A fluid flowing around the surface of 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 can act in any direction at right angles to the flow.
Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In other words, if the axis of rotation of a body is itself rotating about a second axis, that body is said to be precessing about the second axis. A motion in which the second Euler angle changes is called nutation. In physics, there are two types of precession: torque-free and torque-induced.
Freeflying is a skydiving discipline which began in the late 1980s, involving freefalling in various vertical orientations, as opposed to the traditional "belly-to-earth" orientation. The discipline is known to have originated when Olav Zipser began experimenting with non-traditional forms of bodyflight. Zipser founded the FreeFly Clowns as a two-person competitive team with Mike Vail in 1992, and was joined by Omar Alhegelan, Charles Bryan, and Stefania Martinengo in 1994. The FreeFly Clowns are also credited with opening the first school to teach freeflying, The First School of Modern SkyFlying.
Flight is the process by which an object moves through an atmosphere without contact with the surface. This can be achieved by generating aerodynamic lift associated with propulsive thrust, aerostatically using buoyancy, or by ballistic movement.
Wind shear, sometimes referred to as wind gradient, is a difference in wind speed or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizontal wind shear. Vertical wind shear is a change in wind speed or direction with change in altitude. Horizontal wind shear is a change in wind speed with change in lateral position for a given altitude.
In fluid dynamics, angle of attack is the angle between a reference line on a body and the vector representing the relative motion between the body and the fluid through which it is moving. Angle of attack is the angle between the body's reference line and the oncoming flow. This article focuses on the most common application, the angle of attack of a wing or airfoil moving through air.
Jet force is the exhaust from some machine, esp. aircraft, propelling the object itself in the opposite direction as per Newton's Third Law. An understanding of jet force is intrinsic to the launching of drones, satellites, rockets, airplanes and other airborne machines.
Wingsuit flying is the sport of flying through the air using a wingsuit which adds surface area to the human body to enable a significant increase in lift. The modern wingsuit, first developed in the late 1990s, creates a surface area with fabric between the legs and under the arms. Wingsuits are sometimes referred to as "birdman suits", "squirrel suits", and "bat suits".
Flight mechanics are relevant to fixed wing and rotary wing (helicopters) aircraft. An aeroplane, is defined in ICAO Document 9110 as, "a power-driven heavier than air aircraft, deriving its lift chiefly from aerodynamic reactions on surface which remain fixed under given conditions of flight".
Retreating blade stall is a hazardous flight condition in helicopters and other rotary wing aircraft, where the retreating rotor blade has a lower relative blade speed, combined with an increased angle of attack, causing a stall and loss of lift. Retreating blade stall is the primary limiting factor of a helicopter's never exceed speed, VNE.
Tracking, a basic freefall skill learned by a novice skydiver, is the technique of assuming a body position that allows the skydiver to move horizontally while freefalling.
A tailwind is a wind that blows in the direction of travel of an object, while a headwind blows against the direction of travel. A tailwind increases the object's speed and reduces the time required to reach its destination, while a headwind has the opposite effect.
An aircraft stabilizer is an aerodynamic surface, typically including one or more movable control surfaces, that provides longitudinal (pitch) and/or directional (yaw) stability and control. A stabilizer can feature a fixed or adjustable structure on which any movable control surfaces are hinged, or it can itself be a fully movable surface such as a stabilator. Depending on the context, "stabilizer" may sometimes describe only the front part of the overall surface.
Adverse yaw is the natural and undesirable tendency for an aircraft to yaw in the opposite direction of a roll. It is caused by the difference in lift and drag of each wing. The effect can be greatly minimized with ailerons deliberately designed to create drag when deflected upward and/or mechanisms which automatically apply some amount of coordinated rudder. As the major causes of adverse yaw vary with lift, any fixed-ratio mechanism will fail to fully solve the problem across all flight conditions and thus any manually operated aircraft will require some amount of rudder input from the pilot in order to maintain coordinated flight.
Dissymmetry of lift in rotorcraft aerodynamics refers to an uneven amount of lift on opposite sides of the rotor disc. It is a phenomenon that affects single-rotor helicopters and autogyros in forward flight.
The cyclogyro, or cyclocopter, is an aircraft configuration that uses a horizontal-axis cyclorotor as a rotor wing to provide lift and sometimes also propulsion and control. In principle, the cyclogyro is capable of vertical take off and landing and hovering performance like a helicopter, while potentially benefiting from some of the advantages of a fixed-wing aircraft.
Parachuting is a method of transiting from a high point to Earth with the aid of gravity, involving the control of speed during the descent using a parachute or parachutes. It may involve more or less free-falling which is a period when the parachute has not yet been deployed and the body gradually accelerates to terminal velocity.
3D Aerobatics or 3D flying is a form of flying using flying aircraft to perform specific aerial maneuvers. They are usually performed when the aircraft had been intentionally placed in a stalled position.
The Course Setting Bomb Sight (CSBS) is the canonical vector bombsight, the first practical system for properly accounting for the effects of wind when dropping bombs. It is also widely referred to as the Wimperis sight after its inventor, Harry Wimperis.
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