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RV 14 IO390 BA Prop Dual P Mags

Hello, Would appreciate comments with regard to the use of Dual PMags on a BA Prop Metal 2 blade(Hartzell) on the Thunderbolt IO 390 or similar. Although building a 14, would gratefully appreciate comments from any RV type with a similar prop, engine, and ignition system. Note my fuel lnjection system is a FM 150.
Completing the build in the U.K. under the auspices of the LAA.
Looking for current operational experience of the above configuration to help justify the initial U.K. experimental operation of the Hartzell 2 blade metal BA prop on the 390 with dual P Mags.
Initial proposal intends to have prop limitations similar to those originally applied to the IO 360 with additional full dynamic balancing and also additional annual inspections of the prop to establish or minimise that no adverse damage is apparent due to unwarranted vibration harmonics. If possible also make annual vibration analysis of similarly operated props on a comparison data basis?
Currently the LAA require the prop to have undergone the required certification vibration testing as required under the US AC, this has not been undertaken in the above configuration, hence the request for operational experience of such operations from within the US RV fleet which may have a similar configuration.
 
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Use of PMags on IO390

Hi Perhaps as no reply to query, a listing of prop type and ignition on the IO 390 for the RV 14 and other types would be helpful. I note there is another thread requesting help on propeller choice for the IO 390?
 
The ignitions work well, if they are timed (configured) properly.

P-mags are different than standard mags, make sure you understand how they work.

Here is a tread that might help.
 
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I hope to be able to let you know about this combination in a few months. I am in the "final" stages of building.

I have the following:
IO390 thunderbolt
FM-150 (modified snorkel opening to 3" as per Airflow Performance suggestion)
Dual Pmags
Hartzell two blade 72"
EI commander to keep track of data from Pmags (https://eicommander.com) and real time adjustments

cheers
ken
 
Not sure what you need but...

...I have been flying my RV-14 for about 100 hours now. I have dual PMags and a Hartzell aluminum blended airfoil constant speed prop (72?) which I ordered from Van's (C2YR-1BFP/F7497-2). The first 75 hours were flown with a Superior XP-400. I had the prop dynamically balanced at 40 hours. The airplane flew flawlessly with no detectable vibration issues prior to balancing and I noticed no difference after dynamic balancing. I replaced the XP-400 with a Barrett-built IO-390 due to the recall and have about 25 hours on that combination. It is running as well as the XP and I have no noticeable vibration. I have not yet had the prop balanced again but will be doing so soon.
 
I have similar circumstances to Jeff with the same experience. I had 500 hours on a Superior XP-400 and now have 65 hours on a Lycoming IO390, both with the Hartzell 74" (on A model). Balanced the prop on the first engine, haven't yet on the second. No negative experience (prop wise) and no prop limitations (RPM or power) in operating conditions.
 
One more data point as Keith, only started with Lycoming TB IO-390, dual PMAG and same prop. I attempted to do a dynamic balancing at around 30 hours and the vibration was spot on, the A&P said any attempt to change it will probably make it worse. The engine runs really smooth. I have now about 125 hours on it.
 
My RV-14 has the IO-390 Thunderbolt with the AFP FM-150, 72? Hartzell BA prop and dual P-Mags. Prop was dynamically balanced at 2,400 RPM. No problems operating with this configuration and I?m at about 100 hours. I?m not operating under any prop limitations similar to the IO-360?s and I have not seen anyone else doing that.
 
I doubt dynamic balance is relevant to the LAA's concerns. The likely concern is resonant blade vibration and its effect on long term fatigue life.

The BA/IO390 combination was subjected to a standard Hartzell strain gauge survey some time ago. Blade loads, vibratory and otherwise, were found to be low enough that the combination was approved without operating limitations. The entire process was documented by Marc Cook and published in Kitplanes. The article is available as a download for subscribers.

However, the survey was done with magnetos and fixed timing. The new question is what blade loads might be with advanced timing, which can significantly change the average point of peak cylinder pressure, and thus crank torque at any given point of rotation.

Think of it this way. The aluminum blade can ring like a bell. The change of ignition timing is something akin to striking the bell with a different hammer.

The LAA's "show us similar installations" approach isn't unreasonable, but the only absolutely sure approach is a strain gauge survey.

