New Challenger XS-50, XS-65 and XL-65

National Ultralight releases three exciting new Challenger Ultralight models

At the Montebello 2011 Challenger Fly-in and Conference, Bryan Quickmire of National Ultralight gave an informative 1 hour seminar detailing all of the new features and enhancements included in the new XS-50, XS-65 and XL-65 Challenger Light Sport Aircraft models being marketed in Canada.

These 3 new models have some interesting new developments that really enhance the performance and versatility of the Challenger aircraft.

The XS-50 model is powered by the venerable and cost effective 50HP Rotax 503 air cooled engine. This aircraft has the clipped 26 foot wings with fibreglass Hoerner style wing tips. The short wing span gives it a very high maximum level cruise speed of 95 mph and a Vne of 120 mph. The XS-50 is designed for use on wheels and skis. It is not suitable for use with floats due to the short wing span. The gross weight is 960 lbs.

(Go to the bottom of this page for a summary of the test flight of a brand new XS-50 that we completed here at Lake Aviation)

The XS-65 is the same as the XS-50 but is powered by the larger 65 horse power Rotax 582. The larger Rotax 582 will give it quicker take offs, faster climbs, and better hot and high performance. It also has clipped wings and is therefore intended for use on wheels and skis.

The XL-65 model is powered by the larger 65 HP Rotax 582 engine which is liquid cooled and has a radiator mounted above the wing. This aircraft has the longer 29.5 foot wing with fibreglass Hoerner style wing tips. The cruise speed is about 85 mph and Vne is 100 mph. The larger high lift wing enables the XL-65 to be used on wheels, skis and floats. The gross weight on this model is increased to 1060 lbs because the fuel tanks are now located in the wings reducing the load on the fuselage. This new feature frees up a large amount of space for luggage behind the rear seat. These features alone make the Challenger XL-65 a true 2 person cross country aircraft suitable for overnight trips.

All of these new Challenger models also have the following upgrades and new features:

1. A beefed up yet more streamlined landing gear. The landing gear sockets inside the fuselage are larger with additional welded steel cross braces. There are longer any external drag wires. The additional cross braces also strengthen the belly of the aircraft at the center of gravity. This will strengthen the belly for lifting the aircraft during landing gear changes. (See photos at bottom of page.)
2. The tail is the most noticeable change on these models. The highly swept tail is 10″ taller with 25% more surface area. This will make the aircraft much more directionally stable in the yaw axis. In other words, it will be easier to maintain on a constant heading.
3. The aileron bell crank is modified so that the ailerons function as “differential” ailerons. This will all but eliminate adverse yaw. Thus the airplane is even friendlier to fly especially for those who are used to GA aircraft. (See photo at bottom of page.)
4. The cockpit wind screen, side rails, and doors have been redesigned to make cockpit entry much easier. The wind screen stops about 4″ closer to the nose compared to previous models. This gives more room for the pilot to climb into the front seat. The side rails are lower all the way to the back of the rear seat. All this combines to make the aircraft easier to climb into. A third door modification is available if the pilot desires even more room to climb into the front seat.
5. Additional streamlining is included in these new kits. The landing gear legs are smaller in diameter and are made from solid aluminum shafts. There are no external support wires for the landing gear legs. They also have full length streamlined covers. All of the jury struts on the main wings are now streamlined as well as the small struts supporting the horizontal stabilizers in the tail. The main wing struts are also streamlined.
6. Hegar hydraulic brakes are standard. The hydraulic lines are hidden beneath the streamlined gear leg  covers. There are no longer any exposed brake cables. This really cleans up the appearance of the aircraft around the landing gear and the cockpit.
7. The cruise and max speeds are all increased due to all of the streamlining.
8. The interior design of the wings has been changed to increase strength. A light weight leading edge wrap is now supplied as standard from the factory. This eliminates the scalloping effect on the leading edge of the ribs seen on previous Challenger models. The bottom surface of the wings now features ribs every 18″. This will eliminate drag also. The maximum aircraft load factors are also increased to +6G/-4G due to the stronger wing design.
9. The wing struts are now equipped with a high load fastener kit. This kit spreads the forces acting on the bolts that hold the struts over a much larger area. This greatly increases the strength of the connection of the strut to the longeron in the fuselage.
10. The stronger wing enables two 10 gallon wing tanks to be installed. This not only increases the range of the aircraft but also enables a higher gross weight on the XL-65 model because the wing carries the fuel load not the fuselage. The new wing tanks are standard on the XL-65 and optional on the XS-50 and XS-65. With the wing tank option, the fuselage can be equipped with more storage volume than ever before.
11. The instrument panel has been upgraded also. A precut aluminum panel is now supplied. A full suite of analogue instruments is now standard including ASI, altimeter, tachometer, hour meter, dual EGT, dual CHT, and water temperature (XS-65 and XL-65).

