Ryan ST replica performance data

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32fordboy

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Our Phase 1 testing was finally completed yesterday, so it felt appropriate to share the testing details. It's funny how the plane matured as a design. The initial goal was a to have a plane that was extremely light with an empty weight of less than 700 lbs, powered by the little Mikron engine. Of course, projects mature, which is definitely for the better. Obviously we'll learn more throughout the life of the design, but Brooks tested the plane so thoroughly I have no reason to extend Phase 1.

Our "copy/paste" results are below:

ST-L real-life test results. Keep in mind this is at high Colorado altitudes with only 100 hp. More power or a turbo would really wake up the machine. Some of these numbers are shown in the videos made by Brooks Mershon, so be sure to check them out.

Span: 28’ 6”
Empty weight as tested: 815 lbs
Gross weight: 1350 lbs
Fuel capacity 17.2 US gallons
Engine as tested: Rotax 912uls 100hp
Cruise speed averaged about 85 kts/98 mph
Design cruise speed up to 113kts
Maximum speed attained so far 123 kts/ 141 mph
VNE: 130 kts/150 mph
Approach speed: 60 kts
Landing speed approximately 40 kts
Takeoff and in ground effect by 45 kts.
Landings as short as 700 feet, takeoffs as short as 600 feet at a field elevation of 5,288 feet. Conditions vary significantly. See notes below.

Lowest recorded power-on stall: 25 kts indicated (likely attitude error) at about 9,000 feet with no tendency to drop a wing tip.
Maximum demonstrated crosswind: 12 kts. 8 kts maximum is recommended.
Tested to 14,000 feet
Tested to aft CG with simulated zero fuel. The plane does become more difficult to land, but it didn’t show a tendency to be dangerous.
Climb: approximately 800 fpm solo, 300 fpm dual at about 7200 feet density altitude. Again, more power or a design-specific propeller would help

Barrel rolls, wingovers, and steep turns have been tested. Loops will not be performed in the prototype airplane. Toilet paper dogfighting has been tested several times, repeatedly pulling 3.5-4G while maneuvering. General handling is docile/gentle at slow speeds and quite nimble at higher speeds.

Ground handling is good for a sharp and current tailwheel pilot who doesn’t mind the plane’s long nose. Most landings were wheel landings on asphalt, and the plane really shines doing three-point landings on grass, described as very easy with positive directional control. Kits will sit a bit lower on the main gears for a one degree change in deck angle and will likely handle better yet.

Landing distances are short for the type of plane and, depending on the airport, it can be off the runway at the first taxiway, as is done at Boulder Airport, KBDU. The tail comes down at a speed that was described as laughably slow. As with anything in life, this has its pros and cons. For pilots who prefer a faster landing speed, a clipped wing version is available.

The amount of wing clip has been determined by testing wing loadings in combination with predictions in landing speeds. Clipped wings should, from what we know at the time, increase landing speeds by about 4 kts. In addition, clipping the wings outboard of the flying wires reduces the lift-induced moment on the wings which means that, for no other change in structure, we get a higher limit load. This is opening up the potential for gentleman’s aerobatics beyond what has already been tested.

Stalls are very gentle and the plane would rather not spin. Minor incoordination in stalls has not shown to be a problem if the plane is built as straight as the prototype. Accelerated stalls had very positive control and showed no tendency to break loose when skidding during the stall. To sum it up, if the plane is built as straight as the prototype, it would really rather stay upright and not throw itself into a spin. From what we know, it would take honest effort to initiate a spin. Thus, spins were not tested.

For grins, we tested VGs on the rudder. They surprisingly had zero effect on the rudder. Now I just have to figure out how to remove them without pulling paint.

The stick-based trim system proved to be insufficient on the prototype. Therefore, kits will go back to using the Ryan-style aerodynamic tab. That is better, anyhow, as it offers redundancy.

The biggest issues with the plane were ergonomic, and these have been addressed for the kits. The rear seat will be 1” lower, giving the pilot the option to move down 2” from the current state, or upward with the slightly taller (more scale) rear windscreen. It’ll be based on pilot preference. The throttle has been moved forward. I designed and built 4 different rudder/brake pedals to get them just right. Pedals on the kits will be moved aft 1” to allow better fitment around the front occupant. The front occupant will have more aft elbow room to allow better operation of their throttle.

The cockpit remains wider than a factory ST. Thanks to Glenn Gordon’s extremely careful and deliberate cowl shaping, this is not very noticeable on the ground at all.

The forward baggage compartment has surprisingly been found useless (impractically large for the compromises that had to be made to fit it), so kits now have the rear baggage, and provisions for a belly pod, which is in the works. The benefits are more fuel, more room for gauges, more foot room, more firewall space, easier tank filling. Too many positives.
 

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32fordboy

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Ah, great question! Ours is non-sport pilot eligible. We did this so we could test gross weights as high as we wanted...in hindsight, it might have been best just to set our gross at 1320 lbs. In all other respects, it meets the Sport Pilot eligibility requirements, so if a builder sets their gross weight to 1320 lbs, they are good to go. The structure is safe all the way to 1420 lbs if the limit load is reduced to 3.8G, but we haven't yet tested it that high due to our density altitude and lack of appropriate power for that weight.

