Re-Programming the AR636a in the E-Flite Timber (Part II)

Part I of this post is here.

When I reconfigured my Spektrum AR636A and reloaded code to make it into (essentially) a standard AR636 receiver and used it as a non-AS3X model by setting all the gains to zero… all was well.  But when I then decided to add back in some AS3X functionality in certain flight modes I overlooked one important plot point.  Luckily while reading some forum posts on the subject of the Timber in general one comment about reversing the servo direction got me thinking.  So I ran up to the shop and checked and guess what?  My elevator and aileron were responding exactly the opposite of what I would want when I tested the AS3X reaction to uncommanded roll and pitch movements!!  This could have been disastrous had I flown in this mode.

Here’s the problem.  When I went back to what I’m calling “standard” receiver mode with no gains so no AS3X functionality at all, I decided to treat this just like every other receiver.  I relied on my transmitter to make all servo adjustments including centering, movement direction and speed, expo etc…. That’s great in standard mode.  The problem comes when I decided to re-institute a switchable AS3X mode.  With the servos all set to standard (not reversed) and the servos reversed as needed (Aileron and Elevator) in the transmitter the stick command work fine.  But, when the AS3X is on and sees an un-commanded pitch change it command the elevator in the opposite direction.  Unfortunately since it does not know the transmitter is acting in reverse it command what it thinks is the opposite direction from the pitch but (the way these servos are connected and linkage attached) is simply more of the same!!  This would result in a sudden increase in whatever uncommanded pitch occurred.  I’m guessing the plane would try to loop… continuously.  For the ailerons a constant roll would likely have occurred and in my case both would have happened and things might have gotten ugly from there.  Of course I could have overridden those command but as soon as I neutralized the sticks it would have just reoccurred and we would have been off to the races again.

Honestly my only shot to control the plane might have been if I could have reached the switch to shut off the AS3X function in time.  Since this likely would have occurred quickly after launch… I imagine there would have been some unscheduled contact with the earth and a lot of cursing and gnashing of teeth!

Lucky for me I have been reading a lot of posts and so this came to mind before an ugly incident forced me to learn the hard way!  So lessons… 

  1.  When working with the AS3X receivers, servo reversing is best done “on board”
  2. Make sure you have a known good working flight mode to use when changing these things.  Take off in that mode and test up high in the air so you have time to switch back to the known good mode if anything seems amiss.
  3. Don’t trust anything you read or are told if the person telling you has not flight tested his tweek/update or whatever!

OK, so quit wasting your time reading on line and go fly!!  ūüôā

 

Re-Programming the AR636a in the E-Flite Timber

Please read Part II (located here) when finished with this post… it has vital information if you are reprogramming as I did!

After a dozen or so flights on the Timber I started thinking it was time to either replace the receiver with a non-SAFE/AS3X model or find a way to disable the SAFE mode (which I will never use) and be able to at least switch off the AS3X mode.  There is a fair amount of contradictory information out there and apparently there is no reliable way to tell which AR636A can be adjusted and to what extent.  Some, you can adjust the rate gain and priority but not the heading (this seemed to be the case on the Timber) while others apparently are locked down.  It wasn’t clear to me if I could setup the receiver from the Timber to keep the safe switch selectable as well as have multiple AS3X settings or not…  

I did find one place saying you could “upgrade” the code on some of these receivers and basically bring the receiver back to standard AR636 functionality.  Of course there are all sorts of warning that you are on your own if something goes wrong.  Since I’ve got a new receiver sitting on the bench ready for install… I decided to take the shot.

So I went into the Spektrum web site and registered my AR636 so I could download the code.  When the site took the serial number successfully I was heartened that just maybe this would work.  After viewing a few videos about how to program the receiver I decided to just go forward with sending the code and see what happened.  The software recognized the 636 SAFE receiver and allowed me to download the code.  To do this using a PC you will need the USB cable.

Here’s a link in case you decide you need one of these.

