Monday, January 11, 2016

Yet Another Annual

The plane is down for inspection since December. I am by no means ready to formally document everything yet but there was one issue I should inform readers about before they run into the same problem.
The nice blue air filters I had installed during the last annual (and which appeared just fine in March when I installed the Ducati regulator) both showed cracked bodies just behind the attachment flange. They were both cracked almost to 50% of the circumference and clearly did not provide much filtration at that point. When I removed them, I found that the rubber appeared to have worked its way into the serrations of the hose clamp that was holding it on, on both. One was so deeply connected that it ripped the rubber of when I removed the hose clamp. It almost looked like the rubber or plastic was not able to take the heat under the cowling as it looked partially melted into the hose clamp.
I was about to order replacement filters from the same place and am happy now that they ran out of stock. That gave me a moment to reconsider that they might just not be the best solution as an aftermarket product anyway.
I found a smaller sized K&N but decided to give Green Filter a chance. They have one model that just fits the Bing flange and I like that it is a fully paper/rubber model with no metal parts.

It has a pretty nice clearance and a very good fit to the rubber flange of the Bings. Actually, I had taper the inside of the filter flange a bit to be able to get them to slide on. The type number is 7069 and it appears to be only one that would fit the Bing inlet. Let's hope this one holds up to the vibrations better than the blue filters.

It was also time to replace the spark plugs. I did not do it at the 50 hour mark as they looked prestine. I just cleaned them and put them back in. They still did not look like they needed replacement but I did notice a deeper drop during the 4000 RPM ignition test in the last months, so I went ahead and threw them out.


Of course I had to try something new for the replacement, so I installed the Iridium version of the same DCPR8E plugs which have an EIX suffix. They are a bit pricey but then again they go into an airplane so we are used to overpaying, right?
The result by the way was amazing. The ignition test dropped the RPM only by 50 instead of 70-90 with the 8E plugs. We will see how they hold up and if this deteriorates over time but for now I think they might be worth it.

I might have to improve the air scoop for the voltage regulator as the temp indicator hit the lower mark so far and I don't believe she flew a lot during Arizona's hot summers....

One of my concerns last year was the plastic buffer in the tail cone that should keep the lower cable for the elevator from sawing through a bulk head. It was worn down very close to the metal and I had greased it with silicone grease to reduce friction.

I pushed the cable out of the way to get a better shot of the actual friction area and it looks like it did not deepen any further since last year. If it was touching the metal the primer would have rubbed off and there is no evidence that this is happening yet. I just re-greased it and will check again next year. The tension of the cables held up pretty well too and I did not tighten them.

One of the improvements this year was to finally add the APRS radio beacon. I am a licensed Amateur Radio operator, so it was just natural to put that license to additional use with the RV-12. I took quite some time to choose the right antenna for this project. I had an antenna from DeltaPop Aviation but was afraid that it was too heavy and catching too much wind load for the super thin skin on the bottom of the tail cone. I looked into mobile Amateur Radio antennas and considered different antenna bases and so on. After long deliberation with myself I decided to go back to the initial thought of using the whip antenna from DeltaPop Aviation. It is exactly tuned to the APRS frequency, has a matching network that eliminates static build-up and it is proven to survive the 120 knots TAS of an RV-12. The mobile antennas won't get used much above 80 mph and their radiator could separate from the base and fall off the plane if the set screw ever gets loose. All I needed to do was to properly reinforce the skin on the bottom of the tail cone to avoid vibration cracks over time.


The little fin is the PCAS antenna that I had installed last year. I finally hooked this one up to the Zaon MRX unit this year too. The base of the APRS antenna is 4 feet away from the base of the VHF Com antenna and I only had to slightly increase the automatic squelch of the SL-40 to not open up when the beacon sends a position (from 56 to 75).


So you can see that I took the reinforcement very serious. The large sheet is 40/1000" thick and a foot long, I put the transponder reinforcement plate on top that came with the RV-12 antenna and which we never used and I also installed some left over angle on the perimeter of the base sheet to stiffen it up while keeping it very light weight.

On the interior I did not get very fancy for now but it might turn out to be a good spot anyway. The Byonics radio was attached with cable ties to the tank fill spout (some foam in between to dampen vibrations). And the GPS antenna for the radio was riveted to the center bracket of the rear window to give it a good view of the satellites.

The only required switch on the dashboard is a breaker of 3 Amps that is labelled "Beacon" which I felt was quite accurate.

It worked right away when I switched Main and Avionics on. If you would like some advice on where to wire this into the existing 12V bus without causing a fire, just email me.
As you can see the Zaon MRX was finally installed too and it is connected through the 1 Amp breaker to the Avionics bus. So far I have not seen a case where it would have detected traffic when ADS-B did not see it but I haven't been flying in rough mountainous terrain yet, so the jury is out if this PCAS install was a waste of time.
The APRS beacon works great and you can now follow the travels of N128TL by following this link.

Besides adding stuff I was also able to determine the cause of my problems with the EGT sensors. The sensors work just fine but the wire of the right sensor (on the sensor side) had vibrated off. The stiff wire of the sensor harness is not just hard to reliably crimp a connector too but is not itself not very happy about vibrations. I did a brute force approach with a tube of red solicone to address that after soldering (yes, yes, I know, we will see if it breaks again) an extension to the broken harness wire.

I just smothered the EGT temp wires in a layer of red silicone in the hopes of softly reducing the vibrations enough to avoid future breaks.

This should have been the last item on my list but then Dynon announced the release of the GPS-2020 that would be the last piece in my Avionics system to be fully 2020 compliant. I couldn't pass that chance up to replace my current GPS while the plane was all opened up now, could I?
Dynon was very quick in delivering the GPS and I figured from the RV electrical schematics that this was a drop-in replacement. As I did want to reroute the 4 wires through the firewall, I just cut off the wires of the old GPS and soldered the new wire harness to the existing wires.

Getting the old GPS out was a hassle. The metal lock screws are almost impossible to hold well enough to turn the bolts. I ended up dremeling the case of the GPS back to I could get a wrench on them. The GPS still works but sure doesn't look so good now. Oh well.
Please note that you do need to upgrade your SkyView software to V14.0 or beyond to be able to use the GPS-2020. And you will have to go into the setup and manually make all the changes to make it understand that the previous GPS has been replaced.

I also checked that worrisome Service Bulletin item about the flaperon torque base in the tunnel. Sorry I can't remember the exact phrasing or the number right now. It's the one where an aluminum bracket starts developing a crack from a rivet hole after around 200 hours of operation. I took photos and they show no issues yet at 113 hours.

And the final installation was a piece of plastic that I designed and printed out on a side project I completed in December last year. It's a Kossel 3D printer and it allows me create neat stuff that would be hard to find otherwise. In this case it is a headset hook that allows me to finally have a good place for my Bose headset while I am away from the RV.

This is a prototype and I am trying 3M double sided tape on the back (the red type) but I a mnot sure if it will stay there when the plane heats up in the summer on the tarmac. So I will design another one that takes rivets for installation - just in case. Anyway, for now I am very happy that the headset is nicely stored under the avionics bay and out of the sun.

No comments:

Post a Comment