Current testing requirements for high temperature alloys are defined in general industry specifications (ASTM, AMS), as well as in user specifications. Many of these requirements were established in the 1960's when production practices were yet to be refined.
cowling - protective covering consisting of a metal part that covers the engine; there are powerful engines under the hoods of new cars; the mechanic removed the cowling in order to repair the plane's engine.
What is an external combustion engine? An external combustion engine is one in which the oxidation of the  fuel occurs outside the engine, which provides heat to the motive  portion of the engine. External combusâ¦tion is characterized by  burning the fuel outside of the moving parts, as opposed to burning  fuel inside the cylinders of an internal combustion engine.