The Oz Report

We all like what we fly, whether it is objectively that great or not.  That said, my ATOS is by far the best hang glider that I have ever flown.  It glides the best, it climbs the best, it is the easiest to handle, and it lands great.  This says it all: my longest flight before ATOS – 165 miles (Exxtacy, Hobbs, NM.).  Longest flight (so far) with ATOS 232 miles (Manilla, NSW, OZ).

Just because I think it is the best, doesn't mean it's perfect (or that someone else won't come out with a better one soon).  There are lots of little things about the ATOS (and the pilot, for that matter) that I wish were a little bit better.  I thought that it would be useful to list them (and qualify them where I could), so as to open a discussion about these issues, and to push along the development of rigid wing hang gliders.

Oz Report readers will remember that I wrote a long article about the little problems with the Exxtacy not too long after I got it.  I also let Flight Design provide answers to my issues.  I published the whole give and take and other publications picked up on it.

I have sent this list of issues to Felix and Berndt at AIR.  I know that answering this article just cuts into their research, development, and production efforts, but then customer relations are also an important part of a total business operation.  I have included their answers to my points, so that I can present a balanced picture.

Felix's responses are in blue.

As I go through these points, I may not be clear on certain items.  Hopefully the give and take between Felix, Berndt and me will clear up any misunderstandings.

As I have not crashed my ATOS, and I didn't find any damage around the crack, I wondered where it came from.  Did it come from transportation, i.e.  while on a car top?  There was no denting at all around it.

It was very easy to fix, but it made me nervous about where such cracks come from.

Was there a small deformation or just a crack, can you sent me a picture with description of the location?

Perhaps these are entirely my fault.  It appears that rigid wing gliders (well this didn't seem to be the case with my Exxtacy) need to have extra special care taken when transported.  Padding that is good for flex wings is not enough for rigid wings.  Racks should be square (they are on my truck, and Gilbert's son's car that I have here in Australia) and not round tubes.  The racks should be well padded.

I've checked the Exxtacy and an ATOS prototype with honeycombs.  The spar with honeycombs looked at first much better compared to other ATOS D-spars with foam and similar hours (about 200 hours). Checking later however we found more and bigger impacts on the spar with honeycombs. Because it is easy to check, the D-spar with foam sandwich is more practical be cause all damage done to the spar is visible.

Never the less every carbon surface is sensitive to puncture loads and shouldn't be placed on an unpadded rack.  We have special foam pads in stock which work well when transporting the glider on your car or cable car. These pads are fixed around the glider back with Velcro and can be stored in the glider during flight.

We tested many different sail materials.  The ATOS sail (polyester) is not only lighter it showed less wear compared to a thicker sail we've tested.  The main reason for the damage you detail are locations were the sail touch hard parts like screws or carbon edges.  A thicker sail wouldn't help much. It is more important is to solve the problems at their source.

We spent a lot of time discovering all the points and padding them.  Your glider was one of the first gliders made and in some cases we didn't  detect the wear points in advance be cause the gliders before were packed little bit different or just had less flight time.

Thanks to the feedback of the first pilots we have improved this.  We have protections at pulleys , rib hinges and for the edge of the D-spar (see pictures below).  All this things are available as retrofit and the first customers will get this parts for no cost just be contacting us.  Additionally the very first customers who had the option price like you can get a new sail for manufacturing cost.

The ATOS comes with curved wing tips.  Take out the tip wands, and the tubes that connect to the end of the D-cells, and you have quite a bit of material that needs folding.  Even Felix couldn't figure out a good way to fold this when I saw him do it in Italy at the Worlds.

The problem is that you have to fold the material enough to allow the bag to go around the ends of the D-cell.  You also have to allow the spoilerons to fold correctly onto each other so that they can fit in the bag on top of the D-cells.  I sure wish there were a good formula from AIR for how to do this.

That's right it is a little bit difficult be cause there are many possibilities.

Enclosed you'll find the method which we determined to the most practicable.

