Third Wave

(Hang Gliding Magazine, March 2004)

By Mike Sandlin

First the hang gliders, then the paragliders, and now... are the ultralight

sailplanes coming to your local flying site?

On a good soaring day, I load my glider on top of my truck and head

for my local mountain hang gliding site, where I set up with the gang, launch,

soar, land in the L.Z., and swap stories about the day's flying. This has been

going on for years, but this season there's a new twist: I'm not flying a hang

glider or a paraglider anymore, I'm flying an airchair, a new species of

ultralight sailplane. I'm taking off from the same old launch slope that I ran

down when I was hang gliding, but now I roll down the slope until I reach

flying speed, and then I'm off into the blue. Since this kind of launch isn't

being done regularly anywhere else in the world that I know of, some

explanation is called for.

Over the last four or five years I've designed, built, and flown a series

of gliders that fit my idea of an "airchair", essentially a garden chair with a

wing. This is an ultralight sailplane that allows the pilot to fly out in the open,

at low speeds, in a light, simple airframe that has been designed for basic

soaring and car top transport. My latest design, the Goat, can serve as a good

example. It weighs about 140 lbs. empty (complete with hand deployed

emergency parachute).This is well under the ultralight sailplane weight limit

of 155 lbs., so its airworthiness and pilot qualifications are not subject to

direct official oversight in the United States. I fly seated, strapped in place

with a four point seat belt, mostly out in the open air, like a paraglider pilot,

and usually in an insulated flight suit. This exposed flying is comfortable

because the Goat flies at hang glider speeds, a result of having about the same

wing loading as a hang glider (i.e., the ratio of its total flying weight in

proportion to its wing area is about the same as that of a hang glider). While

disassembled and folded, the glider can be transported on top of my truck on

my padded hang glider rack, with no special adaptations, braces, or other

baggage. Under perfect conditions I can assemble the Goat, single handed, in

just under twenty minutes.

The rolling launch idea originated while a few friends and I were

fumbling around on a training hill with one of my early prototypes, trying to

do some first flights. Hang gliders on wheels had been pushed down launch

slopes forever, so we tried pushing the glider down the hill and managed to

get some flights, but it was awkward and perilous to the pushers. Next we

tried the paraglider training technique of pulling with a short rope, but that

really didn't work at all, the pull wasn't fast enough and the pullers were in

the way. At last somebody suggested just letting it roll down the hill until it

flew, and to the amazement of all this seemed to work about as well as

anything. Eventually this became our standard launch technique both for

training and for mountain launching, since it was easy to do and practical as

long as the wind was adequate and the slope was smooth and open. The

requirements for mountain roll launching are (1) slow flying speeds

(presumably requiring a low wing loading) and (2) car top transport (the

trailers won't make it up the back roads). This season my weekend soaring

takeoffs have all been done by roll launching, mostly at Horse Canyon, a

mountain hang gliding site near San Diego, California. At Horse the launch

pad is two Goat wingspans long and drops about seventeen feet, adequate for

launches in moderate winds, with reasonable tip clearance from the rocks and

bushes along the sidelines.

At launch, I sit at the top of the slope, belted into the Goat seat with

my feet and nose skid down on the ground (the skid is held down by keeping

the control stick full forward, a precaution against wind gusts). In this

position I can wait for the best wind and traffic conditions before takeoff, a

launch potato once again, but with a few differences from my hang gliding

days. I have to persuade the launch helpers to let go and stand aside, since

unlike a hang glider I usually have good roll authority while just sitting there

in the wind. Good control and stability in turbulence also tempt me to go at

the height of the wind cycle, rather than waiting for the smoother but lower

velocity wind that follows it, to get the highest possible margin of takeoff

airspeed.

The launch starts when I call out "clear" and push against the ground

with my feet to raise the nose off the ground (or, if the wind is strong

enough, I just raise the nose with the elevator). Some fast foot action gets my

feet onto the rudder pedals as the glider begins to roll and slowly picks up

speed. I hold the wings at a level bank (controlled by sideways action of the

stick) and the nose down but clear of the ground (controlled by fore and aft

motion of the stick) as I steer straight down the hill with the rudder (foot

pedals). The sixteen inch diameter pneumatic tire gives me a smooth ride

down to the end of the slope, where I lift off the ground and dive over the

bush tops until I'm sure of some reserve airspeed. When I'm well clear of the

ridge I settle into a comfortable flying speed (30 mph. is fast in the Goat) and

switch to the coordinated flight control technique where the stick and rudder

are used together for turns.

