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Meaning of AO2 in automated station remarks

Remote Pilot (Part 107) practice question 16 of 18 on Weather / Sources. ACS element UA.III.A.K4 · difficulty: standard. Want to answer it in a timed quiz? Use the Remote Pilot (Part 107) practice mode.

Question bank updated 2026-09-22

QUESTIONAn automated METAR includes AO2 in the remarks section. What does this tell the remote pilot about the station?

  1. AThe automated station lacks a precipitation discriminator
  2. BThe automated station has a precipitation discriminator
  3. CThe second of two automated observations in the hour
Show the answer and explanation

Correct answer: B. The automated station has a precipitation discriminator

  • A — incorrect A station with no precipitation discriminator is indicated by AO1, not AO2.
  • B — correct The study guide states that AO2 in the remarks indicates the automated station is equipped with a precipitation discriminator.
  • C — incorrect AO1 and AO2 describe the type of precipitation sensors employed, not the count of observations.

BACKGROUND

When a METAR or SPECI comes from an automated source, the modifier AUTO appears in the body of the report. The remarks section then lists AO1 or AO2 to indicate the type of precipitation sensors employed at the automated station. AO1 means the station has no precipitation discriminator, and AO2 means it has a precipitation discriminator. Automated stations also use the remarks section to indicate when equipment needs maintenance.

STUDY TIP

Remember the pair as AO1 = no discriminator, AO2 = with discriminator. Both codes live in the RMK section, not in the modifier field.

KEY POINTS

  • AUTO in the body marks an automated report.
  • AO1 = no precipitation discriminator; AO2 = precipitation discriminator installed.
  • Automated stations flag equipment maintenance needs in the remarks.

SOURCES

  • remote_pilot_study_guide.txt, Chapter 3a "Aviation Routine Weather Report (METAR)", item 4 Modifier and item 12 Remarks
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SkyDrill is not affiliated with the FAA. This is an original practice item based on 14 CFR part 107, 14 CFR part 89, and the FAA Remote Pilot – Small UAS Study Guide (FAA-G-8082-22). Regulations and handbooks are revised; confirm details against the current edition.