Over the weekend I did my first Balloon assisted flight. Helium balloon carried my glider up to 13,000ft, at that point i issued a remote cutdown command to release the balloon from the plane.
http://twitter.com/#!/W0OTM/status/130798913224577024/photo/1
We ha some issues...First know that shortly after launch the XMTR was turned off, to initiate RTL mode. So, for the majority of the flight (20min) it was in RTL mode while suspended from the balloon.
After finding the wreckage, I began to filter though the logs. (the APM survived the crash) Here is what i found.
The pressure sensor began sending erroneous readings as 1137m (4,000ft) or so. Here is a sample of the logs.
GPS: 71299000, 1, 11, 41.1029510, -92.4485240, 0.0000, 1137.9200, 1294.2400, 2.2300, 338.1000
GPS: 71299000, 1, 11, 41.1029510, -92.4485240, 0.0000, 950.5000, 1294.2400, 2.2300, 338.1000
GPS: 71299250, 1, 11, 41.1029590, -92.4485240, 0.0000, 821.7400, 1296.0200, 1.9200, 18.2300
GPS: 71299250, 1, 11, 41.1029590, -92.4485240, 0.0000, 650.5400, 1296.0200, 1.9200, 18.2300
GPS: 71299250, 1, 11, 41.1029590, -92.4485240, 0.0000, 452.5100, 1296.0200, 1.9200, 18.2300
GPS: 71299500, 1, 11, 41.1029590, -92.4485170, 0.0000, 238.2400, 1297.8101, 2.3700, 38.0600
GPS: 71299500, 1, 11, 41.1029590, -92.4485170, 0.0000, 15.0300, 1297.8101, 2.3700, 38.0600
GPS: 71299750, 1, 11, 41.1029660, -92.4485170, 0.0000, -137.8500, 1299.6100, 2.8800, 55.0100
GPS: 71299750, 1, 11, 41.1029660, -92.4485170, 0.0000, -316.5000, 1299.6100, 2.8800, 55.0100
GPS: 71299750, 1, 11, 41.1029660, -92.4485170, 0.0000, -439.2400, 1299.6100, 2.8800, 55.0100
GPS: 71300000, 1, 11, 41.1029700, -92.4485090, 0.0000, -523.8900, 1301.4301, 3.1900, 61.0800
GPS: 71300000, 1, 11, 41.1029700, -92.4485090, 0.0000, -582.4400, 1301.4301, 3.1900, 61.0800
GPS: 71300250, 1, 11, 41.1029700, -92.4485020, 0.0000, -623.2000, 1303.2400, 3.6500, 58.7000
Also, the IMU axis sensors stopped sending values at 7000ft. Also note the HUGE difference in the MIXALT and the GPSALT.
GPS: 71460500, 1, 10, 41.1069680, -92.4342270, 0.0000, 140.1700, 2359.3101, 15.8400, 99.1400
ATT: -17273, -7770, 1014
GPS: 71460500, 1, 10, 41.1069680, -92.4342270, 0.0000, 140.7600, 2359.3101, 15.8400, 99.1400
ATT: -16141, -8484, 35974
GPS: 71460750, 1, 10, 41.1069640, -92.4341740, 0.0000, 141.4400, 2360.8999, 15.1800, 100.5000
ATT: -11298, -8952, 31063
GPS: 71460750, 1, 10, 41.1069640, -92.4341740, 0.0000, 141.8600, 2360.8999, 15.1800, 100.5000
ATT: 0, 0, 0
GPS: 71460750, 1, 10, 41.1069640, -92.4341740, 0.0000, 142.5400, 2360.8999, 15.1800, 100.5000
ATT: 0, 0, 0
GPS: 71461000, 1, 11, 41.1069560, -92.4341280, 0.0000, 143.3000, 2362.7300, 14.6200, 101.7700
ATT: 0, 0, 0
What would have caused these 2 failures?
Replies
cosmic rays ;) just kidding
Sort of on the subject of the pressure sensor (which drives the non GPS altitude), the data sheet says that the hole in the top should not be exposed to light (during reading) as it can "influence the accuracy of the measurement". I thought that was interesting for those that mount their APM board facing the sky.
http://www.sparkfun.com/datasheets/Components/General/BST-BMP085-DS...
page 25.
Hello to
Ottumwa, IA
Barometer problems could be due to temperature extremes and wind. It's recommended to cover it with a piece of foam.
Marshal I have experienced something very similar around the same altitude.
I have replicated it twice.
Around 1300m, my APM started reporting -1000m altitude (so of course started climbing).
Details are here...
http://diydrones.com/forum/topics/nasty-altitde-bug