been BR1054.
• Ships 'as fitted drawings' that show where equipments were fitted, and how the various equipments were interconnected electrically, via cables/cores and junction boxes.
• Finally, there may well be training establishment notes, handouts or drawings that help explain aspects of the equipment to supplement the BR's/CB's, or in some cases, official training films/movies.In the WW2 period, data transmission was primarily by 'M Type' a stepping system switching DC from +24v, to zero to -24v DC, as the angular input shaft rotated, via a sequence of 12 or 24 steps. Such systems had coarse and fine channels, and could handle accuracy at levels of 2 to 5 minutes, but were not synchronous (self-aligning), and could easily slip, so ships staff would check readings were in step whenever the opportunity offered (see BR1096 Chapter 8). The AC systems (the US Synchro and UK Magslip) appeared during the second half of the war, but did not wholly replace the M Type until the 1950's.
During 1943-49 there was no effective remote power control (RPC) from the predictor out to the gun mountings, therefore the guns crew 'followed the pointer' of training and elevation order receivers, driven by M type transmissions from the TS.
For the Haida system, there is no single overarching title or name. In contrast AA systems like HACS or Flyplane had a single title embracing all the components, but the pre-war systems in destroyers and below, have a list of all the component parts, not a single description or nomenclature. The main reference is the BR931 series, with BR931(1) Handbook of the Fuze Keeping Clock and Associated Equipment. Introduction.Haida's system includes:
• Destroyer Director Control Tower (DCT). Upright cylinder structure with stepped roof, uses Type P stabilised sights. Layer, Trainer and Director Officer controlled surface fire, taking target range from the separate rangefinder director. See Peter Hodges & Norman Friedman. Destroyer Weapons of WW2.
• Mk 3W Rangefinder Director (RFD), with optical rangefinder and Type 285 radar. Fitted abaft the DCT, but raised above it. Haida had a Mk 3W Rangefinder Director, where 'W' indicates a windscreen. The trainers sight was stabilised for level angle. See BR931(3) and (9).
* Optical Rangefinder. UK Mk III rangefinder with 12 foot base length. See BR295B. Moving eyepiece (elevates with rangefinder). Inverted strip image, and can be rate aided by range drive from FKC. Fitted with QG Mk II air disturber and desiccator gear.
* Radar Type 285. See BR 1634(5).Comment. The windscreen may well be the deflector up to 12 inches high, held off from the director vertical walls, to give a venturi, diverting wind up, and so avoiding edge turbulence buffeting the crew in the open body of the director. See bridge windscreens.
• Admiralty Fire Control Clock (AFCC) Mk I, for fire at surface targets. BR901(43)
• Fuze Keeping Clock (FKC) Mk II Star, for fire at AA targets. Inputs include target bearing, elevation and range, plus angle of presentation (AP). Contains single set of ballistic cams for 4.7 inch guns, covering Tangent Elevation and Time of Flight (Fuze Number).
? Because FKC provided a single set of ballistics for 4.7 inch guns (A, B and Y), additional corrections were required for X mounting (4 inch gun). The FKC output was modified by a separate AP10440 Fuze Conversion Unit to give a revised set back and fuze number for the 4 inch shell.
? FKC limits were: present range 1000 to 17000 yards, range future (fuze range) from 0 to 11500 yards, height to 35000 feet, target speed of 40 to 250 or 300 knots, and angle of sight from minus 10 degrees to plus 80 degrees• Other components like gyro level corrector Mk III or IX (BR913(4)) converts director elevation into angle of sight by eliminating 'roll' along the line of sight. An Auto Barrage Unit (ABU) fired an AA barrage at a set target range using radar range from 285, see BR1634(6).
• Elevation Receiver (E Mk I two star), and Training Receiver D Mk IV star). Fitted at the gun mountings. See BR 912(12) and (20, plus BR912(8), (11) and (20).
Oct 14/20