Wake Turbulence

Understand how aircraft wake vortices form and move, when they are strongest, and how pilots avoid them during takeoff, approach, landing, and cruise flight.

Wake Turbulence

Introduction to Wake Turbulence

  • Every aircraft generates a wake while in flight.
  • Wake turbulence is a function of an aircraft producing lift, creating a vortex that forms two counter-rotating vortices trailing behind the aircraft.
  • The strength and behavior of vortices generated by one aircraft can create hazardous wake turbulence for an aircraft that encounters them.
    • Vortices can impose rolling moments that exceed the roll-control authority of the encountering aircraft, potentially causing injury to occupants and damage to the aircraft.
  • In a slow hover taxi or stationary hover near the surface, the helicopter's main rotor(s) generate downwash, producing high velocity outwash vortices to a distance approximately three times the diameter of the rotor.
  • Pilots must learn to envision the location of the vortex wake generated by larger aircraft and adjust the flight path accordingly.
  • Reinforce your understanding of Wake Turbulence by completing the knowledge quiz and interactive scenario, comparing your performance with the applicable Airman Certification Standards, and reviewing the topic summary before moving on.
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Wake Turbulence

Wake Turbulence Key Highlights

  • Wake turbulence is generated by wingtip vortices created as an aircraft produces lift during flight.
  • Wingtip vortices are strongest when an aircraft is heavy, clean, and operating at slow airspeeds.
  • Wake turbulence can cause abrupt rolling moments and loss of aircraft control for following aircraft.
  • Large aircraft, especially heavy transport-category airplanes, produce the most significant wake turbulence hazards.
  • Wake vortices typically sink below the generating aircraft’s flight path and drift with the wind.
  • Pilots should remain above and upwind of a preceding aircraft’s flight path whenever possible.
  • Takeoff, landing, and low-altitude operations present the greatest risk of wake turbulence encounters.
  • Air traffic control wake turbulence separation standards help reduce the risk of hazardous vortex encounters.
  • Crosswinds can move wake vortices onto adjacent runways or taxiways, increasing operational hazards.
  • Understanding wake turbulence improves situational awareness, traffic spacing decisions, and overall flight safety.
Wake Turbulence

Vortex Formation

  • Wake Vortex Generation
    Wake Vortex Generation
  • The creation of a pressure differential over the wing surface generates lift.
  • The lowest pressure occurs over the upper wing surface, and the highest pressure occurs under the wing.
  • This pressure differential triggers the roll-up of the airflow at the rear of the wing, resulting in swirling air masses trailing downstream of the wingtips.
  • After the roll-up, the wake consists of two counter-rotating cylindrical vortices. []
  • The wake vortex forms with most of the energy concentrated within a few feet of the vortex core.
  • More aircraft are being manufactured or retrofitted with winglets to increase fuel efficiency (by improving the lift-to-drag ratio).
    • Studies have shown, however, that winglets have a negligible effect on wake turbulence generation, particularly with the slower speeds involved during departures and arrivals.

  • Vortex Strength:

    • Wake Encounter Counter Control
      Wake Encounter Counter Control
    • The strength of the vortex depends on the weight, speed, wingspan, and shape of the generating aircraft's wing.
      • The vortex strength from an aircraft increases proportionately to an increase in operating weight or a decrease in aircraft speed.
    • Characteristics change with the extension of flaps or other wing-configuring devices.
    • An aircraft creates the greatest vortex strength when:
      • Heavy.
      • Clean.
        • A dirty aircraft configuration hastens wake decay.
      • Slow.
    • Wake turbulence is near maximum behind a jet transport immediately after takeoff because the aircraft is typically heavy and flying relatively slowly at a high angle of attack, requiring substantial lift and producing strong wingtip vortices.
    • Wake turbulence can remain hazardous behind a jet transport during final approach and landing because the aircraft is flying slowly while producing substantial lift. Vortex generation continues until touchdown.
    • High wing loading amplifies the effects of vortex strength.
    • Landing gear and flap extension tend to disrupt wake formation and reduce vortex intensity.
    • The terminal area presents a common high-risk setting because aircraft are slow, close to the ground, and have little altitude available for recovery.

