Spektrum iX12 – 1 month in…

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One of my more recent additions to the RC hangar is not a new airplane but instead a new controller.  I have been using a DX18 for a few years and have found it to be an excellent radio.  I have zero complaints operationally with the 18 but I really like the newer designs that have come out without all the excess “chromed” plastic.  What’s the point in putting a coating over plastic that will eventually wrinkle/peal and otherwise just create issues?  It looks nice if you like chrome I suppose… never a big draw for me… and sometimes can create glare issues on especially sunny days.  Also, while not a big fan, there are times when a voice notification would be welcome.   I’ve held off because previously they were rigidly defined.  Want the radio to say “charge my battery!”?  Sorry, the only message available is “low battery”.

Spektrum’s approach of putting an Android tablet functionality “up front” in the iX12 sounded like it would have some nice advantages and I haven’t yet needed channel 13 and up on my DX18… so after a bit of research I took the plunge.  Hey, it’s a hobby!  If I’m going to get a little closer to the “bleeding” edge of technology in some facet of my life, this is the place to do it.  So after some time with the radio here is what I have observed and what I’ve done so far.

So far, I have had zero issues… I am somewhat familiar with Android so I think I have avoided some of the odd issues that folks on some of the forums have reported.  I moved 16 models over from my DX18 Gen 1 and everything has worked great so far.  I’ve flown a couple small quads plus 4 or 5 indoor airplanes and other than messing with the spoken prompts, I haven’t modified my setups at all.  Generally, I like the look and feel of the mechanicals of the transmitter.  If you’ve ever handled a DX9, you will find much of this radio to be very familiar.  Some parts of the box are even better, like the back sliders (which I rarely use) being much smoother.  The UI is not yet totally intuitive to me but I’m getting accustomed to it quickly.  I am beginning to like the text to speech options though I wish the audio defaulted to all OFF.  Will probably build myself a template for future use to accomplish this.

The radio is not capable of terribly loud audio levels and some have complained about that.  It certainly is not capable of the same volume of the DX9… Of course folks complained about distortion with the DX9 so Spektrum may not have been able to win this one!  Volume is not an issue for me as I intended from day one to use a blue tooth headset as I hate hearing the constant chatter of audio from other folks radios while I’m trying to fly.  I like to hear my aircraft (and others) and all that chatter is distracting and irritates me after a while.  I also think it impedes communication with my fellow pilots as needed for safety so I love the blue tooth headset option afforded by the Android interface. 

In order to make the audio usable, not annoy my fellow pilots and maintain safety I intend to use a single earpiece.  I bought the Sentry BT950 so I can use whichever ear I like… So far I like how it sits on my neck and audio seems plenty loud.  I have a couple other Bluetooth sets so I can try some others if need be but this one is a nice cheap option I can afford to leave in my flight case.

I also picked up an inexpensive blue tooth keyboard and mouse (Logitech model K380 and model M535, refurbished).  Both paired up and worked right off.  One oddity that was noted in some of the forums was apparent immediately.  When used in conjunction with the iX12, the enter key doesn’t function as you would expect.  So far the esc key seems to function in place of the enter key for text entry.  I’d bet there is an app that would remap the keys for me but I’m OK with using the esc key for this purpose.  The mouse works great and even has a “gesture” button that can be used to do swipes and such so you can pull up the various “side” menus etc… I’ve only used the mouse and keyboard a bit during setup of new aircraft but so far it seems like a great alternative to using the screen based keyboard to create all the text to speech prompts, timer call outs etc…  Do I need them to accomplish this?  No, but I like to have the option for anything that is going to require much typing.  I don’t even like to send long texts on my touch screen Android phone so having a keyboard is a nice option for me.   All my blue tooth hardware total cost me $70 and I will use some of it for other things so in my mind they are cheap at the price and nice to have options.

