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In aeronautics, blade pitch refers to the angle of the blades of an aircraft propeller or helicopter rotor. Blade pitch is measured relative to the aircraft body. It is usually described as "fine" or "low" for a more vertical blade angle, and "coarse" or "high" for a more horizontal blade angle.
If a helicopter suffers a power failure a pilot can adjust the collective pitch to keep the rotor spinning, generating enough lift to touch down and skid in a relatively soft landing. [ 3 ] The collective pitch control in a Boeing CH-47 Chinook is called a thrust control , but serves the same purpose, except that it controls two rotor systems ...
A constant-speed propeller is a variable-pitch propeller that automatically changes its blade pitch in order to maintain a chosen rotational speed, regardless of the operational conditions of the aircraft. This is achieved by use of a constant-speed unit (CSU) or propeller governor, which automatically changes the propeller's blade pitch.
1. Non-rotating outer ring (blue). 2. Turning inner ring (silver). 3. Ball joint. 4. Control (pitch) preventing turning of outer ring. 5. Control (roll). 6. Linkages (silver) to the rotor blade. In aeronautics, a swashplate is a mechanical device that translates input via the helicopter flight controls into motion of the main rotor blades.
The sizes of these regions vary with the blade pitch, rate of descent, and rotor rotational speed. When changing autorotative rotational speed, blade pitch, or rate of descent, the sizes of the regions change in relation to each other. The driven region, also called the propeller region, is the region at the end of the blades.
A rigid rotorhead has no flapping or lag hinges but does have pitch change bearings. The flapping and lagging movement is accommodated by flexible sections (commonly elastomeric bearings) at the blade root or blade attachment. When using composite blades, the blades can also flex to provide a flapping motion. Benefits of rigid rotor system are:
An example of two-blade rotor is the Bell 212, and four blade version of this helicopter is the Bell 412. [23] An example of the effect of rotor blade number is the UH-72 ( EC145 variant ); the A model had four blades, but the UH-72B was changed to five blades which reduced vibration. [ 24 ]
Detail of the pitch control mechanism of an EC135 Fenestron. Increased safety for people on the ground because the enclosure provides peripheral protection. [5] [18] Greatly reduced noise and vibration due to the enclosure of the blade tips and greater number of blades. [5] [18] A decrease in power requirements during the cruise phase of flight ...