This was a problem with the Exxtacy also.  If you don't rotate the turnbuckle all the way counter clockwise before spreading the wings (one of the first things you do when setting up the ATOS), the unclipped end of the turnbuckle will lodge itself inside the whack tube sleeve and knock off a piece of it on the left hand side (pilot facing forward).  Even if you do rotate it, it is easy for it to fall back and still hook the sleeve when you spread the wings.

I've knocked off three pieces of the sleeve so far, and I try to be sure that the turnbuckle is swung out every time.  I lost one of the A4 bolts (cylinders actually) that connect the turnbuckle to the leading edge of the D-cell.  I have replaced it with a hardware-store bolt while I await a new A4 bolt.  The replacement bolt holds the turnbuckle in even more and has helped me take the last two sleeve pieces off.

The nose turnbuckle has the advantage of being very flexible.  You can adjust it as your glider adjusts (you make measurements of the nose angle).  The problem is that often it is difficult to turn, and you feel that you may be straining the system.

I often find the tail end of the keel is sitting on the ground when I am attempting to tighten the turnbuckle.  The tail is supposed to be off the ground in order to allow the pilot to push down on the front of the keel and take tension off the turnbuckle while turning it.  The wing tips are supposed to be on the ground so that pushing on the front of the keel pushes the leading edges together as the wing tips are held in place.

I often find that this doesn't work, even on flat ground.  Perhaps the keel should be a little shorter.

I am a bit torn by this issue.  I like the solid nature of the turnbuckle, and worry about a cam just flipping open.  I know that the turnbuckle has been designed to fail before the carbon fiber rings on the D-cell.  I also know that the forces on the front nosepiece should be no greater than the sail tension.

When I inadvertently lost my A4 bolt to my turnbuckle, I was running with my ATOS in a field into a 20 mile per hour wind without the turnbuckle connected and the wings did not fold up (except about 1 degree of nose angle), so I have had some experience with the forces on the nose.

If Berndt and Felix want to say that it is just the case that the customer has to be careful, I can accept that.  But I do know from speaking with Oliver, who worked at the factory, that even Berndt and Felix would have the same problems as I do.

The turn buckle is a well designed part for its purpose, but it requires special attention like you mentioned.  Our new lever has several advantages.  You tighten the fitting before fixing the tip and ribs.  Then it is possible to insert the tips without holding the wing.  This method help you also to keep the sail clean and makes it more comfortable to insert the tips.

The fitting folds out automatically and can't damage a part if you forget to fold out the fitting.

It is not necessary to remove a bolt or ring (except one Quick Pin) so you can't lose them and you save assembling time.

The new fittings are already available as retrofit.  If you however used to the turnbuckle and don't care about the extra assembling time or comfort there is no need to change.

new nose catch saves assembling time (available as retrofit)

Reconsideration and reflections:

I have found that if I just move one of the wing tips forward when the turn buckle gets hard to turn, that this solves the problem.  There was no need to shorten the keel, or really complain.  I just had to know to walk out to the tip and pull it forward an extra couple of inches (after I had already done this before I started turning the turn turn buckle.

I wish the whack tube wouldn't tear a hole in the sleeve in a hard whack

I'm a bit torn on this one also.  I realize that the whack tube and its sleeve are supposed to be sacrificial items.  That is, you are supposed to replace them if you have a very bad landing.  I have had only two nose overs in my ATOS (I have wheels).  One was in a gust front at the Austrian Nationals.  The only damage was a bit of lengthening of the hole in the sleeve that allows the pop-up from the whack tube to lock in.

The present design is probably the right design, but perhaps we should get a couple of extra whack tubes and sleeves when we order a glider (just as standard items).  My whack tube itself has suffered no damage (other than a slightly bent pin, which I was able to straighten).  People who saw me flying my Exxtacy might remember that my whack tube didn't have a cap.  That way when I whacked, I could use the ground as a cushion, since I could dig a divot.

