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Author Topic: Flight Stabilizers  (Read 1781 times)

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Online Deerslayer

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Flight Stabilizers
« on: January 22, 2013, 11:33:20 AM »
They're here, they're there, they're everywhere!

I set up this Topic to discuss various projects and activities in this area.

Hey, Flypaper, tell us a bit about what you've been doing in this area. I am posting some of my adventure stories.
« Last Edit: September 14, 2017, 08:06:38 AM by Deerslayer »
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Online Deerslayer

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Re: Flight Stabilizers
« Reply #1 on: January 22, 2013, 11:59:13 AM »
Attached is a write-up I regarding my initial experimentation with the Eagle Tree Guardian.

I also have a set of operational notes which may eventually be added in here.

Please refer to the WORKSHOPS Topic, The Guardian Notes, for my latest notes on working with the Guardian
« Last Edit: March 17, 2013, 02:29:58 PM by Deerslayer »
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Online Deerslayer

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Re: Flight Stabilizers
« Reply #2 on: February 08, 2013, 10:25:57 AM »
I have a Workshop semi-prepared for the February Meeting. Note: I term this semi-prepared, as I cannot risk raising expectations.

This will cover flight stabilizers in general, the Eagle Tree Guardian specifically and my, and others, experiences with such stuff over the past few months here at our field. There will be hardware and demos, plus contributions from Dave Fasken (I hope).

I have some thoughts I would like to share with others on this topic, as such gear has many applications. From beginner through general port or scale flyer, to 3D, soaring, RPV or camera pilot. there is something about this stuff that could be useful to everyone.

I look forward to seeing you there.
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Offline fliegerfunker

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Re: Flight Stabilizers
« Reply #3 on: February 12, 2013, 12:25:33 AM »
Hey Gary,
I'm looking forward to this - I have nearly finished an Austrian triplane with tipperons - it might benefit from a flight stabilizer!

Martin

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Re: Flight Stabilizers
« Reply #4 on: February 19, 2013, 01:54:31 PM »
 As I mentioned to in the Workshop at the Club Meeting, Martin's  name came to mind regarding one of the many who could benefit from this technology.

 Let me be absolutely clear, this is NOT a criticism. Au contraire! Martin is the best designer and builder of complex and scale aircraft that I know, highly respected amongst his peers and any others who see his projects. He tackles some unusual projects, typically producing an exact scale model of something rather old that few have ever heard of! The fact that such a flying machine was probably a real "challenge" to fly back in its heyday meant there were often only 1 or a very few of its kind ever produced. Models normally will not fly better than their full scale counterparts, if they are created faithful to the original, and Martin tends not to cheat in his replications.

 So, here may be one of the best uses of stabilizer assistance. Wild and hair-raising, wing-swinging, porpoising take-offs plus an eventual white-knuckled flare and touchdown, combined with that final "bow" when the thing tumbles ass over teakettle - those are the kind of things that the stabilizer might just be able to tame or eliminate. (Oh, wait a minute, is that me and mine that I am thinking about? )

Long before the r/c pilot can recognize some of the excursions from a normal flight, the device may be able to detect and attempt to rectify the situation.

 I can think of one such machine in Martin's hangar that I am sure could be transformed. A Davis-something biplane? I hope that you give that a try, Martin. If I can help in any way, please let me know!
 
« Last Edit: February 20, 2013, 05:36:27 AM by Deerslayer »
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Re: Flight Stabilizers
« Reply #5 on: May 11, 2013, 08:38:37 AM »
Some of you may have seen me flying this Geewhizbee I got from Coy a while ago. As you may know I have a fetish for weird planes. ::) and had to beat this away from Coy. Well, I just grabbed it and ran like he##  :D Very difficult to fly with the short span and wide chord/low aspect ratio of about 2 to 1. Deep short fuselage doesn't help, but it is cute. Was ready to take the geat out of it but thought I would try a gyro in it. Made a completely different plane out of it!! A pleasure to fly now. ;D Enabled me to crank the throws up and moved the CG way back. A fun aerobatic plane now with a bit more tweaking to do yet. If you have that mean, unstable plane your ready to dump, give it a second chance with a HK reasonably priced gyro. They are basic but do the job well. If you need a hand to set one up, give me a holler. Be glad to help out, out at the field..

Online Deerslayer

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Flight testing utilizing Flight Stabilizers
« Reply #6 on: April 02, 2019, 08:38:59 AM »
A lot of air has moved across the wings since this Topic was first set up. Not much has shown up in here regarding ongoing experiences with stabilizers. So, I am bringing up some personal experiences with their use in initial flight testing and learning to fly aircraft that are new to me. Most of these are various flying objects of my own creation but some are ARFs that benefitted from that extra "set of hands" in the cockpit. Perhaps you have a difficult plane, such as a WW1 warbird, that is a pain to launch or handle under some conditions. A stab may help, even if you just use the Rudder portion, having turned down the Gains for the other controls, to enable a nice take-off roll. 

In my early days of using various stabilizers, I would first fly a plane with the stab turned OFF, having set it up to what I hoped would be OK. but not fully trusting it yet. Once the aircraft was airborne and reasonably trimmed, I would invoke the stab. Or, I would land, adjust the controls to achieve proper trim and do the next flight at least partially with the stab. A very cautious approach, one which I recommended to others who were trying out this new technology.

