1st flt Avid - impressions

[Turbo 162]

Celebrated Cinco de Mayo 2018 with first flight...yowtza!  Mine, N23PB is STOL taildragger with grey-head 582, 3:1 C-box, swinging 72" 3-bladed IVO.

I've got to admit all this talk about groundloops had me fearing 1st flight, wondering if I too would immediately fall prey.  The good-news takeaway for me was the realization that the Avid has plenty of rudder authority on landing!  The one-person 25mph stall speed is pure myth.  Stall IAS showed up around 40 mph, with no steady-state stall per se, just a controllable mush.  Engine was smooth (above idle) and powerful, and P-factor is reminiscent of WW2 warbirds with their huge props. I found myself sideways on steep climbout before applying the required left rudder.  Just putting around the sky was great; down to 4000rpm I could hold altitude just fine.  4500 seemed a good cruise rpm.  In 1.8 hrs I burned just 5 gallons!  According to the Rotax data, the engine should be burning 3.3 gph at that rpm. Thermal efficiency is pretty good there as well - just below 30%!  But it goes down with rpm - to just over 20% at 6000 rpm.  I'll post fuel flow & thermal efficiency data in customary units if desired, translated from Rotax data in the metric system.  

I could not do a graceful takeoff!  The bird ran along the ground, then ballooned up suddenly!  I clearly need practice!  Landing proved way more problematic.  The bird just didn't want to come down, and I executed a number of go-arounds.  The short, narrow runway demanded more of me than I expected: my landings were awful!  I will go elsewhere to practice!  And practice I must!  This bird was demanding, and I fear grace may prove elusive.   Hats off to you guys who fly her well!   

Shaky Jake has nothing on the 582.  The cabin noise & vibration at idle (below, say 3000 rpm) were horrible.  I am contemplating a clutch to help with that, but need some inputs from those who have gone there.  What does a freewheeling prop do to landing approach?  How are taxiing and landing runout affected?  All-in-all, it was a very exciting day!  - Turbo

 

[1avidflyer 1983]

Glad you got it in the air (and back down)safely :-)  Never had a clutch, so I can't address that.  Leni has used one, if I remember right, he said it acts like a big airbrake when it goes to freewheel mode.  If your ASI is accurate, get slowed up to about 55 or maybe just a bit less on final, it will come down.   Grass is very nice to fly off of.   Way better than pavement.   I usually cruised at 5000-5200 rpm to just put around.  What model do you have?  What is the empty weight.  For noise, get a good headset.  Oh, and wipe that grin off yer face!    JImChuk

[Turbo 162]

Thanks for the words of encouragement, JimChuck.  Mine is the C model, with empty weight around 470lbs.  After banging it in trying to land slow, I settled on 55mph for final.  Seems to me a clutch will give a big step between high windmilling drag and positive thrust with the clutch engaged, with no in-between.  Without, and with static idle set at 2300 rpm roughly, idle on final gave me a rough 3000rpm.  After touchdown, it didn't want to slow down!  I'm glad the brakes are weak enough to keep me out of trouble, since I had to use them to slow down.  I expect a clutch would help there, too.  The IVO prop has a sharp leading edge, which I expect would help reduce windmilling drag since the prop's backside would be stalled when windmilling. At least them little airfoils are stalled!  For a bird that small, that prop seems a monster!

[akflyer 1427]

Congrats on the first flights! 

The freewheeling prop is a huge air brake.. That's a good thing landing short.  You can set the idle at 1400 all day long and its smooth as silk.  You can keep the prop engaged by keeping the RPM up a tad as well.  The only time the freewheeling prop truly sucks is when you have an engine out.  In that case, look at the spot directly under you as that's pretty much how far you are going to glide.  What tailwheel do you have?  It does not take much practice at all to keep the prop turning right where you want it with the clutch, I miss having mine and will soon be spending the money on another one. 

Diving for the runway is the best way to float past the end of it.  Did you play with the flaperons?? My plane is 100 pounds heavier than yours empty and it stalls right around 40 as well, just a touch under with the flaperons on.  With the VG's the only way to really get it to break is to do power on stalls or to really yank the nose up and hold it there.  If you just ease into it them it will just go into a mush.

Spend some time practicing your landings at say.. 2000' AGL.  Basically see how slow you can fly it and yet have just enough speed to get your sink rate to 0 or close to it just prior to hitting 1K on the altimeter.  Or start off at 3K and use 2K for your virtual run way in the sky as your target goal to arrest sink rate. 

I tend to fly mine behind the power curve most of the time dragging it in with lots of power as needed to keep the AS as slow as possible, but I know full when that if the engine burps I have a pretty good chance of becoming a lawn dart. 

