Appendix B - Acronyms and Abbreviations

U W UAS—unmanned aircraft systems W—west UFN—until further notice WAAS—Wide Area Augmentation System UHF—ultra high frequency WAN—wide area network UNAVBL—unavailable WB—westbound UNLGTD—unlighted WC—work center UNMKD—unmarked WCP—Weather Communications Processor UNMNT—unmonitored WECO—Western Electric Company UNREL—unreliable WED—Wednesday UNUSBL—unusable WEF—with effect from; effective from URA—Uniform Relocation Assistance and Real Property WESCOM—Western Electric Satellite Communications Acquisition Policies Act of 1970 WI—within USAF—United States Air Force WIE—with immediate effect, or effective immediately USC—United States Code WKDAYS—Monday through Friday USOC—Uniform Service Order Code WKEND—Saturday and Sunday WMSC—Weather Message Switching Center V WMSCR—Weather Message Switching Center Replacement WND—wind V/PD—Vehicle/pedestrian deviation WPT—waypoint VALE—voluntary airport low emission WSCMO—Weather Service Contract Meteorological VASI—visual approach slope indicator Observatory VDME—VOR with distance measuring equipment WSFO—Weather Service Forecast Office VDP—visual descent point WSMO—Weather Service Meteorological Observatory VF—voice frequency WSO—Weather Service Office VFR—visual flight rules WSR—wet snow on runway(s) VGSI—visual glide slope indicator WTHR—weather VHF—very high frequency WTR—water on runway(s) VIA—by way of WX—weather VICE—instead/versus VIS—visibility VLF—very low frequency VMC—visual meteorological conditions VNAV—visual navigational aids VNTSC—Volpe National Transportation System Center VOL—volume VON—virtual on-net VOR—VHF omnidirectional range VOR/DME—VHF omnidirectional range/distance measuring equipment VORTAC—VOR and TACAN (collocated) VOT—VOR Test Facility VP/D—vehicle/pedestrian deviation VRS—voice recording system VSCS—voice switching and control system VTA—vertex time of arrival VTAC—VOR and TACAN (collocated) VTOL—vertical takeoff and landing VTS—voice telecommunications system B-12