KMD 550 self-test error, airworthy?

Discussion in 'Avionics and Upgrades' started by arnoha, Nov 30, 2017.

  1. arnoha

    arnoha Line Up and Wait

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    What to do, what to do...

    I have a 172S with a KLN 94/KMD 550 combination. The KMD 550 complains during self-test that one of the panel LEDs doesn't work. It's a spurious error: all the LEDs work perfectly. Every other aspect of the device works great. It's flown this way for years now, without a single complaint from any mechanic looking at the aircraft or this issue. Everyone has signed it off as airworthy.

    Until now. The GM for the club it's on leaseback with wants it placarded in-op due to this. Everyone else has read the indication as spurious and that the device is actually working perfectly. This GM wants a stricter reading where this indication requires the thing pulled.

    Fixing the issue directly is about $5K. That would be a silly amount of money to spend on this ancient tech. Better to save it for a later GTN install. But am I really stuck with making that later now?
     
  2. bnt83

    bnt83 Final Approach

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    Can avionics shop reload the software? Maybe the issue will go away?

    Picking fly **** out of pepper on this one. The GM must not deal with avionics much.
     
  3. mtuomi

    mtuomi En-Route

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    Another "club GM" who is happy to waste other peoples money.
     
  4. bradg33

    bradg33 Cleared for Takeoff

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    The KMD500 is just "Advisory" anyway, isn't it? The primary navigational device is the KLN94 and its associated CDI. I'd be a little concerned if the GPS itself were giving error messages, but just the MFD? No reason at all to inop it, IMHO.
     
  5. arnoha

    arnoha Line Up and Wait

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    That's what everyone else has basically said. I'm kind of at a loss as to how to proceed. His claim was that the FAA will have a field day when they see that the squawk has been opened by numerous renters and always closed with a "won't fix, fit for flight". And that the FARs require it rendered inop.

    Do I have any precedent that this won't happen? That the FAA won't have a problem with it?
     
  6. bradg33

    bradg33 Cleared for Takeoff

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    It's non-essential, non-required equipment and (presumably) a mechanic has determined it's still airworthy. Sure, it's possible some over-the-top FAA inspector might take you to task over it, but if they're going to do that, they were going to get you on SOMETHING anyway. And tell the renters to stop writing it up!

    The meaningfulness of a "squawk" from a renter is questionable anyway. The regs are a little fuzzy on whether it actually requires any corrective action or a "return to service" by an A&P. It's really up to each individual renter to decide if the airplane is airworthy; what one renter thought was an issue doesn't necessarily bind the next one. Look at it this way: if Renter A squawks a V-tail Bonanza with "vertical stabilizer missing," does that really constitute an open "squawk" that requires any sort of formal resolution before the plane is flown again?
     
  7. JAWS

    JAWS Line Up and Wait

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    No MEL Inoperative Equipment Flowchart:

    [​IMG]
     
  8. arnoha

    arnoha Line Up and Wait

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    Certainly aware of that chart, but by my rendering, it should be airworthy, as it doesn't pass the very first box: every pilot who's flown the aircraft so far has recognized the equipment as operative.
     
  9. Axtel4

    Axtel4 Pre-takeoff checklist

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    Do you have the exact verbiage of the fault message? My recollection is the LED fault message means the Self Test routine detected an issue with one of the LEDs that illuminates the "Power Key"nomenclature. These are the "hard key" buttons along the right side of the bezel. The nomenclature is context sensitive and illuminates in coordination with the Menu buttons along the bottom of the display. Illumination of the nomenclature will depend on what optional modules are installed in the KMD 550.

    If an LED has failed, the failure may not show up until the Menu button is selected that calls the associated "Power Key" into focus. For example, if the "AUX" menu is selected, none of the Power Key nomenclature is illuminated and button function is transferred the "Soft Key" menu along the side of the LDC display. If the MAP function is displayed, only the RNG/\ the RNG\/, and the OVLY nomenclature is illuminated. You could step through the Menu selections and see which Power Key nomenclature illuminates. If you find one that doesn't illuminate when invoked then there is a hard failure for that LED.
     
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  10. BigBadLou

    BigBadLou En-Route

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    I agree, the MKD, from FAA's perspective, is just a toy. Not approved for navigation and only advisory only, as pointed out.

    Sooooooo, to save you $5k, don't replace the KMD ..... replace the GM. Problem solved. Now send me the $5k for my consultation fee. ;)
     
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  11. arnoha

    arnoha Line Up and Wait

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    This is actually the best explanation I've seen for this problem! I think all the LEDs light: every one I believe should exist lights during the startup sequence, as they light in order. But I'll check on that again. Do you have a reference for every one that should exist?

    Part of the issue is that the KMD 550 in the 172S only uses one page. No traffic, no weather, no nothing. Just moving map and some info. So there may be LEDs that don't every light up in this application, but are a part of the self-test.
     
  12. Axtel4

    Axtel4 Pre-takeoff checklist

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    Here is an image of the unit in Map mode captured from the Pilots Guide.

    KMD550 Map Mode.JPG

    The information on which Power Keys go with with Menu selection should be in the AFMS (Airplane Flight Manual Supplement) if added to the aircraft after manufacture, or in the AFM (Airplane Flight Manual) included at the time the aircraft was manufactured.
     
  13. arnoha

    arnoha Line Up and Wait

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    I'll have to look next I'm in the plane. I know the two RNG LEDs light up. All the bottom ones light up. I think OVLY does, but I could be wrong as I never use that function. The avionics guys that have looked at it also believe it's the self-test itself that's busted, but I'll double-check with this info. I wonder if I can solve it with just an LED soldered into the board?

    EDIT: regarding that, if I do correct it myself, who's allowed to sign it off as airworthy?
     
  14. Paulie

    Paulie Line Up and Wait

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    If the cost of renting the airplane is not affected by not having this non-essential piece of equipment working, I would stick a inop sticker on it and pull the breaker to shut the guy up while it's in the rental mode.