Updated October 2026
Wake turbulence is the pair of counter-rotating wingtip vortices every airplane leaves behind it while its wing makes lift. The FAA's Aeronautical Information Manual (AIM 7-4) says they are strongest behind an aircraft that is heavy, clean and slow. They sink at several hundred feet per minute, and near the ground they drift sideways at 2 to 3 knots.
That matters more at Van Nuys than at most training fields. Van Nuys is one of the world's busiest general aviation airports, and on a normal day a 100-horsepower Cessna 162 shares two closely spaced parallel runways with business jets, helicopters and air ambulances. The FAA's own Van Nuys page ends its list of local cautions with four words: use caution for wake turbulence. Below: how vortices form and move, how to depart and land behind a jet here, helicopters on the ramp, and what the tower means by "caution wake turbulence".
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What Wake Turbulence Is (Wingtip Vortices, Not Jet Blast)
A wing makes lift with a pressure difference, low above and high below. AIM 7-4-2 explains that this difference makes the air roll up at the back of the wing, and the result is a vortex trailing from each wingtip. Seen from ahead or from behind, the circulation is outward, upward and around each wingtip. Most of the energy sits within a few feet of each vortex core.
The danger is roll. AIM 7-4-3 says the usual hazard is an induced rolling moment that can exceed the roll-control authority of the airplane that flies into it. Fly into a vortex from behind and one wing is pushed up while the other is pushed down, and the roll can be more than full aileron can answer. A short-span airplane has the least to answer with.
Jet blast is something else. It is engine exhaust, and it is a ramp and taxiway hazard behind a jet that is running its engines on the ground. Wake turbulence comes from the wing and exists only once the wing is making lift, from the moment the nose comes up on the takeoff roll to the moment the wheels touch on landing. A Gulfstream taxiing past you makes jet blast and no wake. The same airplane rotating off 16R makes both.
When It Is Worst: Heavy, Clean And Slow
AIM 7-4-3 puts it in capitals: the greatest vortex strength occurs when the generating aircraft is HEAVY, CLEAN and SLOW. Strength depends on weight, speed, wingspan and wing shape.
The logic is short. More weight needs more lift, and more lift makes stronger vortices. At low speed the wing needs a high angle of attack to carry that weight, and the vortices strengthen. Flaps and other devices change the vortex pattern, and with them retracted the wake is at its worst.
Put those together and the worst moments at an airport are the ones a student sees most: a jet just after rotation, and a jet on short final. Both are slow, and both are low over the runways you are about to use.
ATC sorts aircraft into wake classes in the FAA's Pilot/Controller Glossary. Small is 41,000 pounds maximum certificated takeoff weight or less. Large is more than 41,000 up to 300,000 pounds. Heavy is 300,000 pounds or more, and Super is the Airbus A380. A large-cabin business jet sits in the Large class, and a light jet may be Small. Every airplane in our fleet is Small by a wide margin, which is the whole problem.
How Vortices Move: Sink, Drift And Calm-Wind Danger
AIM 7-4-4 describes the behavior, and the whole avoidance strategy follows from it.
- They sink. Vortices descend at several hundred feet per minute, slowing and weakening with time and distance behind the airplane that made them.
- They spread near the ground. Within about 100 to 200 feet of the surface, the two vortices move apart sideways at 2 or 3 knots.
- Wind carries them. A light crosswind of 1 to 5 knots can stop the upwind vortex from drifting away, holding it over the runway in the touchdown zone, while speeding the other one off to the side.
- A tailwind pushes them forward. It can move a previous airplane's vortices up the runway into your touchdown zone. The AIM's words: the light quartering tailwind requires maximum caution.
Calm wind is not the safe case. AIM 7-4-5 tells pilots to be particularly alert in calm conditions, when vortices can remain in the touchdown area. A dead-calm summer evening at Van Nuys, with a jet landing just ahead of you, is the textbook setup.
Now apply the movement to the Van Nuys layout. The long runway, 16R/34L, is the western one, and the short runway, 16L/34R, sits beside it to the east. A light westerly breeze blows the long runway's vortices toward the short one. AIM 7-4-6 says that whenever parallel runways are less than 2,500 feet apart, you should consider vortex drift from the other runway onto yours. The FAA describes the Van Nuys runways as closely spaced parallels, so treat a jet on 16R as if it were on your runway.
