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RV-12 -- Is it too soon to start the nagging?

jonbakerok

jonbakerok

Well Known Member
Just sold my 6A. Wasn't sure what I wanted to build next, but now I'm thinking LSA.

After looking at all the other options, here I am right back here at Vans. But doggoneit, my next plane will be a taildragger, and I don't give a rat's *** how unpractical it is! I had practical. Now I just want cheap and fun.

By the way, that flip-up canopy's gotta go, too. In fact, how about giving us a removable slider, for open-cockpit fun?

And how about a Jabiru instead of that Rotax? Not geared, more power, same all-up weight, 2000 hr TBO, and no water cooling system to mess around with. Why would anyone choose a Rotax?

And 118 mph cruise? Gimme a break! The LSA def allows 138 mph top speed at sea level. If 138 is top, I want at least 130 at 75% -- for a 150 TAS at 8500. The Zodiac claims 160 TAS at 8500 with the Jabiru. Why not Vans?

If fact, I would have already ordered the Zodiac if not for the unbalanced ailerons and non-removable wings. From what I hear, the control harmony on the Zodiac is awful, and after flying that sweet 6A for four years, I couldn't put up with that.
 
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Jon, Be very skeptical of Zenair's speed claims. I've built one. They originally claimed 140 mph out of the CH601HDS. We finally got a solid 105 kts. after several speed mods.
They are nice airplanes, but they have a tendency to exaggerate.
I can almost guarantee you that Van will NOT offer a tail wheel or canopy option on the -12. It is designed for a specific market.
BTW, I've done a lot of research deciding on the engine for my bi-plane. The Jabiru 3300,whick I am using, is about 50 lbs. heavier than the Rotax. The 4 cylinder Jabiru is only 85 hp.
 
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jonbakerok said:
And how about a Jabiru instead of that Rotax? Not geared, more power, same all-up weight, 2000 hr TBO, and no water cooling system to mess around with. Why would anyone choose a Rotax?
Click to expand...

The Rotax 912 run on auto fuel easily achieves its TBO in most cases if operated by the book (flog it and change the oil) and in fact some are going to 4000 hours BO. That is not a misprint. Jabiru has only just finished fixing several major problems with their original design, many of which were toast before even 500 hours. From what I've seen, they appear to have most things licked now but few if any have demonstrated 2000 hours of flight time to my knowledge. Someone correct me if I'm wrong here.

There are 20+ times more 912s flying with a good dealer/ repair network in place. Van would have chosen the Jab from the start if he thought it was better. I'm sure he carefully reviewed all possible engine options.
 
jonbakerok said:
Just sold my 6A. Wasn't sure what I wanted to build next, but now I'm thinking LSA.

And how about a Jabiru instead of that Rotax? Not geared, more power, same all-up weight, 2000 hr TBO, and no water cooling system to mess around with. Why would anyone choose a Rotax?

And 118 mph cruise? Gimme a break! The LSA def allows 138 mph top speed at sea level. If 138 is top, I want at least 130 at 75% -- for a 150 TAS at 8500. The Zodiac claims 160 TAS at 8500 with the Jabiru. Why not Vans?
Click to expand...
From VAN'S website:

Cruise Speed (75% power @8,000?) 118 kts.
Climb rate: 1320 lbs. gross wt. 750 fpm
Climb rate: (solo, 1000 lbs) 1100 fpm
Stall speed: @ 1320 lbs. 50 kts
Click to expand...


That's 118 KTS. - NOT MPH. And that is without wheelpants.

Posted elsewhere, Jabiru reportedly plans to offer a FWF kit for the RV-12, assuming using their 3300. I like the idea of the Jab power too. But it sounds like VAN'S is providing a pretty complete kit/instructions - possibly even including panel. So, for ease of build, shorter build time and economy, I may not deviate from their offering. I'll have to see.

The biggest plus for me that they could announce now is that it is OK to do loops and rolls. :D

Don't lose sleep yet. The final version isn't out yet. There'll be a whole new set of numbers.

DJ
 
ONE of the reasons Van chose the Rotax over the Jabiru is availability. It's difficult to get Jabirus.
 
jonbakerok said:
And how about a Jabiru instead of that Rotax? Not geared, more power, same all-up weight, 2000 hr TBO, and no water cooling system to mess around with. Why would anyone choose a Rotax?
Click to expand...
The J3300 is an interesting engine in theory. However, it is not widely available, no FWF from Van's (at this time), and reliability is a question - not saying that it's poor, it's just not as proven as the Rotax.

