Defense rotary-wing aircraft must have helicopter engines because they supply the strength and dependability needed for a variety of military activities. Military rotary-wing aircraft’s operating capability and effectiveness depend heavily on their defense helicopter engines. These engines power the rotor systems of the helicopters, allowing them to perform a variety of tasks such as transport, reconnaissance, combat, search and rescue, and anti-submarine warfare. Military rotary-wing aircraft’s operational success in a variety of duties depends heavily on their defense helicopter engines. To ensure that these engines remain functional, performance, emissions, and maintenance issues must be addressed.