After ever-bigger Rebels, the JDM – 8 is a genuine ultralight Darryl Murphy’s commitment to small plane design is evident by the fact that during the years when Murphy Aircraft Mfg. exhibited in two locations at various fly-ins, Darryl frequently was seen working his company’s booth in the ultralight area. Other Murphy Aircraft staff members would be working the Rebel/Super Rebel booth. At the Northwest EAA Fly-In in Arlington, Washington, this past summer, that pattern re-emerged; the boss stayed with the JDM-8 in the ultralight exhibit area. In my conversations with him, he seemed pleased to be presenting a genuine ultralight again. Those who know the history of Murphy Aircraft before the first Rebel arrived won’t be surprised to see the company marketing an ultralight. This Canadian manufacturer was an ultralight company that expanded into homebuilts and has achieved success through their Rebel series. The new single-seat JDM-8—especially when contrasted with the huge, radialengine- powered Moose—shows this company has not forgotten its roots in ultralight aircraft.
After ever-bigger Rebels, the JDM - 8 is a genuine ultralight Darryl Murphy’s commitment to small plane design is evident by the fact that during the years when Murphy Aircraft Mfg. exhibited in two locations at various fly-ins, Darryl frequently was seen working his company’s booth in the ultralight area. Other Murphy Aircraft staff members would be working the Rebel/Super Rebel booth. At the Northwest EAA Fly-In in Arlington, Washington, this past summer, that pattern re-emerged; the boss stayed with the JDM-8 in the ultralight exhibit area. In my conversations with him, he seemed pleased to be presenting a genuine ultralight again. Those who know the history of Murphy Aircraft before the first Rebel arrived won’t be surprised to see the company marketing an ultralight. This Canadian manufacturer was an ultralight company that expanded into homebuilts and has achieved success through their Rebel series. The new single-seat JDM-8—especially when contrasted with the huge, radialengine- powered Moose—shows this company has not forgotten its roots in ultralight aircraft. Welcome back to the lighter side of Darryl Murphy. From Moose to Ultralight The JDM-8 is a low-wing monoplane, and in the tradition of Darryl’s later designs, it’s of all-metal construction. Recall that Murphy’s first entry onto the ultralight/ homebuilt scene was the tube-and-fabric Murphy Renegade biplane, followed next by the all-metal Rebel, Super Rebel, and Maverick designs. Having flown the Renegade, Maverick, and two models of the Rebel, I keenly followed the development of the single-seat ultralight Darryl was creating. The first version was rather basic and a little crude in the way of prototypes. It used a wing covering called Tedlar, the see-through qualities of which were interesting. But this material never seemed to strike a chord with the mainstream. At the Northwest EAA Fly-In when I chanced across the latest version of the design, I was pleased to see it had more conventional construction and was painted in the highly finished way typical of Murphy Aircraft’s air show planes. And, it had its wings folded! That impressed me for several reasons. Darryl told me years ago that he does not like folding wings because he was always concerned about wings folding in flight. Yet, here was his new JDM-8 with that popular feature. In true Murphy style, Darryl expended special effort in designing the wing-fold mechanism to make sure that it would be unlikely that anyone would ever assemble this aircraft in a manner that would cause it to fold up in flight. “We do not want the JDM-8 to have an incident,” said factory representative Stephane (pronounced Steh-FAHN) Marois, “and that’s why this design does not use the rearward-swinging wings often seen on other aircraft.” Instead, Murphy uses a folding system similar to Navy carrier aircraft where the wings fold upward from the wingtip and come to a point above the canopy. When folded, the wings are less than 11 feet above the ground—still low enough for most hangar doors—and 8 feet wide. This should equate to lower hangar costs and less hangar damage to parts, though you’ll want to preflight the hinges with special care, as they become the outermost extremities when the JDM-8 is folded. Folding of the wings is best done with two persons, as a few parts must be detached. It will take 10-15 minutes per wing to fold the JDM-8 into or from its 8- foot width. In addition to his conscientiousness about thoroughly reviewing the folding-wing mechanism, Stephane was equally careful to show me the aircraft bolts used in the elevator and rudder hinges. He employs a fore and aft motion to reveal if any elongation is occurring in those hinges. Murphy Aircraft uses a clear tape for gap seals; you can barely see them, but they close the opening and improve control efficiency. Stephane, who reports flying 30 different ultralights, is quite impressed with the feel and control balance of Darryl’s design. Murphy powered the JDM-8 with the Rotax 277 engine to stay within FAA’s Part 103 weight definitions. Darryl describes the 277 as “half a 503,” an apt enough label that I’d never heard before. Some buyers are likely to choose the Rotax 503 for its extra oomph. Those who want to stay within Part 103’s limits but yearn for more power or twin cylinders may use the 2si or Zanzottera engines, both of which boast lower weight penalties. Parts to Paint in Two Weeks Stephane built this evaluation aircraft at the factory in a mere two weeks, a reasonably amazing feat, despite long hours during the fortnight. He