GPS Telemetry – First Flight

I picked up the Spektrum GPS module over the Christmas holiday.  Somehow I was not even aware when this item came on the market but when I saw the ad for it I knew I had to try it.  I immediately dropped an email to my friendly local hobby shop and a few days later I picked it up.  I already have telemetry in my Wildhare 50cc size Slick as well as my Topflite P51 “Redtail” Mustang but this, in my mind, was a totally different level.  I’ve already posted on some basic telemetry usage in my Radian glider, but being able to track altitude, heading and speed in addition to GPS coordinates was potentially a game changer.  In my mind, there were so many possible upsides to this new sensor.

The module is a bit pricey, but you have to keep in mind that the GPS module is a possible replacement for a couple of the other existing Spektrum sensors and therefore some of the sting of the ~$100 price tag is diminished.  When you throw in the heading and position facilities the module starts to seem a bit more reasonable.  Lets be honest, none of us fly RC airplanes because its a particularly cheap hobby do we?

That was my train of thought when I got busy and installed a TM1000 and the GPS module in my trusty Telemaster 40.  Looking at the local weather forecast on the shop TV convinced me to add the floats as well.  Skis work in some snow conditions but I have found floats work well on a wide variety of ice/snow or water.  A quick test start on the trusty Saito 82 and a good overnight charge and all was ready.  A couple days and 4-6 or maybe it was 6-8 inches of white stuff later and January 1st, 2013 dawned calm and cool.  Time to test out the new GPS module!

After a nice long flight, I entered our club’s nicely heated shelter, downloaded the telemetry file and emailed it to my old (original model) Ipad.  As you can see by this clip (I’ll insert a video here eventually) the STI application can overlay the collected flight track on what appears to be a satellite shot of the flying field.  Then you can replay and watch as the entire previous flight plays out as a small airplane icon moves across the map and leaves behind a trail of arrows.  A window can be brought up showing all the GPS information as the flight plays out on the map.  By noting the heading, altitude, speed, etc… and comparing to the track you quickly start to recognize loops and stall turns and can easily see just how close you came to that tree line or how high you really flew.  This is extremely cool stuff with some real life usefulness behind it.  Here is a small sample video showing the first minute or so of my flight.

You can see a fair bit of information in this.  First its around 808ft above sea level at our field.  You’ll see it on the screen until about 24 seconds in when I take off.  You’ll also notice the time in UTC format.  Locally it’s a minute or so after 9AM which is when we were allowed to start flying the “noisy” planes at this event.  My speed ranges up to about 65mph (that is full throttle and a pretty steep dive) and my max altitude above the 808 foot base seems to be about 250 feet toward the end of the clip.  At about 1:23 you will see the speed drop to near zero and a very quick heading change as I perform a stall turn… at least the best I could with floats on a Telemaster!  It takes a bit to figure things like that out.  You just have to imagine what is happening that would cause the changes in altitude, airspeed and heading to reason it through in most cases.
Of course there is plenty of room for improvement.  Here’s my top three:
  • Allow me to pause the flight and clear all those little arrow tracks.  After a while I can’t see the airplane icon for all the little arrows.
  • Give me the ability to “zero” the altitude with the push of a button and let the program do the math to tell me what the variance in altitude is from that point on.
  • Put a scale of some sort on the screen so I can get some sort of idea of relative distance… even better if I could set a zero point just as I’d like to do with altitude and let me see distance from that point.

Having said that, this technology makes a lot of valuable information available to us.  During part of my flight I flew out “close” to our northern tree line… or so I thought.  On review I had more available space than I thought.  Very good to know.  When practicing for IMAC, one of the prominent issues to watch for is flying a straight line parallel to the runway with a constant altitude.  Without the ability to do this you will never score well at a contest.  This is a lot more difficult than you might believe.  With GPS telemetry, you can answer these question once and for all.  As you might guess, the GPS module has already been moved (likely permanently) into my Slick (my IMAC dabbling plane) and another has been ordered.

How fast?  How far?  How high? Where?  When?  All those questions are answered once and for all with GPS.  I can’t wait to get a plane in the air with a GPS combined with a “full boat” of other sensors.  Ever wonder how your engine temperature varies with throttle and speed?  What the unloaded RPMs really are in flight?  I’m looking forward to learning all those things during this upcoming flying season.

I’ll try to write up an article some time soon showing all the Spektrum Telemetry pieces and parts and the ins and outs of making the system work.  There are some small quirks but nothing overly difficult and the information gained is fascinating.

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