FMS Fox 3000MM Aerobatic EP Glider

Written by Andrew Griffith A big glider at a small price Product Review As seen in the May 2019 issue of Model Aviation.

Bonus Video

At A Glance

Specifications

Model type: Electric glider Skill level: Beginner Wingspan: 118.1 inches Wing area: 1,154 square inches Wing loading: 20.4 ounces per square foot Wing cube loading: 7.2 Airfoil: Semisymmetrical Length: 73.8 inches Weight: 10 pounds, 4 ounces Power system: 460 Kv electric motor; 70-amp ESC Radio: Full-range, five-channel minimum Construction: EPO foam Covering/finish: White foam with water slide decals Price: $439.99

Test-Model Details

Motor used: 460 Kv brushless electric (included) Receiver battery: BEC (included) Propeller: 15 × 7.5 folding propeller (included) Radio system: Spektrum DX20; AR636 receiver; six 23-gram metal-gear Predator servos Ready-to-fly weight: 10 pounds, 4 ounces Flight duration: 20-plus minutes

Pluses

• Constructed of durable, easy-to-repair EPO foam.
• Huge model with great presence in the air.
• Aerobatic and fun to fly.
• Easily removable canopy allows access to the roomy battery compartment.

Minus

• Needs some color on the bottom of the wing to improve visibility, especially at a distance.

Watch It Fly

The clean lines of the Fox are on display during a high-speed pass. The propeller folds back, greatly reducing drag when the throttle is closed. The full-scale mdm-1 Fox is a fully composite, two-seat aerobatic glider with a 14-meter (46-foot) wingspan. During its debut in 1993 at the World Aerobatic Glider Championships in the Netherlands, Jerzy Makula flew it to win a gold medal. The two-place Fox can withstand up to 9 positive Gs and is currently used in air show flight demonstrations and aerobatic glider training. The first thing that jumped out at me as I unpacked the FMS Fox 3000mm Aerobatic EP Glider was that this thing is big! The carbon-fiber wing tube alone measures 56 inches long and the fuselage is longer than my 60cc Corsair! The Fox is constructed of dense EPO foam. In addition to the primary flight controls, the Fox is equipped with flaps and, like the full-scale Fox, uses fixed landing gear. Power is provided via a 460 Kv brushless electric motor and 70-amp ESC fed by a six-cell LiPo battery. It employs a 15-inch propeller that stops and folds back to minimize drag and maximize glide performance when the throttle is cut. The roomy battery compartment easily accommodates a six-cell 5,000 mAh LiPo. There is no point trying to save weight with a smaller battery. The Fox needs some weight up front to offset the weight of the beefy tail, and I prefer to carry a useful battery instead of dead weight. I chose a new 6S 5,000 mAh Spektrum Smart battery to power the motor system; a built-in BEC powers the radio system. A couple of details stood out to me as I inspected the parts. The two-place cockpit doubles as the battery hatch and is held in place by a springloaded latch. Instrument panels and a pilot figure are included. Although FPV isn’t my thing, someone who does a lot of FPV flying at our field noted that the canopy is perfectly clear and free of blemishes. In addition to the main wheel, another nice feature is the smaller wheels on each wingtip and one on the tail. These will prevent runway rash on the long wing during landings. I looked over the wing halves and drew a couple of quick conclusions. The molding is smooth and the finish is glossy. The flat-bottomed airfoil has a thick (several millimeters) trailing edge (TE). This is, pardon the pun, a double-edged sword. On the plus side, the thick TE will likely mitigate damage from handling and transportation better than a razor-thin TE. The downside is that it will probably hurt glide performance slightly, but the airfoil’s high lift, and adding a few degrees of flaps, should overcome this nicely.

Assembly

I read the online version of the manual before receiving the Fox. Assembly appeared to be so simple that I decided to put the box in the truck and take it to the field to put together. The parts count is extremely low, and the Fox snaps together in only a few minutes. No tools or adhesives are needed. It’s also easy to break down to transport without tools. If transportation space is tight, the entire tail can be removed in a few seconds, breaking down to manageable pieces. The wing installation uses a clever multiple connector that mates up when the wing is snapped into place to connect the aileron and flap servos. There are no extensions to fool with. Slide the wing tube into place, slide the wing halves into position until the latch clicks, and you’re done. The first few times that I installed the wing halves, they were a tight fit in the wing pockets. You want to be sure that they are fully seated, with the latches engaged. They could probably be lightly sanded, but I chose to allow them to wear in. The horizontal stabilizer slides into place and engages a spring-loaded latch. The elevator servo needs to be connected to the extension in the tail assembly, but the elevator is already hinged and the servo and pushrod are preinstalled. Snap, click, done.

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Next comes a truly clever feature of the Fox. After connecting the elevator and rudder servo extensions at the tail junction, the entire tail assembly rotates and locks into position. Pulling the pin and rotating the tail assembly allows you to disconnect the servo extensions and transport the model with the entire tail removed. After the wing and tail were installed, it was simply a matter of installing the receiver and flight battery and making the appropriate connections. The Fox uses a typical FMS controller board in which the ailerons and flaps are effectively joined by a Y harness and each is controlled by a single receiver channel. This will drive a few glider purists to fits because it means that if you want full camber control or aileron differential, you need to do some home cooking. I don’t feel that it would be worth the effort. After binding to my DX20 Spektrum radio, I adjusted the control throws so that they were in line with the manual’s recommendations and added 30% exponential to all of the control surfaces. Because of the high-lift wing, motor gliders often need some down-elevator trim when under power, so I built a mix to add down-elevator when throttle is applied. I left the input values at zero until I test-flew it to see how much, if any, was needed. The Fox will be well suited for nearly any radio system. I tested the power system with my Hangar 9 wattmeter and found that it produced roughly 1,250 watts while pulling 55 amps. There is plenty of overhead for a 70-amp ESC, and it yields slightly more than 100 watts per pound.

Flying

After assembling the Fox and charging the Spektrum 6S 5,000 mAh Smart battery pack, I checked the balance and had to install the battery nearly all the way forward on the tray to get the center of gravity in the recommended range. The propeller length and the landing gear stance make rolling takeoffs impossible, so the choices are hand launching or building a launch dolly. Having handlaunched many powered gliders throughout the years, I decided that this would be a two-person operation. It is possible to self-launch the Fox, but my motto is that if you have help available, you might as well use it. My friend, Adam Strong, held the Fox aloft while I powered up to full throttle. He then gave it a straight toss into the prevailing wind. The Fox climbed with authority and, as I suspected, it needed some down-elevator when full power was applied. The climb rate isn’t ballistic, but it’s no dog and gains altitude quickly. Common questions about a glider such as this will be about glide/thermal performance, aerobatic ability, and energy retention. I’ll start with glide performance.

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Sources: Spektrum (800) 338-4639 www.spektrumrc.com