9.2.1.1.1 During visual approaches or at uncontrolled airports, including at a part-time controlled airport when the control tower is not in operation, or during charted visual flight procedures (CVFP), pilots are solely responsible for wake turbulence separation and avoidance.
9.2.2 Arrival Following a Landing Aircraft to the Same or Closely Spaced Parallel Runway.
When arriving after a similar or larger-sized aircraft has landed on the same runway, or a closely spaced parallel runway, where conditions exist for wake to drift into their flightpath, pilots are encouraged to delay operations to allow for wake decay and drift, if required. Pilots are encouraged to approach the runway at or above the flightpath of the preceding aircraft and touchdown after the touchdown point of the preceding aircraft. See Figure 26, Landing After a Larger Aircraft.
9.2.2.1 In certain scenarios when parallel approach courses authorized for simultaneous dependent operations, parallel offset approaches, or simultaneous offset instrument approaches (SOIA) are in use, aircraft on both approaches are encouraged to remain on the electronic glidepath, as applicable, for wake vortex encounter mitigation. Refer to the instrument approach chart notes for details.
Figure 26. Landing After a Larger Aircraft
9.2.3 A rrival Behind an Aircraft Landing on a Staggered Threshold. When arriving behind a similar or larger-sized aircraft landing on a closely spaced parallel runway closer than 2,500 feet, where conditions exist for wake to drift into your flightpath, with a staggered threshold, consider the implications of where the wake vortices may be found and avoid that area. Pilots are encouraged to approach the runway at or above the flightpath of the preceding aircraft and touchdown after the touchdown point of the preceding aircraft.
9.2.4 Arrival Behind an Aircraft with a Different Glidepath Angle. Aircraft abeam each other on approaches to nonstaggered parallel runways with the same glidepath angle tend to be at approximately the same altitude. Conversely, on approaches to staggered parallel runways (i.e., one TDZ is more distant) with the same glidepath angle, when aircraft are abeam each other, the aircraft on approach to the more distant TDZ tend to be relatively higher. When following a similar or larger-sized aircraft to a staggered parallel runway, where conditions exist for wake to drift into their flightpath, to the closer TDZ, pilots are
22 encouraged to adjust their flightpath or delay operations accordingly. See Figure 27, Parallel Runways With Threshold Stagger.
Figure 27. Parallel Runways With Threshold Stagger
9.2.5 Arriva l Following a Departing Aircraft from the Same or Closely Spaced Parallel Runway. When arriving after a similar or larger-sized aircraft has departed on the same or closely spaced parallel runway, where conditions exist for wake to drift into their flightpath, pilots are encouraged to touchdown prior to the rotation point of the larger aircraft. See Figure 28, Landing After a Departing Aircraft.
Figure 28. Landing After a Departing Aircraft
9.2.6 A rrival Following a Departure from a Crossing Runway. When arriving after a similar or larger-sized aircraft has departed from a crossing runway, pilots are encouraged to take note of the takeoff rotation point of the preceding aircraft, the possible wake vortex drift, as well as the departure flightpath. Pilots are encouraged to avoid a flightpath that crosses below and behind the flightpath of the preceding aircraft. If the preceding aircraft rotates prior to the intersection, pilots are encouraged to execute a missed approach or go-around unless a landing is ensured well before the intersection. See Figure 29, Landing After a Crossing Runway Departure (Rotation Point Before Intersection), and Figure 30, Landing After a Crossing Runway Departure (Rotation Point After Intersection).
23 Figure 29. Landing After a Crossing Runway Departure (Rotation Point Before Intersection)
Figu re 30. Landing After a Crossing Runway Departure (Rotation Point After Intersection)
9.2.7 Arriv al Following an Aircraft Landing from a Converging Runway. Converging runways have various layouts and hazards. When arriving after a similar or larger-sized aircraft has landed on a converging runway, pilots are encouraged to take note of the point of touchdown of the preceding aircraft, the possible wake vortex drift, and the approach path. Pilots are encouraged to avoid a flightpath that crosses below and behind the
24 preceding aircraft. See Figure 31, Landing After an Arriving Aircraft on a Converging Runway.
