Static line fracture in level flight can cause the ASI and altimeter to read high, with the VSI briefly showing a climb before leveling. Which option correctly describes this scenario?

• A. ASI overread; Altimeter overread; VSI climb briefly then level
• B. ASI underread; Altimeter underread; VSI descent then level
• C. ASI overread; Altimeter underread; VSI level flight
• D. ASI steady; Altimeter overread; VSI climb

Answer: (A)

A static line fracture introduces a leak in the static pressure system that feeds the altimeter, VSI, and other instruments. In level flight, the pitot tube still supplies total pressure, so the ASI detects a larger difference between total pressure and the now-leakily reduced static pressure. That makes the ASI indicate a higher airspeed than actually present. The altimeter uses static pressure to determine altitude, and with the static pressure lower than it should be, it overreads, showing a higher altitude. The VSI reacts to changes in static pressure; when the leak occurs, the static pressure in the instrument system changes rapidly, which can momentarily be interpreted as a climb, and then as the system settles to the new condition, the VSI returns to level flight. So you get ASI overread, altimeter overread, and a brief VSI climb before leveling.