I immediately went in and changed a few settings and quickly thereafter the SAFE mode was lost for good!  No big loss for me… would be nice to be able to reactivate that somehow just in case I wanted to sell this plane but it seems unlikely I would do that… it will likely crash or be cannibalized at some future point.  Hopefully thousands of flights from now.

I now have all the settings set to zero gain for all three (switch selectable) modes… as well as taking away a couple servo reversing settings.   So I have effectively converted the the 636a to a dumb standard receiver!  Well actually it seems to be equivalent to a 636 now with expo, channel assignment and reversing and all the “gyro” settings available.  I can see where this would be really nice for someone with an inexpensive radio that didn’t have all the expo, assignment etc… already available.  For now I’ll just use it as a standard receiver and be happy with that.  Looking forward to flying the Timber without the stabilization to see how it goes.  Will be nice to see what the air frame and my skills can do without any help from the receiver.

Eventually I may re-institute some of the stabilization settings on a switch in case I want to do some “poor condition” flying and need a safety net or perhaps if some other folks want to get a flight or two in on a stabilized aircraft.  I kept an export of the original settings so hopefully, I can go back and re-import the original settings if I want to.

Looking forward to getting a flight or two on it soon to test it out.

Extreme Flight Laser 200 – First flights and Telemetry reports from the speed controller

Saturday was my first 2 flights on the new Extreme Flight Laser 200.  It’s not even quite “finished” but I deemed if safe to fly and took it out for the clubs “Electric Only Fly”.

All I can say is WOW!  The plane flew very well with perhaps 2 clicks of aileron trim and nothing else…  I need to experiment with balance as I think I had the batteries a bit to far forward as the nose wanted to fall  during inverted flight or inverted 45 degree up lines… but otherwise the Laser drew a line just like it’s namesake.  It also flew light while still handling a bit of wind without issues. The smooth power from the 35cc Xpwr/Castle 120HV and 12S 4500 45C Pulse battery setup was awesome to behold.  Using a Xoar 20×10 for these first flights and the prop noise is minimal.  I love being able to hear that and the air over the air frame instead of the din of a gas motor.

The 4500mah Pulse batteries seem to be able to give me about 7 minutes of mixed IMAC style flying and time to land with 35% or so of capacity left over… which is sufficient though I might wish for a tad more flight time.  I’m thinking of moving to 5000s as the plane only weighs 11lbs 4oz +/- so I think an extra 4-6oz of battery pack wouldn’t make a big difference.

A new item of note that I am running in this bird is the Castle Creations Telemetry Link for Xbus.  Here’s a link if you have to have one after reading this:

This nifty gadget feeds back information like the current draw, voltage, watts, RPM and FET temperature based on information directly from the speed controller.  Getting all this information from a standard Spektrum telemetry setup required a lot more work and several sensors that cost a lot more than this module.  Based on the information it provided I was able to get pretty graphs like this out of my telemetry viewing program on my PC:

Some interesting information can be had by examining this data closely… for instance at on peak point during the flight, the motor was pulling around 86 Amps!  This was at a point just a minute or two before landing and this caused the battery to sag to about 40.5 Volts.  At this point the prop was turning slightly above 11,300 rpm!  At another point after some sustained mid-throttle flight, the FET on the speed controller reached 145 degrees Fahrenheit.  The reported max power was just over 3600 watts!  For this light an aircraft that is almost insane… which is fine with me!  I’m not in full throttle very often and certainly won’t need to be with this bird.  To quote an old friend “To much power is almost enough.”

The FET temp reading tells me that the 20×10 Xoar is not over stressing the electrical system when flown in this manner though the RPMs seem a bit high so perhaps the 21×10 or 22×8 that I have may be more suitable.  It will be fascinating to run those and get some comparison data.  This kind of data is priceless when you consider it is going to allow me to choose a propeller that maximizes speed or torque or battery life as I see fit and to insure that I’m keeping the power system in a “happy place” while doing so.  Not having to worry about the health of that system is going to keep money in my pocket (not buying more components to replace the burnt out ones!) and give me one less thing to be concerned about.  That makes me happy.

