This ARP is intended to cover the detail installation requirements and the temperature response characteristics of various types of temperature responsive elements intended for well type installation in air-cooled aircraft engine cylinder heads. Provisions of the well for installation of the parts shall be made by the engine manufacturer in such a location as to give characteristic temperature response for indication and control of engine cylinder temperature. The details of this ARP may also be applied to temperature measuring applications other than air-cooled aircraft engine cylinder heads.