In the early days of aviation, airports were open fields. Airplanes were small and light and with few passengers, there was no need for all-weather accommodations or operations. Airfields, as they were known, were maintained with frequent grass trimming and heavy rollers to smooth their surfaces. Ensuring the smoothness of a large field was and is a daunting task and the surface of these fields could be quite rough at times. This operating environment heavily influenced early airplane design.
If you were to pick up a picture book of early aviation, you might notice that the overwhelming majority of airplanes had two main wheels, typically built into the fuselage near the junction of the wing and a skid or wheel positioned under the tail of the machine. This design is known as "conventional gear" or more commonly as a "taildragger." A few early airplanes replaced the tailskid or tailwheel with a single wheel positioned at the front of the airplane, a design which came to be known as "tricycle gear." I will skip the physics explanation, but in a nutshell, it is much easier to design and build a tailwheel or tailskid to manage rough surfaces than it is to build a similarly robust tricycle gear. Even modern science and metallurgy have not altered these conclusions and most new "bush planes", which are designed to operate in undeveloped areas and rough fields, have conventional gear.
In the post-WWII aviation boom, airfields became airports and hard surface runways became the norm. Airplanes grew larger and tricycle landing gear became the design standard for modern airplanes in all but a few specialized areas including bushplanes and aerobatic mounts. In the air, taildraggers and tricycle gear airplanes fly pretty much the same. On the ground, though, they are two completely different animals. Enough so, that the FAA requires modern pilots to get specialized instruction and receive a "tailwheel endorsement" before soloing in a conventional gear aircraft.
Picture a tailwheel airplane for a moment. Imagine that there must be more weight behind the front wheels than in front of them, otherwise the airplane would topple forward and come to rest on its propeller. Now, imagine an arrow. In a traditional, stone tipped arrow, the vast majority of weight is in the arrowhead. If you were to take that arrow and find the center point along its shaft, the balance point would be well front of the measured center of the arrow. Now imagine shooting an arrow backwards, with the arrowhead facing rearward and the nock and feathers forward.. The arrow might fly for a while with the arrowhead trailing, but eventually, it would swap ends. Although there are more accurate scientific terms to describe the effect, I think of it as "mass leads."
Let's return to taildraggers. We've already established that there is more mass behind the front wheels than in front of them. Now imagine that same airplane, traveling forty or fifty miles an hour down a runway. During takeoff, with the engine at full power and the propeller clawing at the air to accelerate the machine, a pilot doesn't feel the mass difference. In landing configuration, with the engine idling and the airplane coasting in to land, this mass leading principle becomes more evident and commands that the pilot pay attention. Like our backwards arrow, the airplane wants to swap ends and have "mass lead." This event, known as a "ground loop" in pilot speak, can be dramatic and often results in bent wings, propellers and egos. Those of us who fly conventional landing gear airplanes say that there "are those who have and those who will." One of my mentors use to admonish me that the landing is finished when the "airplane is back in the hangar."
The most critical part of landing a taildragger is right after the machine touches down and it begins the transition from airplane to land vehicle. At that point, with the airplane close to flying speed, the airplane's control surfaces are still very effective and the airplane is flying down the runway almost as much as it is riding on its wheels. As land vehicles, taildraggers are pretty unstable, suffering from the scientific fact that mass "wants" to lead and that speed magnifies every control input. In aerobatic airplanes, which have relatively high landing speeds, this effect is very pronounced. Aerobatic pilots "dance" on the rudder pedals to keep the airplane heading straight down the runway. As an airplane slows, either because the pilot is braking or as a result of drag, the machine becomes less and less sensitive to control inputs and more forgiving of inattentiveness or clumsiness on the part of the pilot. By the time the airplane has decelerated to 20 mph or so, the transition to land vehicle has been largely accomplished and the rules that apply to its operation well understood.
If one chooses to live an examined life, then much like a pilot who chooses to fly a conventional gear aircraft, transitions will become a regular part of the life experience. One nice thing about flying is that as pilots, we know that the transition at landing is from aircraft to landcraft. With life transitions, the new steady state isn't always so obvious. I try to remember to stay focused and aware of the inputs and outputs and keep dancing on the rudder pedals until I have the machine put back safely in the hangar.
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