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Cruise vs. Vne speed

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Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Mon Feb 27, 2006 12:50 am Post subject: Cruise vs. Vne speed

Hello guys,

On the Jabiru Engines list, someone was comparing the cruise speed of different Kitfoxes and I was surprised to see someone with a model 2 saying that he cruises at 122 MPH. 

I have a model 3 and while I believe I can reach 122 MPH at WOT, my POH says that 100 MPH is Vne, and I respect that. Could it be that the model 2 has a higher Vne that the model 3?



While on the subject of speed, I was wondering when you, guys, decide to slow down to Va, due to turbulence. I know the theory but ... how bad the turbulence must be for you to slow down?



Cheers,

Michel

_________________
Kitfox 3 - Jabiru 2200

Graeme Toft

Joined: 09 Jan 2006
Posts: 123

Posted: Mon Feb 27, 2006 2:07 am Post subject: Cruise vs. Vne speed

Hi Michel, I have always backed off in turbulence because of the real 

possibility of exceeding VNE very quickly, in fact excessive speed can occur 

so fast that even in mild conditions I tend to find myself flying with my 

hand on the throttle. Here in Queensland most of our turbulence is created 

by heat with very little mechanical effect due to a relatively flattish 

terrain. At times the thermals are so active you can be in a descending 

attitude but ascending at over 1500 ft a minute, then as you come out of the 

thermal you will enter another that is descending equally as fast. I like to 

keep at least 20 knots between VNE and cruise as a safety margin in these 

conditions. The figures on the Model 2 in my humble opinion are pushing the 

limit.



Cheers

Graeme Toft

Queensland Safety Solutions

Ph: 07 49397011

Mob: 0411476527

---

jdmcbean(at)cableone.net
Guest

Posted: Mon Feb 27, 2006 10:06 am Post subject: Cruise vs. Vne speed

Michel,

	The Vne is 100 mph on the 2 and the 3.  I doubt what was being said is the

truth.. There are not that many Fox's cruising around at 122 mph and the

ones that are, have the flatter bottom wing not the high under camber. You

can visit the about Kitfox page on our web

http://sportplanellc.com/about_kitfox.htm regarding the Vne.



As for Va... follow your comfort level if it feels like you should be slower

then slow down... I think you'll find that above mild turbulence in the

Kitfox usually does the trick and you'll slow down.  If there is a lot of

gusty type turbulence (gust loads) it is a good idea to be at Va.



Fly Safe !!

John McBean

www.sportplanellc.com

"The Sky is not the Limit...  It's a Playground"



--

spaghettiohead(at)hotmail
Guest

Posted: Mon Feb 27, 2006 10:49 am Post subject: Cruise vs. Vne speed

I doubt that the Model 2 is cruising at 122...what's he got for a 

powerplant?



My Model 3 with the 582 doesn't cruise over 80 at WOT, but normal cruise is 

65-70. And what would Va be in our earlier models?



Also, it's amazing how quickly the 'Fox picks up speed - in a power-off dive 

she'll hit 100 in about 3 seconds!



Andrew

[quote]From: "Graeme Toft" <msm(at)byterocky.net>

Reply-To: kitfox-list(at)matronics.com

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

Subject: Re: Cruise vs. Vne speed

Date: Mon, 27 Feb 2006 20:02:04 +1000






Hi Michel, I have always backed off in turbulence because of the real

possibility of exceeding VNE very quickly, in fact excessive speed can 

occur

so fast that even in mild conditions I tend to find myself flying with my

hand on the throttle. Here in Queensland most of our turbulence is created

by heat with very little mechanical effect due to a relatively flattish

terrain. At times the thermals are so active you can be in a descending

attitude but ascending at over 1500 ft a minute, then as you come out of 

the

thermal you will enter another that is descending equally as fast. I like 

to

keep at least 20 knots between VNE and cruise as a safety margin in these

conditions. The figures on the Model 2 in my humble opinion are pushing the

limit.



Cheers

Graeme Toft

Queensland Safety Solutions

Ph: 07 49397011

Mob: 0411476527

---

Rex Hefferan

Joined: 10 Jan 2006
Posts: 147
Location: Olney Springs, Colorado USA "NOT a Kitpig"

Posted: Mon Feb 27, 2006 11:39 am Post subject: Cruise vs. Vne speed

Hi Michel,

 No the Vne has risen with some newer models of Kitfox, never fallen. 

Standard Model 2 Vne is also 100 MPH. If someone properly modified their 

Model 2 it's possible they might safely operate at a higher Vne, but I 

wouldn't know about that.



Rex

M2 - N740GP

Colorado

Michel Verheughe wrote:



 	  Quote: 	
		  



Hello guys,

On the Jabiru Engines list, someone was comparing the cruise speed of different Kitfoxes and I was surprised to see someone with a model 2 saying that he cruises at 122 MPH. 

I have a model 3 and while I believe I can reach 122 MPH at WOT, my POH says that 100 MPH is Vne, and I respect that. Could it be that the model 2 has a higher Vne that the model 3?



