<p>With the rapid advancement of unmanned aerial vehicle (UAV) technology, aerial photography using UAVs has been widely used in various fields. Meanwhile, the high resolution and wide availability of UAV aerial images raise serious privacy risks. At present, scholars have proposed some schemes based on image encryption to protect the privacy of images. However, these schemes sacrifice the inherent visual usability of images. Motivated by this, this paper proposes a UAV aerial image encryption scheme that ensures privacy protection while preserving certain visual usability. This makes it possible to preview the structural information in the encrypted image. In this scheme, the one-time pad is employed to generate distinct derived keys, enabling the creation of different derived keys each time when processing images. Subsequently, the chaotic system is utilized to produce pseudo-random number sequences for replacing and rearranging the image pixels, thereby achieving an effect similar to Mosaic. It achieves a balance between privacy and visual usability by adjusting the block size. Experimental results show that the proposed scheme has good security, and effectively balances privacy protection and visual usability of images.</p>