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PNEUMATICS
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2. THIS PRESENTATION INCLUDES THE SOURCES OF AIR, THE MAJOR SYSTEM COMPONENTS AND THE WAY THE CONTROLS AND INDICATORS ARE USED TO OPERATE THE PNEUMATIC SYSTEM. FIRST, LET'S LOOK AT THE SOURCES OF AIR.
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3. THE SOURCES OF AIR FOR THE PNEUMATIC SYSTEM ARE: THE ENGINES (pause2) THE AUXILIARY POWER UNIT (pause2) OR A GROUND PNEUMATIC CART
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4. DURING GROUND OPERATION, THE NORMAL SUPPLY OF BLEED AIR FOR THE PNEUMATIC SYSTEM IS THE APU (pause2) (pause3) HOWEVER, A GROUND CART MAY BE USED WHEN IT IS AVAILABLE (pause2) (pause2) AFTER ENGINE START, BLEED AIR IS NORMALLY SUPPLIED BY THE ENGINES.
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5. THE PRIMARY SOURCE OF BLEED AIR IS THE MID OR EIGHTH STAGE OF THE ENGINE COMPRESSOR SECTION. IF THE VOLUME OF MID STAGE AIR IS INSUFFICIENT FOR THE SYSTEM DEMAND, HIGH, OR 13TH STAGE, BLEED AIR AUGMENTS THE SUPPLY. CHECK VALVES ENSURE THE PROPER DIRECTION OF AIR FLOW. AIR FROM THE MID AND HIGH COMPRESSOR SECTIONS IS HOT.
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6. THIS HOT AIR IS COOLED BY FAN AIR PASSING THROUGH HEAT EXCHANGERS (pause2) A
THERMOSTATICALLY CONTROLLED VALVE AUTOMATICALLY REGULATES THE VOLUME OF FAN AIR REQUIRED FOR COOLING.
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7. ANSWER AA IS CORRECT.
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8. BLEED AIR IS COOLED BY FAN AIR PASSING THROUGH HEAT EXCHANGERS
BLEED AIR IS COOLED BY FAN AIR PASSING THROUGH HEAT EXCHANGERS. (pause4) NOW, LET'S LOOK AT THE COCKPIT CONTROLS AND INDICATORS.
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9. THE CONTROLS AND INDICATORS FOR THE PNEUMATIC SYSTEM ARE LOCATED ON THE RIGHT SIDE OF THE FORWARD OVERHEAD PANEL. LOCATE THESE CONTROLS AND INDICATORS ON YOUR PANEL.
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10. LET'S LOOK AT THE PNEUMATIC CONTROLS AND INDICATORS IN GREATER DETAIL.
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11. THE ENGINE BLEED-AIR SWITCHES OPEN AND CLOSE THE RESPECTIVE BLEED AIR VALVE. THESE VALVES OPERATE ON AC POWER. (pause3) IF THE TEMPERATURE DOWNSTREAM OF THE VALVE IS EXCESSIVE, A TEMPERATURE SENSOR AUTOMATICALLY CLOSES THE RESPECTIVE VALVE TO PREVENT DAMAGE TO AIRPLANE COMPONENTS. WITH AN OVER TEMPERATURE CONDITION, THE BLEED TRIP [`]OFF LIGHT ILLUMINATES.
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12. THE APU BLEED AIR SWITCH OPENS AND CLOSES THE APU BLEED AIR VALVE
THE APU BLEED AIR SWITCH OPENS AND CLOSES THE APU BLEED AIR VALVE. AS WITH THE ENGINE BLEEDS, THE APU BLEED ALSO OPERATES ON AC POWER. WHEN THE VALVE OPENS, IT ALLOWS AIR TO FLOW FROM THE APU INTO THE PNEUMATIC SYSTEM. A CHECK VALVE PREVENTS ENGINE OR GROUND CART BLEED AIR FROM FLOWING INTO THE APU.
