Abstract: A six-degree-of-freedom dynamics model of catapult launch of a carrier-based aircraft is established taking into consideration its off-center position. The launch bar load during the off-center catapult launch is calculated. The effect of initial off-center distance and take-off weight on the launch bar load is analyzed, and the kinetic cause of this phenomenon is also discussed in detail. From the catapult launch calculation, three important conclusions are obtained: the roll movement of the aircraft is the primarily source of the bending moment and the torsion which act on the launch bar; the bending moment and the torsion increase sharply with the increase of initial off-center distance, while the axle load is only slightly affected; in the prophase of catapult launch, the launch bar loads, including its axle load, bending moment and torsion, all increase with the decrease of the take-off weight, but in the anaphase of catapult launch, these loads decrease with the decrease of the take-off weight.

Key words: carrier-based aircraft, catapult launch, off-center distance, launch bar, loads