aircraft systemsFAA-published sample question (AGI, Aug 2021)
Fouling of spark plugs is more apt to occur if the aircraft
A
gains altitude with no mixture adjustment.✓ Correct Answer
B
descends from altitude with no mixture adjustment.
C
throttle is advanced very abruptly.
Explanation
Climbing into thinner air without leaning makes the mixture progressively richer, and PHAK notes an excessively rich mixture causes rough running and spark plug fouling from carbon deposits. Descending without adjusting makes the mixture leaner, and abrupt throttle movement is not the typical cause of fouling.
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