Dream plane

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roger lee
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Re: Dream plane

Post by roger lee »

You should pick a plane that serves your everyday mission and use. That may not be the same plane for everyone.

"On speed, I am hearing that with the turbo or the 912iS and the prop set to max cruise, top speeds for these aircraft are in the 125-128 range ... Anyone have a view on that?"

The 912iS doesn't tend to be any faster than the 912ULS. I'm around both engines and different planes a lot. It's all hull design and prop pitch. So even with the same plane setup is everything. Too much pitch and your entire flight package is garbage. Too little pitch and you climb well, but the cruise and fuel economy suffer.

The CT's all have chutes and weight is 30 lbs. For that aircraft it's no big deal and a nice to have insurance policy, but may not be a determining factor for some.

For example:
I have a Flight Design CTSW and my friend has a Flight Design CTLSi (912iS eng). I tend to fly faster at low altitudes with less fuel, but when we climb up to higher altitudes i.e. 7K-10K he flies at lower rpm and with a 20% less fuel use. At lower altitude I'm at 5200 rpm and he's at 5300 rpm. At those higher altitudes that is reversed because his onboard computer does a better job of fuel/air metering. At lower altitudes an his 5300 rpm he still burns less fuel than I do at 5200 rpm.


Hull design is the biggest factor over just dry aircraft weight. There are many LSA or light aircraft with a Rotax 912 ULS 100 HP that will only fly 80-90 and some at 120 and then one in Europe that flies over 200. Weight does play a factor, but not because of another 20-50 lbs of engine and design weight, but usually because of adding a 180-250 lb pilot and or passenger.

The hull of an airplane is similar in concept to a sailboat. An 8 kt. hull means just that. Put all the HP behind it that you want and it is going 8 kts.

Then prop and rpm will figure in after hull design is factored in. Weight is another added factor so your everyday mission parameters makes a difference. As an example: Do you weigh only 150 lbs and always fly solo or do you weigh 220 lbs and always have a passenger. If you don't believe that then you guys with an LSA know the difference in climb and performance from a solo flight versus a dual flight with baggage. If we had retractable gear on our 120 knt. LSA we would cruise even faster after we dumped that drag.

As far as density altitude. The 914 does shine here, but I can still take off at 10K DA and be 100 lbs. overweight in my CTSW. If the prop is too course it isn't going to happen. A well balanced RPM for your individual mission can be key to a well performing aircraft. Even prop MFG's and prop size eventually figure in the equation.

I have flown nothing, but light aircraft since 1980. Hull design and parasitic drag are the main determining factors.


The new Rotax 915 turbo with intercooler won't be out for approximately 1-1.5 years with a price tag of about $40K and possibly a few dollars more. It is being designed primarily for the Gyro users. Its added weight and physical size requirements won't be conducive to our LSA industry unless the FAA has a weight change and LSA MFG's redesign their aircraft firewall forward. Putting it under an existing airplane cowl is unlikely due to its space requirements. It will happen, but that isn't the engines target group.

I have never seen a 912ULS at 5300 rpm use only 4.4 gph. That's even way below Rotax specs.
Roger Lee
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Nomore767
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Re: Dream plane

Post by Nomore767 »

MackAttack wrote:Nomore, did you wind up with the Sirius 3000 about which you posted a while back? If so, how did you spec it out? Empty weight? Apologies if you posted this elsewhere and I missed it ...

On your other Sirius thread, you observed the difference between sales people quoting figures but not the trade-offs. I will say that the Tecnam person with whom I spoke was COMPLETELY clear about the empty weight, payload, useful load trade offs in connection with the Astore and P2008 discussion we were having ... He was very clear that flying with two adults necessitates about a 3-hour range to be under 1320 and that the max range figure was a single-occupant figure. Should I wind up going with one of those, I will know what I'm getting into. And I will also say that there are a few LSAs which cruise at or near 120 knots and have a pretty stout useful load (e.g., the Bristell).

Re the 914 and density altitude, here in Houston during the summer, density on the ramp can be 2500-3000 feet on a 95-degree F and humid day. So a normally aspirated engine will suffer performance and climb rate loss even in a near-sea-level environment. And that's why I'm leaning towards the 914.

Cheers!

