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  #1  
Old 08-02-2019, 10:21 AM
DaleB's Avatar
DaleB DaleB is offline
 
Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,184
Default Soft start failure

Our RV-12 (engine SN 6775234) has an interesting failure.

The engine has the original ignition modules, with an added soft-start module that I'm 99% sure is the Bully Hawk soft-start module. There is no label on it, other than a QA/date code sticker. Per the original builder's instructions, we normally start on the A ignition only and switch on the B side as soon as the engine is running.

When cold, the first start of the day, it will not start on the A ignition. Crank all you want, it won't start. As soon as you turn on the B ignition, it starts right up. Run-up is normal, with both ignitions working fine. After the engine is warmed up, it will start on the A ignition only just fine. A couple weeks ago when it first happened, I started it 8 times in one day normally, after the first balky start.

We found the ground wire to the soft-start box broken off. Great!! That was an easy fix. Unfortunately, fixing it did not change anything at all. I made a test flight last night. The first time I had to turn on the B ignition to get it to start. I let the engine warm up, did a totally normal run-up, and flew a lap around the pattern. Shut down, and it would start on just the A side with no problem.

So, I think we have a bad soft-start module. It looks like this one is no longer made. The Rotax soft-start for this engine is around $1K, and would require a new flywheel and other parts -- I believe that means pulling the engine. Not really on our list of things we'd like to do, frankly.

Anyone have experience with this and/or have any suggestions? Or a Bully Hawk module for sale cheap?
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Dale

Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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  #2  
Old 08-02-2019, 10:46 AM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,635
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Dale,

I always start on both ignition circuits. Why do you start on one? Am I missing something?

Rich
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  #3  
Old 08-02-2019, 10:51 AM
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DaleB DaleB is offline
 
Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,184
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Quote:
Originally Posted by RFSchaller View Post
Dale,

I always start on both ignition circuits. Why do you start on one? Am I missing something?

Rich
It's an older 912ULS engine without the Rotax factory soft-start (ignition timing retard during startup). We have the green labeled ignition modules, so there is an aftermarket add-on soft start module on the A ignition only.

Not retarding the timing during startup can lead to engine kickback, which can destroy the expensive and difficult to replace sprag clutch.

This whole thing was fixed years ago, but after our engine was delivered. Upgrading to the newer ignition modules, or adding the new Rotax soft-start, would cost us a few grand and we'd have to pull the engine.
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Dale

Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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  #4  
Old 08-02-2019, 11:50 AM
sandpiper sandpiper is offline
 
Join Date: Nov 2009
Location: Independence, OR
Posts: 316
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Dale - I have a Bully Hawk I bought new that is unused. I bought it years ago when I wanted soft start. At the same time Rotax was having a special price for two ignition modules with soft start for just less than $1,000. The usual price is twice that. So, no need for the Bully Hawk.

Make me an offer that includes postage if you want it.
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John Horn (donated for 2020)
Independence, OR
LSRM-A, CFII
Rotax Service, Maintenance, and Heavy Maintenance Trained
Building an RV-12, N7878H reserved
Flying a Flight Design CTSW
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  #5  
Old 08-02-2019, 01:09 PM
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maniago maniago is offline
 
Join Date: Aug 2014
Location: Bowie MD
Posts: 875
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I dont know anything about your soft start system, but from an purely electrical stand point, I'd check the voltage you are seeing at the module when on ABuss. Sounds like with all the starts you mentioned, you got some heating or arching in a connection that increased resistance somewhere that logically doesnt exist in the BBuss wires. Just a guess, but easier to trouble shoot - ie run new wires as a test - vs buying something new.
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  #6  
Old 08-02-2019, 01:51 PM
sf3543 sf3543 is offline
 
Join Date: Jan 2005
Location: San Antonio, TX
Posts: 981
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I have an early RV12 on which I had to replace the ignition coils. (No soft start modules on this plane either.) Same symptoms as you are seeing.
I did the ice pack test to see if it was bad coils. If it doesn't start, put an ice pack on top of the coils for 15 or so minutes and then try to start it. If it starts after that, its the coil. I got this method from Lockwood aviation.
Anyway, I ended up replacing both coils with the newer soft start versions that Rotax now offers.
I did not have to do any flywheel mods or anything other than wire in the new modules.
Its been flying fine for about 300 hours since.
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Legend Cub
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  #7  
Old 08-02-2019, 02:32 PM
DaleB's Avatar
DaleB DaleB is offline
 
Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,184
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Thanks all for the suggestions. As noted, it appears to only involve the soft-start and not the A side ignition, since it runs on either one once started. And, it only happens when stone cold. Taxi for five minutes, it'll start right up every time for the rest of the day. My guess would be a failing part in the module. Any other time I'd cut it apart and do the repair, but I'm just not in the mood to try to un-pot and reverse engineer whatever the designer of this long-discontinued product hacked together.

John, I'll be flying out to lunch tomorrow with my co-owner. I'll PM you after we talk it over.
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Dale

Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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  #8  
Old 08-02-2019, 09:01 PM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,635
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Thanks, Dale. Now I understand.

Rich
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  #9  
Old 08-03-2019, 06:53 AM
mcems mcems is offline
 
Join Date: Apr 2008
Location: Salem SD
Posts: 152
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Wow Dale your just described the same symptoms I am experiencing. First start of the day on A ignition no go. turn on B ignition and instant go. After that everything works normally. Warm startup on A only no problem.

Now here is the interesting part. I just replaced my sprag clutch a few weeks ago. I had the original modules running with no soft start. So after all that work replacing sprag I decided it was time to spend the money and install a new module with soft start in it on the A switch. Well that is when the symptoms' you describe started for me. Again it only happens on the first start up of the day.

I did get 1000 hours on the plane before the sprag stated getting weak.


Brad Stiefvater
Salem SD
124BJ first customer built RV12 to be airworthied and fly.
Maiden flight 9/20/2009
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  #10  
Old 08-03-2019, 09:52 AM
Wolfgang Wolfgang is offline
 
Join Date: Dec 2018
Location: salida, co
Posts: 16
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My Rotax 912 ULS with the "Billy" soft start module is acting the same,,,,no start cold on A but when warm it works fine...not certain what to do????
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