Thursday, June 7, 2012

RNP and SAAAR, VFR?

One of the great innovations in navigation is the concept of RNP, or Required Navigation Performance. With enough redundancy, computing power, training, and, of course, money, IFR airplanes are threading their way through narrow valleys, the unseen mountains to either side almost close enough to touch.

So, if your Gulfstream, Global Express, or plain Jane Boeing 737 is properly equipped, and if you and your other crew member have the proper training, you can get into Juneau with decent IFR minimums, rather than waiting until the weather is VFR, and good VFR at that, which is what they did in the bad-old-days. This privilege comes at the price of SAAAR, or Special Aircraft and Aircrew Authorization Required.

That sounds expensive.

These days the vast majority of my flying is in an Archer with no de-icing or radar. In my former life, flying Cessna 414s and King Airs on "Lifeguard" missions, I used to fly at night into mountain strips like Afton, Wyoming, or Salmon, Idaho. The unseen mountains were close enough to touch, but I had been trained to turn base over Pete's dad's house in a corner of the valley, and I had weather radar running in mapping mode, giving me some idea where the rocks were or were not. I don't do this in the Archer.  The Archer is worth less money than SAAAR equipment.

But lately I've found myself studying the SAAAR approaches into some of my destinations, even when VFR. Especially when VFR. Let me explain, with an example.

There's a Father's Day fly-in, spot landing contest, and general good time planned for Smiley Creek, ID (KU87) on, of course, Father's Day, and I was thinking about flying in, hitting the spot, and generally having a good time. Smiley Creek is one of the easier high-altitude strips in Idaho; it's at 7160MSL, but the valley around it is wide open, at least enough to allow a normal pattern. You just have to keep an eye out for density altitude.

The grass is well trimmed and the campground has hot showers. The free campground has hot showers!  If you prefer, there's an inn across the road, but I've enjoyed camping there. I've never found much fishing, but there is lots of interesting hiking (it's the only place I've ever seen a bear in the wild).

Smiley Creek isn't hard to find, but my philosophy is that more flight planning is always better, so I wanted to look at a GPS route that I could actually fly.  Looking at the sectional, though, there are no charted fixes that follow the valleys, which is where I prefer to be.  This isn't uncommon; just look at Afton, or Ennis, MT, or any the dozens of airports in the Rockies.

Smiley Creek has no approaches, but nearby Hailey (KSUN), which serves the Gulfstream crowd, has an RNP approach to runway 31.  A flash of intuition struck, and took a look at the fancy-pants approach to KSUN.

So here is the RNAV (RNP) Y RWY 31 approach into KSUN.  I've highlighted some of the interesting bits: first, it's a SAAAR approach; DME-DME and inertial navigation are not supported; and the missed approach requirement is pretty tight.  The missed approach takes you over the valleys to the northwest, toward Smiley Creek.  With a little fooling around, I decided CUTLA was the fix closest to my desired route; the resulting route is the magenta line on the sectional above.

The charted route is 11NM longer than the direct route, but it is, in fact, almost exactly the route I will fly.  I really want to fly with minimum (comfortable) fuel because of the density altitue situation, and 22 NM (including the departure) is about 2 gallons, or 12 pounds. If I were rash enough to plan for minimum fuel, I would be smart to include those 2 gallons in my planning. This amount of weight probably won't change the outcome of the flight.  Probably!  For flights that go deeper into the mountains, there might be much more than 22 miles of "diversion," making the fuel calculation more complex.

And what if something goes really wrong?  Wrong, like smoke from a wildfire making the route hard to see, or, worse, a windscreen covered in hot oil?  Having a preplanned escape plan can't possibly hurt.

I did this recently planning to go to a fly-in at Hill AFB (KHIF), where the desired reporting point was the tip of Antelope Island in the Great Salt Lake.  This is very close to the missed approach fix for one of the TACAN approaches into Hill (it's also charted as a VFR reporting point on the Salt Lake City Terminal Area Chart).  In this case the goal was more to pick a direct route to the rendezvous, but the same principle holds.  (Alas, the fly-in was cancelled due to weather.)

So, no, while I am not equipped for a TACAN approach, and, no, I don't have SAAAR authorization, I can still use the fixes to make my VFR flying easier and more efficient.

An alternative is to pick out lat/long coordinates and use these in your flight planning.  The main problem with this is that, despite years of practice, every now and then I misread them, usually by a whole or half degree.  I usually check them before I launch, but an in-flight reroute can make the coordinates hard to read as well as hard to type into your GPS flight plan.

Another alternative is to use your GPS moving map's capability (if you have one).  Select a point on the map and add it to your flight plan; this is pretty easy on my Garmin AERA, but other units can involve a lot more work.  With the AERA, when I fly to Idaho Falls to teach at our other campus, I put a waypoint at the entry point for the downwind to the runway I expect to use, and go straight there.  But that's a short flight over flat terrain.

The conclusion is that, going back to Bowditch, a wise navigator uses every available resource.  Even without the equipment to fly those approaches, you can use the data to make your flying safer and more efficient.

Try it!




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