National Ultralight Inc.
Exclusive Canadian Distributor

Advanced Ultralight Aircraft

Intro | General BuildCoverPaintRigRegisterFlyMaintainStore 

Home Page | Canadian Support Section Contact Us

Canadian Challenger Owners Manual
- Building -

The information contained in this document is intended for the sole use of Canadian Challenger owners and is strictly proprietary and confidential.

One of the biggest benefits of building a Challenger is that all of the difficult fabrication work has been done for you professionally at the factory, but don't let this lull you into skipping the instructions - you need them!

Make sure you take the time to carefully read all the instructions before proceeding with the assembly. What may appear obvious, is not always and as new improvements and options have been added to the design, the addendum to the instructions that accompany those items may supersede the original manuals. Only by reading and understanding all the instructions can you be sure of avoiding problems.

Do not make modifications to the airplane. The airplane is a well known and thoroughly tested commodity in its standard form and modifications, however minor could put you at risk. There have been instances of relatively innocuous modifications having both direct and indirect consequences, some of which take considerable time to show up. Modifications of any kind will also void the Certificate of Conformity for planes registered in the advanced category.

Try to resist the compulsion that so many succumb to - adding everything but the kitchen sink to their airplanes. The lighter you keep the plane, the better it will perform. It will go faster, stall slower, climb steeper, carry heavier loads, use less fuel, go farther and take off and land shorter. In the case of the standard wing 2-seater it will also soar better. We have one of the few designs that is quite capable of soaring. Don't spoil it! If you don't really need to add it - don't. Every extra pound you save means extra performance.

It is vital that you be aware of the extreme importance of weight and balance. Do not randomly add equipment that will make the plane excessively nose or tail heavy - it could lead to an uncontrollable aircraft. The Challenger II in its basic form requires a minimum front seat weight of approximately 160 lbs. Adding a long range tank, electric starter or other equipment behind the center of gravity (roughly the middle of the back seat) will require greater front seat weight. Place weight forward (i.e. the battery in the nose) or ballast (secure thin barbell weights under the front seat cushion), to keep the aircraft properly balanced.

Typically for pilots weighing 160 lbs. or less, where a choice of placement is possible, every effort should be made to add weight as far forward as possible. For pilots in the 175 - 200 lb. range, some effort must be made to keep weight forward, but it will be less critical. Placing the battery on one of the longerons alongside the pilot's knee, is likely sufficient and will also be easier to access. If the pilot is significantly over 200 pounds, you may need to consider installing the battery under the engine or in extreme cases, adding weight to the tail.

Wherever the battery is installed, you will need to make a secure mounting point for it and run the wiring from that point. A sealed motorcycle or Skidoo battery (available at Canadian Tire) is ideal as the weight is quite low and there is no possibility of leakage.

The Challenger has an ingenious feature that lets you easily check the C of G with the plane on wheels or skis. When ready for flight with the pilot (and passenger) aboard, the nose wheel should stay in contact with the ground with the engine turned off. If the plane wants to sit back on its tail wheel (the most likely scenario), the front seat weight is too light. It was designed this way so that airplanes out of CG can not be steered to the runway and accidents will be avoided.

Before you cover your airplane, consider whether you will want to install a heater. If you plan to add one to a 503 powered Challenger, you will need sufficient clearance between the Rotax cowling and the fuselage formers below the engine. Depending on which type of heating system you plan to install, you may want to drill out the top formers and reinstall them lower to allow more room for the heater and ducting.

You may also want to install a thin triangular aluminum sheet between the two rearmost down tubes (just in front of the motor). This will reflect engine noise away from the cabin, help retain cabin heat and provide a convenient mounting place for the solenoid and voltage regulator if you have a starter motor installed.

As you receive it, the Rotax engine out of the box may have the carburetor intakes installed the wrong way around. If yours are installed incorrectly (with the carbs not vertical when viewed from behind) simply undo the two Allen head bolts and rotate each manifold 180 degrees, then reinstall. When installing the muffler, use Loctite anti seize compound on the ball joints.

