Cylinder head temperature of aircraft engine?

Answer 1

CYLINDER HEAD TEMPERATURE

The engine temperature can have a dramatic: impact

on engine performance. Therefore, most reciprocat-

ing engine powered aircraft are equipped with a

cylinder head temperature (CHT) gauge that allows a

pilot to monitor engine temperatures.

Most cylinder head temperature gauges are gal-

vanometer-type meters that display temperatures in

degrees Fahrenheit. If you recall from your study of

electricity, a galvanometer measures the amount of

electrical current produced by a thermocouple. A

thermocouple is a circuit consisting of two dissimi-

lar metal wires connected together at two junctions

to form a loop. Anytime a temperature difference

exists between the two junctions, a small electrical

current is generated that is proportional to the tem-

perature difference and measurable by the gal-

vanometer. Typical dissimilar metal combinations

used are iron and constantan. or chromel and

alumel. Since a thermocouple generates its own

electrical current, it is capable of operating indepen-

dent of aircraft power.

The two junctions of a thermocouple circuit are

commonly referred to as a hot junction and a cold

junction. The hot junction is installed in the cylin-

der head in one of two ways; the two dissimilar

wires may be joined inside a bayonet probe which is

then inserted into a special well in the top or rear of

the hottest cylinder, or the wires may be imbedded

in a special copper spark plug gasket. The cold junc-

tion. or reference junction, on the other hand, is typ-

ically located in the instrument case.