    • Induced Roll:

      • In rare instances, a wake encounter could cause catastrophic in-flight structural damage to an aircraft.
        • However, the usual hazard is associated with induced rolling moments that can exceed the roll-control authority of the encountering aircraft.
        • Induced roll is especially dangerous during takeoff and landing when there is little altitude for recovery.
      • During in-flight testing, the aircraft intentionally flew directly through the trailing vortex cores of larger aircraft.
        • These tests demonstrated that the ability of aircraft to counteract the roll imposed by wake vortex depends primarily on the wingspan and counter-control responsiveness of the encountering aircraft.
        • These tests also demonstrated the difficulty for an aircraft to remain within a wake vortex.
        • The natural tendency is for the circulation to eject aircraft from the vortex.
        • Counter-control is usually effective and induces minimal roll in cases where the wingspan and ailerons of the encountering aircraft extend beyond the rotational flow field of the vortex.
        • It is more difficult for aircraft with a short wingspan (relative to the generating aircraft) to counter the imposed roll induced by vortex flow.
      • The wake of larger aircraft requires the respect of all pilots.
      • Pilots of short-span aircraft, even of the high-performance type, must be especially alert to vortex encounters. []
Wake Turbulence

Vortex Behavior

  • Wake Ends/Wake Begins
    Wake Ends/Wake Begins
  • Vortex Flow Field
    Vortex Flow Field
  • An aircraft generates vortices from the moment it rotates on takeoff until touchdown, since trailing vortices are a by-product of wing lift. []
    • Before takeoff or touchdown, pilots should note the rotation or touchdown point of the preceding aircraft.
  • Wake Ends/Wake Begins
    Wake Ends/Wake Begins
  • Circulation is outward, upward, and around the wing tips.
    • Vortices remain spaced less than a wingspan apart, drifting with the wind at altitudes greater than a wingspan above the ground.
    • Given this, if encountering persistent vortex turbulence, a slight change of altitude (upward) and lateral position (upwind) should provide a flight path clear of the turbulence.
  • Those from larger aircraft sink at a rate of several hundred feet per minute, slowing their descent and diminishing in strength with time and distance behind the generating aircraft. []
    • When present, atmospheric turbulence hastens breakup.
    • Pilots should fly at or above the preceding aircraft's flight path, altering course as necessary to avoid the area directly behind and below the generating aircraft.
    • A 1,000-foot vertical separation may reduce the likelihood of a wake encounter, but it does not ensure avoidance; vortices from Heavy and especially Super aircraft may descend more than 1,000 feet before decaying to a less perceptible residual strength.
  • When vortices sink close to the ground (within 100 to 200 feet), they tend to move laterally over the ground at a speed of 2 or 3 knots. [//]
  • Vortex Flow Field
    Vortex Flow Field
  • Pilots should remain alert for possible wake vortex encounters in all phases of flight, particularly during takeoff, approach, and landing.
    • The pilot is ultimately responsible for maintaining an appropriate interval and should consider all available information in positioning the aircraft in the terminal area to avoid the wake turbulence created by a preceding aircraft.
    • Test data show that vortices can rise with the air mass that contains them.
    • The effects of wind shear can cause a vortex flow field "tilting."
    • In addition, ambient thermal lifting, orographic effects (such as rising terrain or tree lines), can cause a vortex flow field to rise and possibly bounce.
  • A crosswind will decrease the lateral movement of the upwind vortex and increase the movement of the downwind vortex.
  • Thus, a light wind with a cross-runway component of 1 to 5 knots could result in the upwind vortex remaining in the touchdown zone for some time and hasten the drift of the downwind vortex toward another runway.
  • A tailwind condition can cause the vortices to move forward into the touchdown zone.
  • The light quartering tailwind requires maximum caution.
  • Vortex Movement in Ground Effect - Tailwind
    Vortex Movement in Ground Effect - Tailwind

  • Operations Problem Areas:

