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Kitfox IV Stall Speeds

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gentryll

Joined: 30 Jan 2011
Posts: 7

Posted: Sun Jan 30, 2011 3:13 pm Post subject: Kitfox IV Stall Speeds

I have a Model IV with a Subaru.  It is light for a Subaru at around 630 lbs. During initial testing I am getting power off and up to 2000 rpm, stall speeds of around 50 mph, and  with flaps around 45. I checked airspeed indicator against GPS and speeds are good. I was expecting a lot less.  I have about 38 lbs. on the tailwheel.  Is this normal or have I done something wrong.  I can still land and take off very short.  It just looks bad, when I can fly lower than my indicated stall speed.

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Sun Jan 30, 2011 3:50 pm Post subject: Kitfox IV Stall Speeds

On 1/30/2011 3:13 PM, gentryll wrote:

 	  Quote: 	
		   I checked airspeed indicator against GPS and speeds are good. I was expecting a lot less.  I have about 38 lbs. on the tailwheel.  Is this normal or have I done something wrong.

Hi,
	


     Moderator here again asking you to please include your full name, 

location, and aircraft type / status in your signature. It makes us much 

more friendly.

     Your stall speeds sound about right. I've got a IV with a 582 and 

it stalls 40/45 mph. Your engine is a lot heavier so I'd expect the 

stall to be higher. (My empty weight is about 620# and my CG is at the 

aft limit.)



Guy Buchanan - List moderator

Ramona, CA

Kitfox IV-1200 / 592-C / Warp 3cs / 500 hrs. and grounded

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

helili(at)chahtatushka.ne
Guest

Posted: Sun Jan 30, 2011 3:57 pm Post subject: Kitfox IV Stall Speeds

My KF-IV with a NSI Subaru and prop stalls at around 4o-45 mph indicated

clean.  I am sure that figure is incorrect because of the high angle of

attack, which causes some angular airflow across the pitot tube inlet rather

than directly into it, and the inherent inaccuracy of airspeed indicators at

low speeds.  Each airspeed indicator installation varies somewhat from

aircraft to aircraft.  Some of the variables are such things as where the

static port is located, whether static source is just cabin air and so on.

I have my static source, which is on the pitot tube, plumbed in to the

airspeed indicator, VSI, and transponder altitude encoder.  



John Hart 

KF-IV

Wilburton, OK 



--

lcfitt(at)sbcglobal.net
Guest

Posted: Sun Jan 30, 2011 5:10 pm Post subject: Kitfox IV Stall Speeds

My first Model IV stalled at 43.  That is indicated.  I think the mention of 

pitot tube angle might be an error producer - though I logic tells me that 

with an angled pitot, it would likely read low rather than high.  Did you do 

your AIS calibration at speed or in a slow flight configuration mimicking 

the angle you would find near stall?  I calibrated my ASI with a water 

manometer once and found that at 60 mph it was spot on, but fudged upward at 

high speeds - that allowed me to brag about my cruise speeds, and low at 

lower speeds giving the same bragging rights there as well.  Whatever the 

stall speed is, though, at 630 with an auto conversion, you most certainly 

did something right.



Lowell Fitt

Kitfox IV-1200 Gone West

Kitfox IV-1200 Close

Cameron Park, CA

--------------------------------------------------

From: "gentryll" <gentryll(at)aol.com>

Sent: Sunday, January 30, 2011 3:13 PM

To: <kitfox-list(at)matronics.com>

Subject: Kitfox IV Stall Speeds



 	  Quote: 	
		   



 I have a Model IV with a Subaru.  It is light for a Subaru at around 630 

 lbs. During initial testing I am getting power off and up to 2000 rpm, 

 stall speeds of around 50 mph, and  with flaps around 45. I checked 

 airspeed indicator against GPS and speeds are good. I was expecting a lot 

 less.  I have about 38 lbs. on the tailwheel.  Is this normal or have I 

 done something wrong.  I can still land and take off very short.  It just 

 looks bad, when I can fly lower than my indicated stall speed.