I've found the ATOS really easy to land, so the percentage of whacks is now quite small (say compared to the Exxtacy, which wasn't that hard to land).  The light weight of the ATOS contributes to the ease with which one can rotate it.  I also recommend not pulling on the flaps all the way for landing, as the ATOS (and the Exxtacy) pushes back hard when you flare if you do have them all the way on.  The only reason for full flaps would be a very short field.

That's right.  It is easier to flare with less flap. It is possible to land shorter with full flap deflection.  I personally prefer to use only full flap position for landing to have enough practice if I need it.

I don't know how much difference it makes, but everyone always wants to have a nice tight sail.  It may require that I tighten up the ribs (more on this later).  Maybe tightening the tip wands, but at the moment they appear to want me to loosen them up.

I have noticed that on one sail the Velcro keeps unhooking at the wing end of the D-cell.  Perhaps this sail is too tight (too close to the nose).  I guess that I am just looking for some guidance here.

Unlike flex wing gliders, the Exxtacy and the ATOS are very adjustable.  This puts some responsibility on the pilot to adjust them correctly, and responsibility on AIR to tell you how to adjust the ATOS.  You can adjust the nose angle, sail tension straps, zipper tension, sail placement at the nose and ends of the D-cell, batten tension, flap and spoileron placement, spoileron wire tension and stop point on the spoilerons.  A lot of adjustments to get correct.

The sail material shrinks a bit, as you can see by looking for a bit of carbon fiber leading edge near the nose of the glider.  At the factory there is no little strip of leading edge showing here.  Perhaps there is a way to adjust the sail so that the little folds are taken away, but I don't know what to do at the moment.

I don't know how much difference it makes, but everyone always wants to have a nice tight sail.  It may require that I tighten up the ribs (more on this later).  Maybe tightening the tip wands, but at the moment they appear to want me to loosen them up.

I have noticed that on one sail the Velcro keeps unhooking at the wing end of the D-cell.  Perhaps this sail is too tight (too close to the nose).  I guess that I am just looking for some guidance here.

Unlike flex wing gliders, the Exxtacy and the ATOS are very adjustable.  This puts some responsibility on the pilot to adjust them correctly, and responsibility on AIR to tell you how to adjust the ATOS.  You can adjust the nose angle, sail tension straps, zipper tension, sail placement at the nose and ends of the D-cell, batten tension, flap and spoileron placement, spoileron wire tension and stop point on the spoilerons.  A lot of adjustments to get correct.

answer below (tightening the rib)

The bottom trailing edge near the wing tip on one side is now a little forward of the top trailing edge.  This means that the Velcro doesn't line up.  One would think that the sail isn't fitted around the leading edge correctly.  I'll have to check this again.

Sticky Velcro is used on the flaps and spoilerons.  The problem is the Velcro is stickier than the glue.  If you try to undo the Velcro, it comes unglued first.  AIR has sewn some of the sticky Velcro on the flaps to overcome this problem.  Unfortunately they didn't completely sew it on the flaps or the spoilerons.  Take off a spoileron, and the Velcro tries to come off the spoileron first.

The Velcro at the outside ends of the flaps is not sewn, so it comes off.  I really can't get mine to stick now.  Perhaps if I had a really strong sewing machine I could fix this up.

The Velcro is now completely stitched and not as strong.  I hope you find somebody with a stitching machine there or you can wait for the next check at AIR or ALTAIR. If not we will replace the spoiler.  Till then you can fix with new sticky Velcro.  The standard Velcro is not as strong and not stronger than the glue.

Perhaps due to folding problems, the fiberglass pieces have split along the Velcro line.  In one case the split went along the Velcro about 4 inches.  I have tacked it back together with carbon fiber, although I could have used fiberglass.

Perhaps the spoilerons are too long to be folded easily.  Perhaps there just needs to be a little reinforcement there.

We reinforced this area with Aramid and additionally shortened the spoiler there so that it is little bit easier to pack .  The easiest way for fixing if this occurs is to use a self sticking sail or Velcro at this area from the bottom side.

area which needs special attention when packing the glider

critical area for packing (outer side of the spoiler)

At the new sails the bottom sail is longer and provides a higher tolerance for the adjustment.

