But what is the best way to teach taxiing? Just as with any other lesson, first determine your lesson objectives, come up with a plan to teach the skills and techniques to reach those objectives, and then use performance criteria to check and evaluate progress.
A good place to start a lesson on taxiing is with a definition. Taxiing is the controlled movement of the aircraft under its own power over the ground. You can emphasize that the key word here is controlled. In every lesson, taxiing included, we want our students to develop and exercise control over the aircraft.
To make it easier for your students, divide aircraft control into two elements-speed control and directional control. In teaching these elements, you should also be teaching safety, minimizing wear and tear on the aircraft, and smoothness. Safety means such things as minimizing propeller blast and maintaining heads up and eyes outside. Minimizing wear and tear means using proper technique so that tires and brakes don't wear out prematurely. And smoothness means that aircraft movement should be free from abrupt starts, stops, and excessive lateral forces in turns.
Now, with this very detailed definition, and with all of these different elements to consider, we can see that taxiing well involves more than just getting from point A to point B.
Speed Control
One of the first elements students must learn is speed control. Here is where an understanding of Newton's laws of motion begins to be helpful. Newton's first law of motion states that, "Every body continues in its state of rest or of uniform speed in a straight line unless it is compelled to change that state by forces acting on it." The tendency of a body (or aircraft) to maintain its state of rest or of uniform motion in a straight line is called inertia. As a result, Newton's first law is often called the law of inertia.
Applied to an aircraft, this means that it is going to take more thrust to get it moving forward than is required to keep it moving forward. How much thrust is necessary to start moving? Jet pilots who are familiar with the inertia of their larger aircraft call this amount of thrust "breakaway thrust." They gradually apply just enough thrust to break inertia and get the aircraft moving. Then they reduce power to the amount necessary to maintain the desired taxi speed.
Our students should be taught to use a similar technique. When starting to taxi from a standstill, have them gradually add power (you can give them a target power setting, but usually no more than 200 or 300 rpm above idle rpm) to get the aircraft moving. Once the aircraft reaches the desired taxi speed, they should retard the power as appropriate to maintain that speed.
One of the most common problems you will see here is that students add excessive power to make the aircraft accelerate quickly. Some students mistakenly believe that an aircraft should accelerate like a car. The result is usually an abrupt start followed by excessive taxi speed. You must teach students to be patient and explain that maintaining control during taxiing means being able to stop quickly, not accelerate quickly.
Once under way, and as early as possible in the taxi, have your students perform a brake check for safety. They should check for the typical warning signs of improper brake function such as weak braking action, squeaking or binding noises, spongy-feeling brake pedals, or excessive brake-pedal travel. This brake check should be smooth-so smooth that passengers don't even notice. Teach your students to reduce power rather than use the brakes to slow taxi speed and before making turns. This will minimize brake wear and help prevent overheating. When brakes are needed, they should be used intermittently, rather than continuously.
Momentum is another physics concept that plays an important role in speed control during taxi. Momentum, which is simply mass multiplied by velocity, aids greatly in turns and helps with directional control. To maintain constant momentum, the aircraft needs to maintain a constant taxi speed. Have students adjust the throttle as necessary to maintain this desired taxi speed. Initially, many students use excessively large power adjustments to control taxi speed. One method that can be used to combat this common error is to assign restrictions on the use of power. For example, allow students to use only between idle power and 1,300 rpm while taxiing. Another way to help avoid large power adjustments is by making small corrections as soon as the taxi speed starts to change. Students should be aware of slopes, headwinds, and tailwinds, because these will all cause variations in taxi speed. If the speed gets too fast, have students reduce the power to idle before using the brakes. What you don't want to see is your students braking with a power setting higher than idle. That is poor technique and causes excessive wear on the brakes.
We must teach our students to taxi at a safe speed. But what is a safe taxi speed? It is difficult to set any rule. What is safe under some conditions may be hazardous under others. In congested areas, the safe taxi speed will be much slower than in uncongested areas. The primary requirement of safe taxiing is having positive control-the ability to stop or turn where and when desired. Students should taxi at a speed that is slow enough so that the aircraft can be stopped promptly and safely.
Directional Control
Directional control (or steering) is another element of taxiing that our students must learn. Have students strive to taxi right on the yellow taxiway line. If they eventually go on to the airlines and taxi the big jets, being exactly on the yellow line is not just good practice-it is imperative.
One of the first and most common problems students have with directional control is that they will try to "steer" the aircraft with the control wheel instead of using the rudder pedals. To break this habit early, have them place their "steering" hand somewhere other than on the control wheel.
The next challenge is to teach your students how to determine when the aircraft is centered with the nosewheel actually on the yellow line. Since the view from each cockpit is different, one of the best ways to teach this skill is by demonstration. You can taxi on the yellow line for a while and then let the student take over.
