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Old 03-21-2023, 11:04 PM
Lithosis Lithosis is offline
Join Date: Apr 2021
Location: Meridian, ID
Posts: 8

Originally Posted by gmcjetpilot View Post
Personally I would stay clear of UL Power. I know about the UL520. Not failure with turbo charged version UL520T except for what is on their web page I can say the effective HP or thrust from their engines in not as advertised. It is a complaint of many. They get their claimed HP at 3200 RPM. It is direct drive and that is too much RPM for Prop efficiency. The special prop they use can only do so much. Also it burns as much or more fuel as a Lyc, on HP to Gallon basis.

What is Van's RV-15 engine: "Lycoming IO-390 four-stroke powerplant, driving a 80-inch Hartzell Propeller Trailblazer three-blade, constant-speed propeller. The Lycoming O-360 will be an option." Stick with that, unless you want to make your own engine mount and custom intake, exhaust. deal with a 100 custom design and system installation design and fabrication. More build time for sure.

The UL Power advertised power is optimistic with rated HP by a good bit. I know of an RV7 with UL520 engine. The custom engine mount, CG issues. slower speeds (more like a 160HP) while burning same GPH. Not impressive. In 2019 prices a Lycoming was $10,000 less than UL Power. Now they are about the same. Stick with what Van suggests and has designed the plane for.

Prop on UL is either fixed or a very expensive AIRMASTER electric prop ($15,000) made om Australia. Have a problem good luck. UL power it also made far away in Europe. Give me a Lyc and Hartzell Hydraulic Prop.

Early models of the UL520 had piston and cylinder issues. There is Facebook group for UL Power. There are some pictures of broke internal parts. They sold engines with CAST pistons. They failed. I believe they are using forged pistons now.

If it's ain't Lycoming I ain't going. 3 years ago Lyc prices were $25K to $36K new the UL520 was $38,000 rated at 200HP but really makes 180HP or less. The UL530T I guess is $48,000. Why? More time and Work to build deviating from plans, lower performance and more cost. Why?

The horsepower is rated differently on the turbo version: “220 hp @ 2700 rpm up to 15000 ft“. Fuel burn should be very comparable to 390. Don’t remember if I had found a testimonial or if I'm just using their numbers. (Website claims 8-11 gal/hr in cruise)

I was told by the US distributor that they work with someone who would have an engine mount and cowling for the engine. There will definitely be more work though. That's why I'm hoping it’s supported by Vans.

The 390 thunderbolt is over $62k today. Non-thunderbolt 390 will run you $58k, while the 520T is still in the $48k range. It is not a fair comparison to look at pricing a couple years ago, or to use a 360.

What’s a constant speed prop cost? I thought they were in the 12k+ range anyway. Looks like the Hartzell's are $10k. It is a better system and the electric prop is one of the primary downsides of going with the 520T in my opinion. But the electric is priced that way as a 4 bladed prop which probably contributes to cost. Won't the 15 look awesome with 4 blades on the front!?

The added weight of the turbo really helps bring in the CG. If they design for the lighter 360 there's only a marginal difference in weight to make up. I would consider a ground adjustable prop if I didn't want the extra weight on the nose though.

I think most of the points you make are just a little dated and you don’t give it any credit for the improved performance up high, FADEC, and single lever control. Another big piece of info we’re missing is what the Vne will be on this airframe. Then we’ll know if we can take advantage of that turbo up high to help a slower plane kill it cross country.

These are the opinions I want to hear though so thank you. There’s certainly a lot to consider.

Last edited by Lithosis : 03-22-2023 at 08:48 AM. Reason: I wrote this on my phone late last night. Wanted to better formulate my thoughts.
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Old 03-22-2023, 09:19 AM
gmcjetpilot's Avatar
gmcjetpilot gmcjetpilot is offline
Join Date: Jan 2005
Posts: 4,944

Originally Posted by Lithosis View Post
The horsepower is rated differently on the turbo “220 hp @ 2700 rpm up to 15000 ft“ from their website. The 390 thunderbolt is over $60k today, while the 520T is still in the 48k range. I forget my source but fuel burn should be very comparable to 390. Don’t remember if that was a testimonial or using their numbers. What’s a constant speed prop cost? I thought they were in the 12k+ range anyway. It will be a more difficult install, unless it’s supported by vans which is certainly my hope. The added weight of the turbo really helps bring in the CG. I think most of the points you make are just a little dated and you don’t give it any credit for the improved performance up high. These are the opinions I want to hear though so thank you. Another big piece of info we’re missing is what the Vne will be on this airframe. Then we’ll know if we can take advantage of that turbo up high to help a slower plane kill it cross country. There’s certainly a lot to consider.
That is good to know. I would reserve judgement on any engine until it has flow for 100's of hours or better 1000's of hours. I also would not buy an engine until I talked to person that flies it with real flight test data collected. Better still fly the plane with that engine. I don't mean someone who bought it and has it in a crate on their hanger floor or hanging on their project yet to fly.

