The document discusses weight and balance concepts for aircraft. It covers structural weight limitations, performance effects of being overweight, and the importance of center of gravity position for stability and controllability. Calculating an aircraft's center of gravity involves determining the basic empty weight, empty moment, and empty center of gravity, then accounting for changes in weight and moment from passengers, baggage, and fuel. The center of gravity position must remain within specified limits for safe flight.

1. Weight and Balance

2. Weight and Balance
We will mainly talk about:
● Weight
● Center of gravity

4. Weight - Structural Limitation
Weight of aircraft limited structurally by:
● Maximum structural resistance of the wings
● Maximum lift the wings are able to generate
● Maximum force the landing gear is able to
absorb

5. Weight - Structural Limitation
The maximum weight figures can be found in
the “Limitations” chapter of the POH:

6. Weight - Structural Limitation
● The amount of lift produced is limited by:
● airfoil design
● angle of attack (AOA)
● airspeed, and air density.
● We must ensure that lift generated is sufficient to
counteract weight.

7. Weight - Structural Limitation
An overweight condition puts the airplane at
risk!

8. High-drag field
(wet or grass runway)
Runway lengthHigh-density altitude
Weight - Performance Limitation

9. Effects of Overweight
● Structural limits may be exceeded
● Stall speed increase
● T/O, Landing distances increase
● Rate of climb reduction
● Range and endurance reduce
● Excessive wear on brakes and tyres

10. Center of Gravity (CG)
Point at which all weight is said to act.

11. Center Of Gravity Position
Primary importance to aircraft stability and
controllability
A CG beyond limit puts the aeroplane at risk!

12. Center Of Gravity Position
On most aeroplanes, CG must be forward of the
CP
Makes the aircraft “nose heavy”
Requires a downward
force on the horizontal
stabilizer

13. Center Of Gravity Position
This gives the aeroplane static longitudinal
stability.

14. Center Of Gravity Position
Effects of CG too far aft:
● Aircraft aerodynamically unstable
● Nose may lift before rotation speed
● Excessive nose down trim is required

15. Center Of Gravity Position
Effects of CG too far forward:
● Tail load needs to be increased
● Lack of sufficient elevator authority
● Increased stalling speed
● Increased nose down trim
required

16. Weight And Balance
Calculations

17. Weight and moment
10lbs 10lbs
Exemple 1
Will this plank remain in equilibrium over the fulcrum?
Yes!
CG is at fulcrum

18. Weight and moment
10lbs 10lbs
Exemple 2
Will that plank remain in equilibrium over the fulcrum?

19. Weight and moment
Answer: No!
CG no longer at fulcrum position

20. Weight and moment
Equal amount of mass but MOMENT is different.
Moment = Mass · Distance
Unit of Moment = pound-inches

21. Weight and moment
10lbs 10lbs
5in 2in
10 × 5 = 50lbs-in 10 × 2 = 20lbs-in

22. Calculating the CG Position of the plank
Our mission:
Find the CG position to make the plank hold in equilibrium
What do we need to find?
● The CG

23. Calculating the CG Position of the plank
10lbs 10lbs
10 · 14 = 140lbs·in
Datum
2in
14in
CG = Total Moment
Total
Weight
10 · 2 = 20lbs·in

24. CG= 160lbs·in = 8
20lbs
Calculating the CG Position of the plank
10lbs 10lbs
10 · 2 = 20lbs·in 10 · 14 = 140lbs·in
Datum
2in
14in
8in

25. The CG is equidistant from both weights.
Calculating the CG Position of the plank
10lbs 10lbs
10 · 2 = 20lbs·in 10 · 14 = 140lbs·in
Datum
2in
14in
8in

26. Calculating the CG Position of the plank
10lbs 10lbs
10 · 2 = 20lbs·in 10 · 14 = 140lbs·in
Datum
2in
14in
6in 6in
Does that make sense?
Yes, because that means the CG is equidistant from
both weights.

27. Weight and moment

28. Weight and moment
300lbs180lbs30lbs

29. Weight and moment
We need to know how much weight we put in
our aircraft to determine our CG:
● Passengers
● Baggage
● Fuel

30. Weight and moment
Before calculating the influence of our
passengers and cargo, we need to know:
● Basic Empty Weight of airplane (BEW)
● Empty CG

31. Weighing of aircraft
Some conditions for weighing:
● Clean Aircraft
● Inside hangar
● Fuel drained
● ...

32. Weighing of aircraft
By taking the weight of each wheel we are able
to know the total weight and the empty CG.
Nose wheel reads: 450lbs
Right wheel reads: 480lbs
Left wheel reads: 480lbs
Total: 1410lbs

33. Weighing of aircraft
Moment:
N.W.: 450lbs × 31= 13950lbs in
R.W.: 480lbs × 109.7= 52656lbs in
L.W.: 480lbs × 1.097= 52656lbs in
Total moment= 119262lbs in
Total weight=
1410lbs119262 84.6

34. Weighing of aircraft
Total weight = 1410
lbs
Total moment = 119262
lbs in
BECG =
84.6
We now have the three elements required for our Weight &
Balance calculations:

35. Weighing of aircraft
Basic Empty Weight (BEW) = 1410
lbs
Basic Empty Moment = 119262
lbs in
Basic Empty CG =
84.6 in
We now have the three elements required for our Weight &
Balance calculations:

36. These figures must be
onboard whenever you
fly.
Usually a paper at the
end of the POH.

37. 1460.3 126078
390 31395
160 18896
300 28500
20 2856
2330.3 207725.0
2323.3 207060.0
86.3
89.1
89.1
Fuel:
1 USg AVGAS
weighs 6 lbs.
50 US gallons.
50×6=300

38. 1460.3 126078
390 31395
160 18896
300 28500
20 2856
2330.3 207725.0
86.3
89.1
2323.3 207060.089.1
Takeoff weight and CG
are within the envelope.

39. 2598 231481.889.1
! Takeoff weight and CG
outside the envelope !

40. 2410 20605585.5
! Takeoff weight and CG
outside the envelope !

41. 2410 20605585.5
! Takeoff weight and CG
outside the envelope !
You will need to
● rearrange the load
● offload something or somebody
● reduce the fuel load if possible

42. End

43. Calculating the CG Position of the plank
10lbs 10lbs
10 · 14 = 140lbs·in
Datum
2in
14in
CG = Total Moment
Total Weight
10 · 2 = 20lbs·in

44. Calculating the CG Position of the plank
Our mission:
Find the CG position to make the plank hold in equilibrium
What do we need to find?
● A datum
● The moments of our objects