When the landing gear actuators on the King Air 90 and 200 model aircraft arrive at Duncan Aviation for their six year or 8,000 cycle overhaul, the first thing we perform is the actuator screw and nut end play inspection on each actuator assembly (two main/one nose). The end-play inspection measures the play between the threads of the screw assembly and nut assembly. A large majority of the time the nut assembly will require replacement due to extended wear.
The actuator screw and nut end play inspection should be performed every 1000 cycles or 30 months, whichever comes first. The allowable tolerance between the actuator screw and nut assembly is .016 of an inch, but the actuator can remain in service up to .018 of an inch but must be re-inspected every 200 cycles. If the inspection finds the tolerance beyond .018 of an inch, the landing gear actuators must be sent in for overhaul. Keep in mind that even if the Actuator passes the end play check at 1000 cycles or 30 months, it may not pass the more stringent end play check required by the overhaul manual. The maximum allowable end play at time of overhaul is only .009" before it must be replaced.
This nut assembly wear is caused because the nut assembly is made of a bronze material that rubs against the steel screw assembly. Symptoms of extended tolerance could be a loud noise when the LG is extended and retracted. If any foreign material were to get in between the threads, this assembly will bind up and the LG will no longer be able to extend or retract.
If you should have any questions about this, don’t hesitate to contact me. To schedule your King Air 90/200 landing gear overhaul, contact your Duncan Aviation accessories customer account rep.
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