The Rotax is here, proven, and well known (problems and all). Reading between the lines, Van's wanted a reliable, well understood engine that met the requirements for the -12.

Personally, I'd love to see the J3300 catch on - it's simpler than the Rotax and could be a lot easier to feed and care for. However, it's been said before that with the large gap between MCP and max takeoff power, the J3300 really needs a CS / adjustable pitch prop to make use of the power. I enjoyed flying the 3300.

TODR
 
WHAT?

the_other_dougreeves said:
However, it's been said before that with the large gap between MCP and max takeoff power, the J3300 really needs a CS / adjustable pitch prop to make use of the power. I enjoyed flying the 3300.

TODR
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I don't understand this at all. Just look at the flat torque curve. This is one of the reasons that it flies circles around the Continental in the Legend Cub. It's also the main reason I'm using it in my bi-plane. All the way down to 2800 rpm, it still develops 100 hp. It works GREAT with fixed pitch.
 
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Jab max continuous rpm

Mel said:
The "max continuous power" is a paperwork limit to make it acceptable for LSA.
Click to expand...

Not exactly. The max continuous rpm of 2750 was first published in 1998 when the 3300 went into production. That was long before anybody had a clue as to what the LSA rules would be. When hydraulic lifters were added to the engine starting with sn 961 the limit was increased to 3150 continuous. Configurations that met the rule with the old engine would be hard pressed to do it with the new one.

Engine manuals are available here:

http://www.suncoastjabiru.com/downloads.htm

Tony
 
jonbakerok said:
.

After looking at all the other options, here I am right back here at Vans. But doggoneit, my next plane will be a taildragger, and I don't give a rat's *** how unpractical it is! I had practical. Now I just want cheap and fun.

By the way, that flip-up canopy's gotta go, too. In fact, how about giving us a removable slider, for open-cockpit fun?
QUOTE]

If you have to have a taildragger, you could always look at one of these:

http://www.kitfoxaircraft.com/
http://www.rans.com/ranshome.htm

They both can be built as a taildragger. From the way it sounds, Van's isn't interested in making the -12 a TD or slider :eek:
Click to expand...
 
rv-12

how about the O-200 ? reliability, easy maintenance, excellent availability, proven track record, 2000 tbo, made in USA !!!. yes, a sliding/removable canopy and tail wheel configuration option is needed. if van's doesn't figure this out there will be alot of builders making these mods and a large resale market for factory new rotex 912's . that will harm the great reputation that vans has enjoyed. what's with these marketing guys ? do they have a clue ? have they left the universe ? he has a plane that can wax the zodiac 601xl (tail dragger/O-200) and the rans s-19 if he pays attention to his following.
frustrated ? d*** right. bernie
 
Biggest problem with the O-200 for LSA is weight. It weighs considerably more than the Rotax.
 
Mel said:
Jon, Be very skeptical of Zenair's speed claims. I've built one. They originally claimed 140 mph out of the CH601HDS. We finally got a solid 105 kts. after several speed mods.
They are nice airplanes, but they have a tendency to exaggerate.
.
Click to expand...

Mel I think you are the master of the understatement...:)

I believe zenair claimed 140mph Cruise on just 80Hp...My out of the box 601HDS made about 90kts on 5GPH

I think they way over exagerated and I got sold a pup...Nice flying airplane (even spins better than the RV 7a) but I was very dissappointed in Zenair's creative marketing.

Frank 7a
 
They said the same about the -9

Mike_ExpressCT said:
From the way it sounds, Van's isn't interested in making the -12 a TD or slider :eek:
Click to expand...
They said the same about the -9. Let the whining begin!

Phyrcooler said:
From VAN'S website:
That's 118 KTS. - NOT MPH. And that is without wheelpants.
DJ
Click to expand...

Oops, shot off my mouth without reading the fine print! Since when does Vans post performance numbers in knots? That's still only 135 mph. Not good enough! But I'll hold my tongue 'til we see the numbers with wheel pants.

As far as all the stuff about Jabiru... I gotta admit, both Rotax and Jabiru are foreign animals to me. But the Jabiru sure looks better on paper. If Vans picked it, the availability would improve. By the way, I read in a magazine once that a Rotax comes with a disclaimer that warns you from installing your airplane engine in an airplane! I wonder if that's really true. I'd just about reject that deal on principal.