At any rate, I would bet that within 4 or 5 hrs you will be much more comfortable flying these birds and your landings will come right into line.

 

[Turbo 162]

I've got the Maule tailwheel, which doesn't give the wings much AOA on the ground.  It seems the rough idle is due in part to some kind of engine-prop resonance.  It seemed like it wanted to shake unplugged all my instruments!  Is this a C-box only phenom, or do the other boxes have torsional impulse softening rubbers?  If your opinion is that the clutch is worthwhile and manageable, I reckon I'm in.  The 582 seems a robust little engine, if one obeys the rules:  1. Don't take off before achieving operating water temp,  2. Keep egt between 1000 and 1200 Fahrenheit, 3. Give it a little time to cool back down, and 4. Keep an eagle eye out for coolant leaks.  Seems simple enough.   Leni, thanks for the encouragement.

[Turbo 162]

Oh yeah, the flaperons:  I did not use them.  Previous owner & builder did nothing for trim, and this first flight I was also test-flying a first iteration version.  It didn't work, so I was wthout trim, which makes holding airspeed not-so-easy.  On top of this, I was holding left-stick to stay level, i had a cheezy com system, it was saturday, with traffic, including glider ops.  Hood river is a short, narrow strip, so I may have bit off a bit too much!  But what a nice, smooth, calm day!  Suffice it to say bird & pilot survived!

[1avidflyer 1983]

I would get the feel for the plane before I worry to much about flaperons.  If the plane wants to climb, you can add just a bit of flaperons and that will push the nose down.  For some reason that I don't understand, it might even lift a heavy wing.   A light bungee tied to the seat truss and going around the joystick works good for nose up trim.  All the way down, it does nothing, higher up you set it, the more it pulls back on the stick.  For the heavy left stick, check the wash out in the wings with a 4' level.  Front spar to trailing edge near the wing tip, same place on both sides to see if there is a bunch of difference.  That could account for one wing being "heavy".  Something is wrong that you have that much vibration.  Be carefull it could shake a carb loose.  Not good! What rpm was it shaking the worst?  JImChuk

PS  pictures also show the aluminum angel that stops the elevator control tube end from being rolled around the joystick cross tube.  

Edited 8 May 2018 by 1avidflyer

[Turbo 162]

I am planning to adjust the port wing twist.  Will use inclinometer as you suggested, for how much.  I have a series of springs of different stiffness to try for the trim.  Right away I'm going to the stiffest.  Ship wanted to dive; not enough decalage. I was only holding about 1/2 " left stick, so it's not too far out of rig.  Rough running was only on the idle jets, less than 3000rpm.  I was close to the Rotax " one turn" setting, so carbs were rich at idle.  I think I'll play with them some more before ordering a clutch, since engine-out glide is a safety consideration.  I wonder if this roughness is a C-box resonance thing.

[Turbo 162]

Again, the flaperons:  I was not too happy to find that the flaperon mixer geometry is such that, at higher flap deflections, the flaperon's down deflection is greater than the other side's up deflection.  Maybe I'm all wet here, but I think there's a simple way to reverse that nasty characteristic.  This would enhance safety and allow greater flap deflections for landing.  Wouldn'it be nice to have flaps we could actually use?  Currently, I'm unclear as to the advantages of these Junkers-style flaperons over the more conventional flaps & ailerons, aside from being easy to build.

[Av8r_Sed 82]

I agree with everything Leni said about the clutch. I went to it because I’m running a fairly heavy IVO medium and there was no way to get a smooth idle without it. When the vibration got bad it upset the carb floats and ended up barfing gas out on the exhaust. 

Approach with a freewheeling prop and a slow airspeed gets you in nice and short but requires a shot of power to arrest the considerable sink rate and avoid an embarrasing “arrival”. 

The only other negative to the clutch is you can’t prop the engine, nor turn it over to bring a piston to TDC. 

[C5Engineer 1170]

Take the time to tune the bottom end you will be much happier. Very few people run the clutch. I have 450 hrs on my E box. I run 50 idle jets and the air screws out 3.5 turns at Sea Level. It idles nice at 2000 rpm with a 3 bladed Ivo and the 2 bladed Warp before that. I'm running a clutch on my new Avid and I'm still up in the air. It starts really nice but it adds to maintenance and I've had it slip once on take off which will really get your attention. Thousands of 582's out there without it. Pretty spendy mod just to smooth out your idle.

[akflyer 1427]

Again, the flaperons:  I was not too happy to find that the flaperon mixer geometry is such that, at higher flap deflections, the flaperon's down deflection is greater than the other side's up deflection.  Maybe I'm all wet here, but I think there's a simple way to reverse that nasty characteristic.  This would enhance safety and allow greater flap deflections for landing.  Wouldn'it be nice to have flaps we could actually use?  Currently, I'm unclear as to the advantages of these Junkers-style flaperons over the more conventional flaps & ailerons, aside from being easy to build.

