Performance/Weight and Balance

Question 1

What are some characteristics of a (relatively) heavy airplane?

Answer 1

• Higher takeoff speed
• Longer takeoff run
• Reduced rate and angle of climb
• Lower max altitude
• Shorter range
• Reduced cruising speed
• Reduced maneuverability
• Higher stall speed
• Higher approach and landing speed
• Longer landing roll
• Excessive weight on nose or tail wheel

Question 2

What is the CG shift formula?
a. What is the weight addition/removal formula?
b. What is the maneuvering speed formula?

Answer 2

Weight shifted / total weight = Change in CG / Distance weight is shifted
a. Weight added or removed / new total weight = Change of CG / Distance between location where weight is added / removed and old CG
b. Va @ max gross weight * square root (current weight / max gross weight)

Question 3

How much does the atmosphere’s weight change?

Answer 3

-1 inch of Mercury per 1000ft

Question 4

What does the current altimeter setting at a given airport represent?

Answer 4

It represents the station’s pressure corrected down to mean sea level. It is the altimeter setting that shows the airport’s true altitude.

Question 5

What is the density altitude formula?

Answer 5

120 ( OAT - standard temp ) + pressure altitude

Question 6

By what percent does your TAS increase every 1000ft?

Answer 6

TAS increases 2% of the IAS per 1000ft

Question 7

How does a forward CG affect the following characteristics?
- Takeoff
- Stall speed
- Cruise speed
- Fuel burn
- Stability
- Controllability
- Stall recovery
- Spin recovery
- Landing
- Vmc speed

Answer 7

• Takeoff - makes raising the nose more difficult
• Stall speed - higher - tail must produce more down force, thus increasing wing loading and causing the plane to fly @ higher AOAs to produce the same amount of lift to support the additional weight
• Cruise speed - lower - due to same reasons as higher stall speed, more drag is produced
• Fuel burn - increased - due to increased drag from above
• Stability - more longitudinally stable - as the CG moves forward, the plane becomes more nose heavy and tail heavy (more tail negative lift force), thus making them harder to be displaced.
• Controllability - less controllable - inverse relationship with stability. The more stable, the control forces needed to overcome that stability become become greater
• Stall recovery - easier - more nose heavy to decrease AOA
• Spin recovery - easier - more nose heavy to decrease AOA
• Landing - makes flaring more difficult, possibly causing a flat landing
• Vmc speed - lower - longer leverage arm between the CG and the rudder, translating to more authority with the rudder