I will update some more and do some comparisons as I try out more/different prop choices.  I’m really hoping the 22×8 works well as I’m thinking that it will give me more low end pull and less speed overall (which is fine with me) while giving me a bit more down line braking effect…  time will tell.

So far, I’m loving the information this little module provides.

I’m also using the arming lockout key from Castle.  This little gadget signals the speed controller to enter the lockout state whenever the key is inserted into the socket.  It’s another layer of security for the very powerful motor and attached prop.  Between this and the throttle cut I have programmed into my transmitter, I feel much more safe plugging in the two 6S packs!  This system is nearing the 5HP level and spinning a 20 inch prop at 11000 plus RPM.  What that can do to unprotected hands, arms, legs, etc… is worth considering.  An extra measure of safety is always welcome.

 

Aeroworks BD-5B – final touches and photos

Did some final work on the BD-5B this evening. ¬†Here are a couple photos… still pre-flight.

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You can see the Pitot tube (which I love on this plane) along with some of the decals in this shot.

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The rear end of this plane has some bite! ¬†That spinner (stock) is nice looking and the APC 7x6E looks great and certainly seems to produce some push… at least sitting on the bench.

2016-02-10 20.25.55-smallThis view shows the interior which is admittedly cramped and messy with all the goodies stuffed in the right places to make the balance come out as specified. ¬†You can see the 2200mah 3S LiPo on the right (tucked into the nose). ¬†The tubes coming out from underneath it are going to the pitot which feeds pressure to the airspeed sensor which is tucked in the back (left/upper in the picture) part of the area under the canopy. ¬†Hidden under the wires in that same area is the Variometer as well. ¬† The Castle speed controller is velcro’d on to the sidewall at the bottom center. ¬†At the bottom left of the photo just behind and below the speed controller is the telemetry receiver with the g force sensor attached to it. ¬†Just in front of the servos, just peaking out from under the servo tray is the Spektrum receiver.

This may be a bit of over instrumentation for this little bird but once I see the data I can always pull some or all of it out… except the pitot/airspeed as it just looks to good to lose it! ¬†Hurry up spring… I need to get a few flights on this bird. ¬†ūüôā

 

Updates… Carbon Cub motor, AR9000 repair

In an earlier post I related my misfortune with my Carbon Cub motor having failed. ¬†Another covered the issue of channel cross interference in a Spektrum receiver. ¬†Well I’m happy to report that both issues are now resolved.

The Carbon Cub motor was replaced with no charge by Horizon Hobby.  In fact it came back in something like 4 days which allowed me to get a test flight in at the club field before slapping the floats on and making a trip back down to Lake Lemon near Bloomington, IN for the fall float fly.  Once again the Cub performed great.

I would still recommend the Carbon Cub, but I would certainly advise keeping a close eye on the BL52 motor from E-flite.  I love the Power 60 on my Extra 260 but this motor is not that same quality in my opinion.

On the receiver, once again Horizon finally came through, and not only replaced but upgraded me to a new AR9020 DSMX receiver. ¬†I was a tad disappointed the tech still couldn’t recreate the issue after I sent them a video and exact transmitter settings that allowed me to recreate the issue using both my Spectrum radios! ¬†The important thing I suppose is they did right by the customer and that seems to be the way they tend to ¬†operate which is not always the case with all businesses. ¬†Kudos to Horizon on that front.

It’s getting to be late in the flying season here so expect to see some building projects, indoor/micro electrics and similar discussion soon.

 

 

 

Battery Energy Sensor…

I recently got my hands on what seemed to be one of the first batch of the new Spektrum SPMA9605… known as the Flight Pack Battery Energy Sensor. ¬†Where the earlier options had been a current sensor and a voltage sensing lead, the new sensor promised to not only read instantaneous current, but to keep accumulated current draw and pack temperature as well.

