Calculations of aircraft contrail formation critical temperatures

Forecasts of condensation trail (contrail) formation are an extremely important consideration in military aircraft operations, particularly in the operation of stealth aircraft. Some recently published works have claimed improvements in the time-tested forecast technique of H. Appleman, but the results are called into question by errors in the basic physics. This note provides a brief explanation of contrail formation theory and presents a simple derivation of the critical temperature of contrail formation for representative jet engine types.