Chapter 6 - The Effect of Mass and its Distribution

Question 1

What is the centre of gravity?

Answer 1

The point at which an objects mass can be thought of as acting through.

Question 2

An aircrafts CG is forward of the centre of pressure. Is this aircraft stable?

Answer 2

Yes, it would create a pitch down moment.

Question 3

An aircrafts CG is aft of the centre of pressure. Is this aircraft stable?

Answer 3

No, it would create a pitch up moment.

Question 4

What characteristics does a stable aircraft have?

Answer 4

Increased trim, induced drag and fuel consumption
Increased pitch down tendency, especially for flap use
Increased elevator load required to raise nose
Increased longitudinal stability
Increased stress for nose gear
Decreased rate and gradient of climb.
Increased stall speed

Question 5

What characteristics does an unstable aircraft have?

Answer 5

Elevator control force reduced, possible overstressing of aircraft
Increased workload for the pilot
More difficult spin recovery
Reduced drag, so endurance and range increased
Tendency for aircraft to pitch up.
Reduced stall speed.
Poor landing characteristics

Question 6

Why is there a corner cut off of the CG envelope for an aircraft?

Answer 6

Once a specific weight in reached elevators wont have enough authority and so to stop this from happening the section of corresponding mass and CG is omitted