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May 12, 2013, 03:54 PM
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Experiences with Orange RX3 flight stabilizers (V1 and V2)

Experiences with Orange RX3 flight stabilizers (V1 and V2)

After reading the RC group thread in 2012 I ordered 3 stabilizers before V2 came on the market. As you might be aware of through my other blog pages on this forum, I mostly fly enhanced foam scale models which are often critical under anything but very smooth calm air. Those systems had been intended to test on my Funcub, and install in an FMS Spitfire and Art-Tech T6 Texan. A few weeks later, winter came, I got a good bid for my Funcub, and the Version 2 stabilizers became available. Whilst the V1 is always active and sensitive to adjust, V2 can be switched on or off in the air and is less sensitive to adjust.

I quickly decided to mount a V2 in the vast accessible bay of the 1400mm FMS P51 to check the system.

Spring 1013 I took her in the air and assigned switch G (for Gyro) on my Specrtrum DX10t to enable the operation at altitude. I choose that knob because it was far enough from my other controls not to be actuated by accident, yet easily recognizable by feel for actuation with my left hand. I fly mode 2 so wanted my right hand on elevator and aileron during the switch, with my left hand on the G switch ready to disconnect the system in a fraction of a second if things got out of hand. System setup had been straightforward after reading the RC thread experiences of others, but final adjustments were more delicate as anticipated.

After trimming out the Mustang at a safe altitude and moderate straight and level pass, I switched the stabilization on but immediately saw the airplane fishtail vigorously. I must admit I had opened up the yaw pot slightly more as the pitch and roll, the idea being to be able to better control aircraft direction during takeoff and landing. Switching the system off, I landed (manually) and with the easy access to the pots I adjusted them on the runway. Second flight was much better, but as I increased speed I encountered aileron instability. It took me 4 flights to find a workable compromise on the 3 axis. Performing aerobatics with the system on I noted a drastic reduction of control effectiveness. The loopings are nice and big, because I cannot fly tight ones anymore and have insufficient authority to quickly pull out of a dive. Victory rolls also are nice and slow (as a real mustang) necessitating unloading the stick inverted (much more as before). The airplane became much more stable during scale type attack passes and reposition turns, especially in turbulent air, and takeoff and landings are much easier, yaw is now easier to control but not as rock stable as I had expected. I now have the system on most of the time, only switching it off when performing pure aerobatics.

The second V2 stabilizer was installed in my Dynham DC3. With battery and MrRCsound system filling the forward accessible cabin, I elected to mount the system next to the receiver on the top part of the wing center section (as close to the cg as possible not for weight but for angular movement detection). This meant I always would have to remove the wing from the fuselage for adjusting the pots.

Although I made the tailwheel steerable, the model is difficult to keep straight during takeoff. Prop wind tends to lift the tail from the ground at speeds the obscured rudder hasn’t reached effectiveness, no gyro installation is able to cope with that. Manual slow acceleration with full up elevator till rudder effectiveness, then slowly relax the back pressure till the tail becomes horizontal before liftoff still seems the only way to get it off the ground like a venerable airliner. Eliminating the horrendous 14 downthrust didn’t help takeoff nor landings, but at least the plane looks much better. Mixing some down elevator with engine power soon provided neutral behavior but that first had to be done with the stabilization off, the system otherwise would fight too much. I quickly got the pitch sensitivity right, but again find it difficult to adjust the roll sensitivity. Independent from speed, I sometimes notice a short wing waggle. Compared to the trouble I had controlling the airplane in final without the stabilization, it now comes gliding in as on rails. After touchdown, having the props still turn (to sync with the sound system) again makes it difficult to keep exactly straight. Flap application also is mixed with elevator and now the airplane seems steady and stable enough to tackle the modification towards retractable gear installation. More details about my DC3 on my dedicated blog page

With the experience I gained adjusting the V2 stabilizers, I installed and conservatively setup a V1 system in my Art-Tech T6. I carved out the back seat a bit more and was able to install the orange box flush just behind the pilot seat, next to the receiver but aft of the CG (ideal place already being occupied by the heavy sound system).

