What is the maximum altitude for single pack operations?

What is the maximum altitude for single pack operations?

• A. 29,000 ft
• B. 31,000 ft
• C. 33,000 ft
• D. 35,000 ft

Answer: (B)

The key idea is how much conditioning capacity you have when only one air conditioning pack is working. With both packs, the system can meet cabin cooling, heating, and air supply demands across the cruise envelope. When one pack is inoperative, the remaining pack has to handle all the load by itself, so there’s a certification-based altitude limit where it can still maintain acceptable cabin temperature and pressurization. Beyond that limit, the single pack can’t supply enough conditioned air or maintain the proper cabin environment. That limit for the ERJ 175 is thirty-one thousand feet. Below this, the single pack can keep the cabin within acceptable conditions; above it, performance would degrade and safety margins could be compromised. The higher altitudes listed would require two packs to maintain acceptable cabin conditions.

The key idea is how much conditioning capacity you have when only one air conditioning pack is working. With both packs, the system can meet cabin cooling, heating, and air supply demands across the cruise envelope. When one pack is inoperative, the remaining pack has to handle all the load by itself, so there’s a certification-based altitude limit where it can still maintain acceptable cabin temperature and pressurization. Beyond that limit, the single pack can’t supply enough conditioned air or maintain the proper cabin environment.

That limit for the ERJ 175 is thirty-one thousand feet. Below this, the single pack can keep the cabin within acceptable conditions; above it, performance would degrade and safety margins could be compromised. The higher altitudes listed would require two packs to maintain acceptable cabin conditions.