If the pitot drain hole and static hole are blocked, readings will be:

• A. ASI and Altimeter = freezes, VSI = 0
• B. All readings go to zero
• C. ASI = freezes, Altimeter = accurate, VSI = 0
• D. VSI = freezes, ASI and Altimeter = 0

Answer: (A)

When both the pitot drain and the static hole are blocked, the pitot-static system becomes sealed, so no pressure signals can change in the lines that feed the instruments. The airspeed indicator relies on dynamic pressure from the pitot line minus the static pressure; with the pitot line effectively sealed and the static source blocked, the diaphragm can’t respond to any change, so the ASI freezes at the speed shown at the moment of blockage. The altimeter uses static pressure to determine altitude; if the static port is blocked, it no longer sees ambient pressure changes and will freeze at the altitude where the blockage occurred. The vertical speed indicator depends on the rate of change of static pressure; with the static signal blocked, there is no change to indicate, so it shows zero. That combination—ASI and altimeter frozen, VSI at zero—matches the described scenario.