You can truly only get in so much flap action before you run out of elevator to compensate for the nose down pitching when you pull them on.  15 degree is a pretty safe bet and yes it does make a difference.  you can get 20 deg out of them on a day when the wind is pretty much straight on the nose and your not having to use lots of roll input.  Again, get in the air and play with these settings.  You can do slow flight all day long at 5000 RPM just slowly keep pulling the nose up and get the plane to slow down. 

Remember that the very best performance mod you can do for any airplane is to put more gas through the tanks! 

Adjusting the rod end on the strut will get rid of the rolling moment you have and its quick and easy to do.

 

[Turbo 162]

Thanks for all the tips & info, guys!  Leni's comment re running out of elevator makes me wonder why Dean Wilson didn't start with the low-moment NACA 23012 and just find an acceptable LE shape mod to keep the high CL max while using a 2.5" radius.  My experience as an aerodynamicist holds that undercambering the undersurface can help up near the L.E., but further aft does almost nothing for max CL, while adding undesirable nose-down moment, especially in the aft end, near the T.E.  Oh well!  Maybe the best place for VGs is the H-stab's undersurface.  A flat-plate stab has got to have pathetic aerodynamics.  If only there was an easy way to seal the gap beteen stab & elevator.

 Thanks, Joey for the encouragement.  I will play around with idle mixture a bit more.  It's nice to know that smooth, slow idle is possible!  The internals of the E-box include a torsional softener like the C-box has, right? 

Looks like I'll be making up new bungees.  Merci to Fred Stork for posting a great way to fab the end loops.  Love your videos flying around France in the springtime!

[akflyer 1427]

Think ease of building and flying... the flat plate stab has been used on the cub lines as well as many others for a very long time.  Think again at what you flying.  If you want a higher performance plane then the Avid / kitfox line may not be for you.  The plane was designed and built to be light, slow and easy to build.  Yes there are some trade off to it but it is what it is for the most part and when you put some time in the seat you will learn to enjoy it.

The benefits of the junkers style flaperons are well documented.  Even when the wing stalls you still have full control.

Do you have the F7A arms installed?  This helps with the adverse yaw.

Running out of elevator when you add in more flap deflection than it is designed to handle.  Once again, stay within design limitations or you have to make a larger elevator.

Easy way to seal the gap?  that has been documented on here MANY times.  Gorilla tape works, clear tape works, the clear thick tape used on the top of snowboards works well.  Gap seals can be made from foam or anything else you want to use, its experimental and its easy to do and you don't have to have anyones approval to do it.

At the end of the day, its hard to make a silk purse from a sows ear but then again, none of us wanted a silk purse to begin with LOL

Once again I recommend that before you start doing anything with it other than adjust the strut end to get the roll out of it is to put some gas through the tanks and get YOU up to speed on the plane and its quirks.  It is a very easy plane to fly and is nice and light on the controls, you just need a little time to get used to it.  Pretty much about the same as going from flying a cub to getting some time in a slippery 210.  There is a big difference in how you have to fly the 2 different airplanes and you wont get good at flying either one unless you spend some time learning they 2 different types of animals that they are.

 

 

 

[Ramos 62]

If you want an airport all to yourself, come on out to Wasco,Oregon. Airport 35S, 3,450X60 feet. No services and no aircraft other than two spray planes that should be about done with Spring work. We are about 50 miles East of you and nine miles South of the river.

[Bandit 286]

Remember Dean designed these airplanes to fly out of grass pastures and keep simple. They are not 747s. Like Leni said learn to fly the airplane and you will enjoy it. No need to try to make it something it will never be. 

[Turbo 162]

From y'all's comments, I must have come across as whinging.  My bad.  It may be the curse of being an old design engineer to always think design, and it makes one perhaps a bit more critical.  The Avid is what it is, and hey, I bought it!  I like the little bird, and am looking forward to flying it, and working to improve it where I can, like everyone else on the site.  My first flight was more exciting, almost scary, than I anticipated, but that will change as my mastery of the beast improves.  I have windsurfed the Gorge in winds gusting to 50+ mph, so I know I can do this, especially with all the experience y'all bring to the site, and for which I am grateful.  Obviously what I need is lots more time-in-the-cockpit.

[zadwit 105]

I flew a factory new 582 not long ago with a C gear box adn 3 blade warp drive prop. WHen it was warm it would idle smoothly at 2200 rpm. I did have to go DOWN one size in jets to #50s on the idle mixture like C-5 says above and it will idle smoother.....being that engine sat for a number of years the carbs are likely gummed up...

not sure of a good way to clean them but I have taken them off and apart and the jets out, not to hard to do any of this, and then soaked them in sea foam. I used sea foam mainly so I wouldnt ruin any O rings if I got it on... other wise I guess carb cleaner would work...