I installed it into my AeroWorks Extra 260 (60-90 size) powered by a Power 60 E-Flite motor by the expedient method of simply plugging in the two EC-3s and the xbus connector from the earlier installed current sensor. ¬†Upon testing I was dismayed to find I could see no option to display the new information… ¬†Only after fussing with it at the field for 30 minutes or so did I recall that I had declined to upgrade the software in my DX-18 months before, seeing no need for any of the fixes that centered mostly on helis and sail planes. ¬†I especially did not want to rebind all of my aircraft since every previous version had required that. ¬†The latest versions promise that it might not be necessary but I had not been interested in testing that assertion.

A couple days later (tonight in fact) I downloaded the latest version and after backing up the DX-18s memories… placed the updated file on the memory card and hit the proper keys… ¬†After a couple of minutes the radio finished the process and miraculously upon power up, I had full control of the little Extra!

Even better, I now had the option to include the battery pack sensor in my display and set thresholds and alarms.  I set up appropriate levels and tested the current readings and all looked promising.  Since my built in temperature sensor was already in use monitoring the motor, I wanted to take advantage of the temperature capability of the new sensor.

Now, I became confused as the port labeled temperature on the side of the sensor was clearly 4 pins and the only temperature probe I had available was clearly a three wire connector… and actually only used two of them! ¬†I chatted with a supposed expert¬†on the Horizon web site and they had not physically seen the sensor and could not help, nor did the documentation that came with the unit so much as mention the temperature port.

I had nearly given up hope of finding an answer when I finally noticed the top label of the sensor was (at least apparently) applied upside down… ¬†Where the label says X-Bus 1 and X-Bus 2 there is but one port and it is 3 pins…. X-Bus is a 4 pin connection. ¬†On the opposite side is a label Temp and on that side are dual¬†4 pin ports… ¬†Clearly these are the two X-Bus ports and the one 3 pin is the temp sensor!! ¬†I had already plugged in the single X-Bus port into one of the two ports on the side labeled temp it could only fit on that side. ¬†I went to look at pictures and realized that all must be this way! ¬†Someone should tell the folks on the assembly line… ūüôā

Here is a picture showing the labeling and the correct wiring.

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Turning in the radio after this revelation shows the following…

2015-09-09 21.06.20I now look forward to actually flying and testing the capacity measurement capability and am excited that I will no longer endanger my batteries by over discharging them.  The closest I could do before was to set a low voltage limit which often meant I would get a warning that would sound at anywhere from 5-35% of capacity remaining depending on throttle setting at the time.  I have great hopes that with this new capability I can set the alarm for a calculated 80% of battery capacity used and expect a much more accurate accounting.

I will post more as I get time to fly and test this capability.

Carbon Z Cub – Flight times, batteries, Telemetry and more.

The Carbon Z Cub flew on 3 different battery packs on New Year’s day and considering the temperature (15F or so) and the winds (~15MPH and largely across the runway) it flew quite well.¬† Flying with a stock setup with the exception of the Dubro 6″ inflatable tires, the recommended 3200mah 30C E-Flite 6S pack kept the cub up for somewhere between 10-13 minutes.¬† This flight was a fair mix of smooth and easy flying mixed with loops, rolls, stall turns, etc…¬† Especially considering the temperature, I was quite happy with the flight time.¬† Testing back in the shop showed all cells at between 3.70 and 3.74V and a recharge required 3006ma before the charger shut off and the cells stabilized at 4.17-4.18V per cell.¬† I did not even fly to the point of voltage cut-off but I imagine I was very close!

The second battery is a GForce 40C 3700mah 6S.¬† I flew approximately 10 minutes and later testing showed the cells at ~3.8V per cell.¬† Recharge took 2863ma to bring the battery up to 4.19-4.20v per cell.¬† Again, I did not fly ’till cutoff and it appears I had another 2 or 3 minutes of flight time available at a minimum.

