A technician performing a scheduled inspection on a reciprocating engine notices the induction air filter is heavily loaded with dust and oil residue, significantly restricting airflow. What is the most likely operational effect of continuing to operate the engine with this filter condition?
- ANo measurable effect since the alternate air source compensates automatically at all times
- BIncreased manifold pressure and improved fuel economy
- CImproved induction icing resistance due to reduced airflow
- DReduced airflow to the engine causing a rich fuel/air mixture and possible power loss
Show answer & explanationAnswer & explanation
Correct answer: D. Reduced airflow to the engine causing a rich fuel/air mixture and possible power loss
A restricted induction air filter reduces the volume of air reaching the engine, which shifts the fuel/air mixture toward rich (since fuel metering assumes normal airflow), resulting in reduced power output, rough running, and increased fuel consumption. This is the opposite of improved economy or icing resistance, and alternate air typically activates only when selected or automatically at low manifold pressure, not as a general compensation.
Why the other options are wrong
- A. Alternate air doors are not always automatic or engaged; a clogged filter alone does not guarantee compensation.
- B. A restricted filter reduces, not increases, airflow and manifold pressure.
- C. Reduced airflow does not improve icing resistance; icing is related to temperature/humidity, not filter condition.
Induction Air Filter Restriction
A clogged or heavily contaminated induction air filter that reduces airflow to the engine, causing an abnormally rich fuel/air mixture and reduced engine power.
- Inspected during scheduled maintenance for dust/oil buildup
- Restriction reduces airflow, enriching the fuel/air mixture
- Can cause rough running, power loss, and increased fuel consumption
- Serviced by cleaning or replacing the filter element per manual
Memory trick: Clogged filter, choked breath — engine gets fuel but not enough air.