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Old May 25th 18, 09:15 PM posted to rec.aviation.soaring
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Default Pitot system - odd event

On Friday, May 25, 2018 at 9:27:39 AM UTC-7, wrote:
On Friday, May 25, 2018 at 11:23:52 AM UTC-4, wrote:
This happened on my ASW-15 a few years back - when it was stored in the locked trailer in a garage over the winter. It was fine on the last flight of the year at the end of October and when I took it in for the annual in spring I noticed the ASI was off when I looked in the cockpit. The diaphragm had burst at the edge sometime during the off season. I think in my case it was just age.

It is quite common that moisture builds up in the diaphragm and causes corrosion at the bottom edge, eventually leading to failure.
I've seen it a dozen times.
Any glider kept outside that has had a pitot blocked by water needs to be drained and dried. Obvious, but people don't do it.

I never leave my glider out BUT now that I think of it that particular autumn most of the flying days we had humidity around 90%+ and the temperature and dew point were frequently very close. Whenever I rolled to a stop on landing the wings were almost instantly covered in moisture, the face of my electronic vario had some moisture condensed on the glass face quite often and once the radio acted up and when I took off the top plate I saw that the top of the circuit board was covered in dew... It worked fine when I dried it out in a warm room but I wouldn't be surprised if moisture condensed in the ASI led to corrosion and failure.