Directional axis flying qualities assessment of low aspect-ratio combat flying wings

The directional axis flying qualities of low aspect-ratio combat flying wings were assessed in accordance with MIL-STD-1797A, and the evaluation results indicate the following aspects. The stability and damping of the low aspect-ratio flying wing is found to be poor due to the unusual configuration, and the closed-loop dynamic response characteristics such as Dutch-roll mode and sideslip magnitude depend much more on the flight control system. However, owing to the special aerodynamic configuration, the static trimming characteristics cannot entirely meet the criterion for flying qualities. Most low aspect-ratio flying wings have several redundant control surfaces, and the control allocation leads to the need to modify of some existing criterions. In some cases, the control power requirements of flying wings are quite different from those of the conventional-configuration fighters, which is a result of the disappearance of the vertical tail and rudders and the appearance of innovative control effectors (ICE). In sum, those new flying quality characteristics must be concerned in the design of flying wings' configuration and flight system design and the enaction and implement of flying quality criterions.