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Rotax 916iS

I’ve been waiting to hear them announce this since I was at Sling in S.A. Almost a year ago! That’s close to 20 more HP than the 915iS, which is not insignificant…..

The trick to putting it on an RV is going to be W&B and the added nose length due to a lighter powerplant - yaw stability is not to be ignored….
 
It's been Rotax's worst kept 'secret'. Flown extensively in the drone market, it does mean it arrives in the GA world with a 2,000hour TBO.

Did you fly it Paul?
 
It's been Rotax's worst kept 'secret'. Flown extensively in the drone market, it does mean it arrives in the GA world with a 2,000hour TBO.

Did you fly it Paul?

Haven’t had a chance to fly it yet - they didn’t have one quite yet when I was at Sling, and haven’t seen on “in the wild” here in the states. But I think one will come along before I know it…..
 
I’m just hoping for a 918 - 180 HP. The extended nose on the -8 will be cool, too. (“Will be”, not “would be” - positive thinking here!)
 
EdH: "159hp for three minutes, then 137hp to 23,000ft service ceiling. A good match for an RV airframe in future?"

The trick to putting it on an RV is going to be W&B and the added nose length due to a lighter powerplant - yaw stability is not to be ignored….

This could be a fantastic package for an RV-3. Extending the fuselage a few inches forward would create a small baggage space and more leg room for tall pilots. A light C/S prop would help balance too. (the Rotax 914 F supports a hydraulic C/S prop, so I would assume the 915 would too?)

And while I was at it, I would extend the fin and rudder up a couple inches to add a counterbalance horn, which would give a bit more fin area to counter the longer nose.
 
The power at altitude is impressive, but how much flying do RVs do at high altitude cruise? What's the point of flying a sport plane straight and level?

Some folks, of course, do a lot of cruising, but for many pilots, power at non-oxygen altitudes will be more important.

Then again, back when I lived at 5,000 feet MSL...
 
Any idea how much change in spin characteristics you would get with the longer nose? As long as you keep the cg location the same spin entry should not change but the change in longitudinal moment of inertia will effect spin rate and angle I am just not sure if it would be enough to be noticeable or not. I am building a -9A so I won't be spinning intentionally but I would hate to find out the hard way that there is an issue. Also does anyone know if there is a good handbook for calculating longitudinal stability changes?
 
Any idea how much change in spin characteristics you would get with the longer nose? As long as you keep the cg location the same spin entry should not change but the change in longitudinal moment of inertia will effect spin rate and angle I am just not sure if it would be enough to be noticeable or not. I am building a -9A so I won't be spinning intentionally but I would hate to find out the hard way that there is an issue. Also does anyone know if there is a good handbook for calculating longitudinal stability changes?

Yaw stability and the airplane becoming is where risk can get dicey with a longer nose. Imagine entering a slip and the nose turns into a sail that prevents you from straightening back out to coordinated forward flight. Or worse, it goes truly divergent and the nose continues around to someplace the tail is supposed to be. I am not saying that will happen, but it's the sort of risk-related concern that has to be looked at with trained design eyes and math.
 
This is cool! It looks like it can be light, which is a good thing, but not totally straight forward. It produces power at altitude, which is great for high density altitude takeoff, but still limited by VNE in cruise. The problem, if there is one, that we have with engines is price. Power production is not an issue. weight is not an issue though in general lighter is better. What we need help with is price, if this doesn't address that, then it isn't really that interesting except for the high density altitude takeoffs.

Tim
 
It dosent help with purchase price. I just talked to Lockwood aviation and the purchase price for the 916is from them is $49,995. That does include the Rotax care support so that is somthing but it is still fairly high. Though I also talked to Barrett engines and they quoted $40-42k for an overhauled 360 which is about what it costs new from Van's.
 
Weight delta may not be as bad as being guessed here: Rotax's configurator lists this engine at 207 lbs. But that's without radiator/coolant/plumbing/ducting. Installed length (prop flange to firewall) is the same on a 915-equipped Sling TSi vs an RV-7 with O-360 (33").
rotax 916.jpg

Add a (heavy) Hartzell aluminum CS prop plus the radiator parts and you'll be in the ballpark of a 320/360. Governor is mounted on the aft side of the reduction gear housing, so fairly far forward as well. (red cover below)
gov mount.jpg

Finally, you could add an A/C compressor + backup generator to get another 10 lbs on the engine (although that would be mounted on the back of the engine).
pdr engine rear bigger.jpg
 
Intercooler too?

It looks like ones needs a radiator AND an intercooler too!

With the RV9A's VNE as True airspeed, it doesnt seem to make much sense to have more horsepower for high altitude cruising since the VNE limitations prevent using this extra horsepower.

Seems better for a clean sheet design, like a RV-15 lite, that can be designed for a higher cruise speed at altitude.
 
With the RV9A's VNE as True airspeed, it doesnt seem to make much sense to have more horsepower for high altitude cruising since the VNE limitations prevent using this extra horsepower.

