Air Condition and Pressurization System

Question 1

Before bleed air enters the pneumatic system, what valve does it pass through and what controls this valve?

Answer 1

It passes through the bleed air shutoff valve. This valve is controlled by the CABIN ORESS / RAM/DUMP switch, an AC-powered switch

Question 2

When the Cabin Pressure switch is in the CABIN PRESS position, what happens?

Answer 2

The bleed air valve opens, allowing air to enter the pneumatic system. This activates both the AC system and cabin pressurization system. The air is then cooled, as required, and is directed to the air conditioning, pressurization, defog, canopy seal, and anti-G suit outlet

Question 3

Describe the air conditioning process:

Answer 3

Once the bleed air enters the pneumatic system through the open bleed air shutoff valve, it goes to a heat exchanger. This heat exchanger sends the hot bleed air through coils inside of it while cool ram air from outside is drawn across the coils by a fan.
This air is still at a high pressure. It is sent through a cooling turbine, dropping the pressure and temperature of the air. Excess energy from this system is used to drive the fan for the heat exchanger and the turbine.

Question 4

If the cabin air temperature is in the manual position, how fast will the temperature control valve switch from full hot to full cold or visa versa?

Answer 4

6 seconds

Question 5

When moving the cabin temperature rheostat, what does it do to change the temperature of the cockpit?

Answer 5

The rheostatic uses AC electrical power to move the temperature control valve in the heat exchanger and cooling turbine. This determines the amount of hot air that passes through the cooling turbine

Question 6

What does the defog control in the front cockpit control?

Answer 6

It only controls the volume of airflow sent out for defog

Question 7

What is the defog air temp?

Answer 7

200 F

Question 8

Above what temperature is all defog airflow shutoff by a backup temperature sensor?

Answer 8

280 F

Question 9

Where does the air for cockpit pressurization come from?

Answer 9

Cabin pressurization uses the same conditioned air that enters the cokcpit area

Question 10

When does the canopy seal inflate?

Answer 10

1. When both canopies are down and locked
2. Cabin Pressure Switch is in CABIN PRESS
3. At least one engine is running

Question 11

Is the cabin pressure regulator DC or AC powered?

Answer 11

Neither, it is a mechanical device

Question 12

How does the cabin pressure regulator regulate cabin pressure?

Answer 12

It allows excess air to flow from the cockpit into the nose section equipment bay, cooling the electrical equipment there. This allows for the regulator to maintain the pressure differential.

Question 13

Until what altitude does the cabin pressure regulator maintain a cabin altitude of 8,000 ft?

Answer 13

23,000 ft

Question 14

What altitude does the pressure regulator initiate pressurization?

Answer 14

8000 ft

Question 15

What is the formulate to compute cabin pressure above FL 230? (+/- 2000 ft)

Answer 15

(Altitude - 6,000ft)/2

Question 16

What is the approximate cabin altitude at FL350?

Answer 16

14,500 ft

Question 17

What happens when the RAMP DUMP position of the cabin pressure switch is selected?

Answer 17

The bleed air shutoff valve closes, halting bleed air entering the pneumatic system. The ram dump valve is then opened, and an air scoop extended into the airstream providing an outside ram air source.

Question 18

What two functions are not shut off when ram dump is selected and why?

Answer 18

1. Hydraulic Pressurization
2. Anti-Ice

Because these bleed air lines are located up-line from the bleed air shutoff valve

Question 19

When climbing, what does setting the temperature system to full hot temporarily do?

Answer 19

It helps clear the moisture separator to preclude the canopy fogging up after level off

Question 20

If the canopies fog up, what should you do?

Answer 20

Turn the defog to full on and the ac temperature to full cold. Once the canopies clear, increase ac temperature to clear the moisture separator.

Question 21

How does pitot heat work?

Answer 21

The pitot is heated by an AC powered heating system. When the Pitot switch is placed on, power is supplied to the pitot boom heater, the AOA transmitter vane, and the Total Air Temperature probe heater

Question 22

What does the pitot heat system heat?

Answer 22

1. The Pitot Tube
2. The AOA transmitter vane
3. The Total Air Temperature probe heater

Question 23

What may happen if you leave the Pitot Heat on on the ground for more than 30 seconds?

Answer 23

1. YSAS can disengage and not reengage unless sufficient cooling airflow is generated (25 knots) or pitot heat is turned off and it cools down sufficiently
2. Vibration of the AOA vane transmitter heating element can generate an ADC PFL and all the AOA indexer lights can illuminate
3. TAS is not available for display