Landing Gear System Controls and Indicators .1 Landing Gear Lever

A landing gear lever (seeFigure 2-55) is located on the left side of the copilot instrument panel. It is a two-position (UP, DN) lever that directs the gear actuating mechanism to raise or lower the nose and main landing gears. When the lever is moved to the UP position, a solenoid-operated selector valve directs pressure from the utility hydraulic system to release the nosegear downlock, to the up side of the nose landing gear actuating cylinder, to both main landing gear hydraulic motors, and the landing gears retract. When the lever is moved to the DN position, the nose landing gear uplock is released, the main landing gear motors are reversed, and the landing gear extends. The valve circuit is powered by 28-Vdc from the essential dc bus, through the LANDING GEAR CONTROL circuit breaker on the copilot lower circuit breaker panel. A mechanical locking device is engaged when the landing gear lever is moved to the DN position so that the lever stays in the DN position until released. During takeoff or in flight, the energized position of the touchdown relay energizes the landing gear lever release solenoid to reduce the locking device to a simple detent. At other times, the LOCK RELEASE finger latch (seeFigure 2-55) must be pulled down before the landing gear lever can be moved to the UP position. When the landing gear lever is in the UP position, 28-Vdc power is routed from the LANDING GEAR CONTROL circuit breaker on the copilot lower circuit breaker panel to energize the normal brake selector valve to prevent application of normal brakes. When the landing gear lever is in the DN position, the normal brake selector valve is deenergized to allow brake application regardless of main landing gear strut compression. Seeparagraph 2.13for interrelation of antiskid provisions.

2.10.3.2 Main Landing Gear Touchdown Switch

A touchdown switch is installed on the lower aft side of each forward main gear strut. The switches are safety devices that either prevent some aircraft system from operating or permit it to operate when the aircraft is on the ground or in flight. The weight of the aircraft on the gear operates these switches.

Some systems are wired directly through the touch-down switches and others through relays that are controlled by the touchdown switches. Systems that are affected by the touchdown switches and relays are as follows:

1. Touchdown switch.

c. Cockpit controls for cargo door and ramp (inoperative on the ground).

d. Airdrop release (inoperative on the ground).

Figure 2-53. Main Landing Gear System

Figure 2-54. Nose Landing Gear System

Figure 2-55. Landing Gear Controls and Indicators

3. Auxiliary touchdown relay No. 1.

a. Dc bus tie control (inoperative in flight).

b. APU door control (door opens 35_ on the ground and 15_ in flight).

c. TCAS(enables test on ground).

4. Auxiliary touchdown relay No. 2.

a. Autopilot trim monitor test (inoperative in flight).

b. TCAS and transponder computers.

5. Auxiliary touchdown relay No. 3.

a. Ground/anticollision/strobes.

2.10.3.3 Emergency Engaging Handle

A yellow emergency engaging handle is located on the forward wall of each wheelwell, just below the landing gear manual operation stub shaft. The handle operates a cable that disengages the main landing gear mechanism brake and the drive motor, and simultaneously engages the mechanical linkage that connects the stub shaft to the gearbox, thereby permitting manual raising or lowering of the main landing gear. The handle must be pulled out and turned counterclockwise approximately one-quarter turn to lock before the landing gear can be extended or retracted manually. To restore the system to normal, the handle must be turned approximately one-quarter turn clockwise to unlock, and then be released to the normal position. Proper positioning of the emergency engaging handle is verified by rotating the handcrank in both directions. If the handle is in the normal position, the handcrank will rotate freely.

2.10.3.4 Landing Gear Handcrank

Two landing gear reversible ratchet-type handcranks are provided for the manual operation of the main landing gears.

One handcrank is stored in retaining clips on the forward face of the left wheelwell, and the other is stored on the fuselage wall forward of the right wheelwell. One end of each crank is made to fit over the protruding end of the extension stub shaft located on each wheelwell forward wall, just above the emergency engaging handles. The handcrank also fits the landing gear access panel bolts.

2.10.3.5 Main Landing Gear Emergency Extension Wrench

The emergency extension wrench is provided for manual extension of the main landing gear if both the normal and emergency extension systems fail to extend the gear. The wrench has a fixed splined socket on one end and a ratchet and splined box on the other end. The wrench is used to manually rotate the landing gear ball screws to lower the struts. The wrench is stowed in a bracket located forward of the left main wheelwell area.