In my opinion, the ideal build for this plane would be to set the gross to 1320 lbs, then clip the wings to allow for gentleman's aerobatics.

The loops could probably be tested in this plane, but the kits have been beefed up in key locations for extra-extra margin. A loop could successfully be done within the G limits we've already tested, but there are other considerations, too, that don't have much to do with the plane itself.

We have a radial version in the works that may go clipped wing. It's up to the builder, who I am working closely with. My next personal plane may have the clipped wings, as well. If it does, we'll do further aerobatic testing.
 

Dana

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Ah, great question!
And great answers, thanks. It looks like it could be a great airplane for fun gentleman's aerobatics, like a lot of the non-Pitts sport biplanes, if the g limits are sufficient. Lou Stolp didn't design the Starduster with aerobatics in mind, but he knew people would do them so he designed it strong enough. There are so few open cockpit monoplanes in that category, and none (IMO) as pretty as a Ryan.
 

PTAirco

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I would really, really advocate spin testing. I know it's your only prototype but you seem to have ample confidence in it. You would want to know its spin characteristics before selling them to customers. Even if you then placard it " No Spins". Kind of what they did on my Maule; I'm sure it spins and recovers just fine, but they just didn't want to do the testing to save money, I'm sure.
 

PTAirco

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I'm curious: I just noticed on your website that flying wires are extra; I assume they come from those chaps in NZ? Would you offer a cheaper, but draggier cable bracing option?

Proper flying wires are a seriously expensive problem for those of us who like biplanes etc. Nobody has yet to come up with a cheaper system. Even cable bracing can be astronomical in cost if you add up the cost of turnbuckles. I'm still investigating the use of solid wire using bike spoke technology. Yes, it's still round but you could use tandem wires of smaller diameter for a little drag reduction. And have $6,000 or so to spend on Avgas.
 

32fordboy

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The flying wires are an expense, but in the grand scheme of things, the plane still comes out competetively priced when compared to completion costs of many other kits. Our wires came from Bruntons. A bit more expensive than the New Zealand type from what I understand, but rolled threads were important to me. Not sure if the NZ wires were cut or rolled, but I think they were cut at one point. You'll have to double check that. There are people in the US working hard to make rolled-thread wires. They are really close to figuring it all out and my guess is prices will eventually come down a bit. I would urge against the use of cables for various reasons. Not impossible, just something I don't see as being as practical as expected on this airframe.

Regarding spins, we do have a lot confidence in the prototype. Testing wasn't done for a few reasons, scheduling with the test pilot being one of them (he's got a lot of things going on right now). The original ST spins very well and our plane handles well enough that spins became a backburner test for later. We'll get there eventually. With the docile airfoil and identical external geometry to the original ST, we're not expecting any surprises on that front.
 

Dominic Eller

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The flying wires are an expense, but in the grand scheme of things, the plane still comes out competetively priced when compared to completion costs of many other kits. Our wires came from Bruntons. A bit more expensive than the New Zealand type from what I understand, but rolled threads were important to me. Not sure if the NZ wires were cut or rolled, but I think they were cut at one point. You'll have to double check that. There are people in the US working hard to make rolled-thread wires. They are really close to figuring it all out and my guess is prices will eventually come down a bit. I would urge against the use of cables for various reasons. Not impossible, just something I don't see as being as practical as expected on this airframe.

Regarding spins, we do have a lot confidence in the prototype. Testing wasn't done for a few reasons, scheduling with the test pilot being one of them (he's got a lot of things going on right now). The original ST spins very well and our plane handles well enough that spins became a backburner test for later. We'll get there eventually. With the docile airfoil and identical external geometry to the original ST, we're not expecting any surprises on that front.
NZ wires are rolled thread and of very high quality, Russ Ward is excellent to deal with very helpful and great service!
 

imacfii

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NZ wires are rolled thread and of very high quality, Russ Ward is excellent to deal with very helpful and great service!
Vintage Aero has always used rolled threads, as a cut thread will produce a stress riser at the shank end of the thread, and ultimately the thread will fail at this point and break the shank. A piece of steel is like a piece of wood, in that there is a grain structure running down the length of the bar, just like a wooden branch, so if you cut a thread on the shank, you have a lot of unsupported grain hanging out there. With a rolled thread, the grain is formed around the rollers, ensuring grain integrity.
In order to roll the thread, the shank must be reduced to the thread effective diameter. Some organizations reduce the thread by grinding, which may have consequences on the grain integrity and orientation. We utilize a rotary swager which compresses the shank, realigning the grain and substantially increasing the tensile strength of the shank. Next the thread is rolled up to the nominal diameter, further increasing both the toughness of the grain and also the tensile strength, so the thread is stronger than the original shank.

More info at


www.vintageaero.com

Russ Ward
 
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32fordboy

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Russ, thanks for setting things straight. It sounds like your wires are a fantastic option.

I'm going to reach out to you regarding the matter. We have a following in New Zealand and I'd like to learn more about your product.

Nick
 
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