    • Vortex Movement Near Ground - No Wind
      Vortex Movement Near Ground - No Wind
    • Vortex Movement Near Ground - with Cross Winds
      Vortex Movement Near Ground - with Cross Winds
    • The probability of induced roll increases when the encountering aircraft's heading generally aligns with the flight path of the generating aircraft.
    • A crosswind will decrease the lateral movement of the upwind vortex and increase the movement of the downwind vortex.
      • Thus, a light wind with a cross runway component of 1 to 5 knots could result in the upwind vortex remaining in the touchdown zone for a period of time and hasten the drift of the downwind vortex toward another runway.
      • Similarly, a tailwind condition can cause the vortices of the preceding aircraft to move forward into the touchdown zone.
      • THE LIGHT QUARTERING TAILWIND REQUIRES MAXIMUM CAUTION.
      • Pilots should be alert to large aircraft upwind from their approach and takeoff flight paths.
    • Pilots should be vigilant in calm wind conditions and situations where the vortices could:
      • Remain in the touchdown area.
      • Drift from aircraft operating on a nearby runway.
      • Sink into the takeoff or landing path from a crossing runway.
      • Sink into the traffic pattern from other airport operations.
      • Sink into the flight path of VFR aircraft operating on the hemispheric altitude 500' below.
    • AVOID THE AREA BELOW AND BEHIND THE GENERATING AIRCRAFT, ESPECIALLY AT LOW ALTITUDES, WHERE EVEN A MOMENTARY WAKE ENCOUNTER COULD BE CATASTROPHIC.
    • Vortex Movement Near Ground - No Wind
      Vortex Movement Near Ground - No Wind
    • Vortex Movement Near Ground - with Cross Winds
      Vortex Movement Near Ground - with Cross Winds
Wake Turbulence

Avoidance Procedures

  • Under certain conditions, airport traffic controllers apply procedures for separating IFR (Instrument Flight Rules) aircraft.
  • If a pilot accepts a clearance to follow a preceding aircraft visually, they accept responsibility for ensuring separation and avoiding wake turbulence.
  • The controllers will also provide to VFR aircraft, with whom they are in communication and which, in the tower's opinion, may be adversely affected by wake turbulence from a larger aircraft, the position, altitude, and direction of flight of larger aircraft, followed by the phrase "caution, wake turbulence."
  • After issuing the wake-turbulence caution, airport traffic controllers generally do not provide additional information to the following aircraft unless they know it is overtaking the preceding aircraft.
  • Whether or not given a warning or information, the expectation is that the pilot adjusts aircraft operations and flight path as necessary to preclude serious wake encounters.
    • Do not treat smooth air, the absence of a pilot report, or the absence of an ATC (Air Traffic Control) wake-turbulence advisory as assurance that the flight path is free of wake; continue to identify aircraft ahead and compare their route, altitude, and climb or descent profile with yours.
    • When any doubt exists about maintaining safe separation during an approach, ask the control tower for updates on separation distance and aircraft groundspeed.

  • Landing behind a larger aircraft - same runway:

    • Stay at or above the larger aircraft's final approach flight path, note its touchdown point, and land beyond it.
      • Incident data shows that the most significant potential for a wake vortex incident occurs when a light aircraft is turning from base to final behind a heavy aircraft flying a straight-in approach.
      • Use extreme caution to intercept the final above or well behind the heavier aircraft.
      • When a pilot accepts a visual approach to follow a preceding aircraft, the pilot must establish a safe landing interval behind the instructed aircraft.
      • Pilots must not decrease the separation that existed when the visual approach was issued unless they can remain on or above the flight path of the preceding aircraft.

  • Landing behind a larger aircraft - when a parallel runway is closer than 2,500':

    • Consider the possible drift to your runway.
    • Stay at or above the larger aircraft's final approach flight path- note its touchdown point.

  • Landing behind a larger aircraft - crossing runway:

    • Cross above the larger aircraft's flight path.

  • Landing behind a departing larger aircraft - same runway:

    • Note the larger aircraft's rotation point, and land well before it.

  • Landing behind a departing larger aircraft - crossing runway:

    • Note the larger aircraft's rotation point, and if past the intersection, continue the approach to land before the intersection.
    • If a larger aircraft rotates before the intersection, avoid flight below the larger aircraft's flight path.
    • Abandon the approach unless a landing is ensured well before reaching the intersection.

