Looking for Piper drawing #15500 Electrical

[Stew]

Very many thanks for the above responses.

In the UK many eligible light aircraft types fly under a permit from the UK LAA and that includes all the homebuilds. If it is deemed sensible and safe then you can incorporate changes/modifications following their procedures.

The PA18 is not eligible to go on the UK LAA Permit Scheme so it flies with a full UK CAA airworthiness certificate (as an result, it can be used for training and "hire and reward") . However, changes and modifications are much more time consuming and expensive. I have attached the three modified schematics that I have, I have simply removed the erroneous tags leaving just the swg wire sizes.

As you say, it is not rocket science and a decent scheme could be developed but we would have to go through an approval process or we have to stick to the original with some "minor" mods to incorporate the radio,transponder, electric AH/Turn & Slip, LED landing and nav lights. Sticking to the original apparently requires an original wiring diagram to illustrate how it has been rewired.

Could you just confirm that this is the best schematics/diagrams anyone is aware of.

Kind regards

Stew

 

[willhash]

Really have me scratching my head on that one. But I'm sure that I have never wired a Cub as per the factory diagrams. To many improvements and to many changes since they were first drawn up. Not sure what your 'legal' situation is on that side of the pond but I've always just sat down and drawn up the diagram as needed.

Some things I always include are master and start relays with spike diodes. Wires sized as per tables in AC43.13. All switches and breakers moved to instrument panel. Separate main bus and avionics bus. DPST switch for master switch. It's actually a pretty simple layout for the airframe wiring.

Web

Hey Web what are your thoughts on using a DPDT switch for the master and connecting only the battery to the second "on" position.

Will

 

[wireweinie]

Hey Web what are your thoughts on using a DPDT switch for the master and connecting only the battery to the second "on" position.

Will

That works as long as you don't have a charging system. If you do have a charging system that second pole is used to switch regulator power on/off. That way, if you have a meltdown, one switch motion and the battery is off line and the regulator is powered down.

Web

 

[Eddie747]

Hey Web what are your thoughts on using a DPDT switch for the master and connecting only the battery to the second "on" position.

Will

Not sure if this is what you mean, mine is a DPDT with one pole battery power to buss, second pole is alternator field. It's a 3 position switch On-Off-On, the pole with the alternator field circuit only the left On position is wired to the alternator, cut the jumper wire that went to the Right On position, the Right On position is battery only no alternator field power, Alt-Off-Batt

 

[willhash]

Yep that's what I was getting at Eddie. Probably could have explained better. Thx.

Will

 

[Eddie747]

Yep that's what I was getting at Eddie. Probably could have explained better. Thx.

Will

I did it that way a while back, I wouldn't do it that way again though, I would leave it wired so alt field is on in both ON positions, and wire the field power source from the buss through a 5 amp c/b directly to the field pole of that DPDT master switch. That way the alternator is available in both ON positions and if you ever need to break the field signal you can pull the 5 amp c/b on the buss. I just didn't think about that when I wired it. Wired now 5amp field protection is a fuse inline between alt and master, wouldn't have needed that if wired through a 5amp breaker on buss.

 

[Steve Pierce]

My 1972 SC has the two fuses in the back and only one relay (starter). I wired a circuit breaker switch on the field when I installed the B&C altinator a few years ago so I can kill the alternator but run off the battery if needed. I don't turn the field on till after the engine is running. Something I got from my Dad who use rebuilt alernators. I plan on installing two circuit breakers in place of the two fuses at the battery next.

 

[wireweinie]

Battery still in the stock position? If so, the two breakers make sense. If under the seat, just one breaker. If it pops, reach down and reset it. I've seen a couple of installs with two breakers under the seat. Just doesn't make sense to me.

But having a field breaker (switch or push-pull) is mandatory safety item to me. As stated above, it allows the pilot to power down the charging system while still keeping the battery on line.

Web

 

[Steve Pierce]

Yes, stock battery position and agree on the undersea battery and I too believe the field switch is a must. Swelled up a better I was sitting on and had an electrical fire with my son in the back with a runaway generator.