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RV-14A operating experience.

rvbuilder2002

Legacy Member
Mentor
In light of the number of negative comments in the past regarding the decision to choose the IO-390 as the focus engine for the RV-14, out of concern for it being a fuel thirsty engine, and the opinion that the airplane suffers in performance compared to an RV-7; I thought I would give an update on our experience now that we have been operating it for a while (airplane has surpassed 500 Hrs).
Having just made a 2000+ mile round trim to the Copperstate Fly-in, I can say that I never cease to be impressed by the airplane.
Yes I am probably a bit biased, but I think the feeling is entirely valid.
My wife has traveled with me a lot in RV's since we completed our first one in 1993.
This was her second long trip in the RV-14 and she could not stop talking about how much more comfortable she felt with the additional cockpit room. The baggage space and payload capability makes this type of trip much easier for us (we need to carry a lot of display materials and equipment with us).
At upper cruise altitudes (10,500 - 11,500) we got true airspeeds of 170 - 172 Kts while burning 8.7 - 8.8 GPH. This was while operating slightly lean of peak (.2 - .5 GPH).
We have flown the airplane quite a bit on trips along side of the RV-7A prototype. At lower altitudes the RV-7A is a little bit faster, but at higher altitudes the tide is turned and the higher aspect ratio wing and different airfoil turn the advantage to the RV-14A.

I think you RV-14 builders are really going to like this airplane......
 
Thanks for the report.

Just wondering: what was the powersetting at the 8.7 - 8.8 fuelburn?
Also: what the indicated percent power?
 
Thanks for the report.

Just wondering: what was the powersetting at the 8.7 - 8.8 fuelburn?
Also: what the indicated percent power?

2400 RPM / full throttle
MP at those altitudes/temps would be somewhere between 20 - 21 inches but I didn't take note of specifics (it will vary somewhat depending on air temp., etc.)
I didn't note the display % pwr, it is not displayed with our current screen configuration if you have the screen split 3 ways.
 
Simple answer, 63% power.

Remember that WOT is the most efficient way to run the engine, the RPM where it is smooth, and when LOP fuel flow determines HP. So that was around 133HP.

I am perplexed at why anyone would be complaining. The 390 seems the obvious choice. The fuel burn issue for most people is only a problem because they either have never learned or refuse to learn how to operate them properly.

Scott was operating properly ;)
 
With respect to the IO390 being thirsty, the Glasair Sportsman has proven a good test bed to analyze this claim. This airframe can be built in the TWTT program with a 180hp IO-360, a 200hp IO-360, or the engine that most builders choose, the IO390. Performance comparisons between the engines reveal that, of course, the IO390 will move the airplane faster as a result of its greater available power, but that speed increase comes with a fuel burn increase commensurate with the increased horsepower being used.

In general, with the Sportsman, flying a 180hp IO-360 and a 210-hp IO-390 side by side at the same speed and density altitude will produce very similar fuel burns, plus or minus the small variations attributable to slight differences in the airframes and their rigging as well as differences in pilot technique.

In short, the IO-390 isn't a particularly fuel-thirsty engine, in and of itself.
 
IO-390

I have the 390 in my 8 and routinely burn less fuel than my buddies 8 with a fadec system, and I can out run him. I love my IO 390!:)
 
Thanks for the information Scott. Stuff like this helps keep us builders motivated! Sounds like the perfect compromise in a two seat RV!
 
"negative comments in the past regarding the decision to choose the IO-390 as the focus engine for the RV-14"

Indeed ... one of the issues for me is not just the engine itself, but the lack of alternatives that will fit relatively easily in there. The XP-400 is the only one AFAIK.

Thing is these days there are plenty of engines like the IO-375, X-371 or X-409 that could also fit the bill ... if it weren't for the weight issue ...

Finally, the IO-390 is avgas only, an issue for some in north america, and an issue for everyone outside north america ... a strange choice from that point of view ... At least the XP-400 or whatever BPE will build for you can have mogas friendly low compression configurations ...

A FWF kit that will support the lighter engines (appropriate engine mount and cowl?) would certainly be a great seller I'd expect ...

This whole engine business is really driving me bonkers about choosing the RV-14!
 
Always interesting to receive a good report meeting expectations. But, Scott,
when the boys get done whipping up the taildragger version, immediately start fixing the one great shortcoming of the -14...utility.

A wife's happiness also has a proportional baggage component. The -14 desperately needs a baggage door to take advantage of the capacious baggage volume. It looks silly without one. It's a clumsy and awkward struggle up the wing with anything clunky and/or heavy, maybe passing it through the seat-roll bar gap in the bag area. Tip the seat forward and it's now in the way of stepping in. Try all this with a loaded, but melted ice, ice chest!

The tip-up slider on my -7 makes loading oh so easy. Stand on the ground and directly drop in The Big Bag. Maybe Van's can devise an open-able rear window. Something!

