Static And Dynamic Stability

Question 1

Stability

Answer 1

The inherent quality of an airplane to correct for conditions that may disturb its equilibrium, and to return or to continue the original flightpath.

Question 2

Maneuverability

Answer 2

The quality of an airplane that permits it to be maneuvered easily and to withstand the stresses imposed by maneuvers.

Question 3

Controllability

Answer 3

The capability of an airplane to respond to the pilot’s control, especially with regard to flightpath and attitude.

Question 4

Equilibrium

Answer 4

All opposing forces acting on the airplane are balanced.

Question 5

Static stability

Answer 5

The initial tendency that the airplane displays after its equilibrium is disturbed.

Question 6

Positive static stability

Answer 6

The initial tendency of the airplane to return to the original state of equilibrium after being disturbed.

Question 7

Neutral static stability

Answer 7

The initial tendency of the airplane to remain in a new condition after its equilibrium has been disturbed.

Question 8

Negative static stability

Answer 8

The initial tendency of the airplane to continue away from the original state of equilibrium after being disturbed.

Question 9

Stable design

Answer 9

When designing the airplane, engineers must compromise between stability, maneuverability, and controllability; and the problem is compounded because of the airplane’s three-axis freedom.
●Lateral – Pitch
●Longitudinal – Roll
●Vertical – Yaw

Question 10

Dynamic stability

Answer 10

Overall tendency that the airplane displays after its equilibrium is disturbed.

Question 11

Long period phugoid oscillation

Answer 11

Over 10 seconds long.

Question 12

Short period oscillation

Answer 12

1-2 seconds.
A neutral or divergent, short-period oscillation is dangerous because structural failure usually results if the oscillation is not damped immediately.
Short-period oscillations affect airplane and control surfaces alike and reveal themselves as “porpoising” in the airplane, or as in “buzz” or “flutter” in the control surfaces.
Basically, the short-period oscillation is a change in angle of attack with no change in airspeed.
A short-period oscillation of a control surface is usually of such high frequency that the airplane does not have time to react.

Question 13

Dynamic vs static stability

Answer 13

A Dynamically Stable Airplane Is Also Statically Stable.
A Statically Stable Airplane May Not Be Dynamically Stable.

Question 14

Center of gravity

Answer 14

Theoretical Point At Which The Entire Weight Of The Airplane Is Assumed To Be Concentrated.
Airplane Rotates About CG In Three Planes of Freedom.