The length and breadth of the flaps is a bit arbitrary to begin with, so it wouldn't seem to be a big deal to remove an inch or so from the end of the flap to keep it from interfering with the nearest rib.  The pilot can install the flap a tiny bit closer to the keel, and that solves the problem, but it seems like the tolerances are a bit tighter than they need to be.

I was able to get rid of any waves in the flaps by unhooking the flaps and re Velcroing them back into the sail.  I believe that John Reynoldson was referring to the wavy flaps on my ATOS when he said that there were some minor problems with the ATOS trailing edge.  It was easy to fix.

But once I fixed it, I noticed that the end of the flap was too close to the nearest rib.  I could undo the flap again and reposition it, but it didn't seem to be that much off to begin with.  Perhaps AIR wants to make sure that it isn't required that the flap be exactly in the right spot.

The flaps are in the right place when they didn't interfere each other in the middle and when the distance between the flap is not wider than about 10mm (we adjust it with 5mm).  The flap at the very first Atos like you have were a little bit longer than now.  If you shorten and round the outer side of the flap you will get the same shape like we have now and it will be easier for packing.  A good distance between flap end and rib is about 6cm.

AIR puts in a shrink-wrap piece that is supposed to keep this from happening, but it is now wearing out on my ATOS.  I expect that the pulley will soon flip and cause the rope to wear.

Even if this shrink tube wears the pulley will not flip over if the knot there is tight enough.  We have an extra check for this now.

Perhaps it got a bit wet.  It is made of bakelight.  The other pulley is fine.  The other pulleys are metal, but they need to be greased or the bearing don't work very well and the rope wears.  I've put some Phil's grease on all my pulleys.  I noticed rope wear around all the pulleys.

AIR sent me two end plugs that fit into the ATOS control frame hardware.  I fashioned two shims that allowed the plugs to form a tight fit with the sleeves in my Wallaby Ranch, Rhett-and-Ryan Exxtacy aero-steel base-tube.  All I had to do was bolt the plugs into the base tube using the already perfectly positioned holes, and I had an aero base tube.

Perhaps it got a bit wet.  It is made of bakelight.  The other pulley is fine.  The other pulleys are metal, but they need to be greased or the bearing don't work very well and the rope wears.  I've put some Phil's grease on all my pulleys.  I noticed rope wear around all the pulleys.

Water should not be a problem for the pulleys.  However while these pulleys are built to an aeronautical standard, the quality is not perfect.  Perhaps one pulley has a different look because we sometimes smoothen the surface if we find irregularities at the check.  If there is a damage at the pulley especially at the area where the control cable is connected the pulley has to be replaced.

Perhaps it is just an issue of getting the proper adjustments, especially as the sail shrinks a bit, but at the moment the wing tips are very tight (too tight?).  It is quite a struggle to get the lines on and off.

I really enjoyed the cams on the Exxtacy.  They were inside the sail and they were easy to use.  I sure hope that Felix decides on how to deal with this issue.

There is a lot of metal in the nose, and it wears out the bag.

Perhaps it is just an issue of getting the proper adjustments, especially as the sail shrinks a bit, but at the moment the wing tips are very tight (too tight?).  It is quite a struggle to get the lines on and off.

I really enjoyed the cams on the Exxtacy.  They were inside the sail and they were easy to use.  I sure hope that Felix decides on how to deal with this issue.

The news Atoses have cams which work well and provide a possibility to adjust the sail with different tension.  This levers are available as retrofit.

Reconsideration and reflections:

The problem I was having was due to the fact that the sail had shrunk about 3/8" along the span of the wing, and I hadn't increased the length of the string on the tip wand, or moved the sail away from the nose by that amount.  The tension kept getting tighter and tighter, so it became quite difficult to put the tip wands on.  Once I started adjusting the sail to make up for the small shrinkage all thes problems went away.

I do like my thin little steel speed bar, but I can't put the wheels with brakes on it because the hubs are too small to go around the bar (at least it seems that way to me).  I currently have to use my other thin plastic wheels that don't have brakes on them.

