Presented are the comprehensive results of research testing accomplished with the Pilot Test Unit (PTU) at AEDC since February 1969. The major objective of this continuing test program is to develop operational techniques and suitable ceramic materials in direct support of a full-scale, intermittent airflow, high enthalpy, high pressure test facility capable of testing aircraft and missile models, components, and engines in the Mach 2 to 8 flight regime. Eighty-four blowdown runs accomplished in the PTU are reported herein. Heater maximum operating conditions of 1850 psi and 4450F were accomplished during testing.