The Hirobo XRB Sky Robo is a ready-to-fly radio-controlled micro-helicopter designed, manufactured and distributed by Hirobo Limited of Japan. It is similar in design and execution to the Megatech Housefly, Venom Air Corps Ocean Rescue and Walkera RC-54.
Introduced in 2004 and modeled after a full-scale, Swiss-made Lama two-man helicopter, the XRB Sky Robo is a radio-controlled version of the tether-controlled Sky Robo. Both models share the same cabin, tail boom and blades, but the frames are different, meaning a tether-controlled model cannot be converted to R/C. It is intended for use indoors with its "furniture friendly" Styrofoam blades and should never be flown outdoors due to its light weight. Aftermarket composite blades may be fitted for outdoor use, but modifications of any kind are discouraged by the factory.
The Sky Robo is powered by two 180-series coreless electric motors operating counter-rotating coaxial main blades. A non-functional, unpowered tail rotor serves as scale detail and serves to help balance the model. Onboard electronics are proprietary to Hirobo but may be operated with Futaba, JR, Graupner, Multiplex or Sanwa PPM transmitters. A small selector dial on the helicopter is used to switch between the different transmitter settings, which is mainly affecting the channel assignments to match those of the different radio manufacturers. There is a version sold without transmitter for those wishing to fly the Sky Robo with their own radio. Adjustments to cyclic and rudder are performed via potentiometers on the model itself while pitch is mechanically adjusted via a control link connecting the upper rotor with the flybar.
Like the E-flite Blade CX and other coaxial helicopters, the Hirobo XRB Sky Robo is extremely stable, sacrificing forward flight for stability. As such, it is an excellent if slightly pricey choice for first-time users as well as experienced pilots looking for a helicopter suitable for use in limited indoor space. Lighter flybar weights are included for advanced pilots wishing for more response at the cost of some stability. Alternate mounting points are provided for the pitch control link which further increses responsiveness. Due to the design of the coaxial rotors that are located relatively far above the fuselage, the XRB has a tentency to stabilize itself as if it was tethered at the top of the mast. It is not possible to achieve fast forward speeds, but thanks to the fact that only the lower blades are steered it can do quite fast counter-clockwise circles - yet the XRB is unable to do speedy clockwise circles. The self-stabilizing characteristics of the XRB make it a good beginner helicopter, as the pilot-in-training can concentrate on getting familiar with orientation situations (like nose-in hover) and the effects of the various controls, without having to keep the craft in balance as is the case with the other RC helicopters.
A lithium polymer battery pack with an unusual three-lead connector is standard as is an AC wall charger, but a standard two-lead battery may be used.
Unlike the Blade with its composite construction, the Sky Robo is constructed of styrene plastic. The Styrofoam main blades are easily balanced with the help of ordinary transparent tape and the Sky Robo's included balancer. Proper balancing and tracking of the rotor blades is vital for smooth flying, since the low weight of the XRB means that even small imbalances in the blades cause feelable effects.
The rotor blades are designed to protect furnishings and humans/pets by breaking or deforming on impact; repair is not recommended. Several top and bottom blades are included with the model and replacements are both inexpensive and readily available. Training skids are included as well.
- Rotor span: 350mm
- Weight: 195g
- Overall length: 360mm
- Overall height: 160mm
- Gear ratio: 9.857:1
- Included radio system Four-channel FM analog; available in the 72 MHz band in North America, the 35 MHz band in Europe and the 40 MHz band in Asia
- Drive motors: XRB coreless
- Standard battery pack: 7.4V, 720mAh li-po
- Charger input: 100-240VAC, 50-60Hz
- Charger output: 8.4V, 0.65A
- Retail/street price (RTF): US$350.00/$300.00