Jake@BevanAviation

@Brad Reid If the system will engage with FD and ALT hold only and when selecting a lateral control mode like heading, nav, approach the system disconnects. I would check the compass valid input to the computer. If the compass valid fails and you have a lateral control mode selected it will instantly disconnect the system. It will not allow you to engage the system with a lateral control mode if the compass valid has failed.

Will need to replace the Aspen with a G5, GI275, or G3x system for the GFC500 autopilot. If you are wanting to keep the Aspen your choices drop down to Aerocruze 100, S-Tec 55x/3100. Also, is the navigator a GNS430W? You might have some limitations if the GPS navigator is not WAAS.

GI-275 ADAHRS+AP units work just fine with the KAP and KFC 150 series autopilots. The KAP will not have flight bars and there is no alt preselect functions with a GI-275. You must follow the alignment procedure outlined in the GI-275 IM when interfacing with the King autopilot. We have done this interface multiple times on various airframes and no issues. Make sure whoever is the installing shop knows this interface, has the KTS158 or has built the breakout harness in the GI-275 IM before, and has done the alignment to the flight computer.

Lamps are the T-1 mini series. They are soldered to one of the motherboard assemblies behind the bezel. You have to remove the front bezel and remove both motherboard assemblies to gain access to the lamps. Just don't break any pins off the sockets.

@FLYFST With Century Flight Systems being out of business the support for Century autopilots systems is dropping off pretty fast unless someone has a supply of parts. The problem with the Century 21, 31, 41, and 2000 is there are not many used units and some of the parts I could only get from Century. For example, if it is an altitude hold issue with the Century 2000, I have no new transducer parts and no new board assemblies with the revised alt hold transducer. I have fixed some for other customers but I had to have a working parts unit. Some times you can get lucky and find a unit on eBay or a salvage yard. However, the C2000 is voltage specific and there were several revisions to the board assemblies. What issue are you having with your C2000 system?

The Century 21 MM calls has the IC listed as a MC14016BCP (quad analog switch) or a Century PN of 48S114.

Originally the 1k 5% 1w load resistors are only used on the Century 4, 41, and 2000 systems. See note below. Service Bulletin 23096 has revised this note and added the Century 21. The latest version of the GI275 IM has this revision included. If you can measure the heading error voltage when the system stop responding, move the heading bug and see if you still see a voltage change. The heading bug error voltage should go above and below the reference voltage. Reference voltage should be around 4.8VDC (half of regulated DC supply 9.6). If the heading error will still change with input the problem is not with the GI275. With Century Flight Systems being out of business support for any legacy system is going to be very limited. As parts continue to diminish there will be even less support in the future. The Century 21, 31, and 41 used a gate IC that was used to route error signals on the motherboards. If the gate fails the signal stops at that component. They also used ribbon cables to interconnect the motherboard assemblies. The ribbon cables will delaminate over time and can cause issues as well.

Yes, you would want to use the bracket that is in your aircraft for servo mounting. Just be sure that the servo dash number matches the one you have. Some servos are voltage specific 14 or 28.

Possible issue in the KC191 flight computer or roll servo. If you can gain access to the roll servo and disconnect it from the ship you could monitor to drive command across pins D and L at the roll servo connector to the ship. With a DC volt meter the AI spooled/level, the heading/course pointer under the lubber line, and the autopilot engaged in heading and AP engage modes you should see close to 0vdc. Moving the heading bug left and right of the lubber line should create a increasing DC drive voltage. Going one direction will be positive voltage and the other direction would be negative voltage. This will check the drive voltage from the computer. If you check Pins E to C this is the solenoid engage voltage. It will go positive and stay positive when the flight computer is engaged. It would also be helpful if you could find out what servo version you have. Some Mooney's have the KS-17X series of servos, other have the more common KS-27X series. Both servo assemblies function exactly the same but the KS-17X have different parts and some a getting hard to find.

The autopilot configuration page should be set for KI525 and at default values, the flight director page should be set for KI256 and at default values. The GAD43 gyro emulation type should be KI256. You need to align the flight computer to the GAD using the GAD output test. You should follow King installation bulletin 430 using the King flight line test set (KTS 150). If the KTS150 is not available you can fabricate a breakout harness. The GI275 IM shows how to make this harness if needed.

We had this happen before. Turned out to be the GSU25 had a issue.

I would check the output of the transducer inside the flight computer if the aircraft was here. You can remove the static line to the flight computer and attach a hose to the unit. When applying pressure or vacuum to the hose the computer should respond in the opposite direction. For example with a level attitude source or the ADI unplugged. If you applied pressure to the static line the computer should want to climb to get back to target altitude. If you create a vacuum the system should want to descend to get back to target altitude. You can do this with your mouth as the system is very sensitive to pressure changes. This would test to see that the transducer assembly is functioning. NOTE: there is a interlock circuit in the computer that if there is an issue with alt hold it will not allow you to select the mode and you will not get the annunciation of ALT on the bezel.

