What is the APU start temperature range (min - max)?

What is the APU start temperature range (min - max)?

• A. -60°C - ISA +25
• B. -54°C - ISA +35
• C. -50°C - ISA +30
• D. -45°C - ISA +20

Answer: (B)

The APU start temperature range is the ambient temperature window in which the APU can be started safely. The minimum is set at -54°C to ensure fuel atomization, lubrication viscosity, and the starter system can operate reliably in cold weather; below this, starting the APU becomes unreliable or could cause damage. The maximum is ISA + 35°C to prevent overheating and to keep the APU within its thermal and component limits during start in hot conditions. This combination—minus 54 degrees Celsius up to ISA plus 35—is the standard Embraer specification, and it matches the given correct answer.

The APU start temperature range is the ambient temperature window in which the APU can be started safely. The minimum is set at -54°C to ensure fuel atomization, lubrication viscosity, and the starter system can operate reliably in cold weather; below this, starting the APU becomes unreliable or could cause damage. The maximum is ISA + 35°C to prevent overheating and to keep the APU within its thermal and component limits during start in hot conditions. This combination—minus 54 degrees Celsius up to ISA plus 35—is the standard Embraer specification, and it matches the given correct answer.