F-TEK 30A Fixed Wing Flight Stabilization Controller with Self-Leveling

UPDATE 7/13/2013:  After flying with the heading hold gyro mode, called “3D Control Mode,” for a while I am going to downgrade the F-TEK to a B overall.  I don’t like the frequent heading resets, others might like it fine.This gyro is best suited to people who will click it on for some maneuvers and off for (most) others.

Another issue is the mushy plastic of the gain control potentiometers, which degrade too quickly.

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I’ll soon be adding the F-TEK 30A to the list of Z8RC-tested Gyro systems.  This one is a little cooler, and more expensive at $93, as it combines 3-axis inertial accelerometer with a 3-axis gyro.  Three flight modes are programmable to any 3-position radio switch, knob or slider.  A 2-position switch can be used to select between Mode 1 or 3, or with mixing, two 2-position switches can be used to access all three modes.  The modes are:

  • Mode 1 turns the unit off
  • Mode 2 is called “3D Control Mode,” it acts like a 3-Axis gyro in tending to resist uncommanded aircraft movement, but adds inertial information that tends to hold the computer-assisted inputs until the plane returns to it’s last commanded attitude
  • Mode 3 is called “Emergency Recovery” and it attempts to level the wings while returning pitch attitude to a  saved, stored position whenever the controls are neutralized. The F-TEK memorizes a designated attitude, which is perfectly level by default, but user-assignable within a certain tolerance range

Essentially, the unit enables an “attitude hold” Auto-Pilot function, where the attitude is pre-selected.  There is also a GPS and barometric pressure enabled version (F-TEK 31AP) that allows automatic altitude control, programmable point-to-point autopilot navigation, and a return to starting point function for about $220.  Return to and orbit the starting point is automatic upon a lost signal

The F-TEK 30A is expensive, but not as expensive as a ring laser gryo.

The F-TEK 30A seems like an excellent choice for my STOVL F-35 project with the gear down, which switches the jet from Forward Flight Mode to VTO/VL/Hover Mode.  But “phase 1” will be to install it in a more benign situation for testing, and to assess the F-TEK 30A’s aerobatic impact and capability.
My phase 1 airplane is the new Sbach 342 1400mm project.  Phase 1 flight test is now complete.

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MANUFACTURER SPECS
• Working Voltage: 5~6V
• Stabilization: 3-axis gyro and 3-axis accelerometer
• Flight Mode: 3 selectable by transmitter
• Dimensions: 47x27x16mm
• Weight: 23g

FEATURES
• Easy installation
• 3-axis accelerometer and 3-axis gyro stabilization
• Self-leveling flight stabilization
• 3 flight modes selectable by transmitter
• Easy access gain adjustments for flight tuning

INCLUDES
• F-TEK 30A Flight Controller
• USB connection cable
• Required wire leads and mounting accessories

PRICE PAID
$93

UPGRADES
F-TEK 31AP includes GPS point to point navigation, barometric altitude hold, and return to starting point functions

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The F-TEK 30A package is more complete than most aircraft gyros.
The downside is the use of a simple wiring harness that could be difficult to replace, but could be hand made in a pinch.

