Oral Prep - Air Conditioning Flashcards
What does the FAN position of the CARGO switch provide?
Recirculated cabin exhaust air to the cargo compartment.
What does the COND AIR position of the CARGO switch provide?
Recirculated cabin exhaust air mixed with fresh air from the right pack or air warmed by a thermal heater to the cargo bay area.
When is COND AIR required to be used in the CARGO compartment?
When live cargo is carried.
Why does the “CARGO OVERHEAT” abnormal procedure have you select the Fan position?
Overheat protection is only provided in COND AIR, power for the over-temperature circuit is removed when in fan.
When would the Ram Air switch be used?
During unpressurized flight, or when QRH directed
What happens to the pack during a “PACK HI PRESS” condition?
The affected pack turns off, the 10th stage isolation valve, pack valve and the associated 10th stage shut off valve close when the engine is supplying bleed air.
What happens to the pack during a “PACK HI TEMP” condition?
The affected pack turns off.
How are the pack heat exchangers cooled?
By a ram-air heat exchanger.
If the pressurization is deferred can you operate the packs? Why would you want to? Where is the procedure?
Yes, there are several items that may be differed per the MEL that will lead to operating the aircraft unpressurized. The MEL will refer you to the QRH Abnormal section 2-5, Unpressurized Flight Procedure which has a section for PACKS ON and PACKS OFF. If the packs are operable they can provide heating or cooling as needed.
What is a PRSOV? What does the PRSOV do if only one pack is operating? What is the maximum altitude for single pack operation?
Both the left and right pack are housed in the aft equipment bay. The right pack normally supplies air to the cabin; the left pack to the flightdeck. The pressure of air in the 10th stage manifold is regulated by two PRSOVs, not depicted on the EICAS ECS synoptic page. The PRSOVs reduce and regulate the amount of bleed air entering the pack. The PRSOVs operate on two schedules, dual pack, or single. When single pack, the PRSOV boosts the remaining pack’s operating pressure. Maximum operating altitude single pack is 25,000 ft.
