Superior RC Extra 330L
Frank Granelli
A versatile, well-rounded 50cc aerobat
The Extra goes exactly where it is pointed and looks good doing it. The rudder has ample authority, with little required for knife-edge flight.
WALTER EXTRA manufactures some of the most exciting and competitive business and aerobatic airplanes in the world. Among his best is the Extra 300/330 series of aerobats. The world’s fastest production, nonsupercharged piston airplane is his 330LT. The 330SC is the current world aerobatic champion, and the 330LC is considered one of the best aerobatic two-seaters available.
The one aircraft that Mr. Extra does not produce is a 330L. Yet the modeling world features hordes of various 330Ls, and one of the most interesting is the 29% version from Superior RC.
In addition to its all-wood laser-cut construction, extreme prefabrication, and attractive cover scheme, the Superior RC Extra 330L features a high-performance, scalelike control surface hinge system. Known as the “Pocket Hinge System,” a 2mm carbon-fiber rod passes through phenolic bearings to mate the control surfaces. The control surface leading edge is rounded, nesting tightly against the fixed surface.
The result is a sealed, gapless joint that eliminates flutter and reduces air drag while increasing the effectiveness of the control surface. By using this hinging system, all control surfaces are capable of up to 60° movement.
The ailerons and elevators are installed at the factory, and mounting the impressive rudder requires approximately 75 seconds. The rudder on this 90.5-inch-wingspan airplane is massive. It is also extremely effective—more so than that on any similar-size aerobatic airplane I have owned or flown.
The majority of work has been completed by the time you remove the 330L from the box. The tasks that remain for you to do are much less challenging than is usual with most large ARFs.
Wing and stabilizer carbon-fiber spars are already mounted into the fuselage. The cowling mounts are factory-installed, as are the phenolic rudder control horns. A complete hardware package, including extra Oracover in all colors on the model, is packed in the gigantic box.
Tools, radio equipment, engine, and a short length of extra fuel line are all that you need to finish this model.
Equipment
The review 330L is powered by the BraveHeart BH50. This 3.75-pound 50cc gas engine produces 5.2 horsepower at 6,500 rpm and comes with an effective muffler, standoffs, and an electronic ignition system.
The BH50 has proven to be reliable, idles well, can hover the big Extra, and provides decent verticals. At only $300, it is incredibly cost-effective.
Since the onboard battery system was planned to be four times redundant, I installed two Spektrum 2S2P 4000 mAh Li-Poly battery packs. I wanted to reduce setup complications by eliminating the ignition battery.
Since most of the servos were 6-volt units, both batteries also needed voltage regulators. With the usual setup, this requires two radio switches, an ignition switch, and two regulators. Enter the remarkable Tech-Aero Designs Ultra IBEC (Ignition Battery Eliminator Circuit).
This programmable device powers the engine’s ignition system from one or two receiver batteries with regulators all on a single switch. The ignition and receiver voltage outputs can be set anywhere from 5–6.5 volts (I set both at 6 volts), while the input voltage can be as high as 13 volts. There are four filter stages that eliminate possible capacitive discharge ignition (CDI) interference.
Twin batteries with voltage regulation, elimination of a separate ignition battery, extra CDI filtering, ignition control from the transmitter, and an on/off light—all in one system.
For this airplane I chose the new Hitec HS-7955TG and HS-7950TH (rudder) titanium-gear, coreless digital servos. These ultrastrong units feature dual ball bearings, fast transit times, and, most important, super-precise digital centering.
Exact servo centering is all-important in this type of model. Imagine trying to fly the 330L in a straight line, with its super-responsive control surfaces, while the giant rudder is slightly offset or an aileron is hanging—impossible!
The 333 ounces of torque at 6 volts that the HS-7955TGs produce eliminates the need for twin aileron servos on the Extra, although the wing does have two servo mounts and the extra linkage hardware. Those units are also very fast, at 0.15 second.
On the rudder the HS-7950TH produces 403 ounces at 6 volts in 0.15 second. Later, when run at the full 7.4 volts, this servo will speed along at 0.13 second, producing 486 ounces of torque.
Although the 330L’s onboard power requirements are small, I used the JR R122 12-channel receiver that can handle 10 volts and 35 amps of current. It has dual battery connections and a data port, allowing me to monitor what is happening inside the model in flight. The trusty JR 12X transmitter will easily handle all control and trimming tasks.