Departing Behind A Jet At Van Nuys: Rotate Early, Climb Above Its Path
Jets use 16R/34L, and the Chart Supplement says they must use its full length for departure unless the tower directs otherwise. A jet departing ahead of you therefore starts its takeoff from the end and lifts off somewhere down the long runway. Its wake begins at that rotation point.
AIM 7-4-6 gives the technique in one sentence: note the larger aircraft's rotation point, rotate before it, and keep climbing above its climb path until you turn clear of its wake. Two practical points make that work here:
- Watch where the jet's nose comes up, and pick a taxiway abeam the spot. That is where its wake starts, and you want to be airborne before it.
- Stay above its path, then turn away. A trainer will not out-climb a business jet, but its wake sinks below the jet's path. Climb at your best rate and turn off the jet's track as soon as the departure procedure and the tower allow. On 16L and 16R the noise procedure keeps you straight out over the flood basin before any turn, so plan on the climb, not the turn, to protect you.
Intersection departures are common at Van Nuys, such as 16R at taxiway D. AIM 7-4-6 warns against an intersection takeoff on a heading that crosses below a larger aircraft's path. If you are offered an intersection behind a departing jet and the geometry looks wrong, ask for the full length or for time.
Time is the other tool. ATC applies a 2-minute interval behind a Heavy departure and 3 minutes behind a Super. Business jets are almost never Heavies, and behind a Large jet a VFR trainer may simply hear "caution wake turbulence". You can ask for more. AIM 7-4-9 says pilots may request additional separation, and two minutes on the hold line costs a few dollars of Hobbs time.
Landing Behind A Jet: Stay Above Its Path, Land Beyond Its Touchdown
The landing rule mirrors the departure rule. Behind a larger aircraft landing on the same runway, AIM 7-4-6 says to stay at or above its final approach path, note its touchdown point, and land beyond it. Its wake ends where its wheels touch, so staying above its path and landing beyond that point keeps you out of it.
Behind a larger aircraft that is departing from the runway you are landing on, the rule flips: land well before its rotation point, where it has not yet made a wake.
Van Nuys adds two wrinkles. The 16R PAPI is set at 3.5 degrees, steeper than the usual 3.0. AIM 7-4-8 asks heavy aircraft to fly on the glide path and lighter aircraft on visual approaches to fly on or above it. Following a jet to 16R therefore means a steeper approach than you are used to. Second, the short runway has little room to spare. With the 16L threshold displaced 1,434 feet, the landing distance available on 16L is 2,582 feet. If staying above a jet's path means you would land too long, extend downwind, ask for a delay, or go around. Our guide to the traffic pattern, landings and go-arounds covers how to make that decision early.
One more. The FAA's Van Nuys page warns of aircraft passing overhead on the final approach to Burbank's runway 8, and says Van Nuys tower is not talking to them. The central rule in AIM 7-4-5 is to avoid the area below and behind a wake-generating aircraft. Look up as well as ahead.
| Situation | What To Do |
|---|---|
| Landing behind a larger aircraft, same runway | Stay at or above its approach path; land beyond its touchdown point |
| Landing behind a larger aircraft departing the same runway | Land well before its rotation point |
| Parallel runway less than 2,500 feet away | Expect drift onto your runway; stay at or above its path |
| Departing behind a larger aircraft | Rotate before its rotation point; climb above its path until clear |
| Intersection takeoff | Avoid a heading that crosses below its path |
| After a larger aircraft's low approach, missed approach or touch-and-go | Wait at least 2 minutes before your takeoff or landing |
| En route, VFR | Avoid flying below and behind; shift sideways, preferably upwind |
Helicopter Rotor Wash On The Ramp
Van Nuys has a lot of helicopters: news, law enforcement, air ambulance and training. The Chart Supplement asks helicopters to contact the tower for approach and departure routes, and lists a separate helicopter tower frequency. The FAA's Van Nuys page notes helicopter routes east and west of the runway centerlines at 500 feet AGL.
