Electronics International US-8A - Manual (Page 15)

Operating Information
pilot of an over-temperature condition. This is an important feature for turbo-charged aircraft since turbine
inlet temperatures can easily creep above limit after a change in power or mixture settings.
Another advantage of the Ultimate Analyzer over conventional gauges is its extreme accuracy and linearity.
This assures you of accurate TIT readings.
Turbine housing life is also affected by sudden changes in temperature. Thermal shock can occur during
abrupt changes in the mixture or power settings. Make gentle changes in the mixture and power settings
when transitioning from a higher TIT to a lower temperature. The Ultimate Analyzer’s 1’F resolution will
help in assuring that the proper transitioning of the TIT is taking place.
A) Selecting the High TIT Limit: At 75% power, lean your engine to peak TIT. Allow the TIT
temperature to stabilize. Set your High TIT Limit for 40’F above this temperature. Do not exceed the
maximum limit allowed for your aircraft. For most aircraft this limit will be 1650’F.
B) Selecting the Lower TIT Limit: Set your aircraft up in a normal low cruise power condition.
Adjust the mixture full rich and wait for the TIT to stabilize. Program the Lower TIT Limit 40’F below
this temperature.
3. CHT’s:
The Ultimate Analyzer helps you protect your engine against the threat of excessive heat. Most general
aviation aircraft take the CHT off the hottest cylinder determined by extensive flight tests. 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 complex 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 head temperatures 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, burned 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. The Ultimate Analyzer will automati-
cally detect a Shock-Cooling condition in the normal mode of operation for the cylinder being displayed.
When it detects a CHT descending too rapidly the red light over the CHT display will blink.
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, OAT or airspeed will affect the CHT and the rate at which it will change. Since rate
and trend information can be interpreted easily on the Ultimate Analyzer’s digital display, changing any one
of these parameters to stabilize, slow or reduce the CHT is possible with almost immediate results.
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Selecting the Proper Limits