The start-of-APU EGT range is specified as which temperature range?

• A. 692C to 1038C
• B. 0C to 806C
• C. 807C to 1038C
• D. 1038C to 1100C

Answer: (A)

The start-of-APU EGT range is the temperature window the exhaust gas temperature should fall within during the APU start sequence. This window reflects a normal ignition and acceleration of the turbine: the temperature must rise quickly from a safe, but not excessive, level as fuel begins to burn, and it must stay under an overtemp limit as the APU comes up to speed. The acceptable start range of 692C to 1038C represents that initial ignition and safe acceleration zone. Temps surrounding this window—such as starting from near 0C, which is unreal for exhaust gas; or starting only from 807C to 1038C, which misses the lower bound; or starting at 1038C up to 1100C, which would imply operating at or above the limit—do not fit the expected start conditions.