I've also heard that Zenith exaggerates their performance numbers. Their web site says they'll prove the numbers with a test flight, and I'm tempted to take them up on that. I'd like to see how bad that control harmony problem is, anyway. Why the heck did they balance the elevators but not the ailerons? Weird.
 
jonbakerok said:
I've also heard that Zenith exaggerates their performance numbers. Their web site says they'll prove the numbers with a test flight, and I'm tempted to take them up on that.
Click to expand...
Yeah, they proved it to me, with indicated airspeed. Later discovered that they had the "static" open to the cockpit. When I asked the demo pilots what they flight plan block to block, they said 100 mph.
This was back in the mid '90s. Maybe they have gotten their act together by now.
 
jonbakerok said:
I'd like to see how bad that control harmony problem is, anyway. Why the heck did they balance the elevators but not the ailerons? Weird.
Click to expand...

Maybe I'm off base here....

But I assume that Van's "frize" ailerons have the weight up front because of the pivot point, as well as forming the leading edge. As I remember, the aileron balancing comes from each aileron balancing the other.

However, I have no idea what type of ailerons the Van's RV12 uses. But I just wanted to put forth the idea of each aileron balancing the other.

L.Adamson
 
jonbakerok said:
Why the heck did they balance the elevators but not the ailerons? Weird.
Click to expand...
Which airplane are we talking about? I've never seen a Zodiac with balanced elevators, and I've inspected quite a few.
 
Mel said:
This was back in the mid '90s. Maybe they have gotten their act together by now.
Click to expand...

I test flew an RV-6 and the Zodiac XL (new version, not the same plane as the HD) about a year ago while doing pre-purchase evaluations.

It wouldn't be right for me to judge the quality of all RV's by the quality of the single RV-6 that I flew (it was a rattle trap and I was happy to get back on the ground).

To be fair, I'm sure not all Zodiacs are as nice as the one I flew either. I've never flown the older HD so I can't speak to that design.

IMHO, the RV-12 would be a more viable candidate for more people if there were some flexibility in engine choice. As it stands today, all it has to offer over the Zodiacs and S-19's is brand loyalty by an existing customer base (which is almost certainly enough to make it successful).

- PatrickW
 
jonbakerok said:
They said the same about the -9. Let the whining begin!



Oops, shot off my mouth without reading the fine print! Since when does Vans post performance numbers in knots? That's still only 135 mph. Not good enough! But I'll hold my tongue 'til we see the numbers with wheel pants.

As far as all the stuff about Jabiru... I gotta admit, both Rotax and Jabiru are foreign animals to me. But the Jabiru sure looks better on paper. If Vans picked it, the availability would improve. By the way, I read in a magazine once that a Rotax comes with a disclaimer that warns you from installing your airplane engine in an airplane! I wonder if that's really true. I'd just about reject that deal on principal.

I've also heard that Zenith exaggerates their performance numbers. Their web site says they'll prove the numbers with a test flight, and I'm tempted to take them up on that. I'd like to see how bad that control harmony problem is, anyway. Why the heck did they balance the elevators but not the ailerons? Weird.
Click to expand...
Jon,

Maybe, just maybe Van's needs to be cut some slack.

The plane is not even OUT yet, so in my opinion, yes it is too soon to be whining.

A few more points ...
I think they are really trying adhere **properly** to the specifications for LSA .. not a wink, wink, nod .. but the real deal.

One of the reasons for the delay, as I recall (1-2 knots off on stall speed). Some may have just winked at that but not Van.

There is a speed limit as we all know for LSA.

I think I heard "someone" from Van's say that the Jabairus were either too little or too much on the HP that the design needed. That along with the other points made provide good reason to go with the Rotax. Some could make the argument that the RV7's, 8's and 9's should be Continental powered. I for one am glad that he picked an engine that matched the design and "made it work for us".

Of course, anyone can put any engine, cowl, wheel they choose on their experimental. But even though I am not in the market for an RV12 (this week), I for one hope that Van keeps the focus on delivering a plane with all known working parts. AFTER that is "successfully done" then go looking into other potential options IF there is real demand. Also if there really is a lot of demand and Van's does not do it, then of course, Jabairu can.

Just another viewpoint.

James


James
 
jonbakerok said:
They said the same about the -9. Let the whining begin!
Click to expand...

Not from me! If I had the choice, I would build the -12 just the way Van is. Tip up for better visibility and nose gear so I can relax a little easier when I turn final :D
 
Mel said:
I don't understand this at all. Just look at the flat torque curve. This is one of the reasons that it flies circles around the Continental in the Legend Cub. It's also the main reason I'm using it in my bi-plane. All the way down to 2800 rpm, it still develops 100 hp. It works GREAT with fixed pitch.
Click to expand...
Let me see if I can explain -

In order to get good speed, you'll need to pitch the prop so you get near 2750 (MCP) at WOT and level flight. So, in climb, you're getting less RPM, meaning less power. Right?

