Weight And Balance Flashcards
Effects of adverse balance
Stability
Control
Negligible weight / CG change
1lbs or less for <5000lbs
2lbs or less for 5000-50000lbs
5lbs or less for 50000lbs+
CG change less than 0.05%.of mean aerodynamic chord (MAC) = average distance from leading edge to trailing edge
Moment arm
Horizontal distance in inches from reference datum line to the CG
Basic empty weight
GAMA
Standard plus equipment
CG
Point aircraft would balance if suspended, mass center
In inches from datum line or percent of MAC
CG limits
Forward and aft points within CG must be located
CG range
Datum
Imaginary vertical plane or line from which all measurements of arm are taken
Established by manufacturer
Floor load limit
Max weight per sqr in/foot
Fuel load
Expendable part of the fuel
Ramp or taxi weight vs take off weight
Difference due to fuel burn during taxi
Max zero fuel weight - GAMA
Exclusive usable fuel
Moment
Weight of an item x arm
In pound-inches
Moment index
Divided by constant such as 100, 1000
Simplify weight and balance computation
Payload - GAMA
Weight of occupants, cargo, baggage
Standard empty weight - GAMA
Airframe, engines, fixed equipment, ballast, hydraulic fluid, unusable fuel, engine oil
Standard weights
Use if actual weights are not available
Station
Location in aircraft, distance in inches from datum
Useful load
Pilot, co-pilot, passengers, baggage, usable fuel, drainable oil
Determine load weight and CG
Computational method
List weight of aircraft, occupants, fuel (6lbs/gal), baggage
Weight x arm = Moment
Total weight and total moment
Total moment / total weight = CG
Loaded weight and CG
Graph method
Graphs calculate moment
Find weight and draw line straight across until it intercepts with item, straight line down to read moment
Other load weight and CG calculations
Table
With negative arm
With zero fuel,weight
Calculate weight shift and CG
100lbs shifted from station 30 to 150
Moment increases total by 12000in-lbs
Moment at 150 = 100lb x 150in = 15000in-lb
Moment at 30 = 100lb x 30in = 12000in-lb
Moment change 15000-3000= 12000
Total moments = 616000 + 12000 = 628000
CG = 628000in-lb/8000lb (total weight) = 78.5in
Calculate shift of CG
Weight shifted / total weight = ^CG / distance of weight shift
100 / 8000 = ^CG / 120
^CG = 1.5in
Previous CG + ^CG = new CG
Add/Subtract ^CG
Shifting aft, add
Shifting forward, subtract