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The efficiency of a contra-rotating propeller is somewhat offset by its mechanical complexity and the added weight of this gearing that makes the aircraft heavier, thus some performance is sacrificed to carry it. Nonetheless, coaxial contra-rotating propellers and rotors have been used in several military aircraft, such as the Tupolev Tu-95 "Bear".
Contra-rotating, also referred to as coaxial contra-rotating, is a technique whereby parts of a mechanism rotate in opposite directions about a common axis, usually to minimise the effect of torque. Examples include some aircraft propellers , resulting in the maximum power of a single piston or turboprop engine to drive two propellers in ...
However, in commercial ships and in traditional machinery arrangement, contra-rotating propellers are rare, due to cost and complexity. ABB provided an azimuth thruster for ShinNihonkai Ferries in form of the CRP Azipod, [2] claiming efficiency gains from the propeller (about 10% increase [3]) and a simpler hull design.
Counter-rotating propellers (CRP) are propellers which turn in opposite directions to each other. [1] They are used on some twin- and multi-engine propeller-driven aircraft. The propellers on most conventional twin-engined aircraft turn clockwise (as viewed from behind the engine). Counter-rotating propellers generally turn clockwise on the ...
The simplest mechanism is the ground-adjustable propeller, which may be adjusted on the ground, but is effectively a fixed-pitch prop once airborne. The spring-loaded "two-speed" VP prop is set to fine for takeoff, and then triggered to coarse once in cruise, the propeller remaining coarse for the remainder of the flight.
The original Y.A.5 was designed to take the new Napier Coupled Naiad turboprop engine, consisting of two single Naiads driving contra-rotating propellers through a common gearbox. This engine was ultimately cancelled, so the Y.A.5 flew as the Y.A.7 with a Rolls-Royce Griffon 56 piston engine driving contra-rotating propellers. This aircraft ...
When the propeller reached a certain RPM, centrifugal force would cause the weights to swing outwards, which would drive a mechanism that twisted the propeller into a steeper pitch. When the propeller slowed, the RPM would decrease enough for the spring to push the weights back in, realigning the propeller to the shallower pitch.
It was propelled by two contra-rotating propellers that were spun by rapidly pulling out wires from drums wound inside the torpedo. Differential speed on the wires connected to the shore station allowed the torpedo to be guided to its target, up to 2,000 yards (1,800 m) away, at speeds of up to 27 knots (31 mph).