[PabloSniper]

Hello gentlemen of the Vans Forum!
After several mistakes and some not-so-sensible suggestions, I believe this time I’ve hit the mark.
This is not my project, and I’m not claiming any credit for it — I’m just an aviation enthusiast who sees opportunities.
Robert Haag, a German engineer, built an RV-4 with a Rotax 915iS engine, using a new engine mount and a longer cowling to accommodate the lighter engine, which had to be positioned further forward from the firewall. And gentlemen, the result is truly a masterpiece.
Well, in order not to clutter this suggestion with images, I have made a YouTube video to explain this suggestion in detail.

Link to Kitplanes article about it: https://www.kitplanes.com/rotax-anyone/

However, as you can see in this post from Rotax, Robert has classified his RV as an ultralight, with a maximum takeoff weight of 600 kilograms ( 1,320 pounds)


Personally, I don't see any advantage in that, since Van's design specifies a maximum takeoff weight of 680 kilograms, or 1,500 pounds. So, I put together a table with the actual data of the standard RV-4 and Robert's RV-4 (considering the maximum takeoff weight as designed by Van's), along with three other variants with estimated data, including the 916iS, 914UL, and 912iS. It is worth noting that Robert's RV-4 is equipped with a parachute weighing 17 kilograms (approximately 37 pounds).





As you can witness, the Rotax engines give new life to the old RV-4. It transforms from being a one-and-a-half-seater into a true two-seater, with enough margin to fill the fuel tanks, load the baggage compartment, and still comfortably accommodate two heavy passengers.
Not to mention the fuel savings.

Possible issues to be addressed in this suggestion:

• But if Robert is already making the parts, why should Van's do it?
• Many builders do not trust third-party services, but if Van's offers it, it would have the full confidence of the public.
• But the RV-4 is an old kit, and demand for it is low compared to other models.
• The demand is low because assembling the standard kit takes about 2,000 to 2,500 hours, as its parts are not pre-drilled. If this kit were updated to the level of the RV-12, which requires only 800 to 900 hours to complete, it would have much greater appeal.

Not to mention that, with a Lycoming engine similar to the RV-8, it offers virtually nothing that the RV-8 doesn’t already provide.
The reduced cost of assembly (as the Rotax is cheaper than the Lycoming), the greater fuel efficiency, the increased useful load, and the reduction in total build hours would make this aircraft a sales success beyond even the most optimistic expectations.



I sincerely hope that this topic will receive the support of the community and that it will reach those responsible at Van's.
My best regards,
PabloSniper

P.S.: As you could see in the video, an Italian builder made an RV-4 with a Rotax 912 100hp.
However, I was unable to get in touch with him to obtain the performance figures.

Just to make it perfectly clear, I am not requesting a new aircraft design; I am only proposing an engine modification to an existing, well-established project, which has a large community of enthusiasts and is already renowned for its excellent flight characteristics.
I never imagined in my life that writing a topic on a forum could take so much time. It took hours and hours of research and video editing, I hope you like the result.

And now a message for someone responsible for Van's.
I'm not only going to buy one for myself, but I promise to dedicate my time and use my YouTube channel with around 50 thousand followers to promote your product here in Brazil.
Although we are a backward country, we have the second largest civil aviation fleet in the world, behind only the United States of America. The RV-10 is responsible for 73% of the civil aircraft here. And this proposed model would be a huge success in a poor and large country like ours.
We would have the possibility of making a transfer between one city and another, at a lower cost than in a car. And that is fantastic.

 

[Mel]

I'm not understanding why you would want to reduce the gross weight to 1320 lbs. Seemingly the only reason would be to bring it into Light-Sport parameters. But it would never meet the maximum cruise speed and minimum stall speeds of LSA, so why?

I also don't think the market would bear Van's "redoing" the RV-4 kit. The primary reason people reject building the -4 is for the restricted cockpit room, not the difficulty of the build.

 

[JonJay]

Vans discontinued all of the legacy models except the 3 which was re-engineered via CAD for their modern machinery. They would have to do the same for the 4. That would be very expensive, take years, and detract from their other projects like the 15, which still isn’t in production.
Your friends airplane is nice and it’s a great idea. I can see the appeal, but you might need to do it yourself or third party it.
Lycoming conversion for the Bucker’s was done in such a way. You could buy engine mounts, cowlings, airbox, etc… and upgrade your Bucker. Most of them flying in the US have done this.