  • Departing behind a larger aircraft:

    • Note the larger aircraft's rotation point and rotate before it.
    • Continue climbing above the larger aircraft's flightpath, or alter your flightpath upwind until above or clear of the larger aircraft's flightpath.
    • Avoid subsequent headings that will cross below and behind a larger aircraft.
    • Be alert for any critical takeoff situation that could lead to a vortex encounter.

  • Intersection takeoffs - same runway:

    • Be alert to the operations of adjacent larger aircraft, particularly those upwind of your runway.
    • If intersection takeoff clearance is received, avoid subsequent headings that will cross below a larger aircraft's path.

  • Departing or landing after a larger aircraft executing a low approach, missed approach, or touch-and-go landing:

    • Because vortices settle and move laterally near the ground, the vortex hazard may exist along the runway and in your flight path after a larger aircraft has executed a low approach, missed approach, or a touch-and-go landing, particularly in light quartering wind conditions.
    • Ensure that an interval of at least 2 minutes has elapsed before taking off or landing.
      • For a small aircraft departing after one of these operations, ATC requires at least 3 minutes after a B757-size aircraft or 4 minutes after an A380-size aircraft before issuing takeoff clearance.

  • En route VFR (thousand-foot altitude plus 500'):

    • Avoid flying below and behind a large aircraft's path.
    • If a larger aircraft is observed above on the same track, adjust your position laterally, preferably upwind.
    • If a larger aircraft is observed above on the same track (meeting or overtaking), adjust your position laterally, preferably upwind.
  • Guidance on Wake Turbulence:
    • Wake Turbulence Avoidance (1995)

    • Pilot Action to Mitigate Wake Turbulence Encounters:

      • Pilots should be alert for wake turbulence when operating:

        • In the vicinity of aircraft climbing or descending through their altitude.
        • Approximately 10-30 miles after passing 1,000' below opposite-direction traffic.
        • Approximately 10-30 miles behind and 1,000' below same-direction traffic.
      • Pilots encountering or anticipating wake turbulence in DRVSM (Domestic Reduced Vertical Separation Minimum) airspace have the option of requesting a vector, FL (Flight Level) change, or, if capable, a lateral offset.
        • Offsets of approximately a wing span upwind generally can move the aircraft out of the immediate vicinity of another aircraft's wake vortex.
        • In domestic U.S. airspace, pilots must request clearance to fly a lateral offset. Strategic lateral offsets flown in oceanic airspace do not apply.
Wake Turbulence

Warning Signs

  • Wakes may cause uncommanded aircraft movements (i.e., wing rocking).
    • Maintaining situational awareness during approach and landing operations is critical.
    • Ordinary turbulence is not unusual, particularly in the approach phase.
  • A pilot who suspects wake turbulence is affecting their aircraft should get away from the wake, execute a missed approach or go-around, and be prepared for a stronger wake encounter.
  • The onset of wake can be insidious and even surprisingly gentle.
  • Wake vortex encounters can range from light turbulence to loss of control in flight or an in-flight breakup accident.
  • If a wake vortex is encountered on approach, recognize and escape by initiating a go-around, balked landing, or missed approach when appropriate.
  • If the encounter causes an aircraft upset, follow aircraft-specific recovery procedures and use control inputs appropriate to the aircraft's flight condition.
Wake Turbulence

Helicopter Specifics

  • While the behavioral characteristics are similar to a fixed-wing aircraft, circulation is outward, upward, around, and away from the main rotor(s) in all directions.
    • In fact, helicopter wakes may be of significantly greater strength than those from a fixed-wing aircraft of the same weight.
  • Pilots of small aircraft should avoid operating within three rotor diameters of any helicopter in a slow hover taxi or stationary hover.
  • In forward flight, departing or landing helicopters produce a pair of strong, high-speed trailing vortices, similar to those made by fixed-wing aircraft.
    • The strongest wake can occur when the helicopter is operating at lower speeds (20 - 50 knots).
    • Some mid-size or executive-class helicopters produce wake as strong as that of heavier helicopters.
      • Two-blade main rotor systems, typical of lighter helicopters, produce stronger wakes than rotor systems with more blades.
  • Pilots of small aircraft should use caution when operating behind or crossing behind landing and departing helicopters.
Wake Turbulence

