As far as I can tell, according to the Tech Manual there isn't, but just like the vehicle cards found on the MUL, Conventional fighters have a heat scale. Is this a mistake?
From Tech Manual page 193
Most aerospace units require heat sinks to dissipate the waste heat generated by their weapons, engines and other equipment. Aerospace fighters can push these heat sinks beyond tolerances, but conventional fi ghters, Small Craft and DropShips operate on a “zero-heat principle,” which means that these units have no Heat Scale during combat and cannot generate any heat in excess of their heat sink capacity.
I've also noticed that not a single Conventional Fighter has an Overheat Value of any kind.
Here's an example of a CF card from the Master Unit List