I routinely pull pictures directly from the web using the Chrome browser on the radio to use as my icons in the model selection screens and downloading the updates from google play is a nice and familiar way to operate so the ability to connect to a WiFi network directly from the radio is another nice to have option.  All in all, I like the radio so far.  There have been complaints about some issues (minor for me) like the audio level, slower model selection than other radios (30 seconds to change models versus maybe 5-10 on most radios) and the fact that it takes about 2.5 minutes to go from powered down to fully functional the first time you power up at the field.  This last is something you adapt to fairly quickly.  Just turn it on when you get to the flying site.  By the time you get a plane or two out, all is ready to go.  During the day, simply double tap the power button and go into sleep mode after each flight.  Coming back to full power up from there is a couple seconds.  The battery will last all day using this routine. 

As I worked with the radio a bit there were a couple of additions I decided were worthwhile.  First, there is a company (Powerhobby) who sells vinyl wraps for the face of many transmitters including the iX12.  I have occasionally dropped something onto the face of my transmitters in the past and I thought maybe this might give it a bit of extra protection.   Also a little individuality never hurts… I already know of one other guy in the club who has an iX12 on order so now there won’t be any mistaking mine for his!  Installation of the vinyl was a bit tedious but not terribly so and I think the result is pretty nice.  Here is what mine looks like after the application.

In addition I quickly noticed that the touch screen was going to often get greasy and spattered, etc… so I decided to take the leap and try to find a good screen protector.  I have not had great luck with the cheap plastic sheets you get for cell phones… they either mute the sensitivity of the screen, cause visibility issues, etc…  so I looked for a glass cover for this use and actually found one sold through Radiocontronics.  It is made of something marketed as “AirGlass” and is apparently from a company called Brotect.  I hesitated to spend ~$24 with shipping for what looks like a highly hyped piece of plastic cut to shape… but I have been pleasantly surprised.

Installation was pretty straight forward.  Clean with supplied lens cloth and carefully drop into place.  Done.  So far I have to say the screen is every bit as responsive as ever, there are zero bubbles or imperfections and so far it seems to pick up less dirt and finger “grease” than the screen itself did.  I wish it were just a millimeter or so bigger in both dimensions than it is… there is a very fine line around the screen that is visible if you know what to look for but is probably not noticeable to anyone else.  That aside though, I have to say it is working as advertised and if it keeps all those microfine scratches off my screen that my DX18 seemed to accumulate regularly (and it wasn’t even touchscreen) than I will be ecstatic.

At around the $600 mark, I think there is a lot to like in this radio.  And yes, I am a bit of a Spektrum fan for which I make no apologies.  I have worked with several other brands like Futaba, Hitec, Airtronics, Multiplex , Graupner and a couple others I can’t even recall.  All of them have some interesting features and strengths but it is hard to beat the Spektrum value for the dollar, excellent support and good balance of feature set with ease of programming.  The iX12 leans toward the more complex end of their line of radios so it may not be the ultimate answer for those who are not smartphone savvy or that are just happy with their DX7s or 9 or whatever but I think I’m going to enjoy it for quite some time.  At least until the iX12 Gen 2… or iX18 or whatever hits the market next! 

 

Graupner MZ-24 Radio — What???

My flying buddy Kelly, who I’m pretty sure considers me his personal “RC Aircraft Mechanic and Radio Setup Technician”… decided some time ago that he wanted to get a new radio system for his RC needs.  I know he has had good experiences with his Graupner charger and is a big fan of German engineering in general and so had high hopes when he ordered his new radio system.  He even talked to me first to insure that I was up for learning a new system and I said yes….

I have programmed many RC radio systems over the past 15 years or so. Airtronics RD6000, RD8000, Hitec Prism 7, Futaba 9CAP, Multiplex EVO 9, JR9303 and Spektrum DX8 and DX18 are all transmitters that I’ve spent time programming.  I’ve spent significant time and effort setting up multiple aircraft from trainers to multi-engines and delta wings to 3D aerobats on these radios and now I can add the Graupner MZ-24 to that list… or at least I’m trying!

Some random thoughts on my experience so far.

