Datum

• An imaginary vertical line from which all measurements of arm are taken
• Established by the manufacturer
• Commonly located on the Firewall of the aircraft

Arm

• The horizontal distance in inches from the reference datum line to the CG of an item

Station

• A location in the aircraft that is identified by a number designating its distance from the datum
• We use this for CG calculations as ARM
• Established by the POH

Moment

• The product of the weight of an item multiplied by its arm

$Moment = (Weight)x(Distance from Datum)$

Center of Gravity CG

• The point about which an aircraft would balance if it were possible to suspend it at that point

CG Limits

• The specific forward and aft points within which the CG must be located during flight
• Established by the POH

Standard Empty Weight (GAMA)

• Aircraft weight that consists of the airframe, engines, full operating fluids, full engine oil and all items of operating equipment that are permanently installed

Basic Empty Weight (GAMA)

• The standard empty weight plus the weight of optional and special equipment that has been installed

Maximum Zero Fuel Weight

• Is the maximum weight allowed before usable fuel and other specified usable agents

Maximum Takeoff Weight

• The maximum allowable weight for takeoff

Maximum Weight

• The maximum authorized weight of the aircraft and all of its equipment

Maximum Gross Weight

Maximum Ramp Weight

• The maximum weight an aircraft can weight on the ramp prior to takeoff
• May be higher than max takeoff weigh because the fuel that is burned in taxi and runup

Maximum Landing Weight

• Maximum weight that an aircraft is normally allowed to have a landing

Payload

• The weight of occupants, cargo and baggage

Usable Fuel

• The amount of fuel available for flight planning purposes
• Established by the POH

Useful Load

• The weight of the pilot, copilot, passengers, baggage, usable fuel and drainable oil

Fuel Load

• Includes only usable fuel

Reduces the flight Performance of the aircraft

1. Higher takeoff speed
2. Longer takeoff run
3. Reduced climb rate
4. Lower max altitude
5. Shorter max range
6. Slower cruise speed
7. Reduce maneuverability
8. Higher stall speed
9. Higher landing Speed
10. Longer landing roll

Load Factor

1. Va (Maneuvering Speed)
2. Structural Integrity

Forward CG Effects

• Longer Takeoff Roll
• Longer Landing Roll
• Higher Stall Speed
• Easier Stall Recovery
• Decreased Cruising Speed

Aft CG Effects

• Lower Stall Speed
• Reduced Elevator Authority
• Difficult Stall Recovery

Normal Category

An aircraft must fall into this category to safe perform normal flight maneuvers, such as Takeoffs, Landings, Steep Turns, Slow Flights, Stalls...

Utility Category

An aircraft must fall into this category to safe perform special flight maneuvers such as spins or other maneuvers specified in that aircraft’s POH