A forward slip is a deliberate cross-controlled descent: you lower one wing with aileron and hold opposite rudder, so the nose points off to one side while the airplane keeps tracking straight along its original flight path. The extra drag lets you lose altitude quickly without gaining airspeed, which makes it the tool for an approach that is too high, an airplane without usable flaps, or a power-off landing to a field. It is also a Private Pilot ACS task (Area IV, Task M), and the standard is a touchdown on or within 400 feet beyond a specified point.
Part of our Flight Maneuvers guide. This page is educational and is not a substitute for instruction from a certificated flight instructor or for your airplane’s POH.
What a forward slip does
In a slip the airplane flies partly sideways through the air. The FAA Airplane Flying Handbook (FAA-H-8083-3C) explains the two effects that make that useful: presenting the side of the airplane to the relative wind produces a marked increase in drag, and because the airplane is banked, the vertical component of lift is reduced. Together they let the airplane descend steeply without the airspeed increase you would get from simply lowering the nose. Power is normally at idle, and you control airspeed with the elevator.
The steeper the bank, the steeper the descent. In most light airplanes the limit is rudder travel: once full opposite rudder is needed just to keep the nose from swinging, any more bank would start a turn. The handbook calls this the practical slip limit.
Forward slip vs sideslip
Both slips use crossed controls. What differs is the goal and where the nose points.
| Forward slip | Sideslip | |
|---|---|---|
| Purpose | Steepen the descent without gaining airspeed | Cancel crosswind drift on final and at touchdown |
| Where the nose points | Well off to the side, away from the low wing | Straight along the runway centerline |
| Rudder | Enough opposite rudder to yaw the nose away while the airplane stays on its original path | Just enough opposite rudder to prevent a turn and keep the longitudinal axis aligned |
| Typical use | High on final, no flaps, power-off landings | Crosswind approach, roundout and touchdown |
The two connect on a crosswind landing. The ACS asks you to correlate the crosswind with the direction of the forward slip and, as necessary, transition to a sideslip before touchdown, so the wheels touch with no drift. Our crosswind landings guide covers the sideslip in detail.
When to use a forward slip
- High on final. A slip steepens the approach to your aiming point without building the excess speed that makes an airplane float down the runway.
- Flaps inoperative or not installed. The AFH notes a slip can also reduce airspeed rapidly when flaps are not available.
- Forced landings. After an engine failure you can start a slip faster than you can extend flaps, and you can remove it without penalty if you start getting low. Retracting flaps on an approach, by contrast, can cost unwanted altitude.
- Obstacles. Slips help you clear obstacles on the way into a confined field, which pairs naturally with short-field approaches.
Slips to a landing are also required pre-solo training under 14 CFR 61.87(d)(14).
How to fly a forward slip to a landing
The AFH describes the checkride version this way: plan the descent so a forward slip may be used on final, with the flaps usually retracted, and use it wherever you need to steepen the descent. Step by step:
- Set up. Abeam your landing point on downwind, reduce power to idle and establish your glide. If you are high on downwind or base you can slip there too, but make coordinated turns from leg to leg.
- Lower a wing. With a crosswind, lower the upwind wing. Slipping into the wind makes it easier to stay on the original path; slipping the other way is one of the listed common errors.
- Add opposite rudder. Yaw the nose away from the low wing until the airplane tracks the extended centerline. The nose will point well off to the side.
- Hold airspeed with pitch. Fly the attitude for your normal approach speed. Because of where the pitot tube and static vents sit, some airspeed indicators show considerable error in a slip, so judge it by attitude, the sound of the airflow and the feel of the controls. Our pitot-static system guide explains why.
- Control the descent with bank. More bank steepens the descent and less bank shallows it. Small aileron changes also move you left or right of the centerline while you hold the rudder in.
- Take it out smoothly. Level the wings and release the rudder together while you set the normal glide attitude. Release the rudder abruptly and the nose swings into line and the airplane picks up excess speed. Be out of the slip by the time the roundout begins, then land normally, transitioning to a sideslip if there is a crosswind.
Think of bank as your descent-rate control and rudder as the heading lock. If the nose starts to swing even with full rudder, you have reached the practical slip limit: shallow the bank.
The ACS standard: Task IV.M
Forward Slip to a Landing is Task M of Area of Operation IV in the Private Pilot for Airplane Category ACS (FAA-S-ACS-6C), and it applies to single-engine land and sea applicants. The skill elements ask you to:
- Complete the checklist, make radio calls and plan a path to the landing area that considers altitude, wind, terrain and obstructions.
