Performance and Limitations

Question 1

What are the effects of a forward CG?

Answer 1

Higher stall speed: aircraft has to fly at a higher AOA for level flight. Closer to Critical AOA.

Easier Stall Recovery: Nose naturally wants to fall forward.

Slower Cruise: Higher AOA means more life and more drag.

Less Range: Slower Cruise

Generally more stable: Higher AOA means more wing contribution to stability.

Question 2

What are the effects of an aft CG?

Answer 2

Slower Stall Speed: Lower AOA means further from critical AOA

Harder Stall Recovery: nose does not want to naturally fall forward.

Faster Cruise Speed: Lower AOA means less drag

More Range: Faster Cruise

Generally Less stable: Lower AOA means less wing contribution.

Question 3

What are the Load Factor Limits for the C-172? and where can you find them?

Answer 3

Normal:
Flaps Up positive 3.8g, negative 1.52g
Flaps down positive 3.0g

Utility:
Flaps Up positive 4.4g, negative 1.76g
Flaps down positive 3.0g

They can be found in POH section 2 Operating Limitations. 2-11

Question 4

What are the Load Limits in general? and where do you find them?

Answer 4

FAR 23.337

Normal Category: Positive is 3.8G, Negative is -1.52G

Utility Category: Positive is 4.4G, Negative is -1.76G.

Question 5

What are the effects of density altitude on performance?

Answer 5

Hot, Humid, High all decrease the density of the air.

Decreased power: Engine takes in less air
Decreased Thrust: propellers are less efficient in the thinner air
Decreased Lift: because airflow over the wings exert less force

increased ground roll, poor climb rate, longer take off and landing distances.

Question 6

Explain why Va changes with weight.

Answer 6

Draw it out and explain it as if you were teaching it to a student.