All aircraft have a whole bunch of probes connecting various parts of the aircraft engine to the cockpit. The probes (or sensors), pickup the information it is supposed to pickup and transmits it in real time to the cockpit where it is connected to the appropriate indicator or Aircraft Engine Data Management (EDM).

CRB probe and CHT gasket probes are two such probes. The Carburettor Temperature Probe (CRB) probe transmits carburettor temperature while the Cylinder Head Temperature (CHT) gasket probes transmits the cylinder head temperature to the appropriate indicator / EDM in the cockpits.

As you might guess, irrespective of the weather or temperature outside the aircraft, the engine and every other vital parts of the aircraft, has to function at a temperature that is conducive to its smooth functioning. Overheating can lead to fuel ignition and fire whereas, a drop in temperature can lead to the engine stalling and dying out in flight due to fuel starvation.

Every pilot therefore keeps a wary eye on the CRB and CHT indicators. If the cockpit sports an EDM than the pilot’s task is made simpler as the EDM can be pilot-programmed to raise and alarm in the event of any abnormalities in the CRB and CHT readings. The pilot is therefore free to pursue higher cognitive functions.

CRB probe explained:

Every carbon fuel powered engine has a carburettor usually mounted on top of the cylinder. Inside the carburettor is where the fuel-air mixture happens before it is pumped into the cylinder. The fuel-air mixture has to be precisely both in terms of fuel-to-air ratio and as to the temperature of the mixture. Any deviation will lead to serious consequences inside the cylinder and for the aircraft itself hence the need to monitor the carburettor temperature.

J.P. Instruments manufacturers CRB probes that are immune to humidity or presence of oil and gasoline. J.P.I CRB Probes are also engineered to withstand temperature fluctuations.

CHT probes explained:

Although there are three basic types of CHT probes, the one that we are concerned with, is the “J-type” CHT probe; also known as CHT gasket probe because it replaces the gasket on 18mm spark plugs.

You buy a CHT gasket probe if your aircraft engine does not have a threaded thermowell receptor. If you have difficulty adopting the CHT probe to your cylinder, you might want to look at the ‘CHT adapter probe’.

The CHT adapter probe is used in conjunction with the OEM CHT probe. The CHT adapter probe is a threaded probe that fits into the cylinder head thermo well and is available as a bayonet type or threaded type. So, you might want to take a look at the existing CHT probe and cylinder before buying the replacement CHT probe or CHT gasket probe.