Equipment Cooling

Question 1

No engines running, APU providing pack air, Miami at 100 degrees, pack commands 65 degrees, where is the air sent to?

Answer 1

4 zones and E&E

Question 2

How many E&E fans work on the ground?

Answer 2

Both

Question 3

On the ground, the skin heat exchanger is effective when?

Answer 3

<45 degrees

Question 4

With temperature above 45 degrees how is the air dispersed through the system?

Answer 4

Overboard/Ground Exhaust valve open
Skin heater exchanger closed

Question 5

what does the skin heat exchanger do?

Answer 5

Routes warm air from the E&E compartment and cockpit instruments near the skin of the aircraft to cool it. Requires aircraft skin temp to be cool to work

Question 6

On the ground, <45 degrees how is the air dispersed through the system?

Answer 6

Overboard valve closed
Skin Heat exchanger open

Question 7

On the ground, 49 degrees, what is the position of the ground exhaust valve and skin heat exchanger valve, with the APU supplying air?

Answer 7

Overboard/Ground exhaust open
Skin heat exchanger closed because skin heat exchanger is ineffective above 45 degrees

Question 8

Start the right engine (first engine), how does the config of the equipment cool change?

Answer 8

It doesn’t

Question 9

Starting the second engine, how does the config of the equipment cool change?

Answer 9

Boeing logic:
closes inboard supply valve – no air from the packs
3 way valve automatically opens to take conditioned air from the cabin
Skin heat exchanger valve opens
Overboard/Ground Exhaust valve closes

Question 10

With the inboard supply valve open, where is the air coming from?

Answer 10

Coldest available from the packs

Question 11

Boeing logic, in flight, why does the supply fan de-energise?

Answer 11

Skin heat exchanger becomes more effective as the skin cools. only one fan is needed

Question 12

With both engines running, with equipment cooling in auto, Boeing controls Overboard/ground exhaust and skin heat exchanger. What does the valve light mean?

Answer 12

The exhaust valve or heat exchanger valve isn’t in the correct position.
Selecting stand by forces the valve to the correct position
Means we’re able to pressurise

Question 13

In flight, what does the OVHT light on mean?

Answer 13

Exhaust fan failed
Call for the checklist. Select standby. Energises supply fan. OVHT light out
Supply fan needs 5 minutes to cool the system

Question 14

If the OVHT light re-illuminates after 5 minutes and STBY selection, what has happened?

Answer 14

Supply fan has failed to energise
Follow check list. Select OVRD. All the valves forced close (except smoke OVRD). Both fans de-energised. No cooling light inhibited for 1 minute
(Attempting to set up reverse flow pressure differential in thru the 3 way valve to cool out thru the smoke OVRD valve)

Question 15

How do you know the OVRD was successful in clearing the OVHT light?

Answer 15

If the no cooling light doesn’t come on you were successful in setting up reverse flow

Question 16

When you select OVRD, what happens?

Answer 16

Forces valves closed (except smoke OVRD)
De-energises fans
Setting up reverse flow
No cooling light inhibited

Question 17

What does the SMOKE light illuminated mean?

Answer 17

Call for the checklist
Go directly to OVRD

Question 18

What does the No Cooling light mean?

Answer 18

Boeing logic not met
Reverse flow not established
Follow the checklist

Question 19

E&E cooling non normals all require what?

Answer 19

Follow the checklist

Question 20

On the ground how many fans are operational?

Answer 20

2
1 in the air (1 de-energised by the main gear logic)

Question 21

Where does the inboard supply valve take its air from?

Answer 21

Coldest commanded by the packs

Question 22

What does selecting standby do?

Answer 22

In flight - Energises the supply fan
On the ground - commands valve to correct position

Question 23

On the ground, selecting STBY, what is being impacted?

Answer 23

Only impacts valves
In flight - only impacts fans