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Building for maintenance and modernization

Carl Froehlich

Well Known Member
I key design element common on the three RVs I built is ease of maintenance and ability to upgrade as opportunity presents, without too much pain. Toward that end I make sure I never violate my rule of ?never be on my back with my head under the panel?. This translates to a panel that is fully removable for work/modification on the bench.

The RV-8 has been the most challenging for this as the towers tend to be a real PITA for wire runs. Even so, a full IFR, dual EFIS screen panel is achievable inside this design requirement.

In simple terms, wiring is divided into two elements:
- Wiring between components that stay on the panel, as example for the RV-8 this is the GTN-650 and the audio panel. Breakers for these components are also on the panel, power connected via a large pin Molex connector.
- Wiring (and all other breakers) are mounted off the removable panel. On the RV-8 the panel wings provide this space. On the RV-10 it is the lower panel skirt. The SkyView displays are all connected via D connectors, so all that wiring stays in the plane when the panel is removed.
- Connecting between the panel elements and the rest of the plane is done via two 25 pin D connectors - of which only half of the pins are used. The rest are available for future options.

This first photo was taking after all the rough wire runs where done:
4612-BAF7-B106-4-D86-9-A2-C-BAB552-D3561-C.jpg

This photo is after all the behind the panel connectors are done:
90-E51191-2878-4069-BF24-B535-DD9-AE044.jpg

This is the back of the panel showing the interconnections and the connections to the rest of the plane.
B4-F5-FFFC-4376-4-A50-996-B-BEB84-E094-EEB.jpg

Here is it all assembled and first panel power up.
05-E40-F9-A-4-A15-41-B6-8-FA9-5-A935-FBEA470.jpg


I advise builders to keep in mind that the perfect panel they build will be modified many times over. My 2002 RV-8A is on its fifth panel. The first panel in the RV-10 lasted only 18 months. If you stick with stock aluminum panels from Van?s a new panel is ~$26, some time cutting holes and paint.

Carl
 
Great plan! I did the same for my -7. I can completely pull the panel in less than 10 minutes. Quick disconnect the pneumatics to the steam gauges and ADAHRS, disconnect the cable bundles, remove the screws and out she comes.

Side view of connector array:
i-bfgnCkp-L.jpg


Back view of connector array:
i-J9M976k-L.jpg


Pulled panel on the bench:
i-TqkZQFJ-L.jpg


Backside (almost complete):
i-fsn3n49-L.jpg


No need for back aches!
 
That looks great for the '5 year back ache'.
Any solutions for the 'annual back aches'? As in maintaining fuel pump filters & brake pedals in a 8?
I sure could use some.
 
That looks great for the '5 year back ache'.
Any solutions for the 'annual back aches'? As in maintaining fuel pump filters & brake pedals in a 8?
I sure could use some.

The fuel filter in an 8 (assuming a standard AFP unit mounted in the standard location) is not all that hard (and easy compared to RVs with tunnels) once you get the pilot seat ramp and floor out. They need to come out anyway to inspect the control linkage.

Brakes - just always bite the bullet and take out the forwarded baggage compartment floor. Simple once you do that as you go in from the top. Get a 45 degree or so degree adapter for you electric driver and you will find it easy to get the floor screws in and out.

Carl
 
Excellent advice

Having just spent (far) more time than anyone should on my back for a (simple) Transponder/Comm/Intercom upgrade I think this approach makes tremendous sense. I still have a steam to 1st gen glass update to do, and would be far happier doing it on the bench.

With proper maintenance and good luck, I hope to be flying my RV6 through several future generations of the electronic bits. If I thought I could stand the initial downtime hit to fully rebuild/rewire the panel in this fashion I would do this now (and probably should).

Those of you building *know* you know exactly what you want (today). Those of us flying know that will certainly change. Plan for many happy upgrades!

Peter
 
A couple of questions.

Reliability - have you found and identifiable issues with the additional connections?

Wire Identification - I see a lot of white wires, a) how do you mark./identify the wires b) does wire marking remain after installed?

I am small and slightly flexible, but crawling under the panel has is increasingly wearing on the old torso. Is the selection and placement of all the parts for easy assembly (and such) a trainable skill with rules that are available?

Thanks for posting this!!
 
A couple of questions.

Reliability - have you found and identifiable issues with the additional connections?

Wire Identification - I see a lot of white wires, a) how do you mark./identify the wires b) does wire marking remain after installed?

I am small and slightly flexible, but crawling under the panel has is increasingly wearing on the old torso. Is the selection and placement of all the parts for easy assembly (and such) a trainable skill with rules that are available?

Thanks for posting this!!

Bill,

If you question is for me then:
- Reliably, no problems on the multi year (and now 5th panel mod) on the 8A. No problems on the seven year (and now 3rd panel mod) on the RV-10. Note - I use a fraction of the connections that Bill Bencze has as all the non-panel related switches are not mounted on the panel - and stay in the plane when the panel comes out so perhaps he can share his experience. Disclaimer - if you use junk connectors and wire it makes little difference how you do it, you will have problems.
- Wire identification, I consider this just one step above useless. I carefully document what connects to what, via which conduit run, which switch, which connector and which pin. This has proven to be the real gold when it comes to maintenance or a panel mod.
- Placement, this is where you should spend some time. There is a logical approach and I suspect you will see it once you work it.

Carl
 
A couple of questions.

Reliability - have you found and identifiable issues with the additional connections?

Wire Identification - I see a lot of white wires, a) how do you mark./identify the wires b) does wire marking remain after installed?

I am small and slightly flexible, but crawling under the panel has is increasingly wearing on the old torso. Is the selection and placement of all the parts for easy assembly (and such) a trainable skill with rules that are available?

