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FireFly CofG

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johngilpin

Joined: 23 Mar 2011
Posts: 93
Location: 004

Posted: Mon Jan 30, 2012 3:02 am Post subject: FireFly CofG

I've been searching the archives for info regarding the CofG of FireFlys.  All seem to end up pretty near the specified aft limit, but then it's a pretty mixed message, some quite comfortable with the CofG right back there, and some finding that they needed to carry weight in the nose for comfortable handling....  



I'm inquiring because I've bought a FireFly that's waiting for me in Mississippi (I'm coming over from Australia in March to start to fly it.).  I note that it has a 447 with C-box, clutch, and three-blade prop, and I only weigh about 160lbs, so it sounds like it'll be right back at the specified limit, if not even farther aft....  I've done enough flight testing in other aircraft to know not to believe all manufacturers numbers, and not even necessarily conventional 'wisdom'.  It's actual performance, as determined by real life flight time, that really tells the story.



Is there anyone who has experience with this combo on the FireFly??   



The reason I ask now before flying it, is that I have a spare B-box here that I can bring along if it would turn out to be necessary to swap it.....



JG

zeprep251(at)aol.com
Guest

Posted: Mon Jan 30, 2012 3:39 pm Post subject: FireFly CofG

JG.

 Have you ever ridden a small boat over the wake of another boat?That's the feeling I experience in a Kolb in rough air if it is aft cg wise.A quick pitch up, then back to aerodynamic neutral,You can fly it,you can land it slightly aft,it just FEELS so much more stable if it.s closer to the center.Wear your lead soled shoes or bite the bullet and stick some weight up front,maybe a storage compartment in the nose cone where you can keep a heavy lunch.

 G.Aman MK3C Jabiru 2200A 670hrs currently in Lakeland FL

    

  

     

  

     

  

    --

johngilpin

Joined: 23 Mar 2011
Posts: 93
Location: 004

Posted: Wed Feb 01, 2012 3:00 am Post subject: FireFly CofG

 	  Quote: 	
		  >stick some weight up front, maybe a storage compartment in the nose cone where you can keep a heavy lunch.

 

Good idea. I really don't like to carry lead, but food and water is good.  In the remote areas that I like to fly I always like to carry plenty of water anyhow.  So I could live with a couple of water bags and some canned food right in the nose... If there's room....

 

My main concern is that a high thrust line pusher is a real trap for aft CofG.  The prop thrust gives a nose-down moment, balancing the nose-up moment of the aft CofG, making it all balance well, until the engine stops........ and then that high thrust line suddenly becomes a high drag line, and then both the high drag line and the aft CofG nose-up moments are summed.  At the same time the elevator authority is much reduced by the lack of prop blast.  Kolb flyers know this from experience, and some have learned the h-a-r-d way.....  I've had a couple of off-list emails strongly cautioning me to keep power on right to touch-down, and I take that advice seriously.  I'm used to always pulling power at base leg and glide approach all the way to touchdown, but certainly won't be doing that in the FireFly, at least in the beginning.  But still need to practice dead stick landings just in case..... 

 [b] 	  Quote: 	
		  [b] 	  Quote: 	
		  

 	  Quote: 	
		  Not sure of his plans after the tour.


	


	
	
[/b]I think the costs and hassles wouldn't be worth it to ship it to Aus.  And besides, I don't have to be restricted to the Cat-103 over here, so can have two seats, and more range.....

  	
[/b]

  [quote][b]

pj.ladd(at)btinternet.com
Guest

Posted: Wed Feb 01, 2012 3:19 am Post subject: FireFly CofG

I'm used to always pulling power at base leg and glide approach all the way  to touchdown,>>

  

 If the C of g is anywhere close to where it should  be thats fine.  I always use a trickle of power  on the approach and  close the throttle on finals in my Xtra.

  

 The effect of the high thrust line is exaggerated  in my opinion. You just deal with it automatically .

  

 From Oz?.  Why don`t you buy a Thruster? Good  with a 503. Better with a Jabiru.

  

 Pat

   [quote][b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Wed Feb 01, 2012 6:01 am Post subject: FireFly CofG

I've had a couple of off-list emails strongly cautioning me to keep power

on right to touch-down, and I take that advice seriously.  I'm used to

always pulling power at base leg and glide approach all the way to

touchdown, but certainly won't be doing that in the FireFly, at least in the

beginning.  But still need to practice dead stick landings just in case.....

 



JC G/Kolbers:



Don't need power if you simply push the nose down to glide.



Since 1984, when I built and flew my first Kolb, I have made it a habit to

shoot landings at idle power settings just in case the two stroke quit.  In

the early days two strokes had a habit of quitting at idle and just when you

needed power.  I figured if I could make the field at idle, I could make the

field with dead stick.  I carried through with the same habit of flying my

Kolb with the 912 engines for the last 19 years.



