CH.3B Stability

Question 1

STABILITY

Answer 1

Characteristic that causes plane to return to condition of equilibrium

Question 2

POSITIVE STATIC STABILITY

Answer 2

The tendency to return to position from which it was displaced

Question 3

POSITIVE DYNAMIC STABILITY

Answer 3

coupled with positive static stability - does not happen at once, instead over a period of time and several oscillations

Question 4

MANEUVERABILITY

Answer 4

Permits you to maneuver it easily and allows manueves

Question 5

CONTROLLABILITY

Answer 5

response to control inputs, especially with regard to attitude and flight path

Question 6

THREE AXES OF FLIGHT

Answer 6

Longitudinal (roll)
Lateral (pitch)
Vertical (yaw)

Question 7

CENTER OF PRESSURE

Answer 7

Point on the wing chord where lift is considered to be concentrated AKA CENTER OF LIFT

Question 8

What determines the longitudinal stability of an airplane?

Answer 8

The location of center of gravity in relation to the center of pressure (lift)

Question 9

CG

Answer 9

Center of Gravity - The forward and aft limits coincide with the CG

Question 10

Effects of forward CG

Answer 10

May seem stable but will be nose heavy
longer take off distance
higher stalling speeds

Question 11

Effects of aft CG

Answer 11

Tail heavy and very unstable in pitch regardless of speed
Stabilator (elevator) may be ineffective for stall or spin recovery
THIS IS MORE dangerous that forward CG
Keep heavier passengers and baggage more far forward

Question 12

TAIL-DOWN FORCE

Answer 12

The position of the horizontal stabilizer to offset the nose-heavy tendency. It creates a negative angle of attack, negative lift on the tail (downward force), to counteract the hose heaviness.

Question 13

THRUSTLINE

Answer 13

Where the propeller is mounted and where thrust acts

Question 14

LATERAL STABILITY

Answer 14

Runs along the longitudinal axis (from nose to tail)
The tendency to resist roll:
Weight distribution
Dihedral
Sweepback (also help vertical axis/directional stability)
Keel effect (also help vertical axis/directional stability)

Question 15

DIHEDRAL

Answer 15

(Structural design)

The upward angle of the wing with respect to the horizon

Question 16

SWEEPBACK

Answer 16

(wing sweep) The characteristic of the wing that creates the angle backward from the wing root
Designed to maintain the center of lift aft of the CG and reduce wave drag at or above speed of sound
(light training airplanes - designed to improve lateral stability)

Question 17

KEEL EFFECT

Answer 17

The steadying influence exerted by the side area of the fuselage and vertical stabilizer

Question 18

DIRECTIONAL STABILITY

Answer 18

Stability about the vertical axis. The vertical fin contributes to the directional stability

Question 19

DUTCH ROLL

Answer 19

Combination of rolling/yawing oscillations caused by control input or wind gusts. (weak directional stability and strong lateral stability)

Question 20

THREE BASIC TYPES OF STALLS

Answer 20

Power-off stall
Power-on stall
Accelerated stall

Question 21

POWER-OFF STALL

Answer 21

AC configuration for normal landing approach stall

Question 22

POWER-ON STALL

Answer 22

These are encountered during takeoff, climb-out and go-arounds when pilot fails to maintain proper control due to premature flap retraction or excessive nose-high trim

Question 23

ACCELERATED STALL

Answer 23

Stalls at a higher speed

Question 24

CROSSED-CONTROL STALL

Answer 24

This happens when a pilot tries to compensate for overshooting a runways during a turn from base to final while on landing approach.

Question 25

STALL RECOGNITION

Answer 25

Mushy controls Less control effect with decreased speed (reduced control effectiveness is primarily due to reduced airflow) Loss of RPMs Buffeting, uncontrollable pitching or vibrations Kinesthetic sense (your ability to recognize changes in direction or speed) provides warning of decreased speed or sinking feeling

Question 26

SECONDARY STALL

Answer 26

Normally caused by poor stall recovery technique | ex. attempting flight prior to attaining sufficient flying speed

Question 27

What are the steps for proper STALL RECOVERY?

Answer 27

- Decrease angle of attack - Smoothly apply max allowed power to minimize latitude loss and increase speed - Adjust power as required, maintain coordinated flight while adjusting power to normal level

Question 28

SPIN

Answer 28

An aggravated stall which results in a helical (corkscrew) path

Question 29

What is the stability around the AC longitudinal axis?

Answer 29

This refers to as the lateral stability. Wing dihedrals, sweepback, keel effect, and weight distribution are design features that affect an airplane's lateral stability

Question 30

Where does the directional stability come from?

Answer 30

The vertical axis - maintained by the vertical tail

Question 31

When will a stall occur?

Answer 31

A stall will always occur when the critical angle of attack, or CLmax, is exceeded. This can occur at any airspeed an din an configuration or attitude

Question 32

In relation to the center of gravity, in which direction would the center of pressure normally move as angle of attack is increased on a cambered wing?

Answer 32

forward

Question 33

SPIN RECOVERY procedure

Answer 33

- Throttle to idle (eliminates thrust and minimizes loss of altitude) - Neutralize the ailerons - Determine direction of rotation (shown on turn coordinator) - Apply full opposite rudder (opposite of direction of spin) - Briskly apply elevator (stabilator) forward to aprox. neutral position. - As rotation stops, neutralize rudders (if not spin could go in opposite direction - Gradually apply aft elevator to return to level flight (too quickly can result in secondary stall, and possibly another spin. - adhere to AC airspeed and load limits during recovery and dive

Question 34

What factors can affect the longitudinal stability of an airplane at hight power settings and low airspeed?

Answer 34

An increase in thrust increases the pitching moment and nose heaviness due to the placement of the thrust line of the AC. This helps counteract the longitudinally destabilizing effect f increased downwash that results from an increase in power and extension of hight lift devices.

Question 35

Why are high wing AC normally designed with less dihedral than low wing AC

Answer 35

Upwash passing around the fuselage just ahead of the wing tends to roll a high wing AC toward the upright position, contributing to lateral stability. In a low wing airplane, the downwash around the fuselage tends to be laterally destabilizing since it tends to increase the roll. The amount of dihedral is adjusted to compensate for the effects of fuselage upwash and downwash resulting in a greater requirements for dihedral in low wing airplane than in a high wing configuration

Question 36

Does the propwash resulting from high power settings increase or decrease the contribution of wing dihedral to the lateral stability of an airplane

Answer 36

Decrease

Question 37

An aircraft with strong directional stability and weak lateral stability is often prone to what type of undesirable side effect

Answer 37

Spiral instability

Question 38

What should an AC do in terms of airspeed to land in gusty winds and help guard against a stall?

Answer 38

Increase airspeed above normal