Challenger II Classic Comparison to XS-50 Light Sport

A Classic Challenger II is shown below in white. The new XS-50 Light Sport model is shown in blue/yellow. Click twice on the photos to see a larger view:

Contact Us at Lake Aviation if you would like us to quote you on building one of these exciting new aircraft.

Questions on the new Challenger XS-50, XS-65 and XL-65 light sport aircraft:

A visitor to this site asked about the new higher gross weight of the Challenger XL-65 model. The reply I sent to Michael was probably a bit more than he expected. He probably did not want the one thousand word essay that I wrote. Ah,well. When I get talking airplanes, I sometimes get carried away.

Question:

I noticed in your Modifications section that you cautioned about adding too much weight to the Challenger. Now that the XL 65 has a gross weight of 1060 lbs, do you think that the 582 will start to be taxed like the 503 was previously at 960 lbs.? What do you think the performance will be if you’re on floats, two up, at high altitude on a hot day at close to gross weight?

Answer:

The caution with our ultralights is always to keep the empty weight as low as possible. Many builders are adding a lot of equipment that adds unnecessary weight to the aircraft as it sits empty. This reduces the payload and performance. However, demands and requirements have changed over the years. Modern Challengers are heavier than they used to be. The manufacturer has recognized this weight growth and has responded with increased maximum gross weights over the years. These have increased from the original 850 lbs to 960 lbs and now to 1060 lbs with the XL-65 model. The higher gross weights are due to changes in design in a few key areas of the airframe.

The original Challengers back in 1983 had no doors, no brakes, no streamlining fairings, no radio, no electric start, no battery, no lights, no heater, and so on. They were very light weight at about 350 lbs empty. A typical Challenger II now weighs about 450 lbs empty, some even more. (Mine is 470) Many of these options that I have listed are now considered mandatory by owners especially in Canada and the northern United States.

The problem with the Challenger and other similar 2 place ultralights was that when equipped with floats and all of these other options, they essentially become a single seat aircraft during the hot summer months because of density altitude – hot and humid and heavy. Add to this a full 17 gallon fuel tank and a bunch of other modifications and you get what is called a fat ultralight. Performance suffers and even becomes dangerous.

The 65 HP Rotax 582 helps eliminate this problem with extra power. A Challenger with a 582 on floats flies like a Challenger with a 503 on wheels. In effect it flies like it is not on floats at all. That is remarkable since floats weigh about 110 lbs. Last fall I flew a customer’s Challenger 582 on amphibious floats with a full 17 gallon fuel tank and with him in the back seat. We climbed out at about 600 fpm. Of course, it was a cool autumn evening and we both weigh about 180 lbs each. But I was really impressed by the performance of this Rotax 582 equipped Challenger on floats. Earlier in the year I test flew a new Challenger 582 on wheels and it climbed out so fast that I overshot circuit height by 200 feet and I still had not joined the downwind leg! It made me laugh out loud because it performed so well.

The more powerful engine is not the only reason for the increased gross weight on the XL-65 though. The XL-65 features a high load kit that strengthens the connection where the main wing struts attach to the fuselage airframe. The kit essentially spreads the pull forces from the wing over a wider area where the strut bolts attach to the longeron. So the wings are therefore able to pull on the fuselage with more force with the high load kit. This kit is available for retrofit on any Challenger but it will not increase the gross weight of old Challengers. It will simply add strength and peace of mind.

In addition, the XL-65 now has the fuel tanks in the wings as a standard feature. The wings have been specially strengthened to accommodate the weight of the two 10 gallon wing tanks. Having the fuel in the wings means that the weight of the fuel is spread out and is easier for the aircraft to carry. Formerly, the weight of the fuel carried in the fuselage meant that all of this weight would be focused where the wings join the fuselage. The new wing tanks take this stress away from the fuselage to wing attachment point.

Finally, the XS-50, XS-65 and XL-65 models have a redesigned landing gear assembly. The welded steel cuffs that support the gear legs have been heavily reinforced. Formerly the steel cuffs were two separate units that sat around the two large fuselage longerons. Now the two steel cuffs are connected together with a welded steel cross brace that spans the width of the fuselage. In addition, the cuffs are supported by triangular welded steel support rods that are inside the fuselage. These supports brace the gear leg cuffs from forces they have to encounter during landing and taxiing across rough terrain especially at higher gross weights.

The other advantage to this new landing gear design is that all of the external guide wires that used to be added to support the gear legs are now no longer necessary. This makes for a cleaner less draggy aircraft with a higher cruise speed. It is even easier to climb into the rear seat!

So, these four new features: more horse power, the high load kit for the struts, the wing tanks and the beefed up landing gear, all add up to the higher allowable gross weight of 1060 lbs for the XL-65 Challenger model. This makes the XL-65 Challenger ideal for use on floats. It will perform better with 2 persons on board during the hot summer months.