Figure 31. Landing After an Arriving Aircraft on a Converging Runway
9.2.8 A rrival Following a Landing on the Opposite End of the Runway. When arriving after a similar or larger-sized aircraft has taken off from the opposite end of the same or closely spaced runway, where conditions exist for wake to drift into their flightpath, pilots are encouraged to delay operations to allow for wake decay and drift away from the approach area and the possible missed approach flightpath.
9.2.9 Arrival Following an Aircraft that Performs a Go-Around. When arriving after a similar or larger-sized aircraft performs a missed approach, low approach, go-around, balked landing, or touch and go, the wake vortex hazard may exist along the runway and in your flightpath, including the possible missed approach course.
9.2.10 Arrival to an Adjacent Airport. When arriving at an airport adjacent to another airport with similar or larger-sized aircraft operations, pilots are encouraged to take care to avoid wake vortices from arriving and departing aircraft. See Figure 32, Arrival at an Adjacent Airport.
25 Figure 32. Arrival at an Adjacent Airport
9.2.11 Arriv al Following Rotorcraft Operations. The effects of rotorcraft wake vortices, downwash, and outwash may be stronger than expected compared to fixed-wing aircraft of a similar size. Pilots of fixed-wing aircraft are encouraged to:
1. Regard rotorcraft of a similar size as a larger aircraft for wake vortex avoidance.
2. Avoid the area within three times the rotor diameter, of the nearest main rotor, of a rotorcraft in a hover or slow hover taxi.
3. Avoid wake vortices from an arriving or departing rotorcraft that may be present in different locations than the expected location of wake vortices from fixed-wing aircraft.
9.3 En Route.
9.3.1 En Route Wake Encounter Scenarios.
9.3.1.1 Pilots are encouraged to be alert for wake vortices when operating behind and in the vicinity of aircraft climbing or descending through their altitude.
9.3.1.2 When VFR en route with 500-foot separation from IFR traffic, pilots are encouraged to avoid flight below and behind the flightpath of a similar or larger-sized aircraft. If a preceding aircraft is observed above on nearly the same path, whether opposing or overtaking, pilots are encouraged to adjust the flightpath of the aircraft laterally, preferably upwind.
9.3.1.3 When IFR en route with 1,000-foot separation from other IFR traffic, pilots are encouraged to be alert for wake vortices when approximately 5 to 25 miles after passing 1,000 feet below opposite-direction traffic or behind same-direction traffic.
9.3.2 En Route Wake Vortex Encounter Mitigations. If the hazard of wake vortex encounter is suspected, especially in the case of a generating aircraft defined as a category of “Heavy” or “Super,” pilots are encouraged to request a lateral offset upwind of the expected wake vortices. Lateral offsets upwind as small as the wingspan of the preceding aircraft may
26 move the trailing aircraft out of the immediate vicinity of a wake vortex. See Figure 33, Opposing Flightpaths.
Figure 33. Opposing Flightpaths
9.3.2.1 Strategic Lateral Offset Procedure (SLOP) may be utilized where allowed by International Civil Aviation Organization (ICAO) Doc 4444, Procedures for Air Navigation Service (PANS), and national Aeronautical Information Publications (AIP) (i.e., oceanic airspace) to offset from an airway, preferably upwind. SLOP does not apply to domestic U.S. airspace. In domestic U.S.
airspace, pilots are encouraged to request an amended clearance to fly a lateral offset, preferably upwind, as applicable. See Figure 34, In-Trail Flightpath.
Figure 34. In-Trail Flightpath
9.3.2.2 Condensation trails, known as contrails, and wake vortices propagate, descend, and decay in the atmosphere differently. The ice particles that form in the exhaust of aircraft flying at high altitude are only to be used as a gross indication of the flightpath of a preceding aircraft, not the specific wake vortex location.
9.4 Wake Vortex Encounter Mitigations for Generating Aircraft.
9.4.1 Vertical Course. Large aircraft operators are encouraged to make every attempt to fly their aircraft predictably. In the terminal environment, this includes flying on the glidepath, not above it. Flying the glidepath where appropriate establishes a baseline from
27 which pilots of in-trail aircraft may make effective flightpath adjustments to mitigate wake vortex encounters. At airports without visual or electronic glidepath indications, or both, pilots are encouraged to use a 3-degree glidepath using the “3 to 1” glidepath guidance. For every NM away from the runway, the pilot is encouraged to be an additional 300 feet above the TDZE (e.g., 1,500 feet above TDZE at 5 NM). Exceptions exist where a 3-degree glidepath is too low, including operations near mountainous terrain.