Unlike traditional gyros which have a plastic case or attach an exposed Printed Circuit Board directly to the plane using double-sided mounting tape, the F-TEK 30A comes in a crash survivable all-metal black box that would walk away from any RC mishap.  The downside to its industrial build quality is weight.  An installed weighs a hefty .85 oz, (23g), compare to an 0.3 oz (8g) typical PCB-based gyro’s weight.  The heavy build limits the possibility of putting the 30A into smaller planes.
F-TEK’s 30A was surprisingly easy to install and set-up.  Unlike most gyros, and because there is a custom wiring harness that dictates the way the unit connects to your receiver, there is no way to reverse the input and output leads which can cause gyro damage.  The harness consists of a single plug breaking into color coded individual leads running from the F-TEK into the Rx.  There are five leads:  aileron, elevator, rudder, throttle (for powering the unit, actual control of the throttle is not implemented with the 30A), and a dedicated control channel lead presumably linked to a 3-position transmitter switch through channel 5 or higher.  The servos plug directly into the F-TEK’s “out” pins.  It is actually a little easier to hook up the F-TEK 30A than a traditional gyro, and better still, there is no hidden cost to buy the typically required male-to-male servo leads.
At this point, the F-TEK is fully functional.  Easy!
Once power is applied to the plane, the unit comes alive after about a one second initialization.  Although the manual states the unit was calibrated at the factory, my unit slowly commanded movement of all the flight control control surfaces to full deflection, even while the model was stationary.  Although the instructions do not specially not address this behavior, it does say that you might need to re-initialize the stationary state if there is a large change in ambient temperature.   I interpreted the slow movement as a lack of steady state calibration, so I decided to do the optional recalibration.
Recalibrating the unit consists of sliding the supplied jumper onto two pins, then powering on in a stationary state for at least 20 seconds.  During the stationary time, the red light flashed for about 10 seconds then the blue light came on solid.  I let the model sit for the remainder of the 20 seconds, then powered down and removed the jumper.  After that, the unit behaved perfectly.
The next thing to assess is the gain setting.  Like many 3-axis systems, the per-axis gains are set by turning a set of three potentiometers.  Reversing the direction of stabilization outputs, as required by your particular servo and pushrod orientation, is done with each potentiometer.  The center or 12 O’clock setting gives 0-gain, turning the potentiometer in one direction increases the gain to maximum, turning it in the other direction does the same but with reversed control output.
The gains come set to maximum, so count on lowering them significantly.  As you’ll see in my video, even though I substantially reduced the gains based on previous gyro experience, the model still oscillated along the roll axis at higher speeds.  I found that the 11 or 1 O’clock position was about right for my Sbach 342 installation, which has huge control surfaces and throws, or just one clock position of gain.
The last task is optional.  In Mode 3, “Emergency Recovery” mode, I discovered through brief experimentation, that the F-TEK 30A neutralized the elevator and ailerons when the attitude (not to be confused with altitude) was perfectly level (perpendicular to gravity).  Rudder is neutralized where ever the stick was last neutralized, then deflects automatically to return to that heading/attitude, like a heading hold function.  The obvious problem is that a model like the Sbach has a symmetrical airfoil which produces no lift at zero Angle of Attack, so the model would descend if the aircraft was automatically flown to the default attitude.  I decided to reprogram.
The procedure to program a new Emergency Recovery attitude consists of powering down, flipping a tiny dip switch (#4 to on), powering up with the unit in Mode 1 (off), manually flying the model to straight and level and then selecting Mode 3 (Emergency Recovery) for three seconds, then turning the 30A off by transmitter switch, landing and setting the dip switch back to off.  Done.  Pretty straight forward.
Being the enterprising type, I decided to do the above procedure on the ground.  I set the model on level ground and propped up the tail wheel to a pitch attitude about half way between level and the plane’s normal nose high taxi orientation.  Surprisingly, once checked in the air, that was not nose high enough to avoid losing altitude at a half throttle cruise.  So I recalibrated the way the manual prescribed for automatic return to exactly level flight.
Then, a light bulb went on, and I started scheming.  I thought, hey, I’ll program the Emergency Recovery attitude to establish and hold a perfect 90 degree nose high hover, instead of leveling the plane.  So I hung the plane from the spinner, let it stabilize, then attempted to capture the attitude.  Bzzzt.  The F-TEK wouldn’t accept such an obviously not-level recovery attitude.  Bummer.  Can’t we have a little fun here?
It didn’t take long to scheme some more.  I wondered if I could stand the unit on end in the plane, so the gyro case would actually be level when the plane is established in a hover, then I could reverse the rudder and aileron channels to provide the proper general flight control.  This has to be one of my better harebrained ideas, but I decided to iron out the “normal” installation first, then resume scheming.

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BLUF
The F-TEK 30A provides at least twice the stabilization of other 3-axis gyros—which isn’t always good.

