by Charles Gulick
The Lone OMNI-Ranger
Fairchild Int'l, Port Angeles, WA to Olympia, WA
North: 21739. East: 6377. Altitude: 289. Pitch: 0. Bank: 0.
Heading: 265. Airspeed: 0. Throttle: 0. Rudder: 32767.
Ailerons: 32767. Flaps: 0. Elevators: 32767. Time: 14:30.
Season: 3. Cloud Layer 1: 7000, 4000.
Wind Level 1:4 kn., 90 deg. Surface Wind: 4 kn., 255 deg.
This weather's no surprise. Port Angeles is one of the world's wetter places. It once held the U.S. record for a year's rainfall.
Get out your Seattle chart, so we can explore our location. I want to show you some more things about tuning and understanding VOR (Very-high-frequency Omnidirectional Range) transmitters, or OMNIs for short.
Note that Fairchild International is rather isolated out here on the Olympic Peninsula; it's actually on a little finger of land called Ediz Hook, which you can see on most maps of Washington, although it isn't delineated on your chart or on radar. There's daily ferry service between here and Victoria on Vancouver Island, British Columbia.
Look at the VOR stations depicted on your chart: Tatoosh and Hoquiam on the Pacific, Bayview in the extreme north of the state (about 35 miles from the Canadian border), and then a string of four in the Puget Sound area: Paine, Seattle, McChord (Piper chart only, though the station exists for Cessna as well), and Olympia.
See if you can raise Olympia on your NAV. Then tune Tatoosh and see if you're within range of its transmitter. If you are, first use a straightedge from the airport to the OMNI center and estimate what TO radial you're on, then use your OBS to see how close you came.
How about Hoquiam? Do you think you can get a reading? Try it.
How about that? Sitting here on the ground, you're in touch with a pinpoint 75 miles away, across mountains some of which reach nearly 8000 feet into the overcast. That's hard to believe, especially since OMNI is a line-of-sight system.
Just to make sure you understand your OMNI procedure, use your OBS to get a heading to Hoquiam, as if you were going to fly straight to the VOR station. What heading did you come up with?
Now lay your straightedge on the chart so it intersects both Fairchild and Hoquiam. Get the idea?
Well, we want to fly to Olympia Airport this afternoon, so let's get to it.
There are two ways we could fly there, but contact isn't one of them, because there are no landmarks of any kind for quite a few miles. The first way to go is to find a VOR station near Olympia, which is in range, and fly toward it until we can pick up the Olympia transmission, then turn and fly inbound on one of its radials. The second way is to eyeball or straightedge a heading to Olympia using our chart, then fly that heading until we can get a more precise one on our OBI. The more direct method in this case is the second.
So use your straightedge and decide what heading you'll want to start out on. Then ready your airplane for takeoff and let's go.
Steer to keep the end of the runway straight ahead of you. Back pressure at 80 KIAS … take it off when you're climbing … get your flaps off … get rid of your takeoff trim … reduce your power for a 500-FPM climb (2105 RPM in Cessna and 2250 RPM in Piper). You're going to have this down pat pretty soon!
Turn to the heading you chose as you pass through 1000 feet. That way you'll steer clear of the Tri-motors and Spads and all. By the way, a good general rule for turning to a new heading is: Turn left for a lower number, right for a higher number, which is certainly logical enough—unless your heading is in the north quadrant. Then you have to visualize the compass rose and use some logic. If you were heading 10 degrees, for example, and wanted to head 300, you wouldn't turn right just because 300 is a higher number. But the general rule works for the majority of small turns and heading corrections.
Our cruising altitude will be 7500 feet. So climb right on up into and through the overcast. You'll need more power as you gain altitude to keep your climb rate at 500 FPM. So use it. Remember that a faster climb won't get you to Olympia faster, even though it will get you on top faster. Notice that your airspeed stays nice and fat when you hold 500 FPM.
When you're in the overcast, pin down the precise radial you want to fly, and center the needle.
What's the matter? Things aren't right? Is your heading way off what you thought? If it is, can you figure out why? Use your full scan. Is everything where it's supposed to be? Did you forget something?
This is no time to panic. It is time to think. (Of course, if everything is as you expected it to be—your estimated heading and the present radial agree within a few degrees, and you're ticking off the miles to Olympia as you tick off the altitude to 7500—then you can relax for a minute and have a cup of coffee. But if not, no coffee for you yet.)
