E-flite UMX Gee Bee R2

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E-flite UMX Gee Bee R2
The Gee Bee's micro outrunner motor and AS3X motherboard with its built-in rudder and elevator servos
The battery and charger supplied with the Gee Bee. A 12V external power supply may be used
Operational full-scale replica which served as the basis for the model on display at Fantasy of Flight, Polk City, Florida USA. Photo: Wikimedia Commons

The E-flite UMX Gee Bee R2 is an outdoor-only foam ultra micro-sized scale air racer designed, manufactured and distributed by E-flite, a division of Horizon Hobby of Champaign, Illinois USA.

Introduced in January 2012, the Gee Bee R2 features Horizon's AS3X technology. This three-axis MEMS-based gyroscopic technology is similar to that found in flybarless helicopters and has been adapted to micro airplanes. It makes constant rapid, minute corrections to all control surfaces while in flight. The result is a micro model with the feel, manuverability and aerobatic capability of a giant scale model; indeed, a Gee Bee in this scale would likely be impossible to fly without the aid of the AS3X system. It is a BNF bind-and-fly model which is bindable to any Spektrum or JR DSM2 or DSMX transmitter. A transmitter with dual rates is recommended. It will bind to the transmitter's default modes with no need to reverse servo direction or to change end points. Futaba radios equipped with a Spektrum RF module will work as well, but the throttle channel must be reversed. Recommended throws are 70% low rate and 100% high rate for all control surfaces. Recommended exponential is 10% on the elevator at high rate.

An E-flite 200mAh 2S 7.4v 25C lithium polymer battery (EFLB2002S25) and Celectra (EFLUC1007) DC charger are provided. Since the plug and receptacle are unique to E-flite micro aircraft and Team Losi micro vehicles, a charger plug adapter (EFLA7001UM) is available for those wishing to use their existing banana plug-equipped charger.

Spare hook-and-loop fastener strips for the battery are provided along with a detailed instruction manual in English, German, French and Italian.

As of February 2013, the retail price has dramatically dropped from US$169.99 to an average of $64.99 depending on the vendor, signaling a possible early discontinuation of the model.


The model, designed by longtime Horizon Hobby designer David Payne, is based on a 1991 replica of the famous 1932 Granville Brothers R2 pylon racer built by Steve Wolf and Delmar Benjamin. Benjamin flew an aerobatic routine in this aircraft at numerous airshows until he retired the aircraft in 2002; his is the pilot's name on the model. This aircraft is now owned by museum curator Kermit Weeks and was placed on display at his Fantasy of Flight in Polk City, Florida in 2004. The replica is shown in the photograph at right and Weeks is shown on the model's box standing in front of the replica while holding the model.

Flight characteristics

The 3000Kv motor pulls the Gee Bee into the air within a very short length of runway. Though faster than its stablemate, the Beast 3D, the Gee Bee is somewhat less aerobatic. Like the prototype, the Gee Bee is built for speed and will turn in as hard and as fast as the pilot wishes. Plenty of power is on tap for loops and other basic aerobatics including knife edge and inverted flight, but the roll rate is slower than that of the Beast.

A lack of speed is not an issue; estimated top speed is 50 MPH (80km/h) based on propeller speed, 75% motor efficiency and airframe drag.

According to Horizon Hobby, a new, freshly charged battery may force the over-current protection system on early production models to engage at or near full throttle, possibly causing a crash at takeoff. Designed to shut down the throttle in the event of a jammed propeller, the OCP system can be overridden for normal flight by carefully holding the model and operating the throttle below the cut off point for ten to fifteen seconds to lower a freshly charged pack's voltage prior to takeoff.

Most models of the Gee Bee are difficult to fly due to the short wings, close wing/stabilizer incidence and small control surfaces. A model this size might be unthinkable without the aid of AS3X, but with the aid, the Gee Bee flies and tracks like a far larger model. The prototype's fuselage acted as a sort of airfoil; the model's fuselage may act in much the same way. Wing loading may appear to be an issue, but the Gee Bee's light weight means easily controlled, long glides upon landing. Slight application of power assures gentle, three-point landings.

The model should be landed immediately upon loss of power. In order to prevent damage to the battery by overdischarge, the motherboard is programmed to operate the motor in short bursts when the individual cell voltage approaches 3V. This lack of power might increase the difficulty of landing the model.

Although E-flite recommends the Gee Bee be flown outdoors, Horizon Hobby representatives put on indoor demonstrations of display samples shown at the 2012 and 2013 Academy of Model Aeronautics Expositions in Ontario, California USA.


  • Wingspan: 20.1" (510mm)
  • Length: 13.9" (352mm)
  • Wing area: 72.5 sq. in. (4.7 sq. dm.)
  • Flying weight: 3.60 oz (102 g)
  • Motor: E-flite 180-size 3000Kv brushless outrunner
  • Radio: Four-channel minimum Spektrum or JR, DSM2 or DSMX compatible transmitter
  • Servos: Four 2.3g high-speed linear long throw
  • Construction: Expanded polystyrene foam inlaid with composite reinforcement and carbon fiber bracing
  • Trim scheme: Red and white Granville Brothers racing livery depicting the 1991 replica
  • Propeller: 5.25 x 3.5 electric
  • Battery: E-flite 2S 200 mAh 25C lithium polymer (included)
  • Approximate flight time: Four minutes
  • Charger: Celectra DC-powered 2S lithium polymer (included)
  • Minimum age recommendation: 14 years
  • Minimum experience level: Intermediate
  • Catalog number: EFLU4580
  • Price (USD): $64.99

External links and references