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RC University: Airplanes



 


Landing Basics
Written by: Dr. Bob Motazedi
 

The landing pattern is the course the airplane flies before landing. It consists of four segments or legs (fig. 5-2). These legs are connected by gentle 90-degree turns. Together, they form a large rectangular course which can be flown by using either left or right turns. The direction depends on the flying field and the location of the runway (fig. 5-3).

The first segment of the pattern is called the upwind leg. This is located directly above the center of the runway. It begins at the closest end of the runway and usually extends past the farthest end. The airplane is flying into the wind on this leg. A 90-degree turn at the end of the upwind leg puts the airplane onto the next leg, called the crosswind leg. This is shorter than the upwind segment. Another 90-degree turn places the airplane onto the downwind leg. This segment parallels the upwind leg and the runway. The airplane is flying with the wind at this point.

The next segment is called the base leg. At this point, the plane usually begins its descent for an actual landing. The last turn puts the airplane onto a special portion of the upwind leg. The area between this last turn (the point at which the plane turns from the base leg back onto the upwind leg) and the touchdown point on the runway (where the airplane actually lands) is called the final approach leg. One word before I go any further, when practicing the landing pattern, keep the airplane at an altitude of at least 100 feet in the beginning sessions. This altitude will provide for a margin of safety.

As in all other cases, your instructor should first demonstrate how to properly fly the pattern. When it’s your turn, use a pattern large enough to allow time to correct errors but not so large that you cannot see the airplane adequately. Trial and error will help with this.

You should be able to follow the pattern with your airplane while using as little correction as possible. Perform each 90-degree turn using shallow banks not exceeding 20 degrees, and maintain a constant altitude throughout the pattern. The key here is practice. No RC flying maneuver will require more practice throughout your training than landing patterns. With sufficient practice will come more confidence, which you’ll need when you progress to the next step, landing.

Special Details

Now I’ll discuss each leg of the landing pattern in more detail, focusing especially on problems that can arise.

Let’s begin with the crosswind leg. Students often leave this leg too quickly, turning onto the downwind leg prematurely. Why is this a problem? Because the crosswind leg and the base leg need to be the same length, and by shortening the crosswind leg you also shorten the base leg, which may not allow you ample room to orient yourself to making the final turn onto the critical approach leg. But that’s getting a little ahead of ourselves. To simplify things, remember to stay on the crosswind leg for at least five or six seconds. This should put you in a good position once you reach the base leg. Once your airplane has traveled five or six seconds on the crosswind leg, you can make the turn onto the downwind leg. Once your airplane is established on the downwind leg, the most frequent problem seen is the tendency for student pilots to alter their course toward the runway instead of holding a true parallel course. This usually occurs for two reasons: (1) anticipation of the turn toward the runway, and (2) a visual parallax. The latter happens on a true parallel course when the airplane reaches that point for from its operator where it appears to be getting smaller. This illusion can create slight confusion, leading the pilot to assume some correction is needed to keep the airplane at a constant size. The response is often a shallow turn towards the runway. Such a maneuver, however, can considerably reduce the length of the base leg and make it difficult to perform a precise turn onto the final approach leg.

Correcting this problem is simple. As soon as you recognize the deviation, alter your course away from the runway at a 20- to 30-degree angle. This will allow you to re-intercept the downward leg, at which point you can easily make the turn onto the base leg. Fly the base leg just as you flew the crosswind leg and at the same constant altitude. You won’t need to adjust the throttle.

The turn onto the final approach leg is the most difficult part of the pattern. At the end of this turn, the airplane must be precisely on the extended centerline of the runway on a heading that will take the airplane directly over the runway. You’ll need good judgment combined with skill and anticipation to effect this turn precisely. The turn should begin well in advance of the intersection of the base leg and the final approach. Several problems can arise at this point:

  1. If you begin the turn too late, the airplane will over fly the upwind leg and end up on the opposite side of the course. If this happens, you’ll need to make gentle S-turns to return your airplane to the correct course. At no time, however, should the angle of bank exceed 20 degrees, even during a correction. Too steep of a bank angle at this point can result in a rapid loss of altitude and a dangerous flirtation with the ground.
  2. If you begin the turn too soon, the airplane will veer off the course and end up on the inside of the upwind leg. There are two ways to correct this. The first is employed when the airplane is far off the course. Make a gentle S-turn toward the final approach leg. Once the airplane is close to the correct course, make a shallow turn to intercept the final approach leg. The second correction is used when the airplane veers only slightly off course. In this case, simply decrease the angle of bank and slowly turn onto the final course.
  3. The final problem is one of anticipation. As you know, the airplane usually takes a few seconds to turn to a level attitude when completing a turn. As a result, even though the airplane may be on the extended center line from the runway by the time it’s leveled, its heading may deviate from the course (fig. 5-9). To prevent this, begin to level the wings when the airplane’s heading is approximately 30 degrees from the final heading. Once this turn is completed, the airplane should be level and on the proper heading. This is called anticipating the final turn.
Awareness of these potential problems, together with lots of practice, will help you master the difficult turn to the final leg. Once the airplane is established on the upwind leg with the proper heading, concentrate on keeping the wings level. For instance, any wing drop must be corrected quickly. If the wings are kept level, the airplane will fly directly over the centerline of the runway. Now you can see how the wing leveling procedure that you practiced earlier becomes important. Once you master this procedure, the final approach becomes much easier. As I’ve mentioned, before actually landing, you should practice flying the landing pattern many times. Continue past the landing area toward the end of the upwind leg and start the pattern over. Keep those wings level, using gentle S-turns if necessary to return the plane to its normal course.

To order the full text of Dr. Bob's book, "Safe and Easy Flying" or any of the many titles by Dr. Bob, call 1.800.390.HAWK.

 
 



 



 
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