flyrotary@lancaironline.net Mailing List Archive

Bill,

You are correct that my battery is in the cockpit. Since you have multiple devices that are having problems simultaneously, it might be good to check things that are common to all of them. The likelihood of loosing several ground or supply connections at the same time seems remote. In other words, check the connection of the forest of tabs to the battery ground before worrying about the individual tabs.. Also, since you have two batteries, it seems unlikely that the problem would be happening within both of them at the same time. Are the batteries connected to the positive side of the system through separate contactors? If so, are both contactors closed when the problem occurs? If both batteries are connected through one contactor, that could be a common point of failure.

Steve

From: Rotary motors in aircraft [flyrotary@lancaironline.net] on behalf of Bill Bradburry [bbradburry@bellsouth.net]
Sent: Saturday, December 08, 2012 6:06 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Engine Ground changed from Aeroquip hose

Steve,

My two batteries are mounted on the engine side of the firewall. I presume yours is mounted in the cockpit? I had not considered a loose connection inside the battery. I plan to clean up all the connections outside the battery.

I have had a VOM connected to the supply side of the transponder when it went off and I did not see any fluctuation in the voltage when that happened. Several folks have suggested that I have a grounding issue so I am cleaning all of them up. I previously replaced both the power and ground wires to the transponder but that had no affect.

I am not certain how to check each ground wire going to the forest of tabs. Anybody have a suggestion?

Bill B

From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Steven W. Boese
Sent: Saturday, December 08, 2012 4:52 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Aeroquip hose

Bill,

From your description, your ground architecture sounds very similar to mine. I have the forest of tabs bolted to the firewall with a brass bolt. On the cabin side, the battery ground is connected to this bolt. Everything else grounds to the forest of tabs. On the engine side of the firewall, the engine ground is connected from the front (in the car) cover to that brass bolt. My arrangement has not had any electrical problems that I am aware of.

I also have a stainless wire braid covered fuel line from the firewall bulkhead fitting to the fuel rail on the engine. I have seen no damage to it. The fact that your wire braid on the fuel line has been burnt suggests that it might have intermittently served as the engine ground at one time or another. The braid must not have conducted a large current for very long or it would been destroyed completely. I can't think of a worse place to have an uncontrolled resistance heater than on that fuel line. Verifying the integrity of the ground from the engine to the airframe and from the battery to the airframe certainly seems like a worthwhile endeavor.

Depending on the details of the alternator installation, an intermittent connection inside the battery also might be a possibility although this would not explain the damage to the fuel line braid.

FWIW

Steve Boese

RV6A, 1986 13B NA, RD1A, EC2