PT20J

Comparing autos (and airplanes) to bicycles and motorcycles may be confusing because each vehicle has it's own terminology for the same geometric parameters. Here's a picture from Wikipedia showing that a bicycle has, what in automobiles is called, positive caster. We're talking about caster (steering axis angle), bicycle manufacturers talk about trail. But the idea is the same: the tire contact point is behind the extended steering axis.

It's harder to visualize when the pivot point is at an angle. It's more obvious when the pivot point is vertical as on a shopping cart wheel. The force moving the wheel forward acts at the pivot point and the friction force on the wheel acts in the opposite direction at the ground contact point. When the wheel is moving straight ahead, the two forces are in alignment, but when the wheel is turned, the two forces are not aligned and thus create a restoring torque that turns the wheel back into alignment.

You're right, I missed that button somehow. The point of entering the waypoint is that it allows the GPS to do its normal TO-TO leg sequencing and frees you from any further knob twisting or button pushing.

I'll have to look again, but I recall on my J the pin is captive somehow -- maybe a crimp in the last hinge loop. I was going to see if I could pull the pin to remove the door to replace the door seal and decided it was going to be impossible.

There are locations out in the mountainous west where, due to terrain or gaps in radar coverage, you are on your own nav for quite a while after departure.

There are still some obstacle departure procedures around that require flying a VOR radial and then intersect a radial from a second VOR. Sure, I have dual VORs and the G3X has dual bearing pointers and there is always OBS mode on the GPS - there are several setups to fly these procedures that are not in the GTN database. But, it is so much easier to let the GPS navigator do the work. Although my GTN Xi won't let me enter a user waypoint at the intersection of two radials, ForeFlight will easily do this. Just enter VOR1radial1/VOR2radial2. When I upload the ForeFlight flight plan to the GTN via the G3X (Flightstream would be another way to upload), the GTN creates a user waypoint at the lat-lon for the intersection. If you don't have a way to upload flight plans from ForeFlight, just select the waypoint on ForeFlight and note the lat-lon and enter that in the screen for creating a user waypoint in the GTN. ForeFlight uses decimal degrees for lat-lon and Garmin defaults to deg-minutes, but there is a convert button on the user waypoint data entry page to change modes so that you don't have to do the math.

I would expect high resistance failures of either Tempest or current production Champion plugs to be rare. The problem was with older Champion plugs that had the removable resistor. Champion now has a design similar to Tempest. If your mechanic is having this many failures, I would suspect his test rig or method.

I’ve found that after the plugs have been in use that it is more difficult to get a good connection to the firing end with a multimeter probe. I have the best luck pressing the probe tip tightly in the gap between the center and a ground electrode.

I failed it as part of my ongoing FMEA. I had my avionics installer agree that it was a minor deviation to put the GMU on a separate CB rather than combining it with the GSU 25D because I saw no need to deprive the G5 of the magnetometer in the event the GSU 25D or it’s circuit popped the breaker. Garmin told me there was no technical issue; they were just trying to cut down on the number of breakers by combining circuits to make the installation easier. I actually noticed this a couple of years ago but it took a few contacts with different people over time to finally get to someone who agreed it was a real issue.

There was also a problem with some Champion massives after the change to the molded-in resistor to eliminate the high resistance issues with the old removable resistor design. A change was made to eliminate the cement between the center electrode and the insulator and some plugs had enough of a gap there that combustion gasses could get in and the pressure would crack the center electrode. I don't know if that got fixed or not, but after I discovered two broken center insulators, I replaced the Champions (which came with the rebuilt engine from Lycoming) with Tempest plugs.

There is a software bug in the G3X (v9.15 and earlier). According to the AFMS, if the GMU 11 fails the G3X is supposed to display a red X over amber HDG and display magenta GPS TRK on the HSI. But, instead, it continues to display white HDG as normal. What is happening is that the logic is not switching to TRK upon GMU failure and the ADSU 25D is continuing to compute HDG but without GMU input so the heading will drift over time. The G5 does properly switch to TRK. I don't have a GI 275, so I don't know how it behaves. I reported it to Garmin and after some back and forth, Support was able to reproduce it and passed it on to Engineering for resolution.

The Lycoming EIS is fixed timing only. Did you set your Surefly for variable timing? That would account for the DIP switch differences. You can check with the experimental sites about how they set their plug gaps. The last time I talked to Surefly about it, they had some legal concerns about recommending wider gaps on certified airplanes. A wider gap would allow the voltage to build higher and result in a stronger spark which might improve combustion efficiency slightly. But, probably not by much. If it runs well, I wouldn’t mess with it. If you do decide to widen the gaps, be very careful not to put any side load on the center electrode. It is very easy to stress the center insulator, and if it breaks later you can get a preignition event that will destroy a cylinder if you don’t catch it and reduce power quickly enough.

https://www.3m.com/3M/en_US/p/d/b40069421/

Good catch. I suspect that a loose or broken piano hinge pin is what allows the door to detach if opens in flight.

G3X data logging must be enabled in configuration mode, and an SD card must be inserted in the G3X. The G3X will create a .csv file on the SD card every time it is powered up. You can copy the .csv files from the SD card to your computer and upload them to Savvy. I keep two SD cards for the G3X. I download nav data updates from flygarmin to a card and take it to the airplane and swap cards and then update the G3X. I copy the data files from the removed card to my computer and then reuse that card for the next nav data update.

Ah, apparently there is a difference between EFC-100 and EFC100. My mistake - I just searched for the string referenced in the post. Thanks for the clarification.

I never heard of this for fuel tanks. But I took the poster's advice and looked into it. EPC stands for Epoxy Flooring Compound. According to the manufacturer, Sealbond, it's "Ideal for floor protections of new and existing flooring of food processing plants, chemicals and pharmaceutical factories, sugar and oil refineries. Recommended for installation of anti-skid coatings indoor. For patching of deteriorated flooring. High performance coating system." Not sure about airplane fuel tanks, but it sounds like a good product to use on my hangar floor. Sealbond-EFC-100-Epoxy-Flooring-Compound.pdf

You probably know this, but just in case… Don’t forget to transfer the programming modules, and save the light bulbs from the old unit for spares. The computer and attitude indicator should really be aligned when swapping parts, but try it out - it may work OK.

Aircraft Maintenance Engineer.

The engine mount on my M20J is attached with 4 AN4 bolts which each have a shear strength of 3730 lbs. The engine and prop weigh around 400 lbs and with a 1.5 factor of safety and a max load factor of 3.8 g that’s the equivalent of 2280 lbs. When we weighed my airplane, the weight on the nose wheel was only 639 lbs. Seems like the engine mount is plenty strong. However, I do what 90% of mechanics do and use a tail weight.

You can put a heavy strap around the engine mount and lift from there -- no one has said not to do that.

That's because you have a lot of experience and know what you are doing. I don't have your experience, so I have to look this stuff up

Interesting. My Blackstone analysis always comes back with 0.0 water and <0.5 fuel (except for once it was 1.0 fuel). I'm not running an dehumidifier and I use Camguard but have not used MMO. Mostly LOP down low and peak up higher. Now I'm curious what others are seeing.

It may depend on serial number. Early Js had a flat left cowl flap and it may work on those. Later Js had a contoured left cowl flap to match right one and it doesn't work on those; the POH states that opening the cowl flaps 1/4 costs 2 KTAS and opening 1/2 costs 4 KTAS.

They give some paint specs in here. WBtech.PDF