Turbulence

050-02-06Pablo Asensio Martínez2026-04-011 min

Turbulence is the irregular and violent movement of air that causes the aircraft to shake.

Types of Turbulence

1. Convective Turbulence (Thermal)

  • Cause: Uneven heating of the Earth's surface generating updrafts and downdrafts.
  • Associated with: Vertically developed clouds (Cumulus and Cumulonimbus).
  • Critical time: Early afternoon (when solar heating is maximum).
  • Location: Below cumulus clouds (rising air) and inside them.

2. Mechanical Turbulence (Frictional)

  • Cause: Physical obstructions to wind flow (buildings, trees, hills).
  • Location: Friction layer (up to 2000-3000 ft).
  • Factors:
    • Wind speed (generally > 20 kt).
    • Terrain roughness.
    • Air stability.

3. Orographic Turbulence (Mountain Waves)

  • See previous section (050-02-05).
  • The most dangerous zone is the Rotor, on the leeward side of the mountain.

4. Clear Air Turbulence (CAT)

  • Definition: Severe turbulence in cloudless air (or outside convective clouds), generally at high altitude (> 20,000 ft).
  • Cause: Wind shear associated with Jet Streams.
  • Detection:
    • Invisible to weather radar and satellites (no water/ice particles to reflect the signal).
    • Only reliable source: Reports from other pilots (AIREPs / PIREPs).

Wind Shear

It is a sudden change in wind direction and/or speed over a short distance (vertical or horizontal). It can occur at any level, but is critical at low altitude during takeoffs and landings.

Gusts

Sudden and brief increases in wind speed.

  • Reported when the speed exceeds the mean wind by at least 10 kt.
  • Typical duration: a few seconds (average of 3 seconds).