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The two craft were operated most of the time they spent in RAF service as experimental craft. One source indicates the two craft were built to complement the SARO Princess flying boats which spent many years ashore unused at Calshot. The same source indicates that the fortunes of the Firefloat Mk2 faded with those of the flying boats. Whilst in service the two craft were reported to have rocket like acceleration and could stop in their own length, once the automatic time delay of 7 seconds on the reverse gear cut in. This is borne out in that the craft had a turning circle of two boat lengths at 13 knots and three boat lengths at 28.5 knots.
The hull of the 46ft FireFloats, often referred to as Crash Boats, was of the hard chine type, built of double-skin mahogany on birch plywood framing. Bulkheads divided the craft into five compartments: fore peak, fore cabin and wheelhouse, sick bay, engine room, cockpit and after peak. The main engines were twin Rover Meteorite petrol units, developing 375 hp each at 2,400 rpm. The units were marinized versions of the Meteorite engines developed for military transport. Each engine had eight cylinders of 5.4ins bore and 6ins stroke, in two banks of four set at 60 degrees, the capacity being 1,099 cubic ins. The compression ratio was 6-1. Mathway hydraulically operated reverse gearboxes were employed, with direct drive, and the engines were controlled from the wheelhouse. Both engines rotated anti-clockwise. Three-bladed propellers of 19½ diameter and 17Ό pitch were used, and with the engines running at 2,400 rpm a speed of 28 knots was attained.
Fire fighting was carried out by two 3½ hand-operated monitors which were suitable for foam or water, each being fitted with a hinged 1 nozzle for use with water. The pumping engine was a Ford V-8, which drove a rotary vane pump manufactured by Sun Engineering (Richmond), Ltd and designed to deliver 2,250-2,500 gpm of foam at 1,800 rpm (pump speed) or 500-600 gpm of water at 500 rpm. The same pump, connected to a suction hose, was employed for salvage pumping, the water being discharged through the monitors. A spring-loaded towing hook was fitted abaft the engine room casing and was designed for towing a flying boat and had an overload release of 10,000 lb. Rescue equipment carried included breaking in tools, line throwing rockets, a crash ladder, stretchers and a portable deck davit with winch.
The craft was built with the hull decked in, except for the after cockpit, and with raised casings provided over the engine room, sick bay and fore cabin. It was considered that the arrangement gave the maximum working space on deck, consistent with reasonable head room below. A watertight bulkhead separated the fore peak from the fore cabin and there were watertight bulkheads at each end of the engine room. The fore peak was arranged as an anchor cable locker and was accessed through a watertight panel. The wheelhouse, with raised floor, was arranged between the galley and the sick bay. The helmsmans position was on the centreline; there were windows giving an all-round view and a Kent Clear View screen was provided for the window in front of the wheel. The control for an 11 inch searchlight was fitted in the roof above the helmsman's position. Radio equipment was mounted on a shelf on the port side opposite the galley and comprised one type 1143A transmitter/receiver for VHF.
The sick bay, aft of the wheelhouse, had a settee at each side. The roofs of both the wheelhouse and sick bay were heat insulated with Isoflex and the windows were of Perspex.
The cockpit was formed by a flat over the after peak and foam compound tanks were fitted along each side. Stowage was provided for deck equipment and boxes contained the crash equipment and flares. Stowage was also provided for batteries in the after peak. Positive cam-type steering gear was employed. Twin rudders were fitted, the blades and stocks being of nickel aluminium bronze cast in one piece and housed in bearings and glands of similar metal. The main engines were carried by resilient mountings on sub-frames. The engines were of the dry sump type, with fresh water cooling, and the forward end of each sub-frame also carried the lubricating oil service tank, oil filters, oil thermostat and a combined oil and water cooler. The whole assembly could be lifted and transported as a single unit. A Silentbloc flexible coupling connected each engine to its propeller shaft. The shafts were carried in stern tubes equipped with Cutless rubber bearings, lubricated by circulating water bled from the engines sea water system. The stern tube glands were flexibly mounted an the stern tube by laminated rubber sleeves. The propeller shafts were of Monel metal and the brackets were of aluminium bronze, with Cutless bearings.
One main engine fuel tank of 270 gallons capacity was fitted in a gas tight compartment, between the engine room and sick bay. Water-jacketted copper exhaust pipes were employed in the engine room; near the after bulkhead the cooling water was injected into the exhaust pipes, the after lengths of which were of rubber and discharged through the transom. Flaps were provided for the outlets to prevent the ingress of water. Plessey cartridge starters were employed for the main engines. A 288 watt, 32 volt electric generating set, driven by a J.A.P. 2A petrol engine, was mounted on a shelf at the starboard end of the engine room and a fuel tank of 7 gallons capacity was fitted on the after bulkhead. This fuel tank also supplied the Ford V-8 pumping engine. A gear-type bilge pump was also driven by the auxiliary engine. There were two batteries, each of 12 volts and 100 amp hours, arranged in series. In addition to the auxiliary generating set a 24 volt C.A.V. Dynamo was driven by each main engine.
The craft was fitted with two oil service tanks each of 9 gallons capacity and two reserve oil tanks each of 7 gallons capacity. Fresh water was supplied from a tank of capacity 10 gallons. A separate distilled water tank of 9 gallons capacity was fitted for supplying water to the heat exchanger unit. Ventilation for the engine room and forward accommodation was by forced and natural draught, whereas that for the fore peak, sick bay, tank space and after peak was natural draught. The engine room and tank space were fitted with piping and sprays for methyl bromide fire extinguishing supplied from a 2 gallon fire extinguisher. Two methyl bromide Mk25 fire extinguishers were also fitted. Ground tackle consisted of a Danforth anchor with a Nylon cable. The listed duties of the 46ft Firefloat Mk2 were crash rescue, fire fighting, and salvage pumping. The craft was operated by a crew of 5 .
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