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Jake@BevanAviation

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  1. @Amelia A S-Tec 30 system with the ST-901 GPSS convertor if equipped would rarely use a NAV mode unless you wanted to track a VOR/ILS. You would put your fight plan in on your primary navigator, turn GPSS on for the ST-901 and engage the autopilot in heading mode. The system would follow the flight plan as if it was tracking a heading bug. Can you provide additional details about the issue you have with NAV mode? As for the alt hold function, the system relies on the output of the pressure transducer to provide a correction error for alt hold functions. The old blue plastic transducer are known to have issues that develop over time. If it was me I would start by checking the pitch servo start-up voltage and control rigging. Next you would check the static system input to the pressure transducer and the output of the transducer for correction error. We have seen multiple issues with the blue transducers and static lines that create issues with alt hold tracking. If you wanted to troubleshoot a Nav track issue you would start by checking the lateral deviation error from the navigator to the S-Tec 30 control head. As long as you are getting the correct deviation voltage to the control head the navigators are working as intended and the wiring would be ok. The new step would be to get the control head and roll servo checked. Just like the pitch servo, check the roll servo start-up voltage and control rigging. Unfortunately, S-Tec requires that faulty units be sent in to the factory for repair via a SRO from a current dealer. There are only very minor field repairs that can be done to the units. Also, the blue transducer is not repairable if found to be faulty. You would need a new gold transducer assembly. If you have questions or concerns about the system just give me a call. NOTE: the G3x 7" and 10" pfd are approved for the Mooney M20 up to the S model. Just make sure you have plenty of space as the units are pretty big.
  2. Could be a roll servo or flight computer issue (final amp stage). If it was me I would disconnect the roll servo and put a DC voltage meter across pins D and L. With heading mode and the A/P engaged, heading bug under the lubber line with a level attitude you should have close to 0VDC. Going one way you will have positive DC voltage, and the other way negative DC voltage. The voltage should be equal at 45 deg left and right of the lubber line. This will check the flight computer to see if there is a issue in the final amp stage. If the computer checks good I would send the roll servo out for evaluation. We can evaluate the servo if sent in. Current lead time is 10-14 business days. If you want to send both the roll servo and flight computer I can run them together on the bench.
  3. You can back pin the connector if you take the back shell off or use a test box which we have.
  4. 28VDC input power, 25-27VDC regulation on pin A. If you monitor pin A with the servo connector plugged into the ship you should have 25-27VDC. Anything outside that spec would cause a PFT failure and if the voltage was too low MET would not be functional.
  5. What is the long part number of the trim servo and I can tell you what the regulated voltage should be.
  6. During the A/P test, the 4 flashes of trim is two up pulses and two down pulses to the trim servo. The computer sends this drive and looks for feedback to see if the motor ran or not. You never see the motor turn the capstan cause the solenoid does not engage during this test. However, if you listen for the trim servo to run in the tail you should hear it run 4 times then stop. If MET (manual electric trim) is not working I would check the regulated trim voltage (pin A of trim servo connector). This has to be within a certain tolerance as the autopilot (KC19X) monitors this voltage. If this regulated trim voltage is not within a certain tolerance or missing the unit will fail PFT.
  7. I would start by double checking the compass system to the wet compass on a compass rose. That should give you an idea as to which system is off. If the issue is the KCS-55A compass system, possible components that could be a problem would be the KG-102, KMT-112, KI-525, slaving accessory. There are adjustment pots on the slaving accessory to help align the system. The adjustments for the slaving accessory are for N/S and E/W. If the system was consistently off around the compass card I would say adjust the KMT-112. If only 2 points (N/S or E/W) were off try adjust the slaving accessory. If you need help troubleshooting the system give Ronnie Tucker a call (Onsite Avionics) 713-254-9367. He is based out of Willis TX and has a mobile service. If the KG-102 needs to be evaluated contact Jerry at Porter-Strait in Tulsa OK. Unfortunately, we do not have the capabilities to repair the KCS-55A compass system.
