Cleaning interval change between corrosion severity zones

Aviation Mechanic General (AMG) practice question 5 of 31 on Cleaning and Corrosion Control. ACS element AM.I.G.K5 · difficulty: applied. Want to answer it in a timed quiz? Use the Aviation Mechanic General (AMG) practice mode.

Question bank updated 2026-09-22

QUESTIONAn aircraft that was based in a mild corrosion severity zone is relocated to a severe zone. By how many days does the suggested interval between cleaning, inspection, lubrication, and preservation shorten?

A75 days
B45 days
C30 days, from 45 to 15

Show the answer and explanation

Correct answer: A. 75 days

A — correct The suggested interval is every 90 days in mild zones and every 15 days in severe zones, so the interval shortens by 90 minus 15, or 75 days.
B — incorrect Forty-five days is the suggested interval for a moderate zone; it is not the difference between the mild and severe intervals.
C — incorrect The mild-zone interval is 90 days, not 45; 45 days applies to moderate zones.

BACKGROUND

The handbook categorizes an aircraft's operational environment as mild, moderate, or severe with respect to corrosion severity. Factors that raise severity include airborne industrial pollutants, runway deicing chemicals, humidity, temperature, and prevailing winds from a corrosive environment. The suggested intervals for cleaning, inspection, lubrication, and preservation are every 90 days in mild zones, every 45 days in moderate zones, and every 15 days in severe zones. Maps of corrosion severity for North America and other regions are published in Advisory Circular (AC) 43-4.

STUDY TIP

Memorize the three intervals (90, 45, 15 days) and be ready to compute differences or ratios between them.

KEY POINTS

Mild zone: every 90 days
Moderate zone: every 45 days
Severe zone: every 15 days

SOURCES

FAA-H-8083-30B ch08 "Geographical Location"

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