My teaching schedule has been a bit hectic lately, hence little time to blog. With two days off in a row, I've found a spare moment to regroup and talk about a topic that recently came up - RNAV direct, off-airway routings when flying under IFR.
A manager I had years ago in the software world introduced me to the concept of the New Jersey Left. Some folks also know this as a Boston Left, too. The concept is basically this: You are on a crowded, two-lane city street, waiting at a red light. The on-coming traffic is being led by one car that needs to make a left turn. There is no room for the cars behind the left-turner to pass on the right. The light turns green and the left-turner, paying attention and gifted with fast reflexes, turns left in front of you and, this is the important part, you let them do so out of consideration to the folks behind the left turner who otherwise would have to wait until the next green light. You are delayed a second or so and that allows several other people to get on with their busy lives. Ah, cooperation! It's a sweet thing when it happens.
The FAA recently announced that pilots who want to be assigned RNAV standard departure procedures (SIDs) or RNAV Standard Terminal Arrivals (STARs) need to file an ICAO flight plan. You see, the current FAA Form 7233-1 flight plan uses a single-letter equipment suffix to describe the type of navigational equipment onboard the aircraft. This overly simplistic simplistic system worked fine back in the 1960's when most aircraft either had a couple of VOR receivers and maybe an Automatic Direction Finder. It still worked in the 70's when distance measuring equipment (DME) became popular as pilots began to realize that being able to immediately discern their distance from a VOR station without doing mental math or using a second VOR was a pretty good thing. The simple equipment suffix continued to work into the 1980's as flight management systems (FMS) became more prevalent. And it still worked in the 1990's as IFR GPS receivers with moving maps became commonplace, even as many old school pilots where complaining "Pshaw, that's just cheating."
In the last few years, the combination of FMS and various flavors of WAAS and non-WAAS GPS has resulted in numerous levels of navigation performance and the matrix became too complicated to develop a kludge for the equipment suffix. Enter the Form 7233-4 ICAO-style flight plan for certain RNAV flights - you can read more here and here.
Now virtually every other country has been using ICAO flight plans for quite some time, which allows the pilot using said form to describe in fairly complete detail just what sorts of knobs, dials, and screens they have on board. In the FAA's defense, they tried to switch everyone to the ICAO flight plan format several years ago. AOPA lobbied strongly against the proposal, saying it was too complicated to get every U.S. pilot to switch. I remember reading that argument and thinking at the time that my BS meter was reading firmly in the yellow, if not in the red.
The good news for many of you out there is that most GA aircraft still won't need to file an ICAO flight plan unless they are equipped to fly (and want to fly) RNAV SIDs or STARs. ATC's computerized system for assigning clearances has been programmed based on well-established operational reasoning and that isn't going to change anytime soon, near as I can tell.
I recently tried experimenting with an ICAO IFR flight plan to see if using it would result in a more direct routing to a nearby airport. After much research on how to get the flight plan filled out correctly, I filed an ICAO flight plane using DUAT. And when my student called clearance delivery, we got exactly the same clearance we always get. And the additional detail supplied in the ICAO flight plan didn't seem to make any difference to the approach controller once we were airborne. Given a vector to join an airway, we had to specifically request to proceed direct to a fix on the airway, thereby reminding (or perhaps informing) the controller that we had en route RNAV capabilities.
Most pilots who fly RNAV-equipped aircraft regularly will learn to request direct-to shortcuts, and you can too. Here are some basic scenarios for requesting direct-to navigation, but remember that the controller may say "unable direct" for a variety of reasons. It still doesn't hurt to ask.
If a controller tells you "fly heading 120, vectors Red Bluff" and you notice that the 120 heading is virtually direct Red Bluff, you can respond with "heading 120 and we can proceed direct Red Bluff now if that's okay." In these situations, I've found controllers are usually quite happy to give you direct-to the fix.
When you are being vectored to join an airway and you want a shortcut that you believe will not pose a traffic problem or a obstacle clearance problem, request direct-to the fix to which you want to proceed. A little caution is in order here. If you specify a fix that is outside the controller's sector, they may say "unable" simply because they don't know where that fix is located. You can sometimes help the controller out by specifying what the on-course heading would be to your desired fix.
If the shortcut you want will take you through busy airspace at an inconvenient altitude when the controller is busy, the answer will most certainly be "unable" and you may as well not ask. My experience has shown me that flying at a higher altitude and in a faster aircraft is more conducive to getting a shortcut than flying at a lower altitude in a slower aircraft.
If you fly the same route frequently, asking for a shortcut will help you learn the controller's constraints. Some controllers will take the time to explain when a shortcut will work and when it won't. Other controllers will just bark at you, so be prepared. But by asking for direct, you remind the controller that you are RNAV capable.
And the next time you read about how NexGen will allow aircraft of the future to route themselves, how VORs are going to be phased out, and how everyone will be able to fly direct to their destination, you can take that with the appropriate amount of sodium chloride. Until then, you can ask for your own shortcuts from ATC and, with a little knowledge and cooperation, you might just get to your destination a bit faster and burn less fuel in the process.