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Thread: 77 Sierra MC-460 - Gear Problems, AOG

  1. #1

    77 Sierra MC-460 - Gear Problems, AOG

    Hi guys,

    I am hoping someone out there can help me, I had a problem with the Gear in Transition during flight. The gear motor seemed to be cutting in to try and raise the gear as it was loosing pressure. My Mechanic removed the gear motor and said it was burned out. He replaced the gear pump motor along with some O-Rings in the nose gear actuator. Now he tells me there is a problem with the pressure switch. At this rate it will be 10K before we get this bird back in the air...HELP!

    Here is what my Mechanic is telling me:

    When the new motor was installed, Pat found where the leak was in the gear hydraulic pressure system. The O-rings (3) in the nose gear actuator had worn down pretty badly and were actually the wrong thickness. Anyway, they were replaced and the gear now extends and retracts much faster than before. This is the good news. The bad news is when the gear is retracted, the pressure switch that should deactivate the gear motor when the required 1500 PSI is reached remains closed, meaning that the motor remains on. Eventually, the motor will burn out from this. This is apparently what happened to the previous motor. The bottom line is that you need a working pressure switch to resolve the problem. This is where it gets ugly. The switch assembly, now only available through Ratheyon, is $6K US. It would take about 10-14 days to get here.
    I told them to hold off on ordering such a part until I had a chance to check with some other Beech Owners.

    The Beechcraft part number 169-380099-1.
    The standard part number is PH8P-94.

    The switch by itself is part # A4403 but apparently Raytheon will not sell it that way, just the whole assembly. I have the schematic for the complete assembly and it is made by United Electric Controls, Precision Sensors Division in Milford CT. My Mechanic said he called them today directly but they said they could not sell it to him directly and we had to deal through RAPID. Another parts supplier said he sold one in October to someone and they paid approx $1300 through Rapid at that time. Now it seems the price is 5 times as much. The worst part is RAPID tells us they actually have 2 on the shelf.
    If anyone can offer a suggestion of another source for this part (certified or not) or even a used one it would be much appreciated. Basically I am not even convinced that this is the answer to all of our problems and am hesitant at this price to "try it and see". If I could get any kind of hydraulic switch that is rated 1200 - 1500 lbs then at least I would know that this is the answer.
    All I want for Christmas is a 1500lb pressure switch....
    Thanks,
    Bruce Dwyer
    77 Sierra, MC-460
    C-GMTT


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  2. #2

    77 Sierra MC-460 - Gear Problems, AOG

    When I had a case of the gear not fully raising on a long X-country
    flight,with the pump coming on repeatedly after the takeoff and retraction
    and the light had flickered red,I dropped the gear and kept them down till I
    landed on my next stop. It turned out it was a small o-ring seal on the left
    main gear Actuator.(Which is visible in the wheel well). The mechanic
    advised that if I had not dropped the gear,I could have soon burned out the
    gear motor,but it did not.He surmised the fluid had been slowly leaking
    until there was insufficient pressure to get that one gear up and locked.I
    always check the wheelwells now for a hydraulic gear fluid leak,which
    manifested itself in my case as a fine spray,invisible but sticky. The
    tipoff to the mechanic was lots of tiny little bugs stuck to the aluminum
    soffit of the left wheelwell,whereas the right wheelwell was dry,with no
    stuck bugs.
    Ray Griffin '74 Sierra C-GTTW

    -----Original Message-----
    From: musketeermail@yahoogroups.com
    [mailto:musketeermail@yahoogroups.com]On Behalf Of Wes K
    Sent: Saturday, December 24, 2005 9:40 AM
    To: musketeermail@yahoogroups.com
    Subject: [musketeermail] 77 Sierra MC-460 - Gear Problems, AOG


    Has you mechanic confirmed that the pressure switch is positively inop
    and that the up relay is not sticking closed? The pressure switch when
    activated by the high hydraulic pressure will remove the up relay hold
    power and the up relay should then open taking power away from the pump
    motor. The pressure switch opening itself does not actually remove power
    from the pump motor but only from the up relay holding circuit. If the
    up relay is sticking closed due to burnt contacts then the pump will
    continue to get power.

    Wes K

    >___
    >_________________________________________________ _______________________
    >
    >Message: 4
    > Date: Fri, 23 Dec 2005 22:48:43 -0500
    > From: "Dwyer, Bruce" <Bruce.Dwyer@gowlings.com>
    >Subject: 77 Sierra MC-460 - Gear Problems, AOG
    >
    >Hi guys,
    >
    >I am hoping someone out there can help me, I had a problem with the Gear in
    Transition during flight. The gear motor seemed to be cutting in to try and
    raise the gear as it was loosing pressure. My Mechanic removed the gear
    motor and said it was burned out. He replaced the gear pump motor along with
    some O-Rings in the nose gear actuator. Now he tells me there is a problem
    with the pressure switch. At this rate it will be 10K before we get this
    bird back in the air...HELP!
    >
    >Here is what my Mechanic is telling me:
    >
    >When the new motor was installed, Pat found where the leak was in the gear
    hydraulic pressure system. The O-rings (3) in the nose gear actuator had
    worn down pretty badly and were actually the wrong thickness. Anyway, they
    were replaced and the gear now extends and retracts much faster than before.
    This is the good news. The bad news is when the gear is retracted, the
    pressure switch that should deactivate the gear motor when the required 1500
    PSI is reached remains closed, meaning that the motor remains on.
    Eventually, the motor will burn out from this. This is apparently what
    happened to the previous motor. The bottom line is that you need a working
    pressure switch to resolve the problem. This is where it gets ugly. The
    switch assembly, now only available through Ratheyon, is $6K US. It would
    take about 10-14 days to get here.
    >I told them to hold off on ordering such a part until I had a chance to
    check with some other Beech Owners.
    >
    >The Beechcraft part number 169-380099-1.
    >The standard part number is PH8P-94.
    >
    >The switch by itself is part # A4403 but apparently Raytheon will not sell
    it that way, just the whole assembly. I have the schematic for the complete
    assembly and it is made by United Electric Controls, Precision Sensors
    Division in Milford CT. My Mechanic said he called them today directly but
    they said they could not sell it to him directly and we had to deal through
    RAPID. Another parts supplier said he sold one in October to someone and
    they paid approx $1300 through Rapid at that time. Now it seems the price is
    5 times as much. The worst part is RAPID tells us they actually have 2 on
    the shelf.
    >If anyone can offer a suggestion of another source for this part (certified
    or not) or even a used one it would be much appreciated. Basically I am not
    even convinced that this is the answer to all of our problems and am
    hesitant at this price to "try it and see". If I could get any kind of
    hydraulic switch that is rated 1200 - 1500 lbs then at least I would know
    that this is the answer.
    >All I want for Christmas is a 1500lb pressure switch....
    >Thanks,
    >Bruce Dwyer
    >77 Sierra, MC-460
    >C-GMTT
    >
    >
    >





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