December 2004Features

Tackling taxiing

Smooth techniques for surface transit


I am not so far from my first flight lesson that I don't remember it. The instructor took me out to the airplane, showed me how the preflight inspection is done, and put me into the left seat. Up until that time, I thought we would just go out for a little sightseeing excursion. You know, get used to being up in a small airplane -- especially as I had never been close enough to touch one before. Then he instructed me on how to start the engine, which got a "hmmm..." going in my head. He progressed to an overview of how to control the airplane during the taxi to the runway, which intensified the "hmmm." He finished up with instructions on how to take off, and indicated that I would be doing that! Well, I went far beyond "hmmm" and have never forgotten the state of half-panic, half-exhilaration I experienced as the airplane lifted off the ground.

Don't become a statistic
Help in avoiding runway incursions

Keep in mind that where you taxi can be just as important as how you taxi.

For several years, the FAA, AOPA Air Safety Foundation (ASF), and the aviation community have been battling runway incursions, and there has been some success. Although totals nationwide have dropped from 407 incursions in 2001 to 339 during 2002 and 324 last year, according to FAA data, the most serious runway incursions actually increased in early 2004.

A runway incursion takes place whenever an aircraft enters a runway at a towered airport without permission from air traffic control (see "Two Aircraft, One Runway," July 2004 AOPA Flight Training). Most are minor, as when an airplane noses across the hold-short line, but are incursions nonetheless. But others result in go-arounds or collisions, which often involve fatalities. The nosewheel doesn't even have to cross the hold-short line-if any part of the aircraft crosses the line, an incursion has occurred.

FAA statistics show that more than half of all runway incursions are caused by pilot deviations, when a pilot deviates from a clearance-another term for pilot error (see "Incursions R Us," August 2004 AOPA Pilot). And nearly 70 percent are general aviation pilots. Sometimes pilots read back hold-short instructions correctly and enter the runway anyway. Other times, pilots don't understand airport signage and surface markings. Distraction often plays a role.

Doug Draper, a flight instructor at Buchanan Field in Concord, California-an airport with a reputation for incursions-offers some tips that will help you keep from becoming a runway-incursion statistic:

  • Have a taxi diagram for the airport on your lap, and use it. Diagrams for all towered airports are available online, free to any pilot, through ASF.

  • Write down the taxi clearance and verify it.

  • If you get confused, ask for progressive taxi instructions (see "Aviation Speak: Progressive Taxi," p. 96).

  • When you stop at hold lines, position yourself to face the landing traffic.

For an excellent overview of airport surface operations, take the free online ASF Runway Safety Program. Links to that online course, as well as ASF's Operations at Towered Airports and Operations at Nontowered Airports Safety Advisors -- as well as related quizzes, runway signage flash cards, and other resources -- are conveniently collected for you online.
--Mike Collins

In retrospect, I think maybe I should have progressed beyond "hmmm" when he indicated that I'd be taxiing the aircraft to the runway. Taxiing is not as simple as it sounds, and inattention or bad habits during taxi can result in mishaps. So let's take on the taxi phase of flight.

The typical light training airplane has combined rudder and brake pedals that are operated with your feet. In the air, the brakes, of course, do nothing. The rudder pedals control the back-and-forth movement of the rudder to manage yaw in flight. The brakes are usually actuated by pressing on the tops of the pedals and the rudder actuated by pressing on the bottoms of the pedals.

On the ground, the brakes are used to slow and stop the airplane. The rudder will still move back and forth in response to pressure on the rudder pedals, but most light trainers also have a steerable nosewheel that also will move in response to the pedals. Others have a castering nosewheel, which is not connected to the rudder pedals. Regardless of the type, unlike your car, an airplane is steered on the ground with your feet, and not with movement of the control yoke. This is somewhat akin to sitting on a snow sled and steering it, with one important difference: On the sled, to go left you press right, and vice versa, whereas with the airplane, you press the left pedal to go left.

When we taxi on a taxiway, we use the entire surface by staying directly on the yellow centerline. When you first learn to taxi, you may find that this is not quite as simple as it sounds. Most students will encounter one of two common problems: either weaving back and forth along the taxiway, or taxiing to one side of the centerline. Both are fairly easy problems to fix.

Taxiing to one side of the taxiway centerline usually occurs when you are looking closely in front of the airplane while taxiing. Because you are seated off to one side in a typical trainer, you're viewing the nose of the airplane and the centerline at an angle, making it look like you're on the centerline when in fact you aren't-a parallax view. The solution is to look down the length of the taxiway as you taxi, which minimizes parallax as well as allows you a better opportunity to avoid things that might be in your way. The airplane will then appear to be on the centerline when it actually is.

If you weave back and forth during taxi, you are probably overcontrolling with the rudder pedals. I find that this is often the result of poor positioning of the feet. Before starting the engine and while seated in the airplane, adjust your seat-both height and distance from the pedals-until you can sit comfortably with your heels resting on the floor of the cockpit and your toes resting on the bottom (rudder portion) of the pedals. You want the weight of your leg resting on your heels, and to be able to move the rudder pedals by leaving your heels in place and "pointing" with your toes, or at most by sliding your heels slightly forward. This foot positioning will allow you to have a greater feel for just how much pressure you're putting on the rudder pedals-a feeling that becomes lost when the weight of your legs is resting on the pedals themselves. Unless you have very big feet, when they are correctly positioned you will not be able to reach the brake portion of the pedals with your toes, meaning that you cannot inadvertently apply brakes.

