FAA Sport Pilot Airplane (SPA)WeatherMedium
A pilot receives a PIREP that states: 'OCNL MOD CHOP 8000 FT.' How should the pilot interpret this report?
- AOccasional moderate chop causing rapid, rhythmic bumpiness without significant changes in altitude or attitude
- BOccasional moderate turbulence that momentarily causes loss of aircraft control
- CContinuous light turbulence with slight, erratic changes in altitude
- DOccasional severe turbulence causing abrupt changes in altitude and attitude
Show answer & explanationAnswer & explanation
Correct answer: A. Occasional moderate chop causing rapid, rhythmic bumpiness without significant changes in altitude or attitude
'Chop' describes rapid, rhythmic bumpiness without large changes in altitude or attitude, and moderate intensity means variations in indicated airspeed may occur. 'OCNL' means the condition affects less than 1/3 of the time period reported.
Why the other options are wrong
- B. Moderate turbulence does not cause momentary loss of control; that describes severe or greater.
- C. Chop is not the same as continuous light turbulence.
- D. Severe turbulence would be reported as 'SEV,' not 'MOD.'
PIREP Turbulence Terminology
Pilot reports use standardized terms (light, moderate, severe, extreme) and qualifiers (occasional, intermittent, continuous) to describe turbulence intensity and frequency.
- Chop = rapid, rhythmic bumpiness without altitude/attitude change
- Turbulence = more abrupt changes in altitude and/or attitude
- OCNL = less than 1/3 of the time period
- Severe turbulence causes large, abrupt changes in altitude/attitude and momentary loss of control
Memory trick: Chop is a Choppy Boat Ride — bumpy but steady, not tossed around.