RG gear issues

Dan Thomas said:
Section 2 of the Service Manual has the inspection details in the last 10 or 12 pages or so. One of those items will be a check of the motor brushes, with a note number that leads you to the notes section giving more detail. One model of motor, IIRC, wasn't easily opened up without taking it right out and maybe sending it for service. The other type is easily inspected by removing the top cap and getting a look at the brushes. Gotta have at least the right front seat out. There are other inspections, too, that are usually ignored; the self-relieving check valve filter, the pressure switch cutoff point, the main and thermal relief valve pressure settings. It all takes time, it all costs money, and if ignored long enough it can add up to serious difficulty and expense. Chapter 5 (landing gear and hydraulics) is a long chapter and details all of the stuff that needs checking.
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The powerpack is in the tailcone on all 177RGs.
 
BigBadLou said:
IIRC, that is not normal.
The gear pump should not run on the ground. The nose gear squat switch prevents that.
Correct me if I am wrong, please.
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You're right that the solenoid relay should never close on the ground due to power in the circuit, even if the pressure falls, because of the squat switch. The pump only runs momentarily the moment the master is switched on, and then only very rarely, so I wonder if the solenoid relay (contactor) might occasionally move to the closed position when the system is powered off.

Of course it's also possible that I have a flaky squat switch that sometimes doesn't open the circuit when it should - in fact, I strongly suspect the squat switch is the problem causing the gear retraction failure, but it's sticking open instead of closed.
 
Dan is spot-on in describing the solenoid operation. Power to the solenoid (providing power to the pump) is controlled only by the squat and the pressure switches. (I have a 75 Cardinal RG but also have the 76 manual). I would give the squat switch a thorough check. Check squat switch and squat switch adjustment. It's in the upper scissor of the nose gear and, when the gear is extended, makes contact with the nose gear "inner barrel". This action closes the switch. When on the ground with the nose strut collapsed, the squat switch plunger should extend .055 +/- .005 inches. If you have the plane jacked, try moving the nose gear around, push it up, wiggle the wires, etc., to see if you can get the system to fail. Could be it is out-of-adjustment and barely contacting, the wires making intermittent contact - the airstream coming into play.
 
noahfong said:
Dan is spot-on in describing the solenoid operation. Power to the solenoid (providing power to the pump) is controlled only by the squat and the pressure switches. (I have a 75 Cardinal RG but also have the 76 manual). I would give the squat switch a thorough check. Check squat switch and squat switch adjustment. It's in the upper scissor of the nose gear and, when the gear is extended, makes contact with the nose gear "inner barrel". This action closes the switch. When on the ground with the nose strut collapsed, the squat switch plunger should extend .055 +/- .005 inches. If you have the plane jacked, try moving the nose gear around, push it up, wiggle the wires, etc., to see if you can get the system to fail. Could be it is out-of-adjustment and barely contacting, the wires making intermittent contact - the airstream coming into play.
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Yup. The problem is that I don't own jacks (nowhere to store them safely in the community hangar) so I'm dependent on the local mechanic, who is out sick and likely to be out for at least another week. I caught him in briefly last week though, and asked him what he did in March when this first happened. He claims that he tested the squat switch thoroughly, wiggled the wire leading to it, and could not get the system to fail after at least 20 gear swings. So I'm kind of at a loss as to how to proceed, short of getting someone else to look at it, or just replacing the switch.

Another possibility that has been suggested is to clean up the pressure switch, though the pressure switch is not subject to the airstream and so seems less likely to me as a possible culprit, since the problem appears to be impossible to reproduce on jacks. I might do that before sinking money into a new squat switch. The real problem is how rare an occurrence these failures are at this point. Until they start happening on a more regular basis, I suspect I'm not going to have any luck figuring it out.
 
I just checked the squat switch placement on my cardinal. The "plunger" extends, by rough estimate, about 1/16 inch. Somewhat close to 0.055". (I had nothing with which to do a precise measurement). With the airplane on the ground, it is easy to visually inspect. Next time you're there, you may wish to take a quick look, if you already haven't.
 
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