Stability

Question 1

What is static stability?

Answer 1

The immediate reaction of the body after disturbance.

Returns to original position = Positive static stability

Remains in new position = Neutral static stability

Continues to move off in new direction = Negative static stability

Question 2

What is dynamic stability?

Answer 2

The subsequent reaction after a body has been disturbed.

Question 3

Name some factors that affect the long-term response of an aircraft.

Answer 3

Linear velocity and mass (momentum)

Static stabilities in roll, pitch and yaw

Angular velocities about the three axis

Angular momentum

Aerodynamic damping moments due to roll, pitch and yaw

Question 4

What design features enhance Directional stability?

Answer 4

Large Fin

Long Moment Arm

Question 5

What design features enhance Longitudinal stability?

Answer 5

Large Horizontal Tailplane

Long Moment Arm

Question 6

What design features enhance Lateral stability?

Answer 6

Large Fin

Dihedral

Sweep Back

High Wing

Question 7

Go and look at graph of dynamic stabilities in notes or course manual.

Answer 7

LEARN

Question 8

At what indicated airspeed, for a certain AUW (All-Up-Weight) is maximum range achieved?

Answer 8

Vimd - IAS for minimum drag

Actually want to fly at 1.32Vimd for max range!! LARGE increase in distance covered for SMALL increase in drag.

Question 9

What is range flying concerned with regarding fuel?

Answer 9

SFC - Specific Fuel Consumption

Air nautical miles per kg of fuel

I.e. fuel efficiency with respect to thrust output

Question 10

What is endurance flying concerned with regarding fuel?

Answer 10

GFC - Gross fuel consumption (i.e. weight of fuel consumed per hour)

Proportional to power output

Question 11

At what speed is the maximum endurance obtained?

Answer 11

The level flight speed that corresponds to the minimum POWER output of the engine.

Note - WIND HAS NO EFFECT ON ENDURANCE

Question 12

What must be considered when aiming to fly for max range?

Answer 12

Clean aircraft, fuel load, AUW

Temperature - Colder = more thrust + better engine thermal efficiency

High altitude - Less drag

1.32Vimd

Higher TAS at higher altitudes as air is less dense. Increases the range.

Tailwind will increase range.

Lowest possible SFC - Run at high “design RPMs”, achieved at high altitudes and reduces SFC. Colder temp also reduces SFC. High altitude decreases SFC.

Question 13

How is maximum endurance achieved in a turboprop aircraft?

Answer 13

Fly at medium altitude where the engines are throttled to produce an IAS of about Vimd.

Question 14

How is max range achieved in a turboprop?

Answer 14

In cruise climb - Max continuous RPM and an IAS slightly above Vimd.