9.4.2 Lateral Course. Larger aircraft operators are encouraged to remain as close to as feasible the centerline of an airway and to fly as closely as possible to the approach centerline or the extended runway centerline. Flying the lateral course predictably allows pilots of in-trail aircraft to make effective flightpath adjustments to mitigate wake vortex encounters.
9.4.3 Radio Phraseology. Pilots of “Heavy” or “Super” wake turbulence category aircraft are encouraged to use the appropriately designated weight identifying term in radio communication.
9.5 Wake Vortex Encounter Mitigations Utilized by ATC.
9.5.1 Wake Vortex Encounter Mitigation Roles and Responsibilities. In accordance with 14 CFR § 91.3(a), the PIC of an aircraft is directly responsible for, and is the final authority as to, the operation of that aircraft. This responsibility includes wake vortex encounter avoidance and mitigation. Pilots arriving and departing from uncontrolled airports, or accepting a clearance for a visual approach, operating using VFR outside of controlled airspace are accepting the responsibility for wake vortex encounter avoidance and mitigation. Per Order JO 7110.65, when ATC is providing separation services, the controller shares in this responsibility. ATC mitigates wake vortex encounter risk through minimum separation standards between leader aircraft and follower aircraft, as well as information reports to pilots such as wake turbulence cautionary advisories.
9.5.2 Wake Assessment. Wake assessment performed by the FAA defines the characteristics of an aircraft wake vortices, including the initial wake strength and the wake age required to reduce the residual wake strength encountered by a following aircraft. Wake assessment also quantifies the ability of a following aircraft to encounter wake vortices.
9.5.3 Wake Categorization. Wake assessments result in wake categorization of an aircraft to define separation standards in time or distance between leader and follower aircraft pairs to be used by ATC. For example, on an approach, ATC may separate a “Heavy” category follower aircraft behind another “Heavy” category leader aircraft by the Minimum Radar Separation (MRS). If, instead, the follower aircraft was a “Light” category aircraft behind a “Heavy” category aircraft, the controller would increase the separation allowing for the wake vortices to decay and move away from the flightpath. Originally, wake categorization and minimum separation standards were based on the maximum gross takeoff weight of an aircraft. In this weight-only wake categorization of aircraft there is potential for aircraft with similar weights to have markedly different wake generation and behavior characteristics, as well as differing abilities to encounter wake as a following
28 aircraft. Weight-only categorization, therefore, carries heightened safety risks or less efficient use of congested airspace. Advances in the understanding of wake behavior and computational simulations facilitated the development of Wake Turbulence Recategorization (RECAT). RECAT offered a multiparameter aircraft classification system that enhanced safety over the weight-only structure while yielding operational efficiency gains. RECAT was modified into different versions including RECAT 1.5 and RECAT II. Now, Consolidated Wake Turbulence (CWT) takes advantage of the continuing evolution of wake mitigation strategies to consolidate the benefits of previous RECAT efforts. ATC facilities are currently transitioning to CWT separation standards.
9.5.3.1 CWT categorizes aircraft into nine separate categories, labeled A through I.
“A” is the category designator for a “Super” (e.g., Airbus A380), and “I” is the category designator for a smaller aircraft (e.g., Beechcraft King Air 200).
9.5.3.2 ICAO Wake Turbulence Category (WTC) is based on weight only. The designators are “L” for “Light” category aircraft with a maximum certificated takeoff weight of 15,400 pounds or less. “M” for “Medium” category aircraft with a maximum certificated takeoff weight of more than 15,400 pounds to 300,000 pounds. “H” for “Heavy” category aircraft with a maximum certificated takeoff weight of more than 300,000 pounds. There is also a designator “J”, which denotes a “Super” category aircraft type
(e.g., Airbus A380).
9.5.4 Flight Plan. An ICAO compliant flight plan such as FAA Form 7233-4, Pre-Flight Pilot Checklist and International Flight Plan, requires the input of an aircraft type designator of an aircraft as well as the ICAO WTC in Item 9 of FAA Form 7233-4. The aircraft type designators, ICAO WTCs, and the corresponding CWT category for an aircraft type can be found in the current version of Order JO 7360.1.