John Siebold
Boise, ID
 
A wife's happiness also has a proportional baggage component. The -14 desperately needs a baggage door to take advantage of the capacious baggage volume. It looks silly without one. It's a clumsy and awkward struggle up the wing with anything clunky and/or heavy, maybe passing it through the seat-roll bar gap in the bag area. Tip the seat forward and it's now in the way of stepping in. Try all this with a loaded, but melted ice, ice chest!

The tip-up slider on my -7 makes loading oh so easy. Stand on the ground and directly drop in The Big Bag. Maybe Van's can devise an open-able rear window. Something!
Actually, the RV-14 is the easiest to load baggage in of any of the 2 place side by side models. With the lower cockpit side rail, the opening between the rear seat support structure and the roll bar, is proportionally taller than all of the others. This makes it much easier to get most anything into the baggage area (including a cooler with water in it), and you don't have to lift it as high because of the lower cockpit side.
For this reason, and with the added weight, build complexity, and cost that would be induced by adding a baggage door... it is not likely to happen.
 
"negative comments in the past regarding the decision to choose the IO-390 as the focus engine for the RV-14"

Indeed ... one of the issues for me is not just the engine itself, but the lack of alternatives that will fit relatively easily in there. The XP-400 is the only one AFAIK.

Thing is these days there are plenty of engines like the IO-375, X-371 or X-409 that could also fit the bill ... if it weren't for the weight issue ...

Finally, the IO-390 is avgas only, an issue for some in north america, and an issue for everyone outside north america ... a strange choice from that point of view ... At least the XP-400 or whatever BPE will build for you can have mogas friendly low compression configurations ...

A FWF kit that will support the lighter engines (appropriate engine mount and cowl?) would certainly be a great seller I'd expect ...

This whole engine business is really driving me bonkers about choosing the RV-14!

Designing an aircraft for optimal performance and utility is a juggling act of compromises.
The engine choices for the RV-14 was narrowed to optimize the kit for the major majority of people.
Yes, that pretty much locks in the use of an angle valve derivative of the 4 cyl. Lyc. (because the parallel valve versions are too light) but that still leaves a lot of choices. The majority of the 200HP angle valve models can be used in place of the IO-390.
With creativity, it is possible to build up a just slightly lower compression version of the IO-360 engine to enable worry free use of mogas, and still have very good HP output.
 
Are there any cooling issues with the IO-390 in the RV-14a? What kind of CHT and oil temperatures have you witnessed? Thanks for all the great info and perspective, it helps tremendously.

Greg Novotny
Gig Harbor, WA
 
This is probably a fair comparison, dead stock 390 in a clean RV-8. The photo was taken in the last hour of a non-stop from OSH this summer, so remember, light on fuel, and solo. Anyway, 11,500, WOT, slightly lean of peak, cowl door shut.

Thoughts...

The 390 is not a fuel hog when operated with an eye toward conservation.

There is a penalty to be paid for the larger RV-14 airframe. If you need the space, pay the bill. If you don't, well, don't.

I'll bet RV-14's cruise cooling drag could be cut by half. Then if we put the little wheel in the back....

I wouldn't want less engine in an RV14. As noted, it would burn the same for the same speed in cruise. However, it would climb slower...and the cool air is up there.

I'd probably like a Superior/BPE 400 even better.

 
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I've found running 2300 instead of 2400 will dramaticly drop fuel flow with little speed penalty. Should be able to get 24-25 mpg instead of the 22.
 
I'm wondering if the lighter weight issues with a higher performance IO360 that matches the horsepower of the IO390 could be helped by use of inverted oil and smoke systems. Not sure how much weight these add but could it keep the CG within limits?
 
I'm wondering if the lighter weight issues with a higher performance IO360 that matches the horsepower of the IO390 could be helped by use of inverted oil and smoke systems. Not sure how much weight these add but could it keep the CG within limits?

You would need to make up for a weight difference of 35-40 pounds at the arm position of the engine C.G (~ 20 inches fwd of the firewall).
Any optional equipment added aft of that point would obviously have to be even higher in weight to get enough of a moment.

Some have suggested that enough compensation could possibly be made by installing air conditioning since the compressor is mounted out on the front of the engine. I haven't done any math, but I don't see how it could work. The compressor is no where near heavy enough to compensate for the lighter engine, and there are other components of the system would likely be reversing any gain from the compressor (in aircraft the condenser is typically mounted aft of the C.G.). Not to mention the extra money spent for the A.C. system, that would offset any savings gained by using a different engine.
 
Are there any cooling issues with the IO-390 in the RV-14a? What kind of CHT and oil temperatures have you witnessed? Thanks for all the great info and perspective, it helps tremendously.

Greg Novotny
Gig Harbor, WA

The trip I just made with the airplane had me flying in OAT's of 95 F. while in the Phoenix area. I can't give you specific #'s because in those conditions, with the flight profile that I flew, the temps were more than acceptable so I didn't take specific note.