The MZ-24 is NOT a 24 channel radio.  For EVERY other radio in my list above you could probably correctly guess the number of channels by picking out the number in the radio name… but not the Graupner.  For some reason the number of channels you can control is 12… you can now decode that the MZ-18 is a 9 channel system, maybe?.  Kelly wasn’t fooled… he’s definitely a guy to research his purchases but I was fooled for a minute or two.

What Kelly thought was a German radio was apparently designed and built in South Korea?  Now that’s not a bad thing in my book… I’m pretty sure that more than half of the electronics in my home were designed and built there and I wouldn’t keep buying them if I didn’t think they were great products….but this radio…. maybe not my favorite effort from our friends in South Korea.

Setting up the flap system on this radio has been a multi-week odyssey which has ended in…. success… but only after completely abandoning the built in flap system functionality!  Apparently, setting up the flap system to do a simple 3 position flap setting with elevator mix is completely beyond my ability using this radio if I try to use the built in flap system.  Even after a few exchanges on the phone and via email with Graupner support I could not reliably make the flaps worked as I wished.  Setting the end points of the flap function is apparently impossible, and simple reversing of the function and strange things like changes in speed through the travel of the flaps are a couple of the  challenges I faced when trying to use the flap system.  Take my advice and just leave that function alone.  Just assign the channel, set the endpoints and sub-trim to establish the motion you want.  Slow the servo with the servo speed function and then build your own mix for elevator or whatever else you need.

Programming the telemetry system on this radio is… just odd.  While most other functions are configured in a somewhat intuitive method… when you get into the telemetry system you are confronted with screens of text that look like they are something from a 1970s computer application… i.e. from the days when computers didn’t yet have a mouse attached or a graphical interface.  Gone are all the pretty colors, graphs and symbols.  Absent are any understandable directions… at least for the simple voltage monitor we wanted to use.  Even the list of “alarms” are just labeled with numbers.  What each number represents is cataloged where?  Imagine how easy it could be to program a telemetry system if you a full touch screen color screen with audio prompts available…  Oh, that describes the Graupner radio!!  Unfortunately what we get is text only…  Did the graphical interface team all quit mid-project?

The range of receivers available, reasonable pricing as I recall and apparently solid build quality… even the various ports and options available… All would give the impression of a high quality, easy to use, good value, complete RC system.  To bad that it seems this product never got “finished”… or at least that is how it seems.

We are going to continue to work with this system and just see how it goes… at least until or unless we run into actual RF issues, which I don’t expect.  Here’s hoping Graupner does some more development and sorts out the oddities in the user interface.  The potential is certainly there.

For my part, I think I’ll stick with my Spektrum DX18.  I think both it and the DX9 are great radios that do about anything you’d want and who’s interface is far superior to the Graupner… even without a touch or color screen!

 

Throttle lock/Kill Switch programming on the DX8

A couple years ago I was taxiing back toward the pits with one of my smaller gas powered planes and had stopped to observer another flyer doing a nice touch and go… My plane was sitting by my feet at a sedate idle during this distraction.  When I turned back, I returned my left hand to my radio and inadvertently slid the throttle stick to full!!  Luckily I was pointed at the pit chain link fence 6 feet away with no other obstructions… like people… so as I grabbed the stick and returned the throttle to idle the plane made a dash for the fence and quit as a result of the impact and the prop breaking into several pieces.  It did no real harm to anything except the prop and my pride… but it woke me up and from then on I have been much more attentive to my models while they are running.  When I am idleing, my thumb is hooked across the top of the throttle stick so that it cannot easily be moved upward.  As well, I now have a kill switch on every fuel powered airplane and it is always in the same position on the radio so I don’t have to hunt for it!  With gas planes I have a mechanism hooked into the ignition circuit that kills power to the ignition.  Depending on the type of engine and ignition system it may work a bit differently but each disables the ignition which kills a gas motor immediately.

