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Which condition is most likely to cause detonation?
Choices
✓ Using a fuel grade lower than specified for the enginecorrect
A lower-than-specified fuel grade is a classic cause of detonation.
Enriching the mixture during a high-power climb
A richer mixture actually helps cool the engine and prevent detonation.
Operating at low manifold pressure with high RPM
High manifold pressure with LOW RPM promotes detonation, not the reverse.
Keeping cylinder head temperatures low
Low cylinder head temperatures reduce, not increase, the risk of detonation.
Why
Detonation is promoted by a fuel grade lower than specified, an over-lean mixture at high power, and high manifold pressure with low RPM and high cylinder head temperatures; it is prevented with the correct fuel grade, a proper mixture, and reduced power or enrichment.
FAA source: PHAK Ch. 7browse the reference library →
Original study question written for this course — representative of FAA knowledge-test topics, not an actual current FAA exam question.