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In aviation, relaxed stability refers to the tendency of an aircraft to change its attitude and angle of bank on its own accord. An aircraft with relaxed stability will oscillate in simple harmonic motion around a particular attitude at an increasing amplitude. Image File history File links Broom_icon. ... Simple harmonic motion is the motion of a simple harmonic oscillator, a motion that is neither driven nor damped. ...

This can be contrasted with the tendency of an aircraft with positive stability, which, when trimmed to fly at a certain attitude, will continue to do so in the absence of control input, and will oscillate in simple harmonic motion on a decreasing scale around the trimmed attitude, eventually returning to its trimmed attitude. A positively stable aircraft will also resist any bank movement. A Cessna 152 is an example of a stable aircraft. Similarly, an aircraft with "neutral stability" will not return to its trimmed setting without control input, but will oscillate in simple harmonic motion around the trimmed setting continuously and be susceptible to bank influences. The Cessna 152 is a two-seat, fixed tricycle gear, general aviation airplane, used primarily for flight training, touring, and personal flying. ...

Methods of decreasing stability in design

The Lockeed F-117 Nighthawk is not an inherently stable design.

Modern aircraft and in particular low observable designs often exhibit relaxed stability as a result of their design. The Lockheed F-117 Nighthawk for instance employs a highly non-traditional fuselage and wing shape in order to reduce its radar cross section and enable it to penetrate air defences with relative impunity. However the flat facets of the design reduce its stability to the point where a digital fly-by-wire system was required to allow safe operation. The difficulty in flying such an aircraft without fly-by-wire can be illustrated by the proof of concept vehicle developed prior to the Nighthawk, Have Blue. This was a smaller design based upon similar principles of reducing radar cross section, and was successfully implemented, however both prototypes were lost in accidents while testing due to their instability. USAF F-117 Nighthawk from af. ... USAF F-117 Nighthawk from af. ... The United States Air Forces F-117A Nighthawk is the worlds first operational aircraft designed to exploit low-observable stealth technology. ... Lockheed/BAE/Northrop F-35 Lockheed Trident missile C-130 Hercules; in production since the 1950s, now as the C-130J Lockheed Martin (NYSE: LMT) is an aerospace manufacturer formed in 1995 by the merger of Lockheed Corporation with Martin Marietta. ... The United States Air Forces F-117A Nighthawk is the worlds first operational aircraft designed to exploit low-observable stealth technology. ... Typical RCS diagram (B-26 Invader) Radar cross section (RCS) describes the extent to which an object reflects an incident electromagnetic wave. ... A flight control system consists of the flight control surfaces, the respective cockpit controls, connecting linkage, and necessary operating mechanisms to control aircraft in flight. ...

The latest generation of fighter aircraft often employ design elements which reduce stability to increase maneuverability. The BAE Harrier GR7/GR9 employs a significant and obvious anhederal angle to its wings, while the wings are mounted high on the fuselage the anhedral reduces inherent stability in the roll axis. BAE Systems plc is the worlds fourth largest defence contractor,[3] the largest in Europe and a commercial aerospace manufacturer. ... The BAE Systems/Boeing Harrier II (GR5, GR7, and GR9 series) is a second generation vertical/short takeoff and landing (V/STOL) jet aircraft used by the Royal Air Force (RAF) and, since 2006, the Royal Navy. ...

Horizontal wing position

The horizontal positioning of wing changes the roll stability of an aircraft.

• An aircraft with a "high" wing position (i.e., set on top of the fuselage) has a higher roll stability. A Cessna 152 is an example.
• An aircraft with a "low" wing (i.e., underneath the fuselage) has less roll stability. A Piper Pawnee is an example of a "low" wing.

In order to visualize how this works, consider the difference between balancing and hanging. Because the Center of Gravity is under the wing in a high wing, the wing essentially "carries" the aircraft from above. Because the center of gravity is above the wing in a low wing, the wing "holds up" the aircraft from below. This means that if the aircraft begins to roll, it will tend to roll more, since the weight of the fuselage will no longer be centered over the wings. The Cessna 152 is a two-seat, fixed tricycle gear, general aviation airplane, used primarily for flight training, touring, and personal flying. ... The PA-25 Pawnee was a very popular agricultural aircraft produced by Piper Aircraft. ... In physics, the center of mass of a system of particles is a specific point at which, for many purposes, the systems mass behaves as if it were concentrated. ...