So, this essentially makes the J3300 a 105 Hp engine. This doesn't make it a bad engine, just that 15 Hp (~12%) are essentially unavailable without a CS prop. This isn't really any different from any other engine, but the spread seems to be a bit wide, e.g., the 912S is 95Hp @ 5500 MCP and 100Hp at 5800 max TO power (5 min).

TODR
 
The more I learn..

Mel said:
Which airplane are we talking about? I've never seen a Zodiac with balanced elevators, and I've inspected quite a few.
Click to expand...

Zodiac 601 XL. I thought I read it in a flight report somewhere. In fact I've read several places that it's very touchy in pitch and very heavy in roll. If it's not due to over-balanced elevators and unbalanced ailerons, what causes it? And how bad is it? Man, this basic plane has been in production for almost 20 years. You'd think they'd have worked the bugs out by now.

I've also recently discovered that the Zodiac uses cables instead of push tubes, and not only that, it uses nylon bumpers instead of pulleys. Good grief!
 
Two markets

All this just proves my original point. Nobody's going to build the LSA we want unless we ask for it. And none of the vendors seem capable of understanding this market. So let me just make it real simple.

There are two LSA markets:

1) Existing pilots who don't want to mess around with medicals and can't afford to blow $100 on every flight (or $300/month on hangar rent). In other words, me.


Here's what I'm looking for:

-- Fast: The absolute limit of what LSA allows -- 150 mph TAS.
-- Fun: Taildragger, open cockpit if I want it, loops and rolls
-- Cheap: Less than 5 gph mogas in cruise. Trailerable so I can keep it at home.
-- Practical: At least 450 pounds payload.
-- Safe: 6g, 9:1 glide, simple reliable engine, no fuel in the cockpit, pushtube controls
​

2) The other LSA market is for trainers. Great opportunity for Cessna, and no point in offering a taildragger. But kitplanes aren't trainers!


Van -- your LSA market is some small fraction of the barely 700,000 existing pilots. In fact I'm your market -- a previous RV builder who is looking for some way to continue flying in his retirement.

Please do not confuse me with someone who wants to build a trainer!
 
jonbakerok said:
Two LSA markets:

1) Existing pilots
-- Fast: The absolute limit of what LSA allows -- 150 mph TAS.
2) The other LSA market is for trainers.

Please do not confuse me with someone who wants to build a trainer!
Click to expand...
Perfect description. I am in absolute agreement, and dumbfounded that nobody, excepting perhaps Van's Aircraft, is addressing market #1.

Chase Snodgrass
Presidio, TX
http://flybigbend.com
 
Corvair power?

I may off base but would it be possible to mount a Corvair engine on the front of the RV-12? They are suppose to make about 100 hp and I like the idea of the 6 cylinder. If so then maybe I could make a trip to Edgewater and persuade William to come up with a mount and cowl.

Just thinking,
 
jonbakerok said:
...Trailerable so I can keep it at home.
-- Practical: At least 450 pounds payload.
-- Safe: 6g, 9:1 glide, simple reliable engine, no fuel in the cockpit, ...
Click to expand...
The dual requirements of trailerable and no fuel in the cockpit illustrate the tradeoffs of aircraft design. Meeting both these requirements is very tough. Fuel line disconnects? Venting. Then there is the weight of the fuel that has to be dealt with when you are removing the wings.
 
jonbakerok said:
Zodiac 601 XL. I thought I read it in a flight report somewhere. In fact I've read several places that it's very touchy in pitch and very heavy in roll. If it's not due to over-balanced elevators and unbalanced ailerons, what causes it? And how bad is it?
Click to expand...

I flew a Zodiac XL with the original style ailerons (the ones that are part of the upper wing skin). The stick forces for the aileron while sitting on the ground are quite high. Sense you have to flex the upper skin it acts like a return spring. The elevator is another thing. It has very light forces. Needless to say I was quite shocked when I flew this plane. There was not balance between pitch and roll. I'm sure you could get use to it, but it made me really appreciate my RV9 and it's wonderful control balance.
 
Fearless said:
I may off base but would it be possible to mount a Corvair engine on the front of the RV-12? They are suppose to make about 100 hp and I like the idea of the 6 cylinder. If so then maybe I could make a trip to Edgewater and persuade William to come up with a mount and cowl.

Just thinking,
Click to expand...