located parts from here and there in the sprawling Murphy Aircraft plant. And he admits that he had some assistance from other employees including Darryl himself. Despite the ideal working environment for such a project, I find it an impressive effort to go from parts to paint in two weeks’ time and then debut the new machine at the Arlington air show in July 2002. Yet, at the same time, the attention to detail in this aircraft is obvious. For example, Stephane used waxed cord to secure the bungee cords for the landing gear suspension. Normally, builders use the faster and easier metal clips, but these can cut into the cords during normal use. The cord method takes more time and effort, but some say it helps the bungee system last longer. The cowling on this particular JDM-8 was the same one used on the original Murphy Renegade biplane. It had been returned to the company and gained new life after being refitted to the JDM-8. In fact, the entire JDM-8 I flew employed parts of other Murphy designs. Stephane said the landing gear and control linkages are taken from the Renegade, and the wings and tail are from the Maverick. These are parts that buyers can feel comfortable with based on the long track record for those other models. Another reason the fast build was successful is that the JDM-8’s metal components use the matched-hole system perfected at Murphy over many years of kit building. This method virtually guarantees that the parts will go together accurately. In still another example of detail awareness, Stephane was careful to make me aware that he had just mic’d (micrometer measured) the control cable swages to be positive they had a perfect press. Throughout the aircraft, the JDM-8 uses single-swaged nicopressed cable ends— which is the established industry method. Despite the fast building time, this isn’t a rushed-together project; the JDM-8 has been developed and refined over a four-year development period. Though it borrows from other Murphy designs, the final JDM-8 design shares only a few common airframe members with the Tedlar-covered version shown at Sun ’n Fun two years ago. Overall, I found Stephane to be a careful and thoughtful young fellow. After his excellent preflight check and preflight review, I had no concerns when I took to the air solo for the first time in this new JDM-8 he’d built. In addition to his building skills, Stephane is quite an experienced pilot, having logged lots of time as an instructor for another Canadian company prior to joining Darryl Murphy’s team, basically to work on this project. The preflight Stephane did was arguably the best inspection I’ve ever seen anyone do on an airplane. Of course, he’s the proud papa of this particular aircraft. (During construction, Stephane slept on a cot in the Murphy “infirmary,” as he didn’t want to spend an hour and a half each day driving from his home.) He expressed great satisfaction at working for Darryl. He says Darryl gives direction and has control of the operation, but allows enough autonomy that his employees can exercise their own abilities and judgment. Flying on Darryl’s Long Experience I’ve had the pleasure to fly several of Murphy’s aircraft, and I cannot think of one I didn’t enjoy thoroughly. When he offered the JDM-8, I was eager to go aloft. After Stephane’s exacting preflight exam, I felt ready. Once I eased myself into the surprisingly spacious cockpit and fired up the 277, I was ready to go, my tape recorder at the ready to note my observations for this report. My evaluation model JDM-8 has large tires and wheels with hydraulic brakes set up for differential action. This is necessary as the ultralight version has no movable tail wheel, though the tailskid present on the aircraft at the Northwest EAA Fly-In gave way to a tiny skateboard-type wheel by EAA AirVenture Oshkosh. Murphy explained that its factory strip is rough gravel, and a skid is superior to a small wheel on such a surface. Soon after leaving the ultralight runway at EAA AirVenture, I noticed the windscreen gave good wind protection, but it created some rumbling noise while flying. You can elect a slightly taller windscreen or a full canopy—but not if you want to remain within the weight limits of Part 103. The JDM-8 wanted to nose over rather convincingly, though sufficiently light stick forces made it easy to keep the nose up. When I had examined the aircraft before the flight, I saw it once had its seat one bulkhead aft of the current position. It was moved forward to accommodate the lighter weight of both the 277 engine and Stephane’s bodyweight. Because I outweigh Stephane by 20-plus pounds, this seat location probably accounted for the JDM-8’s tendency to lower the nose. Larger pilots may prefer the popular Rotax 503 engine. If so, they’ll move the seat aft one bulkhead—along with the rudder pedals plus other controls. Any builder could locate the seat such that the balance is right for him or her. A controllable trim could also be added if pilots of different weight were going to fly your JDM-8. However, if you want to operate under Part 103, you’ll need to be careful about any weight additions. Though Stephane likes a non-locking throttle, I prefer the opposite, especially when flying with the Rotax 277 engine, which I’ve found can drop from a cruise setting to 4000 rpm without you noticing the change. At the lower revolution, the engine will not sustain the JDM-8 and you lose altitude, albeit rather slowly. Contrarily, the slightest forward bump of the throttle will push the revs back to 5000. I tried to hold between 5000 and 5500 rpm on the 277, and anywhere in this range, the JDM-8 