 

[PabloSniper]

I'm not understanding why you would want to reduce the gross weight to 1320 lbs. Seemingly the only reason would be to bring it into Light-Sport parameters. But it would never meet the maximum cruise speed and minimum stall speeds of LSA, so why?

Personally, I don't see any advantage in that, since Van's design specifies a maximum takeoff weight of 680 kilograms, or 1,500 pounds. So, I put together a table with the actual data of the standard RV-4 and Robert's RV-4 (considering the maximum takeoff weight as designed by Van's), along with three other variants with estimated data, including the 916iS, 914UL, and 912iS. It is worth noting that Robert's RV-4 is equipped with a parachute weighing 17 kilograms (approximately 37 pounds).

Forgive me, but I didn't say that. I said I don't understand why Robert tried to fit him into that class.

 

[mburch]

the Rotax is cheaper than the Lycoming

Is it? Current engine pricing for an apples-to-apples comparison is hard to come by, but this distributor has the 915iS listed for $48.5k; the current Van's price for an O-320 with dual mags is $44.7k, or $47.5k for an IO-320 with P-mags.

 

[PabloSniper]

Is it? Current engine pricing for an apples-to-apples comparison is hard to come by, but this distributor has the 915iS listed for $48.5k; the current Van's price for an O-320 with dual mags is $44.7k, or $47.5k for an IO-320 with P-mags.

But in my specific case, I wouldn't use the 915, I would either use the 912iS or the 914UL.
The Lycoming sacrifices a lot of payload and fuel consumption.

 

[PabloSniper]

Vans discontinued all of the legacy models except the 3 which was re-engineered via CAD for their modern machinery. They would have to do the same for the 4. That would be very expensive, take years, and detract from their other projects like the 15, which still isn’t in production.

Ok, so let's suppose that Van's doesn't change anything in the kit, and that the standard kit still requires between 2000 and 2500 hours, while the quick-build kit takes about 1500 hours.
But what if they only offer an engine mount suitable for the Rotax?
And, obviously, a cowling for it as well."

Your friends airplane is nice and it’s a great idea. I can see the appeal, but you might need to do it yourself or third party it.
Lycoming conversion for the Bucker’s was done in such a way. You could buy engine mounts, cowlings, airbox, etc… and upgrade your Bucker. Most of them flying in the US have done this.

That wouldn't be well accepted by the community, and it would make the airplane lose value when it comes time to resell it.

 

[mburch]

Ok, so let's suppose that Van's doesn't change anything in the kit, and that the standard kit still requires between 2000 and 2500 hours, while the quick-build kit takes about 1500 hours.
But what if they only offer an engine mount suitable for the Rotax?
And, obviously, a cowling for it as well."

Seems like you ought to be pitching this to Lockwood, not Van's.

 

[PabloSniper]

Seems like you ought to be pitching this to Lockwood, not Van's.

I had already been following that RV-9, but I didn’t know who I should email. Thanks for the information.

 

[Mel]

Ok, so let's suppose that Van's doesn't change anything in the kit, and that the standard kit still requires between 2000 and 2500 hours, while the quick-build kit takes about 1500 hours.
But what if they only offer an engine mount suitable for the Rotax?
And, obviously, a cowling for it as well."
That wouldn't be well accepted by the community, and it would make the airplane lose value when it comes time to resell it.

Let's just say that none of this is going to happen.

If one wants to do this on an individual basis, then great, but Van's is way too busy with other things to consider a project like this.

 

[PabloSniper]

Let's just say that none of this is going to happen.

If one wants to do this on an individual basis, then great, but Van's is way too busy with other things to consider a project like this.

Well, I honestly didn’t intend to spend hours writing just to read this.
But since that’s how it is, let’s be practical.
How many of these kits do I need to have considered as sold here in Brazil for Van's to take this seriously?
And what if they launch a pre-sale, where they will only move forward if a certain number of sales is reached?

 

[Auburntsts]

My guess, hundreds per year globally minimum and that ain’t gonna happen. Sorry.

 

[Auburntsts]

What you’re proposing might have an aftermarket potential but even that’s a long shot.

 

[Ironflight]

Well, I honestly didn’t intend to spend hours writing just to read this.
But since that’s how it is, let’s be practical.
How many of these kits do I need to have considered as sold here in Brazil for Van's to take this seriously?
And what if they launch a pre-sale, where they will only move forward if a certain number of sales is reached?