Corvair is way too heavy again and not sure the reliability is there with some crank failures in the direct drive mode. I don't believe the 100hp claims at 3000 or so rpm, having built and worked on these engines many years ago.
 
jonbakerok said:
All this just proves my original point. Nobody's going to build the LSA we want unless we ask for it. And none of the vendors seem capable of understanding this market. So let me just make it real simple.

There are two LSA markets:

1) Existing pilots who don't want to mess around with medicals and can't afford to blow $100 on every flight (or $300/month on hangar rent). In other words, me.



Here's what I'm looking for:
-- Fast: The absolute limit of what LSA allows -- 150 mph TAS.
-- Fun: Taildragger, open cockpit if I want it, loops and rolls
-- Cheap: Less than 5 gph mogas in cruise. Trailerable so I can keep it at home.
-- Practical: At least 450 pounds payload.
-- Safe: 6g, 9:1 glide, simple reliable engine, no fuel in the cockpit, pushtube controls


2) The other LSA market is for trainers. Great opportunity for Cessna, and no point in offering a taildragger. But kitplanes aren't trainers!

Van -- your LSA market is some small fraction of the barely 700,000 existing pilots. In fact I'm your market -- a previous RV builder who is looking for some way to continue flying in his retirement.
​
Please do not confuse me with someone who wants to build a trainer!
Click to expand...
I agree with many of your points. I am one of what I think are many pilots who are looking at the LSA as a low cost entry point, that is quick to build. I have a no problems with a medical, and have a full PPL. So - low cost. Cheap to fly. Fun - (would really like to do loops and rolls). Practical/safe... I agree with all those points.

However, I have to say that too many folks are overly worried about the fuel tank location on the RV-12. Almost every wreck I have seen (either first hand, or in training documentation) that is survived has a relatively intact cockpit area. The FWF area, landing gear and wings absorb the impact. The tank in the baggage area of the fuselage is probably the most secure location it could be in. Fuel in the wings gives you a greater chance of a large amount of atomized/spraying fuel when a wing is impacted or ripped off. The trade-offs for the RV-12 are in baggage compartment space and C of G issues. I would not make this a make or break checklist item when choosing an aircraft. Don't overestimate the safety of fuel in the wings.

The second issue I don't agree is the "Taildragger issue". If we're truly looking for low cost flying... why purposefully add insurance costs? I have a LOT of crosswinds where I fly. I am not afraid of them... but don't see a need to add risk of a ground loop to the whole experience. Remember these things are lighter than a C-150! They are more susceptible to crosswinds.

If this thing were designed per my "fantasy"... it would have been a pulled rivet LSA RV-4A.

My opinion. YMMV

On a related issue - N916K touched on it. The 601XL was designed to use the top skin as a flexing metal "hinge". This is the stiffness in roll that everyone complains about. You can optionally use a piano hinge. Interestingly, it is my belief their QB comes with a real (piano) hinge.

DJ
 
nowlen said:
how about the O-200 ? reliability, easy maintenance, excellent availability, proven track record, 2000 tbo, made in USA !!!.
Click to expand...
I guess we won't see any of these for sale at Walmart then. ;)

nowlen said:
yes, a sliding/removable canopy and tail wheel configuration option is needed. if van's doesn't figure this out there will be alot of builders making these mods and a large resale market for factory new rotex 912's .
Click to expand...
A TW -12 won't ever happen. Just look at the -9A's for the reason. One of the Van's gang once told me they had sold less than 20 -9's (This was two years ago) and they will never get there money out of the engineering, building, and testing effort.
 
jonbakerok said:
Here's what I'm looking for:

-- Fast: The absolute limit of what LSA allows -- 150 mph TAS.
-- Fun: Taildragger, open cockpit if I want it, loops and rolls
-- Cheap: Less than 5 gph mogas in cruise. Trailerable so I can keep it at home.
-- Practical: At least 450 pounds payload.
-- Safe: 6g, 9:1 glide, simple reliable engine, no fuel in the cockpit, pushtube controls
Click to expand...
Huh. I think you're going to have a hard time finding that. If you do, let me know ;)

Seriously, how does 120kt at SL, ISA, MCP (LSA limit) turn into 150 TAS? And how does one do that on 5 gph while also getting 450lb payload (I assume that means "full fuel payload"?) with an open cockpit? And what's a "simple, reliable engine"? 912s? J3300? O-200?

I don't think any of the existing LSA come close to meeting your requirements, nor does any airplane that I know of. We put our primary focus on speed, useful load and handling, with expected operating costs, visibility and availability being the secondary criteria. We did pretty well with the CT. Actually, now that I think about it, it comes pretty close to your criteria, except that the CT is a ND, not a TW, is not approved for aerobatics and would burn more than 5 gph at 150mph. The doors can be taken off (think JetRanger / OH-58), but cannot be opened in flight.

