Radian Pro BNF

So this is how R/C aeromodelling is panning out these days is it? Plug and play? Bind and Fly? ARTF in the truest meaning of the acronym. It suits me. ‘Daniel-son’ and I had the Radian Pro up in the air an hour after opening the box and that includes the 30 minute drive to the flying field! Is it just another electric foamie toy or have Parkzone properly done some homework here?

The Radian Pro upgrades the already popular original Radian with a four servo wing, a reduction in dihedral and with extra reinforcement to provide an overall more robust model than the first rudder/elevator version.

Extra partial span wing spars and a new wing mounting system stiffen things up considerably centrally and deliver a 7-function model now designed to make full use of crow braking, camber changing flaps and full span aileron control if your transmitter has the ability to drive them. This Bind and Fly (BNF) version is supplied with a new Spektrum AR600 receiver, a 1300mAh 3S Li-Po flight battery and an in-car charger for same. All servos and linkages are pre-installed and made off properly with servo arms mechanically offset where required to provide some element of differential throw. A set of extension leads is provided as is all associated electronics. The motor and speed controller are pre-installed and a folding prop fitted. The Internet would have us believe that the power train is the same as the original model but I suspect that this outrunner motor is different than the first Radian that passed through the Skunkworks.

A plug and play version exists too which requires the builder to provide his own receiver, flight battery and charger, but that’s it! Like I said – proper ARTF!

Like the first variant, the Radian Pro is manufactured out of Parkzone’s Z-Foam; yet another Expanded Poly Propylene (EPO) variant but of sufficient density to allow good deformation before permanent damage occurs. The fuselage is further strengthened with glass rod longerons set into the outside surface and the Depron type tailplane simply tapes into place so as to be removable if you feel the need. Fitting it in the first place is the only real significant part to the assembly process.

The two-piece wing joins over a hefty carbon tube before screwing into place through plastic fittings with purposeful steel bolts. The whole model can break down again to fit back into the carry box supplied for storage or transport. There really is almost nothing to do to get it into the air. Even the stickers are pre-applied.

With its fully controllable wing, the Radian Pro is pitched at more experienced pilots. Its 480 sized motor, (960kv) 30 Amp speed controller and 1300mAh 3s LiPo battery turn the stock 9.75 x 7.5 prop at 15A for near enough 150 Watts on a fully charged flight pack. This provides a reasonable climb out at around 45 degrees to towline height (circa 200m) in about 30 seconds, where the model can transit to gliding flight (it is designed as a glider – that prop folds for a reason you know).

In dead air there is enough reserve in the supplied battery pack for around 40 minutes of sensible soaring flight. Use it as a constant ‘power on’ model and you’ll find this is significantly less. One modification which almost every user I have come across has made is to increase the prop sixe to something in the order of 11x8 or 12x8 in order to improve the climb rate. Improve things it most certainly does and to be honest transforms the model once again. It’s about the only thing that Parkzone could tweak as standard to improve the supplied model over its current specification.

The provision of the Radian Pro with a 6 channel Spektrum AR600 receiver allows binding up to many and varied Spektrum DSM2 capable radio systems. Opt for a 5-channel set up and you’ll have to cope with flaps on a switch and throttle on the stick. It really isn’t to the detriment of the performance if I’m being honest. A radio with a slider for either flap control or throttle will give you more options for variable wing geometry but without doubt the most can be brought from the model by forgoing the supplied ‘Y’ leads and setting up the wing for full independent servo control.

Our first flight with the Radian was on my son's Spektrum DX7 with flaps on a switch and working independently of any aileron input. Throttle was on the stick and there was no variable camber mixing. The model flew very nicely. We kept it to just one flight so we could say that we did it, but as the battery re-charged I programmed the model onto my Spektrum module fitted Graupner MX22 transmitter and fitted a 7 channel AR7000 receiver. This brought us full crow braking and put the throttle onto the same stick, accessible through the transmitters fancy ‘mix only’ channel function.  Camber and reflex, mixed flap to aileron (though up travel is severely limited on the flaps because of the pre-fitted mechanical offsets on the servo arms), an aileron to flap mix to expand the camber/reflex to full span, snap-flap (which it really does not need) coupled with elevator and for good measure a coupled aileron to rudder mix for better tracked turns without reducing aileron throw via the differential mixes, were all now possible.

This set up is the same as all of my moulded four servo wing gliders and gives great flexibility in flight.
Even though the section is thick and foamie rather than slender and stiff, the model does respond well to wing mixing. Also a little CAR (coupled Aileron and Rudder) mix permits tighter turns for low level thermalling tighter to the core. A little Reflex across the wing picks up speed noticeably. Crow braking slows the model nicely enough but there is not so much down flap travel so it’s not like throwing out an anchor and somewhat surprisingly camber does flatten out the glide and minimise sink when in lift.

So are there any real down sides to the Radian Pro? Well it is most certainly a very fiddly model to rig. The extension leads, whether you keep the model as supplied or split the Y leads, all lie under a small slotted hatch on the underside of the model and room is tight. Connections must be made here and unless you relocate the receiver you may find it easier to plug things straight in. Why would you want to relocate the receiver? Well, that nice little access hatch on the underside of the model also acts as a scoop for grass, water, mud, bugs and general detritus. Many is the time I’ve had to dry the radio bay after a landing on even slightly damp grass. Keep an eye on it. I moved the receiver slightly forwards. Now only the servos and wiring connections get wet! I’m sure the slots in the door could be covered without detriment unless you really vamped up your current draw and needed to proper cooling.

The elevator and rudder are driven by pre fitted snakes. The elevator is a ‘push for up’ arrangement and is more than a little bit reluctant to push at all when airspeed builds up. Internet forums are splattered with stories of Radian Pro’s plummeting to their doom and many blame this linkage. In reality the error should be blamed at the pilot who let the speed build up so much that the elevator linkage simply won’t ‘elevate’. To be fair you do get quite a warning unless you dive the model vertically. Firstly the wing tip dihedral will flatten out and eventually become anhedral with the rest of the wing. If pushed further then the wing tips will begin to twist under and tuck downwards. It is at this point that you may suddenly notice the fading of the elevator control.

Assuming you have enough height to pull out you will notice that it will do so slowly provided you do not push your speed much above the flat wing 'tucky tips' point. If you do you'll discover that not only might you need a change of underwear but that the only method of recovery now open to you is to throw in full crow braking and hope for the best. Obviously the recommended course of action would be to avoid this corner of the flight envelope at all costs. The Radio Pro is not a hotliner or even a warm liner. Tepid tiner perhaps? Foamie thermal soarer certainly. Stick with its knitting. Don’t over stress it, keep the airspeed down and enjoy its cruising performance and decent thermal soaring ability.

As a comparison I think it has the edge over the Easy Glider (I have both) but obviously not the performance of a non-foam model. It is a nice bounce about electric assist glider that won’t break the bank and will make a nice entry level model for the UK e-soaring scene if that’s your bag.

The Parkzone Radian Pro is distributed throughout the UK by Horizon Hobby UK.

Wingspan:  2000mm (78.5 in)
Length:  1140mm (45.0 in)
Weight:  980 g (34.6 oz)
Speed control:  E-Flite PRO 30A ESC (installed)
Motor:  480 BL 960 KV Outrunner (installed)
Servos:  PKZ SV 80 sport servos (6 installed)
Receiver:  AR600 DSM2 (installed BNF)
Requires:  DSM2 transmitter
Approx street price: £180 (BNF), £130 (PNP)