9.5.4.1 Automation in the ATC system automatically adjusts the wake separation category if the aircraft flight plan is filed correctly with the aircraft type designator found in Order JO 7360.1.
9.5.4.2 It is important that the standard abbreviation for an aircraft type designator is listed correctly in the flight plan. ATC automation systems will not present the correct information to the controller unless the current and proper aircraft type is listed in the flight plan. For example, an Eclipse 550 jet is listed as an EA50; if the operator listed E550, the automation system would recognize the aircraft as an Embraer Legacy that is in a different CWT category.
9.5.4.3 Operators of aircraft without an assigned aircraft type designator are to enter “ZZZZ” as the aircraft type designator in their flight plan. If an operator, or controller, enters a “ZZZZ” designator into the flight plan, or the aircraft type designator entered has not been assessed for wake separation standards, the ATC automation presents the controller with a no weight (NOWGT) classification. The NOWGT classification is better described as “no wake
29 assessment.” NOWGT aircraft are given added separation that may affect the efficiency of airspace use both in front of and behind the NOWGT aircraft.
9.5.5 Wake Turbulence Cautionary Advisories. Wake turbulence cautionary advisories are issued when, in the opinion of the controller, wake turbulence may have an adverse effect on traffic. When traffic is known to be a “Super” or “Heavy” category aircraft, ATC will include the word “Super” or “Heavy” in the description. ATC issues wake turbulence cautionary advisories that include the position, altitude (if known), direction of flight, and the phrase “Caution, Wake Turbulence” to aircraft operating behind an aircraft that requires wake turbulence separation. Wake turbulence cautionary advisories are issued to VFR aircraft not being radar vectored that are behind the larger aircraft, VFR arriving aircraft that have previously been radar vectored and the vectoring has been discontinued, and IFR aircraft accepting a visual approach or visual separation.
Note: Whether or not a warning or information has been given, the pilot is encouraged to adjust aircraft operations and flightpath as necessary to preclude wake vortex encounters.
9.5.6 ATC Inquiry. When any doubt exists about maintaining safe separation distances between aircraft to avoid wake turbulence, pilots are encouraged to ask ATC for updates on separation distance, groundspeed, and altitude.
10 WAKE VORTEX ENCOUNTER RECOVERY GUIDANCE. A wake vortex encounter does not always result in an unsafe condition. Depending on many variables discussed in this AC, a severe wake vortex encounter may include an undesired aircraft state, aircraft upset, or possibly a LOC-I aircraft accident. Incident and accident history has found that pilot inputs during a wake vortex encounter may have a positive or a negative effect. Refer to the Aircraft Flight Manual (AFM) or company policies, or both, for aircraft-specific upset recovery procedures.
10.1 Situational Awareness. The goal of situational awareness, as it relates to wake vortices, is avoidance. Furthermore, if a pilot is situationally aware and yet experiences a wake vortex encounter, the goal is to mitigate the encounter by recognizing and escaping
(e.g., initiating a go-around/balked landing/missed approach when encountering a wake vortex on approach). If an aircraft encounters a severe wake vortex that causes an undesired aircraft state or aircraft upset, the goal of situational awareness is to understand the aircraft state in relation to the AOA, the load factor, the horizon, and energy state, including kinetic energy, potential energy, and chemical energy, so that the pilot will make the correct inputs to recover effectively. Understanding the situation that an aircraft is in is crucial for effectively initiating recovery procedures. A pilot who is aware of the energy state and flightpath of the aircraft is less likely to be startled and, therefore, more likely to deal with a wake vortex encounter with the proper control inputs versus rapid reactive responses and reversals. The larger the excursion from normal flight, the more challenging an upset recovery becomes. Attitude instruments may be unreliable depending on the capabilities of the attitude instrument and the amount of roll and pitch experienced in the aircraft upset. Pilots are encouraged to use all available resources, including looking outside the flight deck windows, including side windows for extreme
30 pitch angles, for attitude information. Failing to reference external cues or inadequately cross-checking instruments (e.g., neglecting to monitor all the instruments or fixating on certain instrument indications and not detecting changes in others) may exacerbate an aircraft upset. Regaining and then maintaining control of the aircraft is paramount.
