“Factoring” GA Landing Speeds

The primary pilot challenge (and CFI responsibility) in aviation education is mastering safe take-offs and landings. Smooth, safe landings require understanding and manipulating kinetic and potential energy. Chapter four of the Airplane Flying Handbook (AFM) has a great chart on “correcting energy errors.” SAFE also has an energy management landing page for those still fighting the “pitch/power war.” This is a good starting point for a deeper discussion. Every learner’s confusion and overcontrol could be diminished with more thorough instruction in energy management.

First solo landings are obviously usually just “arrivals.” It is inappropriate to think you have mastered landings at this point. The basics are there, but this barely recognizable maneuver needs to be carefully crafted and improved over time. First solo is only the “paint by numbers” first version. It is essential that both CFI and learner accept the mandate to continuously improve and perfect the landings. Crosswind training is required in 61.93 before cross-country. Short-field accuracy landing is the pinnacle of perfection, and usually not practiced in earnest until just before the flight test. Flying approach below best glide, playing induced drag against power close to the ground, requires precise control that takes time to develop.

Airspeed control is the most important factor in
achieving landing precision. The secret of precise air
speed control begins in the traffic pattern with the
stabilized approach.  FAA “On Landings”

The Secret to Accuracy: “Factoring!”

The secret to a successful landing (often overlooked) is determining the correct airspeed for the final approach.  Counterintuitively, the problem with most approaches is usually *too much* airspeed. The recommended speed to fly from the POH is often a range: “60-70KIAS.”  This number is only accurate for max gross operation at the most adverse CG. This amount of energy will never achieve the precision required for a commercial flight test:

So start with just one precise number, since flying ability will introduce the +/- variability.  Next, adjust (or “factor”) this for the effect of configuration, weight, and wind. (Jets factor for precise take-off too). If you do not factor the speed correctly, you will end up with way too much energy on final approach, round out, and flare. This leads to an uncomfortable float or “planting” the plane before it is ready to land. A good percentage of jet accidents (overruns) result from too much speed (energy) on final approach (see AC 91-79A). We need to teach this concept of a precise final approach airspeed “early and often” (that primacy thing).

Every professional pilot is required to factor their final approach airspeed on every approach for safety. (One of our jets is based at a 3400′ runway). Unfortunately, very few pilots in training (and even CFIs) are capable of executing this very basic calculation. Simply take the square root of the ratio of the current weight over the max gross weight. Multiply this result times the POH (max gross) number for an accurate factored approach speed (Vref). In math terms: √(Takeoff Weight/MGW X POH number.

Larger aircraft above 12.500 pounds have detailed
and very specific information to determine V-ref for all
landing weights as well as other approach speeds at
various flap settings. FAA “On Landings”

You will notice this speed is much slower than most pilots fly their approaches (FAA recommends 1.3X Vso but do this in CAS to be accurate, then translate the result into IAS). Every smartphone calculator can perform either of these calculations quickly. This weight calculation is the same formula for adjusting stall speed and Va for weight (not a coincidence).

A quick rule of thumb is to reduce your approach speed by 1/2 the percentage your airplane is below max gross weight. The plain vanilla 172P short field number is 61KIAS. With two people on board, 20% below max gross, reduce by 6 knots (fly C-152 numbers). Every pilot should be taught to factor final approach speeds by a competent CFI. Fly these numbers (dual first please) and determine your round-out float time (3 seconds is normal and no float for short field). Accurate speed on final eliminates the “float/wallow/plant” sequence most learners (and many certificated pilots) struggle with. We will look at the short field approach and landing next week. Fly safely out there (and often)!

Join us on Nov. 30th, at 8pm for a free SAFE Webinar on the opportunities and challenges of the new MOSAIC rules and the impact this will have on flight training.