CHT & EGT gauges

[joshfly97]

Hey Guys

I just recently did my CASA PPL theory exam and cannot find the answer to one of the questions I got wrong anywhere. The question asked whether the CHT or EGT gauge would take longer to recognise a difference in temperature.
Thanks for your help :8

[Mark 1]

A CHT gauge is measuring the metal temperature near the outside of the cylinder head so any sudden heating event like detonation would take several seconds to register on the thermocouple as the heat conducts from inside to outside.

EGT gauges are in direct contact with the hot gases so changes are seen almost instantaneously.

[Old Fella]

Just to expand a little. The CHT sensor which is subjected to changes in OAT as well as combustion temperature changes can, with increased altitude which generally means a decrease in OAT, sometimes not reflect what is actually happening within the combustion chambers. EGT sensors, being directly in the exhaust gas stream, sense any change in combustion chamber temperature much quicker and more accurately than a CHT system will.