E-flite UMX FPV Radian BNF
The UMX FPV Radian is a smooth, easy-flying airplane. Rookie FPV pilots should have no trouble adjusting to the nuances of flying with goggles.
By Terry Dunn.
A Radian with a view
Photos by Terry Dunn.
As seen in the Winter 2016 edition of Park Pilot
• Type: RTF ultra-micro FPV glider
• Skill level: Beginner
• Wingspan: 28.7 inches
• Weight: 1.7 ounces
• Price: $189.99
• Info: e-fliterc.com
• AS3X technology provides outstanding stability
• Spektrum VA1100 ultra-micro FPV system (included)
• Fat Shark 5.8 GHz FPV headset compatible
• Three-channel control for easy flying and friendly soaring characteristics
• One-piece, removable wing with carbon-fiber support
Not so long ago, anyone who wanted to experience FPV (First-Person View) flying had to gather the components necessary to transmit and receive a video signal, obtain an amateur radio license in order to operate the equipment, and then put it all into a model large enough to carry the load. Recent technological advances have made the cost and complexity of entering FPV much lower. Using Spektrum’s integrated and miniaturized FPV components, even ultra-micro RC models can be used to experience the thrill of flying with a bird’s-eye view.
The original Radian-powered sailplane has been hugely popular among park flyers because of its gentle flying traits and resilient construction. Likewise, the downsized UMX (ultra-micro) Radian was quickly adopted by indoor fliers. The new FPV version of the UMX Radian combines this proven airframe with the aforementioned Spektrum FPV components. The result is an FPV model that is easy to handle and can be flown nearly anywhere.
The UMX FPV Radian is available only in the BNF (Bind-N-Fly) version. You need to provide a full-range DSM2/DSMX-compatible transmitter. You will also have to provide goggles or a monitor to receive the 5.8 GHz video signal from the airplane.
I’ve used two sets of goggles with this model. One is the Fat Shark Teleporter V4 (fatshark.com) that was included with my ultra-micro FPV Vapor (see the review in the spring 2015 issue of Park Pilot). I’ve also used the Skyzone FPV goggles (skyzonehobby.com). Both perform equally well in this application.
As with most UMX models, little assembly is required. The foam airframe is factory built, with the radio components, power system, pushrods, and even decals already in place. In fact, my only complaint with this model concerns the decals. Although most were smooth, those on the curved part of the upper wing surface were excessively wrinkled.
The receiver, ESC, and both servos are all integrated into a single component (commonly called a brick). On the UMX FPV Radian, the brick also features AS3X stabilization, which helps to combat the effects of wind and bumpy air. The brick is buried inside of the fuselage with no access to anything other than the battery lead.
The airplane is propelled by a geared 8.5mm brushed motor that spins a 5-inch folding propeller. The propeller blades are made of clear plastic that doesn’t impede the visibility of the forward-facing FPV camera. A single-cell 150 mAh 25C LiPo battery powers the model and FPV equipment.
The slender wing must be inserted through a slot in the fuselage. Two small screws hold it in position. The only other component to add is the tiny FPV camera/video transmitter. The bottom of the camera’s base matches the contour of the upper fuselage. I used the included two-sided tape to affix the unit in place, paying close attention to set the correct alignment.
The low parts count reveals how little work is required to get the UMX FPV Radian airworthy.
A single-cell 150 mAh LiPo battery powers both the model and the onboard FPV system.
It is worth noting that an FCC license is not required to operate this FPV equipment. Although its range is somewhat limited, that isn’t much of a factor with the Radian. Given the airplane’s small size, you won’t want to venture far. You’ll be fine as long as you keep the model close enough for your spotter to clearly see it.
I linked the Radian to my Spektrum DX8 transmitter and followed the control throw suggestions listed in the manual. The entire process required only a few minutes of simple programming. I also verified that the stabilization system was operating correctly.