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=329022#329022

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Sun Jan 30, 2011 5:22 pm Post subject: Re: Kitfox IV Stall Speeds

My IV  empty  550 lbs.

stall  37 - 38 mph 



Check my  videos  I will post in a day or two  doing stalls

_________________
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http://www.youtube.com/user/kitfoxflyer
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Av8r3400

Joined: 22 Sep 2008
Posts: 83
Location: North Central Wisconsin (KRRL)

Posted: Sun Jan 30, 2011 6:27 pm Post subject: Re: Kitfox IV Stall Speeds

My IV-1050 is about 635# empty with a 912 on the nose.  Clean stall, solo with half fuel is indicated at ~42 mph, with flaps down around 37 mph.  Your forward CG may add some to your stall speed, along with ASI error.



But, 630# with a Subaru is just this side of a miracle!  That's great!  You did good!

_________________
Thanks,
Av8r3400

Kitfox Model IV-1200 W/912UL & IVO
Kitfox Model IV-1050 W/912UL & Warp
YouTube Videos

gentryll

Joined: 30 Jan 2011
Posts: 7

Posted: Sun Jan 30, 2011 7:11 pm Post subject: Re: Kitfox IV Stall Speeds

 	  gentryll wrote: 	
		  I have a Model IV with a Subaru.  It is light for a Subaru at around 630 lbs. During initial testing I am getting power off and up to 2000 rpm, stall speeds of around 50 mph, and  with flaps around 45. I checked airspeed indicator against GPS and speeds are good. I was expecting a lot less.  I have about 38 lbs. on the tailwheel.  Is this normal or have I done something wrong.  I can still land and take off very short.  It just looks bad, when I can fly lower than my indicated stall speed. 	




Thanks guys, that makes me feel better already.  The GPS corroborates my AIS so the speed is accurate.  I saw the numbers in the operating manual for a 582 and a 912 and noticed mine were much higher , and that made me worry.  Do you guys try to three point with power all the way off or keep it up a bit to keep some air moving across the elevators.  With the NSI gearbox at I think 2.27/1 ratio,  very little air from the prop is moving across the elevators at idle.

Larry Gentry

Kitfox IV

Crawford, ms.

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Sun Jan 30, 2011 11:19 pm Post subject: Kitfox IV Stall Speeds

On 1/30/2011 7:11 PM, gentryll wrote:

 	  Quote: 	
		   Do you guys try to three point with power all the way off or keep it up a bit to keep some air moving across the elevators.  With the NSI gearbox at I think 2.27/1 ratio,  very little air from the prop is moving across the elevators at idle.

    

Larry,
	


     Thanks for putting in the signature. It's much nicer calling you by 

name.

     I can three point full flaps at idle, but I had to gap seal the 

elevator to do it. Otherwise I was limited to partial flaps, three 

point, at idle. Of course, I rarely three point anymore. 



Guy Buchanan

Ramona, CA

Kitfox IV-1200 / 592-C / Warp 3cs / 500 hrs. and grounded

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Mon Jan 31, 2011 1:39 am Post subject: Re: Kitfox IV Stall Speeds

Power off stall  -- no flaps  video 

http://www.youtube.com/watch?v=XcAUa5DjxuE



I would not depend on ASI to give accurate stall speed. 

I know by GPS mine is 37 to 38  mph.



1/2 Flaps will cut it by about 1 - 2 mph, if that.



This Kitfox has Vgs which makes the stall almost just a mush.



Enjoy.

Tom Jones

Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

Posted: Mon Jan 31, 2011 5:52 am Post subject: Re: Kitfox IV Stall Speeds

Classic 4.  Gross weight 795 pounds stall full flaps = 36 MPH, Clean = 38 MPH.  Gross weight 1050 stall full flaps 42 MPH, Clean = 46 MPH.



 	  Quote: 	
		  Do you guys try to three point with power all the way off or keep it up a bit to keep some air moving across the elevators. 	