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13. THE LEFT AND RIGHT PACK SWITCHES CONTROL ELECTRICAL POWER TO THE PACK VALVES. THE VALVES ARE SPRING-LOADED CLOSED. WITH AIR PRESSURE, THE VALVES OPEN AND REGULATE THE FLOW OF BLEED AIR ENTERING THE AIR CONDITIONING PACKS. THESE VALVES OPERATE FROM BATTERY BUS POWER.
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14. AN AC POWERED ISOLATION VALVE SEPARATES THE LEFT AND RIGHT SIDES OF THE PNEUMATIC MANIFOLD. THE NUMBER ONE ENGINE AND APU ARE ON THE LEFT SIDE OF THE VALVE. THE NUMBER TWO ENGINE AND THE PNEUMATIC GROUND CART CONNECTION ARE ON THE RIGHT SIDE.
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15. PNEUMATIC PRESSURE IS SENSED ON EACH SIDE OF THE ISOLATION VALVE AND DISPLAYED ON THE DUCT PRESSURE INDICATOR. THIS INDICATOR REQUIRES AC POWER. THE L POINTER INDICATES THE PRESSURE ON THE LEFT SIDE OF THE PNEUMATIC MANIFOLD, AND THE R POINTER, THE PRESSURE ON THE RIGHT SIDE. IF THE ISOLATION VALVE IS OPEN, BOTH PRESSURE INDICATIONS ARE THE SAME.
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16. THE DUCT PRESSURE INDICATOR DISPLAYS THE PRESSURE IN THE DUCTS FROM ANY OF THE PNEUMATIC SOURCES (pause2) THE ENGINES, (pause2) THE APU, (pause2) OR THE GROUND PNEUMATIC CART. (pause4) WHEN THE APU IS PROVIDING THE BLEED AIR AND THE ISOLATION VALVE IS CLOSED, THE L POINTER INDICATES APU BLEED AIR PRESSURE. THE R POINTER INDICATES PRESSURE ON THE RIGHT SIDE OF THE VALVE. NOW LET'S LOOK AT THE ISOLATION VALVE.
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17. THE ISOLATION VALVE SWITCH HAS THREE POSITIONS (pause2) CLOSE, AUTO, AND OPEN (pause2) THE NORMAL POSITION OF THE SWITCH IS AUTO. PLACING THE SWITCH TO OPEN WILL OPEN THE VALVE (pause2) THE CLOSE POSITION WILL CLOSE THE VALVE. LET'S EXAMINE THE AUTO POSITION OF THE SWITCH IN MORE DETAIL.
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18. WITH THE SWITCH IN THE AUTO POSITION, THE ISOLATION VALVE IS CONTROLLED BY THE POSITION OF THE ENGINE BLEED AND PACK SWITCHES (pause2) IF BOTH ENGINE BLEED SWITCHES AND BOTH PACK SWITCHES ARE ON, THE VALVE WILL BE CLOSED. THIS ISOLATES THE LEFT AND RIGHT SIDES OF THE PNEUMATIC SYSTEM SO THAT EACH ENGINE SUPPLIES AIR TO ONE PACK. THIS IS A NORMAL IN-FLIGHT CONDITION. THE APU BLEED SWITCH HAS NO EFFECT ON THE ISOLATION VALVE OPERATION. COMPARE
THE PANEL SWITCH SELECTION TO THE ACTUAL VALVE POSITION.
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19. WITH THE ISOLATION VALVE SWITCH IN AUTO, POSITIONING AN ENGINE BLEED OR PACK SWITCH TO [`]OFF, (pause3) SIGNALS THE SWITCH LOGIC TO OPEN THE ISOLATION VALVE. THIS CONNECTS THE LEFT AND RIGHT SIDES OF THE PNEUMATIC SYSTEM. (pause2) IN THIS SITUATION, THE LEFT PACK SWITCH IS [`]OFF (pause2) THEREFORE, THE ISOLATION VALVE IS OPEN. STUDY THE SWITCH SELECTION AND COMPARE THE EFFECT ON THE ISOLATION VALVE POSITION.
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20. THE CORRECT ANSWER IS B.
