An aircraft lien is subordinate only to the rights of the holder of any of the following instruments relating to the aircraft, executed and recorded with the Federal Aviation Administration before the time the lien becomes effective: Bill of sale; Contract of conditional sale; Conveyance; or Mortgage or assignment of mortgage. A motor vehicle lien is subordinate only to a security interest perfected as required by law, except in the case of a motor vehicle sold under § 16-207 of this subtitle. In this subsection, “preferred ship mortgage” means a preferred mortgage as defined in 46 U.S.C. § 31322 on a vessel of the United States that is filed in accordance with 46 U.S.C. §§ 31321 through 31330. A boat lien is subordinate to a preferred ship mortgage that is filed with the Secretary of Transportation before the boat is sold under § 16-207 of this subtitle. Except in the case of a boat sold under § 16-207 of this subtitle, a boat lien is subordinate to a security interest perfected as required by law. A mobile home lien is subordinate only to a security interest perfected as required by law, except in the case of a mobile home sold under § 16-207 of this subtitle.