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248 kts airspeed??

Jake14

Well Known Member
While descending from altitude, the EFIS stall warning went off, the airspeed showed 250kts and the wind speed showed 198kts while GPS ground speed and the analog ASI were normal (see pics). Glad I had the analog gauge and GPS to reassure me something terrible wasn't happening. Jonathon at AFS did a great job of analyzing the logs which clearly indicated a static system blockage in the tubing branch going out the wing to the AHARS. Water in that tube froze at altitude while the tubes going to the analog gauge were clear.

So my question is: what are some options on keeping the RV-14 static system clear of moisture? My old Cessna had a sump bottle near the static port but I'm not sure that would have helped in this case.

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Do you have two static sources on the sides of the fuselage and the hoses first go up, then tee together before heading into your instrument panel? Going up should prevent water from entering the system.
 
It looks like an airframe overspeed alarm rather than a stall alarm. It sounds like you're static source in on the wing rather than the fuselage side like in my RV-14. As Tom notes, that design has the static line go up first to avoid any traps for water to accumulate. In any case, the lines are in the fuselage and less likely to freeze. Did you also notice the EFIS altimeter fail to track your altitude as you descended? It appears to be showing a reasonable VS of -350 ft/min. Could there be an issue with your AHARS?
 
static lines and port locations are per the plans. The audio alarms were "angle, angle, push" and "overspeed". You can see the AOA indicator showing stall. I had the static system opened up for a couple of weeks recently during a lot of moist weather so I'm guessing some water or condensation collected at the lowest point (the wing root). The airplane's tied down outside. I'm thinking a sump bottle near the wing root might be a good idea....
 
It was helpful to think about your issue with respect to my recently completed RV-14A and how the instruments would behave in the event of static system failure. I see little chance of water entering my static system and certainly not freezing since the entire system resides within the fuselage. Can't advise you on the sump bottle, but good luck finding a solution that works for you.
 
Installed a alt static switch from Stein, under the panel for that reason, although I have never had that issue happen to me.
 

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