If you are installing an electric starter on your Rotax motor, please take a moment to check the engagement of the starter gear to the flywheel gear before trying it with the key. We have found that not all Rotax flywheels are created equal. Some are slightly thicker than others which may cause the starter to bind or not engage properly. When this does occur a thinner blue anodized spacer must be used for the electric start installation.

This topic is covered in detail by the GPL Starter Installation Instructions which come with the electric start package. GPL will replace the spacer with a thinner one at no charge. In the past some owners have shaved the blue anodized spacer a few thousandths of an inch. If you choose to shave the back side of your spacer, you will also have to reduce the length of the bolts that attach it by a similar amount. If left at full length, the bolts will protrude through the flywheel and could cut ignition wires behind the assembly. If you choose to shave the front side of the spacer the bolt heads may no longer be flush and could cause other fitting problems. We suggest you avoid the complications of shaving and simply have GPL send you the correct size spacer!

The standard Challenger kit comes with a small wooden blank for the instrument panel. This is intended to be mounted at an angle, rather like a panel on a boat. If you wish you can make a larger panel from wood or metal and mount it vertically as would be done in many airplanes. A popular choice of aluminum is 1/16" (0.063") sheet from a blank 24" by 14". Aircraft grade is not necessary for this so material may be sourced at your local machine/fabrication shop. Another source would be Metal Supermarkets who sell metal in small quantities via stores across Canada or shipment direct to your door:

Your Challenger comes with two individual ignition keys, one for each system, and a separate button for the electric starter. If you would prefer an aircraft style ignition switch (Off, Left, Right, Both, Start), they are available from numerous suppliers including Sky Sports 1-800-AIR-STUF. Specify for a Rotax engine.

Rare instances of fuel line squeeze bulbs failing and blocking fuel flow have been reported. To avoid the possibility of this problem ever occurring, you can install 'Y' connectors and a short length of fuel line to bypass the bulb. You will however have to pinch the bypass line when using the bulb.

Similarly there have been rare instances of the Rotax fuel pump eventually failing. To avoid the possibility of this occurring, you can install a small in-line electric fuel pump.

Do not puncture the nylon fuel tank to install a fuel drain. It is extremely likely that the joint will leak or burst in the case of an accident. Use a filtering funnel when adding fuel, keep your tank full to avoid condensation and periodically drain and clean your fuel tank. ('Mr. Funnel' is available from many sources that will trap dirt and water).

If you chose tinted glass, you may wish to paint the aluminum door frames black before assembly as well as the forward and seat down tubes where exposed behind the glass. This will make them disappear and will enhance the smoked appearance.

When you are ready to assemble your doors take all the pieces including the lexan out of the boxes and examine them carefully to locate holes pre-drilled at the factory. If you do not do this you may drill holes in the tubes and then discover they don't line up with the holes already in the lexan.

Also on the doors, you will get a better final fit if you use clecos (temporary rivets available from aircraft suppliers) and do the assembly on the aircraft. The clecos will be useful throughout the assembly. A couple of dozen 1/8" and a dozen 3/16" with cleco pliers will be a good investment. While you're at it, get a deburring tool to clean up any holes you drill before final assembly.

After you have installed the restraining bungees on the doors, take a pair of needle nose pliers or vice grips and crimp the adel clamps that attach each bungee to the door. To not do so is to risk having the door open in flight.

The aluminum bracket supplied by the factory that latches the door to the wing, holds the Lexan in contact with the lower wing surface when open. In time, vibration from the engine will cause scratching of the Lexan. We recommend that you fabricate new, longer hangars that keep the Lexan from contacting the wing.

If you would like ventilation while you fly, the easiest way to do it is to simply wedge the front of the door open in flight with the white nylon retainer between the door and the outside of the windshield on one or both doors. You will have to add some form of additional retainer however, as the doors will blow open at higher speeds without positive locks.

If you plan to fly your plane in a saltwater environment then you may wish to take steps to minimize corrosion. Click here for more info.

Pay very careful attention to aileron hinge placement as incorrect installation may result in limited aileron travel when the flaperons are fully down. The hinges mount with the concave sides against the tubes and the hinge's pin should be 1/8" above the centerline of the rear spar and at the centerline of the aileron. A useful trick is to trial rig the ailerons using hose clamps through the gap in the hinges before covering the wing. This will help you find the proper placement which must allow for full aileron down travel and clearance of the rear strut attach bracket bolt heads even when the flaps are fully deployed.