This business of having to coordinate foot and hand control inputs, the

three axis control system, is one of the big differences between sailplane or

airplane flying as opposed to hang gliding or paragliding, and it's a major

obstacle to a quick transition from foot launching to airchair flying. When

student pilots first try to turn with a three axis system, they will usually try to

use just the control stick, with the result that the wing will roll but the nose

will not swing into the turn, it will just wallow in place or even go the other

way. You have to use the foot pedal (rudder) to yaw the nose into the turn as

well as using some side stick (ailerons) to bank the wing if you want any

kind of decent turn response at all. Of course, while using these two controls

in exquisite coordination, you also have to command airspeed by control stick

fore and aft position (using the elevator to control nose attitude), so three axis

flying can be a tricky business until you get the hang of it. The reward for

using mechanical controls is fast response and not having to use as much

muscle in the turns.

Out on the ridge and back above launch, I can mix readily with the

hang glider traffic because I'm flying at the same speeds and using the same

soaring techniques (typically at Horse Canyon most paragliders don't come

out until later in the day when many of the hang gliders have landed). I

haven't measured the performance of the Goat, but I think I'm flying about

like the average king posted hang glider, and maybe a little slower and

tighter, at times, in thermals. In a small thermal you'd like to fly as slow as

possible in order to stay close in to the lift core, but you can't just fly at

minimum airspeed because you still have to track and follow the lift, and that

requires maintaining maneuvering speed about half the time. Since the Goat

has both a light wing loading and good low speed roll control, I can work

small thermals comfortably and with good results.

Flying seated in a busy thermal, with whirling traffic above and below,

I feel a little like Harry Potter in the middle of a frantic quidditch match,

although, of course, our soaring traffic is usually less chaotic (we don't see

many people turning in the contra-gaggle direction). After a couple of lift

cycles, having taken in the view from whatever altitude is available, I might

be satisfied with my soaring and ready to fly away on a gradually descending

tour of the local flying area, cruising down for a landing.

Airchair landings are a lot like hang glider landings. The pre-landing

checklist is the same (check the local area for other air traffic, especially on

the horizon; check the wind direction; check to be sure the landing zone is

clear). I fly the same box landing pattern as always, at the same airspeeds,

and put out my drogue chute at about the same place (I'm a big drogue

parachute fan, I used them for every landing when I was hang gliding). In the

pattern, the ground path is adjusted in response to turbulence and lift using

the standard hang glider/paraglider practice, cutting in when low, swinging

wide and staying back when being forced up. This is contrary to the general

sailplane method, where you pretty much fly a fixed pattern and operate the

dive brakes for glide path control, and that's what a lot of the ultralight

sailplane pilots still would like to do, but I don't think it's going to work for

airchairs. The magnitude of lift effects at these wing loadings can be so great

that maneuvering and timing are the best practical method for controlling a

descent in the landing pattern . A dive break powerful enough to allow an

airchair to fly a fixed pattern under extreme conditions would itself be a

nemesis.

Landings are generally pretty easy, you just fly a casual pattern down

to grass skimming altitude and then sit there until the wheel settles onto the

ground. Hang glider flares and paraglider type braking maneuvers aren't

needed here, since you're landing on a wheel, not on your feet, and you can

just roll to a stop. If needed, the nose skid can be set down for a brake, but it

may grab on soft ground, like a thin bicycle tire in sand, and it can sometimes

produce a more abrupt halt than intended. A quick stop can rock the glider

forward, putting the tail high in the sky, an undignified way to end a flight.

The more stylish landing method is to slowly roll to a stop while lowering the

tail skid and both feet to the ground (since the wheel is located is at the center

of lift, the glider is only slightly nose heavy and it can be landed or launched

as either a nose dragger or a tail dragger, pilot's choice).

For ground tow or ultralight aerotow launches (which are what most

pilots elsewhere would be doing), airchairs easily fit into a hang glider

operation. The tow speeds are the same, you don't need a launch dolly, the

hookup is fast and simple, and there is little or no risk of a lockout or tumble.

