My apologies for the long break from blogging. This was due mostly to my getting sick and then having a spate of unplanned maintenance activities on my Jetta TDI. We're both now in fine fettle, thank you, though I'm a bit poorer than I'd like. These recent events have led me to offer some unsolicited testimonials:
Bauer's European Auto Repair in Berkeley - they actually understand diesel engines, they're friendly, and their prices are reasonable, and they don't treat you as if you're in league with the devil if you are using biodiesel.
Zicam Cold Remedy Rapid Melts - a homeopathic cold remedy recommended to me. I was skeptical until I tried it. While it doesn't make your cold go away, it turns the volume down on the symptoms and helps you get on with your life.
Mucinex - a time-release, tablet version of guaifenesin (a common active ingredient in cough syrups). It's better than cough syrup by a long shot.
Now on to the promised discussion of RNAV departure procedures. RNAV departures in the U.S. are designed primarily to simplify the delivery of IFR clearances in busy airspace, to provide obstacle clearance in remote areas where VOR reception is spotty due to terrain, or both. They come in a couple of flavors: Type A and Type B. Both types usually start with a heading or vector from the end of the departure runway to an RNAV fix. The differences between type A and B SIDs are largely incidental to the pilot flying with a 430W or 530W, but here they are for completeness:
First RNAV fix from the end of the departure runway:
Type A: approximately 10NM
Type B: "near" the departure end
RNAV accuracy required during 95% of the flight time:
Type A: +/-2NM
Type B: +/-1NM
Type A: no later than 2000 feet Height Above Airport
Type B: no later than 200 feet HAA
Equipment required (described in AC 90-100)
Type A - GPS, DME/DME, or DME/DME/IRU RNAV
Type B - GPS or DME/DME/IRU RNAV
There's really not a lot to flying a RNAV SID, as long as you do some preflight planning. The first task is to ensure that you can meet any required climb gradient specified on the chart. Consider the CHOIR ONE departure from Alturas, California.
And I shouldn't have to say this, but:
Don't use any of the charts, snippets, or other illustrations shown in this blog for navigation in a real aircraft.
This SID requires a minimum climb of 367 feet per nautical mile or 389 feet per nautical mile, depending on the departure runway, up to 11,000 feet. The climb gradient is expressed in feet per nautical mile because the procedure designers don't know how fast your particular aircraft is traveling in a climb. Here's a snippet from an old Klamath Falls VFR sectional showing the topography around Alturas.
Jepp charts are kind enough to calculate the required climb rate for you, translating the climb gradient into feet per minute for a range of different climb speeds. If you use FAA charts, you can use a table in the front part of the approach booklet to do the conversion or just use your calculator:
(398 feet/NM X 100 NM/hour)/60 minutes/hour = 648 feet/minute
This climb rate at altitudes above 6,000 feet MSL is beyond the capability of many single-engine GA aircraft, so check your aircraft's flight manual. If you're flying a multi-engine aircraft, of course you'll want to look at the single-engine rate of climb performance, just in case.
Next, you'll want to do either an FDE prediction and/or a RAIM prediction prior to departure. Power up you Garmin GPS, bring up the Auxiliary pages, find RAIM prediction, and tell the unit to do it's thing. Remember that RAIM prediction uses a satellite almanac to predict the number of satellites your GPS antenna should be able to see, but it is not a guarantee that the in-flight RAIM calculations that the receiver makes will always succeed. Translation? Your RAIM prediction could succeed, but you could still get a RAIM failure in flight (though it is unlikely).
Since a pre-flight RAIM prediction is so important, why does Garmin insist on burying this feature, requiring a bunch of knob twisting and button pushing?
For this example, we'll do a trip from Alturas to Reno, Nevada using the CHOIR ONE departure, then direct to a fix on the RNO RNAV 16R approach. Press the FPL button, press the small knob on the lower right to enter cursor mode, scroll to the empty space below KAAT, then turn the small knob to spell out KRNO for Reno.
Press the PROC button, then scroll with the big knob on the lower right, highlight SELECT DEPARTURE, and press ENT. Select CHOIR1 from the list, and press ENT.
On departure, you can use the terrain view to give you an idea of where the obstructions are located as you climb.
As you approach the second waypoint, the 530W will give you a 10 second countdown before you need to change heading.
As you approach CHOIR, you'll get the same 10 second countdown, then the unit will tell you to turn. As I've said before, this countdown and turn instruction are a huge improvement from the earlier 530/430 units where the prompt was so short lived that it was easy to miss. Turn when the unit tells you to turn and you'll fly by the waypoint and get established on the airway without overshooting.
In a future installment, I'll cover flying a STAR.