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CHAPTER 3 - ENROUTE 3-1 Instrument Flight Rules (IFR). General: a. Prior to departure from within controlled airspace or prior to entering controlled airspace, a pilot must submit a complete flight plan and receive an air traffic clearance, if weather conditions are below VFR minimums. Instrument flight plans may be submitted to either the nearest military base operations, nearest FSS, or ATCT. Deliver either in person or by telephone (or by radio if no other means is available). Pilots should file IFR flight plans at least 30 minutes prior to estimated time of departure to preclude possible delay in receiving a departure clearance from ATC. To minimize your delay in entering Class B, Class C, Class D and Class E surface areas at destination when IFR weather conditions exist or are forecast at that airport, an IFR flight plan should be filed before departure. Otherwise, a 30 minute delay is not unusual in receiving an ATC clearance because of time spent in processing flight plan data. Traffic saturation frequently prevents control personnel from accepting flight plans by radio. In such cases, the pilot is advised to contact the nearest FSS to file a flight plan.
b. Instrument flight rules (IFR) flight. Destination weather must be forecast to be equal to or greater than the published weather planning minimum for the approach procedure to be flown at ETA through 1 hour after ETA. When there are intermittent weather conditions, predominant weather will apply. Aviators flying helicopters may reduce destination and alternate Category A visibility minimums by 50 percent, but not less than 1/4 mile or metric equivalent. Reduction of visibility for approaches labeled"copter only" is not authorized. Category II approach procedures may not be used in destination or alternate weather planning. 3-2 Lost Communications. a. Whether two-way communications failure constitutes an emergency depends on the circumstances, and in any event, it is a determination made by the pilot. FAR Part 91.3(b) authorizes a pilot to deviate from any rule in Subparts A and B to the extent required to meet an emergency. b. In the event of two-way radio communications failure, ATC service will be provided on the basis that the pilot is operating in accordance with FAR Part 91.185. 3-3 Terrain Clearance. a. OFF ROUTE OBSTRUCTION CLEARANCE ALTITUDE (OROCA) - CONUS OROCA is an off-route altitude which provides obstruction clearance with a 1,000 foot buffer in nonmountainous terrain areas and a 2,000 foot buffer in designated mountainous areas within the U.S. This altitude may not provide signal coverage from ground-based navigational aids, air traffic control radar, or communications coverage. b. OFF ROUTE TERRAIN CLEARANCE ALTITUDE (ORTCA) - OCONUS WHAT'S AN ORTCA?- An Off Route Terrain Clearance Altitude is published by the Defense Mapping Agency on Enroute Low Altitude Charts. Introduced on CONUS charts, in 1995, as Off Route Obstruction Clearance Altitudes (OROCA's), ORTCA's are designed to provide 3000' AGL terrain clearance and assist aircrews utilizing random navigation route structures in those areas where off route navigation is permitted. Return to Special Flight Information Bulletin |