The alternate static valve switching to internal cabin pressure helps to maintain accurate indications during icing conditions.

The alternate static valve switching to internal cabin pressure helps to maintain accurate indications during icing conditions.

• A. True
• B. False
• C. Unspecified
• D. Not Applicable

Answer: (A)

Icing can block the outside static ports, which distorts the static pressure that the instruments rely on for accurate readings. The alternate static valve switches the static input to an internal cabin pressure source when the external port is compromised, keeping the pressure feeding the airspeed indicator, altimeter, and vertical speed indicator stable. This helps maintain usable and more accurate indications during icing conditions because the instruments aren’t fed by a blocked or distorted external port. You may see some small deviations in readings when using the alternate source, but they’re generally preferable to the larger errors caused by a blocked external static system.

Icing can block the outside static ports, which distorts the static pressure that the instruments rely on for accurate readings. The alternate static valve switches the static input to an internal cabin pressure source when the external port is compromised, keeping the pressure feeding the airspeed indicator, altimeter, and vertical speed indicator stable. This helps maintain usable and more accurate indications during icing conditions because the instruments aren’t fed by a blocked or distorted external port. You may see some small deviations in readings when using the alternate source, but they’re generally preferable to the larger errors caused by a blocked external static system.