Yes we have a carbon speed bar available with skids right now.

Fortunately the design was changed for later ATOSes so that you didn't have to pull the pit pin out quite as far.  I hope those pilots like this change.

I must say that the hardware on the ATOS is for the most party very streamlined, elegant, and well thought out.  If it wasn't for this spoileron wire connection problem I would say that these corner brackets are the best I've ever seen.

My ATOS is a bit older so that it is more of a hassle.  You have to pull the pit pin almost but not quite all the way out of the plastic piece at the bottom of the down tube, in order to slide in the spoileron wire.  You have to do this while the glider is completely set up.  It is a pain.

Fortunately the design was changed for later ATOSes so that you didn't have to pull the pit pin out quite as far.  I hope those pilots like this change.

I must say that the hardware on the ATOS is for the most party very streamlined, elegant, and well thought out.  If it wasn't for this spoileron wire connection problem I would say that these corner brackets are the best I've ever seen.

connection of the spoiler cable (important: safety cap must be on to secure the pin and to keep the end of the pin clean)

The ATOSes look beefy at the nose, perhaps even beefier than the later Exxtacies.  It gives one the perception of a safe joint connecting the two leading edges together.

It is very hard to say something about the strength from the look but the design load of the Atos is the same as at the Exxtacy and some things have received an additional safety factor like this root connection of the spar.

I saw something similar happen to one of the ribs on an ATOS at the Worlds.

I was able to repair the end of the rib using carbon fiber, epoxy, and filler.  We'll see if this lasts.  Perhaps we could get some guidance on how to fix this problem.

The ends of the ATOS' carbon fiber ribs seem to be made of some other material.  They are formed into U-shaped slots that fit the metal cams that connect the sail to the ribs.  The end of the outboard rib on my right-hand d-cell flaked off so that the cam wouldn't go on it any more.

I saw something similar happen to one of the ribs on an ATOS at the Worlds.

I was able to repair the end of the rib using carbon fiber, epoxy, and filler.  We'll see if this lasts.  Perhaps we could get some guidance on how to fix this problem.

At some of the very first ribs the fibres didn't go to the very end at the area where the metal cams are fixed.  If the trailing edge touch the ground at a hard landing the metal cam of the outer rib can damage the end of the rib.  After detecting this we changed the lay up process and additionally we used new designed metal cams which should fail before the rib fail.  With this combination we haven't had a failure there.

AIR is well aware of this problem, and one fix is to install little pins that break off first.  I wonder if they send out a bunch with each new ATOS?

The third rib was an outer rib.  It also was quite easy to fix and hasn't caused a problem since.  This rib is hinged so it should take any impacts.  I saw another rib like this one broken at the worlds.

Fixing ribs is very easy and quick.  I flew with the broken number nine rib for a week before fixing it as it had just delaminated and otherwise was fine.

Two of the ribs were broken at the Worlds.  Dave Sharp added a bunch of carbon fiber to them when he fixed them, and there are been no problems since.  These first two were the number eight ribs at the ends of the D-cells.  They are easy to break if your flair isn't perfectly even and one wing touches before the other.

AIR is well aware of this problem, and one fix is to install little pins that break off first.  I wonder if they send out a bunch with each new ATOS?

The third rib was an outer rib.  It also was quite easy to fix and hasn't caused a problem since.  This rib is hinged so it should take any impacts.  I saw another rib like this one broken at the worlds.

Fixing ribs is very easy and quick.  I flew with the broken number nine rib for a week before fixing it as it had just delaminated and otherwise was fine.

This is a very sensitive location for rigid wings.  On one hand the wing has to be stiff in order to not change the pitch up moment but on the other hand it has to be flexible or strong enough too not break during a hard landing.  The first Atos rib were not very strong in order to protect the D-spar.  We reinforced this rib after noticing this week point and fixed it with a special bolt to get a predetermining breaking point there.  This rib bolt fails before the rib or the D-spar get damaged.  If the tip would be stronger the outer rib wouldn't fail cause the load is taken by the tip and introduced the load to the D-spar, which can fail like it happened at very hard landings on the tip of the Exxtacy.

