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Landing Gear rigging issue

I've got a 2002 A36 that is giving us trouble. The inboard gear doors started drooping after landing. After following the guidance in the ABS landing gear rigging guide, we ended up installing a new motor. (Brand new) With the plane on jacks and on a 28V GPU, the doors close perfectly. When we fly the plane, they sag. We've adjusted the rigging and again on jacks with GPU, the doors close tight. On battery power only they close softly. We just put a factory rebuilt engine in the plane and found the alternator drive coupling may have been slipping on us so with the new engine we installed a new coupling thinking if we have lower volts in flight, this would help. Same problem. On takeoff and climb we have 28.2 volts showing which is about the same as we get on the GPU. The think the doors are staying open in flight as we've noted a speed loss. Thoughts????

Model: Bonanza A36
Aircraft Serial Number: E-3462
Posted 9/29/2022 - 2 months ago
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You are likely dropping voltage during operation. On jacks / in the shop, check voltage value on the red and white wires on the dynamic brake relay during gear operation. If both low, check the input wire (G1A10) voltage during gear operation.

Wiring diagram attached.

Mike
ABS Tech Advisor

attachment

32-31-01 (Printed data must not be retained for future reference.).pdf - 431.2 KB

Posted 9/29/2022 - 2 months ago
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We will check that. But are you thinking it might be losing voltage through the dynamic braking relay since we’ve already changed the motor?

Posted 10/1/2022 - 2 months ago
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With a proper power supply on, bus voltage on your G36 will be 28.5. You should have a 28.5 volt drop across the motor, but should not have a measureable drop anywhere else. This is why one should systematically check for a voltage drop across all components. Chances are good it will be in the area of the dynamic brake / motor / grounding under the spar cover, but if your input to the relay drops below bus voltage during operation, it may be a compromised wire, circuit breaker, or selector switch. This needs to be checked during gear operation, not static, as the current draw through the defective portion (that should have no resistance) will cause the noted voltage drop.

For example, with the leads on the test voltmeter attached to Terminal D and C3 of the relay (on the wiring diagram I posted) and during operation there is a voltage indication (i.e. voltage drop), that would indicate resistance in wire G2B10. Whatever voltage you read is subtracted from bus voltage. So, if you read 3 volts, subtract that from the 28.5 power supply to get 25.5 volts available to the motor - not enough to get the full-travel of the gear.

Posted 10/1/2022 - 2 months ago
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Landing Gear rigging issue