Installation & Operation Manual
O-360 and IO-360 Series Engines
© March 2004 Superior Air Parts Inc. Chapter 6 • Normal Operating Procedures
10
G. Use of Carburetor Heat Control
(1.) Under certain damp atmospheric conditions
and temperatures of 20°F to 100°F it is possible
for ice to form in the induction system. A loss of
power is reflected by a drop in manifold pressure
in installations equipped with constant speed
propellers or a drop in RPM in installations with
fixed pitch propellers. The engine may stop if
not corrected. To avoid this, carbureted
installations are equipped with a system for
preheating the incoming air supply.
(2.) Ground Operation - Use of the carburetor air
heat on the ground must be held to an absolute
minimum and only to verify it is functioning
properly. On many preheated installations, the
heated air does not pass through the air filter.
(3.) Take-Off - All take-off and full throttle
operations should be made with carburetor heat
in the "Cold" or "Off" position.
(4.) Climbing - When climbing at throttle power
settings of 75% or above, the carburetor heat
control should be set in the "Cold" or "Off"
position. If carburetor heat is necessary, it may
produce an over-rich air mixture. When this
occurs, lean the mixture with the mixture control
enough to produce smooth engine operation.
(5.) Cruise Flight - During normal cruise flight,
leave the carburetor air heat control in the "Cold"
position.
(7.) If the presence of carburetor ice is noted,
apply full carburetor air heat and open the
throttle to limiting manifold pressure and/or
RPM. A slight additional drop in manifold
pressure, which is normal, will be noted. This
will be restored as the ice is melted. The
carburetor heat control should then be returned
to the "Cold" or "Off" position.
(8.) If equipped with a carburetor air temperature
gage, partial heat may be used to keep the
mixture temperature above freezing. Constant
high temperatures are to be avoided because of
a loss in power and variation of mixture. High
intake air temperatures also favor detonation
and pre-ignition, both of which are to be avoided
if normal service life is to be expected from the
engine.
CAUTION: USE CAUTION WHEN OPERATING
WITH PARTIAL CARBURETOR HEAT ON
AIRCRAFT THAT DO NOT HAVE A
CARBURETOR AIR TEMPERATURE GAGE.
IT IS RECOMMENDED TO USE EITHER FULL
HEAT OR NO HEAT IN AIRCRAFT THAT ARE
NOT SO EQUIPPED.
(9.) Approach and Landing
Note: During a landing approach, the
carburetor heat should normally be in the
"Hot" or "Full On" position.
If full power is required under these
conditions, as for an aborted landing, the
carburetor heat should be returned to the
"Cold" or "Off” position as full power is
applied. Under certain hot and dry ambient
conditions, carburetor heat may not be
required. See the aircraft flight manual for
specific instructions.
