British Power Boat Company Type Two 63 ft HSL

Whaleback HSL 164 off Colombo with a Hurricane overhead
Class overview
Name:	Type Two 63 ft HSL
Builders:	British Power Boats
Operators:	RAF, UK
General characteristics
Type:	High speed launch
Displacement:	21.5 tons
Length:	63 ft
Beam:	17 1⁄2 ft
Draught:	3 3⁄4 ft
Propulsion:	3 × Napier Sea Lion each of 500 hp (373 kW)
Speed:	36 kn (67 km/h)
Range:	500 miles (800 km)
Complement:	9 (including captain and a medical orderly)
Armament:	2 × 0.303 machine guns

The Type Two HSL was a 63 feet (19 m) high speed launch craft made by British Power Boat Company (BPBC). The craft were used during the Second World War for air-sea rescue operations to save Allied aircrew from the sea. The Type Two superseded the 64 feet (20 m) high speed launch, and itself was replaced by the 68 feet (21 m) Type Three HSL also built by the BPBC. It was nicknamed the 'Whaleback' due to the distinctive curve to its deck and humped cabin.

The Type Two was designed in 1937 by Hubert Scott-Paine, founder of the British Power Boat Company at Hythe. Scott-Paine had previously owned the Supermarine Aviation Company, later builders of the Supermarine Spitfire and several flying boat types.

A low set cabin contained the wheel-house, chart room and a sickbay. For defence against enemy aircraft, on top of the cabin were two aircraft-style turrets made by Armstrong-Whitworth initially with a single .303 in Vickers machine gun or Lewis gun (this was later improved - see Variants below). The mahogany hull was of the hard chine, planing type.

During the Second World War, the retrieval of pilots and aircrew that had been shot down over, or that had had to ditch, in the sea around the British Isles was the responsibility of the Royal Air Force Air Sea Rescue Service, (motto: "The sea shall not have them"). Rescue of downed aircrew was coordinated using RAF aircraft, aircraft operated by Coastal Command and the Royal Navy and rescue launches operated by the RAF Marine Craft Service and the Royal Navy.