Mack Attack,

After a few demos of different LSAs as well as flying others in flight schools, as well as an abundance of research and questioning, I bought a brand new 2014 RV-12 SLSA. I opted for all the options that were available at the time ADSB, A/P, A/P and Knobs panel, wheel fairings, SkyView Touch (they came out with dual screens a few months later which I would have opted for). With the 912ULS engine the airplane's empty weight is 765lbs with a 555 useful load.
With full fuel on a 20 gallon fuel tank my wife and I can fly with full 50lbs baggage at 1320lbs although I usually always fly solo. I can easily do the LSA 120kts and the wheel fairings seem to add a few extra knots. The performance of the Rotax has been stellar. Even with no flaps the airplane is ready to fly almost when the throttle has reached full open and landing I usually make the first turnoff . Here in SC we regularly have high density altitude days and they've never been a problem, even in summer temps that regularly hit the upper 90s and over 100F. I can typically reach pattern altitude on take-off crossing the end of a 5000' runway or at last on the crosswind turn in winter /spring. With half flaps its even better. In summer heat not quite as good but still pretty good.

Then again, this is sport flying and I actually don't care a whole lot as long as its fun, relatively simple, and cost effective.

Based on my personal mission the RV-12 has been nothing short of brilliant for ME and new cost was about $85k less than a couple of other LSAs I looked at. Maintenance and servicing has been simple and straightforward. I opted not to take the Rotax course yet since I'm having my mechanic change oil at 50 hours and plugs, brakes etc at the annual for which he charges $350 plus parts and anything extra. I can't argue with the economics and he's a fully trained and qualified Rotax mechanic at Lockwood and to be honest he hasn't had much to do.
Based on actual fuel loaded I plan and get 4.45 gph and have been using 93 non ethanol mogas and have just switched to 93 E10 as the non ethanol supply is drying up around here. I carry Decalin for longer cross country flights where 100LL is the only fuel available.

To be clear, you asked and I'm reporting MY personal experience based on MY personal sport flying mission.

I haven't dealt with Tecnam USA so my experiences were all with the previous USA dealer. Your report about your experience with Tecnam is very encouraging. I've always tried to provide realistic comments and thoughts rather than plain negative.

I have demoed a few LSA and I haven't seen an LSA that I didn't like but so far the RV-12 has met all my needs for great sport flying whilst being economical and cost effective. That's MY personal view. Bristol and Tecnam LSAs are very nice to be sure.

My fuel use is based on actual fuel loaded. For example looking at the log I keep in the airplane my last flight was 1.2 Hobbs and I left with full fuel 19.8 gallons. After landing I poured in 5.2 gallons based on what I pump into each container every time and tank was full.
I don't claim 4.4 -4.5 gph in cruise but it is what I plan for based on how I fly, trips I've done, and fuel I load, overall per hour. I also plan on 3 hours 15 minutes as max cruise and a hard 4 gallon reserve and this has turned out well. I wrote earlier that I planned for 4.4-4.5 gph in cruise, but I should have said I plan for that for a flight overall rather than a cruise fuel flow.

Based on all the above the 912ULS engine has worked out to be exactly what I wanted and needed. Your mileage may vary based on your own needs and where you live.
MackAttack
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Re: Dream plane

Post by MackAttack »

Roger and Nomore, thanks for taking the time to post replies this morning. That's all great feedback and very helpful real world info especially on whine choice, prop pitch and DA Roger I agree that the 915 is not going to be a big factor in the US-LSA market. And congrats on the Vans Nomore!!

Congrats on the
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drseti
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Re: Dream plane

Post by drseti »

roger lee wrote:I have never seen a 912ULS at 5300 rpm use only 4.4 gph. That's even way below Rotax specs.
On my most recent trip to Florida, cruising at that power setting, my 912ULS-powered Evektor SportStar Max burned a measured 5.2 GPH, and averaged 106 KTAS. That comes to 23.4 MPG (my Porsche does much better than that :wink: )
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
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FastEddieB
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Re: Dream plane

Post by FastEddieB »

drseti wrote:...(my Porsche does much better than that :wink: )
How about your MG?
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drseti
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Re: Dream plane

Post by drseti »

The MG's issue was not MPG, so much as MPE (miles per engine). :cry:

