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  #1  
Old 08-22-2021, 09:12 AM
CaptBob CaptBob is offline
 
Join Date: Aug 2021
Location: WINDERMERE
Posts: 3
Default Extended Cross Country RV-12 Configuration

I’m an RV newbie but experienced E-AB Velocity builder -- custom Turbocharged TNIO-550N Velocity XL/RG/XC with 1500 hrs from Mt Denali to the British Virgin Islands.

I’m interested in building an E-AB RV-12 with a Rotax 915iS engine and configured for long distance, high altitude cross country use -- like my Velocity but about half the TAS!

Some of the most important modifications for the RV-12 would be the Rotax 915iS turbo engine, the addition of oxygen, and a larger fuel tank.

My experience is that cruising in the low flight levels not only provides the most efficient TAS conditions (depending on winds aloft), but also the advantage of being above most weather, and the important flight safety consideration of having 2x to 3x the ‘energy’ and glide range that provides many more safe emergency landing alternatives, options and troubleshooting time.

My primary questions are:
1) would there be insurmountable physical challenges installing a 915iS instead of the normal 912iS engine (like the firewall size or the stepped firewall configuration, etc.) – I understand I will have to completely redesign and fab my own engine cowling,
2) would anyone expect any particular issues with high speed flutter and/or envelope extension during a Phase I flight test issues aimed at (among other things) extending the Vne up to something more like 150 to 160 KTAS -- I understand also of course that major weight and balance adjustments will need to be made to compensate for the greater engine and prop weight, additional fuel, etc.?

Does anyone have any experience with the 915iS on the RV-12, and/or other suggestions or thoughts with regard to the issues I might encounter in the build as well as in the high altitude (e.g., FL180), long distance (800+ NM) cross country flight use case?

I'm just starting to consider the possibilities seriously and would appreciate any experienced RV user inputs or suggestions.

Thanks,
Bob Jackson
N2XF
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  #2  
Old 08-22-2021, 10:54 AM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
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Location: Hinckley, Ohio
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Quote:
Originally Posted by CaptBob View Post
My primary questions are:

2) would anyone expect any particular issues with high speed flutter and/or envelope extension during a Phase I flight test issues aimed at (among other things) extending the Vne up to something more like 150 to 160 KTAS -- I understand also of course that major weight and balance adjustments will need to be made to compensate for the greater engine and prop weight, additional fuel, etc.?
Let me be the first to join the chorus... Design limitation for the RV-12 is Never Exceed VNE red line = 136 KTAS per POH. I suspect Van's may have very good data to back up this spec...
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  #3  
Old 08-22-2021, 11:07 AM
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Mel Mel is offline
 
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Location: Dallas area
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Not sure I understand your purpose for using the RV-12 design for your mission.

I think your needs far exceed the design limitations of the RV-12. The RV-12 was specifically designed around the Light-Sport limitations and exceeding ANY of the design parameters would be unwise in my opinion.
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  #4  
Old 08-22-2021, 11:26 AM
12vaitor 12vaitor is offline
 
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Location: Panama City, FL
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You should change your focus to an RV-9, its mission profile is more in line with your requirements for speed, payload, and altitude. The 915 would fit in the design power range and expected empty weight you are most likely looking at.

With everything you want to add, I expect it would push the RV-12 gross weight 150-200 lbs past the 1320 lb design rating.

John Salak
RV-12 N896HS
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  #5  
Old 08-22-2021, 04:51 PM
CaptBob CaptBob is offline
 
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Location: WINDERMERE
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I know the RV-12 was designed primarily for the LSA class, however I believe the airframe has a lot more potential for extended cross country use when built as an E-AB aircraft than you are giving it credit.

No doubt I would be building it (as an E-AB) with significantly higher max gross weight and Vne limitations (than as a Light Sport). Also, the fact the RV-12 has dry wings that are easily/quickly removed is also an important positive factor in my interest in it for long distance cross country trip use -- since when you break down far from home it’s great having the option to quickly and easily disassemble it and trailer it back home for repair, rather than buying new tools, finding a place for you and the plane to live, and the time to fix it away from home. Been there, done that.

Unless the RV-12 has inherently sloppy control surface hinging (which I highly doubt) or they can not be readily balanced, I see no reason why standard E-AB flight testing can’t be down with incremental flutter testing to extend the Vne well above even the cruising (and ‘downhill’) airspeeds achievable as configured with the bigger 915iS engine.

What little I’ve seen of the RV-12 in person so far, it appears to me like a very well engineered design that has no obvious inherent issues preventing it from being built as an E-AB aircraft and used for long distance, high altitude cross country flights as I envision.

Bob Jackson
N2XF
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  #6  
Old 08-22-2021, 05:12 PM
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Mel Mel is offline
 
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PM sent...........
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EAA Flight Advisor/Tech Counselor, Friend of the RV-1
Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
USAF Vet, High School E-LSA Project Mentor.
RV-6 Flying since 1993 (sold)
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  #7  
Old 08-22-2021, 05:57 PM
NinerBikes NinerBikes is offline
 
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No need to reinvent the wheel.

The material thickness of the aluminum on the wing's ribs and spars are thinner than that of a RV-9 or RV-7, which are designed for the air speeds you envision.

The RV-12 comes up light, for a reason.

A better idea would be a Sling Tsi, which is designed around the Rotax 915iS power plant.


You are an Aeronautical Engineer, correct? Just asking, as that's what your profile says.
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  #8  
Old 08-22-2021, 07:48 PM
CaptBob CaptBob is offline
 
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Great input WRT the RV-12 rib and spar aluminum thickness, NinerBikes! That's the kind of specific insight I'm looking for.

I believe I read on the website that the RV-12 is an aerobatic airplane -- I would assume it's pretty easy to exceed Vne on the backside of a loop if you aren't careful about holding in the G-loading, correct?

Bob Jackson
N2XF

PS I'm actually a lot more of an Electrical than an Aero engineer, and although I do have a MS in Aeronautical Systems (courtesy of the Navy) my aerodynamics theory is not that strong!
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  #9  
Old 08-22-2021, 08:04 PM
FlyingDiver FlyingDiver is offline
 
Join Date: Feb 2019
Location: Southwest Florida
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Quote:
Originally Posted by CaptBob View Post
I believe I read on the website that the RV-12 is an aerobatic airplane -- I would assume it's pretty easy to exceed Vne on the backside of a loop if you aren't careful about holding in the G-loading, correct?
The RV-12 is NOT aerobatic.
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  #10  
Old 08-22-2021, 08:05 PM
rgmwa rgmwa is online now
 
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The RV-12 is not aerobatic. (+4, -2g).
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