Kitfox 7/Rotax 914 Performance Questions

Well folks, I hope I'm not opening up a can of worms on this. I searched
the usenet archives on google about this, and nothing quite answered my
question, so...

I emailed Skystar, but want to ask here too.

The kit manufacturer claims a 150mph cruise and 160mph top speed. This
seems a little optimistic. This is a side-by-side 2 seater, 100-115hp
engine (turbo maintains output to 16,000 feet), approx 1500lbs gross weight
(about 750 empty). The 100hp normally aspirated engines list 120 and 125mph
for cruise and max respectively. So it doesn't quite add up...

Has anyone backed this up in practice?

I did some rough calculations on scratch paper. The short answer is it
_might_ be possible. Taking into account the turbo engine's higher output
at high altitude, and that the non-turbo aircraft probably max out TAS at
about 5,000ft compared to over 10,000 for the turbo, air density's effect on
profile drag vs induced drag, air density effect on the normally aspirated
engines... Again, my best answer is... maybe.


Thanks for any help.

That's about what the Wittman Tailwind does with 100 hp.
It too is a side by side high wing - with a wing strut.



Jim Carriere wrote:

Well folks, I hope I'm not opening up a can of worms on this. I searched
the usenet archives on google about this, and nothing quite answered my
question, so...

I emailed Skystar, but want to ask here too.

The kit manufacturer claims a 150mph cruise and 160mph top speed. This
seems a little optimistic. This is a side-by-side 2 seater, 100-115hp
engine (turbo maintains output to 16,000 feet), approx 1500lbs gross weight
(about 750 empty). The 100hp normally aspirated engines list 120 and 125mph
for cruise and max respectively. So it doesn't quite add up...

Has anyone backed this up in practice?

I did some rough calculations on scratch paper. The short answer is it
_might_ be possible. Taking into account the turbo engine's higher output
at high altitude, and that the non-turbo aircraft probably max out TAS at
about 5,000ft compared to over 10,000 for the turbo, air density's effect on
profile drag vs induced drag, air density effect on the normally aspirated
engines... Again, my best answer is... maybe.

Thanks for any help.

Jim Carriere wrote:

Well folks, I hope I'm not opening up a can of worms on this. I searched
the usenet archives on google about this, and nothing quite answered my
question, so...

I emailed Skystar, but want to ask here too.

The kit manufacturer claims a 150mph cruise and 160mph top speed. This
seems a little optimistic. This is a side-by-side 2 seater, 100-115hp
engine (turbo maintains output to 16,000 feet), approx 1500lbs gross weight
(about 750 empty). The 100hp normally aspirated engines list 120 and 125mph
for cruise and max respectively. So it doesn't quite add up...

Has anyone backed this up in practice?

I did some rough calculations on scratch paper. The short answer is it
_might_ be possible. Taking into account the turbo engine's higher output
at high altitude, and that the non-turbo aircraft probably max out TAS at
about 5,000ft compared to over 10,000 for the turbo, air density's effect on
profile drag vs induced drag, air density effect on the normally aspirated
engines... Again, my best answer is... maybe.


Thanks for any help.




Yep, 150mph is possible in a KitFox. I've got one. You've gotta' go
high to get the TAS up there, but with the turbo is doable. (I've got a
turbo, but not flying yet). The SkyStar demo ship put up those numbers
on the way to Sun N Fun. Other turbo drivers report about the same
thing. Down low though, you're TAS will be in the 130+ mph range.

Hope this helps,

Ron
KitFox Series 6, NSI turbo, CAP 140


--
************************************************** ********

Ronald K. Stevens

The MITRE Corporation
Center For Advanced Aviation System Development (CAASD)
Air-Ground Simulation Development
7515 Colshire Drive M/S N420
McLean, VA 22102-7508

http://www.caasd.org
Voice: 703-883-6629
Fax: 703-883-1917



************************************************** ********