PropellerA propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working fluid such as water or air. Propellers are used to pump fluid through a pipe or duct, or to create thrust to propel a boat through water or an aircraft through air.
Propeller (aeronautics)In aeronautics, an aircraft propeller, also called an airscrew, converts rotary motion from an engine or other power source into a swirling slipstream which pushes the propeller forwards or backwards. It comprises a rotating power-driven hub, to which are attached several radial airfoil-section blades such that the whole assembly rotates about a longitudinal axis. The blade pitch may be fixed, manually variable to a few set positions, or of the automatically variable "constant-speed" type.
Variable-pitch propeller (aeronautics)In aeronautics, a variable-pitch propeller is a type of propeller (airscrew) with blades that can be rotated around their long axis to change the blade pitch. A controllable-pitch propeller is one where the pitch is controlled manually by the pilot. Alternatively, a constant-speed propeller is one where the pilot sets the desired engine speed (RPM), and the blade pitch is controlled automatically without the pilot's intervention so that the rotational speed remains constant.
Convective available potential energyIn meteorology, convective available potential energy (commonly abbreviated as CAPE), is the integrated amount of work that the upward (positive) buoyancy force would perform on a given mass of air (called an air parcel) if it rose vertically through the entire atmosphere. Positive CAPE will cause the air parcel to rise, while negative CAPE will cause the air parcel to sink. Nonzero CAPE is an indicator of atmospheric instability in any given atmospheric sounding, a necessary condition for the development of cumulus and cumulonimbus clouds with attendant severe weather hazards.
Lift (force)A fluid flowing around an object exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the force parallel to the flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it is defined to act perpendicular to the flow and therefore can act in any direction. If the surrounding fluid is air, the force is called an aerodynamic force.
Aircraft engineAn aircraft engine, often referred to as an aero engine, is the power component of an aircraft propulsion system. Aircraft using power components are referred to as powered flight. Most aircraft engines are either piston engines or gas turbines, although a few have been rocket powered and in recent years many small UAVs have used electric motors. List of aircraft engines In commercial aviation the major Western manufacturers of turbofan engines are Pratt & Whitney (a subsidiary of Raytheon Technologies), General Electric, Rolls-Royce, and CFM International (a joint venture of Safran Aircraft Engines and General Electric).
Lapse rateThe lapse rate is the rate at which an atmospheric variable, normally temperature in Earth's atmosphere, falls with altitude. Lapse rate arises from the word lapse, in the sense of a gradual fall. In dry air, the adiabatic lapse rate is 9.8 °C/km (5.4 °F per 1,000 ft). At Saturated Air Lapse Rate (SALR), where value is 1.1 °C/1000ft - 2.8 °C/1000ft as obtained from ICAO. It corresponds to the vertical component of the spatial gradient of temperature.
Lee waveIn meteorology, lee waves are atmospheric stationary waves. The most common form is mountain waves, which are atmospheric internal gravity waves. These were discovered in 1933 by two German glider pilots, Hans Deutschmann and Wolf Hirth, above the Krkonoše. They are periodic changes of atmospheric pressure, temperature and orthometric height in a current of air caused by vertical displacement, for example orographic lift when the wind blows over a mountain or mountain range.
SafetySafety is the state of being "safe", the condition of being protected from harm or other danger. Safety can also refer to the control of recognized hazards in order to achieve an acceptable level of risk. There are two slightly different meanings of safety. For example, home safety may indicate a building's ability to protect against external harm events (such as weather, home invasion, etc.), or may indicate that its internal installations (such as appliances, stairs, etc.) are safe (not dangerous or harmful) for its inhabitants.
Single marketA single market, sometimes called common market or internal market, is a type of trade bloc in which most trade barriers have been removed (for goods) with some common policies on product regulation, and freedom of movement of the factors of production (capital and labour) and of enterprise and services. The goal is that the movement of capital, labour, goods, and services between the members is as easy as within them. The physical (borders), technical (standards) and fiscal (taxes) barriers among the member states are removed to the maximum extent possible.
