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Guy Buchanan
Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA
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 Posted: Thu Feb 21, 2008 8:02 pm Post subject: rotax 912UL |
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At 12:29 PM 2/21/2008, you wrote:
| Quote: | From what I understand, I can fly a little bit faster than 100 MPH,
my Vne, without much risk.
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Time to kick the hornets nest.
Theoretically, and yes, I mean theoretically, flying around
at Vne is a VERY dangerous thing to do. It means you have 0 (zero)
available gust factor and quite literally any wind shear, gust,
whatever, will rip your wings off. Vno, which for my IV is 99mph,
(Vne = 120mph,) is the top of the green arc, where you can fly around
in most turbulence without much worry. Vno accommodates a 3-sigma
gust, (99.7% unlikely,) without damage to the airframe. As you
increase speed from Vno to Vne you whittle at the available gust
factor until at Vne it reaches zero.
Now is this true for Kitfoxes? It seems hardly likely since
nearly everyone I know cruises their IV at well over 100mph, and
there are some that cruise over Vne. (I think I was told the world
record cruise for a IV was 132mph, though that might have been top
speed.) Certainly no one has ever shed a wing or even experienced
flutter, so it appears that our Vne is highly conjectural. If that's
the case then who knows what Vno really is, or Va for that matter
since it can be assumed that the structure can stand a lot more than
3.8g's. However rest assured that when you fly around at or above
Vne, YOU ARE A TEST PILOT. (Michel, I admire your courage.)
Guy Buchanan
San Diego, CA
K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.
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_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too. |
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bigboyzt0yz
Joined: 29 Jan 2008
Posts: 29
Location: Centeral Maryland
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| Posted: Fri Feb 22, 2008 2:14 pm Post subject: Re: rotax 912UL |
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I was having the same issue with the RPM not getting to 5K. I fooled with it (one whole day) moving the pitch down till I got to 11 Deg. and it now works just great. The Plane comes right off the ground and climbs at 1150 FPM and with 2 it is right around 1000 FPM.
My friend Ray has a IV but his has a 912 ULS and it has 16 Deg. in the same Warp Drive prop. His is not as loud as mine upon take off. It was kinda the reason that I was looking (another thread) to move up from the 912 ULS that was before I joined the list.
My ground RPM did start coming up till I got closer to the 11 deg number and now it is just great. The past owner had the pitch at 20 and it is a good thing that he never tried to fly it cause it would have needed 5K worth of runway and no trees at the end.
It has a good cruise at around 115 / 1500 feet MSL /4900 RPM this past Sunday.
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_________________
Lee Fritz in Owings Mills Md. 2002 KitFox-IV Classic/912UL/Warp drive taper tip/100% Complete ( Extras Strut fairings08, Grove gear09,) 300 hrs since Aug 07 "Have your feet on the Pedals and keep reaching for the sky". |
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dave
Joined: 22 Sep 2006
Posts: 1382
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Guy Buchanan
Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA
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| Posted: Sun Feb 24, 2008 8:39 am Post subject: rotax 912UL |
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At 05:30 AM 2/24/2008, you wrote:
| Quote: | Where did you get that info?
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From one of the owner's friends at last year's Desert Fox Fly-in.
I'll follow up at this year's fly-in and report with more detail.
(Shameless plug for the Desert Fox Fly-in.)
| Quote: | I would bet that a faired IV with a 914 will see 140 to 150
mph + at over FL180 to the low FL200s.
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Now that's a novel idea. An IFR Kitfox with O2 in the flight levels.
I dunno, sounds kinda wierd. But I suspect you're right about the
true airspeed.
| Quote: | a IV with a 912 UL will see mid 120s or better at low altitude.
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Lowell used to cruise at 115 mph, if I recall. I don't know what his
top speed was. I know when I travel with the 912 fleet, I'm only
about 10 slower in cruise than they are, which puts them around 100 mph or so.
Guy Buchanan
San Diego, CA
K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.
| | - The Matronics Kitfox-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too. |
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MichaelGibbs(at)cox.net
Guest
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| Posted: Sun Feb 24, 2008 9:22 am Post subject: rotax 912UL |
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Guy sez:
| Quote: | Now that's a novel idea. An IFR Kitfox with O2 in the flight levels.
I dunno, sounds kinda wierd. But I suspect you're right about the
true airspeed.
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I threw the O2 bottle out of the Turbo Arrow in the back of my
912S-powered IV and took her up to 17,500 (density altitude 19,600)
one day. She was still climbing 300 feet per minute (measured, not
indicated) but leveled off she didn't really pick up much speed.
Unfortunately, I never figured out what my TAS was on that adventure.
At more reasonable altitudes she could hit 140 mph in level flight
(full power) and high-speed cruise was between 125 and 130. I
usually went a bit slower because it required about 5.5 gph to get
those numbers. She was a speedster with clipped wings, wheel pants,
gas cap fairings, streamlined horizontal stabilizer braces, lift
strut fairings, the Safari-style cowling and every other
drag-reducing device I could think of. She also had an Ivo medium
in-flight adjustable prop and was pretty light (660 pounds empty).
Mike G.
N728KF
Phoenix, AZ
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