Ground School 3.06 Weight & Balance

3.06 Importance of Weight Almost every aspect of performance is influenced by the weight of the aircraft and its contents. An overweight airplane will has : longer takeoff run higher takeoff speed lower angle and rate of climb lower cruising speed shorter range higher stalling speed longer landing roll

3.06 Importance of Weight Loading an airplane too heavy can dangerously decrease its performance, and increase the risk of structural damage. Airplane manufacturers do extensive testing to establish safe limits for airplane loading. Most common limits are maximum takeoff and landing weights.

3.06 Importance of Balance Center of gravity (CG) : the imaginary point where the aircraft would balance if suspended CG is critical to an airplane’s stability and elevator effectiveness. CG limits are the forward and aft center of gravity locations within which the aircraft must be operated at a given weight.

3.06 Weight And Balance Terms Empty Airplane Center of Gravity CG Limits Reference datum Arm and Moment

3.06 Weight And Balance Terms Reference datum : the location from which all horizontal distances are measured for weight and balance purposes Arm : distance from the datum, measurements aft of the datum are generally positive numbers, while those forward of the datum are generally negative numbers ( Fuselage station ; F.S. is another term for the arm) Moment : a weight multiplied by an arm

3.06 Aircraft Weight and Balance 10 lbs 5 lbs 1 in. 2 in. WEIGHT X ARM = MOMENT

3.06 Weight And Balance Terms Empty Airplane Center of Gravity CG Limits Reference datum Arm and Moment Basic empty weight Licensed empty weight Unusable fuel

3.06 Weight And Balance Terms Empty Airplane Basic empty weight : weight of airplane + equipment + unusable fuel + full engine oil Licensed empty weight : weight of airplane + equipment + unusable fuel + full engine oil + undrainable oil Unusable fuel : small amount of fuel in tanks that cannot be used in flight or drained on ground

3.06 Weight And Balance Terms Loaded Airplane Ramp Weight Takeoff Weight Landing Weight Total Weight Payload Useful Load

3.06 Weight And Balance Terms Loaded Airplane Ramp Weight : airplane loaded for flight prior to engine start Takeoff Weight : Ramp Weight – fuel burned during start & runup & taxi Landing Weight : Takeoff Weight – fuel burned enroute

3.06 Weight And Balance Terms Loaded Airplane Total Weight : (Gross Wight) weight of airplane and everything carried in it Payload : weight of only passengers, baggage and cargo Useful Load : Payload + weight of flight crew and useable fuel

3.06 Methods For Calculating Total Weight And CG Table Graph Computation

3.06 Calculating the position of the CG - + 5 in. Ref Line 10 lbs 10 lbs 5 in. 15 in. W X A = M 10 lbs. X - 5 in = - 50 in lbs. 10 lbs. X + 15 in = +150 in lbs. 20 lbs. (W) +100 in lbs. Average Arm = +100/20 + 5 in

3.06 Calculating the position of the CG - + 10 in. Reference Line 10 lbs 10 lbs 20 in. 30 in. W X A = M 10 lbs. X 10 in = +100 in lbs. 10 lbs. X 30 in = +300 in lbs. 20 lbs. (W) +400 in lbs. Average Arm = +400/20 + 20 in

3.06 Calculating the position of the CG on an airplane Reference Datum - + 23 in. 10 in. 50 10 100 9 in. 10.18 in. 100 lbs. X 9 in = 900 in lbs 50 lbs. X 10 in = 500 in lbs. 10 lbs. X 23 in = 230 in lbs. 160 lbs. (W) 1630 in lbs. Average Arm = 1630/160 10.18 in

3.06 Calculating the position of the CG on an airplane Empty Airplane: Arm: 70 inches Weight: 1,150 pounds Pilot: Arm: 73 inches Weight: 135 pounds Weight Arm Moment Empty Airplane 1,150 pounds X 70 inches = 80,850 pounds - inches Pilot 135 pounds X 73 inches = 9,855 pounds - inches Total 1,285 pounds 90,355 pounds - inches Total Moment Total Weight = CG Arm 90,355 pounds - inches 1285 pounds = 70.3 inches

3.06 Methods For Calculating Total Weight and CG Computation Graph Table

3.06 Methods For Calculating Total Weight and CG Computation Table Graph

Add all the amounts to obtain ramp moment. 3.06 Methods For Calculating Total Weight And CG Fuel Pilot and Passenger Baggage Rear Passenger(s) Add all the amounts to obtain ramp moment.

3.06 Center Of Gravity Moment Envelope Ramp Weight Ramp Moment Now what?

Divide total moment by total weight to get CG. 3.06 CG Limits Divide total moment by total weight to get CG. Ramp Weight Ramp CG

3.06 Weight Shift Formula Can be used to calculate the amount of weight that must be moved a specific distance or to determine the distance a specific weight would need to move to bring the CG within approved limits

Weight Moved Distance CG Move Weight of A/C Distance Between Arms 3.06 Weight Shift Formula 2600 2500 2400 2300 2200 2100 2000 1900 1800 1700 1600 GROSS WEIGHT MOMENT LIMITS MOMENT / 100 - in. lbs F33C ACROBATIC CATEGORY LIMITS F33A & F33C UTILITY CATEGORY 2700 2800 2900 82.1 86.7 3500 3400 3300 3200 3100 3000 WEIGHT - POUNDS 162 Pounds Weight Moved Weight of Airplane Distance CG Moved Distance Between CG Arms = 162 pounds 2,500 Pounds X 36 inches 162 x 36 2,500 X = X = 2.3 inches Weight Moved Distance CG Move Weight of A/C Distance Between Arms

3.06 Effects of increasing weights Takeoff Distance Landing Distance Climbouts True Airspeed Longer distance required Longer distance required Angle reduced Performance reduced Reduced

3.06 Effects Of Moving CG Aft Rotation Flare Stability True Airspeed Too quick Too quick Less stable Faster

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