Remote-Control Model Planes Combine art and Engineering in Miniature Versions of The Real Thing
From the Print Edition:
Pierce Brosnan, Nov/Dec 97
(continued from page 2)
Today's radio control equipment offer practically unlimited flexibility. While the basic components of the systems have not changed much since the 1970s, the available whistles and bells have evolved dramatically. The function of a modern R/C system is really quite simple. The transmitter sends signals to an airborne receiver that controls servo motors that, in turn, operate the flying surface and engine controls. A small, aircraft-mounted rechargeable battery pack provides at least an hour of flying time. The pilot holds a small transmitter, which usually has two joysticks. In the most common design, moving the right stick forward and backward controls the movement of the elevator, which regulates the up and down pitch of the aircraft. Moving the same stick side to side controls the roll of the aircraft via the wing-tip mounted ailerons. The further you move the stick, the further the aircraft's control surfaces are deflected and the quicker the aircraft performs that particular movement. The left stick controls the throttle and the left and right movements of the rudder, which controls the "yaw" of the aircraft, moving the nose to one side or the other. Additional switches and levers can control the operation of retractable landing gear, landing flaps, payload dropping mechanisms or whatever functions a creative modeler might dream up. It sounds pretty simple, and it is, once you get the feel for flying: move the sticks the proper amount in the correct direction at the right time and you're flying. Move them in the wrong combination, in the wrong direction, at the improper time and you crash.
Crashes do happen, even at high levels of piloting proficiency. This year, even the polo ground's clubhouse claimed a victim, a British-designed Hawker Seafury, which spun into the roof. The sound of the sickening, inevitable "smack" from the impact is delayed--like thunder following a distant lightning strike--for a moment after you see the pieces start to fly. The pond at the downwind end of the field claimed a couple models as well, as pilots occasionally found themselves with a dead engine and not enough speed to make it back. The almost instinctual reflex--to try to stretch the model back to the safety of the manicured grass field--combined with a relentless and stiff crosswind spells disaster.
One of these accidental seaplanes was Eddie Newman's KI-61 "Tony," a Second World War Japanese fighter replica. Tony, a product of many hundreds of hours of work, lay broken in half just aft of the cockpit--its left wing partially missing--as it was unceremoniously carted past in the back of a maintenance cart. Experienced modelers are all too aware that sometimes if you fly 'em, you break 'em. Fortunately, disaster caused by equipment failure is not all that common anymore. Due to the greatly improved level of control and reliability of modern equipment, more complex and larger models are practical now--even common.
Powering a 50-pound aircraft (there are four of them in the competition) requires some serious horsepower. Through the 1980s and early 1990s, engine development kept pace with electronics progress. It wasn't always that way, however. Through the 1970s, most models were usually limited to .60-cubic-inch, two-stroke engines, with an output of around one horsepower, that could only propel models with a six-foot or less wingspan. In the scale modeling world at that time, most replicas were usually no larger than one eighth the size of the original, in comparison to today's models, of which many are 1:6 to 1:3 scale designs. Three models at this year's Top Gun have wingspans of 12 feet.
As miniature model aircraft engines evolved from gasoline- and oil-fired spark-ignition (with a coil, condenser, batteries and spark plug) through the original two-stroke castor oil and nitromethane fuel-burning forebears of today, the sophistication (and size) of the models that can be successfully flown has changed.
Modern engines offer not only exemplary power-to-weight ratios, but an exciting selection of designs. Simple two-stroke, .40- and .60-cubic-inch engines make up the bulk of the power plants (though they can be built as small as .010 cubic inches), including the types used in most trainers designed for beginning pilots. Competition events such as Top Gun have some of these simple, low-cost engines, though most modelers are using sizes and designs that were not available 20 years ago. Synthetic oil- and nitromethane-based four-stroke designs and large, gasoline-fueled electronic spark-ignition motors are the favorite choices. Developments have even led to mass-produced, four-stroke radial engines with five, seven and nine operating cylinders, which allow competitors such as Charlie Nelson (known as "Mr. Waco" to his friends) to power his gorgeous red Waco VKS 7F biplane with a seven-cylinder engine, similar in operation to the full-scale motor. These engines are complete even down to the functioning rocker arms and adjustable valve gear. Just bring along a couple thousand dollars and take one home.
Today, "turbine" is the hot word in power plant development. The technology, which started to appear in the 1990s, has enabled modelers to build miniature, functioning jet turbine engines. This year, four pilots chose to compete with model aircraft based on these power plants, and several more were flown in demonstration fights. These marvels of engineering and fabrication function just as the real thing and are fueled by either propane or kerosene. Twenty years ago, when modelers first started duplicating jet aircraft with any level of realism, they did it with ducted fan technology. Those models commonly used standard, high-performance engines designed for model aircraft racing, located inside a shroud (or duct), driving a multiblade impeller at very high rpm (compared to propeller speed).
Bob Violett, a fighter pilot during the Vietnam War, is one of the pioneering modelers in ducted fan technology and he has developed many refinements to the basic concept. He is also a big player in the turbine field today, and his performance at Top Gun shows why. Despite the intermittent south Florida rain showers, even experienced modelers stopped in their tracks to watch, and especially to listen, as Violett and Jerry Caudle started Caudle's turbine-powered TV-1.
Ah, that sound.
That wonderful hushed whining is punctuated only by an initial high-speed "zip" as compressed air from a pit-side cylinder starts the turbine's fan blades spinning. As the electronics are powered up and the pressurized fuel injection starts, the engine literally lights to life. A small puff of smoke signals the startup, and the unmistakable sound, similar to a large welding torch, is clearly audible. Far from loud, the sound is almost pleasant.
You must be logged in to post a comment.