jkarch

Thank you A! Much appreciated! Yeah it’s been a while, my Century 21 motor drive inductor gave up the ghost and the folks at Autopilots Central in Tulsa fixed it and said “check the motor”. Trouble is I still don’t know the part number of the one installed in my J but I assume it’s the one with a half disk rather than cables.

Hi Dan is the roll servo still available? what type of mooney, 1980s m20j?

That’s what I heard as well from a mechanic, a blocked up frozen oil cooler. Normally the sump and cylinder heaters should be good enough if you wait long enough to preheat. 100w is still good stuff though.

Some people had good results with a gain circuit. I heard there was a radiocoupler or something involved, maybe that was an issue?

Was it in GPSS or DG heading mode? It seems the scale factors are different. For DG heading mode the adjustments could the the potentiometers on the autopilot unit itself. For example the L and R adjustments that bank for standard rate turns at full deflection (90 degrees) of the DG. I think the GPSS gains determine how you steer in to intercept a course. Of course your unit may behave differently than the C21. The C21 has a centering potentiometer, followed by left and right bank adjustments.

The G5 has a GPSS scale factor for gain setting.

So I have an update and should have a better one next week once the fix is made. Seems the installers somehow clipped/disconnected the excitation wire to the attitude indicator, so the attitude indicator control response remained flat. That enabled the aircraft to roll left and right with impunity (I stopped it at a steep turn). The signal wire is connected, as is the excitation return, but the excitation from the tray to the connector may have been disconnected during the G5 install. I'm biding my time until I install a GFC500 and 86 the vacuum system and gyro, but my gut feel is this will fix it. In the meantime, I took the advice of many and contact cleanered the heck out of the connections and made sure everything was ok. It's definitely useful to have some Pomona test pins and a volt meter for this kind of debugging. -J

The one big pain here is you have to remove the interior to mess with the gauges. I’d assume removing the inboard sender also requires a reseal in that location and you probably want to do this with an empty tank too! -J

I had Weep No More redo my tanks and somehow they removed the RTV holding the sight gauge in place. When I flew away after the fuel tank repair I had noticed the fuel gauge had popped up into the slipstream and threatened to fly off the plane. I added some tape to hold it in place till I got home and added RTV. Seems they forgot to RTV in the gauge in time for me to pick the plane up as the RTV was still wet when I went to inspect the reason the gauge almost fell out!

I have a bit of a stumper. I brought my plane up to an avionics shop to do an installation of a dual G5 system connected to my M20J’s Century 21 Autopilot. When I got the plane back I found that the autopilot in DG mode could not hold a heading and would hunt with rather extreme bank angles around a heading point. Namely, it would go into steep turns (+/-45 degrees+) left and right as it crossed the heading bug in HDG mode and I would have to take over the controls by force and disable autopilot to prevent this undesirable operation. NAV mode in GPSS also shows the same behavior. The Attitude indicator had to be retained (probably for this very reason). On the ground, when the engine was running and the attitude indicator was level, engaging the autopilot where the HDG=HDG bug and HDG mode enabled, the roll motor would hold ailerons level. When the engine shuts down, the AI often settles in a left banking position. When this happens, the ailerons respond by rolling to the right, so it’s clear that the autopilot is responding appropriately to the attitude input, and therefore the attitude connection, which was unmodified on connector CD176 seems correctly connected. Before the G5 upgrade the autopilot worked fine with the original 52D54M gyro. I made sure that the jumper connecting pins 13 and 14 (DG select pin) on connector CD-194 was removed since the 52D54M gyro was replaced by a G5 HSI as per Century Flight System’s recommendation. The G5 install manual incorrectly targets different jumper pins on CD-185, which does not exist on a C21 autopilot. This makes me question the reliability of the G5 install manual, but that’s another issue. It appears that on connector CD175, someone took a grey wire out (perhaps it is the HDG signal that is on pin 17 but I don’t know) and wired it to a non-shielded 22 AWG wire. I would probably prefer that it be shielded but I’m sure it’s not the issue as it’s probably heavily filtered. Pin 2, however, is a blue wire that is called course select and it is also supposed to be connected to the GAD29B. Both signals need to be connected and shielded to the GAD29B as per Garmin manuals, though I wonder if there are potential erratas as the information provided is incorrect. CD175 is left hanging and while the grey wire (suspected to be Pin 17, HDG signal) is connected, Pin 2 is left floating. When powered on, the blue wire pin 2 measures 4.825V using a Fluke 87 IV meter wrt airframe ground. Pulling the GTN750 and GAD29B circuit breakers did not change this voltage measurement, making me question if this signal is connected to anything of interest. I’m supposed to bring the plane next weekend in to the avionics shop for a fix, but if anyone has experience working with the C21 and G5s / GAD29B and can chime in on potential issues, it would be helpful because the shop is trying to do the work on it over the weekend while I wait (it’s about 100 miles away from me). I know that the CIII autopilot has radio couplers, etc, but this connection is direct. While there is a GPSS scaling factor, there is no option for HDG bug scaling factor so I wonder if the voltage outputs going to the Century 21 are correct. I also have heard that the C21 is supposed to be limited to +/-29.5 degrees of bank in spite of any inputs on HDG or CRS which is a bit strange too. Any ideas? I did notice this: https://www.beechtalk.com/forums/viewtopic.php?f=21&t=71222 . It does seem the attitude input is suspect because it should be clamped to max deflection, but on the ground it seems to respond, so I'm not 100 percent sure, but perhaps as one poster suggests the signals are intermittent after being relocated from one location to another. Thank you!

electric airplanes are probably closer to turboprops in terms of smoothness and altitude performance except they can regenerate power on approach and be used for landing with that power saved. Trouble is energy densities but new formulations are on their way for batteries.

these are at least 60 percent more expensive, right? An HSI and AI combined is like 10k which is more than these two units combined and installed with a new panel.

I once did Seattle to Rapid City and still had 22 gallons left on my J.

If the cylinder in the back is hot then it could be a baffling issue if the EGTs are uniform

Strange, I had a problem with a misfire in a #1 Cyl harness and #1 ran cooler though with higher EGTs