Unlimited Aluminum Aeorbatic Aircraft

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BJC

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Any idea of what kind of altitudes we're roughly talking about?
I'm not certain what it is today, but years ago, when I last competed, the minimum altitude for Sportsman category was 1,500 feet AGL, Intermediate was 1,200 feet AGL, Advanced was 900 feet AGL and Unlimited was either 300 feet or 100 meters AGL, not sure which. The first several maneuvers in Sportsman and Intermediate, the categories where a low HP, very light airplane could compete, will likely be flown above 2,500 feet AGL.

Someone who is competing in Unlimited posted recently. Hopefully he will chime in with today's minimum altitudes.


BJC
 

Smutny

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Primary & Sportsman - 1500ft
Intermediate - 1200ft
Advanced - 656ft (200 meters)
Unlimited - 328ft (100 meters)
 

BJC

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John:

Is your avitar the purple and yellow Wolf Pitts?

Did you purchase it four or five years ago?


BJC
 

BJC

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I lusted after that airplane, talked to Steve about it in detail, but in the end, accepting that I would not return to competition, I went with an S-1E.

Beautiful airplane when I last saw it, some years ago at the Arlington flyin. Kathy keeps hers three houses /hangars down from me.


BJC
 

Smutny

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I understand, fell in love the second I saw it in the magazine, and then again in person later that year in Ephrata. I feel very lucky to be the current caretaker of the Wolf Pitts.
 
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autoreply

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Any idea of what kind of altitudes we're roughly talking about?

The Extra 300 is roughly 1500 lbs empty, so say 1800 loaded, bare minimums fuel with 315 hp.
With 100 hp, you'd be at 570 lbs, or about 300 lbs empty. If we assume* 400 lbs empty is possible, power/weight is about 15% lower (or you'd need 17% more power). Sounds like with a light ULpower (130-ish hp) it is possible to match power/weight of an unlimited, but with 100 hp it's impossible.

*To avoid a discussion. For an optimal composite, FG aerobatic ship, I think that's about the lowest realistic weight you can achieve with a 912S and a variable pitch prop, but obviously opinions might disagree.

It never occurred to me till now that aerobatic ships don't necessarily have to be such big powerful airframes. You'd think more people would have thought/designed/built in this direction, given the popularity of the Pitts.
fghfghg
 

Smutny

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It goes beyond just engine horsepower though. The real component forward of the firewall that makes aerobatics possible is the propeller. The current top choices of the MTV-9/203, 400AC and Claw that provide fantastic thrust for some great control at lower speeds, can't be put on smaller engines. Even a hopped up IO-360 doesn't have enough oompf for these three.

There's no replacement for displacement...

That being said, there is definitely a market segment open for a 100hp, all metal aerobat. But comparing it to Extra's, Edge's, MX's and Xtreme's is going to leave your potential customers unsatisfied. You just won't won't be able to do that style of aerobatics without the thrust and power they have.
 

autoreply

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It goes beyond just engine horsepower though. The real component forward of the firewall that makes aerobatics possible is the propeller. The current top choices of the MTV-9/203, 400AC and Claw that provide fantastic thrust for some great control at lower speeds, can't be put on smaller engines. Even a hopped up IO-360 doesn't have enough oompf for these three.
True, though for the Rotax there's also good props with more static trust per HP than the 540/550/580.
There's no replacement for displacement...

That being said, there is definitely a market segment open for a 100hp, all metal aerobat. But comparing it to Extra's, Edge's, MX's and Xtreme's is going to leave your potential customers unsatisfied. You just won't won't be able to do that style of aerobatics without the thrust and power they have.
Power is pretty much irrelevant. It's power/weight ratio or trust/weight ratio.

In post 40, I established that 100 hp is indeed impossible, but in the low 100-ish hp range, it might be competitive. Given the lower disk loading (power/prop disk area), somewhere in the 120-140 hp range might very well be superior to the unlimiteds if you can pull off a very light aiframe and can get the visiblity/size issues resolved.
It's official... Autoreply has finally lost all of his marbles. :gig:
Just fighting the forum software, sorry for the trouble ;)
 
S

Sasho

There is one Italian attempt for 100 HP Rotax powered aerobatic airplane called Dallair FR-01. It features steel tube fuselage with sheet metal wings and empennage. It was shown at Oshkosh '11 or '12 in front of the IAC pavilion. It doesn't seem capable of inverted flight though.
 

jbourke

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The Extra 300 is roughly 1500 lbs empty, so say 1800 loaded, bare minimums fuel with 315 hp.
Not trying to split hairs here but just to make sure the details are clear, the Extra 300 is not an unlimited class airplane and also has 300hp. It is often flown in Advanced but only rarely seen in unlimited and it is completely outclassed. It is also a two seat airplane, so it is heavier than most.

