The challenges faced during starting of an aircraft gas turbine engine using a Jet Fuel Starter (JFS) at high altitude airbase are discussed in this paper. Autonomous ground starts at high altitude airbase in soaked sub-zero temperature condition without any external ground support assistance is a challenge. Generally, the start cycle (sub-idle speed) at sub-zero temperatures of a gas turbine engine at high altitudes is influenced by several factors. Drag loads are estimated due to change in lube oil viscosity of engine gearbox and accessory gear box that affects available torque margin of a starter. These estimated loads are superimposed on starter characteristics to identify the available margins for successful starts. The cold start is particularly severe, since it increases the tip clearance between rotor and casing of the engine due to difference in its thermal growth. Higher tip clearances significantly degrade compressor surge margin and results in rotating stall. Inconsistent engine starts were resolved by adopting alternative methods without any change in hardware. This paper presents set of methods used to overcome inconsistent engine starts at high altitude cold weather conditions.

Evaluation of engine performance during armament firing in fighter aircraft is a vital qualification aspect for airframe engine integration. Ingestion of missile’s efflux into air intake results in rapid increase of engine inlet temperatures (temperature ramps) which cause flow disturbance to the compressor. Temperature distortion caused due to armament firing and its effect on compressor stability during flight testing is evaluated. Accordingly mitigation actions are recommended for stall/surge free operations. Distortion descriptors are assessed using simulation model (engine performance program) and results compared with engine distortion limits.