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.



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.


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.


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