Assembly
Starting with the wing, ailerons are preinstalled using the Pocket Hinge System, requiring only servo installation. The light, precise linkage is included and is close to the perfect length. Use a servo arm that is at least 1.25 inches long for maximum aileron movement.
Mounting the engine is the first task. Superior RC provides mounting templates for Desert Aircraft 3W-50i and DA-50R engines in the instruction booklet. The template for the BH50 engine is available on the website. The longest offsets supplied with the BH50 are too short by 8 mm (0.315 inch). Four 1/2 x 1-inch maple blocks were epoxied to the firewall for spacing. When installing the aluminum firewall braces, bolt the front section on and then drill the side mounting holes to ensure that the braces are held tightly against the firewall.
Cowl mounts are installed at the factory, but the cowl mounting holes must be drilled. They should be 11.5 mm (0.453 inch) forward from the cowling rear edge.
Although instructions place the throttle servo inside the firewall extension, I positioned it just to the rear of that along with the choke servo for easy access.
The BraveHeart engine’s choke lever rotates fore and aft. Rather than install a complicated bellcrank arrangement to place a choke actuating rod out the side of the cowl, I installed a choke servo to perform this task.
Elevator servos mount inside the stabilizer halves, and those halves mount on a carbon-fiber spar and bolt into factory-installed blind nuts in the fuselage. The same light, precise linkages used with the ailerons are used to control the elevators.
The elevator halves must travel the same distance and be level at all times—up or down. If not, the Extra will never perform correctly, because it will always be trying to roll with elevator input.
Before installing the rudder, tape two straight balsa sticks onto the elevator tops; they must be positioned to meet on the fuselage centerline behind the vertical fin. Adjust the elevators until the sticks are level.
Move the elevators up and down. The sticks should remain level throughout their travel range and at the endpoints. If they don’t, adjust the elevator control horns, and then make endpoint adjustments. If all else fails, use point mixing until the sticks are synchronized.
A few pilots might prefer to deviate from synchronized elevator movements to compensate for varying torque changes during maneuvers. But even this advanced trimming technique requires starting with synchronized elevator halves.
When attaching the rudder and its pull-pull control system, I found the supplied crimp tubes were too small to allow three cable passes through them. I substituted short sections of 1/8-inch brass tubing. Don’t forget to put thin CA in the crimp tubes after everything is set.
The rudder control horns span roughly 2.25 inches, so use a matching servo output arm for proper centering.
Everything else is fairly straightforward. Make sure that all control surfaces move approximately 60° in each direction; this is where the Pocket Hinge System really shines. The 330L required 1.25 pounds of fishing weights to balance at the 160 mm CG point. The BH50 is on the lighter side. The aircraft is configured for a canister muffler, but I used the stock muffler instead. Both factors combine to reduce nose weight, thereby requiring the extra lead.
The result of close to 30 hours of work is an attractive big airplane that doesn't merely show up at the flying field; it makes an entrance!
Flying
This Extra has two internal arrangements. The stock layout places the receiver and fuel tank behind the CG as outlined in the instructions. When balanced with an empty tank, the model in this configuration is slightly tail-heavy once fuel is added.
My experience is that this is an intentional design to enhance 3-D performance. With fuel in the tank, the 330L flies normally at speed. When throttled back and slowed, it drops its tail and is ready for 3-D work.
This airplane's torque rolls are far better than I can fly. With the tail wanting to drop, full-power Blenders are impressive.
Waterfalls are easier to perform, as are knife-edge loops. The rudder is as impressive in its performance as it is massive.
In fact, all control surfaces are extremely effective. The Pocket Hinge System seals the gaps, increasing control response even at exceptionally slow airspeeds.
Sealed controls also mean that all control surfaces are equally useful, making the aircraft's response curve predictable and constant. For example, the Extra has no wing-drop tendencies when entering the Wall maneuver, because no air spills through an elevator or aileron gap.
However, you pay a price for the 3-D performance. Landing after only eight minutes aloft requires the pilot to hold down-elevator during the approach. Flaring is accomplished by releasing down-elevator. If your transmitter allows it, mixing in one or two points of down-elevator with idle throttle does tend to normalize landing control inputs.
Although it's unusual for many fliers who are unaccustomed to 3-D-trimmed models, the Extra's full-fuel approach is steady and controllable. There are no dangerous tendencies, as are common with most tail-heavy airplanes. It is just that the nose has to be "held down" with elevator.
As fuel burns off, so does 3-D performance while the 330L slowly becomes more tractable as it regains pitch stability. Landing after a 20-minute flight (the BH50 uses little fuel) is normal. With the tank nearly empty, the model is back in balance and easy to fly.