You are right the Vne might be an issue, but in a utilitarian plane like the RV15 the turbo would be for high hot altitude operations in mountain airstrips. Most turbos on small piston aircraft have typically been for normalizing, to maintain SL power to higher altitudes, as well as pressurize the cabin. In the case of the UL520T they must have the boost turned up as it is only 320 cu-in. and advertised as you say 220HP at 2700 RPM. The little engines like Rotax get power by running at 5500 RPM and using PSRU. So we shall see. I know there are some flying I think but don't hear much?

As far as prices you I heard $12,000 a while back so I said $15,000 to account for inflation and shipping. If the prop is $12,000 great. Exotic composite props, electrical I am sure are expensive. MT props are even more. However when they don't widely publish prices you have to guess. You have to factor in shipping and handling from Australia.

I totally appreciate flying with Turbos high up. Flew a Ted Smith Aerostar later became Piper Aerostar twin with turbocharged Lyc 540's. It was certified to FL250. Yes it is great to fly high, sucking O2 all day not so much. RV15 or any plane that operates in and out of high altitude mountain strips at max weight would benefit from Turbo. However you can put a Turbo on Lycoming's or Continental's and they did on certified planes. Ray Jay use to sell kits to add them to Certified planes. I flew turbo charged planes but never owned one nor would I ever. Besides the Aerostar I flew for a Company, the flight school I taught at had a few Turbo planes, one being a Cessna P210... The plane was in the shop every 50 hours, intercoolers, turbo it was complicated. Love the performance but would hate to pay for the maintenance.

UL520T is about 320 cubic inches. I assume it is not aerobatic and there is still no hydraulic prop control. If they can squeeze 220HP out of 320 at 2700, that would be great if reliable, light and not too much money. However watching the latest greatest THING in EAA world my advice is wait until you see them fly, they have 100's if not 1000's of hours with proven real world performance. Ideally the plane you are building is made for the engine so you don't have to invent the installation. At this time we don't have that. In 10 years who knows if they will be in business or dominating the market. The later I personally doubt.

I know of one RV with UL520 and it cruises slower and has similar fuel burn as a Lycoming powered RV. I don't have detailed info. There is no free lunch. People equate Lyc with not modern, but they are powerful for weight. Yes there are lighter engines but the Lyc is built stout. Lyc can achieve very high fuel efficiency in cruise properly leaned. Before 2020 they were a bargain. I still think today even though the prices are shocking they are a good value. We had it really good when you could buy a new O360 for $19,000, then it was $25,000. Now they are $39,000 or more. However that is cheaper than a UL520T I believe. Again prices are not widely advertised.

Van's recommendation is Lycoming. The design, the testing, and kit will be tailored to the Lycoming. I am 100% opinionated, stick to the plans. That is not to say people have not tried alternative engines before and will keep on trying them in the future. Go do it. Let us know how it went. My opinion is alternative engines can be OK, but never better and more often not so great. Alternatives always take more time and fiddling to get built and flying.

The failures I mentioned are dated but not that long ago. As I said they improved the design. Many boutique engine companies like Jabiru are on Gen4. I understand Gen4 is pretty good. It is one of only 3 engines approved for S-LSA's along with Rotax and Continental O-200. The UL is not listed as an approved S-LSA engine at this time. Not S-LSA's are not type cert by FAA. The oversight is by an industry standard and groups like ASTM International, and others.

Lycoming is known, has service and parts widely in USA and world wide. As far as wiz bang "Modern" EFI and EI, you can have that with a Lyc. or go with a Carb or Mechanical FI and Mags for 100% electrical independence. The value of the Lycoming was clear until inflation. However the Lycoming I think is still a better value and way less risk.

A Lyc powered RV will have higher resale than a UL powered one. By the time you buy, ship the UL, make all the custom changes and engine mount to fit it to your RV, the price is likely the same or more, especially in build time and working out kinks. Put a Lyc in go fly.

Red Bull Air race, Reno Sport Class, every plane has Lycoming or Continental (except the Thunder Mustang with Falcon V12). If you want to ring out a Continental or Lycoming with Turbos or HC pistons or NOX for racing that can be done. I just don't see an advantage of going UL. the Lyc 320-340-360-370-390 are hard to beat. I like the lower compression 8.5:1 or less Lycs. I don't need the extra HP. I would rather have fuel flexibility.
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Last edited by gmcjetpilot : 03-22-2023 at 09:29 AM.
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