Final answer:
The principal advisor to a commanding officer on ground safety matters is likely the senior safety officer or a designated safety advisor, responsible for safety management and accident prevention.
Step-by-step explanation:
The principal advisor to the commanding officer on all ground safety matters could vary depending on the branch and specific structure of the military organization. However, within the context of the U.S. Armed Forces, this role might typically be fulfilled by the senior safety officer of the command or by a designated safety advisor. Their responsibility includes advising on safety management, accident prevention, and ensuring compliance with relevant safety regulations and procedures.