In fact, I traded in the MG two years ago on my first Porsche. Good deal all around!
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
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jetcat3
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Re: Dream plane

Post by jetcat3 »

MackAttack wrote:Resurrecting this thread, if folks don't mind, as I'm in the market ATM ... Being more of a low-wing fan, I found this thread interesting and wondered if folks still had any thoughts around this topic. On the low-wing side, I'm considering the Bristell and the Tecnam Astore (which was just coming out when this thread was active). Two very attractive and fast aircraft, high fit/finish and expensive when completely kitted out. At the opposite ends of the empty weight spectrum (720 vs 820 or thereabouts)... I realize there are lots of great low wings out there (SportCruiser, RV12, Evektor, etc...) No disrespect to any of them, but I think (based on paper research and flying the left seat of my sofa vigorously!!) that the Bristell and Tecnam reflect the latest design thinking.

Thoughts on engine selection (912 iS sport vs 914 turbo)? Turbo is much heavier, but delivers full performance in climb and cruise to altitude. I am based in Houston where DA is an issue during the summer and getting to cool air QUICKLY is a big deal, not to mention missions to West Texas or elsewhere along the Gulf Coast, so leaning towards the turbo, although I realize fuel economy is less and there is likely more MX.

Chute? No Chute? Another 37 pounds ... I won't even bring up the 40 pounds for the Flycool air conditioner ... But I could literally cram all of those options in a Bristell and come in at about the empty weight of the Tecnam.

On speed, I am hearing that with the turbo or the 912iS and the prop set to max cruise, top speeds for these aircraft are in the 125-128 range ... Anyone have a view on that?

Thanks in advance for all the incoming!

PS- Not overly concerned about flying 6-hour legs; my "personal waste disposal systems" won't really lend themselves to that, so am not freaking out if I can't take 2 adult males and fuel fuel ...
Mack,

I recently had the opportunity to fly a turbo P2008 and a fuel injected Astore. The turbo engine really blew me away. To me the 912 ULS and 912 iS are very similar in power and smoothness. The 914 was noticeably smoother and seemed quieter at lower RPM's but that may not be true. The power difference was so significant though. It was a cold day with density altitude close to sea level and I didn't expect there to be a big difference. Boy was I wrong! The turbo engine had Mark Gregor and I climbing 1400 fpm and we hit 130 KNOTS indicated at max cruise rpm. I know Shannon has said the Astore turbo will do 128 KNOTS true airspeed which is pretty dang quick. 118 KNOTS true with the fuel injected engine on the Astore. Astore was a sweet flying bird! I can't comment for Bristell as I haven't flown one. Only flown a Sportcruiser. I'm a HUGE fan on the 914 UL engine. Hope that helps some!

Drew
MackAttack
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Re: Dream plane

Post by MackAttack »

Thanks!! I am working with both Mark and Shannon to try and get into both aircraft, either in MN or in FL. Appreciate the feedback!
jetcat3
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Re: Dream plane

Post by jetcat3 »

MackAttack wrote:Thanks!! I am working with both Mark and Shannon to try and get into both aircraft, either in MN or in FL. Appreciate the feedback!
Sweet! That's awesome. You'll love flying them! They are amazing birds.

Drew
Nomore767
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Re: Dream plane

Post by Nomore767 »

drseti wrote:
roger lee wrote:I have never seen a 912ULS at 5300 rpm use only 4.4 gph. That's even way below Rotax specs.
On my most recent trip to Florida, cruising at that power setting, my 912ULS-powered Evektor SportStar Max burned a measured 5.2 GPH, and averaged 106 KTAS. That comes to 23.4 MPG (my Porsche does much better than that :wink: )
Paul,

I was just trolling the Vans Air Force site on a different subject matter and I came across a thread about comparing possible build choices for Vans guys and there were a few posts about fuel burns in the RV-12.

The following post was made on the thread and the guy who wrote it is a retired Boeing engineer who likes to talk performance stats and has been measuring the Rotax 912 ULS he has in his RV-12.
Posted in the spirit of FWIW!