While on the subject of speed, I was wondering when you, guys, decide to slow down to Va, due to turbulence. I know the theory but ... how bad the turbulence must be for you to slow down?



Cheers,

Michel



 

 

 





  




	


-- 

Karla and Rex Hefferan

Gypsy Bee Innkeepers

719-651-5198 or 719-651-9192

_________________
Rex
N740GP - M2/582
Colorado

roncarolnikko(at)hotmail.
Guest

Posted: Mon Feb 27, 2006 11:39 am Post subject: Cruise vs. Vne speed

Hi michel.  I have an early model Avid Flyer and one of the differances that 

keeps it's VNE slow is the .060 windscreen.  At 100 MPH it is pushing in 

more than the .090 thick windscreen.  With the .090 windscreen it could be 

somewhere near 135.

    Ron NB Ore

 	  Quote: 	
		  From: Michel Verheughe <michel(at)online.no>

Reply-To: kitfox-list(at)matronics.com

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

Subject: Cruise vs. Vne speed

Date: Mon, 27 Feb 2006 09:46:12 +0100 (CET)






Hello guys,

On the Jabiru Engines list, someone was comparing the cruise speed of 

different Kitfoxes and I was surprised to see someone with a model 2 saying 

that he cruises at 122 MPH.

I have a model 3 and while I believe I can reach 122 MPH at WOT, my POH 

says that 100 MPH is Vne, and I respect that. Could it be that the model 2 

has a higher Vne that the model 3?



While on the subject of speed, I was wondering when you, guys, decide to 

slow down to Va, due to turbulence. I know the theory but ... how bad the 

turbulence must be for you to slow down?



Cheers,

Michel

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Mon Feb 27, 2006 2:03 pm Post subject: Cruise vs. Vne speed

Thank you, Graeme, Jim, Andrew, Ron and Rex, for your answers.



For the cruise speed, on the Jabiru list, someone was asking for the 

performance of a Jabiru 2200 (that's your answer, Andrew) on a draggy 

plane similar to a Kitfox or Avid Flyer. Several answered and the 

person was puzzled that it may vary from 80 MPH (my cruise speed) to 

122 MPH (one reported by  a friend Kitfox 2 owner). I agree with you, 

it must be exaggerated or, the owner has a special model 2 and likes 

fast cruising! 



For the Va speed, I understand that it is a matter of comfort and that, 

when in turbulent air, Vne is quickly exceeded as both vertical and 

indicated speed needles move fast in all directions. But, I remember 

that I once sailed into a French harbour to hear French yachtsmen who 

had just arrived before me, talking about sailing in a storm ... when I 

would have called it a moderate gale. It's all in the observator's eye.

As a novice pilot, any turbulence is a bit scary and I was wondering 

what is real bad stuff that needs to stay at Va to avoid structural 

damages. Do I have to loose my denture, wig and glass eye, to call it 

significant turbulence? So far, the worse I have experienced is a short 

moment when I felt my feet lifted from the floor ... it must have been 

negative Gs. Is that "bad turbulence" or ... "moderate gale?"



I also like Rod Machado's saying: "Turbulence are like waves at sea, 

only that you don't see them ... and that's what horror movies are made 

of!"  



Cheers,

Michel



do not archive

_________________
Kitfox 3 - Jabiru 2200

jdmcbean(at)cableone.net
Guest

Posted: Mon Feb 27, 2006 5:05 pm Post subject: Cruise vs. Vne speed

Michel,

	Describing turbulence is very difficult..



One pilot's light chop is another's moderate-to-severe. Perception varies

with aircraft weight, type, and speed. A large, heavy, fast plane with high

wing loading has inertia in its corner and will be less disturbed by a given

bump than will a small, slow, lightly laden machine.

According to the AIM, if occupants feel a slight strain against their seat

belts and there is a slight, erratic change in aircraft altitude or

attitude, it is "light" turbulence. But what might be light turbulence to

the pilots of a 747 could be moderate to severe to the occupants of a

four-place single, who might feel definite strains against their seat belts

and have loose objects dislodged (moderate), or who may be forced violently

against their belts and experience large, abrupt changes in aircraft

altitude or attitude.

Turbulence may also be reported as occasional, intermittent, or continuous,

corresponding to less than 1/3, more than 1/3, or more than 2/3 of the time.

Turbulence also comes in two reportable varieties: Normal turbulence is a

dose of the shakes; chop is bumpy and rhythmic, akin to a speedboat skimming

across a rough lake. UDDF is a corollary comment, standing for "strong

up-and-down drafts." Make it quantitative if you must: "2000 FPM UDDF."

The definition according to the Aeronautical Information Manual.. AIM 7-1-24

Light: 	Turbulence that momentarily causes slight, erratic changes in

altitude and/or attitude (pitch, roll, yaw). Report as Light Turbulence or

Turbulence that causes slight, rapid and somewhat rhythmic bumpiness without

appreciable changes in altitude or attitude. Report as Light Chop.