2.10.3.6 Main Landing Gear Ground Lock

Two main landing gear ground locks are provided to prevent accidental retraction of the main landing gears while performing maintenance on the gears. The locks are installed on the hexagonal ends of the main landing gear ball screw assemblies, one lock on each side of the aircraft. The locks are stowed in the miscellaneous equipment box aft of the right paratroop door.

2.10.3.7 Nose Landing Gear Ground Pin

A nose landing gear ground pin (seeFigure 2-56) is provided to prevent accidental retraction of the nose landing gear while the aircraft is parked. The ground pin consists of a ball-lock pin that is inserted in a hole in the nose landing gear actuator rod-end and prevents release of the internal downlock in the actuator.

2.10.3.8 Nosegear Emergency Release Handle

A nose gear uplock emergency release handle (seeFigure 2-57) is located below the floor of the flight station under a hinged panel between the copilot seat and the control pedestal. The handle operates a cable system that releases the nose landing gear uplock and allows the nosegear to fall free.

Note

Practice extension of the nose landing gear with the emergency release handle and auxiliary hydraulic system is not recommended and should be avoided. Extending the nose landing gear by this method and subsequently raising the gear can cause approximately one quart of hydraulic fluid to transfer from the auxiliary hydraulic system to the utility hydraulic system.

2.10.3.9 Landing Gear Warning Horn and Silence Switch

The landing gear warning horn is located above and to the left of the pilot seat. Two things will cause the landing gear warning horn to sound: retarding a throttle to a position within 5_ forward of the FLIGHT IDLE position with the landing gear up, and extending the flaps more than approximately 80 percent with the landing gear up. A HORN SILENCE switch (seeFigure 2-55) is located on the landing gear control panel. It is a press-type switch used to silence the landing gear warning horn when a throttle is retarded. It will not silence the horn when flaps are extended more than 80 percent. When the switch is pressed, the horn-silencing relay is actuated and the warning horn electrical circuit is broken. Cycling of the landing gears or advancement of an engine throttle will reset the horn-silencing relay so that the horn can sound again. The landing gear warning horn circuit is energized by 28-Vdc power from the essential

dc bus through the LANDING GEAR WARN LIGHT circuit breaker on the copilot lower circuit breaker panel. After C-130 AFC-368, audible alarms from the Bleed Air Duct Overheat Detection System are interfaced with existing landing gear warning horn. An audible alarm from the ODS would pulse the horn at a rate of 90 times per minute to distinguish it from the landing gear warning.

2.10.3.10 Landing Gear Warning Light and Warning Light Test Switch

The landing gear warning lights are connected to the landing gear retraction system and the throttle warning switches;

they will illuminate whenever the landing gear is not in a locked position or when an engine throttle is retarded to within 5_ of the FLIGHT IDLE position and the landing gear is not fully extended. A HANDLE LIGHT TEST switch (seeFigure 2-55) is located on the landing gear control panel. It is a press-type switch used to test the continuity of the landing gear warning light electrical circuit. When the switch is pressed, the landing gear warning light bulbs in the landing gear lever handle will illuminate. Failure of the bulbs to illuminate shows a defective circuit. The landing gear warning lights are energized by 28-Vdc power from the essential dc bus, through the LANDING GEAR WARN LIGHT circuit breaker on the copilot lower circuit breaker panel.

2.10.3.11 Landing Gear Position Indicators

A left main gear position indicator, a nosegear position indicator, and a right main gear position indicator are located on the landing gear control panel (seeFigure 2-55). These indicators give a visual indication of position of the landing gear. When the letters UP appear on the face of an indicator, it means that the gear represented by that indicator is retracted and locked. When the picture of a landing gear wheel appears on the face of an indicator, it means that the landing gear represented by that picture is extended and locked. Diagonal lines on the face of an indicator indicates that a gear is somewhere between the extended and retracted positions or that the indicator is inoperative. The landing gear position indicators are energized by 28-Vdc power from the essential dc bus, through the LANDING GEAR POSITION IND circuit breaker on the copilot lower circuit breaker panel.