What a wonderful time to be involved in RC helicopters or model aircraft in general! I’m dating myself, but when I first started flying helicopters, hovering twice in the same day and taking a helicopter home in one piece was a major accomplishment. The two or three people in the country who could hover nose-in were guaranteed a spot on the podium at the AMA Nats. Today, we have lightweight models and radio systems with components that we could only have dreamed about 10 years ago.
The good news is that we have plenty of choices in every size, shape, and power system, and it seems as though new models are entering the market daily. The bad news is that we have so many choices available that sometimes narrowing the list to a final purchase is overwhelming. Thankfully, most of the hobby-grade helicopters are high quality, so it’s difficult to make a poor choice—you simply need to find the one that meets your needs and desires.
The Agile 5.5 is the first 550-size helicopter that I have owned. My club field is home to a number of active helicopter pilots, including a couple of members of various teams. Between helping others and watching what the team pilots are flying, I’ve been exposed to a large variety of helicopters. The 550-size has piqued my interest because it has the power and presence in the air of larger models but with a more modest cost, especially in the battery department.
Since I attended the Orlando Helicopter Blowout, I have had the itch to fly helicopters more often. I have done several airplane reviews recently and, consequently, my helicopter skills are slipping because of lack of practice. I wanted something that was small enough to carry in the truck with my other projects, and electric powered so that I could get a few flights in during each flying session without hauling around all of the support equipment required to fly nitro.
I ran into Allen Bryan from KDS Models USA at the Orlando Helicopter Blowout. The company had a tent with a number of helicopters on display, including the Agile 7.2 and its new little brother, the Agile 5.5. Allen is the CEO of KDS Models USA, which is located in a large distribution warehouse in Houston.
After watching factory pilot JaeHong Lee successfully fly a 5.5 during a noon demo, I sat down in the KDS tent with Allen to discuss the new Agile 5.5. I wanted to learn what it brought to a fairly crowded market, and to shake hands on an agreement to receive one of the new kits for review.
I was curious about what made the Agile different from the growing number of helicopters in the 550 class of electric-powered helicopters. Roberto Gaziano, who designs robotics for media and military applications, used his talent to design the Agile series. Two years of development and testing—which included Roberto’s engineering talent and JaeHong Lee’s extensive flight testing of the prototypes—were needed to bring the Agile 5.5 to the market.
Its unique features include the two-stage belt-drive system and the high-quality components that result in a rigid airframe. KDS, a major supplier of CNC components, tools, and electronics for the RC industry, manufactures nearly all the components for the Agile up to and including the screws, so there is quality parts control from beginning to end.
First Impressions
My first impression when unpacking and examining the Agile was that everything was well organized—very well organized. The larger parts were nicely arranged in molded trays with a spot for each part. Unlike other kits, the Agile screws and small hardware are bagged by size and type. All of the socket head M3 x 10 screws are in one bag. Everything was easy to find.
The parts appeared to be high quality. I have owned several helicopters throughout the years and found JR helis to be the standard for assessing quality. The KDS parts are on par with the JR parts. The frames are 2mm-thick carbon and are smooth and nicely matte finished. I detected no edges resembling steak knives.
The machine work on the Delrin plastic parts, metal gears, and aluminum parts appeared to be outstanding with no discernable machine debris on the parts or in the threads.
Providing no printed manual is a double-edged sword. Customers downloading the manual at the time they start the build means that, in theory, they should always have the most current version of the document with any changes already incorporated. I’m all about technology—I deal with it for a living—but I don’t like building with my iPad as the instruction manual and prefer a printed manual.
The Agile isn’t a beginner’s helicopter, but the manual is straightforward. Although it’s not a difficult build, the manual assumes that the builder has some prior helicopter assembly experience. The manual has plenty of diagrams and accompanying notes with each step. I read each section thoroughly before assembling the Agile.
The Agile is available as a kit—allowing the builder to choose each component such as the flybarless controller, servos, electric motor, ESC, radio system, and batteries. Also available (and the subject of this review) is the Agile 5.5 combo that includes the motor, servos, and flybarless controller. All you need are the transmitter and receiver, a 120-amp ESC, and your favorite batteries. Both kits come with carbon-fiber main and tail blades.
