SkyDrill

Spring-loaded induction filter door action

Aviation Mechanic Powerplant (AMP) practice question 9 of 13 on Reciprocating Engine Induction and Cooling Systems. ACS element AM.III.J.K6 · difficulty: standard. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONAn induction air filter becomes clogged with ice. In an installation that has a spring-loaded filter door, what happens?

  1. AThe door closes and seals the filtered-air entrance
  2. BThe door opens and keeps air flowing
  3. CThe door stays shut until alternate air is selected
Show the answer and explanation

Correct answer: B. The door opens and keeps air flowing

  • A — incorrect Closing the entrance would cut off airflow, the very thing the spring-loaded door exists to prevent.
  • B — correct Some installations have a spring-loaded filter door that automatically opens when the filter is excessively restricted, which prevents the airflow from being cut off when the filter is clogged with ice or dirt.
  • C — incorrect The spring-loaded filter door acts automatically on restriction; it does not wait for a selection.

BACKGROUND

When operation in a dusty atmosphere is necessary, the engine can be protected by an alternate induction system air inlet that incorporates a dust filter, normally made up of a filter element, a door, and an electrically operated actuator. In flight, with air filters operating, consideration must be given to icing that can come from surface icing or from freezing of a rain-soaked filter element. Some installations have a spring-loaded filter door that automatically opens when the filter becomes excessively restricted, preventing airflow from being cut off when the filter clogs with ice or dirt. Other systems use an ice guard, a coarse-mesh screen placed a short distance from the filtered-air entrance, so that when ice forms on the screen the air passes around it and into the filter element. The efficiency of any filter system depends on proper maintenance and servicing.

STUDY TIP

Both protections trade filtration for airflow. If a question asks what a restricted filter installation does, the answer keeps air flowing to the engine.

KEY POINTS

  • A spring-loaded filter door opens automatically when the filter is excessively restricted.
  • An ice guard screen lets air pass around it once ice forms, protecting the filter element.
  • Keeping airflow to the engine takes priority over filtering when the filter clogs.

SOURCES

  • amp-powerplant/ch03.txt "Induction System Filtering"
Practice the Aviation Mechanic Powerplant (AMP) test →Timed 100-question exam, by ACS area, or review your misses. Free.
MORE ON RECIPROCATING ENGINE INDUCTION AND COOLING SYSTEMS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-32B Aviation Maintenance Technician Handbook – Powerplant, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.