This paper highlights the water tunnel experiments of both the Boeing
X-45A stealth drone model and the traditional NASA TP-1803 model
without semblance of stealth, and compares their wing vortex structures and aerocharacteristics for several parameters. The experiments show that the normal force coefficient of the X-45A increases much more than that of the TP-1803 for α<20° in the static processes, and the X-45A has better
longitudinal stability than the TP-1803. For α>20°, the Cn of the TP-1803 is larger than that of the X-45A. Further, the longitudinal instability of the X-45A occurs earlier than TP-1803. Further, For α<20° the Cn of X-45A increases rapidly in the pitch-up process, but decreases slowly for the pitch-down process. The dynamic normal fore experiment shows more
tremendous hysteresis for the TP-1803 than the X-45A. In addition, the
maximum Cm in the X-45A is larger than the TP-1803. Besides, the
X-45A’s nose pitch-up moment appears reductive for α=30° in the
pitch-down process. Yet, larger K result in larger hysteresis loops and the longitudinal instabilities appear clearer. Ultimately, the longitudinal direction presents stable state from α<25° in the pitch-down processes.