Radio Control Jets
Jim Hiller [[email protected]]
Jet events bring out new and exciting products
During the summer I attended three jet events in four weekends; I love our flying season! The people involved in setting up and running these events did a great job, and the sites allowed for great jet flying.
The meets included the Bluegrass Jet Jam, the Flying Aeros Jet Jam, and Jets Over the Heartland. The host clubs were extremely involved. I definitely feel in the jet zone now!
Event sites and organizers
- Bluegrass Jet Jam — organized by Mike Kirby and the Southern Kentucky Model Aero Club (SKYMAC) at its own flying field. The site has a 1,000-foot paved runway and the club consists of a great group of guys.
- Flying Aeros Jet Jam — run by Joe Lewis and the Flying Aeros Association at the Braceville Airport (Ohio). That private facility strongly supports aviation of all types, including an Experimental Aircraft Association chapter and model aircraft.
- Jets Over the Heartland — run by Tim Redelman and the Winamac Aero Modelers at another incredible flying site dedicated to model aircraft.
I compliment our jet-modeling industry for the strong support it gave these events. Special kudos go to AMT, JetCentral, and JetCat for helping fund them.
JetCentral and the new Turbo Prop
Eric Clapp of JetCentral brought the company’s complete line of turbines to Winamac; they were nicely packaged and complete for all to see. Sitting at the end of the table was the new Turbo Prop, ready for delivery.
JetCentral builds its Turbo Prop based on the Super Bee core with an attractive turbine gearbox power package. The complete unit weighs 5 pounds with the starter. The Turbo Prop turns a 26-inch, two-blade propeller with the turbine running at 180,000 rpm. The setup is sold with all the normal accessories, for example:
- fuel pump
- ECU (electronic control unit)
- Hand Data Terminal
- fuel valves
- six-cell, 1400 mAh battery pack
A few months earlier I spoke with Felipe Nieto of JetCentral about this Turbo Prop, and he was proud of how well flight testing had been progressing. He told me he would introduce the Turbo Prop to market as soon as he was assured it would be a reliable, strong addition to the JetCentral line. (JetCentral turbines carry a lifetime warranty.) The movies Felipe showed included his giant-scale aerobatic model flying with authority and good throttle response. The Turbo Prop should make a strong addition to the JetCentral lineup. For additional information about this engine and JetCentral’s complete lineup of turbines, visit www.jetartes.com.
Bob Violett’s Electra Jet
Bob Violett flew his new Electra Jet at Jets Over the Heartland. I hadn’t seen his electric ducted fans fly for approximately six months, and I compliment him on the performance improvements. The Electra Jet is an excellent airframe—well matched to electric fan power—and Bob knows how to show it off. He has the skills to display extreme flight with this model.
Battery options continue to improve, and the Electra Jet has the room to accept them. Although it lacks the smell and sound of a turbine, it isn’t deficient in performance. This model would make a great jet for fields with noise restrictions or when turbine flying is curtailed because of drought conditions. Information about the Electra Jet can be found at Bob Violett Models’ website: www.bvmjets.com.
JR Spektrum systems — new radio technology
The JR Spektrum systems have hit the jet-modeling community in a big way. A disappointing beginning was followed by many successes. When properly set up in a jet, this new technology works extremely well.
During a rain delay at Jets Over the Heartland, Jeff Hollsinger and Erik Meyers held an informative seminar on this new technology, explaining its operation and the new terms and products we will be dealing with. They covered in detail how to set up a JR Spektrum module in a JR 10X-series radio.
There are two important issues of concern:
- Reliable voltage source — If the voltage goes too low for even an instant, the computer-technology–based receiver will reboot, leaving you with no control for an extended period of time.
- Antenna placement — where it is located, its orientation, and how many you have. Additional antennas are readily available and can be installed to improve difficult installations or boost signal reception. A typical jet installation will have two receivers: the primary with two antennas and a remote with one antenna.
Jeff strongly recommends spending the extra $25 for the Flight Logger for peace of mind. This device stays plugged into the receiver to record fades, frames, and lockouts, as well as serving as an onboard voltage gauge for your receiver battery.
- Fade — a loss of usable signal by a receiver, with each receiver’s performance recorded individually. It is common to see a large number of fades without radio performance being affected.
- Loss of frames — losing all receiver signals simultaneously for a period of one frame. This total should be a low number of occurrences.
- Lockout — when the system loses frames in a row, the radio goes into lockout and initiates your failsafe settings. I have not seen a recorded lockout displayed yet on the jet models I have observed.
This explanation should whet your appetite for the Spektrum and all the terminology that goes along with understanding how to effectively use and enjoy this new technology. If you make the jump to Spektrum radios, you are well advised to learn the system from experts such as Jeff and Erik.
Many new manufacturers — buyer beware
One thing I have noticed at these jet meets is the number of new jet manufacturers and their variety of scale models being introduced at a breathtaking pace. They look impressive in the magazines, but not all look as good at the flying field.
This large array of jets is not always developed to the extent we are accustomed to with the mainstream jet manufacturers. It puts the responsibility for success on the builder/pilot’s experience and knowledge.
I am occasionally surprised by some models' poor-quality workmanship, questionable system layouts, and general weakness of aerodynamic design. Because it looks like a jet doesn't make it equal. Buyer beware!
What to inspect — flight-surface installation and airframe rigidity
One area to consider closely is flight-surface installation. The three main issues to consider are:
- How solidly the surfaces are attached to the airframe.
- How solid the control-horn attachment is.
- How rigid the airframe is.
These issues relate to the ability to handle flight loads and to resist flutter. A firm, strongly attached control surface must handle the air loads and servo loads without failing in flight and causing loss of control. In modeling we generally accept a rigid installation—particularly the control linkages—as an acceptable method of containing flutter.
Note that I did not write "eliminating" flutter. The best control linkage, best servo, and most powerful batteries will not contain flutter if the basic airframe itself is not rigid enough not to flex and flutter.
Poor-quality glue joints in the trailing-edge (TE) spar to wing skin, fin skin, or stabilizer skins have resulted in the loss of many aircraft because of airframe flutter. Take the time to inspect these areas of the model.
Flying stabilizers
I love models with flying stabilizers. They are simple, work exceedingly well, and in many cases match the full-scale model for scale purposes.
What should we watch for?
- Pivot point location — flying-stabilizer loads are greatly affected by the pivot point. If the pivot is too far aft, the stabilizer may not want to stay straight near center and the model can hunt in level flight. This can be corrected by moving the pivot point forward.
- Servo selection and linkages — a more common fix for centering problems is to use a stronger digital servo with rigid linkages to combat centering forces and forcibly hold the stabilizer in position. A flying stabilizer induces a load on the servo in most designs.
In all the F-18s I have flown there has been a couple degrees negative incidence when trimmed for level flight. This position was held by the servo, and in one case on a ducted-fan model that servo wasn't powerful enough. I initially believed the model was tail-heavy because it climbed poorly when I slowed it down. It took a couple flights before I tried a different elevator servo, and as simple as that the problem was cured. The new servo wasn't rated as more powerful than the original, but it had more centering power, so it worked better and fixed the model's flight problems.
Final thoughts
I hope this keeps you thinking about your model's setup so you can be successful. Flying jets is fun and crashing is not fun. See you at the field. MA
Transcribed from original scans by AI. Minor OCR errors may remain.
