Challenger Modifications
by
Mike Round

Challenger Light Sport Aircraft

By:  Mike Round

Blind 1/8" rivets are used to attach the tubing to the cross members (Photo 4) and aluminum angle to the 1/2" bottom stringers.

After applying the bottom fabric, the tubing creates a subtle "keel" where water can drain away from the bottom stringer tubing on the sides (Photo 5) and drain out through the seaplane grommets in the bottom (Photo 6).

438

437

435

Here are a couple photos of the plates that Gary Freitag and I made to
protect the longerons from damage when making a less than perfect water
landing on Puddle Jumper floats.

The bearing plate was cut from a 1/2 inch thick nylon sheet. (Photos 438 and 437) The bearing surface of the plate was shaped by using a 2 inch hole cutter on a drill press. I cut about 1/4 inch, or half way, through the
thickness of the bearing plate with the hole cutter for the full length of the contact surface. I added an additional 1/4 inch bolt to stabilize the
plate on the longeron. The size and dimensions of the bearing plate are
arbitrary but the addition of the plate increases the bearing surface on the longeron greatly and provides relief from the concentrated pressure point of the forward stainless steel stabilizer bracket. At the very least, be
advised to put the large fender washer provided by Puddle Jumper between the stabilizer bracket and the longeron. the instructions do not make this clear and I had mistakenly put the fender washer on the inside between the longeron and the nyloc nut. (Another Challenger owner did the very same thing and sustained the exact same damage as I encountered in the first couple of hours of flying on floats.)

I also put a nylon Super-Tough ultra light saddle from Aircraft Spruce on
the longeron on the inside before adding a washer and nyloc nut. (photo 435)

In addition to providing safety from damaging the longerons, it provides and excellent support bracket for the morse control cables which tend to flex and rip the outside fabric. It's an easy modification and I believe that
it's good insurance from damaging the longeron.

Here is what I did to give a quick check on the position of my flaperons. Trimming in flight is a common necessity but landing with reflex flaperons can be dangerous if you don't know at what speed you'll be stalling the plane. The Challenger II on Puddle Jumper floats with a Rotax DCDI 503 (i.e. heavy) can stall at 50 mph when the flaperons are fully reflexed (trailing edge up). Attached are pictures showing the cable control wire attached to the flaperon control horn and snaked down to the starboard aluminum downtube in the cockpit. The gauge end has a copper sleeve swaged to the wire forming a small loop to which I fastened a spring to keep tension on the cable. The gauge itself was made from printed computer graphics and backing made from velcro was glued to the paper gauge. This adhesive velcro allowed me to adjust the scale to the neutral position after everything was in place. The clear plastic tubing protected everything on the down tube for those times when I needed the "sissy bars" in turbulence! The position of the gauge at eye level gives a quick easy reference to the flaperon position on landing and is on my landing check list. Good flying.   

Mike Round

1) Cut the head off a bolt that is the necessary size and thread to accomodate the threaded insert to the plastic friction knob ( this item I found in specialty hardware at the local hardware store), 2) install a nyloc nut and washer on the inside and sandwich the aluminum throttle bracket between the nyloc and another washer, lock washer and a regular nut and tighten securely 3) Drill out the gray original plastic spacer to allow the nut and washer assembly to fit inside so the spacer sits flat against the aluminum bracket 4) install the throttle arm and a large fender washer followed by the threaded friction knob 5) install the compression spring and washer and finish off with an acorn nut. The spring keeps all the components from vibrating loose. This modification works great and it's low profile and the knurled knob is big enough to be adjusted when wearing gloves.

Mike Round