We have heard favourable comments about a technique for placing the hinges which was suggested by a US builder's web site. Click here for details.

The Challenger's 2.6-1 reduction drive is designed to accommodate props from 2" to 2.5" thick. For this reason the prop bolts supplied by Quad City are 3 1/4" long. The wood props from Tennessee and GSC most often seen on Challengers with 503s are 2 1/4" thick and for those the bolts are perfect as is.

Other props - Warp, Ivo, Powerfin, etc - are different. Some are thicker - the Warp Drive standard hub is 2 1/2" which is not a problem since there is enough thread on the 3 1/4" bolts. Some props are thinner - the Warp Drive HP-L hub we use with our 582 Power Pack is 2". With 2" thick props the prop bolts are too long and if no special action is taken they will bottom. In this case the prop will not be tight. Not good!

The prop bolts are custom manufactured grade 5 cadmium plated with a coarse thread and an extra long grip. Do not substitute the prop bolts from Quad City with seemingly perfect length bolts you found at your local hardware store or even at an AN supplier! While AN5H-27A is about the length required for the Warp Drive HP-L hubs, and it has a drilled head for safety wire, that bolt has a 24 pitch thread. This will not work in the Quad City redrive, which takes an 18 pitch thread. Also the exact grip length is essential.

To prevent the bolts from bottoming with thinner props you can do any one of the following:

- Add 5/16" AN washers under the heads of the bolts. If you have the standard red face plate you will likely need 4 washers under each bolt head to prevent bottoming. If you have a spinner with a thicker face plate you may only require 3 washers under each bolt head. This is not pretty but it works.

- Get another red prop face plate and install it on the opposite side of the prop from the first one - ie between the prop and the round plate screwed onto the upper pulley of the redrive. You might still need a washer - most people install one anyway to stop the heads of the bolts from scratching the prop face plate.

Whichever approach you choose do a trial assembly to make absolutely sure the bolts aren't bottoming. If they bottom then the prop won't be tight!

The 3-blade Warp Drive prop shipped with the 582 Power Pack is ground adjustable. Instructions and a protractor come in the package with the prop. You can set the prop anywhere between 12 and 14.5 degrees. A smaller angle lets the prop turn faster which favours takeoff and climb. A larger angle gives the prop a bigger albeit slower bite which favours cruise.

We prefer 12.5 to 13 degrees since this delivers enough rpm to be in the better part of the power curve but not so much that it slows cruise. The 582 power band is quite wide so we don't bother to change pitch between floats and wheels or skis.

Warp's instructions require you to retorque all bolts after 1 hour of operation and then periodically as part of regular maintenance. Make sure you do this!

There are places where you will find the manuals have not kept pace with the design improvements to the airplane. In spite of ongoing requests for a rewrite, none have thus far been forthcoming. This is a large part of the reasoning behind this booklet. You may still have unanswered questions about the building procedure. We have a strong network of extremely capable professional builders who have put many Challengers together for our owners.

None of them work for us, but all are very experienced builders, genuinely interested in the Challenger and willing to help if they can. We ask that you realize that they earn their income by the hour, so if you are going to take them away from their work to answer your questions, please be brief and consider sending them $20 as a thank you for their time and support. Also please consider work hours and time zones when making a call.

- Bernie Rector - Lawrencetown, Nova Scotia - 902-584-3302
- Bill Bryan - Markham, Ontario - 647-218-5403
- Dan Pandur - Westlock, Alberta - 780-349-4159
- John McDermott - Salmon Arm, British Columbia - 250-832-1000

Finally, don't be intimidated by the prospect of building your airplane. Take your time and as the expression goes, "measure twice and cut once". You will find it to be an educational and vastly satisfying experience. Unlike the model airplanes you may have built in your youth and proudly hung from the ceiling, this one you are personally going to hang from a cloud. Enjoy!


Home Page | 10 Best Reasons | Airplane | Experience | Owners | FAQ | Company | Contact Us

To learn and see more order our comprehensive information package and video!

Copyright National Ultralight Inc. All rights reserved.