This damage often is caused by improper maintenance practices such as jacking adjacent to a jack pad or an inadvertent impact with tools or ground-support equipment (e.g., tow vehicles).

• 这类损伤大多是由于维护不当诸如在顶升垫以外的位置顶升飞机或使用工具或地面设备（拖车）撞击飞机造成的。