Wake Turbulence
Definition
Wake turbulence refers to the disturbed airflow generated behind an aircraft, primarily caused by wingtip vortices, prop wash, and jet blast. It is especially hazardous during takeoff, landing, and in-flight when one aircraft follows another too closely. Wake turbulence is invisible but powerful and has the potential to cause control loss, especially in light aircraft operating behind larger ones.
What Causes Wake Turbulence?
- As lift is generated, high-pressure air from beneath the wing flows around the wingtips to the low-pressure area above, forming wingtip vortices
- Larger and heavier aircraft, especially those flying slow and clean (flaps up), generate the strongest vortices
- Vortices descend and drift with the wind and may persist for 2–3 minutes
Types of Wake Turbulence
| Type | Source | Description |
|---|---|---|
| Wingtip vortices | All fixed-wing aircraft | Spiral airflows trailing from wingtips, main source of wake turbulence |
| Jet blast | Jet engines | High-speed exhaust affecting ground traffic and structures |
| Prop wash | Propeller aircraft | Rearward airflow from propeller rotation |
Wake Turbulence Categories (ICAO)
Aircraft are classified by MTOM (Maximum Take-Off Mass):
| Category | Weight | Label |
|---|---|---|
| L (Light) | ≤ 7,000 kg | Light |
| M (Medium) | 7,001–136,000 kg | Medium |
| H (Heavy) | > 136,000 kg | Heavy |
| J (Super) | e.g., Airbus A380 | Super Heavy |
Note: ATC uses these labels to assign separation minima and issue wake turbulence advisories.
Phraseology Examples
- “Caution wake turbulence, departing heavy Airbus A330”
- “Line up and wait, behind landing traffic, caution wake turbulence”
- “Maintain visual separation, report in sight”
Separation Standards (Wake Turbulence Dependent)
| Preceding Aircraft | Following Aircraft | Minimum Separation |
|---|---|---|
| Heavy | Light/Medium | 2–5 NM or 2 minutes |
| Super | Any category | 3–6 NM or 3 minutes |
| Same category | Same | 2–3 NM |
Separation is greater in non-radar or VFR environments. At uncontrolled aerodromes, pilots are responsible for self-separation.
Avoiding Wake Turbulence
- ✅ Stay above and upwind of the preceding aircraft's path
- ✅ On final approach, remain above the glide path and land beyond the touchdown point of a heavier aircraft
- ✅ During takeoff, rotate before the rotation point of the aircraft ahead and climb above its flight path
- ✅ Use ATC-recommended spacing and be ready to go around if necessary
When to Be Most Cautious
- Light aircraft following heavier traffic
- Calm winds, where vortices settle on the runway
- Parallel runways or closely spaced arrivals
- Crosswind components carrying vortices laterally
Tips for Pilots
- Listen for aircraft wake category callsigns (e.g., “Austrian 253 Heavy”)
- Don't hesitate to refuse or delay clearance if spacing is insufficient
- Use LearnATC simulator scenarios to recognize and respond to wake turbulence situations