Environmental System

Question 1

When do you get avionics overheat?

Answer 1

when temp in avionics rack exceeds 90 degrees F for 5 mins

Question 2

What happens when you press the AVIONICS COOL ORIDE switch located on the environmental control panel?

Answer 2

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

Question 3

What criteria drive an avionics overheat?

Answer 3

when temp in avionics rack exceeds 90 deg F for 5 mins

Question 4

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?

Answer 4

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

Question 5

What happens when you get an avionics overheat w/ an engine running on the ground or in flight

Answer 5

the warning horn sounds, but the electrical buses do not shed

Question 6

Brief overview of avionics overheat checklist:

Answer 6

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

Question 7

What would pressing the COMPT AIRFLOW switch do and is it an option for an avionics overheat?

Answer 7

it shuts off all airflow to the flight and cargo compartments, air only to avionics
Yes

Question 8

What does an open loop mean?

Answer 8

both A/C packs are off, and WOW on cooling air is drawn through the nose wheel well by the avionics cooling fan

Question 9

What does a closed loop mean?

Answer 9

if either A/C pack is on-cooling system operates as described in Sec. 1

Question 10

When should you use a closed loop?

Answer 10

when OAT is 90 deg F or more

Question 11

What is the AUTO mode of the px system?

Answer 11

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

Question 12

What is the semi mode of the px system?

Answer 12

adjusts outflow valve to set cabin px to the LDG ALT-FT on the px panel
outflow valve is driven fully open upon landing

Question 13

What is the manual mode of the px system?

Answer 13

crew directly controls the outflow valve

Question 14

Where are the positive px relief valves? How do they work?

Answer 14

three of them
aft right side of fuselage
open if cabin exceeds 8.2 DeltaP
can also be opended by the emer depress switch

Question 15

Where are the negative px relief valves? How do they work?

Answer 15

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

Question 16

What is the maximum altitude you can fly and maintain sea level cabin altitude?

Answer 16

19,800 ft

Question 17

How do you maintain a sea level cabin altitude for your flight?

Answer 17

set SEMI and the cruise altitude in the LDG ALT-FT window

Question 18

What does the HI-FLOW switch do?

Answer 18

commands both A/C flow valves to operate on the high flow schedule

Question 19

How much extra fuel will you burn per hour with the HI-FLOW switch selected?

Answer 19

it will increase the cruise fuel flow by 100 lbs per hour

Question 20

What does the CMPT AIRFLOW switch do?

Answer 20

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

Question 21

When do you use the compartment airflow switch?

Answer 21

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

Question 22

What does the REMOTE TEMP CONTROL switch do?

Answer 22

when selected OFF, transfers cargo compartment temp control from the FLM station to the environmental panel

Question 23

Do you still have avionics overheat protection with ground A/C and AVIONICS COOL ORIDE on?

Answer 23

yes, with an external power cart of APU furnishing electrical power

Question 24

What does the Trim Air Switch do?

Answer 24

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

Question 25

If an air conditioner ground unit is to be used for cooling air, what button(s) is/are pressed to get avionics cooling?

Answer 25

AVIONICS COOL ORIDE

Question 26

What does a MANIFOLD FAIL light on the environmental control panel tell us?

Answer 26

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

Question 27

What 2 conditions allow the RAM AIR to operate?

Answer 27

the aircraft must be fully de-px with both AC packs shutdown

Question 28

What areas do the air conditioning packs supply?

Answer 28

normally, the left pack supplies the flight compartment, crew rest, and avionics cooling; the right pack supplies the cargo compartment

Question 29

How is the cargo compartment floor heated?

Answer 29

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