The Dubro wheels, which add 3/4 of a pound of weight to the aircraft, may have had a minor effect on the climb rate of the Carbon Z but it was still able to climb straight up for at least a couple hundred feet and then hold a hover, though pulling up out of the hover is only possible early in the pack.  I am very happy with this level of performance.

The other effect of the additional weight is a shift in the balance since the wheels are well forward.  Using the Mills battery tray, it is fairly easy to push the batteries way back and keep the balance only slightly ahead of the recommended.

The cub was quite manageable in the 15 MPH crosswind… keep in mind I do NOT have an AS3X receiver in my aircraft… though I would prefer not to be flying in any stronger crosswinds!

I did get a TM1000 Telemetry receiver installed before the flight so I have records showing the receiver voltage and battery temperature for the flights.¬† Since the batteries were kept warm before hand they mostly started around 50-55 degrees and showed a slight temp increase toward the end of the flights… only a few degrees overall.¬† Likewise the receiver voltage was pretty stable.¬† Staying between ~4.8-5V for the entirety of the flights.

I have some plans to add a high current sensor as well as possibly a voltage sensor on the main battery connection and altimeter.¬† I may also move the temperature sensor to the speed controller…

Also, I got in a very short flight with a borrowed 5 cell pack.¬† What I failed to take into account is that the E-Flite speed control is set (by default) to use 6S packs!¬† This led to some anxious moments when shortly after takeoff, the pulsing of the motor that signals the battery is low was clearly heard!¬† This quickly reminded me of the default setting… which I had meant to override.¬† A bit of careful throttle management got the cub back around and on the ground safely.¬† If you intend to fly anything aside from 6S packs, I highly recommend you reset the speed control to the “automatic/70%” setting so it will warn you of a low voltage only at the appropriate time based on the original voltage seen at power up.

Be warned that if you elect to utilize this setting, you should insure that a fresh pack is installed at each power up as anything else may fool the controller into setting its cutoff voltage to something that could easily be low enough to damage the pack if you actually reach the “pulsing” warning level.

Finally, of course I came back with more paint loss around the front battery hatch <sigh>.¬† I intend to make some further efforts to help limit this problem but I want to get some “personalization” done first so for now it looks like just continuing to touch up after every flying session will be the rule.

 

Spektrum Telemetry and Spektrum Telemetry Viewer (STV) – Part 2

The next display I’ll show you from my air show flight combines the speed recorded by the GPS and the speed recorded by the airspeed sensor (Pitot tube/pressure).¬† This is interesting for a couple reasons.¬† First, you would expect to be able to see the difference in ground speed measured by the GPS (at least when flying level??) versus the airspeed measured the airspeed sensor.¬† Here’s what it looks like.

CustomSpeed

 

According to this my top ground speed (GPS.. in purple) was about 98.5 mph while the airspeed sensor shows a top speed of about 97 mph (in red).¬† Trying to compare at any single point doesn’t appear to work very well as the discrepancy between the two sometimes makes no sense.¬† It appears from looking at the numeric data that the sensors disagree on the time stamp associated with the sample so correlation is difficult.¬† This is interesting data and will be very interesting to correlate with a flight after I get retracts installed to see how much the lessened drag changes things.

Next we can look at the G sensor output.  This shows X, Y and Z axis which is Nose to Tail, Wing to wing and top to bottom respectively.

XYZ

The most interesting thing seen here is the maximum G force (Z Axis in gray) is nearly 4.25!¬† Using that handy custom graph again and you can correlate a climbing altitude a few seconds before then bottoming out a few seconds before this reading, along with increasing speed on the same basic curve…¬† This would likely indicate I was performing a loop and this high G was just past the bottom of the loop as I pulled back up to gain altitude.¬† Imagine the wing of the airplane combined with the engine thrust having to create 4.25*21lbs = ~90lbs of lift to arrest the dive and bring the plane back to a zero sink rate. ¬† Maybe a little larger loop and less throttle on the down side would be a good idea!¬† I guess the glue joints and main wing spar are holding up.