@Wingover There is a small dc motor that is attached to the drive motor inside the servo assembly. It provides negative feedback to the computer to tell it the direction of rotation and how fast. If the tach feedback motor is inop the servo will end up over driving causing a 1-2hz oscillation. Sounds like you might have a pitch servo issue. If part of the transistor bridge fails it will cause a hard pitch over or no drive in one direction. You can test this by using the UP/DOWN rocker in the computer to change the pitch attitude. You should be able to set a climb or descent attitude and the computer hold that attitude. When activating alt hold the computer takes the attitude information and the output of the altitude transducer to maintain a selected altitude.

@Wingover A slow drift, a oscillation, hard pitch up or down? If you have a video of the issue maybe that would help. Most common issue for a slow drift would be servo startup voltage, a 1-2 hz oscillation would be failed tach generator, a hard pitch up or down would be failed transistor drive.

Altitude hold information comes from the transducer that is internal to the KC192/KC191. Can you give more detail on what issue you experienced with alt hold in flight?

Base unit GI275's can be purchased over the count and installed by a AP. ADAHRS and ADAHRS+AP units need to be purchased via a Garmin dealer. Base units are typically used for CDI, MFD, HSI, EIS functions. They do not have the second connector that is used for legacy autopilot interface and do not have ADAHRS functions.

I would have someone listen to the motor speed when operating the trim system on the ground. If the motor is slowing down I would expect a increased load on the servo. If the load is too much eventually the slip clutch would start to slip. When was the last time the trim controls were inspected and lubed? Running trim by hand do you notice a area where there is increased friction? The servo would have to work against the increased load when using MET (manual electric trim). We have seen several Mooney's where there was excess friction causing the trim drive to slow when using MET. Cleaning and proper lubrication of moving parts tends to resolve this issue. If the motor speed doesn't slow I would expect a problem with the slip clutch assembly. I can tell you what the slip clutch torque limit should be if I have the model and SN of the aircraft. There is a slight possibility that there is a issue with the voltage regulator in the trim servo. Normally if the voltage regulator is soft the trim servo drive is very slow or INOP.

New GI275's come with a 10 hour trial of SVT. If you like it and want to add it there is a unlock that is needed. GI275's do a lot more vs G5 and interface with more equipment vs G5. Depending on the equipment in the aircraft the GI275 could have a advantage over the G5.

Make sure the installation shop you choose knows how to do the alignment to the KAP150. The process is outlined in the Garmin IM for the GI275 when interfaced to the KAP/KFC 150 system.

The only approved display replacements are the mod kits produced by Honeywell that change the old gas display to a led. Honeywell, continues to increase the price of this mod kit so it has become more costly to fix these units. We have had very few issues with the LED mod by Honeywell. There is another person that advertises an OLED replacement. However, this is not an approved mod, if you choose to do this good luck getting someone to sign off on the radio if it would need any future repairs. We have seen a couple of them come in and we have rejected the units due to no service data being available. The frequency knob issue is pretty common as these units continue to age. It is fairly easy to replace pending the parts are available and the repair shop knows what they are doing. With the repair cost increasing more people are replacing the units with new modern radios. The GNC215 by Garmin is a good option and you can buy them over the counter. We have installed several of them in multiple aircraft with no issues. The KX200 is advertised as the replacement to the KX155., but we have yet to see one in the wild. I have heard that the unit are finally available after being talked about for a couple of years. We still repair the KX155 units and have the LED mod kit available. The thing that really makes the units non repairable is when they have capacitor leakage and it spreads damaging multiple circuits in the radio. This capacitor issue is more common in units manufactured between 1991 and 1998.

@Guillaume see attachment. 006-00396-0000_4.pdf

With the A/P engaged and the A/P lever switch in the up position on the KC290 control head, the lateral axis and the pitch axis should have the controls locked in place if you try to move the yoke. The controls are locked when the solenoids in the servos latch. The solenoids should latch when the autopilot is engaged. With a KFC200 system there is a single solenoid engage voltage that is sent out of the computer and paralleled to all the solenoid's. Do you happen to know if you have the 100 series servos or the 200 series servos? Inside the KC295 on the power supply board are two transistors that develop the solenoid engage voltage. These transistors can fail and there is a very small trace that runs down the edge of the board that can open with high current pull. I would have the avionics tech look at the system interconnect and verify the engage voltage from the computer. If the engage voltage is there and the solenoids are latching the next check would be the slip clutch in the servo capstan and the bridle cable tension to the push rod/bell crank.

Just as a FYI this is not an approved mod from the MFG. We have seen a couple over the years and we will not even attempt to do a repair as the unit is modified outside MFG specs and no longer matches any approved documentation from the MFG. Honeywell does have an approved LED mod that is still available to fix display issues experienced with the old gas discharge displays.

With Century Flight Systems out of business a lot of the parts for that system are very sparse. You might get lucky finding something at a salvage shop but in my opinion it is on a short time line until there is no support for that system. Not to mention finding the correct installation documentation for the aircraft. At this point with the limited parts we have for the Century 21 and 31 systems I am very reluctant to try and repair them. Also, if you require a EASA release your repair choices are going to be drastically limited.

@LANCECASPER We would not be interested in any deviation from the STC on a flight control system.