With the advent of more electrics in my fleet this became even more problematic.  Electrics, once the battery is connected, should be considered to be “running” in all cases and therefore treated with the respect that would be due any idling engine.  Since you can forget the battery is plugged in at times, I try to be especially careful to restrain my electric powered aircraft whenever I’m not holding on to them and a battery is installed.  I have also setup a throttle cut switch that limits the throttle channel output to zero or as close as possible.  In some radios this is simpler than others.  In my Spektrum DX-8 there are two ways to accomplish this… maybe more… but I’ll show one of them here that I use most.  (I believe the 7s, 9 and 18 all do it similarly)

Note: You can do all of the following without the plane even being present and certainly don’t want to play with this with the plane powered up!  I highly recommend you test after you finish however with the plane well restrained or the prop removed.

First, the DX-8 has a throttle cut option in the setup menu.  If you go into that menu and change the inhibit to a switch label (I tend to use Gear0 as I’ll show below) you get a screen that looks like this.

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You’ll notice that the switch is set to Gear0 (that’s a zero).  I use this setting as I tend to setup my radio so that starting point for all airplanes when I fuel up or attach a battery is with all switches pushed away from me.  It really doesn’t matter which way you do it.  I’ve worked with computers and electronics so long and the way I was taught logic you generally consider 0 to be off and 1 to be on…. I guess position 2 is “really on” in the case of a 3 position switch!

With my radio set this way the throttle is locked so it cannot inadvertently start up without moving both the throttle stick and moving the gear switch out of its starting “safe” position.  The other thing you may notice is that the position reads 30%.  I played with this and came upon this setting by trial and error.  I believe this has to be done because of two factors.  First, the designers created this for (I believe) primarily fuel powered aircraft where the stop/kill position is significantly different from the idle/standard starting position.  In an electric aircraft you generally don’t want an “idle” with the prop moving when you pull back to the lowest position on your stick.  You want a full stop.  Second, most speed controllers in my experience will look at the throttle setting on power up (as long as it’s at least somewhere near one end of travel or the other) to be the zero/stop point.  That’s fine until you combine with point 1.

So imagine you plug in the battery with the throttle 30% lower than “idle”… which is what the throttle position would be if you left that setting at zero and had the switch pushed forward/off when you plugged it in.  All seems fine… Your speed controller makes its little tunes and if you move the throttle stick nothing happens but your servos are energized (this may vary by manufacturer of the speed control).  Great, you are ready to taxi and you flip the switch to the armed/on position and immediately the prop spins to a “high idle” setting!!!  That’s not convenient, nor especially safe.  This is because with the kill switch in the forward/off position the throttle was at a point 30% or so below the idle point and when you plugged in the controller reset that to be “zero”.  By testing I have found 30% to be about the right point to avoid this issue.  Now the kill switch doesn’t really change the position of the throttle at all and acts more like a throttle hold then a cut.  Ideal for what we want when dealing with electrics.

There are other ways and other radios do it differently.  On my DX-18 which I fly more than anything else I use the F switch instead of gear because I use the gear for other things… like retractable gears!  But whichever switch you use, I suggest you keep it consistent.  This way your routine on each plane is the same at least as regards to a safe “startup” and also because occasionally you may want to hit it in a hurry and not having to think about which switch it is can make a big difference in response time.

I’ll try to post on a different method in the near future.  Hope this is helpful.  Fly safe!

 

ElectroDynamics Multi-Connex… The answer for the Carbon-Z T-28 and many others.

After a few trips to the field with my buddy Kelly and his new Carbon Z T-28 we quickly became aware that assembly was a bit painful because of the number of servo wires that must be connected when attaching the wing and the shortness of the wires supplied in the T-28.  The length of the wires can be easily fixed but just connecting the 6 wires correctly and reliably time after time seemed an unnecessary annoyance to get to what the Carbon-Z does great… fly!

Another club member pointed out some multi-pin connectors often used in jets and after some quick searches we located the ElectroDynamics OneClik Multi-Connex.  Made for 2,3,4 and 5 servos connections these seemed to fit the bill so we placed an order.  Very shortly (even though we chose the most economical shipping method) we had two of these packs on the bench.

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Here’s the interior of the T-28 before we applied the OneClik solution.

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and likewise here is the wing root before the installation.2015-09-25 10.33.54

Here is the wing root after just sorting out the wires and plugging them in (in alphabetical order just for ease of remembering!) to the new One-Clik wiring harness.

