Saturday, July 22, 2017

Road test

No fancy pictures or videos of "flight" testing since we did not have an independent camera person and did not wish to sacrifice safety.

Melissa and I had a pre-flight safety briefing, established the "knock it off" protocol and the chain of command, and went over our test plan and what could go wrong. We conducted some tests, took some data, then returned home and had a quick debrief.

Our main safety issue is that holding a 5-foot pole with a thingey at the end of it is really hard work for the muscles, so any further testing should be done with some sort of mechanical fixture.

On the other hand, holding the pole made me aware of how turbulent the air is. It is not clear if that or my wobbly hold or something else caused the effect, but the airball display was wobbling all over the place. Actual flight testing will determine how much, if any, lowpass filtering we need in the device.

The XBee units seemed to need line-of-sight -- we would lose data if the probe was over the roof of the car. This might require a change in the form factor, e.g., an antenna that you stick onto the side windshield of the airplane. We'll see.

I have yet to determine the stability of my static pressure measurement. I don't think it's really worth messing with right now because the probe body is very poorly sealed. A future, properly sealed probe should give us better information. The ideal of course is that the static pressure remains the same going from zero to cruise speed and back. I'm sure most static pressure sources don't achieve that much, but it'd be interesting to see how well we do.

I have a bunch of data to crunch over the next couple of days and will be posting graphs as I have them. Stay tuned.

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