A piece of cardboard covers most of the assembly from sight, but allows wires to pass and pots to be adjusted along the sides.

Maybe that was the reason on the first flight just after liftoff I saw a dramatic pitch oscillation. In the air I kept the speed low and it disappeared, but after retracting the gear it came back occasionally, irrespective of speed. I was lucky to be able to land it reasonably well and after reducing the pitch pot, it flew an excellent second flight. Again the yaw excursions during takeoff or landing have not been completely eliminated but the model behaves at least twice better as without V1 stabilizer. More info about my Art Tech T6 can be found on my dedicated blog page

The following V1 found its place in the FMS Stearman. After cutting out some foam and making a flat spot as much forward as possible in the fuselage access, the system got installed so the 3 pots still were adjustable in the fuselage opening.

On this airplane I got it right from the first time. It seems adjusting the pots so the surfaces only move one third of the maximum deflection, provides sufficient capabilities to smoothen out the flying and turbulence, without making the airplanes too nervous or cause servo jitter. The Stearman is now a joy to fly. Having reduced the aileron throw when no stab was installed (to minimize tip stall and reproduce the scale roll rate) now reduces the roll rate even more, so take into account once the stab system is installed and fine-tuned, you better increase control throws again before making aerobatics. More details about my FMS Stearman can be found on my dedicated blog page

I now felt confident to install the system in my most difficult plane, the FMS Spitfire. After modifying the elevator system I got it to fly better, but it still was very prone to tip stall and very difficult to land on its narrow track undercarriage. Finding space to install the V1 system around the CG was easy and takeoff was much easier now.

Flying was a major improvement and I flew some stalls at altitude to get a feel for the speed and recovery. When I came in for landing, everybody agreed I was steady as a rock with sufficient power and speed, but about 3 feet from the ground it abruptly dropped a wing and hit the runway on the nosecone with 45 dive angle. Amazingly when I straightened it up, I could see no damage at all, not even prop or axle damage, only a bit of paint away from the nosecone. I was able to taxi in and further inspection revealed no further damage.
The morale of the story, flight stabilization systems will not prevent tip stalls, the contrary is true. Flying manually at slow speed I always would pick up a low wing by a generous application of opposite rudder. The stabilization system will not do that, it will lower the aileron on the low wing, causing that wing to stall instantaneously because the AOA rises sharply. I now know I will come in even faster with the Spitfire and fly it to the ground in 2-point attitude before reducing the speed, the stabilization system hopefully keeping the fuselage level during the ensuing rollout.
In the meantime I created a dedicated blog page entry for this modified FMS Spitfire, please get all the details about that unique model via the mainpage of this blog. Click on the picture to enlarge.

In 2015 I switched from Spectrum to Taranis/FrSky electronics and when checking that out on a model it showed to be fully compatible with the orange V1 and V2 glight stabilizers. Having "inherited" some V2 stabilizers from a friend who didn't trust them, I took the receiver swap as an excuse to update all of my stabilizer equiped aircraft (Spitfire, Stearman, T6 en DC3) to V2 standards, but also gave some of those airplanes a midlife update. All of them now fly much better and with the slider on the left side of the transmitter I can easily switch the stabilizer on and off (getting audio warning in the process) and now invariably takeoff with the stabilizer on, stick fully back and slow throttle opening till control surface effiectiveness starts, then slowly release back pressure to let the airplane get airborne by itself in a near 2-point attitude. In the air I mostly keep the stabilization on, but prefer to switch it off during aerobatics for better response. Landing is invariably with the stabilizer back on, and as soon as possible after landing in 2-point, I allow the tail to settle and then apply full back stick and avoid the nose to start groundloops.

After all those years neither V1 nor V2 ever caused problems or let me down, but it always took me 4 or 5 flights to find the correct pot settings. The trick is to start at about 1/3th open and during subsequent flights open the pots delicately untill the model starts to jidder at higher speeds, then reduce that pot a tad and everything should be fine in all regimes. Mind you, I fly all those models scale wise, people setting up these stabilizers for 3D aerobatics will probably use diffent approaches.
Last edited by BAF23; Nov 07, 2015 at 11:46 AM.
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