In order to answer your questions, you need to talk with Van’s - not a bunch of us here on VAF…we have no idea what the production or design costs are, don’t understand Van’s current and future business model, and - like you - can just spitball stuff out here on teh internet. If your;e serious, talk to Vans and propose a business partnership - you won’t actually get anything more than opinions from here.

The Rtoax 915 (or 916) FWF package from Lockwood for the RV-9A was going to cost (ballpark) about $20K more than a Lycoming. I would;t expect anything different for an RV-4. And RV-4 with a 912? The performance would be very disappointing for most.

If you want a good example of a modern RV-4 “flying equivalent” (weight and handling), I describe the Scalewings SW-51 as the nicest-looking RV-4 in modern kit form. It is measurably slower than an RV-4 at cruise with eh 915is, but it sure does look cool! You can look up the price - it is eye-watering…

 

[PabloSniper]

In order to answer your questions, you need to talk with Van’s - not a bunch of us here on VAF…we have no idea what the production or design costs are, don’t understand Van’s current and future business model, and - like you - can just spitball stuff out here on teh internet. If your;e serious, talk to Vans and propose a business partnership - you won’t actually get anything more than opinions from here.

The Rtoax 915 (or 916) FWF package from Lockwood for the RV-9A was going to cost (ballpark) about $20K more than a Lycoming. I would;t expect anything different for an RV-4. And RV-4 with a 912? The performance would be very disappointing for most.

If you want a good example of a modern RV-4 “flying equivalent” (weight and handling), I describe the Scalewings SW-51 as the nicest-looking RV-4 in modern kit form. It is measurably slower than an RV-4 at cruise with eh 915is, but it sure does look cool! You can look up the price - it is eye-watering…

Thank you for the kind words !
But this RV-4 has already taken over my heart!
Now (since it is practically impossible for Van's to offer this) I'll focus on getting the money needed to import Robert's engine mount and cowling kit from Germany, and finding an RV-4 without an engine.
But I think the 115hp 914UL will be a more interesting option from a financial point of view.
And it still has more breathing room than the 912 at higher altitudes.





Thank you sir

 

[280FX]

From my neighbor -

Given that you are in Brazil and your version of MOSAIC is already in effect - it seems to me you should be reaching out to a local resource (Flyer) instead of trying to convince Van's (or the folks on VAF) that this is a sound idea. Personally, I don't think it is for many of the reasons already covered by others.

As Flyer has built more RV's than anyone in the world and is a quick build supplier to Van's - if Flyer think's this is a good idea, they would be able to convince Van's as well.

Email Claudio - [email protected]

I expect we would all be curious to hear his response.

 

[Auburntsts]

Just out of curiosity but are you an experienced builder? I only ask because going off plans to make even the simplest mods can add considerable cost and effort to a project and a lot of new or potential builders are completely unaware of what building really entails, even with a very mature kit like an RV that has solid factory support and the best community support out there.

 

[PabloSniper]

From my neighbor -

Given that you are in Brazil and your version of MOSAIC is already in effect - it seems to me you should be reaching out to a local resource (Flyer) instead of trying to convince Van's (or the folks on VAF) that this is a sound idea. Personally, I don't think it is for many of the reasons already covered by others.

As Flyer has built more RV's than anyone in the world and is a quick build supplier to Van's - if Flyer think's this is a good idea, they would be able to convince Van's as well.

Email Claudio - [email protected]

I expect we would all be curious to hear his response.

Just out of curiosity but are you an experienced builder? I only ask because going off plans to make even the simplest mods can add considerable cost and effort to a project and a lot of new or potential builders are completely unaware of what building really entails, even with a very mature kit like an RV that has solid factory support and the best community support out there.

Flyer is geographically far from my home.
But here in my state we have an old builder who does the same service as Flyer.

My guess, hundreds per year globally minimum and that ain’t gonna happen. Sorry.

According to this report https://www.kitplanes.com/rotax-anyone/



It would probably have an audience in Europe as well.

 

[PabloSniper]

I think I wasn't very specific in the first video I presented here, so I redid the whole work and made a new one that is in the main topic.
I hope you understand that this is not my native language, and sometimes I can be misunderstood.
After editing the video twice, I managed to find the Italian RV-4 with a Rotax 912 engine.
Which from what I read weighs 390 kilos or 860 pounds empty.
Which I found odd, since Robert's RV-4 uses a 915 and weighs 370 kilos, or 815 pounds.

