air/ground system.
The system receives air/ground logic signals from sensors located on the right
main gear and the nose gear. These signals are used to configure the airplane
systems to the appropriate air or ground status.
Copyright . The Boeing Company. See title page for details.
14.20.6 December 7, 2001
Landing Gear -System Description 737 Operations Manual
Air/Ground System Logic Table
SYSTEMS NORMAL INFLIGHT OPERATION NORMAL ON GROUND OPERATION REFER TO CH
Drain Mast Heaters 115 volt AC operation. 28 volt AC operation. 1
Pack Valves With one pack operating regulates to high flow with flaps up. With one pack operating, regulates to high flow only when pack is operating from the APU and both engine bleed switches are OFF. 2
Pressurization (CPCS) Allows programmed pressurization in the standby and automatic modes. Allows pressurization on the ground as determined by the FLT/GRD switch. 2
Pressurization (DCPCS) Allows programmed pressurization in the automatic modes. Allows pressurization on the ground. 2
Ram Air Turbofan(s) operate only when air conditioning packs operate and flaps are not up. Turbofans operate whenever air conditioning packs operate. Deflectors are extended. 2
Wing Anti–ice Ground Inhibited System (As Installed) Control valves open when switch is ON. Control valves do not open except during ground test. 3
Wing Anti–ice Ground Operating System (As Installed) Control valves open when switch is ON. Thrust setting and duct temperature logic is bypassed. With switch ON, valves cycle open and closed. Switch trips to OFF at lift–off. 3
Autothrottle Enables go–around below 2000 ft radio altitude. Disengaged 2 seconds after landing. Takeoff mode enabled. 4
TO/GA switch Flight director engages go–around mode. Flight director engages takeoff mode. 4
ACARS Sends out signal on strut extension for takeoff signal. Sends out signal on strut compression for landing signal. 5
Copyright . The Boeing Company. See title page for details.
December 7, 2001 14.20.7
Landing Gear -System Description 737 Operations Manual
SYSTEMS NORMAL INFLIGHT OPERATION NORMAL ON GROUND OPERATION REFER TO CH
Voice Recorder Prevents tape erasure. Allows tape erasure when parking brake is set. 5
Standby Power Standby busses automatically transferred to battery and inverter power when standby power switch is in AUTO BAT position must be selected for transfer of standby busses 6
APU Control APU operation possible with battery switch OFF. APU shutdown if battery switch is positioned OFF. 7
APU Generator May be connected to only one generator. May be connected to two generator buses. 7
Engine Idle Control Idle control and indication system is armed. Maintains high idle until 4 seconds after landing. 7
Thrust Reverser Thrust reverse disabled by gear sensors and radio altimeter. Thrust reverse enabled. 7
APU Fire Horn Wheel well horn disabled. Wheel well horn enabled. 8
Speed Brake Lever Actuator Can be armed to raise ground spoilers for landing. Activates SPEED BRAKE lever on landing if armed. Rejected take–off feature available. Drives to DOWN when thrust lever advanced. 9
Auto Slat System enabled with flaps 1, 2, or 5 selected. PTU available if system B pressure is lost. System disabled. 9
Flight Recorder Operates when transfer bus No. 1 is powered Operates when transfer bus No. 1 is powered and either engine is operating. 10
FMC Position updated from DME or VOR/DME. Does not update. 11
Transponder Enabled. On some airplanes “Reply” function deactivated when AUTO is selected. 11
Standby Hydraulic Pump automatic operation with flaps extended and A or B pressure lost. Wheel speed must be greater than 60 knots for automatic operation. 13
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