For Your Safe Flight Page 23
Section 4 - Diagnosing Engine Problems
Typical Normal Parameters
The follow chart lists typical normal parameter values that you will
observe for most general aircraft engines.
Parameter Normal range Comments
EGTs in Cruise 1350°F
1550°F
• under 200 HP
• high performance
• EGT should drop 200°F
when full throttle is
applied
EGT span (DIF) 70 to 90°F
120 to 150°F
• fuel injected
• carbureted
TIT 1600°F average
• 100° higher than EGT
CHTs 350°F (OAT 60°F)
410°F
• normally aspirated
• Turbocharged
CHT span 50 to 70°F
OIL 200°F
• oil cooler thermostat
opens at 180°F
Shock cooling* -40°/minute
-55°/minute
-200°/minute
• tightly cowled
• Bonanza
• helicopter
* Maintain a cooling rate of less than -60°/minute. You will find that the
cylinder with the greatest shock cooling will shift from front cylinders
(during climb out) to the rear cylinders (during descent ).
If one CHT is reading 20° to 50° above or below the others, this may be
due to that cylinder having a spark plug gasket probe instead of a
bayonet probe. This is necessary because the aircraft’s factory original
CHT probe is occupying the socket in the cylinder head rather than the
EDM. This is normal. If the discrepancy is greater, be sure the spark plug
gasket probe is mounted on the top spark plug. An adapter probe is
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