飞行课程 Stage 3 - Weight and Balance

Content:

1. The Importance of Weight and Balance

2. Weight and Balance Terminology

3. Calculating Total Weight and Center of Gravity

4. Methods for determining Total Weight and Center of Gravity

5. Using the Weight-Shift Formula

1. The Importance of Weight and Balance

• Risks Associated with Operation of Overweight Aircraft

• Take off

• Climb

• Cruise - structural damage

• Landing

• Effects of an Improperly Balanced Aircraft

• CG: critical to aircraft staility as well as elevator or stabiator effectiveness

• CG too far forward (Nose-heavy):

• Reduced elevator or stabilator effectiveness

• Poblems in controlling the pitc attitude 

• CG too far aft (Tail-heavy):

• Incapability to recover from stalls and spins

• Light control forces

• Determine the CG before each flight and ensure that it is within the manufacturer's limits

• Center of Gravity Limits

• Any movement of passengers or cargo changes the location of the CG
  

2. Weight and Balance Terminology

• Definition of Reference Datum:

• Reference datum is an imaginary vertical plane from which all horizontal distances are measured for balance purposes

• CG limits are usually expressed in inches from the reference datum

• The location of the reference datum is specified in the POH or in the airplane's weight and balance documents

• Terms Describing the Empty Aircraft

• "Basic empty weight" - the weight of the standard airplane, optional equipment, unusable fuel, and full operating fluids including full engine oil

• Unusable fuel - the small amount of fuel that connat be trained

• Licensed empty weight - the same as basic empty weight but does not include full engine oil

• Termsn Describing the Loaded Aircraft

• Ramp weight - the weight of the airplane loaded for flight prior to engine start

• Takeoff weight - the ramp weight minus the fuel burned during engine start, runup, and taxi

• Landing weight - the takeoff weight minues the fuel burned enroute

• Useful load - the weight of the flight crew, usable fuel, passengers, baggage, and cargo

• Usable fuel - the portion of the total fuel on board the airplane that is available for flight and ground operations

3. Calculating Total Weight and Center of Gravity

• Calculate Total Weight

1. List the empty weight of the aircraft in column one

2. Compute the weight of oil and record it on the worksheet

3. List the remaining items that you intend to load and record the actual weight of each item in column two

4. Convert fuel to pounds

5. Add all weights to determin the total aircraft weight

6. Verify that the total aircraft weight does not exceed the maximum takeoff weight

• Terms Associated with the Center of Gravity

• Reference Datum - an imaginary vertical plane from which all horizontal distances are measured for balanced purposes

• Arm - the distance, measured in inches, from the reference datum to any area used for weight distrubution

• Aft of the reference datum, the arm is a positive value

• Forward of the reference datum, the arm is a negative value

• Moment - a measurement of the tendency of a weight to cause rotation at the fulcrum

• Relationship Between Movement and Balance

• Moment = Weight x Arm

• Calculate the Center of Gravity

• Add the weights of the two children and the seesaw

• Multiply each weight bu its respective arm to calculate the movement

• Add the moments

• Divide the total moment by the total weight to determine the location of the center of gravity

4. Methods for determining Total Weight and Center of Gravity

• Computatioinal Method
  

• Graph Method

• Table Method

5. Using the Weight-Shift Formula

• Use the weight-shift formula to calculate:

• The amount of weight that must be moved a specific distance to bring the CG within limits

• The distance that a specific weight must be moved to bring the CG within limits

• The weight-shift formula uses four variables:

• Weight Moved

• Weight of Aircraft (loaded)

• Distance that the CG Moves

• Distance Between Arms