Comobowz Posted March 30, 2021 Report Share Posted March 30, 2021 I've been searching here and other forums and not having any luck in finding a resolution to a similar issue. The KFC 150 in my Ovation isn't working at startup. I get a solid TRIM light, but nothing happens when I try the test procedure, it does absolutely nothing, no beeps/flashes, etc. On multiple occasions, it has started working after about 10 mins in to the flight, after repeated attempts at pressing the test button. When it works, it works great, but the issue is getting progressively worse, and is now repeatable every time. In one instance, pressing the red AP disconnect button on the yoke fixed it, but that no longer has any impact. If we press the CWS button on the yoke, it will cause the FD light to illuminate on the computer. @KLudwick, you've seen it multiple times, have I missed anything? Any troubleshooting ideas? Quote Link to comment Share on other sites More sharing options...
PeteMc Posted March 30, 2021 Report Share Posted March 30, 2021 Oxidation on the card edges? If you have contact cleaner, try cleaning the edge connectors on the card. If not, try re-seating them a few times. If it's not a simple bad connection take it to a shop that actually has the test gear. Quote Link to comment Share on other sites More sharing options...
carusoam Posted March 30, 2021 Report Share Posted March 30, 2021 Make sure you remember to turn the electric trim switch on... My first lesson with the KAP150... If you turn the trim switch off... it magically becomes a problem on start-up... My check lists didn’t follow the extra steps to turn this CB off and back on again... So when I turned it of because it seemed to be the right thing to do... it really wasn’t... Best regards, -a- 1 Quote Link to comment Share on other sites More sharing options...
Comobowz Posted March 30, 2021 Author Report Share Posted March 30, 2021 8 hours ago, carusoam said: Make sure you remember to turn the electric trim switch on... My first lesson with the KAP150... If you turn the trim switch off... it magically becomes a problem on start-up... My check lists didn’t follow the extra steps to turn this CB off and back on again... So when I turned it of because it seemed to be the right thing to do... it really wasn’t... Best regards, -a- boy do I wish that was it! I learned that lesson on my 2nd flight. I no longer turn off the trim CB on shutdown. Appreciate it. 1 1 Quote Link to comment Share on other sites More sharing options...
Comobowz Posted March 30, 2021 Author Report Share Posted March 30, 2021 9 hours ago, PeteMc said: Oxidation on the card edges? If you have contact cleaner, try cleaning the edge connectors on the card. If not, try re-seating them a few times. If it's not a simple bad connection take it to a shop that actually has the test gear. This will be my first time pulling out the KC 192. Is the card obvious in the back of the unit, and it just pulls out? I have seen a photo somewhere on MS before of what that looks like but unfortunately I can't find it anymore. I just want to make sure that I don't make things worse! Quote Link to comment Share on other sites More sharing options...
Jake@BevanAviation Posted March 30, 2021 Report Share Posted March 30, 2021 (edited) Depending on the manufacture year of the computer it could be a unit that has capacitors leaking in the power supply (94-98). This cap leakage can corrode traces or even open up traces for the power supply circuit and voltage monitor circuit. Typically when this happens you get some interesting PFT results or the unit will not PFT. As the unit warms up or cools down it will randomly decide to work. This condition will only get worse over time. If the computer is working properly with sufficient power to the trim monitor circuit (NOTE: if there is no voltage to the trim monitor circuit the unit will not flash trim during PFT) when hitting PFT the unit will flash trim 4 times. . Two up trim pules and two down trim pules, the computer looks for feedback and does some other internal test with the microprocessor. If the test are successful the unit will flash AP approximately 12-14 times. Also, on a side note pay attention the the left side of the MET rocker switch if it is not in a neutral position it can cause the PFT to fail. If you are going to remove the unit from the rack use a 3/32 allen tool for the removal screw and be sure to remove the static line to the transducer on the back of the unit before pulling it all the way out. On the unit there should be a red 4 digit stamp (1497) the 14 is the week and 97 is the year. Check to see if you fall in the year range listed above for cap leakage. Edited March 30, 2021 by Jake@BevanAviation 2 Quote Link to comment Share on other sites More sharing options...
