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  #1  
Old 11-17-2021, 08:37 AM
WJaviation WJaviation is offline
 
Join Date: Jul 2020
Location: Pensacola
Posts: 19
Default First Engine Start Trouble (Solved!)

Hi everyone,

I finally got my engine started after 10 unsuccessful starts. I thought id give a quick write up of what I saw so that maybe another builder might not stress as much as I did.

Master on, Lane A and B switches on, the fault lights illuminate for 3 seconds each and then extinguish. This is as described in the Rotax Manual. Then I turn on the #1 fuel pump. I get good fuel pressure at 43.5 PSI. Throttle at exactly 50% as indicated on the Engine Display page (Garmin G3X). On engine start the engine fires up immediately and with positive oil pressure. within about 2-3 seconds it reaches 2700 RPM. I release the key before this and the engine is running on its own for about a second.

As it hits 2700 RPM (about 1 second of running), the Lane A fault light illuminates solid. RPM rapidly decreases. Then the Lane B fault light illuminates. Then the engine totally quits. Both Lane lights remain illuminated and the engine is stopped. The CAS also shows an "ENGINE ECU" red Message. The FADEC page shows a "Caution" for both Lane A and Lane B.

Ive included pictures of the displays from after the event. My very basic understanding is that the lane fault may have to do with the generator swaps that take place around 2500 RPM, but I have no idea how to troubleshoot.

After a day of deep dives in the pubs..

I posted to Rotax-Owner forums my entire story and got a response from a guy named Bill. He claimed that the "dual Lane caution" is normal. He said that when the engines are new like this one, the "A side" injectors are full of air. The Engine fires up on the B side injectors only (only one injector per engine). Depending on the engine, this could or could not be enough fuel to get the engine sustained. By repeatedly getting the engine to "swap" to the gen A around 2500 rpm, this brings the A side injectors online and pushes fuel through. But before the fuel gets through, it pushes air in and screws up the mixture. The engine/ECUs panics and shuts itself off because it can't find where this air is coming from.

Bill suggested that I just keep trying to start it. He claimed that if I was making it "past the key/start release" point of the start process, and the engine was running on the generators, Even for a second. Then it will run, it just needs to be given the chance.

He was right! In total I needed 10 starts, with the Lane lights kicking on each time for the fuel injectors to "get purged". It finally started on the 11th attempt. I ran it solid for 3 minutes, shut it down, and then started again with no issues. I think this is a happy engine now!

I think one of the possible key symptoms is the "Lane A and B Caution" warnings. The Lanes can't figure out what's wrong so they simply say "caution".

I couldn't find any specific pages in any of the Pubs to verify Bill's theory, but the fact that he confidently told me it would work, and it did...means something.

Id love it if Scott or any of the other engineer types might be able to offer any other explanations. Maybe even add a note in the PAP suggesting that it may take several start attempts to get working.

If not, then hopefully this post will help someone out in the future.
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  #2  
Old 11-18-2021, 09:27 AM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,667
Default

I conferred with our SLSA production guys about their experience with first engine starts (they have done a lot of them....), and their experience matches up with mine.
That it is fairly typical for the engine to immediately die after the first start, and occasionally it will do it a second time, but never more than that.
So usually after it dies on the first attempt, it will run normally on the second attempt.

This is the first time we have heard of it taking more than a couple of tries.

Proper throttle position is important though since it is mentioned that an EFIS displayed value of 50% was being used, that is not likely to be a factor in this case.

Chart/graph from the Rotax documentation provided below for future reference.
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__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop Manager
FAA/DAR
RV-6A (aka "Junkyard Special ")
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  #3  
Old 11-19-2021, 12:33 PM
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hamblin10 hamblin10 is offline
 
Join Date: Aug 2021
Location: Owasso, OK
Posts: 10
Default

You said the throttle was at 50% but the screen shot shows 19%. Was that after pulling the throttle back?
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Private Pilot/A&P/Aerospace Engineer
RV-12iS in progress. N993EZ
Build 121398
Empennage kit ordered 9/30/21
Wing kit ordered 11/8/21
Owasso Oklahoma

https://eaabuilderslog.org/?s=MYRV12
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  #4  
Old 11-19-2021, 08:03 PM
WJaviation WJaviation is offline
 
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Location: Pensacola
Posts: 19
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Yes, I always started at 50% +- 5%. When I finally got it started, I had to advance the throttle past 50% during cranking to get it to fire up.
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  #5  
Old 11-19-2021, 08:21 PM
WJaviation WJaviation is offline
 
Join Date: Jul 2020
Location: Pensacola
Posts: 19
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Quote:
Originally Posted by rvbuilder2002 View Post
I conferred with our SLSA production guys about their experience with first engine starts (they have done a lot of them....), and their experience matches up with mine.
That it is fairly typical for the engine to immediately die after the first start, and occasionally it will do it a second time, but never more than that.
So usually after it dies on the first attempt, it will run normally on the second attempt.

This is the first time we have heard of it taking more than a couple of tries.

Proper throttle position is important though since it is mentioned that an EFIS displayed value of 50% was being used, that is not likely to be a factor in this case..
Hi Scott. I did everything I could think of to verify to correct start procedures. I checked the FADEC page to verify my throttle position for each start. Checked my battery voltage to confirm that I was absolutely over the min voltage to start. And made sure to run the main fuel pump for long enough to get the required fuel pressure (~43.5psi).

I held the key long enough for the engine to run on its own. Even then it only ran for a second or two. After 10 start attempts, it finally ran steadily. The only explanation I have is from the gentleman (Bill) at the "Rotax-Owners" forum. I'll attached the link to the thread below:

https://www.rotax-owner.com/en/912is...t-engine-quits

I'm open to ideas on what I may have down wrong to demand so many start attempts. I quadruple checked every connection and fitting and wire and the only thing that worked, was to keep trying.

I don't intend to say that my experience is the norm...but rather to say that it's a data point on a spectrum of other first engine starts!
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  #6  
Old 11-20-2021, 02:26 PM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,667
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Quote:
Originally Posted by WJaviation View Post
Hi Scott. I did everything I could think of to verify to correct start procedures. I checked the FADEC page to verify my throttle position for each start. Checked my battery voltage to confirm that I was absolutely over the min voltage to start. And made sure to run the main fuel pump for long enough to get the required fuel pressure (~43.5psi).

I held the key long enough for the engine to run on its own. Even then it only ran for a second or two. After 10 start attempts, it finally ran steadily. The only explanation I have is from the gentleman (Bill) at the "Rotax-Owners" forum. I'll attached the link to the thread below:

https://www.rotax-owner.com/en/912is...t-engine-quits

I'm open to ideas on what I may have down wrong to demand so many start attempts. I quadruple checked every connection and fitting and wire and the only thing that worked, was to keep trying.

I don't intend to say that my experience is the norm...but rather to say that it's a data point on a spectrum of other first engine starts!
Hi Wes,
My post wasn't meant to pass judgment on what might have been the cause of your engine start difficulties.
I don't really have any ideas what might have caused it, and it sounds like you did everything you could to remedy the problem.

I just meant to point out that your experience is a rare case among RV-12iS builders, but you posting your experience here may be of value in the future if another RV-12iS builder experiences this.
I hope you have a good experience with the engine from now on.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Hubbard, Oregon
Van's Aircraft Engineering Prototype Shop Manager
FAA/DAR
RV-6A (aka "Junkyard Special ")
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