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All-purpose dry chemical powder

Aviation Mechanic Airframe (AMA) practice question 9 of 9 on Airframe Fire Protection Systems. ACS element AM.II.M.K5 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Airframe (AMA) practice mode.

Question bank updated 2026-09-22

QUESTIONWhich dry chemical extinguishing powder carries an all-purpose Class A, B, and C rating?

  1. ASpecialized dry powder
  2. BMono-ammonium phosphate
  3. CEvery other dry chemical powder
Show the answer and explanation

Correct answer: B. Mono-ammonium phosphate

  • A — incorrect Specialized dry powder is the agent for Class D combustible metal fires and is suitable for ground operations, not an all-purpose rating.
  • B — correct The only all-purpose dry chemical powder extinguishers, rated Class A, B, and C, contain mono-ammonium phosphate.
  • C — incorrect All other dry chemical powders carry a Class B, C rating only.

BACKGROUND

Class A, B, or C fires can be controlled by dry chemical extinguishing agents, and the handbook singles out one formulation as all-purpose. Dry chemicals are effective, but their use is limited by the residue they leave and the cleanup that follows a discharge. For that reason dry chemicals are listed as unsuitable for cabin or flight deck hand-held extinguishers, both because of possible corrosion damage to electronic equipment and because a discharge can obscure vision. Water is best on Class A fires because it cools the material below its ignition temperature and soaks it to prevent reignition. Specialized dry powder is the Class D agent, and the extinguisher manufacturer's recommendations must be followed because of possible reaction with the burning metal.

STUDY TIP

Tie each agent to its fire classes in one pass: water to A, carbon dioxide to B and C, dry chemicals and Halons to A, B, and C, and specialized dry powder to D.

KEY POINTS

  • Mono-ammonium phosphate powder is the only all-purpose A, B, C dry chemical.
  • All other dry chemical powders are rated Class B and C only.
  • Dry chemicals are unsuitable for cabin and flight deck hand-held use.

SOURCES

  • sources/ama-airframe/ch17.txt "Dry Powders"
  • sources/ama-airframe/ch17.txt "Extinguisher Types"
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MORE ON AIRFRAME FIRE PROTECTION SYSTEMS

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-31B Aviation Maintenance Technician Handbook – Airframe, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.