For a final look at what we can see using STV and the data supplied by the Spektrum products I will do one more post soon showing the GPS data and logging information soon.

 

Spektrum Telemetry and Spektrum Telemetry Viewer (STV) – Part 1

I have been working with some software from ROBO software called Spektrum Telemetry Viewer.¬† STV as I’ll call it allows you to do several things based on the .tlm file that a Spektrum radio saves to the SD card when appropriately configured.¬† Look for a link to them soon on my links page.¬† Spoiler alert, I like the product and think it really makes the telemetry information gathered by the Spektrum TM1000 into something even more useful than what the radio can do on its own!

Using STV you can really dig in a bit more to the telemetry data that you have collected during flight.¬† I love knowing what my battery voltage was at the high and low point in the flight, how fast, how high etc…¬† Much of it is very cool and parts of it are excellent in determining just how well your radio link is being maintained, if your on board batteries are performing as expected and even some things related to engine performance!

As an example lets look at some data I gathered from my P51 during a demo flight at our recent air show.¬† For reference, the P51 is running a DA-50 with a Xoar WWII style 22×10 prop.¬† The ignition is fed through an Ultra IBEC which includes voltage regulation and is powered off of the same flight packs which power the rest of the aircraft.¬† Those batteries are a pair of 2 cell A123 2300mah packs.¬† These feed the Spektrum power safe 12 channel receiver.¬† There are 9 servos plus and electronic ignition cutoff switch in the bird.¬† All servos are Hitec brand, ranging from 5625/45 digitals, 645 analogs and a couple of standard 425s if memory serves.¬† This is the giant scale Top Flite P51 and it weighs in around 21lbs.

For Telemetry I have the TM1000 which plugs directly into the data port on the receiver to receive flight log information as well as power.¬† I have the head temp probe positioned a couple fins below the top of the head toward the back of the cylinder.¬† The RPM probe is the magnetic type and it is glued into a wood stick and positioned to sense the magnet embedded in the hub that also “fires” the hall sensor.¬† I also have the GPS module installed as well as the 3 axis 8G force sensor, the altimeter unit and air speed sensor.¬† I have the voltage probe wired into the ignition side of the IBEC so I can monitor ignition voltage as well.¬† Having covered all that lets look at some data.

This first graph is the RPM/Volts/Temp page: RPMVoltsTemp

First take a look at the blue line.¬† That is the temperature line.¬† Looking at some of the other data I can tell you that throttle up to takeoff was around 90 seconds into this recording.¬† According to this graph (with a bit of zooming and scrolling which the application allows for) the temperature at that point is around 170 and it takes another 30 seconds or so before the engine gets up to that 220-240 range that it appears to be in for the majority of the flight.¬† This tells me there is no worry with the engine getting to hot sitting and running on the ground as the temperature is only very slowly rising during the time it is idle or taxiing.¬† I always wondered with a tightly cowled engine like the Mustang just how hot it might get if forced to sit for a couple minutes on the ground.¬† Apparently just prop wash airflow is sufficient to keep the engine cool… at least for a couple minutes!¬† Looking at the green (voltage) line tells me my ignition is seeing anywhere from 5.17-5.29V for the duration of the session.¬† Apparently the regulator in the IBEC is getting a fairly constant voltage source from the receiver or is doing a great job regulating what it gets as this voltage is pretty solid and what variance there is does not track with RPM.¬† You would think running the engine at high RPM would require the most current draw and therefore cause a voltage drop if there was any problem with the regulator supplying the needed current so this is reassuring as well.¬† Lastly, the RPM graph shows RPM readings in the air peaking around 7600 RPM.¬† This is a good 800 RPM above static revs on the ground which is a bit more than I would have expected but not alarming and well within the limits that DA recommends.¬† So far all looks well and I’ve learned a bit about how the engine is performing and surviving in the air.

I’ll just call this part one and move onto some other graphs and information gleaned in the next post.