Type D Depth Charge (UK)
The British Type D and Type D* Depth Charges were the first British depth charges designed from scratch for the purpose. They are described in the Annual Report of the Torpedo School, 1915, and were envisioned to become the standard types of depth charges for the Royal Navy.[2]
Particulars
The Type D and Type D* depth charges had the classic cylindrical shape of many World War II "ash cans".
These were much larger depth charges than earlier designs fashioned from other weapons. The Type D* was a variant of the Type D that employed a smaller charge within the Type D shell so it could be used by craft unable to make the 15 knot speed judged a minimum to escape injury from the Type D's charge at the shallow depth setting. The Type D/D* weapons had 300/120 pounds of T.N.T. or Amatol initiated by 2.25 pounds of gun cotton, yielding total weights of 430/250 pounds and danger radii calculated by Vernon at 70/35 feet.
Hydrostatic triggering was for 40 or 80 feet, selectable by moving a lever at the top of the pistol. The rate of sinking for the charges is sadly illegible in my photographed source, but seemingly different for the two types, which seems sane. The sketch of the two seems to show that the Type D had a parachute assembly to slow its rate of sinking. Given its considerable danger radius, the Type D's 40 foot setting was never be used when the depth of water would permit the 80 foot depth to be used. For additional protection, each Type D was provided a steel parachute to slow its rate of sinking which could be attached for use at 40 foot depths.
A special primary safety gear, in series with the main trigger, prevented initiation in water shallower than 10 feet.
Deployment and Use
In 1915, it was envisioned that these would become the standard large and small charges. The first orders of the Type D were made in September 1915, and the Type D* followed in April, 1916.[3]
On December 1, 1915, the Type D was about to be issued and the Type D* was under trial.
A hydraulic release mechanism had been devised for installation in dockyards by which ships could release these charges from the bridge position, to ensure their precise delivery.
In early 1916, it was specified that these weapons should be unshipped and stored below in bad weather.[4]
On 7 September, 1917, Christopher of the Fourth Destroyer Flotilla shipped six Type D charges at Plymouth. She dropped three of them, and one Type G on a submarine contact on the 24th.[5]
By 1918, supplies in-hand or on order were becoming immense. By January 1, 1918, 33,300 Type D and 21,700 Type D* had been approved for order. Approved Type D orders would continue to accrue, amounting to 45,300 at the beginning of April and 61,300 by mid-year. Total expenditures of the two types at the top of the first three quarters of 1918 were 3,000/1,000, 5,500/1,600 and 10,000/2,600. This seems to imply that Type D charges were being dropped at the rate of 50 a day over the second quarter of 1918.[6]
The last order of Type D* charges was in October, 1917 and no further orders were being contemplated, as there were 5,451 in store by mid-1918, and this amounted to over a year's supply at present rates of expenditure. The Type D was the future, with vast numbers approved for order and only 1,403 - about a month's supply - in stock in mid-1918.[7]
See Also
- There was allegedly a Handbook for Type D depth charges
- H.M.S. Vernon. (1920) Annual Report of the Torpedo School, Mining Appendix, 1917-18. Copy 6 at Admiralty Library, Portsmouth.
Footnotes
- ↑ Annual Report of the Torpedo School, 1915. Plate 84.
- ↑ Annual Report of the Torpedo School, 1915. pp. 164-5, 173, Plate 73, Plates 84-6.
- ↑ Annual Report of the Torpedo School, Mining Appendix, 1917-18. Plate 26.
- ↑ Grand Fleet Gunnery and Torpedo Orders. No. 122.
- ↑ Ship's log at The National Archives. ADM 53/37730.
- ↑ Annual Report of the Torpedo School, Mining Appendix, 1917-18. Plate 26.
- ↑ Annual Report of the Torpedo School, Mining Appendix, 1917-18. Plate 26.