Is everything okay on your panel? Airspeed good? Attitude right? Altimeter showing climb too? VSI confirms it? 500 feet Up? Heading? Heading what? Does that look right? Bank and turn okay?
So how about the rest of the panel? Fuel and oil okay? COM radio—haven't used it. NAV1 where it should be? Tuned to Olympia?
Aha! If your NAV1 is still tuned to Hoquiam, that's your problem. I deliberately neglected to tell you to tune your NAV back to Olympia before we took off. If you did, then kudos to you. If you didn't, then do it now. I could tell you everything every time we fly, but the more we fly together, the less I will tell you, because I won't always be flying with you.
Now, so that we'll all be flying together—as Bruce Artwick describes us, “in formation, I assume”—let's all get on the 138-degree radial to Olympia. If you're there already, fine. Otherwise, and for future reference if you don't need it now, here's how to change easily from one radial to another:
- Be sure you are tuned to the OMNI station to which you want to fly.
- Use your OBS to find out what radial TO that station you're presently on. When the needle is centered, the OBI reads out the radial you're on, but that's all it tells you.
- Turn to the heading indicated by the OBI, and point your aircraft to center the needle, flying the needle in the usual manner. You're now bearing TO the station, with your heading and the OBI course selector in agreement (though not on the radial you wish to fly.)
- Reset the course selector to the desired radial. (If it is not a viable TO radial, the OBI will read OFF or FROM, in which case set the OBI to the reciprocal heading indicated and fly that or choose a new heading.)
- Turn to intercept the desired radial, then fly the needle.
But which way and how far do you turn?
If the OBI needle is onscale, of course, you simply fly it as always. If it's offscale, here's where our wheel analogy comes in handy. If you imagine yourself on a spoke of a wheel whose spokes are numbered clockwise, you'll be able to visualize which way to turn. If you're on, say, spoke 90, and you want to be on spoke 40, you simply turn right to get over there and intercept it. If you're on spoke 120 and you want 128, you turn left.
Is a radial of a lower number always to your right, and one of a higher number always to the left? No. Because we're dealing with a 360-degree circle, remember. If you're on the 30-degree radial and want the 330-degree radial, you'll find it to your right. Think of yourself, again, as out there on the 30th spoke, looking toward the hub. Where's the 0 spoke in relation to you? And where's the 330? Even further right, right? If you use the wheel analogy and visualize yourself on a specific spoke, headed toward the hub, you won't turn in the wrong direction.
It's important to realize that, from any given position on the radials of a VOR station, the radials on the near semicircle are FROM radials, and those on the other are TO radials. Some theoreticians say we should think of the nearside radials simply as radials and the farside radials as headings, and if this helps you understand the situation it's fine with me. But also remember that no OMNI radial is a heading in and of itself. Simply heading 80 degrees does not put you on an OMNI heading of 80. You could fly a heading of 80 until your plane ran out of gas, yet never be anywhere near the 80th radial of the station you wanted to fly to or over. Only when you're on a heading of 80 degrees and your OBI is set to the frequency of the VOR you want to fly to and the course selector is set to the 80-degree radial and the OBI needle is centered and the OBI reads TO, are you on the 80-degree radial to the station you've tuned.
Now to the second part of the question above: How far should you turn to intercept a desired radial, if you've done everything else right?
The answer depends on how far you are from the station, and how big a course correction you're making. As with any wheel, the further out you go, the greater the distance between spokes.
As a general rule, if you're 30 or more miles out, turn to a heading 60 degrees higher (right turn) or lower (left turn) than your original TO heading, and fly until you intercept the desired new radial. Closer to the station, reduce the heading change accordingly, adding or subtracting 50, 40, or 30 degrees.
We are talking here about distinct heading changes, not corrections for drift, or corrections to center the needle. The general guide for minor corrections is a 30-degree cut maximum, and when you're close to the station or flying an ILS approach, corrections of only a few degrees.
Remember that you can use your other OBI, NAV2, as a check on your position throughout the change. Just set it to tell you what radial you're on, and keep centering the needle as you progress from that one to the next, and so on, until you're where you want to be.
Now, when you're on the 138-degree radial to Olympia, don't change anything. Just go on to the next flight.