M-20 pilot reported a possible pitot static issue which caused an unreliable airspeed. The pilot was unaware of the issue during landing and the aircraft stalled and contacted the surface prior to the runway incurring damage.
Synopsis
M-20 pilot reported a possible pitot static issue which caused an unreliable airspeed. The pilot was unaware of the issue during landing and the aircraft stalled and contacted the surface prior to the runway incurring damage.
Narrative
Aircraft was picked up from ZZZ1 by PIC to fly back to home airport (ZZZ). Weather clear; winds calm. Runup and operation appeared in order. On departure (RWY XX) climbout positive; although there was fluctuation in both VSI and somewhat in altimeter (pitot-static operation concern). Other instrument indications were fine.Climbed to 6500; direct course for ZZZ; with Garmin 430W and STEC50 autopilot. Flight parameters monitored with Foreflight on iPad. Note on flightpath: GPSS function for STEC 50 indicated active but light flickered and tracking was not precise. Switch to Hdg mode; which was accurate and stable. Flight Following via ATC. Decent from 6500 to 2500 with ATC approval followed by cancel Flight Following and return to VFR/1200 transponder. Noted similar fluctuation in VSI and progression by altimeter. Arrived at ZZZ and joined left downwind for RWY YY. AWOS from ZZZ indicated calm; no winds at surface noted. Pattern flown as trained and POH; 15 deg flaps end runway; gear down; 100 mph airspeed. Left base 100-90 mph; 30 deg flaps at turn into final. Final altitude about 500 AGL; indicated airspeed remained about 90 mph trim configured for final. Noted that configuration seemed to require a little less throttle to keep airspeed (based on experience) and progressed to high 80s mph final 300 yards from end of runway; past fence appeared OK; then at about 200 yards/about 75 ft AGL stall warning; then within 1-2 seconds; stalled to ground contact too fast to respond to throttle increase. After stopping; aircraft about 100 yards to runway; right gear torn off; nose gear collapse. I did not have any obvious injuries; turned off magnetos and master switch. about XA25 dusk; clear calm weather. Airport personnel contacted and FSDO contact. Concern and/or speculation is that a pitot-static problem caused airspeed error; resulting in inaccurate; higher that actual speeds readings; allowing for approach that was near stall speed. Vs0 62 mph in M20F at normal configuration. (Pitot-Static system underwent biannual certification in Month/Year).
NASA callback
The reporter indicated a possible reason for the unreliable airspeed was water inside the pitot static lines. The pitot static system has been removed from the aircraft and it is in the process of being evaluated.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.