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KEG

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Page 45iS/U-02 of the KAI for my 12iS build simply states to install the starter relay with the hardware called out (two AN3 bolts and washers).

The Rotax Installation manual clearly states the relay "must be installed isolated from the airframe ground." Rotax's SI-PAC-017 (meaning of 'PAC unknown!) states, "NOTICE: Engine type ROTAX® 912 iS Sport and ROTAX® 915 iS A electric starter relay assy. housing and mounting tabs must be isolated from both airframe ground and EMS ground. For ROTAX® 912 (Series) and ROTAX® 914 (Series) the relay housing is normally connected to airframe ground (see relevant Installation Manual)

I see no indications of isolating the relay in any of the KAI pictures showing the relay or anywhere else in the KAI. I have not asked Van's tech support about this yet. Has anyone else researched this issue or found a solution for isolating the relay?

Anyone know what makes this starter relay so valuable ($200+)?
 
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You may want to contact Support and reference the KAI page and the Rotax SI-PAC

It would seem that this SI-PAC came out after the RV-12iS was engineered.. and I'm not sure either as to WHY Rotax wants you to use the dedicated starter relay ground lead. My only GUESS is that they want to make sure its using the correct ground (EMS ground or airframe ground) based on the operating condition of the Fuse Box.. and they do this by making you use this dedicated ground wire which may be internally switchable between the two grounding planes.

In fact, at KAI 46iS-09 Step 3, they explicitly have you cut and NOT use that ground wire. So, whatever the reason, it was an intentional decision to always use the airframe ground. Build on, but I'd bring that SI-PAC to their attention.
 
rcarsey said:
You may want to contact Support and reference the KAI page and the Rotax SI-PAC

It would seem that this SI-PAC came out after the RV-12iS was engineered.. and I'm not sure either as to WHY Rotax wants you to use the dedicated starter relay ground lead. My only GUESS is that they want to make sure its using the correct ground (EMS ground or airframe ground) based on the operating condition of the Fuse Box.. and they do this by making you use this dedicated ground wire which may be internally switchable between the two grounding planes.

In fact, at KAI 46iS-09 Step 3, they explicitly have you cut and NOT use that ground wire. So, whatever the reason, it was an intentional decision to always use the airframe ground. Build on, but I'd bring that SI-PAC to their attention.
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Thanks for the response. I have forwarded my post to Tech Support and will report on their response. Good observation on Step 3 cutting the ground wire in the harness. I hope that remains the proper procedure... I already cut mine off!
 
More info on this iissue. I have not heard back from Van's support yet. Someone on the Rotax Owners Forum posted that Kitfox makes a part to isolate the Rotax starter relay. I emailed Kitfox and received this in response, "Unfortunately with today’s climate.. We are only selling to our Kitfox Customer Community." My response back to them was, "I find that very disappointing. I would have expected more from the experimental, homebuilt community. This is an issue with a Rotax part, not your Van's competitor. Word spreads rapidly in the aviation community!" I don't think Van's would be so petty!
 
Another thought.... Maybe visit the KitFox forum and ask if someone would order part for you. If someone asked me, and supplier had issues, I'd order for them. Just a thought....
 
I look a look at the Rotax Installation manual to try and figure out what's going on. The diagrams there show that the Relay's ground connection goes to Bus A ground plane. This is likely because the power to activate the relay is coming from Bus A (the tiny generator that runs the engine) -- although I didnt see that clearly depicted.. but I think that's logical..

During start up, both power buses and both ground planes are joined together.. so the way its set up by Van's doesn't make (shouldn't make) any difference.

After the engine is running, and the ignition module tells the HIC module to split the buses.. If the engine dies (e.g. you turn the fuel pumps off), the buses will still be separate.. I would make a guess that in Van's setup, turning the ignition key won't activate the starter relay (power from Bus A, but ground on Bus B [airframe]). This doesn't really matter, because the ECU will be dead anyway.. and you'd either have to cycle the Master (to join the two buses again and give the ECU power).. or use the EMS Battery Backup switch to manually join the two buses.

If we hooked it up the way Rotax wants, I don't think it will make any difference. The ECU is still dead.. so no power is even provided to the ignition key.
 
Solenoid issue

Rob, You are obviously more well versed in electronics than I will ever be. Thanks for your interest and time in researching this issue. I have not heard back from Van's Tech yet. I emailed them instead of trying to explain all of the Rotax documents over the phone. It will be interesting to see if their analysis matches yours. I'll keep you updated and, thanks again!
 
Response from Van's

Van's Tech Support responded today regarding this issue... "The starter relay is to be installed as per KAI 45iS/U-02. Later in KAI 46iS-09, Step 3 tell you to cut the “Gnd Starter Rel” wire connector off of the Rotax harness and stow it. I don’t know the reason Engineering chose to install it against Rotax’s recommendation, but I suggest you stick to the plans."
 
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