blaplante
Well Known Member
I am stumped. 
In the newly out of phase 1 RV, I tried a practice VOR approach with safety pilot on board. Head direct for the VOR to start. Center up the CDI needle at about 320 degrees as expected and start tracking inbound. Also have the GPS showing direct-to the VOR.
After a short time I have some CDI deflection to the left and am correcting left. Safety pilot pokes me and shows that I'm turning away from the GPS track per the Garmin! Huh? We notice that the to/from flag is showing FROM even though we are SE of the station. Eh? Eventually we discover that you can hack it if you put in reciprocal bearings. Should be 330 inbound? Put in 150 - and you get TO and correct left right needle! Whoa!
OK, let me explain the connections. I have a KX155. An output from the KX155 is the 'composite NAV' signal'. This is wired to an IN-351 (Cessna ARC) converter indicator. Now, this indicator has left/right in/out pins to allow connecting a back course relay... so if those wires were reversed, then the left / right needle would be backwards... Trouble is, that doesn't explain the similarly backward TO/FROM. And the to/from is internally generated by the IN-351. OK - my thought is, someone somehow has put the OBS dial in 180 degrees off. Rather than to try to fix that, we got another IN-351 (yellow tagged). Drop it in, and... does exactly the same thing!
Today, trying to rule out the radio, we pulled the KX155 and put it into a Cessna on the ramp. Both my radio and the Cessna's showed exactly the expected TO bearing and same course. So my KX155 is OK.
I can't understand how it can be a wiring issue... so is it possible that the composite VOR signal from the KX155 is different than the composite signal an IN-351 expects? I thought composite NAV signal is just the demodulated signal?
Hope someone can help!
Bryan
In the newly out of phase 1 RV, I tried a practice VOR approach with safety pilot on board. Head direct for the VOR to start. Center up the CDI needle at about 320 degrees as expected and start tracking inbound. Also have the GPS showing direct-to the VOR.
After a short time I have some CDI deflection to the left and am correcting left. Safety pilot pokes me and shows that I'm turning away from the GPS track per the Garmin! Huh? We notice that the to/from flag is showing FROM even though we are SE of the station. Eh? Eventually we discover that you can hack it if you put in reciprocal bearings. Should be 330 inbound? Put in 150 - and you get TO and correct left right needle! Whoa!
OK, let me explain the connections. I have a KX155. An output from the KX155 is the 'composite NAV' signal'. This is wired to an IN-351 (Cessna ARC) converter indicator. Now, this indicator has left/right in/out pins to allow connecting a back course relay... so if those wires were reversed, then the left / right needle would be backwards... Trouble is, that doesn't explain the similarly backward TO/FROM. And the to/from is internally generated by the IN-351. OK - my thought is, someone somehow has put the OBS dial in 180 degrees off. Rather than to try to fix that, we got another IN-351 (yellow tagged). Drop it in, and... does exactly the same thing!
Today, trying to rule out the radio, we pulled the KX155 and put it into a Cessna on the ramp. Both my radio and the Cessna's showed exactly the expected TO bearing and same course. So my KX155 is OK.
I can't understand how it can be a wiring issue... so is it possible that the composite VOR signal from the KX155 is different than the composite signal an IN-351 expects? I thought composite NAV signal is just the demodulated signal?
Hope someone can help!
Bryan