Having flown a number of different LSA designs, I think you might want to add "acceptable stability in gusts" to that. If you don't believe me, come take a ride in the Drunken Dino with me. ;)

TODR
 
Phyrcooler said:
On a related issue - N916K touched on it. The 601XL was designed to use the top skin as a flexing metal "hinge". This is the stiffness in roll that everyone complains about. You can optionally use a piano hinge. Interestingly, it is my belief their QB comes with a real (piano) hinge.

DJ
Click to expand...

I am sure that the model with the piano hinge still has high aileron forces by RV standards.

It is related to the hinge point being at the very fwd point on the aileron.
 
jonbakerok said:

Here's what I'm looking for:

-- Fast: The absolute limit of what LSA allows -- 150 mph TAS.
-- Fun: Taildragger, open cockpit if I want it, loops and rolls
-- Cheap: Less than 5 gph mogas in cruise. Trailerable so I can keep it at home.
-- Practical: At least 450 pounds payload.
-- Safe: 6g, 9:1 glide, simple reliable engine, no fuel in the cockpit, pushtube controls
​
Click to expand...

Here's an airplane that hits a few of these marks; the FK-12 Comet from FK Lightplanes of Germany. At Oshkosh '02 a Florida dealer had one on display and was looking to start importing them, but it apparently didn't work out. It's a good thing I was broke at the time or I'd have whipped out the checkbook and bought it right there... what a cool little machine it was.

It's a biplane two holer and can flown either with open cockpits or a bubble canopy over one or both pits. I sat in the back seat which was fairly roomy and comfortable. Build quality looked really nice; fuse is steel/alum tubing with fiberglass/Ceconite cover while the wings are glass/carbon with partial fabric cover. Taildragger, Rotax 912 power, quick-to-fold wings, pushrod controls, aerobatic, can be bought as a kit (I think, in '02 a kit was available). Fuel tank is in the fuselage, but I don't think that'd stop me.

Downsides?
-It's slow, cruises at around 105 kts.
-Expensive! But then again, most of these imported LSAs are.

If this thing wasn't so darned pricey it'd be my next airplane... it just looked and felt like it'd be a blast to fly.

Check it out;

http://www.fk-lightplanes.com/html/fk_12_comet.html

http://www.fk-lightplanesusa.com/pages/aircraft.htm

A pilot report from TodaysPilot, a UK aviation rag;
http://www.todayspilot.co.uk/flight_tests/dec02/1p1.html
 
I'll accept physics as a limitation.

the_other_dougreeves said:
Seriously, how does 120kt at SL, ISA, MCP (LSA limit) turn into 150 TAS?
Click to expand...

Do the math. 120kt * 1.152 = 138 mph. 138 IAS at 8500' = 160 TAS

the_other_dougreeves said:
And how does one do that on 5 gph while also getting 450lb payload (I assume that means "full fuel payload"?) with an open cockpit? And what's a "simple, reliable engine"? 912s? J3300? O-200?
Click to expand...

5gph is easy -- any of the existing 100hp engines can manage 5 gph at 75% power. As far as "simple", I personally wouldn't put a geared engine with two carbs and water cooling in that category, but I suppose any of the available 4-strokes would be considered "reliable".

450lb payload is not that difficult. The RV12 is shooting for 550. The Zodiac XL claims 481 (with a 6g airframe!). The Rans S-19 is the only one that's under, at 426. 450lbs payload with an aerobatic g-loading might be a problem, but it doesn't have to have a 6g rating at full gross. Heck, none of the Vans planes are rated for 6g's at full gross.

And open cockpit is easy. Just make it a slider with a removable canopy and do the testing to make sure it still flies right without the top. I never said it had to be able to do 150 mph when the cockpit was open. Who would want to?

the_other_dougreeves said:
Having flown a number of different LSA designs, I think you might want to add "acceptable stability in gusts" to that.
Click to expand...

OK, now you're being unreasonable! The only way to make a 1320 lb plane comfortable on gusty days is to raise the wing loading. I'd rather have a decent glide ratio than the ability to fly in 20 kt crosswinds. Of course, I'd rather have it ALL, but we're stuck with this idiotic 1320 lb weight limit.

I'll accept physics as a limitation. But not arbitrary choices made to capture the wrong market.
 
jonbakerok said:
They said the same about the -9. Let the whining begin!



