File: 03guardian.ht1.doc
SPECIFICATIONS:
Function: 2D/3D Inertial Stabilizer
Dimensions: 40mm x 22mm x 10mm
Weight: 11 grams
Price: $74.99
Let’s face it, beginning pilots do not have a monopoly on sticky flying situations. We all get ourselves into trouble from time to time.
Maybe you flew in front of the low morning sun. Perhaps the wind whipped up after you launched your featherweight park flyer. Perchance you are finding out the hard way that your new aerobat is too hot for your thumbs.
Whatever the case, wouldn’t it be nice to have a safety net that would ensure that our models emerge from these situations unscathed?
Eagle Tree Systems’ new Guardian 2D/3D Inertial Stabilizer is such a safety net.
Stabilizers and auto-pilot devices have been around for several years, so the concept is not new. The Guardian is unique because it does not require external sensors. Everything is crammed into a box that has the look of a modern microreceiver. With such a small footprint and a weight of only 11 grams, the Guardian is a valid option for all but the smallest fixed-wing models.
Setup
Preparing the Guardian for flight is straightforward. After reading the instructions and watching videos on Eagle Tree’s website, I had no difficulty getting things squared away.
A cool feature of the Guardian is that it can be controlled via unused switches and knobs on your transmitter. So if you want to change stabilization modes (which I’ll explain later) or adjust the gain, you can do so on the fly. This was easy to do using the switch-assignment options on my Spektrum DX8 and Futaba 7C transmitters.
Aside from the mode selection and gain settings, the Guardian has a menu that allows you to activate or adjust numerous options. One way to navigate through this menu is with a series of stick movements on your transmitter. Eagle Tree also provides a USB interface and software so you can set up and fine-tune the settings via your PC.
In the Air
The Guardian has two basic stabilization modes: 2-D and 3-D. The 2-D mode maintains level flight, or returns it to such whenever that attitude is upset by outside forces (including your inputs).
Many aircraft possess enough positive stability to return to level flight. The Guardian’s active control surface corrections, however, are much faster at facilitating recovery than passive aerodynamic stability. That’s a handy feature when you don’t have much altitude to spare.
To evaluate the 2-D performance of the Guardian, I installed it in my Flyzone SkyFly Max a—four-channel park flyer, (which has been discontinued). The Guardian fit nicely in the fuselage bay beneath the wing. I attached the unit to the airframe with Velcro. I also taped it to hold it firmly in position.
I had no trouble integrating the Guardian with the onboard Spektrum AR6115 receiver. After adjusting the gain pots to make sure the controls reacted correctly (all explained in the manual), I was ready to try it out in the air.
I was glad to see evidence of a strong breeze when I arrived at the field. This gave me a chance to see how well the Guardian could compensate for less-than-ideal conditions. Initially, I flew a few circuits to remind myself how the SkyFly behaves without any stabilization. As expected, the wind noticeably affected the lightly-loaded model and necessitated corrective inputs to maintain a given course.
Enabling the Guardian in 2-D mode, with the master gain in a moderate setting, I could still horse around with the airplane and make it succumb to my will. Yet, as soon as I released the sticks (which activates the Guardian’s stabilization), the SkyFly Max immediately returned the airplane to straight and level flight. This behavior was true no matter what attitude the model was in when I relinquished control.
The recovery was faster at higher-gain settings. I also was more limited in my ability to put the airplane in awkward attitudes. Any attempt to perform a roll was halted by the Guardian well before the wings were vertical. My loop attempts were similarly squashed. I can see where this would be helpful to new pilots.
The SkyFly Max requires rudder input for a straight takeoff. With the heading-hold feature activated, the Guardian automatically handled this chore. For grins, I also explored the stabilizer’s 3-D mode in the SkyFly Max. Rather than maintain level flight as with 2-D, activating 3-D mode holds your current attitude.
I rolled the model to inverted and let go of the sticks. The SkyFly traversed the entire field in this manner without a bobble.
To further investigate the Guardian’s usefulness, I installed it in my Precision Aerobatics Addiction model. On another windy day, I again began with 2-D mode. With the gains turned up, the Addiction became tame—almost trainer-like. The Guardian prevented me from rolling or pitching too far from level flight. It also prevented the wind from having its way with the airplane. All I had to do was manage the throttle and make sure I occasionally turned the model to prevent a fly-away.
In 3-D mode, I repeatedly put the Addiction in a hover and released the sticks. I could see the control surfaces moving under the Guardian’s control and the airplane stayed as I left it. I altered altitude by jockeying the throttle. Although the wind carried it downrange, the Addiction stayed locked in nose-up. In fact, it only ended the hover when I told it to by moving the right stick. The story was the same with knife-edge flight and every other orientation I could dream up.
Once I had utilized the Guardian in two proven and well-refined airplanes, I decided to take a different approach using the Parallax, an asymmetric park flyer I recently designed. My canard-equipped prototype Parallax tends to wander in pitch at high speed (a problem that I corrected in later variants).
With the Guardian installed in the airworthy prototype, it halted pitch deviations before I could see that they had started. I made numerous high-speed passes on the same flight. With the Guardian turned off, I experienced un-commanded pitch changes nearly every time. I never saw the pitch anomalies after I activated the stabilizer in 2-D or 3-D mode. Apparently, the Guardian can compensate for poor piloting or poor designing!
Conclusion
In my tests with the Guardian, it performed as advertised in all instances. It is a neat, little device.
Before you call the use of a stabilizer cheating, consider all of the potential benefits. In addition to the uses I mentioned in the opening paragraph, the Guardian can broaden your acceptable weather conditions.
Maybe it will give you the courage to step into higher performance models. Perhaps it will give you an extra boost of confidence when you do a maiden flight with that scratch-built masterpiece. You may want to use it simply to impress you flying buddies with casual knee-high hovering.
Whatever the case, the Eagle Tree Guardian can help your models fly their best in all conditions and survive to fly another day.[dingbat]
—Terry Dunn
[email protected]
MANUFACTURER/DISTRIBUTOR:
Eagle Tree Systems
4957 Lakemont Blvd. SE, Suite C-4 PMB 235
Bellevue WA 98006
(425) 614-0450
www.eagletreesystems.com
