Control Line Type Flying Aircraft
Also referred to as U-Control in the USA, introduced
by the Stanzel brothers in Texas during early 1940. It was pioneered and popularized
by the late Jim Walker who often, for show, flew three models at a time. Normally
the model is flown in a circle and controlled by a pilot in the center holding
a handle connected to two thin steel wires. The wires connect through the
inboard wing tip of the plane to a mechanism that translates the handle movement
to the aircraft elevator, allowing maneuvers to be performed along the aircraft
pitch axis. The pilot will turn to follow the model going round, the convention
being counter-clockwise.
Line tension is maintained by centrifugal force and by
the flight characteristics of the model. The air drag of the lines tends to
yaw the model toward the inside hindering line tension. To increase line tension,
models may be built or adjusted in various ways. Rudder offset and thrust
vectoring (tilting the engine toward the outside) yaw the model outward. Weight
on the outside wing, an inside wing that is longer or has more lift than the
outside wing (or even no outside wing at all) and the torque of a left rotating
propeller (or flying clockwise) tend to roll the model toward the outside.
Anhedral (wings sloping downward to the outside) improves resistance to cross
winds, as with the Wright Flyer. Sweep forward has a similar effect. Wing
tip weights, propeller torque, and thrust vectoring are more effective when
the model is going slowly, while rudder offset and other aerodynamic effects
have more influence on a fast moving model.
Since its introduction, control line flying has developed
into a competition sport. There are four contest categories for control line
models: Speed, Aerobatics, Team Racing and Combat.
The international rules are defined by the Fédération
Aéronautique Internationale (FAI). World and Continental (presently
only European) Championships are held with semiannual interleaving. The World
Championships were held in Sweden in July 1996. In 2004 they took place in
Muncie, IN, USA, and in 2006 in Spain. In addition to the international categories
there are also national variants. The international rules are available from
FAI.
Speed
Aerobatics
Team Race
The international class is F2C. A pilot and a mechanic
compete as a team to fly small (370 grams)(13 oz.) 65 cm (25 in.) wingspan
semi-scale racing models over a tarmac or concrete surface. Lines are 15.92
meters long (52.231 ft).
Three pilots, plus mechanic teams, compete simultaneously
in the same circle, and the object is to finish the determined course as fast
as possible. Tank size is limited to 7 cc, thus 2-3 pitstops for refueling
are needed during the race.
The mechanic stands at a pit area outside the marked
flight circle. The engine will be started and the model released at the start
signal. For refuelling, the pilot will operate a fuel shutoff by a quick down
elevator movement after the planned number of laps so that the model can approach
the mechanic at optimum speed, around 50 km/h (30 mph). The mechanic will
catch the model by the wing, fill the tank from a pressurized can by a hose
and finger valve, then restart the engine by hitting the carbon fiber/epoxy
resin propeller with his finger. Ground time of a good pitstop is less than
three seconds.
The race course is 10 km, corresponding to 100 laps.
Flying speeds are around 200 km/h (125 mph), which means that the pilots have
to turn one lap in 1.8 seconds. Line pull due to centrifugal force is 85 N
(17 lb) (19 g:s). A faster model will overtake by the pilot steering it above
the slower one while he moves his handle with lines over the opponent pilot's
head.
After two rounds of elimination heats, the 6, 9 or 12
fastest teams enter two semifinal rounds, and the three fastest teams in the
semifinals go to the final, which is run over the double course.
Maximum engine size is 2.5 cc (.15 cu.in.). Diesel, i.e.
compression ignition engines are used. They are single cylinder two-stroke,
designed for this purpose. At the world championship level it is not uncommon
that the competitors design and build their own engines. Their output power
is approaching .8 horsepower at 25,000 rpm.
Suppliers
Flying model suppliers include Guillows, for the most
basic "dime store" models, built of the same materials and on the
same principles as their advanced types, and Cox for ready to fly control
line internal combustion models and for internal combustion engines in the
very smallest sizes, and now for electric powered radio control.
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