SERVICE MANUAL & I.C.A. FOR THE 7000 AMPHIBIOUS FLOATS
Revision G Page 52 of 102 P/N 1004646 Doc. No. W7001-24-01
Note: There are three “over center” locks on the
main gear when the gear is down. The first is the
over center rod linkages that are adjusted in the
above steps. The second is from the spring pulling
on the actuator arm when the gear is in the down
position. The spring prevents the actuator from
moving in the event of a loss of hydraulic pressure.
The third comes in the form of the angle between
the oleo-pneumatic shock strut and the Top Arm
Assembly. The vector of the oleo force is “over
center” about the rotation point on the Top Arm
Assembly. Thus, one could effectively remove the
entire gear actuator, and the geometry of the Oleo
and Top Arm alone would force the contact faces of
the top arm and top mount together and lock it
“over center.”
There are also two “over center” locks when the
gear is in the retracted “up” position. The first is a
spring installed on the actuating arm that prevents
motion of the rack and pinion actuator in the event
of a hydraulic failure. The second over center lock
comes from the geometry of the gear in the up
position.
Since the retraction mechanism is driven over
center, the weight of the landing gear and oleo,
when retracted, prevent the retraction mechanism
from rotating past the over center point. The
weight of the gear wants to rotate the Top Arm
Assembly, however, when rotating the Top Arm,
the rod linkages must also move. The geometry
is such that the rod linkages are “over center” on
the actuator shaft centerline, and thus the rod
linkages are trying to rotate the actuator more
toward the UP position and hence force the
actuator piston face into the up adjustment
setscrew.
