2. Air cooling (outer) system, consisting of:
-air intake port;
-bafflers;
-air hatch;
-control devices;
7.2.2. Description and operation
The ROTAX 912 S engine cooling system ensures the fluid cooling of cylinder heads and the air cooling of cylinders. The cylinder head cooling system is a closed circuit including a cooler, an expansion tank, and an overflow tank. A water pump actuated by camshaft forces the coolant to flow from cooler to cylinder heads, expansion tank, and then back to cooler. The expansion tank is closed by a cover pressurized by an overpressure valve and by a return valve. As the coolant temperature increases, the overpressure valve opens and the coolant flows through a flexible pipe into the overflow tank. When the coolant temperature drops, the coolant is sucked back into the circuit. Coolant temperatures are not read directly. They are measured by temperature probes installed inside the heads of cylinders 2 and 3. The coolant level is checked in the overflow tank. This level should always remain between the minimum and maximum level marks. The water cooler is located in
S.C. AEROSTAR S.A.
FESTIVAL R40S
BACAU - ROMANIA
AIRPLANE MAINTENANCE MANUAL
forward position, on the lower side of the cowling. The overflow tank lies on the top area of the firewall, port side, with access to its filling cap through the same cover in the cowling as for the oil tank. Air-cooling of cylinders completes the water-cooling of the cylinder heads. The cooling air enters the cylinders through an intake port on the front area of the cowling, and guided toward the cylinders through a baffler system mounted on the engine. To adjust the cooling airflow, a door was made in the lower side of the cowling, the opening of which can be controlled from the cockpit. Additional airflow is ensured to the engine fuel pump by an air intake port, located on the front side of the cowling. The connection pipes of the cooling system are made of aluminum alloy pipe, joint to the system inlets by means of rubber sleeves and collars.
7.2.3. Maintenance and repair of engine cooling system
Level of certification needed: A&P Mechanic
Check the coolant fluid level in the expansion tank on every flight day, to make sure that it does not exceed 2/3 of expansion tank volume. The fluid level in the overflow tank should remain between the maximum and minimum markings.
Check the cooling pipe sleeves for any damages, leakage, hardening due to heating, porosity, or loose tightening. Pay special attention to the sleeve areas to be mounted on fittings and under collars.
Inspect the expansion tank for any damages or anomalies. Check the tank bottom fastening on the rubber plate.
Check the overflow tank for damages or anomalies. Check the condition of the link pipe between the expansion and the overflow tanks.
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