FAA Ground School Practice Test

What is the impact of a clogged pitot tube on an aircraft's instruments?

1. Loss of altitude information

2. Inaccurate speed readings

3. Correct reading of vertical speed

4. All instruments will remain functional

The correct answer is: Inaccurate speed readings

When a pitot tube becomes clogged, it primarily affects the measurement of airspeed. The pitot tube is essential for determining dynamic air pressure, which is critical for calculating the aircraft's indicated airspeed. If the tube is blocked, it will not be able to measure the outside air pressure accurately, leading to incorrect speed readings that can misinform the pilot about the aircraft’s actual performance. While altitude information and vertical speed may remain unaffected because those instruments rely on static pressure rather than the dynamic pressure measured by the pitot tube, the pitot-static system can be complex, and depending on the aircraft configuration, some altitude readings may also show discrepancies in certain situations. However, the direct impact of a clogged pitot tube is most prominently seen in the airspeed indicator, making inaccurate speed readings the most appropriate answer. Essentially, understanding this concept is crucial for pilots to comprehend how instrument readings correlate with actual aircraft performance and to ensure safe and accurate operation of the aircraft.