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21. THE ISOLATION VALVE SWITCH IS IN AUTO, AND ALL ENGINE BLEED AND PACK SWITCHES ARE ON. (pause2) THEREFORE, THE VALVE IS CLOSED. THIS IS A NORMAL IN-FLIGHT PANEL CONFIGURATION.
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22. THE CORRECT ANSWER IS A.
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23. THE ISOLATION VALVE IS CLOSED, AND THE RIGHT POINTER INDICATES THE PRESSURE DEVELOPED BY THE GROUND CART. (pause3) LET'S PROCEED TO THE SWITCH SELECTION TO SET THE PANEL FOR ENGINE START.
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24. NORMALLY, APU BLEED AIR IS USED TO START THE ENGINES
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25. BOTH ENGINE BLEED VALVES AND THE ISOLATION VALVE MUST BE OPEN TO PERMIT AIR TO REACH THE STARTERS (pause2) FOR THIS REASON, THESE BLEED SWITCHES ARE LEFT [']ON PRIOR TO ENGINE SHUT DOWN. THIS INSURES THAT THE VALVES ARE OPEN FOR ENGINE START IN THE EVENT THAT AC POWER IS NOT AVAILABLE, IN WHICH CASE (pause2) THE ENGINE BLEED VALVES MAY BE MANUALLY OPENED.
COMPARE THE SWITCH SELECTIONS TO THE ACTUAL VALVE POSITIONS.
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26. AIR FROM THE PNEUMATIC GROUND CART MAY BE USED TO START THE ENGINES
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27. THE ENGINE BLEED AND ISOLATION VALVES MUST BE OPEN
THE ENGINE BLEED AND ISOLATION VALVES MUST BE OPEN. THE APU BLEED VALVE MUST BE CLOSED TO PREVENT THE POSSIBILITY OF GROUND CART OR ENGINE BLEED AIR FROM ENTERING THE APU (pause2) COMPARE THE SWITCH SELECTIONS TO THE ACTUAL VALVE POSITIONS.
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28. A CROSS BLEED START USES AN OPERATING ENGINE AS A BLEED AIR SOURCE TO START THE OTHER ENGINE
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29. THE ENGINE BLEED AND ISOLATION VALVES ARE OPEN FOR A CROSS BLEED START (pause2) THE APU BLEED VALVE WILL BE CLOSED FOR THIS OPERATION. THE ISOLATION VALVE SWITCH REMAINS IN AUTOMATIC (pause2) COMPARE THE VALVE POSITIONS TO THE SWITCH SELECTIONS. IN THIS SITUATION, THE NUMBER TWO ENGINE IS PROVIDING THE BLEED AIR. REVIEW THE CROSS BLEED START IN SUPPLEMENTARY PROCEDURES.
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30. THERE IS A DUAL BLEED LIGHT LOCATED ABOVE THE PNEUMATIC PANEL.
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31. WHEN BOTH AN ENGINE AND THE APU BLEED VALVE OPEN, THERE IS A POSSIBILITY THAT AIR FROM THE ENGINE COULD BACK PRESSURE THE APU. THE DUAL BLEED LIGHT ILLUMINATES WHENEVER BOTH OF THESE VALVES ARE OPEN. ILLUMINATION OF THIS LIGHT IS AN INDICATION OF CERTAIN COMBINATIONS OF VALVE POSITIONS. (pause2) IT MEANS THAT THE ENGINE, ISOLATION, AND APU VALVES ARE POSITIONED OPEN SO THAT ANY ENGINE BLEED AIR CAN BACK-PRESSURE THE APU BLEED AIR. (pause2) IN THIS CASE, THE BLACK ARROWS INDICATE THAT WITH THE APU BLEED VALVE, (pause2) THE ISOLATION VALVE (pause2) AND THE NUMBER TWO ENGINE BLEED VALVE OPEN, THE NUMBER TWO ENGINE BLEED AIR CAN BACK PRESSURE THE APU, AND THE LIGHT ILLUMINATES. ILLUMINATION OF THE DUAL BLEED LIGHT IS A NORMAL INDICATION DURING ENGINE START. WHEN THE APU IS THE SOURCE OF BLEED AIR; AND DURING GROUND OPERATIONS WHEN THE APU IS USED AS A PNEUMATIC BLEED SOURCE FOR CABIN HEATING OR COOLING. TO EXTINGUISH THE LIGHT, RE-CONFIGURE EITHER OR THE ENGINE BLEED, ISOLATION, AND APU BLEED VALVE SWITCHES TO OFF. THIS ELIMINATES THE POTENTIAL FOR ANY ENGINE BLEED AIR TO BACK-PRESSURE THE APU. (pause4) THIS LIGHT OPERATES ONLY AS A FUNCTION OF VALVE POSITION AND CAN ILLUMINATE EVEN WITH THE ENGINES SHUT DOWN AND NO ENGINE PNEUMATIC PRESSURE AVAILABLE. TO ENSURE THAT NO SIGNIFICANT BACK-PRESSURE OCCURS, ENGINE THRUST MUST BE LIMITED TO IDLE WHILE THIS LIGHT IS ILLUMINATED.