Like all aircraft flight controls, the F-TEK takes some getting used to.  But where other gyros blend into the background most of the time, this gyro system is more prominent in 3D mode, and has an overwhelming presence in Emergency recovery mode, by design.  I’ll take it mode by mode, then provide a few video examples:

Mode 1:  OFF
There shouldn’t be much to say about turning the unit off, but there is, because unlike many gyros with an on/off function, this one actually works.  For starters the F-TEK provides a transmitter on/off switch, which many gyros do not.  This is invaluable because gyro stabilization has drawbacks as well as benefits, so the ability to quickly click the unit off can eliminate most of the drawbacks. 
Second, in off mode, the gyro is completely out of the control loop, not just gained down very low and/or causing servos to react slightly differently.  Off = gone.  Nice.

Mode 2:  3D Control Mode
As stated above, in this mode the F-TEK provides at least twice the stabilization as any of the other gyros I’ve tested.  This is great for maneuvers that tend to stabilize on a line, like inverted flight and Knife Edge.  It is not good for maneuvers that change direction, like simple turns or tumbles.  This is basically true of all gyros, so this balance of benefits and drawbacks is not unique to the F-TEK, only more pronounced because it is better at holding the aircraft steady.

For the times you want stabilization, the 30A is pretty amazing.  For example, the Sbach 342 serving as my test platform requires a dose of forward elevator pressure to maintain inverted flight.  With Mode 2 engaged, the plane requires very little push to stay arrow straight.  Most gyros have some impact on inverted flight or Knife Edge flight, but continuously succumb to gravity over time since they do not remember or strive to hold an initial attitude, they only resist uncommanded changes from the current condition. 

That probably sounds pretty cool, and it is, but there is an unintended consequence to this approach.  I am still getting used to the gyro, but it is easy to accidentally reset the last commanded attitude, which is a problem.  To illustrate what can happen, let’s say you are doing a Knife Edge 360 degree circle at 100 feet altitude.  Normally, you’d roll the wings to 90 degrees and blend the appropriate amount of rudder and throttle to maintain Knife Edge flight, then use elevator to create the circular flight path.  With the F-TEK engaged, as you roll some rudder is blended automatically to keep the nose up, so you don’t need as much rudder stick deflection to establish a platform.  Eventually, some combination of stick deflection and gyro-commanded rudder create the total steady state rudder input as the plane carves around the circle.  Now let’s say the plane starts to climb a little, so you relax your rudder input.  If you relax your portion of the rudder input to the point of hitting the neutral stick position, the gyro resets it’s goal of holding the last commanded position, so it releases it’s portion of the rudder input too, causing the nose to fall unexpectedly the instant the stick centers.

It is easy to demonstrate this problem.   Start a simple turn from level flight by banking the wings and blending a touch of elevator, leave the rudder neutral.  The plane wants to turn due to the bank and elevator, but the rudder gyro wants to maintain the initial course, so it starts to fight the turn causing the airplane to slip heavily around the turning flight path.  So far in this scenario, the rudder stick has not moved from center.  Now, let’s say you make a throttle input that unintentionally creates a tiny rudder stick signal, no matter how small, then the tail instantly snaps out of the induced slip and gets inline with the current heading.  This feels wrong in the air, because you did nothing that should affect a yaw change.

It’s hard to say if this is “a problem” inherent to F-TEK’s approach, or a drawback balanced by getting some pretty nifty new tools.  If you adopt the latter point of view, it follows that as you become more proficient with the gyro, you might click it on to exploit its advantages then click it off to avoid the pitfalls.

A related “issue” is the need to constantly “fly the tail around” during turns, helicopter style.  Like a heli, the airplane’s tail becomes very resistant to weathervaning, giving the appearance of strong adverse yaw.  This flight characteristic forces consistent use of the rudder, which isn’t all bad.

Hovering ease is improved, even a little more than a traditional gyro.