We've had good experience with this solution at the Atos now and haven't had a broken rib since, considering the last four month and about 150 gliders.  However it still could be damaged and is designed to fail before something fails at the D-spar. It must be checked after a hard landing.

The ATOS comes from the factory with really pretty tight ribs.  The tightness is adjusted by a piece of Velcro that sets the placement of the cams on the rib ends.  It would seem that you want to adjust the Velcro so that the cams can be put in place without undue stress on your fingers and arms, but as tight as possible.  I want to be able to just flip on the cams with my thumb without creating any creases in my thumb.

To tighten the sail well it is usually necessary the tighten the ribs with different tension.  The tension should increase from the root rib no.1 to the tip rib no.8+9.  We set the ribs a little bit stronger when the glider is new.  The reasons is, that the sail and seams get stretched a little bit and after the first flights the chance is pretty good to get the right tension.  However this only works well when the temperature and humidity changes are not too big.  Under very warm and dry conditions it will be necessary to adjust the sail to be a bit more lose and under cold and wet conditions it will be necessary to retighten the sail.  If the tension is too high you get wrinkles like it is shown in the picture below.

You can see in the picture below the right way to tighten and untighten the ribs .  Two things are important: 1.  Be sure that the cam fits correctly before turning.  2.  Never pull or push at the rib, only the metal lever.

 tightening the rib wrinkles in the sail when the tension is to high

After some flights or under different conditions it is also necessary to tighten the webbing which connect the sail to the keel.  If it is too tight you will have wrinkles and the nose fitting is hard to close.

To adjust the tip with the right tension we tighten it till the trailing edge gets lose and loosen it again to have high tension with a tight trailing edge.  The tension there is usually quite high.  With the new levers you get this tension easy so it is good to check the tension at the trailing edge in order to not overload the sail or rivet.  Without lever it is hard to get to much tension.

checking the tension at the trailing edge

There are rises in the top surface of the trailing edge as the sail goes over the ribs.  The top Velcro doesn't contact bottom surface Velcro at these points.  There is not a smooth trailing edge.

It should be smooth but there are small rises be cause there is no Velcro close to the rib to have a better handling when opening the cams.  (hope I understand you right here )

Unlike on the older Exxtacies, the Velcro on the ATOS doesn't come unglued on the nose.  This is a great relief.  I personally epoxied the Velcro on my Exxtacy, so it is good to see this on the ATOS.

This makes it easy to examine the leading edges (which unfortunately appear to need regular examination).

It's very easy to repair carbon fiber

Some of my repairs even look good.  Took me about half an hour to repair the large crack in one D-cell.  I'm getting better at this, but with a little practice anyone can do it.  I carry around a small repair kit with epoxy and carbon fiber from Flight Design.  Every pilot should obtain a repair kit from AIR or Flight Design.

I just decided to loosen the zipper at the starting ends, as I could never get it to start zipping otherwise.  Felix says to leave it tight, but that didn't work for me.  I assume that as the sail shrinks you need to loosen the zipper a bit.

That's right.  The zipper should be lose to get an easy start then tight and a little less tight to the end.  This is usually the best setting in order to avoid wrinkles.

Reconsideration and reflections:

As my problems with the zipper and the tip wands were due to the fact that I hadn't adjusted the sail the account for its mall shrinkage.  Once I did that, everything worked well.  It was easy to adjust the Velcro on the zippers.  If the sail shrank much more (which I don't think it will do), I would appreciate having 3" on Velcro on each side of the zipper instead of just 2".

Thanks for your report and feedback, your glider was one of the first and many things are changed with thanks to the good feed back of many Atos customer.  All things we changed are available as retrofit.  A new sail for the very first customer is available for the manufacturing price and the pads for no cost.  An other update is the new nose cover (see picture below) which covers the nose tube and improves slightly the aerodynamic in this area.  Enclosed more pictures of some new details which are available.