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Similarly the interior of the fuselage (with a little wire combing to really clean things up as well).

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I applied a bit of combing to the wing wires as well and then with only two connectors to feed through the bottom of the fuselage it is suddenly very easy to assemble the T-28!  A  bit of Velcro (just a 1/4″ square of so on the connector and a small strip on the sidewalls) makes a nice “keeper” for the new connectors and completes the transformation!

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Admittedly, it helps that the T28 uses all “Y” connectors so there is no right or wrong for left or right sides so you can’t connect it wrong but for those that don’t… at least you’d only have to label right and left!!

The product has a nice snug fit, a great positive click connection and appears to be of a very high quality.  The pricing seems very reasonable and my only regret is that I didn’t order some of these for my Mustang!  Oh well, even with shipping these seem to be a bargain.

Since installing these, we have made a couple trips to the field and unlike previous trips, the setup time is less and we have not had a miss-connect (pretty much impossible now).  In the past this was a tedious task which has occasionally resulted in having to pull the wing and find an errant wire.  I think that is likely in the past.

This system will likely become one of my go to upgrades for all future multi-servo wing aircraft.  The ease of use and added security of the connection is a huge plus in my opinion and I highly recommend you give these a shot especially in those larger and more complicated craft like warbirds and the like with flaps, lights, and etc…

Very odd failure of a Spektrum RC AR9000

My flying buddy Kelly has one of the Top Flite P-40 Giant Scale ARFs.  It’s a beautiful plane and if you are interested in this size and type of aircraft (50cc giant scale warbirds) I encourage you to check it out.  It is a well built and good flying aircraft that shows that the designer has learned from the earlier models in the line and made some important upgrades that make this airplane fly nicely but also hold up well to a few “imperfect” landings and hang together.

Last year, he came to the field and while assembling the plane as usual noticed something disconcerting.  After powering up the radio system with the plane fully assembled and ready for flight the flaps began jumping around in a random manor!!  After dis-assembly, some testing and no flight whatsoever that day… (sometimes you have to wonder why we do it) we determined that the flap channel (6) was always affected, regardless of which servo we plugged into it.  Off the receiver went to Spektrum for repair.  They did whatever it is they do and pronounced it good to go with no problem found.  They also “tossed” in at no charge a “software” upgrade while they had the receiver which was nice.

When we reinstalled, we did not see the issue again until… you guessed it, another day at the field and another day with no flying!!  Now, I don’t blame Spektrum for missing the issue with this receiver as they did not have one key bit of information.  What we discovered this time is that channel 6 only has an issue when channel 5 (landing gear) is at a particular extreme.  In this case, down.  I have further determined that it is the receiver and not the radio at fault as we removed the receiver and bound it to my DX-8 and saw the same issue.  Here it is with just the receiver under test, a 2S A123 as a power source and my DX-8.  I also show a meter to display the voltage to the receiver so there’s no question that the power supply is out of range.

Check out the video here: AR9000 Video

Apologies for the focus issues, but you’ll see that the servo attached to AUX1 remains perfectly still until I flip the gear channel and then the “twitching” begins.  I show this not to pick on Spektrum but to simply display a very strange failure mode I have never seen before and spark some thought processes that might save an airplane or two.  I

When you do your ground check, do you check with the various channels at full throw? With the gear up and down?  etc…  You may want to occasionally go through a “full throw” check if you can.  This may require someone holding the airplane or a stand if your setup involves retracts.  I think I am going to start doing an occasional control surface check with other surfaces at extremes.

I’m convinced that this would have meant a crashed P-40 if the problem had only shown up with gear up… i.e.  Nothing at all would have been wrong until the plane was airborne and he hit that switch to raise the gear.  Having the flaps randomly jumping back and forth in mid flight and with no clue as to why the plane started wildly pitching up and down would have likely been catastrophic.  It may be a very rare occurrence but you can be sure I am going to do the most thorough surface movement checks I can devise on all my aircraft in the near future.

