← All explained questions · Supplemental · IX — Emergency Operations
If the engine begins running rough but doesn't fail, the FIRST troubleshooting steps in cruise are
Choices
shut down the engine immediately.
Don't shut down a running engine before troubleshooting.
✓ Apply CARB HEAT (carb ice is a common cause).correct
check MIXTURE (try richer or leaner depending on conditions), check FUEL SELECTOR (switch tanks if available), check MAGNETOS (try left and right separately to identify a bad mag), check PRIMER (locked?), MONITOR temps and pressures. Engine roughness sequence: carb heat (carb ice common), mixture (lean if fouled plugs, rich if running too lean), fuel selector (water in one tank?), magnetos individually (bad mag = roughness on one side only), primer (unlocked primer = rich miss), engine instruments (temp, pressure, EGT). If problem persists or worsens, divert to nearest suitable airport.
ignore it — it's probably nothing.
Roughness is always significant.
increase throttle to mask the roughness.
Throttle increase masks symptoms but doesn't fix problems.
Why
check MIXTURE (try richer or leaner depending on conditions), check FUEL SELECTOR (switch tanks if available), check MAGNETOS (try left and right separately to identify a bad mag), check PRIMER (locked?), MONITOR temps and pressures. Engine roughness sequence: carb heat (carb ice common), mixture (lean if fouled plugs, rich if running too lean), fuel selector (water in one tank?), magnetos individually (bad mag = roughness on one side only), primer (unlocked primer = rich miss), engine instruments (temp, pressure, EGT). If problem persists or worsens, divert to nearest suitable airport.
FAA source: AFH Ch 18, POH; AFH Chapter 18 — Emergency Proceduresbrowse the reference library →
Original study question written for this course — representative of FAA knowledge-test topics, not an actual current FAA exam question.