Environmental System Flashcards
When do you get avionics overheat?
when temp in avionics rack exceeds 90 degrees F for 5 mins
What happens when you press the AVIONICS COOL ORIDE switch located on the environmental control panel?
the environmental system controller (ESC) is bypassed, augmentation and avionics outflow valves are fully opened, both packs are commanded to high flow and the left pack is controlled to 40+-5 F
What criteria drive an avionics overheat?
when temp in avionics rack exceeds 90 deg F for 5 mins
What happens when you get an avionics overheat occurs on the ground, w/ no eng running and an ext power source of the APU providing electrical power?
all avionics equipment not powered by the batt and emer bus are de-energized to prevent excessively high avionics compartment temps
warning horns sound in the cargo comp and right wheel well
What happens when you get an avionics overheat w/ an engine running on the ground or in flight
the warning horn sounds, but the electrical buses do not shed
Brief overview of avionics overheat checklist:
try to get as much cool air to the avionics compt as quickly as possible
begins by ensuring AC packs are on, then activates the AVIONICS COOL ORIDE switch
What would pressing the COMPT AIRFLOW switch do and is it an option for an avionics overheat?
it shuts off all airflow to the flight and cargo compartments, air only to avionics
Yes
What does an open loop mean?
both A/C packs are off, and WOW on cooling air is drawn through the nose wheel well by the avionics cooling fan
What does a closed loop mean?
if either A/C pack is on-cooling system operates as described in Sec. 1
When should you use a closed loop?
when OAT is 90 deg F or more
What is the AUTO mode of the px system?
automatic modulation of the outflow valve during climb, cruise and descent for altitude auto schedule
rate of de-px is computed to 20 sec after touchdown
What is the semi mode of the px system?
adjusts outflow valve to set cabin px to the LDG ALT-FT on the px panel
outflow valve is driven fully open upon landing
What is the manual mode of the px system?
crew directly controls the outflow valve
Where are the positive px relief valves? How do they work?
three of them
aft right side of fuselage
open if cabin exceeds 8.2 DeltaP
can also be opended by the emer depress switch
Where are the negative px relief valves? How do they work?
three of them
aft fuselage: 2 on left side, 1 on right side
prevent cabin pressure differential from being lower inside than outside
operation is automatic w/ no indication to crew
What is the maximum altitude you can fly and maintain sea level cabin altitude?
19,800 ft
How do you maintain a sea level cabin altitude for your flight?
set SEMI and the cruise altitude in the LDG ALT-FT window
What does the HI-FLOW switch do?
commands both A/C flow valves to operate on the high flow schedule
How much extra fuel will you burn per hour with the HI-FLOW switch selected?
it will increase the cruise fuel flow by 100 lbs per hour
What does the CMPT AIRFLOW switch do?
when pressed, the trim air regulators close, the flight comp/crew rest area and cargo compartment SOVs close, the avionics cooling augmentation valve opens, & the re-circulation fans shut off
R pack flow control valve closes, L pack is commanded to low flow schedule for avionics cooling
When do you use the compartment airflow switch?
when we encounter or anticipate environmental air contaminated by chemicals, biological agents, or radiation
also it is selected when air conditioning ground unit is used
What does the REMOTE TEMP CONTROL switch do?
when selected OFF, transfers cargo compartment temp control from the FLM station to the environmental panel
Do you still have avionics overheat protection with ground A/C and AVIONICS COOL ORIDE on?
yes, with an external power cart of APU furnishing electrical power
What does the Trim Air Switch do?
controls the trim air px regulators if pressed (OFF), packs will supply air as directed by the ESC at a temp to keep the warmest are controlled other areas may be cooler than selected
If an air conditioner ground unit is to be used for cooling air, what button(s) is/are pressed to get avionics cooling?
AVIONICS COOL ORIDE
What does a MANIFOLD FAIL light on the environmental control panel tell us?
an overheat is detected along the associated manifold system (a rupture has occurred allowing hot bleed air to escape the ducting)
the light remains illuminated for a min of 15 secs, and extinguishes when the sensing elements have cooled below the trip temp
What 2 conditions allow the RAM AIR to operate?
the aircraft must be fully de-px with both AC packs shutdown
What areas do the air conditioning packs supply?
normally, the left pack supplies the flight compartment, crew rest, and avionics cooling; the right pack supplies the cargo compartment
How is the cargo compartment floor heated?
heat strips installed on the under floor surface
the system is activated when the aircraft is electrically powered, all AUX hydraulic pumps are OFF, and the cargo compartment floor temperature is below 65 deg F