Although it has the beefed up landing gear and the high load struts, the XS-50 model, which has the smaller 503 engine and the 26 foot clipped wings, has a maximum gross weight of 960 lbs. The clipped wings give it a higher cruise speed. However, the XS-50 is not suitable for use on floats. The shorter wings will not provide enough lift for use on floats.

All that having been said, it is always wise to keep a eye on your gross weight when its hot, humid, and if you are flying at a high altitude airport. Your initial pilot ground school training should have taught you about density altitude and the increase in required runway take-off length at high density altitude. The rule of thumb is that if you are not past 1/2 your required take-off speed at the 1/4 runway length marker, you are not going to make it. Abort your takeoff!

Will people keep adding to the empty weight of the Challenger so that even the new gross weight of the XL-65 is exceeded and performance is adversely affected? Probably some will. Give some people an inch and they will take a mile. (For younger readers: Give some people a centimeter and they will take a kilometer.)

The exhortation remains: Keep the weight of your aircraft to a minimum. Avoid unnecessary weighty add-ons and modifications. Keep the junk out of the trunk (or fuselage in this case).

The Challenger Light Sport Model Summary

Model	Challenger XS-50	Challenger XS-65	Challenger XL-65
Wing span Engine Ldg Gear Weight	Clipped Wing 26′ Rotax 503 (50 hp) Wheels and Skis 960 lbs gross weight	Clipped Wing 26′ Rotax 582 (65 hp) Wheels and Skis 960 lbs gross weight	Long Wing 29.5′ Rotax 582 (65 hp) Wheels, Skis, Floats 1060 lbs gross weight

Challenger XS-50 Flight Test Report

On November 22, 2011, we test flew the Challenger XS-50 C-IMBJ for the first time. The airplane performed beautifully.

Compared to my classic Challenger II, C-IRDL, the XS-50 was even easier to fly. The differential ailerons work great. There is much less need for rudder input in turns. A little is still required, but not much.

The aircraft is also much easier to keep on a straight track. My Classic Challenger wants to wander and I am constantly correcting my heading. The XS-50, with its larger fin area and the fin extension over the rudder, makes holding a heading much easier.

Flying solo I did not notice a difference in the rate of climb. The aircraft was not equipped with a VSI so I can not report on the climb rate. It left the ground quickly and I was at circuit height when I passed the end of the 6500 ft North – South runway here in Kingston.

I climbed to 2500 feet and tried some gentle turns and some stalls. Left hand turns actually required no rudder input, no doubt due to the effect of the engine slipstream on the fin and rudder. Right hand turns needed some  rudder input to initiate the turn and to roll level.

The new plane is fast. Real fast for a Challenger. Flat out, full throttle, straight and level, with 6400 rpm on the tachometer, the ASI read 96 mph! Throttled back to 5800 rpm, a reasonable cruise setting, the ASI maintained 82 mph straight and level.

Keep in mind that the XS-50 is a clipped wing with a 26 foot wing span and fiberglass Hoerner wing tips. This model XS-50 had the optional large oil tank (from Light Engine Services) hidden under the rear mid wing gap cover. The XL-65 with longer 29.5 foot wings will be slower due to the increased induced drag of the bigger wing. It will be interesting to see what the XS-65, the clipped wing Challenger with a 65 HP Rotax 582, will cruise at. Although it has more horse power, the drag from the radiator and the exposed oil tank may counter the advantage of the increased power. But it will climb faster than a 50 HP model.

Here’s the mean data on the XS-50 as tested on a cold fall day (-7 degrees C):

Stall speed clean (no flaps) solo = 32 mph indicated

Stall speed clean (no flaps) dual = 36 mph indicated

Max level flight speed full throttle 6400 rpm = 96 mph indicated

Cruise speed level flight throttle @ 5800 rpm = 82 mph indicated

The heater worked great. Despite the fridgid outside temperatures (-7 degrees C or 19 Fahrenheit) we were warm in the plane for our 1 hour cross training flight. This heater captures the air flowing over the air cooled Rotax 503 and blows it into the cockpit. I copied the design from one I purchased from Turbulence Aviation years ago. Jean Claude does not make them any more and gave me permission to copy his design. Unfortunately with the demise of the Rotax 503, it will be the last 503 heater I make as well.

The other major difference that I noted between my Classic Challenger II and the clipped wing XS-50 was in the landing flare. I am not proud of my landings today.

My Classic Challenger has the 31.5 foot wing span with the bow tips. When it flares, it floats and settles onto the runway. I am very used to its actions in a flare.

The XS-50 with the short 26 foot wings settles down onto the runway much faster. We landed with a thump. This will take some practice and a change of procedure, a little more throttle and less back stick on the flare (I ballooned a little). But then again, its not my plane. I am back to flying my Challenger II Classic. A little slower, a little more rudder, but she’s my baby.

The customer was delighted with her new plane, and that’s all that matters. I was impressed with the handling and performance. It’s a sweet ride.