On Wednesday, June 5, 2013 8:41:20 AM UTC-7, Matt Herron Jr. wrote:
Can anyone share some wisdom on using water at high elevations for long durations? How do you know your fin or wing tanks will not freeze? If I am at 18K for 6 hrs in the Sierras, I really don't want my vertical stab splitting open in flight. Has this ever happened? Any guidance would be appreciated.



Matt

I know in the Duo Discus I used to own (part of) the OAT gage was a required instrument just for this reason. It will take a long time for a wing tank, or even a fin tank to freeze. But we did have an incident where a dribbling leak from the fin tank collected in the rudder counterbalance and froze, freezing the rudder solid. This was on a day when the return from Mt. Whitney to Truckee was a no-turn romp at 17,999 ft. It did finally unfreeze as the Duo descended on final. I don't know of anyone who has had a fin tank freeze.