Now the (probably) good news. Prop manufacturers do expensive surveys when they expect the tested combination to be a popular seller. Lycoming has just released documentation for the IO-390D, a model equipped with their proprietary version of the SureFly ignition system, aka "Lycoming EIS". It has a pre-loaded variable timing schedule. They won't tell us exactly how far it advances or when, which is silly corporate nonsense; it will be trivial to measure in the field. However, it's probably not hugely different from the P-mag's B advance schedule, and any given timing advance is the same for all. Being a certified engine, it's just a matter of time before Hartzell surveys the EIS-equipped 390D with a BA.

Mike, you have contacted Hartzell, yes?

EDIT: Should have said A-schedule.
 
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... It has a pre-loaded variable timing schedule. They won't tell us exactly how far it advances or when, which is silly corporate nonsense; it will be trivial to measure in the field. However, it's probably not hugely different from the P-mag's B advance schedule, and any given timing advance is the same for all....

The P-mag "B curve" should never be run in any modern Lycoming engine!

The "B curve" (No jumper) starts at 30.8 degrees BTC for takeoff settings and advances out to 39.2 degrees when manifold pressure drops off.

Even the "A curve" is way too much advance for an angle valve engine, either the IO-360 or the IO-390.

The "A curve" (Jumper in) starts at 26.6 degrees for takeoff and goes out to 35.0 degrees. (They advance 1.4 degrees more than the "Max Advance" setting.)

The standard angle valve engines should have their timing set to start at 20 degrees BTC for takeoff and this is the reason for my earlier post on this thread about making sure the P-mags installed in an IO-390 are configured properly.

This can be done by "clocking" the P-mags or setting the configuration with Emag's ICAD program or our EICommander, which Ken mentioned in his post.

The angle valve engines are really good at cooling and the wrong timing doesn't always show up has high CHT's like it does on a parallel valve engine. Never the less, this doesn't mean you aren't damaging your engine.

Please, if you are running P-mags, make sure your timing is set correctly! They are great ignitions and will give you trouble free service, if setup properly. Feel free to contact me, if you have any questions.
 
Because the MT is a wood/composite propeller, LAA LAA are happy with dual P-Mags. They have a big issue with metal propellers.
 
Mike, you have contacted Hartzell, yes?

Don't mean to answer for Mike, but I did talk to Hartzell about my prop/engine and PMAG to inquire if there was any limitation. Although I did not emphasize on the EIS, they said there is no limitation on the BA. It was a short conversation on this subject.
 
Because the MT is a wood/composite propeller, LAA LAA are happy with dual P-Mags. They have a big issue with metal propellers.

Not my experience on three RVs running the Hartzell BA prop with dual pMags.

Is there data to support your claim? For me there is no better prop value over the Hartzell BA.

Carl
 
Nobody is questioning the value of Hartzell BA's. The issue here is the S-N curve for aluminum.

My first call would be Les Dowd.
 
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Not my experience on three RVs running the Hartzell BA prop with dual pMags.

Is there data to support your claim? For me there is no better prop value over the Hartzell BA.

Carl

UK thing.......

Our chaps don't like EIS and metal props.

No problems with wood/composite.
 
Hartzell Contacts

Affirm, I made contact with regard to the 72 inch BA and the use of Dual P mags on the IO390, in fact single P Mag use would also apply under the auspices of the LAA. I initially received a helpful response from Les Doud (RV Builder and currently Hartzell Air Safety Investigator) suggesting a conservative approach to propose restricting operation to 2700 rpm apart from take off and during normal operation restrict voluntarily to:
1. Do not operate above 24" between 2350 and 2550 RPM
2. RPM redline of 2700, period. Do not exceed 2700 RPM for any reason, and limit ops at 2700 for takeoff and high performance if feasible.
I made the proposal to the LAA as above who independently contacted Hartzell, note Les Doud was not consulted, and received from other sources in Hartzell, the following:
?At this time we do not have any vibration data to support this installation. As such, Hartzell can make no claim to the suitability of the HC-C2YR-1BFP/F7497-2 propeller installed on the IO-390 with P-Mag Ignition. This includes P-Mag units set to the standard base timing, which is fixed in the primary engine operation range.

