By Paul Wiley
This article is an overview of what constitutes a “stabilized” approach and provides some guidelines and generally recognized best practices for executing a safe and good stabilized approach in VFR conditions. Most of what is covered here concerns the final approach segment. However, a few words are appropriate regarding the traffic pattern and how a properly flown traffic pattern facilitates a safer final approach.
Please refer to the Airman’s Information Manual (AIM) chapter 4, section 3 (Airport Operations) for details describing traffic patterns and airport operations. Also, Advisory Circular AC 90-66: Non-Towered Airport Flight Operations contains information about traffic patterns, communications and procedures at non-towered airports. Any local procedures specific to the airport where you are flying should always be followed.
A well-flown traffic pattern is entered at the proper point and altitude, distance from the runway and airspeed, and results in the airplane being aligned with the extended runway centerline when on final approach. Communications are as recommended in the AIM. It is recommended that aircraft enter the traffic pattern at pattern altitude, abeam the midpoint of the runway, and normally the entry is on a heading approximately 45 degrees from the downwind heading (calm wind conditions). This is the standard entry and results in your best chance to see and be seen by other traffic in the pattern. Other entries (e.g. straight-in final) are possible, but extra vigilance and clear communication (position reporting) is required to see and avoid other aircraft that may already be in the traffic pattern.
Complete the pre-landing checklist prior to entering the pattern and maintain pattern altitude on the downwind leg until abeam the approach end of the runway. Normally turn base leg when approximately 45 degrees from the approach end of the runway. Base leg is your best chance to see the runway and judge your situation, i.e. are you too high or low, too fast or too slow, too close in to the runway, etc. Normally complete the turn to final about 1 to 2 miles from the runway approach end, but not less than ¼ mile from the approach end of the runway. It is important to note that the AIM states: “A pilot may vary the size of the traffic pattern depending on the aircraft’s performance characteristics.” A common error leading to un-stabilized approaches, especially in high performance airplanes, is flying a pattern that is too small. This reduces the time the pilot has to assess the situation, react and make changes to the aircraft configuration and speed thus making it more difficult to execute a stabilized approach when on final.
On final approach here are the main components of stabilized approach:
- ·In Landing Configuration – this means gear confirmed down and flaps are set appropriately for the conditions. Normally gear was extended prior to pattern entry, checked down on the downwind leg and “double checked” again to be down and locked on final.
- ·On flight path – this means you are on a normal approach angle to the runway, and if the runway has a Visual Glideslope Indicator such as VASI, you are on glide path, i.e. not too high and not too low. Being on flight path at the proper speed normally results in a descent of 500 feet per minute or less.
- ·On airspeed – this means you are flying the recommended final approach speed found in the Approved Flight Manual or aircraft Owner’s Manual. Your speed should be as recommended within a +10/-5 knots tolerance. Note: too fast means too much energy which results in the airplane “floating” down the runway. Being just 10% too fast results in approximately 20% more distance required for landing. Too slow means the safety margin between final approach speed and stall speed is not sufficient. The often referenced 1.3 times power off stall speed means you have a 30% safety margin above the stall speed when flying at this recommended final approach speed.
- ·Aligned with the extended runway centerline – This means that as soon as you roll out of the turn from base leg to final (or shortly thereafter) you have the airplane tracking a course over the extended runway centerline. Depending upon the wind direction and speed the actual heading of the airplane may be different from the magnetic course of the runway. This is known as a “crab” angle and the final approach can be flown in a crab down to a short final; however, the airplane’s longitudinal axis must be aligned with the direction the airplane is traveling prior to touchdown. Another technique is to use a forward slip (always with wing down into the wind) to fly the plane down final approach course and touch down on the upwind main landing wheel first, then allow the downwind wheel to touch down while keeping the longitudinal axis aligned with the direction the plane is traveling using rudder. In a strong crosswind this technique must be used from at least short final to touchdown to control side drift. The crosswind correction, i.e. wing down into the wind, is held using sufficient aileron and rudder coordination throughout the touchdown and roll out. It is recommended that pilots practice crosswind takeoffs and landings with a CFI on a regular basis to maintain proficiency.
- ·Adequately correcting for crosswinds, especially in gusty conditions – whether you choose to use the crab method until just above the runway touchdown and then use rudder to “kick out” and align the longitudinal axis with the flight path, or use the slip to land method with wing down into the wind, sufficient and coordinated control forces must be applied continuously to fly the plane to a safe touchdown and roll out. In gusty crosswinds add 1/2 of the gust factor to final approach speed. For example: the winds are a direct crosswind reported at 10 knots gusting to 20. The steady wind speed (10 knots) is 10 knots different from the peak gust (20 knots). Thus the gust factor is 10 knots and a prudent pilot will increase his final approach speed by 5 knots in this example to provide an increased margin of safety.
- ·Manage distractions when in the traffic pattern (Rule No. 1: FLY the plane)
- ·Always be prepared for a go-around and execute a go-around promptly if not stabilized by 500 feet AGL on final
- ·Practice go-arounds until you are proficient
- ·Use small corrections of pitch and power to stay on flight path and on speed +10/-5 knots
- ·Turn final at least 1/4 mile from the approach end of runway
- ·Coordinated turns are crucial in this phase of flight
- ·In gusty crosswinds add 1/2 of the gust factor to final approach speed
- ·Practice landings with different flap settings (including no flaps)
- ·Get refresher training, e.g. Wings, and practice regularly, especially if rusty
- ·Learn and practice good communications especially at non-towered fields
Factors contributing to an un-stabilized approach:
- ·Too much or too little speed
- ·Improper power management
- ·Flight path too high or too low on final (and not correcting promptly)
- ·Traffic pattern too small, turning on final too close to the runway
- ·Allowing distractions to interfere with safely flying the plane
- ·Not aligning with extended runway centerline on final
- ·Not correcting adequately for crosswind
- ·Overshooting final approach and then overcorrecting with excessive bank and rudder. This is a set-up to a stall/spin accident; and a stall when turning final is unfortunately too common, usually unrecoverable, and all too often fatal.
- ·Excessive speed on final. For any approach, but especially if high and fast on short final, it is safer to go around than to try to salvage a good landing from a bad (unstabilized) approach.
- ·When executing a go-around, avoid retracting the flaps too soon or all at once. The proper procedure for a go-around is: Apply full power, ensure the plane is flying at a safe speed, retract the first increment of flaps, e.g. from 40 degrees to 30 degrees, stop the descent with a small controlled increase in pitch attitude, continue to accelerate to Vx, Best Angle of Climb speed, retract the gear and continue to incrementally retract the flaps, and finally accelerate to Vy, Best Rate of Climb speed and climb straight ahead unless otherwise directed by the tower.
- ·Avoid too much “head down” when in the traffic pattern. Be especially vigilant at non-towered airports where aircraft may be operating without a radio.
- ·Do not allow distractions, including communications with the tower or internally with passengers, to interfere with your first priority: FLY the plane!
- ·Finally, avoid the common error just after touchdown of relaxing controls held on final approach for crosswind.
In summary, flying a stabilized approach is safer and gives you the best chance to make a good and safe round out (flare), touchdown and roll out. Good landings follow good approaches.