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28 Cards in this Set
- Front
- Back
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The Bleed Air System (BAS) is part of what other system? |
The “Environmental Control System” (ECS).
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The bleed air system can obtain bleed air from what locations?
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Both engines
APU |
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From what three (3) locations on the engines can the bleed air system obtain bleed air?
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P2.2 Port: Cooling Bleed Air
P2.7 Port: Low Pressure (LP) Bleed Air P3.0 Port: High Pressure (HP) Bleed Air |
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What determines which port the bleed air is obtained from on the engines?
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Power lever position and the “Environmental Control Unit” (ECU).
Low Power: P3.0 Bleed air is used (High Pressure Bleed) High Power: P2.7 Bleed Air is used (Low Pressure Bleed) |
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At what times can the APU be selected as the “Air Conditioning Source”?
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For ground operations only!
Both engine bleeds must be selected to "OFF". |
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Where is the “Electronic Control Unit” (ECU) physically located on the aircraft?
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In the "Avionics Equipment Bay".
Note: They avionics bay is behind the Fwd flight attendants jump seat. |
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How many ECU’s are there on the aircraft?
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Two (2)
One for each engine! |
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How many channels does each ECU have?
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Two (2)
One (1) “digital” channel and one (1) backup “analog” channel. |
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What does the “digital” channels of the ECU actually control?
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Both the LP and HP bleed air ports (P2.7 & P3.0 bleed air) for the respective engine.
The ECU will maintain the correct bleed air pressures, temperatures and flow rates. |
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What does the “analog” channels of the ECU actually control?
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They act as a backup only to the digital channels.
The backup channel is only capable of controlling the “LP Bleed Air” (P2.7). The “HPSOV” will remain closed when the analog channel is controlling the bleed air system. |
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From what panel is the bleed air controlled from?
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The “Air Conditioning Control Panel”.
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What is the purpose of the “BLEEDS 1/2 ON/OFF” switches?
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It turns the respective engines bleed air ON/OFF by energizing the “Nacelle Shutoff Valve” (NSOV).
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What is accomplished by selecting the “Bleed Air Selector” rotary switch to the “MIN” position?
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It allows the ECU to modulate the volume of “both engines” bleed air at a minimum level.
The ECU will modulate the Nacelle Shutoff Valve to control the bleed air supply. |
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What is accomplished by selecting the “Bleed Air Selector” rotary switch to the “NORM” or “MAX” position?
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It allows the ECU to modulate the bleed air supply at an increase level.
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During normal operations the ECU will modulate each engines Nacelle Shutoff Valve (NSOV) so that each engine will supply _____ of the bleed air flow.
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50%
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How many Bleed Air System (BAS) “Pre-Coolers” are there on the aircraft?
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Four (4)
Two (2) for each engine. |
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Each engines bleed air system has two (2) Pre-Coolers. What are the names of the Pre-Coolers?
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High Stage Pre-Cooler
De-Ice Pre-Cooler |
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What is the purpose of the “High Stage Pre-Cooler”?
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At higher engine settings the HP bleed air is too hot. The ECU will open the P2.2 bleed air port to allow cooler air through the pre-cooler to cool the HP Bleed Air.
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After P2.2 bleed air is used to cool the Pre-Coolers what happens to it?
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It is vented overboard!
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What is the purpose of the “De-Ice Pre-Coolers”?
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They pre-cool the temperature of the bleed air going to the airframe de-ice system.
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Is P2.2 air “modulated” by the ECU to the “De-Ice Pre-Coolers”?
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No
P2.2 air is “constantly” routed through the De-Ice Pre-Coolers to reduce the bleed air temperature. |
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What happens to the P2.2 air after pre-cooling the De-Ice Pre-Coolers?
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It is vented overboard!
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How is an “over-temperature” sensed in the bleed air system?
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A temperature switch is installed in the bleed air supply duct downstream of the pre-coolers.
It measures the bleed air temperature just prior to the Nacelle Shutoff Valve (NSOV). |
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What will occur if the bleed air temperature triggers an “over-temperature” condition?
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The Nacelle Shutoff Valve (NSOV) will automatically close and illuminate the “#1/#2 BLEED HOT” caution light.
Once the bleed air cools the NSOV will automatically open again and resume bleed air operation. |
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What four (4) conditions will cause the “#1/#2 BLEED HOT” caution light to illuminate?
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1. Bleed Air System Over-Temperature
2. Nacelle Duct Leak between the inner and outer walls of the bleed duct. 3. Bleed Overpressure 4. Aft or APU Duct leak |
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If a leak is detected between the inner and outer walls of the bleed air duct, what will occur?
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The “#1/#2 BLEED HOT” caution light will illuminate.
The Nacelle Shutoff Valve (NSOV) will automatically “close” and not re-open. |
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How is a bleed air “over-pressure” condition sensed?
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A pressure switch is installed downstream of the Nacelle Shutoff Valve (NSOV).
If an over-pressure is sensed the ECU will close the Nacelle Shutoff Valve (NSOV) and illuminate the “#1/#2 BLEED HOT” caution light. |
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If a duct leak occurs in the “APU” bleed air supply duct, what will automatically occur?
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The ECU will close “BOTH” Nacelle Shutoff Valves (NSOV’s).
The “#1 BLEED HOT” and the “#2 BLEED HOT” caution lights will both illuminate. |