- Select the most suitable touchdown point and position the airplane on a downwind leg parallel to the landing runway.
- Configure the airplane correctly.
- As necessary, correlate the crosswind with the direction of the forward slip and transition to a sideslip before touchdown.
- Touch down at a proper pitch attitude, on or within 400 feet beyond the specified point, with no side drift and with the longitudinal axis aligned with and over the runway centerline.
- Maintain a ground track aligned with the runway centerline.
The examiner also evaluates risk management, including forward slip operations (fuel flowage, tail stalls with flaps and airspeed control), touching down with the longitudinal axis misaligned, and unstable approaches. Our Private Pilot ACS guide explains how the knowledge, risk management and skill elements fit together.
- Idle power from abeam the touchdown point; flaps usually up
- Low wing into the wind, opposite rudder to hold the centerline
- Airspeed with pitch; trust attitude over a slipping airspeed indicator
- Bank controls the descent; full rudder is the practical limit
- Out of the slip by the roundout; sideslip if there is a crosswind
- Touch down on or within 400 ft beyond the point, no drift, aligned
POH limits: flaps, fuel and airspeed
Slips are not treated the same way in every airplane, so read the limitations and normal procedures in your Pilot’s Operating Handbook before you practice.
- Flaps. The AFH notes that, for aerodynamic reasons, some airplanes have recommendations or limitations on slips with flaps extended, and the ACS lists tail stalls with flaps as a forward slip risk. If your POH restricts slips with flaps, follow it.
- Fuel. Some airplanes limit slips by duration or fuel quantity, because fuel forced to one side of a tank in uncoordinated flight can cause fuel starvation. The AFH adds that in a real engine-out emergency those limits become irrelevant, unless a prolonged slip caused the problem.
- Airspeed and stalls. Expect airspeed indication error, and do not let the speed decay. The AFH notes that a slipping airplane that stalls shows very little of the yawing tendency that turns a skidding stall into a spin, but any stall near the ground is dangerous. Our power-on and power-off stalls guide covers recognition and recovery.
Common errors
The AFH lists these common errors for a forward slip to a landing:
- Incorrect pitch adjustments that result in poor airspeed control.
- Reacting to erroneous airspeed indications.
- Using excess power while trying to lose altitude.
- A slip in the same direction as the crosswind, that is, with the downwind wing low.
- Poor glidepath control.
- Late transition to a sideslip when landing in a crosswind.
- Landing without the longitudinal axis parallel to the runway.
- Landing off the centerline.
Study tools
What you'll need
The FAA handbook and standards behind this maneuver, plus an oral exam guide, all from PilotMall.com.
Frequently asked questions
What is a forward slip in aviation?
A forward slip is a cross-controlled maneuver in which you lower one wing with aileron and apply opposite rudder, so the nose points off to the side while the airplane keeps its original flight path. The added drag and reduced vertical lift let you descend steeply without gaining airspeed.
What is the difference between a forward slip and a sideslip?
Both use aileron one way and rudder the other. In a forward slip the nose is yawed well away from the flight path to increase the descent rate. In a sideslip the longitudinal axis stays aligned with the runway while the low wing points into the crosswind to cancel drift.
Which wing do you lower in a forward slip with a crosswind?
Lower the upwind wing, so the airplane is banked into the crosswind. The Airplane Flying Handbook says slipping into the wind makes it easier to stay on the original flight path, and it lists a slip in the same direction as the crosswind as a common error.
Can you do a forward slip with flaps extended?
It depends on the airplane. The Airplane Flying Handbook notes that some airplanes have recommendations or limitations on slips with flaps extended, and the ACS lists tail stalls with flaps as a forward slip risk. Check the limitations and normal procedures in your POH before slipping with flaps.
What are the ACS standards for a forward slip to a landing?
Under Private Pilot ACS Task IV.M you must touch down at a proper pitch attitude on or within 400 feet beyond the specified point, with no side drift and the longitudinal axis aligned with and over the runway centerline, transitioning to a sideslip before touchdown as necessary in a crosswind.
Why is the airspeed indicator unreliable in a slip?
Because of the location of the pitot tube and static vents, airspeed indicators in some airplanes show considerable error when the airplane is slipping. Fly the attitude for your approach speed and use the sound of the airflow and the feel of the controls as cross-checks.