NATOPS - ECS and OBOGS

Question 1

What three systems are part of the Environmental Control System (ECS)?

Answer 1

Air Conditioning, Cockpit Pressurization, and Avionics Equipment Cooling

Question 2

Where does the air for the cabin pressurization and air conditioning come from?

Answer 2

5th stage of the high pressure compressor

Question 3

What are the inducers used for?

Answer 3

To increase airflow through the heat exchangers while the landing gear is extended

Question 4

What positions will the Main Pressure Regulation Shutoff Valve (MPRSOV) and Inducer Pressure Regulation Shutoff Valve (IPRSOV) be in if electrical power is removed and why?

Answer 4

Open, so in the event of an electrical failure the air conditioning and pressurization will remain on

Question 5

What is the purpose of the ram air inlet and outlet valves?

Answer 5

To provide emergency ventilation when the cockpit air condition system is switched off to remove smoke or uncontrollable fogging from the cockpit.
(These valves remain open on the ground)

Question 6

How many heat exchangers are used to condition the cockpit air?

Answer 6

Two. The primary heat exchanger (just after the MPRSOV)

and the secondary heat exchanger (just after the Cold Air Unit compressor and before the Cold Air Unit turbine)

Question 7

How is temperature of cockpit air regulated?

Answer 7

By the Temperature Control Valve and Max Defog Valve (when installed) which allow hot bleed air to bypass the heat exchangers

Question 8

Explain the different modes for temperature control

Answer 8

• Auto mode - regulates cockpit temperature based on the CABIN TEMP setting (limits duct temp to between 2.5 and 75 degrees C)
• Manual mode - CABIN TEMP knob directly controls the position of the temperature control valve
• Max Defog mode (After AFC-291) - similar to auto mode, but limits duct temp to between 17 and 90 degrees C

Question 9

How is cockpit pressurization controlled?

Answer 9

By the pressure control valve and its slave discharge valve by restricting the discharge of air from the cockpit to maintain the desired differential pressure

Question 10

How is cockpit pressure scheduled?

Answer 10

Pressurization commences with weight off wheels and increases linearly until the full differential pressure of 4 psi is attained at 40,000’

Question 11

What pressure is the safety relief valve set to?

Answer 11

4.8 psi

Question 12

How is the canopy seal control valve operated?

Answer 12

mechanically by the canopy locking system

Question 13

Where does cooling air for avionics equipment come from?

Answer 13

Cockpit air exhausted through the pressure control valve and discharge valve passes through the avionics compartment

Question 14

What causes the CABIN ALT warning light to illuminate?

Answer 14

• AC system failure caused by overpressure of the CAU compressor
• CAU outlet temperature above 500 degrees F
• CAU turbine inlet temperature above 250 degrees F
• Cockpit pressurization failure when cabin altitude exceeds 24,000 +/-500 feet

Question 15

***What commands the IPRSOV open, and what is it used for?

Answer 15

Gear down and ECS not OFF
The IPRSOV provides bleed air to the inducers to enhance the efficiency of the ECS heat exchangers at lower airspeeds (high AOA)

Question 16

***When are the ram air valves open?

Answer 16

On the ground (weight on wheels) and in flight with air flow knob OFF

Question 17

***What is the function of the OBOGS Concentrator?

Answer 17

To remove nitrogen and other contaminents