I’ll add commentary to this post or perhaps do a “part 2” when I get this back to Spektrum and get their feedback.  For now the P-40 is ready to fly again with a different Spektrum receiver.

Blade Nano QX – Radio configuration

I’ve had the Nano for a few days now… maybe a dozen flights and I’m enjoying it very much.  Straight out of the box and with the radio configured per the instructions (Using my DX18) it is a nice flying aircraft.  However… there’s always room for improvement, right?

So here is what I’ve done to program my DX18 to help the little quad fly even better.  Here’s my list of “wants” that I came up with:

  • First of all, I wanted a throttle cut.  I consider throttle cut to be a necessary safety feature on any aircraft and on electrics especially.
  • Obviously I need a timer.  The flashing light on the Nano that signals a low battery has so far been unnoticeable for me.
  • Finally, I wanted to institute Expo and End Point adjustments in concert with the change from Stability mode and Agility mode.

With that in mind I started to do some programming on my DX18.  As I thought about what I needed, it hit me that what I really wanted was to use “flight modes”.  With the FM feature, a single switch or combination of switches can change multiple settings including end points, dual rates, expo settings and more.  I have never had a real need for FM, though in some cases it might be equivalent to or better than what I do now, but this seemed the perfect fit.  I wouldn’t want to enter the agility mode without also dropping my rates down and adding some expo and doing that all on one switch seemed ideal.  I knew there was some reason I bought this expensive radio!

The throttle cut function was easily added as was a timer… very standard and easy to do stuff.  But the next part got a bit more difficult.  The mode change (Stability or Agility) on the Nano is set to operate off of a temporary switch… in this case button “I” which is often used as the trainer switch on most radios.  I now wanted this to move to one of the 3 position toggles so that it would happen in concert with my flight mode changes.  It isn’t difficult to reassign this function (in this cast AUX1/channel 6) but when I did that I quickly realized that this was not going to work as intended.  I had thought I would have 3 flight modes.  FM1 would be stability mode with full throws and a little Expo (maybe 30%) thrown in to help me be smoother on the controls.  FM2 would be agile mode with moderate throws and a similar amount of Expo with FM3 being “crazy 3D guy” mode with full tilt throws and a much greater expo setting (maybe 70%) in order to keep things from being to touchy.  Not sure I’ll ever need that mode and maybe I’ll switch this around later to 2 Stability modes and only 1 Agile mode option but this is my desired starting point.  After adding in the “Quad” graphic the main screen shows the modes as seen here.

Here’s FM1 – Named Stability Mode

 

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And FM2 – Agility Mode I

 

 

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And finally FM3 – Agility Mode 2

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That all looks good but after moving the AUX1 channel to a three way toggle, a quick on-bench test immediately brought a problem to light.  The Nano wants to see a temporary Off-On-Off type of signal to change from Stability to Agile and vice versa.  Just going Off-On didn’t do anything until you came back to Off.  Imagine toggling the switch from 0 to 1 (no change in Stability mode but more throws) or moving on to 2 with lots of throw and expo but still in Stability mode… no big issue yet.  But, then going back to 0 and suddenly you’re in Agility mode but with full throws and low Expo… yikes!  For a bit I thought I was stuck… but then the DX18 came to the rescue.

The DX18 has something called a sequencer.  With the flip of single switch you can have a series of events occur.  In this case I setup the sequencer so that going from 0 to 1 (or 1 to 0) caused the Aux1 channel to move to full (step 1) and then back to start (step 2) with a delay of about a half second in each direction.  This sent the correct sequence of events just like hitting a temporary switch.  Moving from position 1 to 2 does not have an associated sequence as I’m already in Agile mode after I move from 0 to 1.  Nifty!  The only catch here is that you have to start with the switch in the correct position.  That’s not a big problem as I have a habit of having all switches pushed away from me when I power up my radio.  I found a way to help with that issue as well though.  More on that a bit later.

With that solved (it’s easy to test for this on the bench as the Nano changes its LED from blue to red when you enter Agility mode) I moved on to setting up my throws (End Points and Dual Rates) as well as my Expo settings for each mode.  With that all accomplished I did a quick trial flight and so far everything is working as planned.  Of course nothing is perfect and I started thinking that I really wanted to insure I powered up the radio in flight mode 1 and with the throttle cut engaged.