Wake Turbulence Responsibilities

  • Pilot Responsibilities:

    • Pilots should remain vigilant for wake turbulence and adjust their flightpaths as necessary, whether or not ATC provides a warning or information.
    • When operating behind any aircraft, pilots acknowledge responsibility for ensuring safe takeoff and landing intervals and providing wake turbulence separation by accepting ATC instructions in the following situations.
      • Traffic information.
      • Instructions to follow an aircraft.
      • The acceptance of a visual approach clearance.
    • ATC will specify the word "super" or "heavy" as appropriate for operations conducted behind super or heavy aircraft when this information is known. Pilots of super or heavy aircraft should always use the word "super" or "heavy" in radio communications.
    • Super, heavy, and large jet aircraft operators should follow the procedures outlined below during an approach to landing. These procedures establish a dependable baseline from which pilots of in-trail, lighter aircraft may reasonably expect to make effective flight path adjustments to avoid serious wake vortex turbulence.
      • Pilots of aircraft that produce strong wake vortices should make every attempt to fly on the established glide-path, not above it; or, if glide-path guidance is not available, to fly as closely as possible to a "3-1" glide-path, not above it.
        • Fly 3,000' at 10 miles from touchdown, 1,500' at 5 miles, 1,200' at 4 miles, and so on to touchdown.
    • Pilots of aircraft that produce strong wake vortices should fly as closely as possible to the approach course centerline or to the extended centerline of the runway of intended landing, as appropriate to conditions.
    • Pilots operating lighter aircraft on visual approaches in-trail to aircraft producing strong wake vortices should use the following procedures to avoid wake turbulence. These procedures apply only to aircraft on visual approaches.
      • Pilots of lighter aircraft should fly on or above the glide path. An ILS may furnish glide-path reference, a visual approach slope system, other ground-based approach slope guidance systems, or other means. In the absence of visible glide-path guidance, pilots may very nearly duplicate a 3-degree glide-slope by adhering to the "3 to 1" glide-path principle.
        • Fly 3,000' at 10 miles from touchdown, 1,500' at 5 miles, 1,200' at 4 miles, and so on to touchdown.
      • If the pilot of the lighter, following aircraft, has visual contact with the preceding heavier aircraft and also with the runway, the pilot may further adjust for possible wake vortex turbulence by following these practices:
        • Pick a point of landing no less than 1,000' from the arrival end of the runway.
        • Establish a line-of-sight to that landing point that is above and in front of the heavier preceding aircraft.
        • When possible, note the point of landing of the heavier preceding aircraft and adjust the point of intended landing as necessary.
          • A puff of smoke may appear at 1,000' markings of the runway, indicating that touchdown occurred at that point; therefore, adjust the point of intended landing to the 1,500' markings.
        • Maintain a line of sight to the point of intended landing above and ahead of the heavier preceding aircraft; maintain it until touchdown.
        • Land beyond the point of landing of the preceding heavier aircraft, ensuring you have adequate runway remaining if conducting a touch-and-go landing, or adequate stopping distance available for a full-stop landing.
      • During visual approaches, pilots may request updates from ATC on separation and ground speed with respect to heavier preceding aircraft, especially when there is any question of maintaining safe separation from wake turbulence.
      • Pilots should notify ATC when they encounter a wake event.
        • Be as descriptive as possible (i.e., bank angle, altitude deviations, intensity and duration of the event, etc.) when reporting the event.
        • ATC will record the event through their reporting system. You are also encouraged to use the Aviation Safety Reporting System (ASRS) to report wake events.
      • Only where the applicable rule permits a pilot-requested waiver may specified wake separation be reduced, and the request must be explicit; some mandatory wake intervals cannot be waived.
        • If doing so, pilots are assuming the risk.
        • Pilots should not waive separation for convenience unless they determine it is safe to do so.