Carry power if you can't fly the Kolb.



Never had a problem of lack of elevator authority with a Firefly power on or

off.



Never had a cg problem with a Kolb unless someone built it with drastic

modifications that would change the cg of a plans built Kolb.



I like JC's comment of not carrying lead, but substitute cargo and survival

gear and supplies.



If my MKIII flies well with a 12+ lb Maule Tundra Tail Wheel, I don't think

I have an aft cg problem, power on or power off.



Kolb "quit" only happens to Kolb pilots that land above the airstrip and not

on it.  Takes airspeed to stay above the stall.



john h

mkIII

Titus, Alabama

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

jbhart(at)onlyinternet.ne
Guest

Posted: Wed Feb 01, 2012 11:54 am Post subject: FireFly CofG

Date: Wed, 1 Feb 2012 20:58:08 +1000

From: JC Gilpin <j.gilpin(at)bigpond.com>

JP,

 	  Quote: 	
		  .......................

My main concern is that a high thrust line pusher is a real trap for aft 

CofG. The prop thrust gives a nose-down moment, balancing the nose-up moment 

of the aft CofG, making it all balance well, until the engine stops......... 

and then that high thrust line suddenly becomes a high drag line, and then 

both the high drag line and the aft CofG nose-up moments are summed.

 	  Quote: 	

This is not the case.  The high thrust line is above the profile drag 

center.  If the engine and thrust line is trimmed for level flight at cruise 

and the engine quits, at that instant there will be no difference in profile 

drag and wing drag.  If the thrust line is pointing down at cruise, it will 

try to hold the tail up and once the engine dies the nose will want to come 

up.  etc.  If you let the nose pitch up wing drag and profile drag will 

increase.  So in all cases the best thing to do when the engine quits is to 

move the stick forward and maintain best glide speed.  Profile drag will 

remain almost constant but wing drag will be reduced.

 	  Quote: 	
		  At the same time the elevator authority is much reduced by the lack of prop 

blast.

 	  Quote: 	

Not so.  Standard FireFly configuration puts very little if any air over the 

horizontal tail surfaces.  See:

http://jackbhart.com/firefly/firefly129.html

 	  Quote: 	
		  Kolb flyers know this from experience, and some have learned the h-a-r-d 

way..... I've had a couple of off-list emails strongly cautioning me to keep 

power on right to touch-down, and I take that advice seriously. I'm used to 

always pulling power at base leg and glide approach all the way to 

touchdown, but certainly won't be doing that in the FireFly, at least in the 

beginning. 

 	  Quote: 	

There is no reason not to pull power at the base leg, just keep your pattern 

tight and keep the air speed over 45 mphi or higher.  One of the best things 

you can do to prepare your self for an engine out is to practice higher and 

higher pattern approaches, closing the throttle at the same point and 

learning how to spill altitude and to touch down at the same spot on the 

runway.

Jack B. Hart FF004

Winchester, IN

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Wed Feb 01, 2012 12:16 pm Post subject: FireFly CofG

There is no reason not to pull power at the base leg, just keep your pattern

tight and keep the air speed over 45 mphi or higher.  One of the best things

you can do to prepare your self for an engine out is to practice higher and

higher pattern approaches, closing the throttle at the same point and

learning how to spill altitude and to touch down at the same spot on the

runway.



Jack B. Hart FF004

 

Jack H/Kolbers:



That was a good post.



However, you could saved a lot of typing by saying:  "Fly the airplane."

It's pretty simple.



Most folks that have problems flying a Kolb don't fly the airplane and blame

it on the Kolb, i.e., Kolb quit and can't land without power.



john h

mkIII

Titus, Alabama

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

herbgh(at)nctc.com
Guest

Posted: Wed Feb 01, 2012 12:31 pm Post subject: FireFly CofG

Good points Jack....do not think I ever want to be in an airplane 

that will not glide..  even 6 to 1 is better than 1 to 1....  Herb

At 01:55 PM 2/1/2012, you wrote:

 	  Quote: 	

Date: Wed, 1 Feb 2012 20:58:08 +1000

From: JC Gilpin <j.gilpin(at)bigpond.com>

JP,

 >.......................

My main concern is that a high thrust line pusher is a real trap for aft

CofG. The prop thrust gives a nose-down moment, balancing the nose-up moment

of the aft CofG, making it all balance well, until the engine stops.........

and then that high thrust line suddenly becomes a high drag line, and then

both the high drag line and the aft CofG nose-up moments are summed.