Question:-

"If you have a fuel burn close to 4 gallons; what is your cruise speed? At what RPM are you running the engine at that moment? An ex Rotax owner told me that as long as you stay below 5000 RPM, it is pretty reasonable. Go over it and the fuel consumptions goes up to the sky, even much higher that an regular Lycoming consumes."

Answer:-

Flight late afternoon Dec. 24 (scouting for Santa....) RV-12

0S9 to KPWT 33.9nm

OAT = 35 deg F
No wheel pants
Estimated weight = 1080 lbs
Typical data point:

Alt = 3011 ft
TAS = 113.9 kts
RPM = 4875
FF = 4.1 GPH (USG)

The flight was:
Hobbs = 31 minutes.
Tach Time = 24 minutes

During the cruise portion, the:

RPM varied from 4284 to 5332 RPM
Altitude averaged 3000 ft
TAS varied 104.3 to 121.6 kts - average about 112 kts
FF varied 3.6 to 5.4 GPH - Average 4.4 GPH

Estimated fuel consumed = about 1.8 gals (USG.) This is a little shaky as it's coming off the float and started from a level just above the float's upper cutoff - but pretty close.

Prem. Mogas @ $3.40/USG = Fuel cost for flight approx $5.98. USD.
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drseti
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Re: Dream plane

Post by drseti »

That's a rather short flight for a meaningful test, Howard. The reason I posted my FL results is that they encompassed real-world operating conditions: multiple legs, takeoffs, landings, climbs, descents, and traffic patterns. And instead of relying on fuel quantity indicators, I started with full tanks each leg, topped up after each leg, and used fuel truck totals dispensed.
Lockwood did a similar but superior test comparing the 912 ULS to 912iS a couple of years ago. They mounted one of each on an Aircam, fed each off a separate wing tank, and flew to Oshkosh and back. Since both engines were set up identically, and operated identically, on the same airframe in identical environments, they got a really good calibration on comparative fuel burn. That has to be better than compairing apples to oranges.
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Flocker
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Re: Dream plane

Post by Flocker »

drseti wrote:Lockwood did a similar but superior test comparing the 912 ULS to 912iS a couple of years ago. They mounted one of each on an Aircam, fed each off a separate wing tank, and flew to Oshkosh and back. Since both engines were set up identically, and operated identically, on the same airframe in identical environments, they got a really good calibration on comparative fuel burn.
Interesting. Were the results posted anywhere?
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drseti
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Re: Dream plane

Post by drseti »

Not to my knowledge. I saw the plane last January, with the two different engines installed, and Dean Vogel told me about the experiment. So, he would be the one to ask.
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Nomore767
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Re: Dream plane

Post by Nomore767 »

drseti wrote:That's a rather short flight for a meaningful test, Howard. The reason I posted my FL results is that they encompassed real-world operating conditions: multiple legs, takeoffs, landings, climbs, descents, and traffic patterns. And instead of relying on fuel quantity indicators, I started with full tanks each leg, topped up after each leg, and used fuel truck totals dispensed.
Lockwood did a similar but superior test comparing the 912 ULS to 912iS a couple of years ago. They mounted one of each on an Aircam, fed each off a separate wing tank, and flew to Oshkosh and back. Since both engines were set up identically, and operated identically, on the same airframe in identical environments, they got a really good calibration on comparative fuel burn. That has to be better than compairing apples to oranges.
Paul,

The example I posted was in answer to one question on the thread and he posted it as an example of how he meticulously figures his fuel consumption. He's a retired Boeing engineer and totally anal in this regard.

He's been doing the same thing since he built his RV.

Anyway, for me I flew 1.6 Hobbs yesterday and started with a full tank 19.8 and shut down with 12 gallons using 7.8 gallons. Overall fuel burn yesterday 4.8 gph. Using Hobbs time it can vary a little since you could be just starting the tenth of an hour or just finishing.

Whatever...I and others have found the Vans book numbers to be pretty conservative for the 912ULS.

What was seriously cool was the SkyView indicating a 140kt groundspeed on the descent to home field with a serious southwesterly tailwind!!
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Re: Dream plane

Post by JimC »

"An 8 kt. hull means just that. Put all the HP behind it that you want and it is going 8 kts"

I thought that for a given airframe and weight, the speed increases with the cube root of the horsepower ratio? In other words, it takes eight times the power to go twice as fast.
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