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Written by Jon Barnes
Sport jet performance in a scale model
Product review
As seen in the December 2018 issue of
Model Aviation.



Specifications

Model type: EDF jet
Skill level: Intermediate
Wingspan: 41.5 inches
Wing area: 358 square inches
Length: 53.1 inches
Weight: 77.6 ounces
Power system: Freewing 12-blade 80 mm EDF
Radio: Minimum six channels required
Construction: EPO foam
Price: $349


Test-Model Details

Power system: Freewing 3530-1850 Kv brushless outrunner (included); Freewing 100 amp with integrated 5-amp BEC ; 6S 4,000 to 5,000 mAh LiPo
Radio system: Spektrum DX9 transmitter; Spektrum AR8020 receiver
Ready-to-fly weight: 102.5 ounces (with 6S 5,000 mAh LiPo)
Flight duration: 3 to 5 minutes


Pluses

• Sturdy suspension-equipped aluminum landing gear facilitates operations from less-improved airfields.
• Bright, sequenced LED landing lights and always-on navigation lights.
• Protective plastic overlay helps prevent the under-canopy cockpit foam from “gatoring” when exposed to excessive sunlight.
• Oversize battery bay allows pilots to experiment with flight duration-extending, larger-capacity batteries.
• Optional detailed 3D-printed cockpit files and preprinted parts available.


Minus

• Slight variations were noted in the hues of red paint used on the underside of the wing compared with the red paint used on the fuselage.


Bonus Video


Product review

The full-scale L-39 Albatros is a high-performance jet trainer that was developed in the 1960s by Czechoslovakian-based Aero Vodochody. It is still used in jet trainer and light attack roles in more than 40 countries.

From Giant Scale, composite construction, turbine-powered behemoths, all the way down to 50 mm electric ducted-fan (EDF) park flyers, an abundance of RC jet models have paid tribute to the popularity of the L-39 Albatros.

Motion RC and Freewing continue to aggressively expand their impressive line of EDF-powered jet models with the release of an 80 mm EDF-powered, EPO foam-composition L-39 Albatros. Like many of the recent models designed and distributed by Freewing and Motion RC, the L-39 is available in both a plug-and-play (PNP) and an ARF Plus version.

The former includes the same lush-sounding 12-blade fan used in several of Motion RC’s previously released 80 mm jet offerings, while the latter version omits the EDF unit and ESC and allows pilots to source their own EDF power system. Dimensioned to come in at 1/9 scale, the L-39 comes bedecked in the brightly colored red, white, and blue scheme used by the White Albatrosses Slovakian Air Force aerobatics display team.




This PNP 80 mm EDF-powered airframe assembles using a combination of glue and screws. A tube of contact-style adhesive is included in the box. All graphics, including an extensive collection of nomenclature markings, are factory applied.


The airframe comes out of the box peppered with an extensive set of factory-applied water slide-style airframe nomenclature graphics. Other pilot-pleasing features include trailing-link, suspension-equipped aluminum landing gear, flaps, and a set of factory-installed navigation and landing lights.

A problem that has long plagued pilots in warmer environs is the tendency of under-canopy foam to “bubble” and “gator” when exposed to excessive sunlight. The L-39 is the first model from Freewing to feature a protective plastic overlay positioned on top of the cockpit foam. By design, the plastic overlay should minimize, if not eliminate, this problem.


Construction

A limited number of fasteners are required to assemble this airframe. In a stroke that is sure to minimize confusion, only two sizes of fasteners are included in the box. Four machine-screw thread fasteners are used to attach the wing to the fuselage. The balance of the assembly, which includes attaching the horizontal stabilizer/elevator, vertical stabilizer/rudder, and the twin tip tanks, uses a dozen of the same size, tapered-thread metal fasteners.

The included tube of contact-style cement is used to glue the tail cone assembly onto the main fuselage assembly, attach the drop tank pylons, mount the two gun barrels into the leading edge of the wing, and to fasten the plastic nose cone to the front of the fuselage.

The drop tanks are designed to magnetically mate with the pylons. While assembling the review model, I noticed that the red paint used on the wing was a shade or two off from that used on the fuselage (in the air and at speed, the difference proved to be barely perceptible).

EDF jet purists might raise an eyebrow because this model does not rely solely on the Albatros’ twin-scale inlet ducts to feed intake air to the 12-blade, 80 mm fan. The NACA-style auxiliary air intake employed by this model is discreetly sized and unobtrusively positioned on the underside of the model at the aft edge of the wing.

Freewing has rolled out a multifunction control module in this model. Christened the MCB-E, this small, blue box nicely aggregates and minimizes the abundance of servo wiring inherent to a model of this size and complexity.




The wingtip tanks attach using a pair of small metal fasteners, allowing pilots to easily replace the tanks or service the integrated lighting system.


Although the L-39’s non-servo-actuated nose gear door does not require it, the short delay that occurs between the moment when the landing gear is commanded to deploy/retract and the actual commencing of the action hints at this module’s included landing gear and door-sequencer functionality.

The control module also serves as a point of connection for the factory-installed LED landing lights and navigation lights. The former are switched on whenever the landing gear is deployed, while the latter remain lit whenever the model is powered up. Extra lighting ports are provided on the module, should pilots wish to add additional lights to their L-39.

