Performance numbers question

Model Specific Discussions about the Sling TSi.
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okent
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Performance numbers question

Post by okent »

Is there a performance table for the TSi at different altitudes?
I'm looking to see what the plane will do at cruise and max continuous power at different altitudes(not in the 02 required levels)

Thanks
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ibgarrett
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Re: Performance numbers question

Post by ibgarrett »

I recently write a blog post about this which will help some at https://www.briangarrett.net/the-first-rivet. The performance is only based on HP, not actual real-world observations.

Basically because of the turbo you will maintain full HP all the way up to 15k/16k (depending upon whose reference you look at) and then it'll start falling off at about 3% for every thousand feet.

Let me know if you have any questions.
Brian Garrett
ncs
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Re: Performance numbers question

Post by ncs »

I had a similar line of reasoning as your post since I am also in an area with high field elevations (8,000' DA can be seen during taxi much less cruise). I compared power loading at gross weight vs altitude rather than just straight hp because of the weight difference you point out. At takeoff power the TSi matches the -10 at about 10,000' (11,000' for continuous power). Sure this doesn't take into account the different airframes, but I think the graph provides a good depiction of where the TSi's strength lies.
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ibgarrett
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Re: Performance numbers question

Post by ibgarrett »

My math mojo just isn't strong enough to take into account the weight differences between the RV10 and the SlingTsi. 600lbs and only a 30hp difference seems like the Tsi should be able to be ahead of the RV10.

I do try to stress the RV10 is a solid airplane and probably has the edge over the Tsi overall, but much like the objects in the mirror are much closer than they seem.
Brian Garrett
okent
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Location: Tulsa- CTLSi

Re: Performance numbers question

Post by okent »

ibgarrett wrote: Wed Feb 24, 2021 10:23 am My math mojo just isn't strong enough to take into account the weight differences between the RV10 and the SlingTsi. 600lbs and only a 30hp difference seems like the Tsi should be able to be ahead of the RV10.

I do try to stress the RV10 is a solid airplane and probably has the edge over the Tsi overall, but much like the objects in the mirror are much closer than they seem.
Thanks for that link, very helpful. I noticed that you listed KTAS vs KIAS for the performance numbers at 8K and 16K on the Experimental Efficiency Comparison. Would the TSi numbers be higher with the increase in altitude? I figure a 2% increase in true air speed per 1K altitude so the TSi should be higher as ncs referenced.

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ibgarrett
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Re: Performance numbers question

Post by ibgarrett »

I definitely spent a lot of time trying to get some hard numbers for what kind of performance people would see in the Tsi at altitude. When you chat w/ the guys at TAF there's a rumor floating around that there was a head to head competition between the Tsi and the RV10. Below 10k feet the RV10 was the clear winner, but higher, the Tsi apparently was gaining a lot of ground. When asked about it being published there's a lot of himming and hawing about it. I'm not really sure what the deal is there.

I went with TAS simply because math and I aren't the best of friends and I'd hate to put something out there wildly wrong. So when I posted my blog post I tried to be as honest with the numbers as possible. Boldmethod did the 4 types of airspeed at https://www.boldmethod.com/blog/lists/2 ... ach-works/ and under point number 2, they do reference the same information you have of "So at 10,000 feet, true airspeed is roughly 20% faster than what you read off your airspeed indicator." Another good reference (which I used the slide in my blog post) is at https://youtu.be/p22FOawoTCM?t=694, and I've come to find the videos that Savvy does to be very informative. A bit dry, but still the material is good.

I also stumbled across this video of an RV10 driver who was demonstrating his LOP to FL200, which is kinda cool, but I was watching it mostly for the airspeeds he was getting not so much his fuel consumption. If you look at this frame https://youtu.be/FgXH-1VJl44?t=342, he's at 16k with a 39kt tail wind with a TAS of 152ks and GS of 196kts. Then if you go to https://youtu.be/FgXH-1VJl44?t=347 which is a bit later in the flight, he's at 18k with a 46kt right x-wind showing 156KT True and 160kt GS. His engine is down to 15.5" on the manifold, so he's way off his full power, or even 75% power.

The FL300 flight test they did in the SlingTsi (two people, more differences in weight of course) doesn't have any good up close panel pictures, but from this frame https://youtu.be/Yn9PU-crXYw?t=576 they are at FL160 with a GS of 141kts and still climbing at 768FPM. The next point of reference they are at FL250 and I'm not even gonna pretend I'm ever going to fly that high in the Sling.

Bottom line is (for me) I certainly want to go as fast as possible (and try really really hard to not be smug about it), but at the end of the day, this is the plane I'm building and planning on keeping for a long while, so whatever it trues out to will be fine. But the meager math I've done seems to suggest that with O2 it will be able to be pretty zippy in the FL150/160 range...

If I'm missing something, or need to correct my thinking on any of this, by all means, please let me know. I'd much rather be corrected than wander around wrong all the time as that's just embarrassing. :)
Brian Garrett
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