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32. ANSWER C IS CORRECT.
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33. POSITIONING THE APU BLEED SWITCH TO [']OFF, ELIMINATES THE POSSIBILITY OF BACK-PRESSURING THE APU WITH ENGINE BLEED AIR, AND THE LIGHT EXTINGUISHES. THE LIGHT WILL ALSO BE EXTINGUISHED BY LEAVING THE APU BLEED [']ON, AND POSITIONING BOTH ENGINE BLEEDS TO [']OFF.
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34. LET'S EXAMINE THE NORMAL PREFLIGHT PNEUMATIC PANEL CONFIGURATION FOR AN ENGINE START USING THE APU.
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35. FIRST, POSITION THE LEFT AND RIGHT PACK SWITCHES OFF, TO ENSURE ALL BLEED AIR IS AVAILABLE FOR THE STARTERS. A MINIMUM OF 30 PSI IS REQUIRED FOR NORMAL ENGINE START.
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36. SECOND, VERIFY THE ISOLATION VALVE SWITCH IS IN THE AUTO POSITION, SO BLEED AIR CAN FLOW TO ENGINE NUMBER TWO. (pause2) THIRD, VERIFY THE ENGINE AND APU BLEED SWITCHES ARE ON. THIS ALLOWS BLEED AIR FROM THE APU TO ENTER THE PNEUMATIC MANIFOLD AND FLOW TO THE STARTERS (pause2) REVIEW THIS OPERATION UNTIL YOU ARE CONFIDENT THAT YOU UNDERSTAND IT.
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37. ANSWER C IS CORRECT.
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38. THE NUMBER ONE ENGINE BLEED VALVE IS CLOSED SO THE PNEUMATIC GROUND CART CAN SUPPLY AIR PRESSURE TO START ENGINE NUMBER TWO ONLY.
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39. THE AIRPLANE MAY BE OPERATED IN AN ENGINE BLEEDS [']OFF CONFIGURATION FOR TAKEOFF.
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40. IN THIS CONFIGURATION, THE APU SUPPLIES AIR TO THE LEFT AIR CONDITIONING PACK. THE ISOLATION VALVE IS CLOSED BECAUSE THE APU CANNOT SUPPLY ENOUGH AIR FOR BOTH AIR CONDITIONING PACKS. THIS PROCEDURE PERMITS ENGINE TAKEOFF THRUST TO BE SET TO EITHER THE LOWER E-P-R, THAT WOULD BE REQUIRED IF ENGINE BLEEDS WERE USED TO OPERATE THE PACKS, OR, TO THE MAXIMUM ENGINE BLEEDS [']OFF E-P-R, WHEN ADDITIONAL THRUST IS REQUIRED FOR TAKEOFF. THE ENGINE BLEEDS [']ON E-P-R IS POINT ZERO FOUR LESS THAN THE BLEEDS [']OFF E-P-R. (pause3) USE OF THE LOWER E-P-R REDUCES INTERNAL ENGINE TEMPERATURES AND EXTENDS ENGINE LIFE. THE LOWER E-P-R MAY BE USED WHENEVER THE ACTUAL TAKEOFF WEIGHT IS SUFFICIENTLY LESS THAN THE PUBLISHED MAXIMUM WEIGHT FOR EACH RUNWAY. REVIEW THE PANEL CONFIGURATION, AND ITS EFFECT ON SYSTEM OPERATION.
