Getting Around (at 5000 Feet)
by Norm Beaudette

Ever wonder how pilots are able to figure out what direction to fly in, to get to their destination - with changing winds, clouds, and no road signs to guide them?

Actually, pilots have quite a few devices to help them find their way.  These include maps, various types of radios, and just plain looking around.  Pilots normally use all three when they fly.

Pilot maps are actually called sectionals, and these contain lots of information about roads, railroads, lakes and tall buildings that can easily be seen from the air.  Of course, the sectionals also contain the positions of all airports, as well as airport runway lengths, runway direction, radio communication frequencies and lots of other useful information for pilots.  Here's a picture of part of a sectional, with the Clermont County airport (our home base) clearly marked on it. 

The numbers that appear next to the CLERMONT CO name tell the pilot that the airport's official identifier is I69, its elevation is 844 feet above sea level, its longest runway is 3500 feet long, it has runway lights for use at night (L), and that pilots should communicate with each other on a radio frequency of 122.975 MHz (called the Common Traffic Advisory Frequency, or CTAF, and designated by the "circle-C" symbol).

The large reddish symbol (its actually a color called magenta) with the slash running through it shows the exact  location of the airport, and the slash is actually used to show the direction of the airport runways.  Clermont County has only one runway surface, but since a pilot can take off in either direction on that surface, it actually has two runways.  To tell runways apart, they're each given a number, and that number is determined by the compass direction that the pilot would be headed in if he were to take off.  Clermont County airport's two runways are Rnwy 4 and Rnwy 22.  That's because the runways have compass headings of about 40° in one direction and 220° in the other (the heading is divided by 10).  The pilot usually decides which runway to use based on the direction of the wind - always trying to take off into the wind.

There's another airport on this part of the sectional, but it's in blue instead of magenta.  The airport is Cincinnati Lunken field, and it's in blue because, unlike Clermont County airport, it has a control tower.  When an airport has a control tower, pilots must get permission (called a clearance) before they're allowed to land.  The pilot obtains a clearance by talking to the person in the control tower over the airplane's radio transmitter, usually when the pilot is about 10 miles away from the airport.  Did you notice that Lunken field has 6 runways?!  Incidentally, the yellow area to the northwest of Lunken field is part of the city of Cincinnati, and the river nearby is the Ohio River!

There are lots of other symbols and markings on the sectional that are useful to the pilot.  For example, the yellow areas designate populated areas.  This is especially useful at night, since these areas will be full of city lights, making them easy to spot from the air.  The "tepee-shaped" symbols designate tall structures, called obstructions.  These are usually either radio towers, water towers, or very tall buildings.  The obstruction's elevation at its highest point is given next to the symbol.  Note the two side-by-side obstructions just south of Lunken field, at an elevation of 771 feet MSL (Mean Sea Level, that is, above sea level).  These are actually bridges over the Ohio river.

Sectionals are a very important part of a pilot's flight tools.  Because the information is so important, they're updated twice a year.  In fact, the CTAF at Clermont County airport recently changed from 122.7 MHz to 122.975 MHz.  Without an up-to-date sectional, a pilot might easily try to communicate on the wrong frequency!  For reasons like this one, pilots are required by law to use updated sectionals whenever they fly.

If a pilot doesn't have very far to go, and the skies are clear, he or she will often just use a sectional to get to his or her destination.  This type of navigation, where the pilot uses landmarks along the route, comparing them with the markings on the sectional, is called pilotage.  Another type of navigation, called dead reckoning involves making mathematical calculations to estimate where the aircraft will be in 20 minutes or so, based on where it is at the present time and how long it took for it to get there from its previous location.

For destinations that are more than just a few miles away, pilots have lots of different types of radios that they can use.  Using radios to navigate is called radio navigation (duh!).  As you might expect, some of these radios use signals that are similar to the AM and FM radios we use for listening to our favorite music.  One difference is that the radio is actually connected to a little meter on the airplane's instrument panel.  The meter usually has an arrow-shaped needle that tells the pilot which compass direction to head in, to fly towards (or away from) the radio signal.  Since the sectionals all show where the radio towers are located, the pilot simply looks for radio towers that lie between his current position and where he wants to go.  He then tunes in the station and flies to it; then, when he passes it, he just tunes in the next station and flies towards that one, repeating the process until he arrives at his destination.  Pretty simple, isn't it?

The latest craze in radio navigation is something called GPS, which stands for Global Positioning System.  With this type of radio (which depends on a bunch of satellites orbiting overhead), a pilot can determine her position, and even her altitude, within a few yards!  Some of these systems even have a little computer-like screen that shows a moving map of the area around the airplane, including the positions of airports.  So as the pilot is flying, if she sees that the airport is over to the left a bit on the screen, she just turns the airplane a little to the left!  Some of these systems have become so sophisticated that they can be connected to what's called an auto-pilot, and they can actually steer the airplane along an entire course, maintaining altitude along the way.  Under certain conditions, some of these are even able to land the airplane!

Copyright © 2001 by Norm Beaudette.  All rights reserved.

Want to read more about navigation?  Here are some interesting links to check out:

Did you know that anyone can buy a sectional chart?  They can be obtained for about $8 at any airport FBO.  (Make sure to specify that you want the Cincinnati sectional!)  What's an FBO?  Well, an FBO, or Fixed Base Operator is a person or company that provides services - like fuel, repairs, and even airplane rentals - at an airport.  There's no need to be afraid to visit your local airport's FBO.  Just tell him you're interested in aviation, and that you would like to look at some airplanes.  He may even show you around a bit, (especially if you buy a sectional!).  One thing to always keep in mind, however, is to NEVER go near any airplane without the permission of the FBO!