This got me to looking at another underutilized (at least by me) feature of my DX18 and that is the preflight checklist.  I immediately found this feature to be quite simple to use.  I have to say I sure wish I could edit the checklist descriptions, but I found two that are close enough that reading them will get me to thinking about these two important switch settings.  My Mode Switch is using a switch that I often use for flaps on other aircraft so the “Flap Position” checklist item works for that and the “Thro. Trim Position” gets me thinking about throttle enough to remind me to check the throttle cut switch.  Of course these check box items don’t actually check the position of those switches for you, but you can (and I did) set the radio so that it will not start sending RF until I check the boxes, and you have to do it before each flight (assuming you turned off the radio or went to another model memory in between).  At least it gives me one more chance to get it right before taking control of the Nano!  Here is the setup screen for that feature.

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And Here is what the preflight screen looks like on power up.

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Lastly another thought occurred and I went into the warning screen and made it so my radio would alarm if my throttle wasn’t at idle (or at least nearly so) and/or I wasn’t in FM1 when I start up the radio.  That’s even more foolproof than the checklist!  Here is the setting for that:

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I think this gets me “in the ballpark” as far as radio setup goes.  I’ll undoubtedly adjust my expo and dual rate settings but those are minor tweaks.  With this configuration I have checked off all of my wish list and gone a bit further on safety and initial start up settings.  So far after a couple more test flights after all this was configured I am well pleased.

 

Only 0ne more issue to tackle… that of visibility.  I have some ideas on that and I’ll post on that soon.  Happy hovering!

Did my Spektrum PowerSafe receiver just save my airplane?

Had a nice day flying at our Annual Toys for Tot’s charity fundraiser yesterday and today did the recharge on the flight packs on the plane I flew.  This particular plane has a pair of A123 2300mah batteries that plug directly into my Spektrum PowerSafe 9110 receiver.  This thing is a $200 item but it’s main feature is the ability to plug two batteries directly into the receiver via high current EC3 type connectors.  With this method the power supplied to the servos is shared between the packs and does not have to go through any switches.  A soft switch is used, which means if the switch fails the airplane is on and the current to run the servos does not pass through the switch so it is not a limiting factor in supplying power to the high torque digitals that are used on all flight surfaces of this aircraft.

When I went to recharge the batteries I started with the port side pack (just because) and charged them up to full… they took about 850mah.  That seemed high as I flew maybe 3 or 4 times and none were much over 7-8 minutes.  As I moved to the starboard pack something even more interesting occurred.  The charger said no battery was present!!  Double checking the leads quickly lead to the discovery that the negative lead ended in a nice solder ball that was no longer attached to the battery!  At some point it had become disconnected…  I don’t know if it was vibration, poor solder joints (from the manufacturer…  I didn’t have a hand in this connection) or some combination of the two.

I have no way to know if this happened before the flight or during but I can tell by the fact that the second battery took only 100mah or so to charge that I made several flights without it!  If the connection was dead before I took off the first time… then it really would have only meant I wouldn’t have flown that plane on that day if I hadn’t had this system.  If it broke at some point during the first flight it likely means my airplane is only here today due to having the redundancy in the system.  Glad I had this system.

Of course, this receiver is not the only way to get this level of redundancy and reliability.  There are other power distribution systems out there but for this size and type of airplane I think its a very nice option and one I will probably continue to deploy.  I will have to look at my pre-flight and assembly routine to see if there is a way I can check for this failure mode in the future.  In the meantime its nice to know its there protecting me and my airplane from disasters.

Updated throttle servo linkage on the P51

Spent a few minutes last night to make a few changes to the throttle linkage that caused me issues on the P51.  Here is the updated version.