With the battery placed near the rear of its mounting area, I was able to achieve the suggested center of gravity without adding ballast. I measured the ready-to-fly weight and found it to be 48 grams (1.7 ounces), which is just shy of the advertised weight.
I didn’t wear the goggles for my initial flights with the UMX FPV Radian. Logging a few flights via line of sight gave me the opportunity to trim it out and gather a feel for its handling qualities. Now with dozens of flights in the logbook, I am just as apt to fly with or without goggles. Both methods are fun.
Every Radian flight begins with a gentle hand launch. You won’t need an assistant. It’s as easy as throwing a paper airplane. I usually add power before the launch. It is just as effective to throw the model with the motor off and then spool it up to climb away.
At full power, the UMX FPV Radian will maintain a steady, gentle climb. After a few quick circuits, the model is usually at a good height to shut down the motor for gliding. When the throttle is at idle, the propeller blades fold back to decrease drag. I enjoy the challenge of extending the Radian’s unpowered descents for as long as I can. Be careful if you catch a thermal because the camera system could drain the battery while you’re gliding.
The Radian can be a fun aircraft for cruising around at partial throttle. For this kind of flying, you might need no more room than a basketball court (indoor or outdoor), but having more space will allow greater freedom of movement. A park near my home has a few acres of open field. Although it’s too confined even for some of my moderately sized park flyers, it is perfect for the UMX FPV Radian.
This model has a bit of aerobatic capability. With a preliminary, speed-building dive, the Radian will pull through a respectable loop. I’ve even been able to sustain inverted flight.
The AS3X stabilization makes the tiny Radian behave like a larger airplane and allows it to be flown in a light wind, but gusty breezes will definitely knock it around. The real limit to the wind conditions it can tolerate is its relatively slow speed. Before launching, make sure that you can make forward progress into the wind!
I’ve flown standard UMX Radians on several occasions and I’m sure that the weight and drag of the video gear detracts somewhat from the performance of the FPV version. My senses, however, are not calibrated precisely enough to detect any significant differences in climb, glide performance, or aerobatics.
The camera system pulls 300 mA of current, which is significant when using a 150 mAh battery. This certainly reduces the flight times. I estimate that you lose roughly one or two minutes per flight because of the FPV gear.
For FPV flying, the kit includes a tiny camera/video transmitter that attaches to the top of the fuselage. You must provide goggles or a monitor to view the video.
Flying the UMX FPV Radian with goggles is easy, thanks to the airplane’s slow speed and smooth maneuvers. If you’re new to FPV, this is a good way to adjust to the restricted field of view and reduced situational awareness that comes with goggle-based piloting. Of course, your spotter is there to help fill in the blanks, but it helps to have an airplane that moves slowly and isn’t demanding to fly.
Recording Your Flights
The incredibly small size and weight of the Spektrum VA1100 FPV system lets you fly FPV with some amazingly small models. One of the tradeoffs for using such tiny aircraft is that they are often unable to carry the extra weight of a secondary camera to record the flight. The only way to save footage is to record the downlinked video stream.
Although there are many ways to do this, one of the easiest is to use an integrated video receiver and digital video recorder. I’ve been using the Lumenier DX800 from GetFPV (getfpv.com). It has a 32-channel 5.8 GHz receiver, so it can pick up the video downlink from the Spektrum unit. The video is displayed on a 5-inch LCD screen. A foldout sunshade is included to make the screen easier to see on sunny days.
When the DX800 has locked onto the desired video signal, you simply press the record button to save the video to a micro SD memory card. The Spektrum camera transmits at relatively low resolution, so don’t expect cinema-quality footage. Even so, I still enjoy recording and watching flight videos that are shot at places where only ultra-micro airplanes can go.
When done correctly, FPV is a safe, fun, and exciting way to experience RC flight. The simplicity and small size of the UMX FPV Radian makes FPV accessible to more people in more places. If FPV flying is on your RC bucket list, this model provides an easy-flying, low-risk way to have a go at it.