New RNAV procedures for instrument pilots

January 9, 2005

New RNAV procedures for instrument pilots
/G? Get ready for RNAV STARs, SIDs, and T routes!

Beginning September 1, the FAA is implementing new RNAV procedures in both terminal and high-altitude airspace. If you're an IFR pilot and you file as a "/G," you should be prepared to fly RNAV instrument departure procedures (SIDs on Jeppesen charts, DPs in NACO publications) and standard terminal arrival routes (STARs). And you now have access to new RNAV "T" routes to ease your way through some Class B airspace and "Q" routes to shorten the distance if you're flying above 18,000 feet.

But don't worry; if you have an IFR-approved panel-mount GPS, you probably have the equipment you need. Now we'll tell most everything you need to know.

"The FAA is turning more and more to satellite navigation, which is something that AOPA has encouraged for a long time," said Randy Kenagy, AOPA director of advanced technology. "RNAV means more direct routes, more efficient use of airspace, and time and money savings for pilots."

Some IFR pilots have called the AOPA Pilot Information Center (800/USA-AOPA) with questions about a recent Jeppesen notice on "Type A & B equipment notes on U.S. RNAV SID and STAR procedures," and specifically what an "RNP-capable" aircraft is.

So let's sort it out.

First off, to use any of the new RNAV procedures, you must have a TSO C-129 or C-146 certified GPS (panel mount, IFR certified for en route and approach operations) or certain kinds of FMS (flight management system) equipment, and a current database. Your IFR or VFR loran, handheld GPS, or KNS-80 "VOR relocator" are not RNAV-capable.

If you do have an IFR GPS unit, you also have an RNP-capable aircraft.

RNP — required navigation performance — is a measure of navigation accuracy. From the pilot's viewpoint, the difference in RNP levels is essentially CDI (course deviation indicator) sensitivity. Type A SIDs and STARs, for example, require RNP 2.0 capability, the same sensitivity used for en route navigation, or 4 nautical miles from full deflection left to full deflection right on the CDI.

Type B are not only RNP 2, but also RNP 1.0, or 1 nm full deflection. That's the same sensitivity your GPS automatically scales to once you're in the terminal area (if the arrival airport is entered in the GPS flight plan).

Which brings up an important point — your GPS will scale automatically to the terminal (1 nm) sensitivity provided you've loaded your departure airport (for SIDs) or arrival airport (for STARs) into the flight plan.

Also, to fly an RNAV SID or STAR, you must load the complete procedure, by name from the database, into the flight plan. You can't load the waypoints manually. And for a SID, make sure you have selected the correct departure runway. The procedures and waypoints are different for each runway.

And now you also have to worry about RAIM for departure, en route, and arrival RNAV procedures, as well as GPS approaches.

RAIM? Receiver autonomous integrity monitoring, and it's essentially a check to see if the receiver will be able to double-check — or validate — its position calculations.

It used to be you had to do a RAIM prediction just for your intended approach. Now you're required to "predict" that you'll have RAIM for every leg of the flight that you plan to fly using an RNAV procedure. So you should ask for GPS notams, and enter the PRN number(s) that are out of service into your GPS. The box will use that data to predict RAIM availability for each airport that you enter. To check your entire route, you may need to enter several different airports and check RAIM. (You may need to spend some time with your GPS manual if this is foreign to you. And we should note, not every GPS model has this capability.)

Flight service stations should also be able to give you a RAIM prediction for arrival and departure procedures at any public-use airport.

The FAA is also developing a RAIM prediction Web site, but it will be a while before it's available. So the agency is giving you a pass, of sorts. Until the Web site is up, you don't have to perform a RAIM prediction for RNAV departure or arrival procedures that have a "radar required" note on the chart, or for RNAV en route segments where ATC has radar coverage.

Of course, if you have the latest IFR GPS navigation system, a Wide Area Augmentation System (WAAS) receiver, no RAIM checks are needed. Just make sure no WAAS notams are published, and you're good to go.

All of this is explained in much greater detail in Advisory Circular 90-100 and Chapter 5 of the Aeronautical Information Manual.

Updated: September 2, 2005, 10:13 a.m. EDT