Propulsion

Machinery
The torpedo boats of the Spica series were the first Swedish warships to be equipped with gas-turbine engines. Each ship has three Bristol Siddley Proteus gas turbines of 4 250 HP.
With their small size and low weight they could be installed far aft, providing ample space for comfortable cabins and mess-rooms, as well as spacious centres for command functions and engines.
The gas-turbine machinery has a short starting time, good manoeuvrability, and a top speed in excess of 40 knots. One, two, or three engines can be engaged, giving approximate speeds of 12 knots (one engine), 27 knots (two engines), or >40 knots (three engines).
Start and switch-in of turbines can be made during propulsion, so that one or two turbines are used at low speeds, and when engaging enemy targets all three engines are used for maximum speed. The turbines are remote-controlled from a noise-protected engine centre.
KaMeWa-propellers with controllable pitch enable fast, smooth manoeuvring and speed control directly from the bridge. The aft space of the deck is dominated by the air intake for the gas turbines.

Technical data for gas turbine GT1:

	Design		12-stage axial compressor and one stage with centrifugal compressor. 2-stage compressor turbine. 2-stage power turbine
	Primary reduction gear		Allen Stoeckicht planetary gearbox
	Reduction gear I/O-ratio		0,4516:1
	Speed of output shaft		Max 5250 rpm
	Engine length		298 cm
	Engine width		117 cm
	Weight, with fuel and oil		1553 kg
	Fuel consumption, full power		Approx. 1000 kg/h
	Fuel consumption, idling		181-227 kg/h
	Air flow		Approx. 73,4 tons/h (20,4 kg/s)
	Output shaft HP, max output		4308 ± 1% (approx. 2,8 HP/kg engine weight. Compare with the T26 petrol engine, with 1 HP/kg engine weight)
	Exhaust temperature		495 °C (650 °C during start-up and acceleration)

Propellers
The propeller arrangement is of type KaMeWa-typ, that is, the blades have controllable pitch for stepless regulation of speed. The KaMeWa-propeller, further developed from the Kaplan-hub, yields several advantages, such as:
Possibility of using full output power from the ship machinery. By varying the pitch of the propeller it is possible always to apply maximum engine power.
In multi-shaft installations, one or more propeller shafts can be disabled (by variation of the pitch) and the operating propeller(s) can be adjusted to the power available.
Ship manoeuvrability is considerably improved relative to conventional arrangements.
Stop distance can be reduced to about 40 % compared to that of fixed propellers.
When assuming bridge manoeuvring, the system for remote control is simple in comparison to an installation with fixed propellers.
Optionally, shaft-driven generators and pumps can be connected.

Propellers on the Spica are designated 33L/3 or RB (K-39). They are made of stainless steel and equipped with three blades each.