  8. Anytime the system is over banking there is a issue with the AI information or the alignment of the system. For example, if you rotate the heading bug 45deg right of the lubber line the aircraft should go into a 20-22 deg right bank and hold the bank until the HDG bug is approaching the lubber line. Without the AI information the system will continue to turn to the right until you tell it to stop. This is situation can lead to a dangerous attitude if you are not watching the bank attitude of the aircraft. All the interconnect drawings for the system and the alignment procedure are listed in the Garmin IM. If the shop is knowledgeable about how the GI275 is interconnected to the legacy system they will know how to test the attitude response on the ground. The GI275 ADAHRS +AP unit is perfectly capable of driving the legacy autopilot system. The key is knowing what information the system wants and how to get it to the system.
  9. I would double check the wiring to the KFC225, specifically the gps select and ILS/GPS approach.
  10. Unfortunately, I have never worked on the Trident system and I don't have any service manuals or test sets for that system.
  11. @Greg_D I can work on the servo but some of the parts are very limited and Honeywell is making it difficult to order replacement parts. If you need someone to remove the servo you might reach out to On-Site Avionics or General Avionics. If you are going to call General Avionics do it early in the morning and ask for James. For On-Site Avionics the contact is Ronnie.
  12. KS-178 roll servos are unlike the KS-271 servos were you just remove the servo from the mount. The whole servo assembly must be removed from the aircraft on the KS-1xx series of servos. The removal isn't overly difficulty just time consuming.
  13. @brianucsf With the Aspen PFD and the EA100 if the PFD gets a red X on the display, the EA100 will cause the flight computer to disengage. The EA100 is interconnected with the flight computer in a manner that it will not allow you to engage the system with a invalid attitude signal. Typically, you will get a amber fail annunciation from the annunciator tied to the EA100 somewhere in the panel. Normally they are within pilots view of the PFD. Refer to the Aspen IM for details. The Aspen ACU provides the flight computer with input errors like heading, course, left/right deviation, up/down deviation, GPSS, ect. If something fails in the ACU the flight computer will follow the failure. For example, if the heading output from the ACU was to fail and get stuck at a constant voltage the computer will not respond to heading bug changes correctly. ACU failures can happen just not frequent. All King servos can have motor, tach generator or drive transistors issues at some point. Typically when the drive transistors fail you will only get drive in one direction, or constant drive one direction. One thing I always ask is how are the FD bars responding to input changes. If the FD bars respond correctly to input error changes that checks about 95% of the drive circuitry inside the flight computer. There is one op amp stage left in the flight computer the generates the servo command voltage. This op amp can fail but a simple voltage check at the servo connector will tell us if the computer is the problem or the servo. The control head a/p engage lever is know to have issues and is a pretty common failure. Inside the unit the lever switch holds a small piece of metal. When you engage the system there is a coil inside that will become a electromagnet when voltage is passed. If the plastic tabs break on the lever that holds the metal piece there is nothing for the electromagnet to grab and the switch will not latch. The coil can fail but it is much more common for the plastic tabs to break. There are several other things that can cause issues and after reading your post it sounds like you have a couple of issues. If you would like to give me a call Monday I can tell you what I would look for.
  14. Possible compass valid issue? If you lost the compass valid input it will disconnect the system when you have a lateral control mode selected. However, if the valid was still missing it should not allow you to select a lateral control mode and engage the system. Vertical modes will work without compass valid. What compass system do you have in your aircraft? It is odd that you were able to re-engage the system in FD and ALT hold and not have any issues for a extended period of time.
  15. @IvanP There are multiple things that could cause the system to disconnect in flight. The key is being able to identify which one. Listed below are some examples of failures that will cause a disconnect. Faulty/intermittent disconnect switch Faulty/weak return springs for MET (manual electric trim) specifically the left side of the split rocker. Faulty current sense resistor (thermal related). Capacitor leakage in power-supply circuit (thermal related), most common in units manufactured between 1991-1998. Faulty rate monitor circuit. Faulty MET voltage regulator. Faulty voltage monitor circuit. If it was me I would check the disconnect switch, MET switch, and see if you can identify when the unit was manufactured. Normally there is a red or black 4 digit stamp on the unit around the transducer port. For example 3688 would be the 36 week in 1988. You can look on eBay to get a idea of what the stamp looks like and location. If you are within 1991-1998 there is a good chance you have some leaking capacitors.
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