 >

This is not the case.  The high thrust line is above the profile drag

center.  If the engine and thrust line is trimmed for level flight at cruise

and the engine quits, at that instant there will be no difference in profile

drag and wing drag.  If the thrust line is pointing down at cruise, it will

try to hold the tail up and once the engine dies the nose will want to come

up.  etc.  If you let the nose pitch up wing drag and profile drag will

increase.  So in all cases the best thing to do when the engine quits is to

move the stick forward and maintain best glide speed.  Profile drag will

remain almost constant but wing drag will be reduced.

 >At the same time the elevator authority is much reduced by the lack of prop

blast.

 >

Not so.  Standard FireFly configuration puts very little if any air over the

horizontal tail surfaces.  See:

http://jackbhart.com/firefly/firefly129.html

 >Kolb flyers know this from experience, and some have learned the h-a-r-d

way..... I've had a couple of off-list emails strongly cautioning me to keep

power on right to touch-down, and I take that advice seriously. I'm used to

always pulling power at base leg and glide approach all the way to

touchdown, but certainly won't be doing that in the FireFly, at least in the

beginning.

 >

There is no reason not to pull power at the base leg, just keep your pattern

tight and keep the air speed over 45 mphi or higher.  One of the best things

you can do to prepare your self for an engine out is to practice higher and

higher pattern approaches, closing the throttle at the same point and

learning how to spill altitude and to touch down at the same spot on the

runway.

Jack B. Hart FF004

Winchester, IN

neilsenrm(at)gmail.com
Guest

Posted: Wed Feb 01, 2012 6:33 pm Post subject: FireFly CofG

Our Kolbs have a tremendous capability to fly in and out of very short fields. The very steep approach angle with very little flair time is necessary to be able to complete incredibly short landings. It's what they were designed for. Pilots new to Kolbs are advised to maintain power on approach right down to the landing flair. Later after a few landings it is good to start gradually exploring the planes capability but go slowly. My GA experience made my transition to my Kolb more difficult. John is right it is just a simple matter of maintaining flying speed. It really is that simple. The problem is pilots new to Kolbs aren't prepared for the visual impact of seeing the high ground closure rate up so close and personal. The natural reaction is to flare way too high and without power, flying speed is lost very quickly and that isn't good. So we have a very well designed airplane, we just need to learn how to fly them properly to be able to use all their capabilities. In summery there is no such thing as Kolb quit there is only pilot quit. 



Rick Neilsen

Redrive VW Powered MKIIIC 

 

On Wed, Feb 1, 2012 at 3:11 PM, John Hauck <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)> wrote:

[quote]  --> Kolb-List message posted by: "John Hauck" <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)>

 

 

 

 

There is no reason not to pull power at the base leg, just keep your pattern

 tight and keep the air speed over 45 mphi or higher.  One of the best things

 you can do to prepare your self for an engine out is to practice higher and

 higher pattern approaches, closing the throttle at the same point and

 learning how to spill altitude and to touch down at the same spot on the

 runway.

 

 Jack B. Hart FF004

 

 

 

 Jack H/Kolbers:

 

 That was a good post.

 

 However, you could saved a lot of typing by saying:  "Fly the airplane."

 It's pretty simple.

 

 Most folks that have problems flying a Kolb don't fly the airplane and blame

 it on the Kolb, i.e., Kolb quit and can't land without power.

 

 john h

 mkIII

 Titus, Alabama

 

 

 

 ===========

 arget="_blank">http://www.matronics.com/Navigator?Kolb-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 



[b]

capedavis(at)yahoo.com
Guest

Posted: Wed Feb 01, 2012 7:14 pm Post subject: FireFly CofG

John and Jack and Kolbers , I agree that is no reason to not pull the power at base i was in the habit of pulling power as soon as I turned downwind but that was from flying Gliders thats why I believe that the best training one can get for any light powered aircraft is in a Glider  , there you learn to fly the aicraft you learn to be infinitely variable as things change what you do changes you got to land the aircraft the first time everytime, there are no gorounds, there  is no blaming the aircraft because the training gliders 2-33 or the equal have been landed successfully in every condition , its all you, just fly the aircraft . just my 2 cents Chris

 

  

 Chris Davis KXP 503 492 hrs Glider Pilot Disabled from crash building Firefly



    

From: John Hauck <jhauck(at)elmore.rr.com>

To: kolb-list(at)matronics.com 

Sent: Wednesday, February 1, 2012 3:11 PM

Subject: RE: Kolb-List: Re: FireFly CofG

--> Kolb-List message posted by: "John Hauck" <jhauck(at)elmore.rr.com (jhauck(at)elmore.rr.com)>



There is no reason not to pull power at the base leg, just keep your pattern

tight and keep the  air speed over 45 mphi or higher.  One of the best things

you can do to prepare your self for an engine out is to practice higher and

higher pattern approaches, closing the throttle at the same point and

learning how to spill altitude and to touch down at the same spot on the

runway.



