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    Controllable pitch propeller

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      This article needs additional citations for verification. Please help by adding citations to reliable sources. Unsourced material may be challenged and removed. (July 2010) A controllable pitch propeller (CPP) or variable pitch propeller is a type of propeller with blades that can be rotated around their long axis to change their pitch. Roe and Louis Breguet. The French aircraft firm Levasseur displayed a variable pitch propeller at the 1921 Paris Airshow which it claimed had been tested by the French government in a ten-hour run and could change pitch at any engine rpm.[2] Dr Henry Selby Hele-Shaw and T E Beacham patented an hydraulically-operated variable-pitch propeller (based on a variable stroke pump) in 1924 and presented a paper on the subject before the Royal Aeronautical Society in 1928, though it was received with scepticism as to its utility.[3] The propeller had been developed with Gloster - as the "Gloster Hele-Shaw Beachem" - and was demonstrated on a Gloster Grebe where it was used to maintain a near-constant rpm.[4] The first practical controllable pitch propeller for aircraft was introduced in 1932.[5] Such propellers are used in propeller-driven aircraft to adapt the propeller to different thrust levels and air speeds so that the propeller blades don't stall, hence degrading the propulsion system's efficiency. Especially for cruising, the engine can operate in its most economical range of rotational speeds. With the exception of going into reverse for braking after touch-down, the pitch is usually controlled automatically without the pilot's intervention. A propeller with a controller that adjusts the blades' pitch so that the rotational speed always stays the same is called a constant speed propeller. A propeller with controllable pitch can have a nearly constant efficiency over a range of airspeeds.[6] The most common type of controllable pitch propeller is hydraulically actuated; it was originally developed by Frank W. Caldwell of the Hamilton Standard Division of the United Aircraft Company. This design led to the award of the Collier Trophy of 1933.[7] de Havilland subsequently bought up the rights to produce Hamilton propellers in the UK, while the British company Rotol was formed to produce its own designs. The French company of Pierre Levasseur and the US Smith Engineering Co. also developed controllable pitch propellors. Smith propellers were used by Wiley Post on some of his flights. As experimental aircraft and microlights have become more sophisticated, it has become more common for such light aeroplanes to fit variable-pitch propellers, both ground-adjustable propellers and in-flight-variable propellers. Hydraulic operation is too expensive and bulky, and instead light aircraft use propellers that are activated mechanically or electrically. Some are manually operated, some are controlled by electronics; and one, the "Silence V-Prop",[8] is fully self-powering and self-adjusting. Controllable pitch propellers (CPP) for marine propulsion systems have been designed to give the highest propulsive efficiency over a broad range of speeds and load conditions. When the vessel is fully loaded with cargo the propulsion power required at a given ship speed is much higher than when the vessel is empty. By adjusting the blade pitch, the optimum efficiency can be obtained and fuel can be saved. when the sails are used instead). This is the marine equivalent of "feathering" an aeronautical propeller. A fixed pitch propeller (FPP) is more efficient than a controllable pitch propeller under a specific rotational speed and load condition. At that particular rotational speed and load, an FPP can transmit power more efficiently than a CPP. At any other rotational speed, or any other vessel loading, the FPP will not be more efficient, either being over pitched or under pitched. A correctly sized controllable pitch propeller can be efficient for a wide range of Replica Cartier Montre rotational speeds, since pitch can be adjusted to absorb all the power that the engine is capable of producing at nearly any rotational speed. The CPP does not improve manoeuverability of a vessel. When maneuvering the vessel the advantage of the FPP is the fast change of propulsion direction. The direction of thrust with a CPP can be changed by moving the pitch of the blade, this takes more time then a gearbox. Also a CPP has constant moving water around the aftship due to propellor rotation. With a gearbox one can de-clutch the propellor. The advantage of a CPP is the possibility of using a shaft generator and using engine power output for generating electricity. A reversing gear or a reversible engine is not necessary for ships utilizing CPP, saving money to install and service these components. Depending on the main engine rotational speed and the size of the CPP, a reduction gear may still be required. A CPP does require a hydraulic system to control the position of the blades. A CPP does not produce more or less wear or stress on the propeller shaft or propulsion engine than an FPP. Therefore this will not be an argument to choose between an FPP GaGa Milano Manuale 40MM Gold Plated Imitation or a CPP. Large vessels that make long trips at a constant service speed, for example crude oil tankers or the largest container ships, do not utilize a CPP as the capital and running costs far outweigh the small improvement in manoeuverability and reduced requirement for starting air. Uljanik shipyard in Yugoslavia produced a series of four VLCCs with variable pitch propellers in the mid-seventies. The first three vessels were ore/oil carriers, the fourth a pure tanker. They were each powered by two 20,000 bhp B W diesel engines directly driving Kamewa variable pitch propellers. Due to the high construction cost none of these vessels ever returned a profit over their lifetimes. A CPP is usually found on harbour or ocean-going tugs, dredgers, cruise ships, ferries, cargo vessels and larger fishing vessels. Prior to the development of CPPs, some vessels would alternate between "speed wheel" and "power wheel" propellers depending on the task. Controllable pitch propeller This article needs additional citations for verification. Please help by adding citations to reliable sources. Unsourced material may be challenged and removed. (July 2010) A controllable pitch propeller (CPP) or variable pitch propeller is a type of propeller with blades that can be rotated around their long axis to change their pitch. Roe and Louis Breguet. The French aircraft firm Levasseur displayed a variable pitch propeller at the 1921 Paris Airshow which it claimed had been tested by the French government in a ten-hour run and could change pitch at any engine rpm.