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# Coffin corner (aerodynamics)

Coffin corner (also known as the aerodynamic ceiling or Q corner) is the altitude at or near which a fast fixed-wing aircraft's stall speed is equal to the critical Mach number, at a given gross weight and G-force loading. [1]

## Airspeed

Airspeed is the speed of an aircraft relative to the air.

## Altitude

Altitude or height (sometimes known as depth) is defined based on the context in which it is used (aviation, geometry, geographical survey, sport, and more).

## Angle of attack

In fluid dynamics, angle of attack (AOA, or \alpha (Greek letter alpha)) is the angle between a reference line on a body (often the chord line of an airfoil) and the vector representing the relative motion between the body and the fluid through which it is moving.

## Center of pressure (fluid mechanics)

The center of pressure is the point where the total sum of a pressure field acts on a body, causing a force to act through that point.

## Critical Mach number

In aerodynamics, the critical Mach number (Mcr) of an aircraft is the lowest Mach number at which the airflow over some point of the aircraft reaches the speed of sound, but does not exceed it.

## Density of air

The density of air, ρ (Greek: rho) (air density), is the mass per unit volume of Earth's atmosphere.

## Drag (physics)

In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) refers to forces acting opposite to the relative motion of any object moving with respect to a surrounding fluid.

## Drag divergence Mach number

The drag divergence Mach number (not to be confused with critical Mach number) is the Mach number at which the aerodynamic drag on an airfoil or airframe begins to increase rapidly as the Mach number continues to increase.

## Dynamic pressure

In incompressible fluid dynamics dynamic pressure (indicated with q, or Q, and sometimes called velocity pressure) is the quantity defined by:Clancy, L.J., Aerodynamics, Section 3.5 where (using SI units): |- | q\; ||.

The Federal Aviation Administration (FAA) is the national aviation authority of the United States.

## Fixed-wing aircraft

A fixed-wing aircraft is an aircraft, such as an aeroplane, which is capable of flight using wings that generate lift caused by the vehicle's forward airspeed and the shape of the wings.

## Flight envelope

In aerodynamics, the flight envelope, service envelope, or performance envelope of an aircraft refers to the capabilities of a design in terms of airspeed and load factor or altitude.

## Flow separation

All solid objects traveling through a fluid (or alternatively a stationary object exposed to a moving fluid) acquire a boundary layer of fluid around them where viscous forces occur in the layer of fluid close to the solid surface.

## G-force

g-force (with g from gravitational) is a measurement of the type of acceleration that causes weight.

## Helicopter

A helicopter is a type of rotorcraft in which lift and thrust are supplied by rotors.

## Helicopter height–velocity diagram

The height–velocity diagram or H/V curve is a graph charting the safe/unsafe flight profiles relevant to a specific helicopter.

## Indicated airspeed

Indicated airspeed (IAS) is the airspeed read directly from the airspeed indicator on an aircraft, driven by the pitot-static system.

## International Standard Atmosphere

The International Standard Atmosphere (ISA) is an atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes or elevations.

## Lift (force)

A fluid flowing past the surface of a body exerts a force on it.

In aeronautics, the load factor is defined as the ratio of the lift of an aircraft to its weight Clancy, section 5.22 Hurt, page 37 and represents a global measure of the stress ("load") to which the structure of the aircraft is subjected: where: Since the load factor is the ratio of two forces, it is dimensionless.

## Lockheed U-2

The Lockheed U-2, nicknamed "Dragon Lady", is a single-jet engine, ultra-high altitude reconnaissance aircraft operated by the United States Air Force (USAF) and previously flown by the Central Intelligence Agency (CIA).

## Mach number

In fluid dynamics, the Mach number (M or Ma) is a dimensionless quantity representing the ratio of flow velocity past a boundary to the local speed of sound.

## Mach tuck

Mach tuck is an aerodynamic effect whereby the nose of an aircraft tends to downward pitch as the airflow around the wing reaches supersonic speeds; the aircraft will first experience this effect at significantly below Mach 1.

## Machmeter

A Machmeter is an aircraft pitot-static system flight instrument that shows the ratio of the true airspeed to the speed of sound, a dimensionless quantity called Mach number.

## Moment (physics)

In physics, moment is a combination of a physical quantity and a distance.

## Shock wave

A shock wave is a type of propagating disturbance.

## Speed of sound

The speed of sound is the distance travelled per unit time by a sound wave propagating through an elastic medium.

## Stall (fluid mechanics)

In fluid dynamics, a stall is a reduction in the lift coefficient generated by a foil as angle of attack increases.

## Statics

Statics is the branch of mechanics that is concerned with the analysis of loads (force and torque, or "moment") on physical systems in static equilibrium, that is, in a state where the relative positions of subsystems do not vary over time, or where components and structures are at a constant velocity.

## Structural integrity and failure

Structural integrity and failure is an aspect of engineering which deals with the ability of a structure to support a designed load (weight, force, etc...) without breaking, tearing apart, or collapsing, and includes the study of breakage that has previously occurred in order to prevent failures in future designs.

## Tailplane

A tailplane, also known as horizontal stabiliser (and horizontal stabilizer in the US), is a small lifting surface located on the tail (empennage) behind the main lifting surfaces of a fixed-wing aircraft as well as other non-fixed-wing aircraft such as helicopters and gyroplanes.

## Thrust

Thrust is a reaction force described quantitatively by Newton's second and third laws.

## Tropopause

The tropopause is the boundary in the Earth's atmosphere between the troposphere and the stratosphere.

## True airspeed

The true airspeed (TAS; also KTAS, for knots true airspeed) of an aircraft is the speed of the aircraft relative to the airmass in which it is flying.

## Turbulence

In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic property changes.

## United States

The United States of America (USA), commonly referred to as the United States (U.S.) or America, is a federal republic composed of 50 states, a federal district, five major territories and various possessions.

## Weight

In science and engineering, the weight of an object is usually taken to be the force on the object due to gravity.

## References

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