An integral part of a new engine certification process is the test verification of satisfactory operation in icing conditions. Icing conditions for this test, which is often conducted at sea level, need to meet or exceed conditions that would be experienced within the flight envelope. In order to assure this fact, manufacturers use analytical tools to conduct a critical point evaluation of engine over the range of flight operation for purposes of comparison to sea level testing. The recent concern for operating in ice crystals places new requirements on icing codes within the industry. One such code is used herein to describe these requirements and to illustrate the critical point evaluation procedure.