Two hazards come from them, and AIM 7-4-7 covers both. A helicopter in a slow hover taxi or a stationary hover blows a high-speed outwash that reaches about three times the diameter of its rotor. The AIM tells pilots of small aircraft to avoid operating within that distance. On the ramp that means stopping short and waiting, or asking ground for another route, rather than taxiing past a hovering helicopter. A two-seat trainer with its canopy or door open is the wrong place to find out how strong outwash is.
In forward flight, a helicopter makes trailing vortices of its own, and the AIM says to use caution behind a landing or departing helicopter. When one crosses your final at 500 feet, give its path the same respect you would give a jet's.
What Tower Says And What "Caution Wake Turbulence" Means For You
When a larger aircraft's wake may affect a VFR airplane, AIM 7-4-6 says controllers give its position and direction, then "caution wake turbulence". A typical call to a trainer might be: "Cessna 7030B, runway 16L, cleared for takeoff, caution wake turbulence, departing Gulfstream on the parallel."
Read what it is and is not. It is information. It is not a delay, and it is not ATC taking responsibility. The AIM is explicit that pilots stay responsible for avoiding serious wake encounters, warning or not. Accepting a visual approach, an instruction to follow another aircraft, or traffic information makes wake avoidance your job.
You have three options when you hear it: accept and fly the technique above, ask for time, or decline and wait. "Unable" and "request delay for wake turbulence" are both fine things to say to a Van Nuys controller. Then fly what you asked for. Report any wake encounter to ATC, as AIM 7-4-8 asks, and consider a NASA ASRS report too.
The Redbird MCX full-motion simulator is where we rehearse the decision without the risk, at $120 an hour inside a package.
Related Reading
- Flying out of Van Nuys Airport: the runways, the traffic and the tower.
- Traffic pattern, landings and go-arounds: when to extend, and when to go around.
- Class D airspace, using Van Nuys: the airspace and tower rules above the runways.
- Runway markings, signs and lighting: the 16R and 16L thresholds and declared distances.
- Aerodynamics for student pilots: how a wing makes lift, and why it trails vortices.
Wake Turbulence FAQ
What Causes Wingtip Vortices?
The pressure difference that makes lift, lower above the wing and higher below, rolls the air up at the back of the wing into a vortex at each wingtip. AIM 7-4-2 describes the circulation as outward, upward and around each wingtip, seen from ahead or behind.
When Is Wake Turbulence Worst?
When the generating aircraft is heavy, clean and slow, according to AIM 7-4-3. In practice that is just after rotation and on short final, low over the runways. Calm wind and a light quartering tailwind are the conditions that keep vortices in the touchdown zone longest.
Is Jet Blast The Same As Wake Turbulence?
No. Jet blast is engine exhaust and is a hazard behind a jet on the ground. Wake turbulence comes from the wing and exists only while the wing makes lift, from rotation on takeoff to touchdown on landing.
How Do You Avoid Wake Turbulence When Departing Behind A Jet?
Note where the jet rotates, lift off before that point, and climb above its flight path until you can turn clear of its wake. At Van Nuys jets use the full length of 16R/34L for departure unless the tower directs otherwise, so their wake usually starts well down the runway.
How Long Should You Wait Behind A Jet?
AIM 7-4-6 says to wait at least 2 minutes after a larger aircraft's low approach, missed approach or touch-and-go. ATC applies 2 minutes behind a Heavy departure and 3 behind a Super. Behind other jets you may hear only "caution wake turbulence", and you may always ask for more time.
How Far Should You Stay From A Hovering Helicopter?
AIM 7-4-7 says the outwash from a helicopter in a slow hover taxi or stationary hover reaches about three rotor diameters, and that small aircraft should avoid operating within that distance. On the ramp, stop and wait or ask ground for another route.
Fly The Pattern With The Jets
Wake avoidance is easier to learn by watching a jet rotate off 16R from the hold line than from a diagram. A 60-minute discovery flight is $229 and you fly it from the left seat at Van Nuys. The two-hour beginner flying lesson is $349 in a Cessna 162 or Piper Warrior. Our private pilot course starts at $10,400 with a plan from $2,500 down, and a free consultation with an instructor sets out the lessons and the cost.
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