The down side to this approach, particularly with an unfamiliar, unusual or self-designed aircraft was that you had to assume/hope that the thing was flyable even though it may have had a poorly located C of G (a common issue with flying wing styles) or a mechanical issue such as a battery pack shifting during flight (this happened to me on a couple of occasions!). Here, we have this eager little helper but are reluctant to turn over partial control to it. Ironic.

Of recent times, I have changed my approach. Many of my flying objects, even the store-bought ones such as the Optera, F-27 Evolution and X-Vert, have integral stability systems as purchased. For the rest, I typically install a system, such as one of the Lemon receivers with integrated stab or else a receiver plus a downstream flight controller/stab such as the BGAOLE. And, I use them right from the initial launch. I have great confidence in such systems and have developed a couple of basic principles regarding their use.

1. Only use a system which can be activated/deactivated from the transmitter or, as with the AS3X, selectable between self-leveling and stability modes. The ability to adjust Gain from the transmitter is extremely helpful but only featured on a few of the current offerings.

 2. At home (not at the field):

 Set it up on the bench, without any distractions. Start out with the Gains set full so that corrective movements will be obvious. When you think you have the controls' directionality correct - stand behind the model, of course, as you wiggle it around in all axes - then try switching through whatever modes the system may provide. Turn down the Gains, perhaps to half way, such that the system is desensitized and therefore unlikely to induce oscillations, at least at lower than maximum airspeeds. If, for mechanical reasons, you have reduced the throws on any control surface via the transmitter, be aware that the typical stabilizer does no know that and may still attempt to use the full available throw, possibly resulting in binding and/or breakage. Keep your Servo Travel at 100% in the transmitter and adjust the control linkages to ensure that full movement will not cause interference with anything.
You can, and should, adjust your Gain appropriately after the initial flight(s).

3. At the field:

 Double check the behaviour of the stab system in each selectable mode. Think about one or more situations where you may wish/need to employ or disconnect the stabilizer and go through the motions. This builds a "memory item" with selecting the appropriate switch quickly when needed. If there is someone else available, enlist their help. Explain to them what you are doing, as they may be very interested. Athletes and professional stunt pilots call it "visualization". Explaining to someone else will reinforce that things are working as expected. I have been surprised on a couple of occasions when things actually did not behave as I was expecting while demonstrating to a friend. Embarrassing? No. More embarrassing would have been to plow a divot with my flying machine due to a simple configuration error! "But, I was sure I had that set up the other way...".

3. First flight(s):

If you have followed the above recommendations, there is no reason not to set up your machine in stabilization mode and begin the flight. Just in case something weird begins to happen, you should have your finger in place to disable the stab, but the odds are that it will be more of a help than a hindrance to achieving a good flight.

I currently have, and have had, a lot of flying wing type airplanes which require hand launching. This is where a stab really shines, as that first 1 or 2 seconds of the launch is "make or break" time. Typically, I will have the stab selected ON. If it has self-levelling capability, my more recent experiences have been to set it into self-levelling mode, although that is trickier - you really do have to be sure that "level" will not just keep the wings level but will keep a healthy Angle of Incidence at all times.

Aside: Remember, Angle of Incidence is NOT the same as Angle of Attack. The former relates to horizontal whereas the latter is related to the relative wind encountered by the wing. With my flying wings, I have the stabilizer set to achieve about 15 degrees Angle of Incidence of the wing, i.e., when the stabilizer thinks it is level, the aircraft has about 15 degrees Angle of Incidence. This should ensure that there will be sufficient Angle of Attack and therefore Lift to ensure level flight or a slight climb upon launch, even as the airspeed increases and therefore the Angle of Attack decreases. that same pitch angle yields a nice flat low speed flight, as well.

 If you are not comfortable with setting a stab into self-leveling mode right from the start, at least try it in the air right away. It could save your plane someday, if you remember to use it! I have on several occasions blinked, glanced away or such and momentarily lost situational awareness with a plane at a great distance out but flipping to self-level at least gave me some confidence as to what it might be doing.

 One caveat with self-leveling regards slow speed flight. Particularly with a sailplane or at least some flying wings (Optera being a great example, as I learned very quickly), there is a hazard. Sometimes, I fly slowly, perhaps relaxing in a thermal, in self-leveling mode; you still have partial control and can fly in large circles, yet the stab is smoothing out the bumps. If you are using a variometer, this will reduce the "stick thermals" and you will be responding to actual vertical air motion. But, you are flying close to stall. A sudden variation in movement of the airmass causes your ship to stall or drop one wing. The stab will try, persistently, to self-level by doing the exact opposite of what is required! Instead of neitralizing the controls, pushing the nose down and perhaps feeding aileron into the direction of the dropping wing, the stab will aggravate the situation into a fully-developed locked-in spin. You MUST immediately disengage the self-leveling, perform the normal stall/spin recovery. Although I often land in self-leveling mode, just for fun or in extreme wind conditions, you must keep the speed up on that turn to final and do base, else it's "earth meets plane" time.

 If you have a system such as Vector, BGAOLE or other that can so such things as Loiter or Return-To-Home (RHT), check out those functions on the first flight or no later than the second one. This will build confidence and may save your aircraft someday. (My Penguin FPV plane got lost one day, I screwed up and had not proven out the RTH function and it was only by great fortune that it got found and returned - undamaged! - a few hours later. Figuring out RTH had been "next" on my  to-do list after that "just one more" flight. Lesson learned!)


« Last Edit: April 05, 2019, 11:59:39 AM by Deerslayer »
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