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41. NOW, REFER TO THE TAKEOFF PERFORMANCE SECTION OF YOUR MANUAL AND REVIEW THE WEIGHT REDUCTION REQUIRED WHEN USING THE ENGINE BLEEDS [']ON E-P-R.
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42. NOW, LET'S CONFIGURE THE PNEUMATIC PANEL FOR AN ENGINE BLEEDS [']OFF TAKEOFF OR LANDING.
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43. FOR AN ENGINE BLEEDS [']OFF TAKEOFF, FIRST, POSITION THE RIGHT PACK SWITCH [']ON, THE ISOLATION VALVE SWITCH TO CLOSE, AND THE LEFT PACK SWITCH [']ON.
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44. NEXT, POSITION THE NUMBER ONE BLEED SWITCH OFF, AND VERIFY THE APU BLEED SWITCH IS ON. THIS ALLOWS BLEED AIR FROM THE APU TO FLOW TO THE LEFT PACK. FINALLY, POSITION THE NUMBER TWO ENGINE BLEED SWITCH TO OFF. NOTICE THAT THIS OPERATION IS PERFORMED USING A LETTER C PATTERN FLOW. REVIEW THESE STEPS AS YOU TRACE THE C PATTERN.
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45. AFTER TAKEOFF, THE PANEL IS RE-CONFIGURED TO ALLOW THE ENGINES TO SUPPLY THE AIR CONDITIONING PACKS. FOR AN ENGINE BLEEDS [`]OFF LANDING, THE LETTER C PATTERN IS AGAIN USED TO POSITION THE SWITCHES EXACTLY AS FOR AN ENGINE BLEEDS [`]OFF TAKEOFF
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46. AFTER AN ENGINE BLEEDS-OFF LANDING, DURING TAXI IN, THE PANEL IS CONFIGURED USING THE REVERSE LETTER C PATTERN FLOW SO THAT THE ENGINE BLEEDS ARE BOTH [']ON, THE APU BLEED [']OFF, THE ISOLATION VALVE AUTO, AND THE LEFT PACK [']OFF. (pause2) WE WILL CONCLUDE THIS SECTION WITH A DISCUSSION OF THE PNEUMATIC DUCT PROTECTION FEATURES.
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47. OVERHEAT DETECTORS ARE INSTALLED ALONG THE PNEUMATIC DUCT SYSTEM TO DETECT BLEED AIR LEAKAGE FROM THE DUCTS. THESE DETECTORS FOLLOW THE PNEUMATIC SYSTEM FROM THE FIRE WALLS TO THE AIR CONDITIONING PACKS. THEY ARE LOCATED ADJACENT TO THE DUCTS IN BOTH THE WING AND BODY AREAS.
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48. WHEN AN OVERHEAT CONDITION OCCURS, THE APPROPRIATE WING BODY OVERHEAT LIGHT WILL ILLUMINATE.
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49. REVIEW THE PNEUMATIC SYSTEM IN THE LIMITATIONS SECTION OF YOUR OPERATIONS MANUAL AT THIS TIME.
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50. THE CORRECT ANSWER IS B.
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51. NOW, REVIEW THE TEST PROCEDURE FOR THE WING BODY OVERHEAT DETECTION CIRCUITS.
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52. THIS IS FOUND IN THE AIR CONDITIONING AND PRESSURIZATION SECTION OF SUPPLEMENTARY PROCEDURES.
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53. END RETURN TO MENU MENU PRINCIPAL
THIS CONCLUDES THE SECTION ON THE PNEUMATIC SYSTEM.
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