While the student is taxiing, give callouts as to where the nosewheel actually is in relationship to the yellow line. For example, you can tell them that the nosewheel is one foot to the left, or six inches to the right. If it is a side-by-side trainer, having the student lean over toward the center of the cockpit helps to develop the proper perspective. Once your students have developed the correct sight picture from the cockpit and can tell when the nosewheel is on the yellow line, the next step is to teach them how to keep it there.
Once under way, students will find that staying on the yellow line requires a fair amount of attention. One of the most irritating things to many student pilots is the rudder-to-nosewheel interconnect rigging. Students think that if the rudder pedals are perfectly centered, the aircraft will taxi straight ahead. Unfortunately, this is rarely the case. It may be true with your brand-new car or truck, but you might say that most training aircraft are in dire need of a front-end alignment. Sometimes, to get an aircraft to taxi straight ahead requires the rudder pedals to be substantially displaced either left or right of center. This takes some getting used to, but you can reduce your student's frustration by making this point clear before taxiing out.
Until students learn to anticipate rudder corrections, one common problem you may see is weaving. Generally, students weave (which is really overcontrolling) because they aren't looking far enough ahead of the aircraft to anticipate the required rudder corrections. They think that they are in a sports car with lightning quick steering, which causes them to make their rudder inputs too late. To help mitigate weaving, have students look approximately 50 to 100 feet ahead of the aircraft. As soon as they detect that the aircraft is deviating from the desired heading, they should make a rudder-pressure correction.
Once students get a feel for taxiing straight ahead, it is time to try some turns. Just as in flight, students must lead their turns, both when going into and coming out of a turn. Teach them to lead turns by applying rudder pressure just before the turn is to be negotiated and releasing (or adding opposite) rudder pressure just before the aircraft reaches the desired heading. Tell your students to think of coming out of a turn as starting a turn in the opposite direction. Students should try to maintain directional control using only the rudders to minimize wear on the brakes. Of course, if a tighter turn radius around corners is required, students can use the technique of dragging the brake on one side to effect a tighter turn radius.
You should closely monitor your students' taxi speed. Excessive taxi speed can be dangerous when negotiating a corner in an aircraft. A certain amount of momentum is good and can carry the aircraft through a turn, but you may want to have students slow down before starting a turn. Aircraft are air machines, not ground machines. With their small tires and closely spaced wheels, aircraft can easily tip over, swerve, or ground loop, especially in strong winds. But it's not always easy for students to find the right balance between slowing down to negotiate a turn and slowing down so much that the aircraft can't turn. If an aircraft isn't rolling, it isn't turning. Students must keep the aircraft rolling if they want it to change direction. Don't let your students lock up or hold the brakes when they want the aircraft to turn. If the aircraft stops moving, no amount of rudder pressure or brake pressure will result in a turn.
Finally, teach students to let the nosewheel straighten out before coming to a complete stop. This will reduce strain on the nosewheel and gear assembly and ensure that the aircraft will start out going straight ahead with no directional surprises.
Safety
Lessons in safety can be some of the hardest to teach our students. This is because at every airport there are examples of certificated pilots, even instructors, using unsafe practices that our students observe, learn, and tend to copy. In these cases, we must teach not only by showing what to do, but also by pointing out what not to do.
Many pilots taxi too fast. Your students should taxi at a speed commensurate with the situation. Some pilots spin aircraft around into tiedowns with high power settings. Teach your students to use the tow bar. Some pilots are totally unaware of their own prop wash. Your students should always be aware of people and objects around and behind their aircraft. Some pilots push the limits when taxiing in tight spots. Anytime your students have a doubt about wingtip or tail clearances, they should stop the aircraft and have someone outside check. If no help is available, the engine should be shut down and the aircraft should be towed rather than taxied under its own power.
Make sure to discuss safety out on the ramp as well. Your students should be aware of the dangers of propeller wash, rotor wash, and jet blast from other aircraft while taxiing. They need to know how closely they should taxi behind other aircraft, including jets and helicopters. Remember that a hovering helicopter can generate enough rotor wash to easily flip over a light trainer. Students also need to be aware of the dangers associated with taxiing in strong winds and importance of using the proper control inputs.
And, with the recent increase in the number of runway incursions, it is imperative that you review the pertinent sections of the Aeronautical Information Manual with your students. Review the sections dealing with taxiway and runway signs and markings, pilot responsibilities and readbacks, and compliance with air traffic control taxi instructions. Teach students that if they are ever in doubt, they should stop the aircraft and ask the ground controller for clarification or directions. And make sure that they know how to request, and when to use, a progressive taxi clearance.
Many instructors don't bother to teach taxiing. They may think that their students will pick it up as they progress through their flight training. But this is not a good assumption. Taxiing is a skill that's worth a lesson. But with help from Newton, getting your students to give you that smooth ride from point A to point B is a little bit easier.
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