Weight & Balance
Keeping the Shiny Side Up
Written for the Notre Dame Pilot Initiative
By the Pilots of the University of Notre Dame
“Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”
Roadmap
Terms
Forces
Mathematical Treatment
Graphical Treatment
Limitations
An airplane must only be flown
within certificated limits of weight
and balance to ensure that it remains
controllable, performs adequately
and is not overstressed. Correct
weight and balance means:
Maximum allowable weight is not
exceeded; and
Center of gravity (CG) is within a
specified range
Terms
Center of Gravity
 Point at which the airplane’s entire weight is
assumed to be concentrated
Center of Lift (Pressure)
 Point at which the airplane’s entire lift
assumed to be concentrated
Basic Empty Weight
 Generally, the weight of the airframe, unusable
fuel, unusable/full oil, and full hydraulic fluid
Forces
The goal in flying any airplane is to
always remain in positive control
Knowing how the forces that act on
our airplane balance helps us predict
how it will fly
AX = BY
Moment arm of A
Moment arm of B
X
Y
A
B
Fulcrum
Mathematical Treatment
“Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”
Practical Exercise
Joe (150) and Jeff (200) want to fly to
Cocoa Beach. They decide to take
Brady (231) with them for some extra
practice with them.
The golden helmets (15) are in the back
seat and footballs (35) are in the
baggage compartment.
Are we good to go?
Weight
We want to add up all of the weights in our
airplane
 Start with BEW
 Then we add usable fuel (and oil), passengers,
and cargo
FAA standard passenger is 170 lbs
 Always ascertain the proper weight of pax and
cargo
AVGAS is 6 pounds per gallon
Oil is 7.5 pounds per gallon
Water is 8.35 pounds per gallon
Weight
Empty Weight
1683
Useable Fuel
350
Front Seats
340
Rear Seats
15
Baggage Area
35
Takeoff Weight
2423
Balance
The aircraft can only be controlled if
it is positively stable.
Maintaining the proper center of gravity
assures us that the airplane will be
controllable upon liftoff
The Center of Gravity must be
forward of the Center of Lift
(Pressure) in order to achieve
positive dynamic stability
Loading Chart
Balance
Empty Weight
1,683
39.7
66,815
Useable Fuel
350
48.0
16,800
Front Seats
340
37.0
12,580
Rear Seats
15
73.0
1,095
Baggage Area
35
95
3,325
Takeoff Weight (lbs)
2,423
Total Moment (lb-in)
C.G (in)
100,615
41.53
“WAM” Weight x Arm = Moment
Total Moment / Total Weight = C.G
Graphical Treatment
“Teaching the Science, Inspiring the Art, Producing Aviation Candidates!”
63+12.5+12+2+3+1 = 93.5 lb-in
Center of Gravity Envelope
Stability & Control
 Center of Gravity concerns:
 Unable to compensate with
elevator in pitch axis
 Weight and Balance
becomes critical – stalls &
landing
Tricks of the Trade
Flying with a rear CG is more efficient but
decreases stability
Flying with a forward CG decreases
performance and makes flaring for landing
more difficult, yet makes for a quick stall
recovery
Flying over gross weight may overstress
the airplane and cause it to self-destruct
Conclusions
It is very easy to make an airplane
unflyable by misloading it.
When you fly outside of tolerance,
you become a test pilot.
Understanding weight and balance
will allow you to maximize
performance and understand poor
performance
Say Intentions
One Passenger, No baggage, Full Fuel, Calm
Winds, No Ceiling, PIC-25 hours
 Go for it
Three Passengers, Full Fuel, Golf Clubs for 4 (10
each), Scattered T-storms, PIC-500 hours
 Calculations bring you right to max GW and a rear CG
 Go for it with that experience
Second scenario again (Passengers are his
grandmother, girlfriend, and the bosses 3 year old
daughter), PIC-50 hours, 5 hours in an Archer
 No go, passengers are not easy to deal with, pilot has
little experience in type, and the airplane will be difficult
to control in turbulence
Salmon 30 Salmon