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  #11  
Old 11-02-2018, 09:20 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Hartzell has done testing of electronic ignition in the past (it was done in a partnership at Van's) and and the test results surprised everyone. The results proved that ignition timing advanced beyond the standard 25 deg. (typically goes along with electronic ignition) can have a significant influence on the engine/prop resonance signature. I imagine that Hartzell's intent with this document is to warn that they have not done any testing on the 390 and that the influence could be more than it was on the parallel valve 360 ( which was worse than it was on the 320).
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  #12  
Old 11-02-2018, 09:30 PM
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The IO-390/Hartzell BA test mule was Marc Cook's Sportsman. See the November 2006 issue of Kitplanes for the article titled "Good Vibrations, Bad Vibrations". Subscribers can download it at kitplanes.com

Propeller fatigue is real.
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  #13  
Old 11-03-2018, 09:02 AM
Stockmanreef Stockmanreef is offline
 
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So if this is a real issue, then I imagine one P Mag with one regular mag would be just like two P Mags. Or am I wrong? With this in mind, why would Van's have the option for P Mags. I my engine build starts in a few weeks and I would like to know if I should change the configuration.

I am very confused.
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  #14  
Old 11-03-2018, 10:00 AM
mturnerb mturnerb is offline
 
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Quote:
Originally Posted by Stockmanreef View Post
So if this is a real issue, then I imagine one P Mag with one regular mag would be just like two P Mags. Or am I wrong? With this in mind, why would Van's have the option for P Mags. I my engine build starts in a few weeks and I would like to know if I should change the configuration.

I am very confused.
I guess the questions for me would be:

1. What are the potential long (and short) term issues that might arise as the result of changes in engine-propeller resonance?
2. Can the issues be addressed by adjusting pmag timing?

I have the same configuration as you - one mag/one p-mag - and no intention to change at this point as my panel/harness are done and it would be too much trouble to change....
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  #15  
Old 11-03-2018, 10:03 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by Stockmanreef View Post
So if this is a real issue, then I imagine one P Mag with one regular mag would be just like two P Mags. Or am I wrong? With this in mind, why would Van's have the option for P Mags. I my engine build starts in a few weeks and I would like to know if I should change the configuration.

I am very confused.
What I would do; dual pMags and the Hartzell BA Prop. That is what I did on the RV-8A and will doing on the current RV-8 project. I offer that Hartzell guidance put out years ago on electronic ignitions is worth reviewing. Such things as limit 2700 RPM operations to takeoff (even with mags on the RV-10 I pull back to 2600 RPM at 1000), limit high RPM and low MP ops, etc.

I never routinely flew with mags until the RV-10, and quickly learned to hate everything about them.

The other point - dont let the lawyer speak (not tested, etc,) override decision. This CYA stuff would lead to never flying - anything.

If it keeps you up at night, get a composite CS prop. Id do that before opting for mags.

Carl
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  #16  
Old 11-03-2018, 10:04 AM
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rv6ejguy rv6ejguy is offline
 
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Torsional vibration and propeller resonances are complex and ideally, each case would be tested. That's expensive and will probably not happen in reality.

Hartzell and Lycoming are simply saying that many combinations of propellers, engines and EIs have not been tested together and that could result in issues. If I were them, I'd be issuing the same cautions.

We don't know if these factors could have caused some other crank failures on Experimental engines in the past couple years.

A customer recently purchased a new Gen 4 Jabiru engine and was seriously considering EFI/EI for it but when he received the engine, it came with a caution on the warranty sheet saying the warranty was voided if ANY changes were made to the engine. He had to re-think the EFI and will probably not make that change until out of the warranty period. I can understand Jabiru's position.
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  #17  
Old 11-03-2018, 11:27 AM
Stockmanreef Stockmanreef is offline
 
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carl--

aren't the standard Hartzell Props from Van's Blended airfoil?

thanks
ken
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  #18  
Old 11-05-2018, 12:12 PM
rvbuilder2002 rvbuilder2002 is offline
 
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As has been mentioned already..... the cautions about torsional vibration are far more than lawyer speak.
It is very real. If tests haven't been done on a specific configuration, then everyone doesn't know what they don't know.

This also can not just be dealt with intuitively.
It has been suggested that keeping RPM's within the normal range will keep you safe. Not necessarily true.

It has been many years since i was involved with some of the testing, but if I am remembering correctly, the most serious RPM's were on the low end of what might be used for cruise flight (2000 - 2300) with moderate MP and advanced timing (read the original Hartzel doc. for more details).
Point being.... without testing there is no way to know what problem areas might exist.
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  #19  
Old 11-05-2018, 06:27 PM
scsmith scsmith is offline
 
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To the OP's original question, there is one aspect of installing Pmags that the FAA does actually care about. You will get a 40 hr phase I test period rather than a 25 hr phase I test period.

If you have a completely conforming certified engine and prop combination, you get a 25 hr test period.

This point is moot if the engine is already experimental in some other respect.

The angle-valve IO-360 which famously has a "yellow" RPM zone from 2050 -- 2350 RPM with the older type Hartzell C/S prop but no such restriction with the BA prop also has the same admonition about electronic ignition. I bet we are testing this combination extensively in the field as we speak. Problems? I don't know.
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  #20  
Old 11-06-2018, 08:11 AM
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rvator10 rvator10 is offline
 
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does the Hartzell recommended propeller release now = 25 hours of phase 1 flying instead of the 40 hours non-certified propeller combination?
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