Table 1
Configure Aircraft for Unpressurized Flight
21 - Air Conditioning
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Chapter 21 Para.
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Item
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OPERATIONAL PROCEDURES
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10-1,
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Stated in each listed paragraph
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Perform the following steps for unpressurized low-level flight:
Prior to the first flight of the day and before engine and APU start, confirm Ram Air and Dump Valve, or Vent Valve (Post Mod. 25G726A/C) operative. Ram Air Valve movement can be heard from Rear Equipment Bay when DUMP VLV , or VENT VALVE (Post Mod. 25G726A/C) is selected OPEN.
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Configure the aircraft for unpressurized flight:
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Select DUMP VLV, or VENT VALVE (Post Mod. 25G726A/C) fully OPEN.
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F/DK VLV positioned as required.
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Operate at or below 15,000 feet MSL.
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Comply with FAR 91.211 or FAR 135.89 and FAR 131.157.
Passenger Oxygen Masks will deploy automatically when the cabin altitude reaches 12,000 feet MSL +/- 500 feet.
The Passenger Supply Valve may be selected closed to prevent passenger oxygen mask deployment, provided the aircraft is operated at or below 10,000 feet MSL or the passenger cabin has no occupants.
NOTE
Special attention should be given to planning low altitude flight
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10-2,
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10-3,
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10-6-2,
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10-11,
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10-12,
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10-13,
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10-14,
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10-15,
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10-16,
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20-4,
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30-3,
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30-5,
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30-6-1,
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30-6-2,
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30-6-3,
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30-7,
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30-8,
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60-4, &
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60-7
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Table 2
Aircraft Altitude Versus Cabin Altitude
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Cabin Altitude (feet)
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Aircraft
Altitude (feet)
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2 Pounds per square inch dial (psid)
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4 psid
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6 psid
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8 psid
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8.6 psid
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41,000
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28,875
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20,575
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14,120
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8,785
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7,345
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40,000
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28,250
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20,120
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13,750
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8,470
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7,045
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35,000
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24,980
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17,605
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11,700
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6,725
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5,375
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30,000
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21,410
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14,785
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9,350
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4,705
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3,430
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25,000
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17,625
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11,710
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6,735
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2,525
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1,230
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20,000
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13,650
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8,390
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3,870
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15,000
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9,525
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4,860
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765
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