NOTE: if you do manage to get it to idle smooth at 2200 or so with the throttle closed, remember to then adjust the idle speed down to around 1400 rpm  otherwise when you are in the air, it will be around 3000 rpm at idle when you close the throttle due to the unloading effect on the prop.....

 

Look at the KF4, they did change the airfoil, increase the tail size and airfoil shape of the tail...HOWEVER I think the earlier models take off shorter and perform better due to their lighter empty wt. The model 4s and up are a lot heavier and weight KILLs these little planes....

[zadwit 105]

You might also remove the cam off the maule tailwheel or else just throw it in the Columbia and buy a MATCO... A couple of years ago a guy trashed a nice kitfox in your area due to wind and the TW unlocking....on landing

[Turbo 162]

I had the carbs apart and they are clean, including the idle jets.  The floats had sunk, so I had to buy new ones.  Gotta look to see what size those idle jets are, though.  Joey flies out of somehere near Fairfield, which has to be less than 100 ft elevation, so maybe the #50 idle jets is a good call right out of the box.  I too will be flying out of fields at less than 1000 ft elevation.  Totally agree re static idle rpm vs on final - part of why I had a tough time getting the bird down.  Trees at approach end of runway & short strip - bad combo for green TW pilot in unfamiliar bird.  Smooth at 1400 static is my new goal!  Next time The Dalles with 5000 ft, 100 ft wide tarmac!  Just loved putting around the verdant Hood River valley & hills, though.  This is why airplanes have such magic.

 

[zadwit 105]

Because of the mass airflow thru a two stroke engine, it is real hard if not impossible to get it to idle much below 2200-2300 mainly because of the prop load, the turngind of the gearbox and prop... I have a clutch on one of my engines and it will idle down below 2000 maybe as low at 1400 just like a snow machine engine sounds...

Im sure you read the pros and cons of clutch... one thing the guys didnt mention, is the C and E gearbox havbe a rubber dampner in the gearbox adn it "steals" power...

 

I easily got 100 rpm more on takeoff with my clutch......I flew in the morning with the standard setup, then install the clutch and flew the same day a few hours later and saw 100 more rpm on takeoff and climbout...its because you dont waste power compressing and expanding that rubber coupler....it is mainly installed for low speed to protect the gears from chatter...

[zadwit 105]

IF you install the smaller idle jets, then install the clutch, you will first notice the idle speed is too high and even if you back the idle speed nut(the big one) all the way out it still  might be too high....IF that happens, you might have to take a dremmel tool and cut the groove a little higher , the one the idle speed screwpresses on the slide...

I like the clutch,it is easier on the engine.... cant hand prop but if you have a good battery and starter not a problem.....

[zadwit 105]

I think there is a way to pressure test the case to see if the crank seals are leaking or not......somewhere on this site or teamkitfox site....

Maybe joey (C5) knows....

[zadwit 105]

I saw a kitfox model 2 wrecked on takeoff because the guy tried full flap takeoff (no wind) but one wing went down and when he fed in aileron the flaperone on the low wing went further down and stalled the wing which hit the ground, dug in and flipped the plane.. major damage and all in about 100 ft ground roll.

In hte KF manual they say to rig the flaperone for 23 degrees down, no more.. I did and  you have very little aileron control.. I would not use them at all in the wind, you are asking for it... the advantage is you have aileron control in the stall...

Install a set of the cheap (100) stol speed VGs from aircraft spruce.. I put a set on my Ridge runner and stall went from 35 mph to 26mph... 

location is critical but most say 2" aft of the WLE, any farther back and they dont help,  IT was 28 (f) and 2500 msl) when I flew this, gross wt=660 #, that plane is light single seat...

 

 

 

[zadwit 105]

I had the carbs apart and they are clean, including the idle jets.  The floats had sunk, so I had to buy new ones.  Gotta look to see what size those idle jets are, though.  Joey flies out of somehere near Fairfield, which has to be less than 100 ft elevation, so maybe the #50 idle jets is a good call right out of the box.  I too will be flying out of fields at less than 1000 ft elevation.  Totally agree re static idle rpm vs on final - part of why I had a tough time getting the bird down.  Trees at approach end of runway & short strip - bad combo for green TW pilot in unfamiliar bird.  Smooth at 1400 static is my new goal!  Next time The Dalles with 5000 ft, 100 ft wide tarmac!  Just loved putting around the verdant Hood River valley & hills, though.  This is why airplanes have such magic.

 

Aircraft spruce has the jets , about $60 a piece!!!! but they make it run better....