Home | Issues | Articles | Aviation Glossary | Q&A | A Personal View | Polls

07/09 – Pilotage - Interpreting Topographical Features Flying High

By Steve Krog

Throughout the past several issues of Reach For The Sky, we have discussed many of the things student pilots are required to know and understand prior to making their first dual cross-country flight. However, there is one more step you will need to become familiar with before planning and flying your first dual cross-country flight—pilotage. Remember making your very first flight? Once in the air everything looked different, yet it all looked the same. For one fleeting moment the thought passed through your mind, “How will I ever find my way back to the airport?”

Pilotage, the most basic method of visual navigation, is an acquired skill you learn by practicing. It’s the ability to look at topographical features seen on the surface of the earth while in flight and match those features to those depicted on your VFR sectional chart. It involves comparing the chart to the ground features along your planned route of flight and determining your actual position.

Even though your instructor never mentioned the term during the first several hours of instruction, you were already learning pilotage. You began recognizing landmarks and determining where they were located in relation to your airport. Within several hours of dual instruction flight you were able to find and return to the airport by looking at landmarks. This is the first phase of pilotage.

So let’s expand your knowledge of pilotage in preparation for that first dual cross-country flight. Using the exploded view of the VFR sectional chart, note the location of the Hartford Airport. Located several miles southeast of the airport is a small body of water shaped somewhat like a horseshoe. It appears large enough to easily spot from the air. The city of Hartford depicted by the yellow area on the chart is located south of the airport.

Flying on a southeasterly heading this is what the actual topographical features look like from the air when seen from the airplane. Note the airport just off and below your right wing. The many buildings and trees just beyond the airport tell you that it is a town or small city. Looking back at the chart the yellow area outlines the city of Hartford. From the air it should be off your right wing.

Assuming the body of water is that which is depicted on the sectional chart, you need to take a closer look before confirming it to be what you think it is. Look again at the sectional chart, noting that there is a four-lane highway and a railroad track that run horizontally near the north end of the body of water. Try to find them in the photo. From this distance and at an altitude of 1,500 feet AGL (above ground level) they are not visible.

Continuing the flight on a southeasterly heading, the exact shape of the body of water can now clearly be seen. It is in the shape of a horseshoe with a small peninsula at the south end. Comparing the body of water to the symbol on the chart tells you that they are one and the same. Also take note of the four-lane highway along the near edge of the body of water. It can now be easily seen and further confirms your exact position.

Turning more eastward refer again to the chart and note that the four-lane highway intersects with a second four-lane road which runs on a northwest to southeast direction. Look at the next photo and you’ll quickly recognize this large intersection from the air.

From this point in the flight, turn northward and fly parallel to the four-lane highway. The sectional chart indicates the highway makes several gradual curves. Additionally, there is a railroad track that runs parallel to the highway.

Studying the photo that follows, the gradual curving highway and parallel railroad track to the left are clearly visible from the air. Without using the highway for reference, though, the railroad track can be somewhat hard to spot.

As you view the aerial photo, note the oval racetrack in the foreground. Sometimes these topographical features will be depicted on the chart. In this case it is not, but in more rural areas prominent landmarks such as racetracks are depicted to aid the pilot.

High-tension electrical power lines are sometimes used for checkpoints along a VFR route of flight. In more rural areas of the country they may serve this purpose quite well. However, they can be hard to spot from the air and they can be confusing. Not all power lines are depicted on the sectional charts.

Look closely at the sectional chart again in the area surrounding the intersection of the four-lane highways. There are no symbols indicating high-tension power lines, yet there are two parallel lines running east to west.

At first you may not even see the parallel power lines as you study this photo. However, they are there - but note how difficult they are to see against the various crop fields. For this reason many instructors do not recommend using them for primary checkpoints along your desired route of flight. If there are prominent power lines along your route of flight, use them as secondary checkpoints to aid in confirming your position.

Spending time studying your sectional chart will provide you with a solid background in being able to recognize topographical features as you prepare for your first dual cross-country flight.

There are several other exercises you might use to prepare for that first flight. Recall that the sectional chart uses a scale of 1:500,000. In more common terms that calculates to eight (8) statute miles per inch. Using this scale, practice estimating distances between towns, lakes, or other topographical points and then measure them. Here’s a tip: the distance between the end of your thumb and first joint is about one inch. Use your thumb to help estimate distances. This exercise may sound a bit silly but it may help you out of a deteriorating situation while in flight when decisions need to be made rapidly.

Being able to accurately determine distances while in flight is one of the weakest knowledge areas among pilots. Frequently a pilot will make a radio call to an airport with intentions of landing. The pilot may state, “This is Cessna N1234, 5 miles south inbound for landing at Hartford.” Other flight traffic in the area immediately begin visually scanning the area approximately 5 miles south of the airport looking for the inbound traffic only to find the aircraft is but a speck on the horizon and well over 10 miles out. Needless to say, the approaching aircraft has created confusion, concern, and may even have compromised safety due to the inability to estimate distances.

Teach yourself how to estimate distances over the ground between two objects seen on the ground. For example, look up how long a lake is, or how far apart two towns are on the chart, and then remember what that distance looks like out the window of your airplane. It will make you a safer pilot.

In the next issue we’ll draw out our plan and determine checkpoints for that first dual cross-country flight.