VOR-DME RNAV)
The suffix R after the aircraft type in an IFR flight plan indicates that, in addition to an altitude-encoding transponder, the aircraft is equipped with an FAA-approved RNAV system. Beyond that, your flight plan for an RNAV trip is no different from one using VOR airways except for the language used to describe the route of flight. Let the specialist know that it’s an RNAV flight plan and then go ahead with the waypoints you intend to use; for example, “direct LMN 270026, DSM 270022, FOD 090030, direct MCW.” In addition to waypoints selected for your con- venience, include one for each turning point (if any) on your route.
Make certain your route of flight includes at least one waypoint in each Center area you will pass through and that such waypoints are located no more than 200 miles from the border of the previous Center’s bailiwick. You should also be aware that one of the pre- requisites for ATC’s acceptance of a straight-line RNAV route is the ca- pability of radar following throughout the flight; this may be the reason an RNAV-direct request is sometimes turned down.
The final waypoint of a typical RNAV trip is right on the airport, but it doesn’t meet the standard of good practice, which calls for the final item in “Route of Flight” to be the radio fix from which you intend to commence an instrument approach in the event of com- munications loss. If the destination airport has a published RNAV ap- proach procedure, it would be proper to list the appropriate Initial Approach Fix as the last item. This could be an IAF shown on the RNAV approach chart or a non-RNAV fix on a conventional chart.
RNAV Includes LORAN
and GPS
The simplicity of planning, filing, and flying IFR with RNAV rises to new heights for pilots with long-range navigation equipment. The
Chapter Ten
two most prominent these days are Loran (LOng RAnge Navigation) and GPS (Global Positioning System). If we can believe what we hear from the government, GPS will eventually replace Loran and the ex- isting VOR system, but don’t hold your breath; the next time a new navigation system doesn’t come on line when it’s scheduled won’t be the first time.
Loran, which now covers almost all of the continental United States, works its magic by interpreting the time difference in low- frequency radio signals from chains of master and slave stations. A typical Loran display shows present position, course to be flown, course deviation, groundspeed, ETE, etc. More accurate than VOR- DME RNAV but not as precise as GPS, perhaps the best thing about Loran is the fact that the signals can be received almost anywhere, including on the ground and behind mountains where VOR signals are blocked.
GPS operates on signals transmitted from a number of orbiting satellites and provides virtual worldwide coverage with accuracy unprecedented in aerial navigation. The cockpit display is generally similar to that provided by Loran.
Remarkably different as they are in terms of operating principles, Loran and GPS both provide course guidance from one point to an- other along a “great circle” route, which is the shortest distance between two points on a sphere. Imagine a world globe with an equator that can be moved about until it rests on your point A and point B; that portion of the equator between A and B is a “great circle” route.
So in accordance with good navigational practice, you should draw a course line on the chart to help keep track of your position in relation to alternate airports, restricted areas, terrain, obstructions, and so forth as you go on your way. But as far as ATC is concerned, only Point A (departure) and Point B (destination) are important, and the computers in the Air Route Traffic Control Centers are pro- grammed to recognize and accept great circle tracks. You should specify turning points on your route and include a checkpoint within 200 miles of each Center’s boundary. If the destination airport’s library of charts includes STARs, or if you are aware of a specific approach fix in use, file to the appropriate point instead of to the air- port itself.
Obviously, there are times when other traffic, hot restricted areas or MOAs, or local flow management procedures prevent a controller from accommodating your request to fly direct, but it’s worth a try. If your “RNAV direct” request is turned down before takeoff, try again when you’re in the air. Each time you are handed off to a new con- 132
troller, politely request “RNAV direct.” It’s not at all uncommon for the traffic situation to be completely different as you get closer to desti- nation, and such a request is often granted. Why not try to wring every bit of utility and economy out of that expensive navigation equipment?
As with any off-airways journey, you are responsible for selecting and accepting an IFR altitude that guarantees proper obstacle clear- ance throughout the flight. With a Sectional, a WAC chart, or an RNAV planning chart, check terrain and obstacles along the way and be cer- tain that your flight altitude clears everything within 4 miles either side of course by at least 1000 feet in the flatlands and 2000 feet in those areas designated “mountainous.”