Overall, the level of stabilization offered by the F-TEK in Mode 2 is unmatched by other gyros I’ve tested.  That definitely comes at the expense of some extreme maneuverability (when turned on), but F-TEK Mode 2 did not limit maneuverability as much as traditional gyros I’ve tested.

Mode 3:  Emergency Recovery Mode
This mode is even more interesting than Mode 2.

If you only use Mode 3 to recover the plane from orientation woes, then it is undoubtedly a thing of goodness.  To use it, engage the transmitter switch and set the throttle to a cruise setting.  The plane instantly rolls upright and establishes the memorized level attitude.  It works great.

It is tempting to use Mode 3 as a basic training mode, since all you have to do is “let go” and the plane re-levels itself.  It’s a little like the good ‘ol F-16 autopilot trick, where some guys would set the autopilot to “altitude hold” before a dogfight, then hold the spring-loaded pinky paddle switch to temporarily disengage it while fighting.  If the Gs put you to sleep, your hand would fall off the stick and the spring loaded paddle switch would open, the autopilot would engage and attempt hold your current altitude.

Unfortunately, Mode 3 only allows 30 degrees of commanded bank while it is engaged, so maneuvering the plane is onerous and turn radii become very large.  The Instruction Manual  warns:

f) Warning:  The Auto Stabilization Mode will provide a smoother leveled landing for your aircraft. However, note that the turning radius is larger when in this mode. Please ensure your landing area has adequate clearance for this larger radius.

When I read that, I thought it was because the gyro inputs might counter a bit of your control inputs, and thus could be overcome by the pilot if desired.  But in fact, a ground test confirms that the F-TEK phases out any pilot commands after the plane hits 30 degrees of bank.  If the plane exceeds 30 degrees for some reason, the gyro issues proportional reverse aileron to command the plane back to a maximum of 30 degrees of bank.  If the aileron stick is released, the plane automatically returns to, and holds, level flight.  So it is impossible to turn tightly in Mode 3, no matter what you do with the sticks.

Mode 3’s behavior feels unnatural and is overbearing for basic flight training, but there is no doubt that it would be harder to crash if one fully understood the mode’s maneuverability limitations.  For those with no choice or a strong desire to self-teach, Mode 3 is an option to be considered.

I have not attempted to land in Mode 3 as of this writing.

Here are a few video comparisons with the test airplane in Mode 2.   These were the first few flights with the both the plane and the gyro, so I sucked a lot more than necessary.  In fact, the first landing is from the Maiden:

Takeoff
The Sbach’s tail wheel has an adjustable spring tension.  I left it way too loosey goosey for manual takeoff tracking, but the F-TEK tackled it with ease:

Turns
Note the desire to knife edge as the rudder resistance to yaw builds:

Tumbles
Extreme maneuverability is reduced, as expected, but the F-TEK’s impact is lighter and smoother than traditional gyros:

Landing
My flare combined with the F-TEK’s desire to hold attitude resulted in a big balloon, but the stability of the gyro still aided a reasonably smooth touchdown.  Consistent control during landing would be easily mastered with practice.  The landing roll is phenomenally straight considering my Sbachs very squirrelly tail wheel under (too) low spring tension:

 

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This is a hard grade, because the F-TEK 30A takes basic flight stabilization to another level, but it’s accelerometer-based approach brings a few logical quirks.  Technically/mechanically, the unit performed flawlessly.  If you take the time to learn explore the quirks in benign situations and understand the unit’s limitations, I think the the improved stabilization capabilities and Emergency Recovery Mode definitely outweigh the limitations and justify the price:  A+

Home Forums F-TEK 30A Fixed Wing Flight Stabilization Controller with Self-Leveling

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This topic contains -23 replies, has 5 voices, and was last updated by avatar z8rcdotcom 1 year, 5 months ago.