[2] Dr Henry Fake Red Watches Selby Hele-Shaw and T E Beacham patented an hydraulically-operated variable-pitch propeller (based on a variable stroke pump) in 1924 and presented a paper on the subject before the Royal Aeronautical Society in 1928, though it was received with scepticism as to its utility.[3] The propeller had been developed with Gloster - as the "Gloster Hele-Shaw Beachem" - and was demonstrated on a Gloster Grebe where it was used to maintain a near-constant rpm.[4] The first practical controllable pitch propeller for aircraft was introduced in 1932.[5] Such propellers are used in propeller-driven aircraft to adapt the propeller to different thrust levels and air speeds so that the propeller blades don't stall, hence degrading the propulsion system's efficiency. Especially for cruising, the engine can operate in its most economical range of rotational speeds. With the exception of going into reverse for braking after touch-down, the pitch is usually controlled automatically without the pilot's intervention. A propeller with a controller that adjusts the blades' pitch so that the rotational speed always stays the same is called a constant speed propeller. A propeller with controllable pitch can have a nearly constant efficiency over a range of airspeeds.[6] The most common type of controllable pitch propeller is hydraulically actuated; it was originally developed by Frank W. Caldwell of the Hamilton Standard Division of the United Aircraft Company. This design led to the award of the Collier Trophy of 1933.[7] de Havilland subsequently bought up the rights to produce Hamilton propellers in the UK, while the British company Rotol was formed to produce its own designs. The French company of Pierre Levasseur and the US Smith Engineering Co. also developed controllable pitch propellors. Smith propellers were used by Wiley Post on some of his flights. As experimental aircraft and microlights have become more sophisticated, it has become more common for such light aeroplanes to fit variable-pitch propellers, both ground-adjustable propellers and in-flight-variable propellers. Hydraulic operation is too expensive and bulky, and instead light aircraft use propellers that are activated mechanically or electrically. Some are manually operated, some are controlled by electronics; and one, the "Silence V-Prop",[8] is fully self-powering and self-adjusting. Controllable pitch propellers (CPP) for marine propulsion systems have been designed to give the highest propulsive efficiency over a broad range of speeds and load conditions. When the vessel is fully loaded with cargo the propulsion power required at a given ship speed is much higher than when the vessel is empty. By adjusting the blade pitch, the optimum efficiency can be obtained and fuel can be saved. when the sails are used instead). This is the marine equivalent of "feathering" an aeronautical propeller. A fixed pitch propeller (FPP) is more efficient than a controllable pitch propeller under a specific rotational speed and load condition. At that particular rotational speed and load, an FPP can transmit power more efficiently than a CPP. At any other rotational speed, or any other vessel loading, the FPP will not be more efficient, either being over pitched or under pitched. A correctly sized controllable pitch propeller can be efficient for a wide range of rotational speeds, since pitch can be adjusted to absorb all the power that the engine is capable of producing at nearly any rotational speed. The CPP does not improve manoeuverability of a vessel. When maneuvering the vessel the advantage of the FPP is the fast change of propulsion direction. The direction of thrust with a CPP can be changed by moving the pitch of the blade, this takes more time then a gearbox. Also a CPP has constant moving water around the aftship due to propellor rotation. With a gearbox one can de-clutch the propellor. The advantage of a CPP is the possibility of using a shaft generator and using engine power output for generating electricity. A reversing gear or a reversible engine is not necessary for ships utilizing CPP, saving money to install and service these components. Depending on the main engine rotational speed and the size of the CPP, a reduction gear may still be required. A CPP does require a hydraulic system to control the position of the blades. A CPP does not produce more or less wear or stress on the propeller shaft or propulsion engine than an FPP. Therefore this will not be an argument to choose between an FPP or a CPP. Large vessels that make long trips at a constant service speed, for example crude oil tankers or the largest container ships, do not utilize a CPP as the capital and running costs far outweigh the small improvement in manoeuverability and reduced requirement for starting air. Uljanik shipyard in Yugoslavia produced a series of four VLCCs with variable pitch propellers in the mid-seventies. The first three vessels were ore/oil carriers, the fourth a pure tanker. They were each powered by two 20,000 bhp B W diesel engines directly driving Kamewa variable pitch propellers. Due to the high construction cost none of these vessels ever returned a profit over their lifetimes. A CPP is usually found on harbour or ocean-going tugs, dredgers, cruise ships, ferries, cargo vessels and larger fishing vessels. Prior to the development of CPPs, some vessels would alternate between "speed wheel" and "power wheel" propellers depending on the task.

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