PeteMc Posted March 30, 2021 Report Share Posted March 30, 2021 1 hour ago, Comobowz said: This will be my first time pulling out the KC 192. Is the card obvious in the back of the unit, and it just pulls out? I have seen a photo somewhere on MS before of what that looks like but unfortunately I can't find it anymore. I just want to make sure that I don't make things worse! So at this point... I'd say go to a shop. A few bucks there could save you a lot if you break something due to an "oops" moment. I don't know on your unit, but there could be little lock tabs or the cards could be held in place when you put the cover on. My only thought on the oxidation was that it often can be an easy check/fix in older gear IF you don't break something in the process. Quote Link to comment Share on other sites More sharing options...
Comobowz Posted March 30, 2021 Author Report Share Posted March 30, 2021 Just now, PeteMc said: So at this point... I'd say go to a shop. Agreed....I'm going to have my shop look at it. For issues like this they are generally fairly quick and they are here on the field. Quote Link to comment Share on other sites More sharing options...
ZuluZulu Posted March 31, 2021 Report Share Posted March 31, 2021 You might find value in a phone call with @Bob Weber, who has been recommended on this forum and others numerous times. I have not used his services myself and have no financial stake, but if it were me I would certainly call him if I needed help with my autopilot. https://webairconsulting.com 2 Quote Link to comment Share on other sites More sharing options...
Bob Weber Posted March 31, 2021 Report Share Posted March 31, 2021 On 3/29/2021 at 9:54 PM, Comobowz said: I've been searching here and other forums and not having any luck in finding a resolution to a similar issue. The KFC 150 in my Ovation isn't working at startup. I get a solid TRIM light, but nothing happens when I try the test procedure, it does absolutely nothing, no beeps/flashes, etc. On multiple occasions, it has started working after about 10 mins in to the flight, after repeated attempts at pressing the test button. When it works, it works great, but the issue is getting progressively worse, and is now repeatable every time. In one instance, pressing the red AP disconnect button on the yoke fixed it, but that no longer has any impact. If we press the CWS button on the yoke, it will cause the FD light to illuminate on the computer. @KLudwick, you've seen it multiple times, have I missed anything? Any troubleshooting ideas? There are several things to check here that will narrow down the search. The install in your Ovation should have a small "B" nut for the static connection just above the copilots left toe. Does this failure act the same as leaving the trim master off? Give me a call if you would like 616 822 1999, and we can put this issue in the rear view mirror quickly. A couple pictures of your instrument panel with pilots yoke could tell me something, an hour or two guiding you or your maintenance shop with a volt meter will determine the likely culprit. Bob Weber Autopilot consultant webairconsulting.com 3 Quote Link to comment Share on other sites More sharing options...
LANCECASPER Posted April 2, 2021 Report Share Posted April 2, 2021 On 3/30/2021 at 9:00 AM, Comobowz said: Agreed....I'm going to have my shop look at it. For issues like this they are generally fairly quick and they are here on the field. I hate to say it, but unless your shop is an expert at KFC150 autopilots, most likely they will only make it worse, making it harder to figure out the underlying problem. Some time on the phone with @Bob Weber would be worth it. And since you are in the midwest a run over to Wichita to Bevan @Jake@BevanAviationcould save you a lot of time and money. 2 Quote Link to comment Share on other sites More sharing options...
Comobowz Posted April 3, 2021 Author Report Share Posted April 3, 2021 So a little update, shop pulled the computer, tested the voltage on the trim servo which was good, put the computer back in and it's running like a champ. I've flown the last 2 days, tested great, and no issues thus far. 1 hour yesterday, two 2-hour cross countries today and no issues. Will update if there is any change, but thus far working well. 3 Quote Link to comment Share on other sites More sharing options...
carusoam Posted April 3, 2021 Report Share Posted April 3, 2021 Great follow-up Como! Best regards, -a- Quote Link to comment Share on other sites More sharing options...
PT20J Posted April 3, 2021 Report Share Posted April 3, 2021 The King equipment of this vintage uses PCB edge connectors to mate the unit to the connectors in the tray. I’ve had several where the beryllium-copper contacts in the socket had lost some spring and were not making good contact - especially if work had been done on the connector. This caused intermittent issues with a KC 191 and a KX 165. A long screw driver with a small cabinet blade tip to gently coax them to make better contact with the edge connector cured it. Skip Quote Link to comment Share on other sites More sharing options...
Bob Weber Posted April 4, 2021 Report Share Posted April 4, 2021 Two words... Stabilant twentytwo 1 1 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.