SPECIFICATIONS
Dimensions: 36 x 34 x 14mm
Supply voltage: 4 to 10 volts (2S LiPo-compliant; minimum 5.5 volt for Spektrum/JR satellites)
Maximum turn rate: 500/s on all axes
Switching servo rate (PC software): Can choose digital (220Hz) or analog (55Hz)
Servo power maximum: Total of 10 amps (permanent load 12 amps, short-term)
Weight: 18 grams (without cable wires)
PLUSES
• Easy to install.
• Simple to set up.
• Adjustable gain settings.
• Remote on/off switch.
• Free PC software and upgrades.
MINUSES
• None.
Until recently, gyros were only something you would typically find in model helicopters. Yet, as technology improved and components shrank, we began to see smaller gyro-stabilized airplanes populate the market.
Before the micro model aircraft boom, some people were already using gyros. They are popular with Scale models and turbines, to tame a nose wheel or calm a rudder, and people have experimented with aerobatic 3-D airplanes to see how the gyro helps or hinders their performance.
For multiple control surfaces, more than one gyro was required, which led to complex systems that are difficult to set up and tedious to tune. As model helicopters began to shed their flybars, three-axis gyro systems started taking over and became the new standard.
Meet bavarianDEMON (formerly HeliCommand). Bavarian Demon has a solid background in helicopter flybarless gyro design, and uses that experience for model airplanes. The company’s newest creation is the Cortex, which is a three-axis gyro designed specifically for airplanes, but can be used in nearly anything.
No bigger than a typical receiver, the Cortex is a single compact unit that sets in-line between your receiver and your servos. It is a rate gyro and heading-hold gyro, and can be remotely switched on and off. Bavarian Demon also provides free PC software via a download from its website, allowing you to customize all of these settings and update the Cortex with the latest firmware release.
The Cortex arrived in a small box that contained a basic instruction card, cables, a USB plug, and adhesive pads. I was installing the Cortex into a known, good setup that had already been flown, and it is recommended that before you begin installation you set up your airplane ahead of time to make sure that all the control surfaces are correctly responding.
Installation is straightforward. Out of the box, the gyro must be installed facing the front of the aircraft, but can be placed anywhere in the airplane. You don’t need PC software to set up the gyro. It can all be done without it, but this requires that the gyro be placed in the correct orientation. After you’ve downloaded the PC software, you can specify the gyro’s orientation.
The included adhesive pad with the Cortex is more than enough to hold the gyro in place, and no extra wire ties are required (or recommended). This method of mounting has been thoroughly tested throughout the years by the heli pilots, so it will stay in place.
I was mounting my Cortex in my wooden 50cc PAU Edge 540T, so to ensure a good bond I first glued in a small square piece of styrene for the adhesive mounting pad to stick to. I installed it fairly close to the receiver so that I could use the included wires to attach the Cortex to my receiver.
The Cortex has five channels available for gyro compensating. They are not labeled because it does not matter which channel you use for any given control surface. I had to ensure that whichever channel I plugged into my receiver matched the channel I plugged into the control surface. If I plugged channel A into what would normally be my rudder channel on the receiver, for example, then I would connect my rudder servo into the corresponding channel A on the Cortex.
Of the five available channels, I used two for each aileron servo, two for each elevator servo, and the last channel for the rudder. This gave me the full three axes of compensation with which to play: yaw, pitch, and roll. The gyro’s auxiliary channel was plugged into the receiver and assigned to a three-position switch on my Futaba 14SG transmitter. That was roughly the extent of the physical setup. It was simple and could be quickly finished.
Next was the gyro setup. If you use dual rates, make sure that they are set to the rate that gives you the maximum throw for setup. Then, you must teach the gyro throw extents, while simultaneously teaching it the correct directions. This is easily done without the aid of a PC, by following the simple LED signals on the gyro.
To begin the setup, I plugged a jumper into the first slot on the Cortex. I then powered up my transmitter and airplane and watched the LED on the Cortex. After it initialized (with my sticks in the neutral position), the Cortex flashed green twice, and I moved the aileron stick to the right and held it there. The gyro then switched to a single green flash, and I moved the aileron stick to the left and held it.
When the LED changed to the double green flash again, I returned the aileron to neutral and pushed the elevator stick up and held it, and then did the opposite when the green LED switched to a single blink. I repeated the same procedure for the rudder and the green LED came back on, signaling that setup was complete. I then powered down and removed the jumper. This concluded the teaching part of the setup. Now I had to program the auxiliary channel on my transmitter.
The channel that I had plugged the auxiliary cable into was assigned to a three-position switch, which included rate mode, off, and the heading-hold mode. The end points for that channel are used to set the gain for each of the two rates, and it is recommended to start low and gradually increase to the desired setting. After speaking with Bavarian Demon employees, I settled on starting with 30% for heading hold and 15% for rate mode.
At this point, the airplane should not be flown in heading-hold mode, only rate mode. Heading-hold mode is only for 3-D airplanes that hover or torque roll. When the airplane is popped into a hover, heading-hold mode can be activated and, when correctly set up, can hold the airplane in a stable hover. The rest of the flight should be done in rate mode to avoid any weird flight characteristics that can be caused by heading-hold mode.
With the airplane set up, I headed to the field to give it a try. When I power up the airplane, I must let everything set for roughly 6 seconds while the gyro initializes. This is indicated by a couple of twitches on all of the control surfaces plugged into the gyro.
The LED on the Cortex shows me which mode it is in. Orange means rate mode, red is off, and green indicates heading-hold mode. I took off with the gyro switched off, and when I was in straight-and-level flight I set the gyro to rate mode.
The first few flights were uneventful because my gains were slightly low, so I kept gradually increasing them to get the effect for which I was looking. If the gain is set too high, the airplane will oscillate in straight-and-level flight, so it’s a good visual indication that you need to dial back the gain. I ended up with my gains at 40% in rate/normal mode, and 65% in heading-hold mode.
When I was happy with the gain settings, I began to pay more attention to what the gyro was doing for the airplane. It was a windy day, and I can only compare the gyro’s effect with a switch that turns off the wind. The airplane tracked with no corrections from me, and there are definite stops in point-roll maneuvers without any effort from the pilot.
Harrier maneuvers are where the gyro shined. It removes most of the hard work and allows you to concentrate on flying the airplane. The overall flying experience was more enjoyable because it smoothed the airplane’s flight, no matter which maneuvers I was flying.
I attempted to hover in heading-hold mode, but I am too stuck in my ways and continued to fight the gyro when trying to hover. If I let go of the sticks, the airplane would practically remain in place, but I had a better experience hovering the airplane in normal/rate mode.
After the first couple of flights, I left the gyro on and quickly got accustomed to this new “super” airplane.
My Edge is already a great-flying airplane, and the gyro enhanced the flying experience. It is difficult to explain exactly what it does, so if you ever get the chance to try one, give it a shot. I think many people will like the way a correctly set up airplane flies with the Cortex.
With the available PC software, you can tweak individual banks, and set heading-hold or rate mode, and tweak the gain settings on each channel. This makes the Cortex flexible. Turbine pilots, for example, can have a high-speed and low-speed setting.
bavarianDEMON has simplified setting up a complex system, making it easy to achieve gyro stabilization in a short time. With such a small footprint, the Cortex can fit in nearly any aircraft, with many options for alternate setups when using more than five servos.
I think that it is a great system, and I know that we will soon see more setups such as this as the technology becomes more mainstream.