As an aside, Hartzell has seen some significant variations in propeller vibratory characteristics caused by changes to ignition systems. The vibratory change is extremely difficult to predict with our limited understanding of many of the ignition systems available to the market. This is compounded by the results of some testing we have completed that shows that a change in the ignition system may affect the vibratory characteristics of Propeller A, but not Propeller B. This topic is of great interest to us and we are actively working to try to characterize what effect systems such a P-Mags have on propeller vibration.?
As a consequence of the above my request for an ?accepted? operation of my proposed engine prop ignition system remains pending on the applicant , myself, since the current LAA view is as follows:
It is our policy with alloy-bladed propellers that the manufacturer?s installation advice is followed due to the possibility of fatigue failure ? clearly something that we want to avoid. We rarely say an outright ?no? on proposals, and the same is the case here: if you can provide a justification that satisfies ourselves and Hartzell that this engine/propeller combination is not going to suffer from fatigue failure of the blades then that?s great: at the current time we don?t have that justification.
Hence I am currently researching to provide such justification. My current view is I can make a justification at least to the LAA, even if all in Hartzell are unlikely to support such ops under the current test status! However, all help and guidance from this forum is much appreciated. The data may eventually be available with the introduction of the certification of the IO D model with the BA.
In addition I have requested Hartzell for any relevant safety data that they are able to share on the BA prop with P MAgs or electronic ignition, none has been made available.
 
That's all you're likely to get from Hartzell for now.

For those currently flying the combination, be smart. Follow Dowd's conservative approach outlined above, and inspect your leading edges before every flight. A sharp V-shaped nick has a stress concentration factor of around six...and here vibratory stress is your mortal enemy.

Vibratory modes. Each blade is a cantilever beam. The twisted airfoil shape, as well as centripetal force, make the natural frequencies and mode shapes harder to predict than the nice theoretical examples presented here. That's why conservative propeller manufacturers still do strain gauge surveys.

Note how each mode is excited at a particular input frequency, while at another frequency it is not excited at all. And take a close look at the 2nd harmonic, starting about 1:40.

https://youtu.be/Z_JSNxNXEjo

Cantilevered beam begins at 56 seconds into the video.

https://youtu.be/kun62B7VUg8

Now some real fun. Wait until dark and fire up a variable rate strobe. You can see things about props which may cause you to quit flying.

https://youtu.be/AA6gWHu7GRs

Many readers believe composite props have no vibratory concerns. Sorry, no...everything vibrates. And the S-N values (stress vs cycles) for composites vary with construction and material. Here are some sample S-N's from Niu's Composite Airframe Structures. Note the steadily declining values for epoxy/S-glass and epoxy/E-glass are very much like aluminum.

S-N%20for%20Composite%20and%20Aluminum.jpg


The best thing about composite props is that they should typically present as a relatively benign failure, i.e. show obvious cracks before flying apart. Aluminum blades, not so much.

Same is true of wood. Here's an experimental prop which split while running on the test stand. The failure has two factors. One, look close at the split line. See how part of it has wood fiber torn from the opposing surface, while the majority of the split is smooth? The smooth part is bond line failure. (I'm not buying any more props from this guy.) Two, the failure happened right at the RPM which was predicted to exhibit the maximum amplitude of torsional vibration, i.e. a powerful forcing frequency. If one of the blade's natural frequencies happened to match that particular forcing frequency, it would resonate like you see in the videos. The good part is the failure mode. Aluminum props tend to throw a chunk off the end of the blade. The wood prop just split.

GlueFailure1.jpg


This is an experimental installation being surveyed by Hartzell. The transmitter board is bolted to the back of the prop. The red lines are conductors leading to strain gauges. You can see some glued to the face of the prop on the lower left.

Prop%20test.jpg


Yes, I think we are entirely too cavalier about props in the EAB world.
 
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Thanks for Information

Many Thanks for those that responded with your configuration details , I now have some evidence that the configuration is in use with some validated hours of operation ahead of my proposed use. I will however propose to operate to the limitations suggested by Les Doud of a Hartzell. In addition I will propose routine and annual inspections above those mandated. Any suggestions as to what these might include other than those mentioned in my original post would be appreciated. Further posts of those utilising the configuration also appreciated. Thanks also for those that added knowledge and information. Eventually I would hope that the 390 D model will provide the elusive strain data that the BA is currently missing with EI and of course P Mags.
 
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