READ

GLEIM CHAPTER 5 (5.7-5.9)

17 QUESTIONS JEP CHAPTER 8 SECTION B (8-

29 TO 8-47) PHAK CHAPTER 9 ASA Chapter 8-1 through 8-20

Private Pilot Ground School Weight & Balance Class #5

Content of Lesson

Terms used in weight and balance calculations.

Effects of weight and the distribution of weight

Various Manufacturers display of weight and balance info and use of

B-19 weight and balance computations sample and actual problems

Weight and Balance Terminology

Reference Datum- imaginary vertical plane from which all horizontal distances are measured for balance purposes

Different Datum Locations

Weight and Balance Terminology

Standard Empty Weight - the weight of a standard airplane including unusable fuel, full operating fluids and full oil.

Basic empty weight - Standard empty weight plus optional equipment

Weight and Balance Terminology

Max ramp weight - max weight of aircraft for taxi operations (it includes start taxi and run-up fuel)

Max takeoff weight - max weight approved for the start of the takeoff run

Max landing weight - max weight approved for the landing touchdown

Weight and Balance Terminology

Useful load - Difference between take off weight and basic empty weight

Payload - Weight of the occupants, cargo and baggage

Zero fuel weight - weight exclusive of usable fuel useful for calculations when fuel is a variable

Weight and Balance Terminology

Tare - Weight of chocks, blocks, stands ect used when weighing an aircraft

Arm - the horizontal distance from the reference datum

Moment - the force exerted by a weight using an arm usually measured in in/lbs or foot/lbs

Station- a designated location on the fuselage measured from the reference datum

Weight and Balance Terminology

Center of Gravity - The point at which an airplane would balance if suspended from that point

C. G. Arm (center of gravity)- The arm obtained by adding the airplane’s individual moments and dividing the sum by the total weight

Weight and Balance Terminology

C. G. Limits - The extreme center of gravity location within which the airplane must be operated at a given weight.

Useable Fuel - Fuel available for flight planning

Weight and Balance Terminology

Unusable Fuel - Fuel remaining after a runout test.

Falcrum - Support point

Principles of Weight and Balance

Weight x Arm = Moment Arm = Moment/Weight Weight=Moment/Arm

WAM

A balanced teeter-totter

- ARMS

Determining Gross Weight & Center of Gravity

Three ways Computation method, Tabular method, and Graphical method

Computation method (p135)

Tabular method (p136)

Like B-19, uses tables to quickly determine arm and moment.

Graphical method (p136)

Also used for B-19 to determine gross weight moment limits (6-12)

Loading graphs commonly found in cessna POH’s

Easy way to determine if aircraft is in the envelope.

Graphical method (p136)

High gross weights

High gross weights

Added wear on engine Increased fuel consumption Overheating in climb

High gross weights It is a violation of FARs to exceed

gross weight limits

LLF

Limit load factors normal 3.8 -1.52 utility 4.4 -1.76 aerobatic 6.0 -3.0

High gross weights

Over loading may accelerate metallic fatigue failures

Baggage floor may have limits on weight for structural reasons

Stability may be effected to the negative if overloaded

High gross weights

The higher the gross weight the higher the stall speed

Less reserve angle of attack Load distribution

Safety

Manufacturer set limits for controllability and maneuverability

Certification procedures demand a certain amount of oscillations before dampening out this determines where the aft cg is located

Forward CG gives:

Higher stall speed, Higher elevator control forces (critical

in takeoff and landing phase), Slower cruise, (higher angle of attack

need more tail down force.) More overall stability, Longer takeoff and landing distance,

Aft C of G

With an aft cg recovery from a stall spin harder or impossible.

Lower stall speed Less elevator control forces in T.O. landing Faster cruise, (Lower angle of attack need

less tail down force.) Less overall stability, Less takeoff and

landing distance

Lateral Balance

Lateral unbalance usually a result of unbalanced fuel load will cause additional lift and drag on heavy side

STANDARD WEIGHTS

Weights

Oil weighs 7.5 lbs. per gallon. Since oil is usually measured in quarts, each quart weights 1 7/8 pounds.

The average weight for passengers is approx. 170 lbs.

Aviation fuel (Avgas)weighs 6 lbs. Per gallon

2 gallons of fuel = 12 lbs.

Problem #1.

Determine the CG of these three objects

Weight A=100 lbs Arm 50 Weight B=100 lbs Arm 90 Weight C=200 lbs Arm 150 What is the CG =110

Problem #2

Basic Empty Weight = 1340 Arm=37 Front seats=140 lbs Pilot and 115 pound

passenger, Moment=8,925 Rear seat =212 lbs passenger and 97 pound

passenger. Arm 72 Useable Fuel=40 Gallons, Arm 48 Baggage 50 lbs. Moment 4,600 To stay in envelope CG limits=+35.6 to +43.2.

What is the CG? Is the aircraft in the envelope?

Problem #2 Answer

CG=44.1 No the aircraft is not in the envelope. Can we fly the aircraft? No, not legal One possible solution would be to trade

places between the 212 pound rear-seat occupant and the 115 pound occupant. Using a weight shift equation we can see how far the CG will move.

Weight Shift Equation

By manipulating the formula we find that CG=(Weight shifted X Distance it is shifted)/Total Weight

Weight Shift Equation

Weight to be shifted is equal to what?

(212lbs-115lbs) Distance it is shifted is equal to

what? (72 inches-35inches)

Weight Shift Equation

Total Weight = What? 2,194 (212-115)X(72-35)/2,194= 97X37/2,194= 1.6 inches This makes the new CG 42.5 within

limits

B-19 PROBLEM

BB2 PILOT 190 LBS ARM 109 FRONT PASSENGER 180 LBS ARM 108 BACK SEAT 15 LBS FUEL 40 GALLONS FLIGHT 1.5 HOURS GPH 7.8 START RUNUP TAXI 1 GALLON