  • Controller Responsibilities:

    • Controllers apply required wake-turbulence separation minima to aircraft operating behind a Super or Heavy, and to Small aircraft operating behind a B757, when the following aircraft is IFR, VFR receiving Class B, Class C, or TRSA services, or VFR being radar sequenced.
    • When in communication with VFR aircraft that, in the tower's opinion, may be adversely affected by wake turbulence from a larger aircraft, airport traffic controllers provide that aircraft's position, altitude, and direction of flight, followed by “CAUTION—WAKE TURBULENCE.”
    • Controllers issue wake-turbulence cautionary advisories, including the position, altitude if known, and direction of flight, to aircraft operating behind an aircraft that requires wake-turbulence separation in these situations:
      • Terminal VFR aircraft that are not being radar vectored and are behind the larger aircraft.
      • Arriving VFR aircraft that were previously radar vectored but are no longer receiving radar vectors.
      • IFR aircraft that accept a visual approach or visual separation.
    • Air traffic controllers should also issue cautionary information to any aircraft if, in their opinion, wake turbulence may adversely affect it.
    • Tower controllers are responsible for runway separation for aircraft arriving or departing the airport.
      • Pilots who accept traffic information, an instruction to follow an aircraft, or a visual approach clearance acknowledge responsibility for ensuring safe landing intervals and wake turbulence separation.
        • ATC applies required wake turbulence separation minima when applicable.
    • Air traffic controllers are responsible for applying the appropriate wake turbulence separation criteria for departing aircraft.
Wake Turbulence

Wake Turbulence Separation

  • Because of the possible effects of wake turbulence, controllers apply no less than the minimum required separation to all aircraft operating behind a "Super" or "Heavy," and to Small aircraft operating behind a B757, when aircraft are IFR; VFR and receiving Class B, Class C, or TRSA airspace services; or VFR and being radar sequenced.
    • Separation is applied to aircraft operating directly behind a super or heavy at the same altitude or less than 1,000 feet below, and to small aircraft operating directly behind a B757 at the same altitude or less than 500 feet below:
      • Heavy behind super: 5 miles.
      • Large behind super: 7 miles.
      • Small behind super: 8 miles.
      • Heavy behind heavy: 3 miles.
      • Small/large behind heavy: 5 miles.
      • Small behind B757: 4 miles.
    • Also, separation, measured at the time the preceding aircraft is over the landing threshold, is provided to small aircraft:
      • Small landing behind heavy - 6 miles.
      • Small landing behind large, non-B757 - 4 miles.
  • Additionally, appropriate time or distance intervals are provided to departing aircraft when the departure will be from the same threshold, a parallel runway separated by less than 2,500 feet with less than 500 feet threshold stagger, or on a crossing runway, and projected flight paths will cross:
    • Three minutes or the appropriate radar separation when taking off will be behind a super aircraft.
    • Two minutes or the appropriate radar separation is required when taking off behind a heavy aircraft.
    • Two minutes or the appropriate radar separation when a small aircraft will take off behind a B757.
    • NOTE: Controllers may not reduce or waive these intervals.
  • A 3-minute interval will be provided when a small aircraft will take off:
    • From an intersection on the same runway (same or opposite direction) behind a departing large aircraft, except a B757; or
    • In the opposite direction on the same runway behind a large-aircraft takeoff or low/missed approach, except a B757.
    • NOTE: This 3-minute interval may be waived upon specific pilot request.
  • A separate 3-minute interval will be provided when a small aircraft will take off from an intersection on the same runway (same or opposite direction) behind a departing B757, or in the opposite direction on the same runway behind a B757 takeoff or low/missed approach. This interval may not be waived.
  • Controllers apply a 4-minute interval for all aircraft taking off behind a super aircraft, and a 3-minute interval for all aircraft taking off behind a heavy aircraft when the operations are as described above, assuming operations are on the same or parallel runways separated by less than 2,500 feet. Controllers may not reduce or waive this interval.
  • Pilots may request additional separation (i.e., 2 minutes instead of 4 or 5 miles) for wake turbulence avoidance. Make the request as soon as practical on ground control and at least before taxiing onto the runway.
  • NOTE: 14 CFR (Code of Federal Regulations) Section 91.3(a) states: "The pilot-in-command of an aircraft is directly responsible for and is the final authority as to the operation of that aircraft."
  • Controllers may anticipate separation and do not need to withhold a takeoff clearance for an aircraft departing behind a large, heavy, or super aircraft if there is reasonable assurance that the required separation will exist when the departing aircraft begins its takeoff roll.
  • Pilots remain responsible for avoiding wake turbulence, while controllers apply required wake-turbulence separation when applicable.
Wake Turbulence

