Thursday, January 26, 2012

Flying the Kolb FireFly




Flying Characteristics of the Kolb FireFly:

The FireFly is the 'sports car' of ultralights.  The short wings and very positive three-axis controls make it handle like a true sports car, especially compared to the usual large wing, high drag, traditional ultralights.  The short wings allow it to handle turbulence much better than the other ultralights.  Still some bumps and rock-and-roll, but just fly though it and always have instant control to correct.  So different from the other ultralights that get thrown around so violently in thermals.

Slow cruise is 50mph, fast cruise 60mph, top speed secret......

The aircraft flies really well.  I had expected that the short (22') wing span to be a bit touchy in roll, but not so, it's quite docile, and hands off it stays level.    I've flown as much as 20 miles in a gentle descent from 10,000 ft without touching the stick at all, just a bit of rudder to keep the course.  It's also well balanced in trim.  Let go the stick, and at cruise power it stabilizes at about 65mph in a shallow descent, at idle power it stabilizes in a glide at about 50mph, the speed that's best for approach.  It's dynamically stable and won't go into an increasing dive or nose up.  I didn't expect a high thrust-line pusher to  be so stable.  The glide at idle power is very stable, with good control response right down to touchdown.  With the VGs, stall is pretty much nonexistent, just a descending mush, still with aileron control.

Landing characteristics:

The short wing makes for a higher landing speed, but this does have advantages on good airstrips.  It gives very crisp and positive control response right down to touchdown, and less influenced by turbulent winds than at slower speed.  Due to the flat stance on the landing gear you can't do a full stall landing, it's more of a fly-it-on at about 42mph.  This is a characteristic of Kolb design, to make it safer for beginning fliers.  Approach is very stable at 50mph, no less.  Due to low momentum it'll lose speed quickly after round-out, so it's best to apply 4000rpm on late approach, then it's a very gradual descent with lots of time to get stable and set up real close to the ground and then just let it settle on by itself.  Don't try to hold off for a full stall landing, or the tailwheel will touch first while the mains are still  a couple for feet in the air, and then they'll will come down with a thump....  And don't try to deliberately plant it on the ground, just hold it straight and level and let it land itself.  Then stick right back and be lively on the pedals to keep it straight.  Don't let it start a swerve or it can quickly get worse....

I've never had a ground loop with the bigger tailwheel, despite landing in strong crosswinds.  With the original factory 'pizza cutter' wheel I did run off narrow strips a couple of times, with that narrow wheel plowing in soft dirt, or skipping on stony asphalt, but still never a full ground loop.  That flat stance on the ground, short wing, and low dihedral, is also very good at preventing a cross-wind from getting under a wing and lifting it, as can happen all to often to other ultralights.  The roll-out is longer than slower landing ultralights, but is easily controllable, and hey, this is a 'sports car', not a '4wd'.....

But I really needed a' 4wd' aircraft instead of a 'sports car' so it didn't suit my needs as well as I would have liked, but it's the only ultralight that folds and transports so well.  I was able to make it do the job, but it was often somewhat like taking a sports car off-road - must do it carefully, and avoid really rough ground.  That very open view from the front seat was excellent for photography, but felt quite exposed when I looked down at the rough country that I would have to ditch into if the single ignition two-stroke behind me decided to quit.  I had already tipped it on it's nose when braking heavily in a tight spot, so no doubt if the mains hit obstacles or heavy foliage at that high landing speed, it would go right up on it's nose and over on it's back, which would put my face in the dirt......  Sure would have liked to have some sturdy pilot protection overhead and down in front.....  But that ridiculous weight limit of 254 lb (115 kg) for this Part 103 category just barely makes a flyable aircraft and doesn't allow much provision for pilot protection....

Pilot protection is a big issue for me because some years ago I hooked the wheels of a much modified Beaver aircraft in a power line and hit the ground vertical nose down, really hard.....  Hopped away with only a broken ankle due to the considerable pilot protection structure that I had built into that aircraft....  So I know that with a sufficient pilot cage around you, you can survive just about anything in these slow, low-momentum ultralights.  The little FireFly doesn't have any such protection, so should always stay in reach of a good landing site.  I couldn't always be confined like that, cause I wanted to explore farther afield, but it was often with an uncomfortable feeling as I looked down at a lack of suitable outlanding options......  Don't like pine forests at all....  This was compounded by the fact that I couldn't get medical insurance to fly an ultralight over there.....  From what we hear of the medical system in the US, if I  ended up in hospital for a couple of weeks with a broken leg in traction, that would clean out all my retirement savings.......  So I jokingly commented that I would try to crash near a road and then crawl up on it and pretend to be road kill....

Even with engine off, prop stopped, the glide is stable and good control.  The glide slope is pretty steep, but easy to maintain the critical 55mph right to the round-out.  The round-out and hold off must be right close to the ground because the speed will decay very quickly without power.  I had an engine stoppage while on downwind at Moab UT airport.  As always, I was on a close-in downwind with plenty of height, so it was easy to do a dead stick landing onto the runway, just as smooth you please!

It's been a great  little aircraft for aerial photography, never has the tendency to get into trouble while I'm distracted in the viewfinder.  To do the photography that I wanted, I often had to fly in less than favourable conditions, and sometimes come back to land in really difficult conditions, but it handled all that really well.



Trailering

I found that having a folding ultralight in a trailer/hangar works very well with 103 ultralights.  With that limitation of only 5 gallons of fuel, there’s very limited range.  I kept meeting Part 103 ultralight flyers who were really bored from just flying around the circuit and to a couple of neighbouring airfields and swapping the same stories with the same fellas.  If they could trailer their aircraft then they could move to a different airfield once in awhile, and fly with different company and hear some different b/s stories.  Don’t have to go chasing all around the country like I did, but surely that gets pretty tempting when you have the mobility that a trailer/hangar gives, and you have the possibility for the views that I saw....  San Andreas Fault, the Arizona meteorite crater, Moab, etc,etc... 

So I was surprised at how difficult it was to find a buyer for the rig.  The Barnstormers ad included a link to this weblog, and I would have thought that would excite others who wanted to do the same.  But not so.....  

The trailer also makes a secure hangar when storms blow through.  At Shelby MT the official recording of a storm front was 67 mph.  No way this light kite would have survived that blast, but I had it safely inside the trailer.  Several other times I had to load quickly to get safe from dust devils and hail storms. Must always remember to fold-and-load before the wind hits, cause it’s very risky to unbolt and handle a wing once its blowing hard....  And it must be easy and quick to do for one person.  The Kolb took 15 minutes to fold/unfold, and 15 minutes more to load and secure.

The Argosy still looked like a travel trailer, which caused a problem once.  I was unhitching to leave the trailer at an airfield near Mendocino CA, when the sheriff stopped and said that I couldn’t camp there.  (They’re very fussy about transients camping around that upmarket coast...)  When he looked inside he got a surprise, and when he didn’t see a bed in there he drove away again.  Then I drove the truck around behind some bushes and camped there out of sight.




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