Rans S-12, Pilot Operating Handbook

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Chapter 6 - Powerplant Maintenance
Overview
As the reader might expect, this listing of maintenance is not comprehensive. Refer to records
kept in the engine logbook for additional practicle maintenance information. In most cases if
something requires periodic maintenance, the mechanic will make a meaningful entry in the
logbook reflecting what he/she has discovered.
Propeller
“Re-torque all bolts after first hour of operation and then after every 5 to 10 hours as part of
regular maintenance.” -Warp Drive Inc. Instructions
Torque 1/4” bolts to 125 inch-pounds (25 increment) using 7/16” wrenches and 5/16” bolts
to 175 inch pounds (25 increment) using 1/2” wrenches. Periodically check the track of the
blades after torquing the blades or hub bolts. The three blades should track well within 1/8” of
each other and if they don’t, then something is wrong. Should the prop need to be re-adjusted,
the most accurate method is to remove it from the airplane and place it on a perfectly flat table
to adjust the pitch of each blade. Do so in a scientific manner to avoid any possibility of mal-
adjustment. As well the prop should be inspected briefly prior to each flight to ensure it is in
good condition. Always turn off the ignition before rotating the prop by hand and also remem-
ber that just because the switch is off doesn’t meant the engine won’t start! Excessive debris
encountered during ground operations will cause nicks and gouges in the prop compromising
it’s integrity. At the first sign of trouble the prop should be sent to the factory for repair. If
known debris conditions will be routinely encountered, the protective leading edge tape should
be installed. Blade tip speed on this particular aircraft is approximately 500mph at 5800
engine RPM, 2.2727 reduction ratio to the propellor.
Engine Mount
Torque the 10mm bolts (TYP 4) using a 17mm wrench to 40 lb*ft. Check that the barry
mounts are tight using a 9/16” wrench. This maintenance should be done at least every 50
hours.
Engine
Most engine maintenance is done by reference to the ROTAX owners manual! Always check
the fluid levels and the quality of the fluids. Replace more often if desired, do not operate
the engine with too much or too little fluid or with damaged fluids (burnt oil, dirty antifreeze,
contaminated fuel, etc). The oil and oil filter should be changed every 100 hours by using the
drill motor operated pump. Warmup the motor so that indicated oil temperature is about 120F.
Remove the oil tank cap and dipstick and insert a small diameter tube to the bottom of the oil
tank thru the dipstick hole. Pump out all oil possible (approximately .66 gallons). Remove
the oil filter carefully avoiding any excessive spills by placing rags underneath and having the
necessary clean up items on hand. Not too much oil will come out but enough to make a mess
if you don’t plan ahead. Wipe a small amount of clean oil around the rubber gasket of the new
oil filter and install it to the engine without pre-filling it. Fill the oil tank to the midpoint of
the marked region on the dip stick. Be sure the ignition is turned off and slowly rotate the prop
5 to 10 revolutions to fill the oil filter and oil pump. Now start the engine and monitor the oil
pressure very closely. Shutdown the engine after 30 seconds or 1 minute and again check the
oil level in the sump tank, add more oil if necessary. Do not overfill, it only takes about .2 gal-
lons to go from low to high point on the dip stick.
This engine has been run-in with standard 10W-40 oil?? from 0.9 hours (new hobbs meter)
to 25.0 hours at which time the oil used is switched to Mobil1 synthetic. It is important to
remember that the Rotax 912 is not designed to run with aviation oil, with or without additives.
Aviation grade oils typically have special additives that are not intended to be used in gearbox
systems and the 912 UL has a common reservoir of oil for the engine and the gearbox. This
engine was designed to be used with automotive grade oils only.
Change the fuel filter every 100 hours. Turn off the fuel valve and be prepared to catch excess
fuel that runs out of the lines. Inspect the fuel filter to the extent possible to monitor signs of
fuel system trouble. It is a good idea to monitor the condition of the fuel tanks (debris floating
in the bottom) and to thoroughly inspect the fuel lines for cracks or other problems.
Throttle
The throttle friction block and mechanism in the cockpit should be inspected for proper opera-
tion before every flight. It is a simple matter to open the throttle and then return it to idle to
observe if one or both of the cables may be sticking. On the 15 hour interval of airframe lubri-
cation, the red plastic block should be lubricated and the throttle should be operated several
times to ensure exact operation of the cable system. Likewise the choke (starting carburetor)
should be inspected at the same time. Every 100 hours, the throttle and choke cables should
be re-adjusted as well as the idle stop screws, if necessary, to synchronize the throttle opening.
This is done with a dual vacuum gage setup attached to the intake manifold ports on each car-
buretor; it is necessary to completely remove the intake manifold cross tube for this test.
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