Hush yo' mouf! Mo' power, mo' gooder :D (up to a point... settle down Scott)

When I cruise in the mid-upper teens I'm usually showing right at 150-152 knots true (running WOTLOP), and with a Vne of 182 knots true that leaves arguably 25 knots on the table for improvement. Fuel burn will be higher since I'm not running LOP on the turbo, but I might be perfectly willing to trade 2-3 gph in exchange for 25 knots.

While I am not considering removing my perfectly good IO360 to replace it with the 916is, I might think real hard about it when it's time for a full overhaul (I'm almost at 1300 now). If I just need to top it, I'll probably keep what I have. The cowling mods for cooling airflow will be interesting.
 
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Latest from Rotax - the 916iS

159hp for three minutes, then 137hp to 23,000ft service ceiling. A good match for an RV airframe in future?

Ed,
where are you getting that info. this is what I see on the link you attached. 0ne minute at 5800 rpm and one minute at 5500 rpm.

PERFORMANCE
117 kW 160 hp 5800 1/min
**101 kW 137 hp 5500 1/min

TORQUE
193 Nm 142 ft lb 5800 1/min
175 Nm 129 ft lb 5500 1/min

Engine performance may vary depending on, among other things, general conditions, ambient temperature and altitude.

* leaded, unleaded, AVGAS 100LL, Ethanol 10
** max. continuous power at 5500 1/min
 
Ed,
where are you getting that info. this is what I see on the link you attached. 0ne minute at 5800 rpm and one minute at 5500 rpm.

PERFORMANCE
117 kW 160 hp 5800 1/min
**101 kW 137 hp 5500 1/min

TORQUE
193 Nm 142 ft lb 5800 1/min
175 Nm 129 ft lb 5500 1/min

Engine performance may vary depending on, among other things, general conditions, ambient temperature and altitude.

* leaded, unleaded, AVGAS 100LL, Ethanol 10
** max. continuous power at 5500 1/min

I think the "1/min" is meaning "per minute" in this context, as in 5800 RPM, not as "for 1 minute".
 
I think the "1/min" is meaning "per minute" in this context, as in 5800 RPM, not as "for 1 minute".

Thanks, that is an interesting way to say RPM (1/min).

was trying to download the operator manual to see what limitations are imposed but no joy.
 
Hopefully it's permitted to operate at max takeoff power for more than a minute, that's not very long. Might get some airplanes to 400ft at best. I'd hate to see someone distracted by other traffic shortly after takeoff and leave the power till 1000ft by accident and that results in an engine limitation exceedance.
 
Ed,
where are you getting that info. this is what I see on the link you attached. 0ne minute at 5800 rpm and one minute at 5500 rpm.

PERFORMANCE
117 kW 160 hp 5800 1/min
**101 kW 137 hp 5500 1/min

TORQUE
193 Nm 142 ft lb 5800 1/min
175 Nm 129 ft lb 5500 1/min

Engine performance may vary depending on, among other things, general conditions, ambient temperature and altitude.

* leaded, unleaded, AVGAS 100LL, Ethanol 10
** max. continuous power at 5500 1/min

Hey Axel. It’s made clearer in the EASA certification documentation.

Max. continuous performance at sea level pressure altitude up to critical altitude of 23000 ft / 7010 m - 100kW 5,500rpm
Maximum certified Take-off performance rpm (max. 5 min at sea level pressure altitude - 117kW 5,800rpm
Normal Take-off performance rpm (max. 3 min.) at sea pressure altitude 117kW 5,800rpm
 

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Why is there two different time limits on the same power rating? Sure it's got slightly different names, but the 117kw is the same.
 
I'm confused about a "normal takeoff" and a "max takeoff"

Hot day, loaded to max weight and there's lots of traffic around to see and avoid. Rolling down the runway, 3 minute timer started, get to 3 minutes and still want some vertical seperation from one other plane. "Oops, I guess this is a max takeoff now", and let the timer run until 5 minutes?

My only experience with normal power takeoffs and max power takeoffs is in twins and the different power rating is only applicable after an engine failure. Either more power, or a longer time limit on take-off power when the other engine has failed. I hardly think that was Rotax's intent when making an engine for the single engine market
 
How long do you typically keep running 2700 rpm after a takeoff before pulling it back?

Then the engine won't ever have a limitation for takeoff. no way to get to 5800rpm, unless you have a constant speed prop or the prop is pitched incorrectly.
 
Sea level PA doesn't mean much to a turbo engine since the engine is capable of making max MAP until critical altitude. Interesting that Rotax would even state it that way.

Most turbo engines state TO, Climb and MCP power with RPM/ MAP limits.

Seems like they don't want it at over 5500 rpm for more than 5 minutes.
 
I'm confused about a "normal takeoff" and a "max takeoff"

I understood it to mean "normal time at takeoff power" and "max time at takeoff power". In other words: Normally you pull the power back after about 3 minutes after you push the throttle all the way in, and you must pull the power back before 5 minutes.
 
I hardly think that was Rotax's intent when making an engine for the single engine market

There's the Tecnam Rotax powered twin (P2006T), and the Aircam, there might be others... The Tecnam is certified, Aircam is experimental, so it wouldn't be out of line for Rotax to appeal to current and future twin designs for the 916.
 
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