Effectivity: 912 Series
Edition 1 / Rev. 0
d04054
page 49
May 01/2007
BRP-Rotax
INSTALLATION MANUAL
◆ NOTE: The basic requirement for safe operation is that boiling of
conventional coolant must be prevented. The boiling point of
conventional coolant is 120 °C (248 °F) with a 50/50 mixture
proportion and a system pressure of 1.2 bar (18 psi).
12.3) Coolant types
In principle, 2 different types of coolant are permitted.
Type 1:
- Conventional coolant based on ethylene glycol
Conventional coolant is recommended as it is commonly available and has a
greater thermal heat transfer capability. Its limitation is its lower boiling point.
Conventional coolant should be used with a mixture of 50 % concentrate and 50
% water.
◆ NOTE: Some conventional coolant is available pre-mixed by the
manufacturer. In this case do not mix with water, follow the
manufacturers instructions on the container.
Conventional coolant with a rate of 50% water cannot boil at a temperature below
120 °C (248 °F) at a pressure of 1.2 bar (18 psi). Thus, the coolant temperature
limit is at max. 120 °C (248 °F).
Permanent monitoring of coolant temperature and cylinder head temperature is
necessary.
Type 2:
- Waterless coolant based on propylene glycol
Waterless coolant is recommended if the design of the aircraft can not maintain
the coolant temperature limit. Waterless coolant has a very high boiling point that
prevents coolant loss due to „boiling over“ (vapor loss), but not to prevent
detonation, which can occur with cylinder head temperatures higher than 150 °C
(300 °F) (for ROTAX 912 UL/A/F) and 135 °C (275 °F) (for ROTAX 912 ULS/
S). It does not require pressure to maintain its boiling point. Due to a lower
thermal conductivity the engine temperature will typically run about 5-10 °C (41-
50 °F) higher with waterless coolant.
Permanent monitoring of cylinder head temperature is necessary.
Additional monitoring of the actual coolant temperature is possible but not
necessary for waterless coolant.
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