Although brakes on airplanes work differentially (meaning that when you press only one pedal, the brake will be applied only on that side of the airplane), when cornering during taxi it's best to avoid using the brakes to accomplish the task unless you need to make a particularly sharp turn. Just as turning the front wheel of a tricycle causes the tricycle to turn, turning the steerable nosewheel of a tri-cycle-gear airplane will cause the airplane to turn. This minimizes heat buildup in the brakes and the resulting problems that can arise. (If the aircraft has a castering nosewheel, you probably will have to use differential braking when taxiing around corners.)

Engine settings during taxi are important, too. Right after engine start, you adjust the throttle so as to obtain the lowest rpm setting consistent with smooth engine operation. You may need to lean the mixture somewhat, especially at higher-altitude airports, to avoid an overly rich setting that can cause fouling of spark plugs during taxi. Your instructor can show you how much leaning is appropriate for your particular airplane.

When beginning to taxi, advance the throttle just enough to get the airplane moving forward. Apply the brakes smoothly to ensure that they are working correctly. Assuming you have applied both brakes evenly, any pulling to one side or failure of the airplane to stop is an indication that one or both brakes have failed, which will require the attention of a mechanic. If the brakes are working correctly, release them and allow the airplane to begin moving again. Then smoothly readjust the throttle until the airplane maintains a steady brisk walking speed.

Try to avoid changing the throttle setting during taxi. Remember that the brakes work differentially, so if you need to slow down while taxiing straight ahead, you will need to apply even pressure to both brake pedals at once. If you have your feet positioned properly, this will simply require that you slide your feet up the pedals, which will also lift your heels off the floor, and you will be able to feel that you have applied the brakes evenly by feeling the same degree of pressure from the pedals against your feet. When coming to a halt and preparing for the engine runup, position the airplane and straighten the nosewheel by letting the airplane roll forward slightly while applying pressure to the rudder pedals so that they are evenly aligned. This will avoid putting side loads on the nosewheel itself during the runup.

Taxiing in a crosswind requires additional control inputs to keep the airplane's tires well planted and, in a strong crosswind, to prevent a wing or tail of the airplane from being lifted by the wind. You will find that applying the correct aileron and elevator/stabilator inputs for crosswind taxi operation will reduce the tendency of the airplane to weathervane (point into the wind) in response to the pressure of the wind on the vertical stabilizer and rudder.

It can be confusing remembering which way the ailerons should be positioned during a crosswind taxi, so I teach this memory aid: When you hold the yoke, your thumb points up; when the wind is coming from in front and to one side (a quartering headwind), point your thumb into the wind. When the wind is coming from behind, point your thumb away from the wind. So, for instance, if the wind is coming from the forward left (left quartering headwind), deflect the yoke to the left (thumb points left and into the wind); when coming from the left rear (quartering tailwind), deflect the yoke to the right (thumb points right and away from the wind).

To remember the elevator/stabilator inputs during a crosswind taxi, remember that when taxiing downwind (in the same direction as the wind is blowing), the elevator/stabilator should be down. When taxiing upwind, the elevator/stabilator should be neutral (for tricycle gear airplanes) or up (for tailwheel airplanes). Watch the movement of wind socks, flags, grass, etc., as you taxi, and change control inputs appropriately as your taxi direction changes.

Pay attention to what's going on outside the airplane while you taxi, and try not to be distracted by things inside the cockpit. This will also allow you to watch for airport signs and pavement markings that tell you where you are, where you're heading, and-most important-where the taxiway ends and the runway begins. This can be especially important if you are taxiing at a bigger airport with more than one runway and associated taxiways. If there is a control tower on the airport and you feel unsure about which way to go, you can ask for help by telling ground control that you would like progressive taxi instructions. The controller will watch your progress and tell you which way to go as you approach taxiway intersections and other areas of the airport surface.

Believe it or not, tower controllers and other pilots often gain an impression of how skilled and professional a pilot is by how he or she taxies and whether assistance is requested when needed. A pilot who weaves from one side to the other of the taxiway while being distracted by preflight cockpit items may even give the pilot following him or her on the taxiway the impression he is drunk. Listen to the sound of exasperation in a controller's voice when he has to redirect a lost pilot on the ground versus his helpfulness when directing a pilot who has requested progressive instructions, and it becomes obvious which situation the controller prefers.

Remember that taxiing is like everything else in flying: When you give the task the proper amount of attention and apply knowledge and common sense, you'll reap the benefits, and those around you will appreciate your professionalism and safety awareness.

Sue A. Critz is a flight and ground instructor and twice-appointed National Association of Flight Instructors Master Instructor based at El Paso International Airport in El Paso, Texas.

Want to know more? Links to additional resources about the topics discussed in this article are available at AOPA Flight Training Online (http://ft.aopa.org/links).


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