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Bonding Strap

Eddie Foy

MEMBER
South Florida
I assume #8-Bonding Strap is to ground the engine to the mount??

Is the #5-pin necessary?

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yes... it's useless junk

instead use a short #8 wire from a bolt in firewall to a bolt on back of engine itself.....

Ignore those that are going to say that's to small of a wire...
 
Thanks Mike. Then I can do away with them? I can't see how they would work on a heavily powdercoated mount. What about the pins?

Doesn't the starter ground also ground the engine?
 
Originally the starter was grounded! I planned to do it the same way. What is the purpose of the pins?
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What do the pins do? Are they required? I ask because only two of the mounts had them.

they keep your engine from falling off... yes important

use weld rod or whatever for missing ones

the lock tabs lock into lower bushing, without pin that "could" rotate.......
 
…..Then I can do away with them? I can't see how they would work on a heavily powdercoated mount. ...

IPC shows them, I would install them.
Then add supplemental grounding cable if required.
Scrape powder coating off at isolator mount and at firewall contact points for continuity.
That's how Cessna designed it.
That said... I replaced the engine mount on my 53 a couple years ago,
when I was bolting on the ground straps from the oil pan to the engine mount,
I realized I'd forgot to scrape the paint off the firewall contact points.
So added an engine-to-firewall cable just for insurance.
So
 
I was having sluggish cranking issues with my newly acquired 185 a couple of years back. It had a newer engine with a Seaplanes West mount.
I couldn't see any obvious grounding between the engine and the mount so called Seaplanes West and yep there is no grounding between the mount and engine.
Added a strap at the starter motor mount and big difference in cranking.
 
rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/2B49290E9B9D8414862569A40052B07C?OpenDocument&Highlight=79-25-07

Apparently only applicable to alternator-equipped C180's --
and maybe just the 60 amp alternator, not the original 52 amp model.
Another good reason to just stay with the generator!
 
Regardless whether the starter was mentioned or not, the AD was applicable to Tom3holer's airplane. And the reason for it would be applicable to starters as well as alternators. He did not have one installed. Applies to:CESSNA Models 180, 182/F182, 185, A185, 188, A188, P206, U206, TU206, 207, T207, 210, T210, P210N Series Airplanes
 
Just read this and no it does not have that connection from the ground post of the Alt and the engine.
It is at MHT for the annual and I will mention it to the guys. Will be up there most of next week as were installing a Trio A/p also.
 
I was having sluggish cranking issues with my newly acquired 185 a couple of years back. It had a newer engine with a Seaplanes West mount.
I couldn't see any obvious grounding between the engine and the mount so called Seaplanes West and yep there is no grounding between the mount and engine.
Added a strap at the starter motor mount and big difference in cranking.
When you think of what the ground path(s) must've been prior to adding the cable/strap, it's kinda concerning. How many amps can a vernier cable carry....? :Gnotsure:
 
I don't understand why there would be an argument against installing a ground strap from the engine to the airframe. Many of us have seen the smoke and/or repaired the mess left over when that strap was not installed. Saying that it should not be installed because it's not listed in a AD or service bulletin or that the aluminum bridges should be relied on just because 'it's in the parts book' is foolish and actually dangerous.
If you believe in the stock aluminum bridges, go ahead and install them. Then track there condition as the aircraft is operated. I've seen the crack in as little as 20-25 hours. I have seen ground straps break from time to time but it's usually from human error, such as to tight or poor workmanship.
You have a CAR 3 aircraft. You have an improvement which is a minor mod by anyone's interpretation. Install the ground strap already! And if the aluminum bridges are already there, just ignore them. Chances are, they're already broken and if not soon will be. Even when broken they won't cause further damage.

Web
 
Since we are talking Bonding Strap it should be mentioned that this applies to ALL types of airplanes whether there is a bulletin of some sort or not. I used to own a Lake LA-4. The grounding strap was attached to the aluminum oil cooler bracket which was riveted to the steel engine mount by about half a dozen AN470-3 (1/8") rivets. The aluminum oil cooler bracket was insulated from the steel engine mount with some zinc chromatic tape. Thus the ground path was only through the rivets. I was having the same issues with starting that Tom described in post #13 until I relocated the ground strap to the steel engine mount.

Everyone should check his plane no matter what type it is, to ensure that there is a good ground strap between the engine crankcase and the main ground source of the airframe. If your belt driven alternator/generator has a rubber mounting bushing, it too should have a means to ground it to the airframe.
 
The ideal ground path for any item mounted on the engine should be from the crank case to the air frame. Then from the air frame to the ground terminal on the battery. This path should be as direct as possible and avoid riveted or bolted connections. In a Cub it should go from the crank case to the steel tubing. As the tubing is welded together it provides a direct, low resistance path to the point where the battery ground lead is attached. In a Cessna, good luck, lol. Avoiding riveted joints in the ground path is almost impossible. In that case, keep it as direct as possible. The ground path crossing a couple of joints is better than crossing five or six. Honestly, the best ground path for the starter & alternator in a Cessna is to mount the battery on the firewall and connecting the battery ground strap directly to the engine. This also allows you to use a much smaller ground strap from the crank case to the air frame as that strap only needs to support lights, radios, etc.

Web
 
now with the small batteries mounted up front(inside firewall), I run my main ground to the engine case, with a smaller wire(same size as buss) going to the airframe & avionics ground plane(mounting shelf for all the boxes) from same connector on ground at battery... lights are all shielded wire with their own grounds....
 
If there is any worry about the rules by your particular Fed, just install the expensive aluminum straps. Then install a nice clean bonding (or grounding,- whatever) connection as described multiple times here. Then you can be sure to both avoid arguments with the authorities and still enjoy a good positive connection to your battery.
 
I’m experimental, so I don’t know if this would fly on a certificated plane, but I added a braided grounding cable from the engine case to the firewall. I ran a bolt through the firewall and added another grounding cable to my battery ground.
 
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