Aircraft Electrical Modifications and Wiring Diagrams

[kontiki]

I've been going through the wiring on my 35 yr old Grumman Tiger. It all started when I noticed the breaker labeled ALT Field didn't control power to the alternator field. Once I started looking, I found quite a few interesting/undocumented things. Too many to really list here.

Previous owners of my airplane had quite a few cockpit modifications done. I've been able to get installation documents for the added gear, but installation documents don't really tell you where connections were made on your airplane. These things are sometimes missing on the 337 forms too. I've got a few switches that aren't specifically required by the installation documents that were added without any documentation. I can deal with all the issues, but I'm just wondering.

In GA does anyone get a decent wiring diagram from an avionics shop when they take their airplane in for a mod? I've been told that if the shops have anything that's detailed, they intentionally withhold them in order to get the customer to return to them for repairs. Is that what other pilot owners find?

 

[bnt83]

I've been going through the wiring on my 35 yr old Grumman Tiger. It all started when I noticed the breaker labeled ALT Field didn't control power to the alternator field. Once I started looking, I found quite a few interesting/undocumented things. Too many to really list here.

Previous owners of my airplane had quite a few cockpit modifications done. I've been able to get installation documents for the added gear, but installation documents don't really tell you where connections were made on your airplane. These things are sometimes missing on the 337 forms too. I've got a few switches that aren't specifically required by the installation documents that were added without any documentation. I can deal with all the issues, but I'm just wondering.

In GA does anyone get a decent wiring diagram from an avionics shop when they take their airplane in for a mod? I've been told that if the shops have anything that's detailed, they intentionally withhold them in order to get the customer to return to them for repairs. Is that what other pilot owners find?

I have never really seen good supplemental wiring diagrams. I don't like it either. I will go out of my way to make it clear what happened when working for othera. If installing a whole stack of radios I would provide prints for those and I would expect it if I were the customer.

Also, withholding them is unprofessional. There is no way that would ever happen in the corporate aviation world.

 

[denverpilot]

Never had a shop "withhold" anything about the airplane from us. If we did, I doubt we would ever use that shop ever again. Had one shop that couldn't detail what they tried when they billed a few hours for troubleshooting. They haven't been used ever again either.

 

[weirdjim]

The fundamental problem is that there is no "standard" drafting program for creating/editing/modifying the electrical drawings of the aircraft. I have "this friend Ernie" that has a half-century old 182 whose original electrical diagrams must have been done with quill pin dipped into sheep's blood onto vellum parchment by the looks of them. They have since been redone with a really nice program called Circuitmaker that got sold to a conglomerate that killed CM so now unless YOU have a copy of CM Ernie's diagrams are of no use to you.

Ernie even offered to put a full-featured version of CM online for everybody to use but (a) there is no Mac version and (b) Microlimp's addiction to 64 bit operating systems are beyond CM's capability, being written back in the turn of the millennium when 16/32 bit operating systems were all the rage.

I've seen some add-on programs to Excel/Word/Access/pdf/dxf/ and the like that start off with a hell of a bang and die with a quiet whimper a couple of years later leaving behind a whole string of orphans. Until somebody comes up with method of using one of the major drafting or drawing programs that will stay around for a few years, this problem will be with us for a VERY long time.

Jim (a VERY close friend of Ernie's)

.

 

[GlennAB1]

I should show you all the G-1 cargo door mod wiring schematic I got from a maintenance controller when he retired (It's all he had). Its hand drawn with correction made by xxx'ing out the wire and re-draweng, quite pathetic.

 

[kontiki]

I remember when almost all drafting was done by hand. Years ago, during a layoff, I worked at traditional drafting table with a T square and lead pencils for a few months. I remember actually creating one exploded and isometric 30 degree rotated assembly drawing showing the final assembly of the system from engineer sketches of weldement drawings (cut metal pieces). It was for a CF-6 fan removal and aircraft pallet shipment system.

I've also worked up a few flight preparation sheets using a quad pad and pencil. They were for instrumentation system changes between flights in a flight test environment.

Pros: it's much faster to work with a pencil to create a new reasonably simple DWG.
Cons: it's much harder to revise, maintain version control, search, create a reusable BOM, track wire numbers, rotate, explode, expand to 3D, select views etc. using pencil and paper.

Using CAD for a one time use situation is a waste.

I think all engineering departments in general have to decide what application they use and in what file format(s) to save in. There's all manner of trade off's in those decisions too.

I have no customers for anything. I do like to use a scalable approach for things I do in support of my flying interest. I learn from it and maybe I will one day I will want to go live.

Regardless what is used to create a WDM, I think a good outfit should reasonably be able to provide a hard copy and a pdf file of the WDM to the customer.

 

[nrpetersen]

Absolutely the very best drafting quality I have ever seen in 50 years of engineering was Ladislao Pazmany's drawings of his PL-1 thru PL-7 homebuilts. All were done with drafting pencil on velum or even linen. They are works of art. His spelling was mediocre but the prints were magnificent works of art.