Effectivity: 914 Series
Edition 2 / Rev. 0
d04277
page 45
July 01/2008
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 (17.5 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 (17.5 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 135 °C (275 °F). 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 required.
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