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cbirdsall6(at)cox.net
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 Posted: Sat May 12, 2012 3:26 pm Post subject: KI 209A and Century I Problems |
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I have a Grumman in my shop with a Century 1 autopilot that derives its
left/right input from a KI204 or a KI209A via a 4P3T switch. The KI209A
can be switched to act as a GPS CDI from a KLN94 or as a VOR CDI.
The owner says that when the autopilot is connected to Nav 1
(KX170/KI204) it captures the radial just fine with a minimum number of
overshoots. When it's connected to Nav 2 (KX170 or GPS/KI208A), it
continually S-turns across the radial (or course line supplied by the
GPS). The owner had the 209A/KLN 94 installed about 2 years ago and he
says it never worked right from the time was installed (I'll not go into
why he didn't just take it back to them ...).
Both VOR systems indicate the appropriate course deflection when checked
with a flightline tester. When the 209A is set for GPS mode, it
displays the appropriate deflection during GPS self test (1/2 right).
I checked the wiring and switch - there is continuity between the
autopilot output of each CDI to the autopilot Left/Right input when
switched in and are open when switched out. Each of the wires are
appropriately open to ground, and there is no continuity between them.
Both CDIs put out 150mV at full scale, 75 mV at half scale, etc. The
209A also puts out the right deflection voltage when switched to GPS mode.
The only difference I noticed: The Left/Right reference voltage out of
the 209A is about 4.15 V (appropriate per the 209A maint manual), but
the reference out of the 204 is around 350mV. I could find no mention
of the reference voltage in the 204 maint manual.
The 209A manual says that the output is designed for a 1Kohm load. The
Century install manual says the input to the autopilot presents no load.
SO ... do I have a problem with one of the indicators? Do I need to
load the output of the 209A in some way? Or is there some other problem?
Thanks,
Chuck
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galsys(at)bezeqint.net
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| Posted: Sat May 12, 2012 10:23 pm Post subject: KI 209A and Century I Problems |
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you better check your Century a/p behavior instead of wasting your time
on the NAV parts!
Gabe
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