The Agile kit isn’t inexpensive, but when you add up all of the components that you would have to purchase separately and consider the quality of the entire package, the price point makes sense. One advantage of the combo kit is that all of the components are carefully chosen to work together, so little guessing is required.
When examining other components, I found spiral-cut gears at all of the power transfer points, as well as a bearing-supported torque-tube tail drive. On the subject of bearings, the main shaft is supported by three bearings riding in machined aluminum bearing blocks. The tail gears are titanium coated to reduce wear for a long life.
The front end is enclosed in a nice fiberglass canopy that is held in place with four cotter pins for easy removal and installation. An optional bright green canopy is available for an eye-popping finish. After seeing the factory pilots fly the Agile 5.5, I was excited to get started and get it into the air.
Construction
Building the Agile 5.5 isn’t difficult, but take your time and build it carefully and precisely. I used Z-42 threadlocker and Pacer Z-Poxy from Frank Tiano Enterprises to assemble the Agile. It always takes more time to document a review build. I estimate that it would take approximately 5 to 7 hours to build and set up another Agile.
You first need to clean all of the screws with acetone and use medium-strength blue threadlocker on all metal-to-metal connections. Most screws ship with an oil-based preservative. Cleaning them with a solvent ensures proper threadlocker adhesion. Apply a few drops of a light machine or air-tool oil on all sliding metal surfaces such as the swashplate and tail pitch slider.
The torque-tube ends and boom-support ends get attached with 30-minute epoxy. I scuffed the ends with sandpaper, and the internal gluing surfaces with a small file.
The tail-drive bearing holders can be somewhat difficult to install in the carbon-fiber tailboom. To overcome this challenge during assembly, I glued the inner face of the bearing to the torque tube then used Teflon Silicon Lubricant from DuPont (available at local home improvement stores) on the rubber bearing holders. After the bearing holders were lubricated, the entire assembly slid into the tailboom.
When assembling the main rotor head, I noticed that KDS included thin shims in case you find any play. My Agile had none, but this is a nice touch, and if anything wears over time I will have the parts to tighten things.
The frame assembly and servo installation went according to the manual with no difficulties or exceptions. The landing gear is six pieces, which isn’t any better or worse than other models, but it’s different from the standard four pieces consisting of two crossbraces and two skids. I’ve seen this configuration before, but it’s definitely not the norm.
I was intrigued by the KDS EBAR V2 flybarless system that was included in the combo kit. Plenty of testing, development, and pilot input went into the V2, and the result is a reasonably priced and easy to set up virtual flybar system. The EBAR includes a field programmer that plugs into the unit and allows you to easily make changes without a laptop computer. You can stick it in your pocket when you’re flying, land, and make immediate adjustments—allowing you to get the Agile set up for your flying style in a short amount of time.
The EBAR programming box also allows you to save model settings so you can restore an older setup if you find that you did some ill-advised tinkering, or to transfer the setup to another EBAR unit. All you need to run it is a simple six-channel radio. No fancy helicopter mixing is required.
One of my favorite features of the KDS EBAR is that you can use one of three preset modes: Precise, Medium, and Vivid. Precise mode is the tamest setup with more gain and a less-aggressive control response. Medium mode is for pilots who want good performance without getting carried away. The hotshots use Vivid mode because it has the least gain, the least stability, and the most aggressive control response.
You can also adjust your EBAR to feel more or less like a flybar—or anywhere in between. I would equate Precise to adding weights to a flybar for a beginner, Medium to moving the weights in or removing them, and Vivid as going to ultralight paddles.
In addition to the included electronics, I used a Futaba 8FG transmitter with a six-channel FASST receiver and an OptiPOWER 2S 2,200 mAh receiver pack to power the electronics. The motor power was provided by an OptiPOWER 6S 5,000 mAh and a KDS 6S 5,000 mAh pack. A Castle Creations 120-amp speed controller was used to move the electrons from battery to motor.
Flying
Most of my larger helicopters are glow-fuel powered models and my aerobatic electric-powered models have typically been 450 size and below. This was my first larger electric heli and I was excited and slightly nervous to give it a few shakedown flights.