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As you see I swapped arms to a fixed heavy duty Hitec arm as well as shortening the 2-56 rod and soldering on a coupler that takes me to a 2-56 threaded end.  Then put a clevis with jam nut and retaining clip on to minimize chances of another disconnect.  After getting the jam nut tight I coated it with a bit of clear finger nail polish to further eliminate any vibration induced loosening.  I then coated the threads on the screw going into the servo (which are all metal) to help on that side as well.  I could use some thread lock but need to make sure I can move it one more time when I adjust the throttle throws (if necessary) whenever I run it next.

I am open to suggestions but I think this will eliminate a re-occurrence of the issue that has me ordering a new wing!  At least I hope so.  The throttle end is held on with a 4-40 bolt through type ball link connector with a nylon insert nut so I don’t expect issues on that end.  I cleaned up any other issues under the cowl and will reassemble that tonight and then the Mustang will get parked safely in a corner of the shop until the wing gets rebuilt.  Probably will become a hangar queen for the winter and look forward to maiden day next year!

 

Mixing optical kill and Telemetry might be bad news…

I consider myself to be a fairly knowledgeable guy when it comes to electrical systems in RC airplanes.  Batteries, chargers and basic servo mechanisms and the like don’t frighten me.  I can solder a good joint, extend servo wires, create a voltage drop harness with a diode… no problem.  I don’t pretend to fully understand spread spectrum radios, short of an RF engineer no one really does but I feel I’m at least a fairly educated user and understand it well enough to cover the basics and have a fairly intuitive grasp on how to safely deploy the new technologies.

But, sometimes I push the envelope and try to make full use of multiple “new” technologies and bad things can occur.  Hey, if you don’t push the limits a little bit you will never learn anything new.  Add the reluctance of manufacturers to fully explain and publish information on how their technology works and occasionally we enter that part of the world that should be labeled “Here there be Dragons”.

Recently, a friend who relies on me to help him deploy the newer technology had a bad result with his Giant Scale P40.  We had setup the Spektrum telemetry system in his bird to provide (amongst other things) RPM readings.  We had done this by using a Y harness from the hall sensor on his DLE ignition.  In this same bird we had put in place one of the many brands of remote kill switches that is marketed as an optically isolated system but had used power from the same battery that powers his receiver.  In testing all seemed OK but we started to have issues with this configuration where the optical kill did NOT cause the airplane to shut down.  Back to the drawing board it appeared it might be possible the ignition was drawing power through this kill.  We swapped the kill to insure it was not failing and had the same result so we then tried eliminating the ground wire on that connection.  This seemed to help and we went merrily on.  We then went on to replace the engine on this bird to give it a bit more pull.  Shortly thereafter the plane started to die during flight and during one of these flights the dead stick did not go well and the plane was destroyed. While it is certainly possible it was something more basic like a bad servo extension etc… it seems as if this RPM sensor connection had some play in the crash.  The engine quit like a switch was being shut off, not like it was starving for air or fuel.  Plus test stand runs after with a much simpler electrical system worked flawlessly!

Eliminating the Telemetry on the test stand afterwards seemed to eliminate the problem and I can’t help but think it has something to do with this combination of Telemetry and ignition kill that caused the issue.  In the future, I think I will avoid using both and will either deploy a second battery for ignition, eliminating the optical kill or at least feeding it off a separate source entirely, or we will not deploy the RPM sensor (at least not by connecting via the hall sensor).

Please note I am not blaming either Spektrum or the kill switch manufacturer for the issue.  Using the halls sensor connection is not an approved method to make this happen… though some folks have made this work.  I will continue to pursue a better way to get RPMs working along with the use of an IBEC which is now my preferred method of running my ignition.  I have the magnetic sensor deployed on my DA 50 powered mustang and it doesn’t cause any issues but can also give erroneous high readings on occasion in mid flight so the search goes on for a better mouse trap!  I’d love to take advantage of the RCEXCEL RPM tap off of the ignition.  If anyone has ideas about how to make use of that to feed the Spektrum Telemetry I’d love to hear about it.  If I make progress on this, I will post and let you know.

In the meantime I’d discourage any use of the ignition hall sensor connection as a way to monitor RPMs, at least when you are running a single on board battery system and maybe just avoiding it all together is better.