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  • #5648
    avatar
    z8rcdotcom
    Keymaster

    I’ll soon be adding the F-TEK 30A to the list of Z8RC-tested Gyro systems.  This one is a little cooler than the rest, as it includes a servo cha
    [See the full post at: F-TEK 30A Fixed Wing Flight Stabilization Controller with Self-Leveling]

    #5649
    avatar
    bunkx9
    Member

    I have an Eagle Tree Guardian 2D/3D stabilizer I have yet to install in anything yet. From what I’ve read, many users are having issues with setting it up correctly. Can wait to read your review on this one.

    #5650

    Doesn’t appear to have the auto-leveling or selectable flight modes, but Orange’s $25 V3 now has a 6-ch rx built, which is nice:

    http://www.hobbyking.com/hobbyking/store/__31586__OrangeRX_RX3S_3_Axis_Flight_Stabilizer_w_DSM2_Compatible_6CH_2_4Ghz_Receiver.html

    #5651
    avatar
    z8rcdotcom
    Keymaster

    I’m struggling with the value proposition on that one. To me, it mostly ruins the gyro to have to use it with a certain radio. Not to mention that it as one less flexible unit, it costs more than the Rx and the gyro purchased separately. I don’t get it.

    And isn’t it a little dicey to do that using the Spektrum standard that hardwires your channels? It isn’t always possible to mount the gyro/Rx in a traditional orientation.

    #5652

    Cleaner wiring and remote on/off switching are the advantages (over previous Orange gyros) I see.
    What do you mean that Spektrum “hardwires” channels?

    Negative for me is lack of a satellite port, which I’ll never fly any plane over ~750mm span without.

    Seems like it basically apes Horizon’s AS3X brick or whatever they call it, no? Except $25 instead of $50+.

    In any event ever since auguring in my beloved PZ T-28 thanks to Orange V1′s extremely slow roll I’m not in a rush to re-install it, or another gyro, in any of my planes. Wouldn’t mind a gyro on my Stinger EDF’s rudder channel but there isn’t room in the fuse to mount the V1.

    #5653
    avatar
    z8rcdotcom
    Keymaster

    What do you mean that Spektrum “hardwires” channels?

    In my Fokker Dr.1, there was no room for a gyro unless I mounted it standing on end, on the fuselage sidewall up in the nose. Even though it was OrangeRx (just to use up a near-free Rx to free a Hitec Rx for something bigger) that was no problem since you can run the gryo channels any way you want to, i.e use the aileron channel to stabilize the rudder, etc. But what happens when each channel is hardwired to a stick function and the Rx cannot be mounted so the gyro channel is in the right orientation to stabilize that channel? Is there a way to deal with that in the integral DSM Rx-gryos?

    With Hitec there is no labeled aileron/rud/elev channel, you assign each stick to a channel on the Tx, so ironically, it would not be a problem with an integral gyro that is mounted sideways.

    P.S. the DX6i/ORx dropped signal in the air at fairly close range and completely destroyed the Dr.1 after flying uncontrolled what seemed like ages. It wasn’t far away, so I doubt it was an ORx issue, but rather a brownout which Orx has been proven to less prone to. In short, a Spektrum DSM failure. I’m now only using Spektrum radios for BNF micros. I’ve lost count of how many planes I’ve lost to DSM/DSMX brownouts/drop outs. What an awful radio system.

    #5654

    I see your point with the combo gyro/RX and Spektrum. Unless you mount it in one specific way your controls would be mixed up.
    I’ve had one possible brownout situation in ~150 flights with Orange/DX8 (late 2012 model). Luckily didn’t result in a total loss just bashed up the Stinger’s nose a bit.
    The other day flying the WingWing (no satellite) it became unresponsive ~250 yds away. Thankfully she was in level flight at the time so I sprinted towards the plane with the TX held in the air, like we used to do with cheap RF RC planes :)
    Regained control after about 5 seconds and brought her home. Probably not a brownout, those take longer to re-bind don’t they?

