To SPEC LSA
- Thread starter Edgefly
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Skylane81E
Final Approach
Yes, many exceed it at altitude (TAS)
Jimmy cooper
En-Route
Check the rans site. The new s20 is very close.
Old Geek
Pattern Altitude
Flight Design CT's can if the prop is pitched right. Mine is much more comfortable and fuel efficient at 100-110 knots though.
Geico266
Touchdown! Greaser!
RV12 easy, but I found 130 mph the sweet spot.
zaitcev
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Pete Zaitcev
I think you meant RANS S-19 Venterra. The S-20 Raven is their new hybrid of S-6 Coyote II fuselage and S-7 Express wings. You'd need 250 hp to propel that at 121 knots, and indeed the website promises modest 96 knots, which is still pretty good for an airplane in the class of Chief, on 100 hp. The S-19 is a slick LSA that was designed to meet the legal cruise limits. Unfortunately it was overpriced and I think they didn't sell any, except as kits. Even so RV-12 beats is in every possible respect, except speed, which is legally limited. RV-12 is cheaper and it's lighter, which is very important in LSAs.
A few slicker designs met the legal limit. CTLS did (like Tim said above). I think Evektor SportStar came very close. And there were a few lesser known airplanes. IIRC Falcon did on 115 hp IO-233-LSA. Dova claimed that Skylark was that fast, too, although looking at their numbers I'm not sure I can trust them.
Experimentals routinely did it, too. If RV-12 is too expensive for you, look at Sonex. That one hit the limits on 80 hp!
bullwinkle
Pattern Altitude
How is your prop pitched? The "wisdom of the CT gurus" is that you pitch it to get 5600-5700rpm at WOT straight and level at your normal cruise altitude. This gets the airplane capable of maximum horsepower and improves both climb and performance over the too-coarse factory settings. I gained both cruise speed and climb (almost 300fpm!) doing this.
My plane cruises 114 knots at 5200rpm and 124 knots WOT at 4000 feet. I climb at 1200fpm solo and 900fpm near gross weight.
The reason I ask is I'm wondering if at 110kt you are cruising at 4600-4800rpm. There are some harsh harmonics at that RPM that can increase wear on the engine. It does better at 5000rpm plus, and the 912 was designed to live its entire 2000 hour life at 5500rpm, so you won't hurt it doing this.
Not trying to tell you how to operate your airplane, just passing along what I have learned from people who know CTs and Rotax engines much better than I ever will.
Old Geek
Pattern Altitude
How is your prop pitched? The "wisdom of the CT gurus" is that you pitch it to get 5600-5700rpm at WOT straight and level at your normal cruise altitude. This gets the airplane capable of maximum horsepower and improves both climb and performance over the too-coarse factory settings. I gained both cruise speed and climb (almost 300fpm!) doing this.
My plane cruises 114 knots at 5200rpm and 124 knots WOT at 4000 feet. I climb at 1200fpm solo and 900fpm near gross weight.
The reason I ask is I'm wondering if at 110kt you are cruising at 4600-4800rpm. There are some harsh harmonics at that RPM that can increase wear on the engine. It does better at 5000rpm plus, and the 912 was designed to live its entire 2000 hour life at 5500rpm, so you won't hurt it doing this.
Not trying to tell you how to operate your airplane, just passing along what I have learned from people who know CTs and Rotax engines much better than I ever will.
Roger Heller and I have had this discussion for years. I'm turning around 5100 rpm at full throttle cruise. I've played around with the prop pitch a couple of times and this seems to work good for me. I might try taking out another degree at the next annual, but my mechanic (rotax trained at the factory in Austria) says I'm not hurting anything.
CharlieTango
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CharlieTango
You have your throttle wide open yet there is more power available so your speed and climb are limited. If you use less pitch and can achieve 5,500 then you can access all the cruise power your engine can deliver instead of lugging it a bit.
Look at the power curve and you can see that 5,100 @ WOT is reduced power.
bullwinkle
Pattern Altitude
Mine was set like yours when I got it. After making the change I gained 300fpm climb and ten knots in cruise. I highly recommend you try it, you can always go back if it doesn't work for you.
SportPilotCO
Pre-takeoff checklist
My Gobosh 700 does 118-125 Kts TAS at between 8000 and 9500 MSL out here in Colorado. One note on the max speed discussion for LSA's. It is 120 Kts calibrated airspeed at sea level, standard atmosphere, max continuous power for the engine. This means as stated previously that they can and do go in excess of 120 Kts at altitude.
Also on the subject of the S-19, they did in fact sell a few S-LSA models. I had the pleasure of flying one at the factory a few years ago. It is a very nice aircraft. It does have a few minor issues but for a slider LSA it is a really nice plane. I was at the factory for their annual fly in recently and spent time sitting in the in progress S-20 and I really like it. I can't wait until it is finished to go up for a flight. Like the OP said, you aren't going to scream cross-country in it.
I have also flown the Vans RV-12 and am in fact building one, almost finished with the fuselage kit. It flies really nicely as well. I didn't get to cruise test it but it handled really well and I suspect you will get every bit of the performance I am seeing in the Gobosh.
Carl
Also on the subject of the S-19, they did in fact sell a few S-LSA models. I had the pleasure of flying one at the factory a few years ago. It is a very nice aircraft. It does have a few minor issues but for a slider LSA it is a really nice plane. I was at the factory for their annual fly in recently and spent time sitting in the in progress S-20 and I really like it. I can't wait until it is finished to go up for a flight. Like the OP said, you aren't going to scream cross-country in it.
I have also flown the Vans RV-12 and am in fact building one, almost finished with the fuselage kit. It flies really nicely as well. I didn't get to cruise test it but it handled really well and I suspect you will get every bit of the performance I am seeing in the Gobosh.
Carl
jnmeade
Cleared for Takeoff
This is one of Roger's mantras but if you go into the documentation and check the various RPM at various pitch settings and get it right I don't think this holds true.
Europeans pitch the 912 differently and seem to get along fine.
bullwinkle
Pattern Altitude
Fair enough, there is debate on the harmonics. I don't think the assertion that the CT performs better with a prop pitch set to achieve an RPM higher than 5100rpm max level WOT is in much doubt though.
zaitcev
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Pete Zaitcev
Europeans are allowed to fly variable pitch props with their 912s in the same CTs and GXes.
jnmeade
Cleared for Takeoff
Of course. And they fly them at different WOT RPM settings than many in the U.S. preach. Thus the discussion about a harmonic zone that may be more fiction than fact.
CharlieTango
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CharlieTango
Even if you discount the harmonic issue what sense does it make to present such a large load (fixed pitch) that you reduce your motor to be effectively a 90hp instead of 100? 5,100RPM @ WOT means that you are giving up 7% of available cruise power, 5,500RPM @ WOT means that you can utilize all available cruise power or throttle back for less.