737-300/400/500
MAINTENANCE MANUAL

UP AND LOCKED
IN TRANSIT
FWD
UPPER DRAGE 
BRACE 
AIRPLANE 
STRUCTURE (TYP)  LOCK STRUT  BUNGEE LOCK SPRING 

NOSE GEAR
ACTUATOR

LOCK BRACE LOCK LINK LOCK ACTUATOR
LOWER PIVOTDRAG AXISBRACE SHOCK STRUT
DOWN AND LOCKED

Nose Gear Extension and Retraction Schematic
Figure 9

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A
737-300/400/500MAINTENANCE MANUAL
 B. Extension
 (1)  When the landing gear control lever is moved to DN position, hydrualic pressure is directed to the gear and lock actuators in the opposite direction to gear retraction and a similar course of events would apply. However, with the gear up and locked, the weight of the gear applies a high compression load on the lock strut. The gear load on the lock strut plus the force applied by the pressurized nose gear actuator tends to make lock release noisy and stiff. Therefore, the transfer cylinder is used to direct down line pressure to the up side of the nose gear actuator and so equalize pressure on both sides of the piston. The pressure impulse from the transfer cylinder is supported momentarily by the flow control valves in the modular package. By this means, the main actuator extension force is reversed during the lock strut unlocking and the initial hinging of the drag brace. After unlocking, the extension cycle is opposite to retraction.
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737-300/400/500MAINTENANCE MANUAL
 NOSE GEAR EXTENSION AND RETRACTION - TROUBLE SHOOTING
_____________________________________________________
 1.  General
_______
 A.  This procedure has these observed fault trouble shooting tasks:
 (1)  
While in the Air:

 (a)  
Nose Landing Gear fails to operate, or does not operate correctly.

 (b)  
Nose Landing Gear enters Locked position with excessive force.

 (2)  
While on the ground:

 (a)  
The Airplane is on the Ground and the Red Warning Light for the Nose Landing Gear is Illuminated. The Landing Gear Control Lever is in the DN position.

 B.  
Trouble shooting the nose gear retraction mechanism requires the airplane to be jacked for nose gear retraction per Airplane Jacking, Chapter 7.

 NOTE: Be careful to not remove the chocks or do other actions that can
____ cause the nose landing gear to inadvertantly retract before the weight of the airplane is supported by the jack.
 C.  Hydraulic power from a variable flow hydraulic bench, or from the airplane hydraulic system may be used. With the airplane system in use, gear operation times and hydraulic pressure will be near normal.
 D.  Three persons are required. One stationed in control cabin to operate the landing gear control lever, one to operate the hydraulic test bench (if used) and one stationed near the nose wheel well to observe gear action.
 E.  Main gear ground lock assemblies must be installed (AMM 32-00-01), control cables correctly rigged and hydraulic reservoirs filled to correct level.
 WARNING: CHECK THAT GROUND LOCK ASSEMBLIES ARE INSTALLED IN MAIN LANDING
_______ GEAR TO PREVENT INADVERTENT OPERATION OF GEAR. INJURY TO PERSONNEL AND/OR DAMAGE TO EQUIPMENT COULD RESULT IF GEAR RETRACTS.
 (1)  If the ground lock pins are not installed on all the landing gear, do this task: Install the ground lock assemblies (AMM 32-00-01/201).
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