    #5655
    avatar
    bunkx9
    Member

    I haven’t worried about brownouts flying my 50mm EDFs w/ ORx’s. But, I bought a Habu 2 which comes with a Spektrum AR600 Rx.. I haven’t flown it yet and am worried that a B.O. will be more likely to occu, especially with the Guardian installed in it. I’m thinking about replacing the Ar600 (a $60 Rx) with a $5 ORx 6 channel. That’s pretty sad to say…

    #5656
    avatar
    jamesgl
    Member

    By way of encouragement, I have five Eagle Tree Guardian flight stabilization units mounted in five different radio control aircraft, which I fly on a regular basis – weather permitting.

    They take just a little bit of getting used to, that’s true. But from the get go, they are reliable, and safe… In my experience.

    If you have ANY specific questions, I would be happy to try and answer them. I can only say by way of encouragement – that since I started using them, I have eliminated 99% + damage on landing for all of the models they are installed in.
    It is not unusual for me to experience several hundred trouble-free landings sequentially. I am not exaggerating.
    And I’m talking about multiple landings on days when it is quite gusty and windy.

    I’m not saying that I won’t have some kind of landing damage tomorrow or the next day, but it’s extremely rare for me to have any landing problems that result in ANY damage that requires ANY degree of repair.
    Sincerely,

    jamesgl

    #7329
    avatar
    airheli1201
    Member

    Have you ever considered multiwii as an alternative? It’s a lot cheaper $25, more flexible and expandable and already has accelerometer, 3 axis gyro PLUS barometer and magnetometer. Not to mention it’s smaller and lighter too.

    #7330
    avatar
    z8rcdotcom
    Keymaster

    Have you ever considered multiwii as an alternative? It’s a lot cheaper $25, more flexible and expandable and already has accelerometer, 3 axis gyro PLUS barometer and magnetometer. Not to mention it’s smaller and lighter too.

    I hadn’t heard of MultiWii until your post. It looks like a cool idea, but I couldn’t find airplane modes on the web info, only multirotor. I didn’t see the stand alone options you described either, but I probably didn’t spend enough time there. Looks like a fun option for an those who enjoy electronics tinkering, which I do. It definitely looks more flexible, as one could envision all sorts of interesting variations and innovations.

    For those who want a turnkey solution, HK also has a version with altitude hold and programmable GPS point-to-point navigation. Look for a flight test of that version on Z8RC soon:

    http://www.hobbyking.com/hobbyking/store/__24760__F_TEK_31AP_Fixed_Wing_Flight_Stabilization_Controller_w_Self_Leveling_.html

    #7386
    avatar
    airheli1201
    Member

    Have a look here.

    http://www.multiwii.com/wiki/index.php?title=Multicopter_Types#Airplane

    http://fotoflygarn.blogspot.fr/2012/03/how-to-setup-multiwii-airplane-same.html

    I was thinking that the level mode could be more stable to use on your vtol. Basically, in vtol mode, let go of your stick and have it level. You will need to position your multiwii board in the right direction to have it level horizontally with vtol. With only gyro based, it could drift, making it harder to control.
    You can get the multiwii on rctimers.com which I find it to be the cheapest online.

    #7388
    avatar
    airheli1201
    Member

    oh I didnt read properly. The F-TEK 30A does have accelerometer.

    #7491
    avatar
    bunkx9
    Member

    Z,

    I noticed in your Gyro post you note that any gyro that features a Heading Hold should never be used in an airplane, as it was designed for Heli’s only. Do you still believe this to be true? I ask this because my Eagle Tree Guardian has this feature and many people say HH is very beneficial, especially when used on 3D planes.

    • This reply was modified 1 year, 5 months ago by avatar bunkx9.
    #7501
    avatar
    z8rcdotcom
    Keymaster

    Maybe it is useful for 3D in with the right plane and the right expectations and practice.

    My reaction was visceral rejection, as the plane violently fought any kind of turn. The more aileron, the more cross control, which isn’t a stable configuration on most RC planes and dumped the nose hard toward the ground the first time I engaged it. If you are fully intending straight line flight, and resist the primal urge to fight the gyro and can manage to let the plane fly out of (your) control, I can see where it could be of some value.

    I think this falls into the category where younger, less experienced minds are a lot more flexible in what they can learn to accept.

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