The first time I flew the Agile, a cold front had apparently wandered into Florida by mistake. It was in the high 40s, with winds at 15 mph and gusting to 20 mph. The combination of new model jitters and cold fingers made me nervous. The Agile was so nice that I didn’t want to wreck it and test KDS USA’s parts support.
After flying one of the KDS models at the Orlando event, which was set up with 14° of collective and 9° of cyclic pitch, I realized that I wanted a tamer setup because of my lack of recent 3-D helicopter flying experience. I opted for +/- 12° of collective pitch throw and 8° of cyclic. I knew that tweaking the setup as I got comfortable would be simple with the EBAR programming unit. My head speeds were set to 2,100 rpm in Idle Up 1, and 2,600 rpm in Idle Up 2.
The first thing that surprised me about the Agile was how stable it was—even in the prevailing winds. In Idle Up 1, the Agile felt solid without being twitchy. The solid feel gave me confidence to fly around and get accustomed to the helicopter. I didn’t try much in the way of aerobatics, but two things stood out that day: the Agile was stable even in the wind and it was fast, especially moving downwind.
I’ve found that higher airspeeds tend to reveal any bobble or instability in the rotor-head design or the flybarless control unit. The Agile exhibited no bad tendencies and the EBAR maintained a good balance of quickness and stability. As a result, I was quickly gaining confidence in myself and the model.
I don’t have an IR thermometer gun anymore, but after my first flight the motor was warm, not hot. The OptiPOWER pack was barely warm to the touch. The KDS pack performed similarly and I was beginning to understand why the Agile 5.5 wasn’t having difficulty with 14° of pitch and 2,600 rpm. At 2,100 and 12°, I was barely working the Agile’s power system.
On a calmer, warmer day I decided to put the Agile through some paces. Even at 2,100 rpm, the heli could be flown aggressively. It felt solid and locked in through everything that I did. My JR Vibe 50 once made my flying take one of those leaps, but looking back, it simply gave me the confidence to push my flying. It never did anything other than what I asked it to do.
The Agile is the same—every battery pack I went through I flew better and things started quickly coming back to me. I know this is a tired phrase in helicopter reviews, but the Agile really does fly “like it’s on rails.” It weighs slightly more than some of the models in this class, but I suspect that the extra weight adds to the model’s stability instead of taking away from its performance.
I noticed when I started doing funnels and hurricanes that the tail was shuddering. Here’s where the EBAR controller is great. Simply land, tweak the gain, and get back in the air to test. I had the entire helicopter tuned to my liking in the time it took to exhaust two battery packs. Each time I landed, the Agile seemed to ask, “Is that all you’ve got?”
After flying sessions, I inspected the entire airframe looking for loose fasteners, wear in the linkages, or dust from the belt and gears, but found the airframe to be in pristine condition.
I loaded a more aggressive setup into the EBAR and turned over the transmitter to a few pros during a helicopter fly-in in Daytona Beach, Florida, to see what the Agile could do in talented hands. I watched as it was put through a demanding series of maneuvers that my brain could barely keep up with.
High-speed, high-energy, pirouetting Tic-Tocks were no problem! Piro-flips into reversing piro-flips—the Agile did everything I knew the name of and a few things that I didn’t. What I did know is that it appeared in control the entire time with no bobbling in the head or tail. Even after these flights in warmer weather, the batteries and motor stayed well within safe temperature limits.
Bobby Smith said it was “ … very smooth. The drive system is quiet, and the control system is very responsive. The model feels solid and doesn’t feel heavy. The motor doesn’t seem to break a sweat.”
Jeremy Strickland said, “KDS models feel smooth and the response to the controls is very linear. The Agile 5.5, like its big brother the Agile 7.2, is no exception.”
Conclusion
Agile is an adjective meaning quick and well-coordinated in movement; lithe; active; lively. I would say the KDS Agile 5.5 definitely meets and exceeds the definition!
I found the aircraft responsive and solid. The combo kit’s components are engineered for performance and satisfaction—a welcome departure from combo deals that are put together with the sole objective of saving money by using marginal components. The high-quality components have withstood my sedate flying style without missing a beat.
Although it’s not an inexpensive kit, the KDS Agile 5.5 is well engineered and appears to be assembled using high-quality components for an uncompromising final product.