The prototype currently has the same oil cooler as is used on the RV-10, remotely mounted and fed air with a 4" SCAT hose.

We have done gross weight climb tests at Vy, all the way to 10K ft in the same temp conditions and recorded acceptable CHT and oil temps.
 
So, what about a 540?

Where is John Harmon when we need him?

Seriously, I keep wondering about this. Seems like the perfect airframe, just like a Piper Dakota.
 
Engines & Fuel Options

Hello everyone. New to VAF. Flew demo RV-10 with Mitch Lock earlier this month. Is there any thought to fuel? Engine notwithstanding I see new fuel being tested and GA diesel piston engines coming on line. Looks like I'll be setting up for a RV-14 in two years. Makes me wonder about possible options out of Oregon. I'd hate to invest in a new plane only to change engines before it's economical.

Then again in another 20+ years I'll probably be too old anyway. I've not seen anything on this. Am I thinking too much or it already addressed?

Loved the RV-10 demo. Plane has smaller engine than kits and is far beyond my little C-150! Based on similarity I can see how a two seat RV-14 will be perfect for our needs. Not quite the same as jets but for my pocketbook and needs, hard to beat.

Not sure about tilt forward canopy, no baggage door, etc. but will take advantage in time. So far I see few items to kill it for us. Compared to factory birds, I like!
 
The RV-14 is designed around the IO-390, which is 100LL only ... though if the fuel industry and the FAA do manage to come out with 100+ octane no-lead fuel replacement, you'll be OK.

Otherwise the experimental engine manufacturers will sell you something similar that will take mogas, such as the XP-400 with lower compression, I believe.

Not sure what might exist as far as diesel options for the -14 ... the CD-200 is likely too heavy ... the SMA it's based on is 430 pounds to the IO-390's 310 ...
 
The RV-14 is designed around the IO-390, which is 100LL only ... though if the fuel industry and the FAA do manage to come out with 100+ octane no-lead fuel replacement, you'll be OK.

Otherwise the experimental engine manufacturers will sell you something similar that will take mogas, such as the XP-400 with lower compression, I believe.

Not sure what might exist as far as diesel options for the -14 ... the CD-200 is likely too heavy ... the SMA it's based on is 430 pounds to the IO-390's 310 ...

If 100LL went away tomorrow without a suitable replacement you would be able to install lower compression pistons in you're IO-390 or angle valve IO-360 and burn Mogas. When lycoming was developing the IO-390 the marketing data and press releases stated that they would be making a Mogas compatible version that was to be rated at 190 HP. Prior to purchasing my engine I spoke with a Lycoming engineer on the phone for about a half hour and asked him about the Mogas version. He said they did not go into production of the Mogas compatibe version due to the power to weight ratio. He said it was more economical to purchase and install a parallel valve 180 or more HP engine that would weigh less than the derated IO-390, and because of this they did not see a market for the lower output version. I did ask him if the low compression Pistons were available and he said they were not currently, but that if a situation arose such as the discontinuation of 100LL then they may make them available, or many of the custom engine shops can make some suitable low compression Pistons.

I honestly don't see 100LL going away anytime soon and when it does there will be a suitable replacement. I am all for running Mogas, which I did almost exclusively in the two LSA aircraft I owned, but the reality is when you actually go somewhere with you're airplane the chances of you finding Mogas at an airport is slim to none and you will end up burning AvGas anyway.

I really thought long and hard regarding the 100LL fuel requirement of the IO-390 before deciding to build a -14A, but I decided that the extra cockpit room and the much improved landing gear of the -14 were a much larger advantage than being able to burn Mogas during local flights.
 
Although I've had my doubts in the past, at this point I'm fairly confident we'll get a 100LL replacement as well ...

That's a good point about changing the cylinders ... I mean it's still a good chunk of change (Lycoming IO-390 cylinders are NOT cheap!), but it's an out should you need it. And indeed, if your IO-390 is experimental, you can put 3rd-party cylinders ... surely someone will want to fill that void were it to occur ...

Looking at my horizon for building, I might actually be able to hold off on an engine buy until 2018, assuming PAFI keeps to their schedule ... or at least we'll have a much better idea of where that stands ... same logic would apply to anyone in the planning stages of building a 14 ...
 
Although I've had my doubts in the past, at this point I'm fairly confident we'll get a 100LL replacement as well ...

That's a good point about changing the cylinders ... I mean it's still a good chunk of change (Lycoming IO-390 cylinders are NOT cheap!), but it's an out should you need it. And indeed, if your IO-390 is experimental, you can put 3rd-party cylinders ... surely someone will want to fill that void were it to occur ...

Looking at my horizon for building, I might actually be able to hold off on an engine buy until 2018, assuming PAFI keeps to their schedule ... or at least we'll have a much better idea of where that stands ... same logic would apply to anyone in the planning stages of building a 14 ...

You just need to change the Pistons to change the compression ratio, not the entire cylinder. :)
 
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