On tow, one hand is always free, ready to release, and behind an ultralight

towplane the glider is stable enough that when the controls are released the

only result is a gradual climb above the level tow position. On the whole,

airchair towing is so casual you have to make yourself wake up and

remember that this part of the flight deserves your full attention because

things can go wrong.

Eventually there will be airchair accidents, probably similar to foot

launch accidents, more often a launch or landing bongle than a plummet from

the sky. In this low speed crash situation an airchair should provide superior

protection for the pilot by surrounding him or her with frangible structure,

which can absorb impact energy and help isolate the pilot from ground

objects. If, on the other hand, control of the glider has been lost at altitude,

and something like a plummet really has developed, it's time to go for the

hand deployed emergency parachute, which is mounted on the side of the

nose section down on the pilot's right. This is an ordinary hang glider

emergency chute and bridle in a deployment bag, rigged to be tossed out to

bring down the pilot and glider together in the usual way. The usual way, that

is, except that the bridle is set up to bring down the glider down tail first,

with the nose up in the air. The plan is that at the end of a drifting parachute

ride, the wing or tail will contact the terrain first and crumple up, protecting

the pilot from... discomfort.

My fellow local airchair pilot, Floyd Fronius, another old time hang

glider pilot, has reworked the Bug2 airchair biplane and is flying it on the

coastal ridge at Torrey Pines (as well as inland). His specialty is the airchair

cliff launch, which can be made from level ground near the cliff edge in high

winds, unassisted. Floyd also resolved our curiosity about what happens

when an airchair lands in shoulder high bushes (the result: nothing dire, just a

gentle forward pitch and nose bonk), and has defined the cliff launch concept

of "too much wind", which is when the wheel starts to rise off the ground

even though the nose skid is pressed firmly into the dirt. My own educational

misadventures involve landing in ruts, destroying wheels, overinflating the

tire (don't do it, it locks up the wheel), and various bent tubes.

The Goat airframe is constructed of aluminum tubing, bolted together

and braced with steel cable, similar to conventional hang glider construction.

For ease of home building, I tried to keep everything down at a "garage

technology" level, using readily available materials and hand held tools.

There are no welded or specially machined parts on the Goat. The covering

fabric is light aircraft polyester (Dacron), cemented in place and shrunk to fit

with a clothes iron, nominally the Polyfiber process except that I stop short

and don't use the ultraviolet protection (aluminum paint) or the cosmetic paint

layers. All the sensational details and the complete technical drawings are in

the public domain, free for downloading from my website,

http://home.att.net/~m--sandlin/bug.htm (or just search for "basic ultralight

glider").

Airchairs like the Goat (in particular, the commercial Super Floater)

are already flying at ultralight tow operations such as the Florida airparks,

and sometime in the future we may also see them flying at mountain sites and

training hills. Eventually, airchairs and faster ultralights might be a "third

wave" at local sites, joining the hang gliders and paragliders, becoming a part

of the local soaring scene. To become popular and be widely accepted,

airchairs will need time to develop all the usual stuff: commercial production

and certification, standardized instruction and ratings, and an organization

that provides unified representation, public relations, insurance, and

calendars. It isn't time yet to say "look out, USHGA, here we come!", but,

ultimately, using the same launch and landing areas would mean joining the

same organizations.

You might ask why anybody would want to fly some new type of wing

if it's heavier, more complex, and has no better performance that an average

hang glider. I'd answer that the main reason is just for the fun of it, for

novelty and adventure, and the comfort of upright seating is not lost on me

either. Also, I expect that a few generations of development would produce

some much improved aircraft, lighter, simpler, more practical, and higher

performance. There's no inherent reason why an airchair has to be heavier

than a hang glider (remember that the average hang glider pilot waddles up to

launch with about 110 pounds of equipment, only 20 or 30 pounds more than

I'm flying with now) and the performance can be increased (my airfoil is

primitive, and span limits have not been established). Another great potential

here is for crash safety, perhaps an opportunity for pilots to walk away from

many of the mishaps that would otherwise have added to soaring injury

statistics.

As a designer and home builder with no interest in anything

commercial, I have my own ideas for an ideal airchair, leading mainly in the

direction of light weight and simplified control systems. I look forward to

seeing more airchair flying, perhaps as a popular third choice for local

ultralight soaring, but mainly just to see what develops from this pleasant

offshoot of foot launch flying.