What is the maximum temperature for APU start?

The maximum temperature for APU start is set at ISA +35°C. This limit is in place to ensure the safe operation of the Auxiliary Power Unit (APU) and to prevent overheating or potential damage to the unit during the starting process. The APU has specific operational parameters that must be adhered to in order to maintain reliability and efficiency, as exceeding the maximum temperature can lead to malfunction or reduced performance.

In operational practice, guidelines like these are established based on extensive testing and assessment of the APU systems in various environmental conditions. Following them helps ensure the aircraft can operate safely and effectively during different phases of flight, especially in warm weather conditions. Adhering to the prescribed maximum temperature limit is crucial for pilots and crew to ensure that the APU performs optimally.