 

[planenutz]

While I agree with the responses suggesting Vans is unlikely to revisit the RV-4, the overall result has some merit. It's certainly a lot more appealing than some of the alternative engine solutions that have been trialed by others, both from a practical and an aesthetic perspective.

Around the world we are facing huge costs for classic aircraft engines (new purchases, repair and overhaul) and with these traditional engines comes the additional cost of using avgas (currently $14/gal here) and, in many places, complying with noise sensitivites. While I'm happy to be running around behind my IO-360 its great to see others out there looking at alternative solutions to make flying possible. I'm not sure it would be the "least expensive" option as the price of new Rotax engines is certainly up there nowadays, but the use of mogas, the cost of maintenance and the low fuel consumption is certainly attractive.

What people in USA probably don't see is how expensive flying is becoming outside their bubble. We are now looking at an RV-12 build costing $280,000. A Sling HW build is approaching $600,000. A Tecnam 4-seater is 535,000 EURO (NZ$1m) and for a good secondhand C206 you're looking at $450,000 - for a 1978 model with 6,000 hours. If you can build a nice RV-7 for under NZ$300,000 I would be surprised. My IO-360 will cost me at least $60,000 to overhaul in current dollars - considerably more than I paid for it. A friend recently had to overhaul his O-540 after it made metal and saw no change out of $120,000. It appears USA is yet to catch up. And maybe it won't. Maybe you'll be lucky and things will continue as they are. My point is - we need people like the OP to be exploring the alternatives even if they appear unattractive to us right now. I commend his enthusiasum.

Perhaps there are a bunch of classic RV kits (RV-3,4,6) out there unfinished which might benefit from the availability of this conversion? The Rotax is not going to be the cheapest engine to buy in USA under current economic conditions but in Europe it might be a much more attractive solution than a Lycoming.

 

[PabloSniper]

While I agree with the responses suggesting Vans is unlikely to revisit the RV-4, the overall result has some merit. It's certainly a lot more appealing than some of the alternative engine solutions that have been trialed by others, both from a practical and an aesthetic perspective.

Around the world we are facing huge costs for classic aircraft engines (new purchases, repair and overhaul) and with these traditional engines comes the additional cost of using avgas (currently $14/gal here) and, in many places, complying with noise sensitivites. While I'm happy to be running around behind my IO-360 its great to see others out there looking at alternative solutions to make flying possible. I'm not sure it would be the "least expensive" option as the price of new Rotax engines is certainly up there nowadays, but the use of mogas, the cost of maintenance and the low fuel consumption is certainly attractive.

What people in USA probably don't see is how expensive flying is becoming outside their bubble. We are now looking at an RV-12 build costing $280,000. A Sling HW build is approaching $600,000. A Tecnam 4-seater is 535,000 EURO (NZ$1m) and for a good secondhand C206 you're looking at $450,000 - for a 1978 model with 6,000 hours. If you can build a nice RV-7 for under NZ$300,000 I would be surprised. My IO-360 will cost me at least $60,000 to overhaul in current dollars - considerably more than I paid for it. A friend recently had to overhaul his O-540 after it made metal and saw no change out of $120,000. It appears USA is yet to catch up. And maybe it won't. Maybe you'll be lucky and things will continue as they are. My point is - we need people like the OP to be exploring the alternatives even if they appear unattractive to us right now. I commend his enthusiasum.

Perhaps there are a bunch of classic RV kits (RV-3,4,6) out there unfinished which might benefit from the availability of this conversion? The Rotax is not going to be the cheapest engine to buy in USA under current economic conditions but in Europe it might be a much more attractive solution than a Lycoming.

Hello Planenutz!
Thank you very much for your kind words! I truly put a great deal of effort and dedication into this suggestion. It involved many hours of research and video editing.
You see, I live in a relatively poor country, but I have a deep passion for aviation. Therefore, I must find financially viable ways to pursue it.
You mentioned the price of Rotax engines, correct? Well, as you may have seen in the video, an Italian built one using the Rotax 912 UL, which has only 100 HP.
That engine is considerably more affordable. It wouldn’t necessarily require the more expensive 915 with 141 HP.
Once again, I’d like to sincerely thank you.

My Best regards,
Pablo

PS:
I almost forgot to mention.
The Chinese company Zonsen is selling Rotax copies for less than half the price.
I don't know anything about their reliability, but I know they made parts for Rotax before copying their engines.