Occupants may feel a slight strain against seat belts or shoulder straps.

Unsecured objects may be displaced slightly. Food service may be conducted

and little or no difficulty is encountered in walking.

Moderate:	Turbulence that is similar to Light Turbulence but of greater

intensity. Changes in altitude and/or attitude occur but the aircraft

remains in positive control at all times. It usually causes variations in

indicated airspeed. Report as Moderate Turbulence or Turbulence that is

similar to Light Chop but of greater intensity. It causes rapid bumps or

jolts without appreciable changes in aircraft altitude or attitude. Report

as Moderate Chop.

	Occupants feel definite strains against seat belts or shoulder straps.

Unsecured objects are dislodged. Food service and walking are difficult.

(Walking not an option in a Fox)

Severe:	Turbulence that causes large, abrupt changes in altitude and/or

attitude. It usually causes large variations in indicated airspeed. Aircraft

may be momentarily out of control. Report as Severe Turbulence.

	Occupants are forced violently against seat belts or shoulder straps.

Unsecured objects are tossed about. Food Service and walking are impossible.

Extreme:	Turbulence in which the aircraft is violently tossed about and is

practically impossible to control. It may cause structural damage. Report as

Extreme Turbulence.

High level turbulence (normally above 15,000 feet ASL) not associated with

cumuliform cloudiness, including thunderstorms, should be reported as CAT

(clear air turbulence) preceded by the appropriate intensity, or light or

moderate chop.

Fly Safe !!

John & Debra McBean

www.sportplanellc.com

"The Sky is not the Limit...  It's a Playground"



--

dcaofak(at)acsalaska.net
Guest

Posted: Mon Feb 27, 2006 5:31 pm Post subject: Cruise vs. Vne speed

I believe there is a Vne issue with the model III and earlier Kitfoxes because the wings are not rib stitched.

I have some memory (?) of there being something from the FAA limiting Vne to 100 mph if the fabric on the wings is only held with glue.

John Stoner

KFIII, 582

Alaska

bmwebb(at)cox.net
Guest

Posted: Mon Feb 27, 2006 6:46 pm Post subject: Cruise vs. Vne speed

Skystar SB'd the Model 2 to 90mph, due to a couple flutter incidents. I

think this was raised to 100 once the dual counter-weights are installed.

Bradley



--

lcfitt(at)sbcglobal.net
Guest

Posted: Mon Feb 27, 2006 7:53 pm Post subject: Cruise vs. Vne speed

Hi, John,



It has been always my understanding that the VNE in the earlier Kitfoxes was 

at least in part a windsheld issue.  I have a model IV and the VNE is 125 

mph.  I believe that the Speedster - thicker windshield with clipped wings 

has a VNE of 135 mph.  Rib stitching was not part of  my building 

instructions, but due to list influence, I did rib stitch mine.  The one 

inch capstrips are pretty unique to our class of airplanes and the factory 

determined that with those wide capstrips rib stitching was not necessary. 

There have been tons of discussion on the list and opinions on ribstitching 

are many.  In fact the subject of false ribs have come up on the list lately 

and brought up a question of my own.



Has anyone rib stitched the false ribs - the upper ones most specifically. 

I did not.



Also when replacing my windshield, I stuck with the thin lexan.  It does 

move a bit getting close to VNE, but I have seen it so much that It really 

doesn't bother me.  I must have had 500 hours on the original and changed it 

out because I finally got tired of looking at a big scratch I put on it 

while building.  Also the thinner Lexan is a bit more flexible - obviously - 

and moves around the top corner a bit easier.



Lowell



---

jopatco(at)mindspring.com
Guest

Posted: Tue Feb 28, 2006 6:04 am Post subject: Cruise vs. Vne speed

150 mph is glued on one inch cap strips.I;ve been over 140 mph and still

here.

 	  Quote: 	
		   [Original Message]

 From: dcaofak <dcaofak(at)acsalaska.net>

 To: <Kitfox-List(at)matronics.com>

 Date: 2/27/2006 6:41:32 PM

 Subject: Re: Cruise vs. Vne speed



 



 I believe there is a Vne issue with the model III and earlier Kitfoxes

because the wings are not rib stitched.
	


 	  Quote: 	
		   I have some memory (?) of there being something from the FAA limiting Vne

to 100 mph if the fabric on the wings is only held with glue.
	


 	  Quote: 	
		   John Stoner

 KFIII, 582

 Alaska

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Tue Feb 28, 2006 7:39 am Post subject: Re: Cruise vs. Vne speed

I've been following this thread with interest because I've always felt that it was strange how close 75% cruise is to to Vne on my airplane. According to Rotax, setting the manifold pressure to 27 inches then pitching the IVO prop for 5200 rpm constitutes 75%. At that setting, I'm pushing about 115mph. That's only 10mph short of Vne. All I have to do is lean forward a little to get a closer look at my chart to pitch the nose down enough to blow past Vne. Is this something that I should be worried about? Should I keep the speeds down until I have a better feel for keeping the airspeed constant?



-Luis

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