Multiconductor cables combine all of the electronics embedded in each half of the wing into two easy-to-manage connections. The connector includes aileron and flap servos, the retractable landing gear wiring ,and two lights per wing half. The eight-pin JST-XH-style connectors used on these cables fit snugly into their corresponding receptacles and make it easy for space-challenged pilots to break down this model for storage and transport.


Flying

Although some pilots might be accustomed to carving out foam in order to fit slightly larger battery packs into a model, this jet provides an ample battery bay. Pilots have the option of flying their L-39 using several sizes of six-cell battery packs. The manufacturer’s recommended pack size is between 4,000 and 5,000 mAh; anything less than a 3,700 mAh pack will offer no more than 2- to 3-minute flight durations.

Using a 5,000 mAh Admiral battery and exercising throttle restraint can potentially push flight durations to 4 or 5 minutes. There is no denying that larger-capacity LiPo battery packs can extend flight durations; the associated increase in wing loading will subsequently raise the stall speed of the model. This will result in a pilot having to maintain a slightly higher approach speed on landing and could make the model more susceptible to a high-speed stall if pushed too tightly through the corners.




A generously dimensioned battery compartment facilitates easy experimentation with larger, flight duration-extending LiPo battery packs.


Pilots will want to experiment with different-size batteries to find their own preferred L-39 performance sweet spot. With a 6S 5,000 mAh LiPo battery pack belted in place, the L-39 comes in at an all-up weight of 102.5 ounces (drop tanks not included). The resultant wing cube loading number of 26 would suggest that modelers possess at least an intermediate level of piloting proficiency, but the L-39’s overall benign sport jet flight behavior makes this a model that inexperienced EDF pilots should be able to competently handle.

Pilots can trust the recommended control throws called out in the assembly manual and should initially set up their models using them. A careful eye during installation of all of the control rods and the associated transmitter programming resulted in the review aircraft needing only a few clicks of trim on the pitch axis during the maiden flight.

Intermediate-level pilots will quickly be comfortable with this model. The wide stance of the trailing link suspension-equipped main gear and low rolling resistance of the wheels bode well for pilots flying from grass airfields. With the aircraft properly trimmed out, departures with scalelike rotations and realistic-looking climbouts can be executed using approximately 75% throttle and half flaps.

Pilots will notice that equipping the L-39 with the pair of included magnetically retained drop tanks makes takeoffs slightly more difficult to execute. The added drag of the underwing tanks caused the L-39 to release more abruptly from the runway with a steeper angle of attack. After it is in the air, there is no need to keep the throttle firewalled for the entire flight.

This model cruises efficiently through the air when flown at moderate and reduced throttle settings. Beauty and performance are in the eye of the beholder and relative to each pilot’s preferences and skill level. According to telemetry data gathered from a GPS sensor-equipped EagleTree eLogger, the L-39 is capable of achieving typical top speeds of 105 to 110 mph! In-flight orientation is good to excellent, thanks to the nearly all-white topside and mostly red underside of the Freewing factory-painted graphics scheme.

Twin pilot figures and an abundance of detailed, factory-applied nomenclature graphics result in this aircraft achieving a realistic-looking, scalelike appearance in the air.




The included, factory-installed lighting system features always-on red and green navigation lights and bright white landing lights that are synchronized to the landing gear’s deployment.


Scale models are often slightly lackluster when it comes to performing accurate and attractive-looking aerobatic maneuvers. Although a Scale model at heart, the Freewing Albatros possesses the agility of a sport jet when pushed into aerobatic maneuvers.

When performed on high rates, aileron rolls are notably axial, crisp, and precise. The abundance of thrust produced by the Freewing 80 mm EDF power system pushes the L-39 up and over the top in large, sky-filling loops. Inverted and knife-edge flight can be easily sustained with minimal corrective control input required.

When it is time to land, this model transitions into a gear-down, flaps-down configuration with no perceptible change in pitch attitude. (Freewing recommends a small amount of flap-to-elevator mix in the assembly manual.)


Conclusion

The Freewing L-39 is likely the first mass-produced, EPO foam composition, high blade-count, 80 mm, EDF-powered version of this aircraft to be modeled en masse. The continued widespread use of the Albatros by many countries as a military jet trainer and light attack aircraft, coupled with its popularity in the jet class at the Reno Air Races, means that pilots interested in pursuing a custom graphics scheme have a number of exciting and authentically scale options from which to choose.

Motion RC partners with Callie Graphics to offer pilots easy access to a selection of alternate graphics schemes, all cut using premium, high-quality vinyl. Pilots with access to a 3D printer can ratchet up the model’s impressive, scalelike appearance by dressing out the cockpit using the optional 3D-printed, detailed cockpit set. The 3D files are available from the Motion RC website product page at no charge.

Pilots will also be able to purchase complete, preprinted cockpit upgrade kits if printing them at home is not an option. The Freewing L-39 Albatros stands out as an EDF jet model that Scale enthusiasts and adrenaline-craving, speed-hungry sport jet pilots will likely be happy to add to their hangars!

—Jon Barnes
barnesjonr@yahoo.com


Manufacturer/Distributor:

Freewing/Motion RC
(224) 633-9090
www.motionrc.com


Sources:

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

Callie Graphics
info@calliegraphics.com
www.callie-graphics.com






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