Jack B. Hart FF004



Jack H/Kolbers:



That was a good post.



However, you could saved a lot of typing by saying:  "Fly the airplane."

It's pretty simple.



Most folks that have problems flying a Kolb don't fly the airplane and blame

it on the Kolb, i.e., Kolb quit and can't land without power.



john h

mkIII

Tit.matronics.com/Navigator?Kolb-List" target=_blank>http://www.matronics.co========================

 [quote][b]

johngilpin

Joined: 23 Mar 2011
Posts: 93
Location: 004

Posted: Thu Feb 02, 2012 1:36 am Post subject: FireFly CofG

OK, that all sounds just fine.  I'm used to diving at the ground on final approach, with plenty of airspeed right to a round-out just in time, then holding off one foot above the ground until airspeed decays such that it absolutely can't fly any more.  That's just the way I flew my Spectrum Beaver for 1000 hrs.  Somehow I'd got the impression that the Kolb was different, but now I'm really looking forward to this.  



Thanks for all the input.

JG

  [quote][b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Feb 02, 2012 4:18 am Post subject: FireFly CofG

 Somehow I'd got the impression that the Kolb was different, but now I'm really looking forward to this.  

JG

[quote]   The Fire Fly is a scaled down Sling Shot.  With a 40 hp engine it is a little hot rod, very agile, quick roll rate.  It does well in rough air. john hmkIIITitus, Alabama [b]

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

zeprep251(at)aol.com
Guest

Posted: Thu Feb 02, 2012 10:56 am Post subject: FireFly CofG

Listers'

 99% of my MK3 landings,short spring steel gear legs,are full stall 3 point events.Approach with engine at idle,Jabiru 2200a 900rpm static idle,and w/vg's.Only with stiff cross winds do I wheel land it or use some power .It's just like any other tail wheel aircraft.

 G.Aman

    

  

     

  

     

  

    --

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Thu Feb 02, 2012 1:01 pm Post subject: FireFly CofG

Gary, Ken's Mk III has the wings set at 2.8 degrees relative to the engine mount and has the long steel tube gear.  I tried a full stall landing, she landed tail wheel first. Hence I wheel her on three.



 Rick



On Thu, Feb 2, 2012 at 12:51 PM, Gary Aman <zeprep251(at)aol.com (zeprep251(at)aol.com)> wrote:

[quote] Listers'

 99% of my MK3 landings,short spring steel gear legs,are full stall 3 point events.Approach with engine at idle,Jabiru 2200a 900rpm static idle,and w/vg's.Only with stiff cross winds do I wheel land it or use some power .It's just like any other tail wheel aircraft.

  G.Aman

    

  

     

  

     

  

    --

_________________
The smallest miracle right in front of you is enough to make you happy....

zeprep251(at)aol.com
Guest

Posted: Thu Feb 02, 2012 1:19 pm Post subject: FireFly CofG

Rick,

 What is the plans built angle for the old MK3?

    Gary

  

     

  

     

  

    --

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Feb 02, 2012 6:54 pm Post subject: FireFly CofG

Listers'

99% of my MK3 landings,short spring steel gear legs,are full

stall 3 point events.Approach with engine at idle,Jabiru

2200a 900rpm static idle,and w/vg's.Only with stiff cross

winds do I wheel land it or use some power .It's just like

any other tail wheel aircraft.

G.Aman

 

Me too, Gary.



I also use full flaps (40 degrees), unless strong cross wind

or at "real" airports with long runways.



If I stall above the ground, the aircraft will drop, whether

Kolb, Cessna, or Piper.



john h

mkIII

Woodville, Florida

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Feb 02, 2012 7:06 pm Post subject: FireFly CofG

Gary, Ken's Mk III has the wings set at 2.8 degrees relative

to the engine mount and has the long steel tube gear.  I

tried a full stall landing, she landed tail wheel first.

Hence I wheel her on three.



Rick

 



Don't pull the nose up so high.



The US three points perfectly.



My original FS did too, because it had 35.5" long main gear

legs.



My MKIII does the same because the main gear have been

reconfigured and got the nose in the air.



john h

mkIII

Titus, Alabama

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Feb 02, 2012 7:12 pm Post subject: FireFly CofG

Rick,

What is the plans built angle for the old MK3?

Gary

 

It is variable, depending on how the builder interpreted the

rigging insturctions.  I'll bet there aren't many rigged the

same.  Doesn't make a whole lot of difference.  Most of us

would never be able to tell.



john h

mkIII

Titus, Alabama

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

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