My Extra 330LX is lighter than the 300 and rolls much faster. It weighs somewhere just over 1400 lbs. It is two seat also, but capable of unlimited. It would not do well enough in international competition but is acceptable for regional unlimited competition.

The Extra 330SC is the top of the line single seat unlimited class aircraft today. They typically come in at around 1300 lbs. It is common to pump up the engines on these planes which puts them at 350hp or more.

So your target power:weight ratio is a bit higher than it might have seemed at first, but that depends on whether you are looking for something to fly at the very highest levels. There is more to it than power:weight because presentation is also extremely important.

With 100 hp, you'd be at 570 lbs, or about 300 lbs empty. If we assume* 400 lbs empty is possible, power/weight is about 15% lower (or you'd need 17% more power). Sounds like with a light ULpower (130-ish hp) it is possible to match power/weight of an unlimited, but with 100 hp it's impossible.
I'm interested in a deeper breakdown of the weights if you have time for it. Maybe a new thread.

Jim
 

Davevon

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You might find this airplane and concept interesting :)

ACRO - Acro Advanced

I've tried to get plans with out any success.

I think the 100 hp unlimited capable airplane is possible, but it's going to take a paragrim shift in construction and what the airplane will look like. Think of where F3P is now. http://youtu.be/bX_4SrDZBvQ

Remember I said capable not competitive, big difference. Not that it's not possible to also be competitive, but the flying style would be so different it'll need acceptance from the judges.

Dave
 

BJC

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That ACRO evolution of the Tipsy Nipper is interesting, but I did not find a specs page. Did I miss it?

Thanks,


BJC
 

jbourke

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It seems like it is a pretty common complaint that competing in Unlimited is too expensive.

Yet there are many inexpensive aircraft already available that can fly the Unlimited sequences. The Pitts S1S does all the figures. It has won before and it can still win.

Jim
 

Davevon

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Here's some limited info.

ACRO- Aerobatics

With the lighter airframes flying slower there'll be a lot less inertia. Vertical penetration will be more dependent on thrust. Larger diameter props driven through a reduction drive will be necessary. That will allow the smaller engines to develop more hp at a higher rpm too.

Dave
 

Davevon

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It seems like it is a pretty common complaint that competing in Unlimited is too expensive.

Yet there are many inexpensive aircraft already available that can fly the Unlimited sequences. The Pitts S1S does all the figures. It has won before and it can still win.

Jim
Yup. Robert Armstrong flew a S-1C, aka: Road Kill, in the Worlds not too long ago. He used trim tape to simulate ailerons on the top wing :)

Dave
 

TFF

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Planes like the S1S can do all the maneuvers, but they cant do all of them linked in a sequence. Given equal pilot skill, Pitts might have to break off at the Advanced sequence under many circumstances vs a Monoplane. The biplanes just have too much drag where the monoplanes have the impression of having 100hp more than a biplane. Anyone flying a Pitts in Unlimited is a hero today. Also Pitts or Biplanes in general dont score well because the judges dont like how they look; they want the straight lines of a monoplane. Americans had to give up on Pitts, not because they wanted to, but judging bias that happens in world comps. With good competition, if a Pitts places well is because they guy or gal is flying their donkey rear off. If you are just flying local contests, a well flown Pitts or lower cost plane can be on top, but when you are really pushing to be on top, you better have a 300hp monoplane that weighs 1400 lbs.
 

Smutny

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I've been attending IAC competitions since 1997. During that time there have been a myriad of low cost, low power aircraft available on the market to whoever wanted them. Everything from the Cessna Aerobat, RANS S-9 & -10, Sonex, RV-3's, Stits, etc., etc.. In those 18 years I've seen only two Cessna Aerobats and one Sonex in the box. Whether it be the folks who own them don't feel they are up to perceived competition standards, or that competition is not their cup of tea, who knows. Fact of the matter is that the airframes exist, but don't show up.

Every few years there's the call for an affordable, top tier aerobatic airplane. But we're not a culture of builders anymore, the vast majority gravitate to factory Pitts, Extra, Yak and Sukhoi for their mounts in Advanced and Unlimited. I've only seen one Zenith, the Eigenhawk (a one off), Laser, and various Pitts S-1's as homebuilts in the top two levels.

Presentation through size and horsepower is the determining factor. And while I honestly feel a 100-130hp acro mount will never be competitive in Unlimited, I do hope people keep trying, even though the market is miniscule.
 
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jbourke

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TFF,

Yes, flying a Pitts in Unlimited is a challenge, possibly involving some penalties for breaks or outs, but for the budget minded it is an option.

There are a lot of other barriers to flying Unlimited besides money. It's simply not for everyone.

In Advanced the Pitts does great. You are flying low enough that the judges can see you even if your plane is a bit smallish. Sure it takes the right hands to make it work but the monoplanes don't fly themselves either.

Jim
 
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