Oops, shot off my mouth without reading the fine print! Since when does Vans post performance numbers in knots? That's still only 135 mph. Not good enough! But I'll hold my tongue 'til we see the numbers with wheel pants.

As far as all the stuff about Jabiru... I gotta admit, both Rotax and Jabiru are foreign animals to me. But the Jabiru sure looks better on paper. If Vans picked it, the availability would improve. By the way, I read in a magazine once that a Rotax comes with a disclaimer that warns you from installing your airplane engine in an airplane! I wonder if that's really true. I'd just about reject that deal on principal.
...
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If you want faster then you don't want an LSA - the 12 is targeted at that (rather strict IMO) set of limitations...

of all your requirements:

jonbakerok said:
Here's what I'm looking for:

-- Fast: The absolute limit of what LSA allows -- 150 mph TAS.
-- Fun: Taildragger, open cockpit if I want it, loops and rolls
-- Cheap: Less than 5 gph mogas in cruise. Trailerable so I can keep it at home.
-- Practical: At least 450 pounds payload.
-- Safe: 6g, 9:1 glide, simple reliable engine, no fuel in the cockpit, pushtube controls
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a Sonex fits all except the removeable canopy & fuel in the cockpit (not sure what the g/r is)

The RV series are some amazing airplanes, and I still want a 7, but my mission now is fun flying and $35~$50 hamburgers. When I'm done with my Sonex I'll have about $30k in it - the biggest selling point was the well developed & supported aerovee engine. Sonex has done their best to keep the affordable in flying. (affordable is a very relative term - I wish I could consider the 10 affordable :D )

One day I'll be able to build/care/feed a 7 (or maybe an 8), but today its a Sonex. If the 12 had been available a year ago when I decided on the Sonex I would have really had to think hard about it, but I still think I would have chosen Sonex because of the engine options (I'll put a jab3300 in if I win the lottery)
 
jonbakerok said:
Do the math. 120kt * 1.152 = 138 mph. 138 IAS at 8500' = 160 TAS
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Ah! 160 MPH, I figured you meant 160 KTAS ... Well, 140 KTAS is easier, but still, the 912S won't develop full power at 8500' DA. Remember that the 120kt limit is for MCP, sea level, ISA. I doubt you're going to get 120kt ISA while you're legal for 120kt SL/ISA; I sure don't (maybe I'm just slow - I've been told this before. ;) You can certainly tune the prop to get that kind of performance, but you might not be legal at SL and ISA.

jonbakerok said:
5gph is easy -- any of the existing 100hp engines can manage 5 gph at 75% power. As far as "simple", I personally wouldn't put a geared engine with two carbs and water cooling in that category, but I suppose any of the available 4-strokes would be considered "reliable".
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According to Rotax's info sheet, 90% power is at 5000 RPM and gives you 5.25 gph. 75% is 4500 RPM and around 4.25 gph. Lockwood reports 75% as 5000 RPM and 5.3 gph. Either way, 5000 RPM = 5.3 gph. However, the conventional wisdom is that the Rotax doesn't like to run below 5200 RPM on 100LL or the cylinders will run cold, causing lead buildup. It's not such an issue on 91/93 MoGas (which runs hotter anyway). So, best cruise (looking at the fuel burn curves) is around 5000 to 5200 depending on fuel and CHTs.

I tend to cruise about 5200 RPM and get 110 KIAS with fuel flows (estimated - no fuel meter on ours) of 5.5 gph. WOT gives about 5400 RPM (depending on DA) and 115kt. On the Dynon-equipped airplanes, I've seen fuel flows of about 6 gph at WOT. If I'm not in any kind of hurry, I use 5000 RPM - the engine is quieter and fuel flow drops off quickly. Speed drops down to around 100kt. The extra 10 knots doesn't sound like much, but at LSA speeds, it is.

Anyway, I plan for 110kt IAS at 5.3 gph, except at higher DAs, when you'll get a little less IAS. This is consistent with other CT owners that I know. The other LSA I've flown (Evektor, T-211) are not as fast.

jonbakerok said:
450lb payload is not that difficult. The RV12 is shooting for 550. The Zodiac XL claims 481 (with a 6g airframe!). The Rans S-19 is the only one that's under, at 426. 450lbs payload with an aerobatic g-loading might be a problem, but it doesn't have to have a 6g rating at full gross. Heck, none of the Vans planes are rated for 6g's at full gross.
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Just to be clear, do you mean useful load (i.e., payload with no fuel)? We have 605lb and we're on the heavy side for a CT (715lb empty). The Evektor is around 550 lb with the new (paperwork only) MGTW increase to 575kg (1267 lb), but watch the empty weight - it can exceed 720 lb if you pile on the options. S-19 looks to be the heaviest design out there.

jonbakerok said:
OK, now you're being unreasonable! The only way to make a 1320 lb plane comfortable on gusty days is to raise the wing loading. I'd rather have a decent glide ratio than the ability to fly in 20 kt crosswinds. Of course, I'd rather have it ALL, but we're stuck with this idiotic 1320 lb weight limit.
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All LSA are going to be a little "tender" in gusts, but there is a good amount of variation between them. The CT has a wing loading at 12.3 lb/sf. The T-211 loading is almost identical, but is much more stable in gusts.