10.2 Startle and Surprise. The expectations of an unprepared pilot may be violated when exposed to a sudden, intense event that may happen in a wake vortex encounter and may produce a startle effect (e.g., automatic muscle reflex, raised heart rate, cognitive impairment, etc.). A surprise that violates a pilot’s expectations can affect the mental processes used to respond to the event. Startle and surprise may cause the pilot to input inappropriate controls that overshoot the desired response. An inappropriate response to a wake vortex encounter that leads to an aircraft upset may lead to another aircraft upset in a different direction or axis. A pilot who is aware of the energy state and flightpath is less likely to be startled and, therefore, more likely to deal with the situation with controlled inputs versus reactive responses.
10.3 Flight Control Inputs. Control inputs that are appropriate at one point in the flight envelope might not be appropriate in another part of the flight envelope. Pilots are encouraged to have a fundamental understanding of flight dynamics to correctly determine the control inputs necessary for recovery. Aircraft upsets caused by a wake vortex encounter may involve a rapid roll reversal as the aircraft transitions across one wake vortex that induces a roll in one direction and then enters the other wake vortex that induces a roll in the opposite direction. Pilots are encouraged to exercise caution with control inputs and ensure that control input is proportional to the situation, including the flight envelope, unless ground contact is imminent. It may be advisable, and if conditions permit, to allow the aircraft to transition through the wake vortex and then recover from any resultant undesired aircraft state versus aggressively trying to control the aircraft during the wake encounter. A pilot-induced oscillation (PIO) may occur when a pilot’s commands become out of phase with the aircraft motion. A PIO may be initiated during an upset recovery if a pilot reacts with large rapid inputs before determining what is occurring. Precedents exist for wake vortex encounter events in which the pilot inputs exacerbated the undesired aircraft state caused by the wake vortex encounter.
10.3.1 Pitch. Aircraft upset may lead to an aircraft at or close to the critical AOA and stall. An airplane wing may stall in any attitude and at any airspeed. The elevator controls the load factor of the aircraft. “Load factor” is the measure of the acceleration being experienced by the aircraft also known as “G” loading. Higher load factors increase the AOA and reduce flight control effectiveness compared to an aircraft at 1G or less than 1G. Zero or negative G’s may have detrimental effects on the aircraft and occupants within. A priority in recovery from an aircraft upset is to manage the AOA and load factor to recover from or prevent a stall and return the aircraft to a desired aircraft state without overstressing the aircraft. Pilots are encouraged to manage the load factor to recover from an upset effectively without stalling or overstressing the aircraft. The use of actions affecting pitch
(e.g., elevator input, pitch trim activation) may aggravate the upset situation or may result in high structural loads.
10.3.2 Roll. An increasing bank results in a reorientation of the lift vector from the vertical, which, in turn, creates a horizontal lift component and a reduced vertical lift component.
When combined with an increased pitch input, an increase in the bank creates an increased load factor. At any speed, large aggressive control deflection reversals may lead to a load factor that exceeds structural design limits.
10.3.3 Yaw. A yaw input is not the preferred initial response to a wake vortex encounter. Pilots are encouraged to use yaw input in combination with roll inputs to eliminate sideslip, not to create sideslip or counter wake-induced roll. Prior experience and training that emphasized the use of yaw input to maneuver in roll may not apply to all aircraft operations. Using yaw to counter roll rate during a roll upset may lead to an undesirable aircraft response. Pilot overreaction in yaw may induce abrupt yawing moments and violent out-of-phase roll rates, which may lead to successive cyclic rudder deflections, known as rudder reversals, as the pilot tries to control the resulting motions. In past aircraft accidents, it was determined that the accident was the result of the in-flight separation of the vertical stabilizer and subsequent loss of control due to excessive rudder pedal inputs in response to a wake vortex encounter.
10.3.4 Thrust. Increased chemical energy (i.e., increased thrust) may be used to increase kinetic energy, increase potential energy, or both. Some aircraft produce a thrust vector that is not coincident with the longitudinal axis of the aircraft and may produce a pitch up or down movement that may not be desired. Propeller-driven aircraft have a faster thrust buildup compared to jet engines that have a longer spool-up time. Propeller effects, however, may introduce rolling moments and unwanted slip or skid in response to power changes that require pilot compensation.
