飞行课程 Stage 3 - Weight and Balance

Content:

The Importance of Weight and Balance

Weight and Balance Terminology

(资料图片仅供参考)

Calculating Total Weight and Center of Gravity

Methods for determining Total Weight and Center of Gravity

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

List the empty weight of the aircraft in column one

Compute the weight of oil and record it on the worksheet

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

Convert fuel to pounds

Add all weights to determin the total aircraft weight

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

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