With one air conditioning pack inop, what is the maximum dispatch altitude?

With one air conditioning pack inop, what is the maximum dispatch altitude?

• A. Fifteen thousand feet
• B. Ten thousand feet
• C. Twenty-five thousand feet
• D. Thirty thousand feet

Answer: (C)

With one air conditioning pack inoperative, the environmental control system has reduced capacity to condition and supply cabin air. To reliably maintain acceptable cabin temperature, pressurization, and avionics cooling with only a single pack, the aircraft must operate at a lower cruise altitude. That’s why the maximum dispatch altitude is limited to 25,000 feet. Above this, the single remaining pack can’t meet the environmental load, so operation at higher altitudes would risk uncomfortable cabin conditions and potential equipment cooling issues. If higher altitude is required, the situation would need the failed pack repaired or an MEL-based approval to operate with both packs active.

With one air conditioning pack inoperative, the environmental control system has reduced capacity to condition and supply cabin air. To reliably maintain acceptable cabin temperature, pressurization, and avionics cooling with only a single pack, the aircraft must operate at a lower cruise altitude. That’s why the maximum dispatch altitude is limited to 25,000 feet. Above this, the single remaining pack can’t meet the environmental load, so operation at higher altitudes would risk uncomfortable cabin conditions and potential equipment cooling issues. If higher altitude is required, the situation would need the failed pack repaired or an MEL-based approval to operate with both packs active.