Sport Pilot Talk

tu16 · Joined: 18 Feb 2010 Posts: 85 Location: Bellevue, WA

Hi, from time to time I see some vague references in LSA specs to 914 as a powerplant option (Evektor SportMax Turbo, etc.) - usually, w/o much of details to follow.

Apart from additional weight, cost and TBO considerations it would seem that some West Coast pilots could appreciate a turbocharged engine to keep LSA MTOW performance through high terrain flying at sea-level one which could be be a great benefit for safer and more accessible cross-country flying in high country. (Not that it can't be done with normally aspirated engine, of course )

But did anybody actually see/fly LSA equipped with 914 turbo?

Although Rotax makes couple models of 914 with flanges for fixed pitch prop - there is an opinion on the net that turbo works well only with constant speed props and therefore, is not recommeded or can be used in LSA that is limited by the rule to a fixed pitch prop. I'm not an expert here and I am interested to learn more. Anybody can offer more detailed explanations, opnions on this topic?

Thanks!
Alex.

jake · Joined: 25 Oct 2009 Posts: 80 Location: minnesota

There are some LSAs that come with the 914. Evector offers the 914, TL ultralight has it available in the Sting and Sirius. I believe it is now available in the CT but may only be certain models. There is no reason that it cant be in an LSA. They are substantially more expensive though as all turbos are. I think about 10-15 thousand more! Whats another 15 grand when your spending over $125000 to begin with!

Jake

rfane · Joined: 26 Apr 2006 Posts: 214 Location: Sunnyvale, CA

Being limited to a ground adjustable prop in a US LSA, makes the 914 a waste. If you can't take advantage of the continuous hp output of a turbo engine, what's the point.

Jack Tyler · Posted: Mon Jan 17, 2011 6:02 am Post subject:

TU16:

"...it would seem that some West Coast pilots could appreciate a turbocharged engine to keep LSA MTOW performance through high terrain flying...Not that it can't be done with normally aspirated engine, of course."

I think you may have partially answered your own question.

I read a Flying article the other day about a 17 yr old H.S. student who, to celebrate his brand new PPL, flew his Dad's Cub cross-country from Maryland to California. No turbo... :D

tu16 · Joined: 18 Feb 2010 Posts: 85 Location: Bellevue, WA

rfane wrote: Being limited to a ground adjustable prop in a US LSA, makes the 914 a waste. If you can't take advantage of the continuous hp output of a turbo engine, what's the point.

Thanks! That is exactly an argument I'm interested in.

As DA increases both HP "shaft output" of normally aspirated engine AND prop efficiency decreases. With turbo at least one of the two negative tendencies stopped - but what is a total net result? Is it truly a waste of turbo? How will it look like - one would have to REDUCE RPMs and power output of a turbo in LSA at 12,000 MSL in order not to overspeed fixed prop in a thinner air with constant HP output? What would performance numbers be, compared to SL and normally aspirated engine?

jake · Joined: 25 Oct 2009 Posts: 80 Location: minnesota

Most LSAs have plenty of climb. Set the prop to use the full 115 hp available at take off and you will still be able to get full cruise at altitude.
Yes a variable pitch would be better but you will definitely get a performance increase over the 912.

Jake

tu16 · Joined: 18 Feb 2010 Posts: 85 Location: Bellevue, WA

Just thought I share with you results of my e-mail exchange with Petr Javorsky, Czech project lead of SportStar Max of Evektor.

With 914 and constant speed prop climb rate at 5,000' is 1100fpm, 10,000' is 850fpm.
I also got comparison numbers for SportStar performance between fixed prop and constant speed prop for 912 to extrapolate to 914.

The difference is less than 10% in climb rate at sea level and no difference at 10,000. (Ground adjustable prop is apparently set for cruise at altitude )

914 would cost extra $15,000 and ~20lbs. Totally loaded with modern avionics, BRS and 914 SportStar MAX Turbo would weigh 803lbs empty and would set you back for 180K ;)

Looks like a perfect plane for upcoming LSA Expo in Colorado. It would be a waste of opportunity not to bring Turbo model to Denver area... ;)

drseti · Joined: 28 Nov 2009 Posts: 1387 Location: Lock Haven PA

tu16 wrote: Just thought I share with you results of my e-mail exchange with Petr Javorsky, Czech project lead of SportStar Max of Evektor.

I just had an email exchange with Petr myself (on an entirely different subject), and as always, he was responsive, timely, and most helpful. A great resource!

Quote: With 914 and constant speed prop climb rate at 5,000' is 1100fpm, 10,000' is 850fpm.

That's much better performance than a SportStar with 912, of course -- but I'm a little confused. I'm under the impression that a turbocharged engine spinning a fixed pitch prop is inefficient and not practical -- and the US LSA rules specifically exclude constant speed props. So, what's the point of the 914 in an LSA?

tu16 · Joined: 18 Feb 2010 Posts: 85 Location: Bellevue, WA

drseti wrote: I'm under the impression that a turbocharged engine spinning a fixed pitch prop is inefficient and not practical -- and the US LSA rules specifically exclude constant speed props. So, what's the point of the 914 in an LSA?

Heard that opinion many times too. However, it seems that inefficiencies of fixed pitch prop vs constant-speed prop do not significantly diminish performance gains from keeping shaft power up. If I set fixed pitch to deliver 850fpm at 10,000' as a constant speed prop - I will lose in performance at sea level compared to constant speed. How much? Petr suggests that it would have the same percentage effect as their 912 measurements for fixed/constant - which is about 10% in fpm at sea level. With 115hp that should be enough, consider that with constant speed you'd get a whopping 1320fpm at MTOW. I could live with 1200fpm (-10%) for fixed pitch....

According to Petr:

Quote: I expect difference between performance of SportStar having ground adjustable prop (Klassic) and Rotax 914 would be similar to difference between SportStar having R914 and R912 and flight variable prop (SR3000).
So for example if you would add difference of rate of climb of the SportStar having R914+SR3000 against R912+SR300 to the rate of climb of the SportStar having R912+Klassic prop, you would approximately get rate of climb of the SportStar with R914 and Klassic. The same with the horizontal speeds.