Grand Admiral a naval rank in one of the highest in the several European navies that use this system, what system are they using?
Grand admiral Grand admiral is a historic naval rank, the highest rank in the several European navies that used it. It is best known for its use in Germany as "Großadmiral". A comparable rank in other navies is that of fleet admiral.
Lieutenant commander (Royal Navy) Lieutenant Commander (often abbreviated Lt Cdr) is a senior officer rank of the Royal Navy of the United Kingdom. It is immediately junior to commander and immediately senior to the naval rank of lieutenant.