Hallett's Director

Hallett's Director was an experimental torpedo director invented by Lt. John I. Hallett and tried at sea and rejected by the Royal Navy's Torpedo School in 1914.

Geometry

The director was intended to exploit, with improvements, an old practice of French torpedo boat tactics The geometry of the design drew upon the fact that when a collision course on another ship is steered, that ship will be on a "steady bearing" no matter its speed or heading.

Use

The director's "own speed bar" is always aligned with the keel of own ship, and is initially set to zero speed and the torpedo bar is set to the speed of the torpedo. The commander then endeavours to steer a course and speed such that the enemy is on a constant bearing. Once satisfied that he has done this, the sighting bar is pointed at the target and the speed of own ship is placed on "own speed bar". This would establish the proper director angle on the sight. The primary innovation Hallett added to the process was to use a gyroscope to fire the torpedo the instant the tube was aligned with the correct bearing to fire. The ship could then have helm applied and the torpedo would fire when it came on target.

Trial

A director based on Hallett's design was under construction by Portsmouth Royal Dockyard by the end of 1911 for trial by Vernon.

It was tried in the Second Destroyer Flotilla and the scout cruiser Bellona. These early tests revealed some minor mechanical issues which did not seem insurmountable, and the added demands for voice pipes, circuits and men were seen as problematic. However, the requirement to place the target at a constant compass bearing was just too difficult with the compass presently fitted.

In 1913, the test unit(s) were transferred to the Third Destroyer Flotilla, as the Beagle class was fitted with fore bridge firing gear which it was felt would show the device's advantages. Sometime in 1914, it was decided not to develop the device further.

See Also

• Pitcairn's Director
• H.M.S. Vernon. Annual Report of the Torpedo School, 1911, with Appendix (Wireless Telegraphy). Copy 15 at The National Archives. ADM 189/31.
• H.M.S. Vernon. Annual Report of the Torpedo School, 1912, with Appendix (Wireless Telegraphy). Copy 17 at The National Archives. ADM 189/32.
• H.M.S. Vernon. (Feb 1914) Annual Report of the Torpedo School, 1913, with Appendix (Wireless Telegraphy). Copy 42 at The National Archives. ADM 189/33.
• H.M.S. Vernon. (Jan 1916) Annual Report of the Torpedo School, 1915. C.B. 1166. Copy 1025 at The National Archives. ADM 189/35.