Chapter 6 terms Weight & Balance

Question 1

Datum

Answer 1

The datum is an imaginary vertical plane from which all horizontal measurements are taken for balance purposes, with the aircraft in level flight attitude.

Question 2

Arm

Answer 2

The arm is the horizontal distance from the datum to any point within the aircraft. The arm’s distance is always measured in inches, and it is preceded by the algebraic sign for positive (+) or negative (􏰀), except for a location which might be exactly on the datum. The positive sign indicates an item is located aft of the datum, and the negative sign indicates an item is located forward of the datum

Question 3

Moment

Answer 3

Force that causes or tries to cause an object to rotate

The word moment is the product of a force or weight times a distance.

To calculate a moment, a force (or weight) and a distance must be known. The weight is multiplied by the distance from the datum and the result is the moment, which is expressed in inch-pounds (in-lb), a point through which the force acts

Question 4

Center of gravity (CG)

Answer 4

The CG is the point at which all the weight of the aircraft is concentrated and balanced; therefore, the aircraft can be supported at that point (the CG).

Question 5

Maximum Weight

Answer 5

The maximum weight is the maximum authorized weight of the aircraft and its contents, and is indicated in the Aircraft Specifications or TCDS

Question 6

Maximum Ramp Weight

Answer 6

The heaviest weight to which an aircraft can be loaded while it is sitting on the ground. This is sometimes referred to as the maximum taxi weight.

Question 7

Maximum Takeoff Weight

Answer 7

the heaviest weight an aircraft can be when it starts the takeoff roll. The difference between this weight and the maximum ramp weight would equal the weight of the fuel that would be consumed prior to takeoff.

Question 8

Maximum Landing Weight

Answer 8

The heaviest weight an aircraft can be when it lands. For large, wide body commercial airplanes, it can be 100,000 lb less than maximum takeoff weight, or even more.

Question 9

Maximum Zero Fuel Weight

Answer 9

The heaviest weight an aircraft can be loaded to without having any usable fuel in the fuel tanks. Any weight loaded above this value must be in the form of fuel.

Question 10

Empty Weight

Answer 10

The empty weight of an aircraft includes all operating equipment that has a fixed location and is actually installed in the aircraft

Question 11

Empty Weight Center of Gravity (EWCG)

Answer 11

The EWCG for an aircraft is the point at which it balances when it is in an empty weight condition.

Question 12

Useful Load

Answer 12

Anything not a part of the empty weight

subtract the empty weight from the maximum allowable gross weight.

Example: Crew member, luggage’s, fuel, passengers, pilot, copilot

Question 13

Minimum Fuel

Answer 13

Indicates that an aircraft’s fuel supply has reached a state where, upon reaching the destination, it can accept little or no delay.

Minimum fuel is the amount needed for 30 minutes of flight at cruise power.

Question 14

Tare Weight

Answer 14

The weight of the plane without any luggage, crew, or passengers. However, this weight would include any useful weight, such as fuel.

Examples: Wheel clocks, places on scales and ground locks left in place on retractable landing gear

Question 15

Weight and Balance Data

Answer 15

The weighing of the aircraft, the maintaining of the weight and balance records, and the proper loading of the aircraft.

Question 16

Scales

Answer 16

A device that uses load cells, designed to measure force or weight, to accurately determine the weight of an aircraft.

Top of jack load cells, as the name implies, can be used on top of the current wing jacks or can be used under axle for larger jets.

Question 17

Spirit Level

Answer 17

A leveling instrument placed on or against a specified place on the aircraft

Spirit levels consist of a vial full of liquid, except for a small air bubble.

Question 18

Plumb Bob

Answer 18

A heavy metal object, cylinder- or cone- shaped, with a sharp point at one end that is suspended by a string to produce a vertical reference line useful in aircraft measurements

Question 19

Oil System

Answer 19

The engine oil system performs several important functions: Lubrication of the engine’s moving parts. Cooling of the engine by reducing friction. Removing heat from the cylinders. Providing a seal between the cylinder walls and pistons

Question 20

Hydrometer

Answer 20

A device used for measuring the specific gravity of liquids

When an aircraft is weighed with full fuel in the tanks, the weight of the fuel must be accounted for by mathematically subtracting it from the scale readings. To subtract it, its weight, arm, and moment must be known.

Question 21

Miscellaneous Fluids

Answer 21

The hydraulic fluid reservoir and all other reservoirs containing fluids required for normal operation of the aircraft should be full. Fluids not considered to be part of the empty weight of the aircraft are potable (drinkable) water, lavatory precharge water, and water for injection into the engines.

Question 22

Flight Controls

Answer 22

The position of such items as spoilers, slats, flaps, and helicopter rotor systems is an important factor when weighing an aircraft. Always refer to the manufacturer’s instructions for the proper position of these items.

Question 23

Weighing Points

Answer 23

When an aircraft is being weighed, the arms must be known for the points where the weight of the aircraft is being transferred to the scales

Question 24

Jacking the aircraft

Answer 24

Jacking of aircraft is done in order to perform maintenance and inspection.

Question 25

Leveling the aircraft

Answer 25

When an aircraft is weighed, it must be in its level flight attitude so that all the components are at the correct distance from the datum. This attitude is determined by information in the TCDS. Some aircraft require a plumb line to be dropped from a specified location so that the point of the weight, the bob, hangs directly above an identifiable point.

Question 26

CG Range

Answer 26

The distance between the forward and aft CG limits indicated on pertinent aircraft specifications

Question 27

Empty Weight Center of Gravity (EWCG) Range

Question 28

Use of Ballast:

Answer 28

Ballast is used in an aircraft to attain the desired CG balance, when the CG is not within limits or is not at the location desired by the operator. It is usually located as far aft or as far forward as possible to bring the CG within limits, while using a minimum amount of weight.

Question 29

Temporary Ballast

Answer 29

Weights that can be carried in a cargo compartment of an aircraft to move the location of CG for a specific flight condition

Question 30

Permanent Ballast

Answer 30

A weight permanently installed in an aircraft to bring its center of gravity into allowable limits

Question 31

Helicopter Weighing

Answer 31

When a helicopter is being weighed, the location of both longitudinal and lateral weighing points must be known to determine its empty weight and EWCG. This is because helicopters have longitudinal and lateral CG limits

As with the airplane, the longitudinal arms are measured from the datum, with locations behind the datum being positive arms and locations in front of the datum being negative arms.

Question 32

TCDS (Type Certificate Data Sheet)

Answer 32

Where the Datums location can be identified

Aircraft with TCDS has a separate Equipment list

Question 33

The Aircraft Specifications

Answer 33

Another way where the Datums location can be Identified

The Aircraft Equipment list is included in this one

Question 34

MAC (Mean Aerodynamic Chord)

Answer 34

the average chord length of a tapered, swept wing.