The Superior RC Extra 330L handles a tail-heavy condition better than any model I have ever flown. But—although it flies 3-D far better than I can—it will not fly "pretty" in the tail-heavy condition.
The control surfaces are too large and far too effective for smooth maneuvering with an aft CG. Even when control surface movements are reduced from 60° to only 10°, slow rolls and knife edges walk badly, snap rolls are awkward, the elevator is far too effective for flying smooth maneuvers, stall turns require a deft touch to avoid их turning into rudder loops, and landings are about 10 mph faster than they should be.
That is common in many models that are designed and trimmed for 3-D work. I prefer flying pretty, so something had to change.
Remember my mentioning that this aircraft is unusually tolerant of CG changes? Well, it truly is. So I made a new, removable fuel-tank position directly forward of the CG.
This makes the Extra slightly nose-heavy when the tank is full. That little change has made all the difference.
Going to lowest rates on the 12X reduces elevator travel to 18°, ailerons to 14°, and rudder to 30°.
With the now-forward CG, the 330L will fly the most beautiful loops and Avalanches, awesome stall turns, barely in-sight to nearly out-of-sight slow rolls, and knife edges with little walking.
Multiple fast rolls are simple to keep in a straight line. Almost zero down-elevator is required when inverted. Outside snaps can be stopped on point almost by single-digit degrees. Spins can appear nearly flat, while altitude loss during the spin is less than expected.
During one flight the airplane flew into what was supposed to be a normal test spin, which morphed into an unplanned sequence because it was performing so well in the spin. Starting at roughly 600 feet, it flew into a two-turn spin to the right, stopped on point, changed to a left two-turn spin, stopped on point, then rotated three turns to the right, followed by another point stop and three turns to the left. It then stopped rotating and climbed straight up approximately 200 feet more, leveled out inverted, and did opposite two-turn inverted spins.
I had not intended to do that, but the Extra proved such an excellent flier that it just happened. After all of that flying, the landing proved to be slow and typical.
With the addition of the forward fuel tank mount, I now have two models in one package. For practicing 3-D, I fly the 330L in stock form by adding a few inches of fuel-line extensions. For flying pretty, move the tank and receiver forward. This is a good deal and a good airplane.
Plans are to reduce the amount of nose weight by moving the rudder servo and the twin receiver batteries forward, while reducing tail weight. This should reduce the nose weight required to nearly 16 ounces.
The Superior RC Extra 330L is versatile, and exploring that versatility is going to be a lot of fun.
Test-Model Details
- Engine used: BraveHeart BH50
- Propeller: Mejzlik 22 x 10 carbon fiber
- Radio system: JR 12X transmitter, JR R122 12-channel receiver, four Hitec HS-7955TG servos, one Hitec HS-7950TH servo, one Hitec HS-322HD servo, two Spektrum 2S2P 4000 mAh Li-Poly batteries
- Ready-to-fly weight: 20.1 pounds
- Flight duration: 20 minutes
Specifications
- Model type: RC scale ARF
- Skill level: Intermediate builder; intermediate pilot
- Wingspan: 90.5 inches
- Wing area: 1,314 square inches
- Length: 76.6 inches
- Weight: 18–20 pounds
- Wing loading: 35.07 ounces/square foot
- Engine: 50cc (gas)
- Radio: Five channels minimum; six to eight servos
- Construction: Balsa and plywood, fiberglass cowl and wheel pants, heavy-duty plastic canopy
- Covering/finish: Five colors of Oracover with matching fuelproof paint
- Price: $695.95
Pluses and Minuses
- Exceptionally wide CG range.
- High-quality construction throughout.
- Innovative Pocket Hinge System.
- Carbon-fiber spars, landing gear, and spinner.
- Plug-in wings and stabilizers.
- Stable yet versatile performer—great for 3-D.
- Vague instructions, especially about throttle-servo installation.
- Color scheme can appear dark in the air.
Manufacturer/Distributor
Superior RC Model Distributors Box 514 Long Lake, NY 12847 (518) 624-2478 www.superiorrc.com
Sources
- Spektrum
(800) 338-4639 www.spektrumrc.com
- Tech-Aero Designs
7 Parkview Rd. Randolph, NJ 07869 www.tech-aero.net
- JR
(800) 338-4639 www.jrradios.com
- Hitec RCD USA
(858) 748-6948 www.hitecrcd.com
Transcribed from original scans by AI. Minor OCR errors may remain.
