Lesson 14 Weight And Balance Importance Of Weight

Lesson 14: Weight And Balance

Importance Of Weight And Balance • Forward CG • Increases tail down force which increases effective weight (real weight + tail down force) • All parameters of aircraft performance will decrease except maximum power off glide distance.

Importance Of Weight And Balance • Forward CG • Take off and landing distance and stall speed will increase, cruising speed and rate of climb will decrease. • Control pressures for pitch changes will be greater. • Pitch trim nose up • Most dangerous part of flight with forward CG is landing (ground effect).

Importance Of Weight And Balance • Aft CG • Decreases the need for tail down force so effective weight is less. • Control changes for pitch changes will be light. • Pitch stability will be poor. • Stall speed decreases.

Importance Of Weight And Balance • Aft CG • All performance parameters improve, except maximum power off glide distance. • Most dangerous part of flight with aft CG occurs in slow flight (stall/spin may lead to flat spin).

Importance Of Weight And Balance • Who has the final responsibility for accurate, up-to-date aircraft empty weight and Balance?

Importance Of Weight And Balance • Who has the final responsibility for accurate, up-to-date aircraft empty weight and Balance? Pilot

Importance Of Weight And Balance • Any time equipment is added or removed, or any repair or alteration is made, this change must be recorded in the weight and balance information. • Weight and balance information used by the pilot must be kept up to date. • Done by maintenance technician. • Referenced by the pilot for weight and balance calculations.

Terminology • Arm – The horizontal distance of any object from the datum. Expressed in inches and may be – or +. • Center of Gravity - The point at which the nose and tail moments are of equal magnitude (CG). • Datum – An imaginary vertical line from which all horizontal measurements are made or indicated.

Terminology • Moment – A rotational force caused by a weight acting on an arm. The product of the weight multiplied by the arm. Weight X Arm = Moment WXA=M

Determining the CG

Determining the CG • Moment Index • Loading graph is used to determine the moment index • Advantage: No multiplication. • Disadvantage: Shows only the loaded CG. Figure 16 -14 Loading graph Figure 16 -15

Terminology • Ballast – Weight used to obtain a favorable center of gravity location. It is often made of lead. It may be movable or permanent and must be marked as such. TOTAL WEIGHT X DISTANCE NEEDED TO SHIFT BP ARM OF BALLAST – ARM OF NEW BP Figure 16 -25 (Temporary Ballast) Figure 16 -26 (Shifting Weight)

Weight And Balance Changes • An A&P maintenance technician will have to find the new empty weight and empty weight center of gravity after an alteration to the aircraft has been performed.