It projected small anti-submarine bombs simultaneously, ten from each side of the ship's forecastle, each containing 20 lb (9.1 kg) of explosive.
[2] The Department of Miscellaneous Weapons Development (the Wheezers and Dodgers) were advocating the multiple spigot mortar that would become Hedgehog.
By firing these mortars ahead instead and by using a smaller, streamlined and faster-sinking projectile, the hope was to destroy a target submarine before ASDIC contact had been lost.
[2] The initial Fairlie projectile was lightweight, limited by the power of the propellant charge and the strength of the deck to support the mortar.
This was recognised to be too light for service use and a developed version would need to be heavier, more powerful and with a more robust mounting on the ship.
A similar problem beset the Thornycroft projector which used heavy charges and was limited to only five, an inadequate pattern, if they were to be thrown far enough to still be ahead of the ship when they detonated.
[8] Fairlie's mortar bombs carried only 20 lb (9.1 kg) of explosive filling and used a lead ballast weight to keep them nose-down for faster sinking.
They had faith in their ASDIC detection and the ability to aim a small number of powerful weapons close to a target but lacked political support to develop this further.
[8] The launcher was well thought out for ease of operation and could be tilted horizontally, to allow re-loading with a simple trolley, rather than the vertical lift on davits that the Thornycroft had required, and which would have made it impossible to reload in most mid-Atlantic conditions.
They were shaped to sink quickly and predictably and had a clockwork time fuze, which was set automatically between loading and firing.
This was better synchronised than a hydrostatic fuze and the charges were intended to detonate simultaneously around the target, giving a combined shock wave.