What is the maximum temperature allowed for APU start?

The maximum temperature allowed for APU start is -54 °C. This limit is critical because it ensures the APU (Auxiliary Power Unit) can operate correctly without risk of damage or failure due to extreme cold conditions. APU systems are sensitive to temperature fluctuations, and starting an APU at temperatures above its prescribed limit can compromise its performance and longevity.

Understanding the operational parameters of the APU, particularly temperature limits, is essential for maintaining the reliability and safety of the aircraft. Operating outside these specified limits can lead to inefficient starting, potential mechanical failures, and overall operational disruptions, which could negatively impact flight schedules and safety.

Other options presented are simply outside the established operational envelope for the APU, making -54 °C the only viable choice for maximum temperature during start.