10.3.5 Lift or Drag Devices. The aircraft’s energy state and trend need to be assessed prior to the deployment or retraction of lift or drag, or both, devices (e.g., flaps, slats, spoilers/speedbrakes).
10.3.6 Autoflight System. Refer to the AFM for specific guidance on the autoflight system, including autothrust systems and yaw damper controls. During a wake vortex encounter, if conditions permit, the autoflight system is engaged and remains engaged, and the aircraft is not in an undesired state, it may be appropriate to allow the autoflight system to fly the transition through the wake vortex, rather than aggressively trying to manually control the aircraft during the wake encounter. An autoflight system may disconnect unexpectedly because of excessive roll or pitch rates, roll or pitch angles, control surface deflection rates, or forces that are not normal. Approaching the limits of an autoflight system may mask the actual airplane trim state, as well as resultant changes in performance and handling qualities. Pilots are encouraged to be prepared to assume manual control of the aircraft if the autoflight system disconnects or if the aircraft attains an undesired state or upset. If the aircraft progresses into an upset, in coordination with AFM procedures, a pilot is encouraged to disconnect the autoflight systems, including the autothrust to recover.
10.4 Other Upset Recovery Considerations. The routine and/or mandatory use of autoflight systems during high-altitude operations often results in pilots having less experience with
32 manual flight control in this environment. However, if a wake vortex is encountered at high altitude, pilots generally have more time to recover due to the greater altitude available. In such scenarios, methodical and deliberate flight control inputs are crucial, as opposed to hasty or arbitrary reactions. In situations such as low-altitude operations, depending on the severity of the wake encounter, the time allowance is shortened for the pilot to recognize the encounter, identify the resultant forces, and make an effective recovery. Proper situational awareness is paramount to upset recovery. When an encountering aircraft transits a wake vortex low to the ground (i.e., low potential energy), relatively slow (i.e., low kinetic energy), and at a higher AOA than would occur during takeoff or landing, the situation may be critical. Prevention and avoidance of wake vortices is always the goal, but if the pilot recognizes that their aircraft is beginning to encounter wake vortices, evasive actions are to be enacted to prevent aircraft upset.
11 PILOT WAKE VORTEX ENCOUNTER REPORTING. Wake vortex encounter reporting is an important aspect of ensuring current aircraft wake separation standards and guidance are effective. Only a pilot knows that they have had a wake vortex encounter. If a pilot believes they have had a wake vortex encounter, they are encouraged to report the event. When reporting, pilots are encouraged to be as specific as possible, including details such as location, altitude, aircraft configuration, phase of flight, roll rate, maximum bank angle, changes to altitude and airspeed, etc.
11.1 Reporting to ATC. When in contact with ATC, pilots are encouraged to report all suspected wake vortex encounters as soon as practical to ATC. When uncontrolled by ATC, pilots may call ATC by radio or telephone to report a wake vortex encounter.
When reporting a wake vortex encounter, pilots are encouraged to take care to distinguish between a wake vortex encounter and atmospheric turbulence. Pilot reports of aircraft wake vortex encounters received through ATC are recorded as a Mandatory Occurrence Report (MOR) per FAA Order JO 7210.632, Air Traffic Organization (ATO) Occurrence Reporting.
11.2 Aviation Safety Reporting System (ASRS). Pilots are encouraged to utilize the National Aeronautics and Space Administration (NASA) ASRS to report wake vortex encounters.
A pilot may file ASRS reports by visiting the NASA Ames Research Center website at https://asrs.arc.nasa.gov/.
11.2.1 Data Anonymity. Pilot reports of wake vortex encounters through the NASA ASRS system are de-identified. All personal and organizational names are removed. Dates, times, and related information, which could be used to infer an identity, are either generalized or eliminated. As a part of the NASA Ames research system, quarterly reports of wake vortex encounters are supplied to the FAA. These reports document event dynamics and contributing factors underlying each reported wake vortex encounter. A sampling of the factors to be analyzed include the assessed magnitude of the wake encounter, aircraft spacing, aircraft type, runway configuration, and consequences of the encounter.