MIL-HDBK-273, MILITARY HANDBOOK; SURVIVABILITY ENHANCEMENT, AIRCRAFT, NUCLEAR WEAPON THREAT, DESIGN AND EVALUATION GUIDELINES (30 DEC 1983)., This handbook is a reference document providing uniform design and evaluation guidelines for the survivability enhancement of aircraft Mission-Essential Weapons Systems (MEWS), within or for the Naval Air Systems Command, to ensure that effective combat operations are achieved when operating in a nuclear threat environment. Those elements and design activities that are related to survivability enhancement but are derived from the degradation of threat subsystem functions (e.g., electronic warfare) or from the ways that the aircraft can be utilized in a hostile environment (e.g., tactics) are not included. The evaluation guidelines, for the purpose of achieving systematic quantification and evaluation of combat survivability, include definition of mission scenario and associated threat environment, vulnerability to threat damage mechanisms, encounter survivability, and survivability enhancement trade-offs.