Electronics International TC-1P - Manual (Page 11)

8
CHT's Operating Information
A. The Large Digital Display gives you a fast and very accurate indication of your current temperature
condition. This unit will display temperatures from ambient to 1999‘F in 1‘F increments. This also
allows you to interpret rate and trend information at a glance.
B. This unit incorporates an Over-Temp Warning Light. This light will come on any time the CHT is
above the Maximum Operating Temperature Limit indicated on the front of this unit. This light has the
advantage of catching your attention without having to scan or interpret the display.
C. This unit also comes with an External Warning Control Line. This line can be connected to an
external light in a control panel or mounted in front of the pilot. This control line will turn on the
external light any time the CHT exceeds the Maximum Operating Temperature Limit indicated on the
front of this unit.
2. Cautionary Temperature Range (Yellow Line):
Although operating your engine in this temperature range is approved, prolonged operation may cause
excessive engine wear. The Cautionary Temperature Range extends from the “CAUTION” to “MAX.
LIMIT” indicated on the front of this instrument.
3. CHT Operation:
The Cylinder Head Temperature (CHT) instrument helps the pilot protect his engine against the threat of
excessive heat. Most general aviation aircraft monitor the hottest CHT as determined by extensive flight
tests done by the airframe manufacture. Minimum in-flight CHT should be 150‘F, and maximum in most
direct drive normally aspirated Avco Lycoming engines is 500‘F. Some of the higher powered, more com-
plex engines have a limit of 475‘F. Although these are minimum and maximum limits, the pilot should
operate the engine at more reasonable temperatures in order to achieve the expected overhaul life of the
powerplant. It would be normal during all-year operations in climb and cruise to see cylinder head tempera-
tures in the range of 350‘F to 435‘F.
Sudden cooling of the CHT (known as shock cooling) is a problem that is common with aircraft engines.
This is caused by fast descents with little or no power and rich mixtures. This may result in bent pushrods
due to exhaust valves sticking, burnt valves, spark plug fouling, broken piston rings, cracked cylinders at the
spark plug and valve ports and warped exhaust valves. To avoid these problems, do not allow the CHT to
cool more rapidly than 1‘F every 3 seconds during in-flight operation. This can be easily detected with our
1‘F digital display.
During climbs, the cylinder head temperatures will rise rapidly until the heat absorbed by the combustion
walls is dissipated out the engine’s cooling fins. At this point, the CHT will stabilize. Any change in
throttle, mixture, cowl or airspeed will affect the CHT and the rate at which it will change. Since rate and
trend information can be easily interpreted from our digital display, changing any one of these parameters to
stabilize, slow or reduce the CHT is possible with almost immediate results. Our digital instrument takes the
guesswork out of controlling your CHT.