Understanding the operation of the B767's landing gear will first not be so easy. I'm presenting some of it's main, most important parts on the following pictures, to get familiar with their names and functions. (We are talking only about the main landing gear, the nose gear will be in an upcoming post.)
Turning down the LG Control lever, it opens the Main Gear Selector Valve, letting the pressurized fluid flow from the Center Hydraulic System to the LG system. The Gear Operated Sequence Valve opens the Door Latch Actuator which is first released by the Lock Out Actuator. Then it activates the Main Gear Door Actuator. The Main Gear Retract Actuator extends and turns the Trunnion which lowers the Shock Strut. The Truck Positioner Actuator tilts the gear for entry into the wheel well and operate proximity switches for the air/ground sensing systems. It makes a tilt of 17.6°. The Lock Actuators are moving the Side & Drag Lock Links into their fixed position. The Down Lock Springs assure the fixed, extended position of the LG which is ready for landing. The retraction is in the opposite order. There are some other covering panels/doors but they have no actuation.
The following pictures will illustrate these and other parts. (The Door mechanism is not illustrated on the pictures.)
|SIDE BRACE INSTALLATION|
|DRAG BRACE INSTALLATION|
Note, the Torsion Link was disassembled therefore it's hanging on a rope. Also, on the next picture the Truck Positioner is not on it's normal place, you may see it assembled on the first photo.
|LEFT MAIN GEAR LOOKING OUTBOUND|
The Down Lock Pin is used only on the ground, for securing the LG from retraction or from any other movement.
All in all you may have about 7-8 actuators which are necessary to extend/retract the LG. Namely;
- Truck Positioner Actuator
- Side Brace Actuator
- Drag Brace Actuator
- Retract Actuator
For the Door mechanism:
- Lockout Actuator
- Latch Actuator
- Door Actuator
Resources: Boeing 767 Training Manual - 1992