Reduced Vertical Separation Minimum (RVSM) Considerations

  • Wake turbulence can still exist at RVSM altitudes, but will generally be moderate or less in magnitude.
  • Pilots should remain alert when operating:
    • In the vicinity of aircraft climbing or descending through their altitude.
    • Approximately 10-30 miles after passing 1,000' below the opposite direction traffic.
    • Approximately 10-30 miles behind and 1,000' below the same direction traffic.
  • Pilots encountering or anticipating wake turbulence in DRVSM airspace may request a vector, flight-level change, or, if capable, a lateral offset.
  • Before the implementation of DRVSM, the FAA established provisions for pilots to report wake turbulence events in RVSM airspace using the NASA Aviation Safety Reporting System (ASRS).
  • To date, wake turbulence has not been reported as a significant factor in DRVSM operations. European authorities also found that reports of wake turbulence encounters did not increase significantly after RVSM implementation (eight versus seven reports in a ten-month period). In addition, they found that reported wake turbulence was generally similar to moderate clear air turbulence.
  • Report wake turbulence events using the NASA (National Aeronautics and Space Administration) Aviation Safety Reporting System (ASRS) through NASA's reporting page.
Wake Turbulence

Wake Turbulence Lessons & Case Studies

  • National Transportation Safety Board Identification: CEN19LA266:
    • A Challenger 650 climbing through FL335 in smooth air encountered the probable wake of an Airbus A300 flying the same route at FL340 approximately eight to ten miles ahead; the Challenger crew was unaware of the preceding aircraft until after the encounter.
    • The NTSB determines the probable cause(s) of this accident to be: The unexpected wake turbulence encounter while climbing in smooth air to cruise, resulting in passenger injuries. Contributing to the accident was the passenger seat belt sign was off.
  • Some accidents have occurred even though the pilot of the trailing aircraft had carefully noted that the aircraft in front was at a considerably lower altitude. Unfortunately, this does not ensure that the flight path of the lead aircraft will be below that of the trailing aircraft.
  • In 1972, a Delta Air Lines DC-9 crashed during a go-around at Greater Southwest International Airport in Fort Worth after encountering the wake vortex of an American Airlines DC-10 that had just completed a touch-and-go landing. All four occupants were killed.
  • A wake turbulence encounter can range from negligible to catastrophic. Its effect depends on the weight, wingspan, and size of the generating aircraft, the distance from it, and the point of vortex encounter.
  • The probability of induced roll increases when the encountering aircraft's heading is generally aligned with the flight path of the generating aircraft.
  • A typical scenario for a wake encounter is in terminal airspace after accepting clearance for a visual approach behind landing traffic. Pilots must be aware of their position relative to the traffic and use all means of vertical guidance to ensure they do not fly below the flight path of the wake-generating aircraft.
  • National Transportation Safety Board Identification: CEN25LA132:
    • The NTSB determines the probable cause(s) of this accident to be: The failure of the U.S. Army helicopter pilots to yield the right-of-way to the landing airplane, which resulted in the airplane encountering wake turbulence emitted from the three departing U.S. Army helicopters, a subsequent loss of directional control, and a runway excursion.
  • National Transportation Safety Board Identification: WPR25LA041:
    • The NTSB determines the probable cause(s) of this accident to be: The pilot’s failure to maintain clearance from a commercial airliner which resulted in an encounter with wake turbulence and subsequent loss of control resulting in impact with terrain.
  • National Transportation Safety Board Identification: ANC24LA093:
    • The NTSB determines the probable cause(s) of this accident to be: The pilot’s encounter with wake turbulence, which resulted in substantial damage to the airplane.
  • National Transportation Safety Board Identification: WPR24LA187:
    • The NTSB determines the probable cause(s) of this accident to be: The pilot’s failure to maintain clearance from terrain while conducting low-level altitude operations, following an encounter with wake turbulence.
  • National Transportation Safety Board Identification: WPR24LA085:
    • The NTSB determines the probable cause(s) of this accident to be: A loss of airplane control due to wake turbulence resulting from the instructor pilot’s decision to continue the landing into a drifting wake vortex.
  • National Transportation Safety Board Identification: ANC24LA010:
    • The NTSB determines the probable cause(s) of this accident to be: The first pilot’s failure to maintain a stabilized approach, in gusty crosswind conditions, in an environment favoring wake turbulence.
  • National Transportation Safety Board Identification: ERA23LA353:
    • The NTSB determines the probable cause(s) of this accident to be: The pilot’s inadvertent encounter with helicopter wake turbulence during initial climb, which resulted in a loss of airplane control.
  • National Transportation Safety Board Identification: WPR23LA277:
    • The NTSB determines the probable cause(s) of this accident to be: The pilot’s loss of directional control during landing after encountering wake turbulence.
  • National Transportation Safety Board Identification: LAX93LA298:
    • In this 1993 Vacaville accident, a Cessna 172 following a large helicopter on a straight-in approach encountered some turbulence near the threshold, then more severe turbulence during the go-around, lost control, and struck the runway.
    • The NTSB identified the pilot's failure to allow enough time for rotor wash to dissipate as the probable cause and wake turbulence (rotor wash) as a factor.
Wake Turbulence

