1. LECTURE 4 BALANCE, STABILITY AND CENTRE OF GRAVITY
MASS AND BALANCE
LECTURE 4
BALANCE, STABILITY AND CENTRE OF GRAVITY

2. INTRODUCTION : RELATIONSHIP
STABILITY
BALANCE
WEIGHT
CENTRE OF GRAVITY

3. INTRODUCTION
As weight change, it affect the aircraft stability and balance.
Stability is the condition of being stable.
Balance refer to the location of centre of gravity (CG).
If we can’t guarantee the aircraft stability and balance, we’ll have trouble to operate the aircraft.

4. THEORY OF LEVER
To balance the lever, the weight must be distributed so that the turning effect is the same on one side of the fulcrum.

5. Important for Aircraft Stability
Ensure Flight safety
Balance
4H 1W CREATION
What is CG?
How important CG is?
Where is CG location?
When aircraft CG move away?
Who can control CG?
Refer to CG

6. WHAT IS CG?
The center of gravity is a point at which an airplane would balance if it were suspended at that point.

7. How to Balance Aircraft?

8. CG Location Longitudinal (From A/c side view) Lateral
(From A/c front view)
Figure:
Aircraft Axis

9. CG Location
The prime concern of airplane balancing is the fore and aft location of the CG along the longitudinal axis.
Where is Fore?
Where is aft?
Draw on note!

10. CG Location
Location of the CG with reference to the lateral axis is also important.
Center of gravity

11. CG Location Shifted
Lateral balance is relatively easy to control and longitudinal balance is more critical.
The center of gravity is not necessarily a fixed point.
Location depends on the distribution of weight.
As variable load items are shifted or expended, there is a resultant shift in CG location.

12. INDIVIDUAL TASK : CLASS
EXAMPLE
As we move, CG also move.
Still remember what is CG?
How can you relate with
aircraft situation?
INDIVIDUAL TASK : CLASS
IN 5 MINUTES, I WANT EACH OF YOU TO GIVE EXAMPLE OF CG WHICH CAN BE RELATED WITH AIRCRAFT SITIUATION / CONDITION.

13. What are the variables that can affect weight and CG?
Luggage
Instrument
Fuel
Passenger
& Crew
Affect Lateral CG
Affect Longitudinal CG

14. CG Importance As the results, CG location shifted (move).
Thus, thus the A/C have will pitch up.
Can cause the A/C stall.

15. CG Importance This cause the A/c lose lateral balance.
One side of the wing is much more heavy.
This cause difficulties for pilot to control.
This unbalance create aircraft instability

16. Continue. . .
The pilot should realize that if the CG of an airplane is displaced too far forward on the longitudinal axis, a nose-heavy condition will result.
Conversely, if the CG is displaced too far aft on the longitudinal axis, a tail-heavy condition will result.
It is possible that an unfavorable location of the CG could produce such an unstable condition that the pilot could not control the airplane.

17. Forward Center of Gravity
Nose become Heavy
– Problems controlling and raising the nose
– Inability to flare for landing
Acts as more weight
– More stable ( base on basic principle. The more the weight, the more stable an object)
– Decreased Performance
Higher stall speeds

18. Aft Center of Gravity Tail become Heavy
– Light control forces
– Easy to over-control and overstress
Reduced capability to recover from stalls and spins
– Can not lower nose
– Flat spin: nearly impossible to recover
Decreased stability
– Difficult to right itself after maneuvering/turbulence

19. WHO CAN CONTROL CG? GROUND TECHNICIAN PILOT Calculate Luggage loading
Ensure Luggage weight
Calculate Luggage
loading
Monitor fuel weight
Ensure Luggage weight
Communicate with Pilot

20. Terminology & Definition

21. Terminology & Definition
Datum
Imaginary vertical plane or line from which all measurements of arm are taken. Established by manufacturer. Everything (moment arms, CG range) measured from this point.
Arm
The distance from the datum to any component part of the airplane, or any object loaded on the airplane. (+) denotes aft of datum, (-) denotes forward of datum

22. Terminology & Definition
Station
Location in the airplane identified by a number designating its distance in inches from the datum.
Moment
Product of the weight of an item multiplied by its arm.
Moment = Weight (Load) x Arm Distance

24. Exercise 1 : Calculate Moments

25. Exercise 2 : Calculate Moments

26. Exercise 3 : Calculate moments
After receiving your Private Pilot Certificate, you decide to
take your family on sight-seeing flight around Grand Forks.
If your mom weighs 150 lbs and sits it the co-pilot seat, your
dad is 200 lbs, your sister is 115lbs and you weigh 130 lbs:
How much fuel can you bring? Calculate moments.
Given:
MZFW = 800lbs
MTOW = 775lbs
MLW = 1090 lbs