Thanks for posting this!!

Hi Bill L,

1) Reliability: With good quality locking connectors, there is no issue with reliability (Like Carl said). These make very solid and reliable connections, esp if you have the proper crimpers and use aerospace grade pins/sockets. However, fewer connections are more reliable than more (and fewer are cheaper!)

And like Carl said .. DON'T use junk connectors! As a lifetime electrical engineer, 95% of the problems I've seen come from connectors and power supplies. You can't practically change the power supplies used in the avionics, but you can choose the connectors. Solid body, gold plated crimp pins are what you want. Garmin sells good stuff; don't know about the others. NEVER use a connector with solder terminations in an aircraft. The natural in-flight vibrations will cause the wire to break at the solder joint in short order.

2) As for marking the wiring: I marked both ends of every wire with a heat shrinked wire ID so I can easily tell what's hooking up to what. I used a Dymo Rhino printer with their heat shrink tube (use theirs, 3rd party compatible products don't work well). It takes a little extra time, but in the end it's worth it (though I did buzz every connection to be sure I got it right). The marking helps to organize the runs and match them up to the right connector quickly. This marking remains forever; very solid. I also have a full schematic of the whole design, so the wire making acts as a good cross reference to the schematic when I terminate each connector.

3) "Is the selection and placement of all the parts for easy assembly (and such) a trainable skill?" Yes; if you know what you want to do: removable panel, removable elx pallet that lives above the rudder/brake assy (this is what I did), I designed the system to make it happen, but using aviation grade assembly and termination techniques. FAA AC 43.13-1B is your best friend here. Also, talk to other builders and learn from their experience/scars.
 
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Great plan! I did the same for my -7. I can completely pull the panel in less than 10 minutes. Quick disconnect the pneumatics to the steam gauges and ADAHRS, disconnect the cable bundles, remove the screws and out she comes.

...

No need for back aches!

Hello Bill. That looks very neat!
How did you carry-through the shield ground of the CAN bus. Did you connect it to the casing of the big connector or did you assign it to a pin?

Also, can you give me the part number of the connectors you used?
Thanks
 
This is an important topic, and not just for the panel. When adding anything anywhere on the aircraft, a builder should ask himself, "Will I be able to get to this later on?" and "Will I be able to get a wrench on this to check the torque?"
 
Great plan! I did the same for my -7. I can completely pull the panel in less than 10 minutes. Quick disconnect the pneumatics to the steam gauges and ADAHRS, disconnect the cable bundles, remove the screws and out she comes.

Is that the standard or extra-tall panel? Or did you roll your own?
 
Great plan! I did the same for my -7. I can completely pull the panel in less than 10 minutes. Quick disconnect the pneumatics to the steam gauges and ADAHRS, disconnect the cable bundles, remove the screws and out she comes.


Back view of connector array:
i-J9M976k-L.jpg


No need for back aches!

This is really elegant. Got any specs and suppliers on those great looking connectors?
 
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Avionics locations and access

Those connectors appear to be the Circular Plastic Connector (CPC) series from TE available through Digikey, Allied, etc. They use the crimp pins that are used in the D Sub connectors.
These connectors are similar to the very much more expensive mil 38999 series of connectors. After a previous lifetime spent in the aerospace design engineering business I can say with some conviction that connector issues are associated with 90% of the reliability and maintainability issues of getting a new system into service so adding a bunch of connectors may be making the troubleshooting easier but increasing the probability that it will be needed.
Since we are building a ? one off? and not designing for production the parts that need to be easily removable should be the parts with the highest failure rate. Removing the whole panel may not be necessary other than for the initial wiring and checkout. Being able to diagnose the root cause of the in service problem is a big part of the design configuration process - especially when the failure is on a trip at a remote location.
Having some capability to ?break in ? to the wiring is a good idea. Either a separate ?test? connector or using terminal strips that easily allow internal wiring to be probed. Using the 16 pin terminal strips from Cinch is one option. Looks a little ( ok- a lot) ancient but it is very reliable. Takes up more space and heavier but much more reliable and has more utility. Did I mention reliable ? Not suited to line production but that is not a consideration. When considering what is good design for the specific application I think it is important to work through all the likely scenarios from initial construction to maintenance for each candidate design solution. I keep coming back to the terminal strip solution as a way to be able to troubleshoot and diagnose faults with just a simple multimeter for test equipment. Still looking for a more elegant solution but that is top of the list for now.

KT
 
SNIP....Removing the whole panel may not be necessary other than for the initial wiring and checkout. SNIP

I keep coming back to the terminal strip solution as a way to be able to troubleshoot and diagnose faults with just a simple multimeter for test equipment. SNIP
KT

On the first point, don?t overlook future panel mods. Once flying many builders figure out that what seemed like a good idea (placement of stuff for example) proved other wise. Simple mods should not require major surgery. The longest one of my panels went from first flight to first mod was 18 months. No replacement of avionics, just layout changes.

On terminal strips - recommend against using them. They take up a massive amount of space, add a boatload of wire and connections and typically do not help much in troubleshooting. D connectors where you have each pin documented however are great for anything other than power and with a simple jumper serve the same function of a terminal strip.

Carl
 
Great plan! I did the same for my -7. I can completely pull the panel in less than 10 minutes. Quick disconnect the pneumatics to the steam gauges and ADAHRS, disconnect the cable bundles, remove the screws and out she comes.

....

No need for back aches!

Is the compass card PAI-700 ?
If so, I was thinking the same for my RV-7, but I was not sure about access to the adjustment screws when panel mounted.
 
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