Rans S-12, Pilot Operating Handbook

Page: 6 / 35

check, return the throttle to idle. Each of the 4 cylinders in the engine has 2 spark plugs. One
ignition circuit controls one spark plug in each cylinder. Two ignition systems increase the
efficiency of the combustion (as evidenced by an RPM drop when you turn off one ignition
switch) and secondarily provide a redundancy feature that if one circuit should fail, there is a
second system to provide adequate power to land the airplane.
Using the Parking Brake Valve
The parking brake valve, if closed while the brakes are held on, will maintain better stop-
ping power than using the brakes alone. This is because most of the hydraulic energy lost in
this particular brake system is due to the flexure of the plastic brake line. While holding the
brakes on hard, switch the valve to the closed position and release the brakes with your feet.
Now the length of brake line holding hydraulic pressure is cut approximately in half, increas-
ing stopping power. This technique should be employed for short field takeoffs and landings
where stopping power is critical. It is also recommended for run-up procedure when checking
magneto operation (the engine generates an enormous amount of thrust at mag-check RPM
of 3750). Although when the valve is closed, it does allow you to apply brakes, it is recom-
mended to hold the brakes on, then close the valve. Due to the ease with which the parking
brake valve can be closed and open, it must remain an item on all checklists. It is not wise to
takeoff or land when the valve is closed. When taxiing, use the brakes as little as possible and
avoid using them lightly for extended periods, it is better to brake hard for a short period than
to ride them lightly. If the situation ever becomes critical, cut the engine power and as soon as
the aircraft is slow enough, put the airplane off the runway on the grass, there the rolling resis-
tance is greatly increased.
High Wind Taxi Methods
Taxiing in high winds and operating on the runway with high crosswinds is no laughing mat-
ter. This is a very light aircraft and can be quite easily tipped over of thrown about by wind.
Taxi with the utmost care in control orientation and always fly with authority and decisiveness
when in high crosswinds. Once the airplane starts to tip over there is little you can do to stop
it. If necessary, treat low wind or no wind days like high wind days. If you create the habit of
continuously correcting for wind on the ground, you will likely be much safer when the winds
do come. Take the time to create a chart for yourself showing control orientation for each type
of cross wind (quartering from the front, quartering from the rear, head on, tail wind, direct
crosswind). Remember that wind blowing backwards across the control surfaces (quartering
tailwind) causes them to work in reverse of what they normally do.
Take-Off Overview
For take-off it is important for you to remember a few things. First of all, if you loose
power in a high angle climb with full flaps or even 2 notches of flaps, you will have to
IMMEDIATELY put in a large amount of nose down control inputs to maintain airspeed. It
is easy to hesitate for a second or two and in this time your airplane can go from 70mph to
30mph. Second of all, you should treat the nose gear gently. Use a generous amount of eleva-
tor control to get the weight off the nosewheel as soon as possible, this also keeps the wheel
from spinning any faster than necessary and minimizes vibration. The nose will come off the
ground at 35mph with full throttle; with the throttle at idle, it is possible to hold the nose up at
25 to 30mph. This also keeps the rotational speed down for the large front wheel which is not
in perfect balance. In high crosswind operations, you may have to compromise a bit and keep
some weight on the nose for steering until you attain enough airspeed to keep the plane aligned
with the runway.
Take-Off Procedure
Be sure your take-off checklist is complete, add power smoothly and hold a large amount of
back stick until you feel the nosewheel come off the ground. Keep reducing back pressure as
the airspeed increases so that the nosewheel remains 4-5 inches off the ground. If you keep
the nosewheel off the ground you will be able to easily feel when the plane is ready to fly. Be
careful not to pull up too hard and scrape the tail skid on the ground. Climb the first 50 or 100
feet at 65mph unless you need to clear an obstacle, in which case use the best angle of climb
speed. After reaching 150 feet, ease out the flaps (if used) and continue the climb to your
cruise altitude. Always observe the maximum flap extension speed on takeoff and landing.
If the flap lever is difficult to pull, it is because there is too much wind pressure on the flaps.
Push the nose over and reduce the throttle to cruise. When adjusting the power setting, do so
in a slow and even manner. If you treat the engine with respect, it will respond when you ask
it to. However if you rev the motor recklessly with rapid and erratic power settings, it will
likely develop abnormal wear qualities.
Just As You Leave the Ground
As soon as you are off the ground, tap the brakes and stop the mains from spinning, you may
notice a considerable amount of shaking if they are spinning fast. Liftoff speed at gross weight
and two notches of flaps is approximately 40mph indicated airspeed. Continue your climb at
Vx or Vy as required.
Engine/Throttle Usage
The airplane can be held in a climb attitude at full power setting for as long as 5 minutes.
After this period of time you should allow for a short rest period or reduce the power of
your climb. The engine is not meant to run at full power indefinitely. Also, if you are in a
prolonged decent it is wise to periodically add power for a few seconds to clear the motor
of excessive fuel build-up and provide a chance for increased circulation of fluids. Be par-
ticularly careful after idling the engine for a minute or so on final approach and then adding
power for a go-around, give the engine a moment to respond to the first 1/4” of throttle input.
Another important aspect of the aircraft is it’s excess power. With the exception of steep
climbs, no matter what attitude the airplane is in, it is possible to quickly exceed 75mph. The
throttle in this aircraft becomes just as important as any of the other controls when maneuver-
ing and typically the airplane responds very rapidly to throttle inputs.
Cowl Flaps
This airplane does not have cowl flaps but there is something to be said on this subject. After
the initial flight test period and when the weather turned cold, the typical in flight engine
parameters started running too low. This is because of the highly effective radiator and the
exposed mounting configuration of the engine. If the aircraft is operated in cold weather, the
radiator inlet should be blocked either partially or completely. A completely blocked radia-
tor inlet in operational weather of 30 degrees F will yield engine temperatures that are on the
verge of too cool. If you discover the engine running too cool (out of the green) in flight,
descend to a lower altitude and continue to the nearest point where you can land to cover up
the inlet to the radiator. Running the engine at low temperatures is not healthy.
Rudder Usage
The rudder is trimmed for most normal flight conditions, however in a low airspeed high
power setting configuration, the aircraft will require a little more right rudder pressure. In
PAGE 6