What is this wire? (Piper Arrow)

[mandm]

Went flying this evening, did a longer flight, some touch and goes and power off 180s. Everything worked on the plane. After flight I wanted to check some panel lighting and instruments and on the pilot side by the rudder pedals, there is this large white wire just hanging out that appears to have come loose from the crimp above (my guess). The wire goes directly through the firewall forward. Wondering if this got loose somehow (and why) and what it might be if anyone knows. I’m guessing it’s electrical due to the size of the wire. I’m going to message my mechanic to come out in the morning too.

 

[Jim K]

The only wires that big on my plane are the main battery and starter cables. It certainly appears to be a ground. Your battery is in the back right? I can't figure what they would run through the firewall to terminate like that, or how it being disconnected didn't cause any issues.

 

[Jdm]

It’s definitely the ground wire. Good catch! Easy fix.

 

[Timbeck2]

I’m going to message my mechanic to come out in the morning too.

Tell him to bring a new terminal and the BIG crimpers.

And if you take the pilot's seat out for him, he may even do it for free.

 

[Ryan Klems]

As previously noted that's a ground, it'll run from there to the engine.

 

[Timbeck2]

^^^^^
My terminal and big crimper guy

Mornin' buddy

 

[mandm]

As previously noted that's a ground, it'll run from there to the engine.

Thank you everyone for the replies. I’m guessing this came loose in flight during touch and goes. All electrical items were working in flight, when I stopped I fuelled up and started again without any issues, so I’m confused what this ground wire does.

 

[Capt. Geoffrey Thorpe]

Thank you everyone for the replies. I’m guessing this came loose in flight during touch and goes. All electrical items were working in flight, when I stopped I fuelled up and started again without any issues, so I’m confused what this ground wire does.

Lets current flow through the wire instead of through things like throttle cables

 

[Ryan Klems]

That ground wire is what provides the main ground to the engine block and everything attached to it, providing a good return path for the current to the starter, etc. Your engine is mounted to the engine mount with rubber isolators so absent that wire, it's going to have to find a ground path through whatever other means it can, such as your throttle cable, mixture cable, carb heat cable, p-lead shields, etc. Those items of course aren't designed to be current carrying items, but the electrons don't care, they just want a path home. Typically you would experience various symptoms from the alternate and most likely higher resistance return path, such as slower cranking. Now, it's always possible someone installed an additional ground for the engine at some point, but generally that is the one and only main ground return from the engine on a PA-28.

 

[ksandrew]

A nice simple repair, no guessing, no diagnosis, Just clean it up and crimp it.

 

[Jdm]

It probably came loose when he pulled the side panel. Again, good catch.

 

[Rgbeard]

Thank you everyone for the replies. I’m guessing this came loose in flight during touch and goes. All electrical items were working in flight, when I stopped I fuelled up and started again without any issues, so I’m confused what this ground wire does.

It provides a solid flow of electrons. In its absence generally electrons will flow from other sources. As stated by @Capt. Geoffrey Thorpe

Glad you found it, and got it fixed. You should strive to increase your knowledge on simple electrical theory as well as other basic technologies that keep us in the air.

 

[Chip Sylverne]

Bad grounds are a major reason why stuff goes wonky. Often overlooked are the main ground straps, as evidence by your experience. Clean 'em up and make sure they're secure every now and then!

 

[Silvaire]

I had an engine to chassis ground wire come loose on my Land Rover. I first noticed that my starter was cranking slowly and then I noticed that my parking brake was frozen. The starter had found a new path to ground through the parking brake cable which got so hot it fused the cable to the housing.