Power off three point full stall landing.  http://vimeo.com/12693781

_________________
Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA

Fox5flyer
Guest

Posted: Mon Jan 31, 2011 9:35 am Post subject: Re: Kitfox IV Stall Speeds

That is a very light IV/Soob so you must have been paying very close attention to weight during building.  Good job.  As for the stall speeds, I wouldn't worry too much about what the AS reads as they can be very inaccurate at lower speeds.  Also, comparing it with the GPS is not very helpful as AS reads airspeed and GPS reads ground speed which means that they are rarely the same when flying.  You will hear stall speeds all over the map with some way too low to believe and many others close to what yours is.  The thing to remember is to just know what your AS reads at stall and don't worry about how accurate it is.  The number is all that really matters.

Good luck,

Deke Morisse

S5/NSI/500TT

NE Michigan

 	  gentryll wrote: 	
		  I have a Model IV with a Subaru.  It is light for a Subaru at around 630 lbs. During initial testing I am getting power off and up to 2000 rpm, stall speeds of around 50 mph, and  with flaps around 45. I checked airspeed indicator against GPS and speeds are good. I was expecting a lot less.  I have about 38 lbs. on the tailwheel.  Is this normal or have I done something wrong.  I can still land and take off very short.  It just looks bad, when I can fly lower than my indicated stall speed.

Fox5flyer
Guest

Posted: Mon Jan 31, 2011 9:42 am Post subject: Re: Kitfox IV Stall Speeds

 	  gentryll wrote: 	
		   	  gentryll wrote: 	
		  I have a Model IV with a Subaru.  It is light for a Subaru at around 630 lbs. During initial testing I am getting power off and up to 2000 rpm, stall speeds of around 50 mph, and  with flaps around 45. I checked airspeed indicator against GPS and speeds are good. I was expecting a lot less.  I have about 38 lbs. on the tailwheel.  Is this normal or have I done something wrong.  I can still land and take off very short.  It just looks bad, when I can fly lower than my indicated stall speed. 	




Thanks guys, that makes me feel better already.  The GPS corroborates my AIS so the speed is accurate.  I saw the numbers in the operating manual for a 582 and a 912 and noticed mine were much higher , and that made me worry.  Do you guys try to three point with power all the way off or keep it up a bit to keep some air moving across the elevators.  With the NSI gearbox at I think 2.27/1 ratio,  very little air from the prop is moving across the elevators at idle.

Larry Gentry

Kitfox IV

Crawford, ms. 	




Do you have your battery in the rear above the tailwheel?  The Soob is heavy and unless you added some sort of ballast it is pretty much necessary to put the battery there to keep the CG far enough back to make a decent tail wheel landing.

Deke Morisse

S5/NSI Soob /500TT

NE Michigan

Big snow on the way

Lynn Matteson

Joined: 10 Jan 2006
Posts: 2778
Location: Grass Lake, Michigan

Posted: Mon Jan 31, 2011 2:55 pm Post subject: Kitfox IV Stall Speeds

That's so good I would suspect the scales....and I'm only half  

kidding. This is based on my Jabiru-powered IV weighing in at  

650....with calibrated aircraft scales.



Lynn Matteson

Kitfox IV Speedster, taildragger

Jabiru 2200, #2062

Sensenich 62"x 55.5 Wood (winter) until the Prince prop arrives

Electroair direct-fire ignition system

Rotec TBI-40 injection

Status: flying...1081 hrs (since 3-27-2006)



On Jan 30, 2011, at 9:27 PM, Av8r3400 wrote:



 	  Quote: 	
		   




	


    (snip)



 	  Quote: 	
		   But, 630# with a Subaru is just this side of a miracle!  That's  

 great!  You did good!



 --------

 Thanks,

 Av8r3400



 Kitfox Model IV-1200 W/912UL &amp; IVO

 Kitfox Model IV-1050 W/912UL &amp; Warp

_________________
Lynn
Kitfox IV-Jabiru 2200
N369LM

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