[Code of Federal Regulations] [Title 14, Volume 3] [Revised as of January 1, 2006] From the U.S. Government Printing Office via GPO Access [CITE: 14CFR171.251] [Page 240] TITLE 14--AERONAUTICS AND SPACE CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PART 171_NON-FEDERAL NAVIGATION FACILITIES--Table of Contents Subpart I_Interim Standard Microwave Landing System (ISMLS) Sec. 171.251 Scope. Source: Docket No. 14120, 40 FR 36110, Aug. 19, 1975, unless otherwise noted. This subpart sets forth minimum requirements for the approval and operation of non-Federal Interim Standard Microwave Landing System (ISMLS) facilities that are to be involved in the approval of instrument flight rules and air traffic control procedures related to those facilities.