Principles of Flight - Section D - Stability

An inherently stable airplane is easy to fly.

It reduces pilot fatigue.

This quality is essential throughout a wide range fo flight conditions.

You will see that handling characteristics are directly related to stability.

Stability is a characteristic of an airplane in flight that causes it to return to a condition of equilibrium, or steady flight, after it is disurbed.

Maneuverability is the characteristic of an airplane that permits you to maneuver it easily and allows it to withstand the stress resulting from the maneuvers.

Controllability is the capability of an airplane to respond to your control inputs, especially with regard to attitude and flight path.

Somewhat less stable.

The initial tendency.

It tends to return to its original attitude after displacement.

A tendency to move farher away from the original attitude following a disturbance is negative static stability.

It is determined by its tendency to oscillate and damp out successive oscillations.

When you consider the overall stability of an airplane.

This is accomplished during the engineering and development phase.

The center of pressure is a point along the wing chord line where lift is considered to be concentrated. For this reason, the center of pressure is often referred to as the center of lift.

The location of the center of gravity with respect to the center of lift determines the longitudinal stability of an airplane.

The nose heavy tendency is ofset by the position if the horizontal stabilizer.

Pitching tendency occurs due to the reduction of downwash from the wings and the propeller.

The alignment of thrust in realation to the longitudinal axis.

A canard is a stabilizer that is located in front of the main wings.

Dihedral is the upward angle of the airplane’s wings with respect to the horizontal.

When you look at an airplane, dihedral makes the wings appear to form a spread out V.

This causes an immediate side slip downward toward the low wing.

This keel effect is the steadying influnce exerted by the side area of the fuselage and vertical stabilizer.

The wings taper backward from the root of the wing to the wingtips. This is called sweepback.

If an airplane with sweepback inadvertently rolls about its logitudinal axis and side slip occurs.

Essentially, an airplane in flight is much like a weather vane.

This arrangment helps keep the airplane aligned with the relative wind.

Dutch roll is a combination of rolling/yawing oscillations caused either by control input or by wind gusts.

If the Dutch roll tendecy is not effectively dampened, it is considered objectionable.

The dutch roll motion is adequately suppressed.

In a light, training airplane a spin may be defined as an aggravated stall which results in autorotation.

These kinds of distractions are another causal factor in stall/spin accidents.

dense air