Wake Turbulence Knowledge Check

Choose the knowledge check that matches your current training for Wake Turbulence.

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PPL knowledge check

Core Knowledge Review

Review foundational knowledge, key concepts, and practical considerations. Topic: Wake Turbulence.

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Wake Turbulence

Wake Turbulence Interactive Scenario

Wake-vortex flow field descending and spreading behind an aircraft.

Behind the Heavy on Runway Two-Seven

Manage a light-aircraft departure and return at a busy airport as heavy jets, crossing runways, wind drift, helicopters, visual separation, and landing geometry move invisible wake hazards. Abbreviations used in this scenario: Aeronautical Information Manual (AIM).

15 DecisionsPrivate PilotWake TurbulenceConsequence-BasedRetry and Debrief
Decision 1
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Scenario Complete

Wake Turbulence

Wake Turbulence Conclusion

  • Aircraft may encounter wake turbulence both in flight and while operating in the airport movement area.
  • A wake turbulence encounter can range from negligible to catastrophic.
  • The impact of the encounter depends on several factors, including the weight, wingspan, and size of the generating aircraft, as well as the distance from the generating aircraft and the point of vortex encounter.
  • Pilots, in all phases of flight, must remain vigilant of possible wake effects created by other aircraft.
    • Studies have shown that atmospheric turbulence hastens wake breakup, while other atmospheric conditions can transport the wake horizontally and vertically.
    • Regardless of whether ATC issues a wake-turbulence warning or information, pilots should adjust aircraft operations and flight paths as necessary to preclude a serious wake encounter.
  • Offsets of approximately a wing span upwind generally can move the aircraft out of the immediate vicinity of another aircraft's wake vortex.
    • In domestic U.S. airspace, pilots must request clearance to fly a lateral offset. Strategic lateral offsets flown in oceanic airspace do not apply.
  • Your most significant hazard from wake turbulence will be induced roll.
    • In rare instances, a wake encounter could cause in-flight structural damage of catastrophic proportions.
  • Pilots should attempt to visualize the vortex trail of aircraft whose projected flight path they may encounter. When possible, pilots of larger aircraft should adjust their flight paths to minimize the exposure of other aircraft to vortices.
    • If unable, or to increase the safety margin, allowing time for the vortex to dissipate reduces risk.
  • When ATC provides separation services, controllers also share responsibility for wake-vortex mitigation through separation standards and cautionary advisories.
  • Recognize that every single aircraft generates wake turbulence.
    • Remember, the effects of wake turbulence will vary based on the big three: heavy, clean, and slow.
  • Terms like super, heavy, and large are in the Pilot/Controller Glossary Term - Aircraft Classes.
  • See also: Aviation Safety Reporting System (ASRS).
Wake Turbulence

Wake Turbulence References