A flight test study to determine whether adding ballast to shift an aircraft center of gravity location aft improves aircraft level flight performance parameters

One of the most fundamental concepts of flight mechanics is that, all other parameters being equal, a light aircraft will perform better than a heavier one. Another characteristic of flight is that, all other parameters being equal, an aircraft with an aft center of gravity, or cg, within the aircraft's cg envelope, will generally outperform an aircraft with a more forward cg location. Some pilots have tried to apply these two theories by adding additional weight to an aircraft in order to move the cg location aft to improve the performance of the aircraft. The purpose of this thesis was to determine whether the advantages of moving the aircraft center of gravity location aft would outweigh the disadvantages of the additional weight added to the aircraft required to accomplish this.

This thesis was based on flight tests taken in a Piper Saratoga, PA-32-301, which is fully instrumented for taking required flight test data. Five flight tests were conducted at varying weight and cg locations using the Speed-Power method. The data was reduced and results obtained using the PIW-VIW method. The results of the flight test conducted with this particular aircraft reveal that, for the configurations tested, adding ballast to move the cg location does not improve the aircraft performance. Performance comparisons were based primarily on the parasitic drag coefficient and Oswald's efficiency factor.