What happens to the altimeter when using an alternate static source?

What happens to the altimeter when using an alternate static source?

• A. It indicates lower than actual
• B. It indicates higher than actual
• C. It stops working
• D. It becomes unreliable

Answer: (B)

When using an alternate static source, the altimeter typically indicates higher than actual. This is because the alternate static source may be located in a position that is more affected by outside air pressure changes, such as being inside the cockpit rather than outside the aircraft. The outside pressure is usually lower than the internal cabin pressure, which can lead to an increase in the altimeter reading when switching to this source. Due to this phenomenon, pilots must be aware that the reading from the altimeter may not accurately represent true altitude when using an alternate static source. It's important for pilots to compensate for this difference when flying in instrument conditions, ensuring safety and accuracy in altitude reporting.

When using an alternate static source, the altimeter typically indicates higher than actual. This is because the alternate static source may be located in a position that is more affected by outside air pressure changes, such as being inside the cockpit rather than outside the aircraft. The outside pressure is usually lower than the internal cabin pressure, which can lead to an increase in the altimeter reading when switching to this source.

Due to this phenomenon, pilots must be aware that the reading from the altimeter may not accurately represent true altitude when using an alternate static source. It's important for pilots to compensate for this difference when flying in instrument conditions, ensuring safety and accuracy in altitude reporting.