will sustain level flight. The JDM-8 I flew was fitted with a cruise prop so it could keep up better with a Super Rebel in a photo session, but the two-blade wood prop provided only a 300-fpm climb. Clearly, you’ll want more, but Stephane assured me that a different prop and different carburetor jetting will remedy the situation. The current 150 jet setting would be replaced with a 148 jet to “significantly boost the power,” he says. The 150 setting was chosen for Arlington, Washington’s, cool air and proved less than optimal in Oshkosh’s hot and humid summer air. We postponed my flight of the JDM-8 during the Arlington 2002 fly-in because Darryl Murphy wasn’t adequately satisfied with the plane. At EAA AirVenture he still fussed at not having this JDM-8 example “perfect,” but he eventually consented to let me fly it knowing that most remaining improvements will be finished before kits are shipped to customers. The JDM-8’s brakes were very powerful. You lift your feet to actuate them (Cessna style), but at first they seemed a little sensitive for ground steering. However, it is precisely ground steering that necessitates brakes this powerful. The tail wheel is not steerable, so the brakes perform steering duties. This was done to keep weight off, but I have to question if hydraulic brakes in lieu of a steerable tail wheel is an efficient weight trade-off. On the lone ultralight runway at Oshkosh, I landed in a significant left crosswind, ranging from 45 to 90 degrees off runway heading. Despite this situation, I did not employ the usual corrections of crab or wing down, and yet the JDM-8 landed very cooperatively. It was as easy as any aircraft I’ve ever flown; so easy it seemed I had help from invisible hands. My takeoff was a little more challenging because of the combined effects of the uphill (northwest) ultralight runway and this JDM-8’s cruise-propped 277 engine. Nonetheless, even at 300 fpm, I never doubted I could climb strongly enough, though it was obvious that a 503 engine would make quite a performer out of this design, even with the engine’s added weight. The airspeed indicator on the JMD-8 was nonfunctional, so I couldn’t perform several of my preferred evaluations. But based on intuition gained from experience, the descent rate felt good; it didn’t give me a fall-from-the-sky feeling when I throttled back. Murphy’s Law If you do not need or wish to stay within Part 103’s weight limitations, the JDM-8 would be an excellent performer with the Rotax 503. You could also use leaf-spring main gear legs in place of the bungee cord suspension, and you could have a full canopy in lieu of the opencockpit version, though many pilots will prefer a partial enclosure that still allows you to smell and feel the air. Builders may also choose to shorten the wing for faster cruising by taking out one bay. The wing was designed with this in mind. You can alter the wing one bay inside of the curved tip where two ribs are placed back to back with this alteration in mind. This change would move the wingtip in to the outside edge of the aileron, doing away with the flaps and thus giving the wing a fixed trailing edge. Having made these alterations, Murphy says with confidence that the JDM-8 could be transformed “from a Part 103 ultralight to a kit-built aircraft capable of 110 mph.” The important aspect of the transformation described above is that the JDM-8 design suddenly appears very versatile, able to serve many pilots who enjoy single- place aircraft. Nonetheless, I wish to observe—for the umpteenth time—that the lighter ultralights are, the more they fly like true ultralights. The JDM-8 with the Rotax 277 meets this description of a light, responsive ultralight with slowspeed charm. The ultralight model JDM-8 grosses at 485 pounds with an empty weight of 250- 254 pounds, depending on the precision of the builder. If you wish to build an Nnumbered JDM-8, its shortened-wing structure can handle a 700-pound gross weight while the empty weight climbs to 300-400 pounds. Murphy Aircraft also states the airframe can accommodate an 80-horsepower engine, suggesting the Rotax 912 for those with the extra cash and a desire for a more conventional aircraft. The heavier JDM-8 has a 4-foot shorter wingspan and 20 square feet less wing area, and in this configuration achieves nearly a ±6g rating. From genuine ultralight to perhaps a potent and speedy light-sport aircraft under the proposed sport pilot rule, Murphy's JDM-8 is a dandy new entry that deserves your attention. And, it's reasonably priced. The basic airframe kit, firewall back, lists at just under $7,000. Engine options include the Rotax 277, 503, and 912, or the 28-hp Hirth F-33 engine. Murphy aircraft offers engine mount and cowling packages for all options. Though I've enjoyed every Murphy design I've flown, this one is far and away my favorite. Maybe it can satisfy you as well.
Published in Experimenter Magazine
|Empty weight||250-254/300-400 pounds|
|Gross weight||485/700 pounds|
|Wing area||120/100 square feet|
|Wing loading||4.0/up to 7.0 pounds per square foot|
|Width||(wings folded) 8 feet|
|Height||(wings folded) 10.75 feet|
|Fuel Capacity||5/20 gallons|
|Standard engine||Rotax 277|
|Power||25-30/up to 80 hp|
|Power loading||17.3*/8.75 pounds/hp|
|Max Speed||63/110 mph|
|Cruise speed||40-60/45-100 mph|
|Stall Speed||26/34 mph|
|Rate of climb at gross||600/1,000 fpm|
|Takeoff distance at gross||200/100 feet**|
|Landing distance at gross||150/200 feet***|
|Range (powered)||125/400 miles|
|Notes:||*Assuming Rotax 277 engine at 28 horsepower.
**Assuming 28/80 horsepower.
***Assuming 485/700 pounds gross weight.