TODR
 
LSA design

A non-supercharged aircraft engine is capable of making 75% of rated horsepower at 8000' elevation on a standard day.

150 mph TRUE airspeed at 8000 ft translates to 130 mph INDICATED airspeed.

Therefore, the problem for LSA designers is this:

Design an aircraft that does not exceed 138 mph INDICATED airspeed at sealevel at full power, but is capable of at least 130 mph INDICATED airspeed at 75% power.

LSA design is an exercize in designing to artifical limitations, much like designing a formula racer. In this case, there's a strict limit on one particularly inaccurate way of measuring top speed at full power, but no limit on actual velocity at any given altitude other than sealevel. They should be designed accordingly.
 
Hello out there,

At some point I even considered a Jabiru 3300 for my RV9A (120 bhp should be enough, right?) It is smooth (6 cyl.), it is light, cheap and simple. But?..also, it seems to be common knowledge that it does not put out 120 bhp but maybe 95-100 max! (the same rate goes for the 2200!)

Anyway, to get the max power you will have to run it at 3300 RPM. Besides that it will be very noisy at that RPM, the prop efficiency will be very bad. To get the best out of it, you could try the silence V-prop. I do like the concept of this prop, it is very light, constant speed, cheap, German proven quality and easy to operate. I would order one immediately if they made one for the 160 HP Lycoming engine.

Apart from the fact that the JAB3300 does not seem to make the claimed power, it seems to have a history of being unreliable to ( ?search? to find out more). A friend of mine had his JAB3300 quit on take-off, just two months ago. Crashed into the bushes and luckily survived. So far he has not figured out why it quit though. At the moment he is building his 7th experimental, so I do consider him to be competent.

I suggest that before you buy a Jabiru, you ask the supplier to put it on a test stand to show you that it does put out the power they claim, before you sign anything! Stick with the proven Rotax if they can?t.

Regards, PilotTonny
 
The early Jabs had serious problems with reliability and have undergone several major redesigns to address these issues. Have these revisions solved the problems? Not enough flight time has been accumulated to know. I hope so because it is a cool engine.

While the 912 may seem complex, it has proven to have excellent reliability and durability when operated by the book- and it does have hundreds of thousands of flight hours to prove it.
 
Horsepuckey!

At some point I even considered a Jabiru 3300 for my RV9A (120 bhp should be enough, right?) It is smooth (6 cyl.), it is light, cheap and simple. But?..also, it seems to be common knowledge that it does not put out 120 bhp but maybe 95-100 max!

Anyway, to get the max power you will have to run it at 3300 RPM. Besides that it will be very noisy at that RPM, the prop efficiency will be very bad. To get the best out of it, you could try the silence V-prop. I do like the concept of this prop, it is very light, constant speed, cheap, German proven quality and easy to operate. I would order one immediately if they made one for the 160 HP Lycoming engine.

Apart from the fact that the JAB3300 does not seem to make the claimed power, it seems to have a history of being unreliable to ( ?search? to find out more). A friend of mine had his JAB3300 quit on take-off, just two months ago. Crashed into the bushes and luckily survived. So far he has not figured out why it quit though. At the moment he is building his 7th experimental, so I do consider him to be competent.

I suggest that before you buy a Jabiru, you ask the supplier to put it on a test stand to show you that it does put out the power they claim, before you sign anything! Stick with the proven Rotax if they can?t.

Having owned a Jab 3300 for six years and 460 hours, I would disagree with every point you made. Except for the one about your friend crashing. And without a cause, how can you point a finger at the Jab?

Tony
 
rv6ejguy said:
The early Jabs had serious problems with reliability and have undergone several major redesigns to address these issues. Have these revisions solved the problems? Not enough flight time has been accumulated to know. I hope so because it is a cool engine.
Click to expand...
The T-211 I flew has an early J3300 without hydraulic lifter adjustment - A&Ps were adjusting every 25 hours! They have since improved the engine. Really liked how it flew....

TODR
 
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