Page 36 - Volume 16 Number 10

will generally be 1.3 times VSO adjusted for the airplane’s weight (the bottom of the white arc at maximum gross weight, less at lower weights) or VMC + 5 knots calibrated airspeed, whichever is higher. Take a look: It’s probably a lot slower airspeed than you’d expect. If you don’t have a clear recommendation in your POH/AFM, do the math for your airplane’s landing weight and fly your approach at 1.3 VSO or VMC + 5, as adjusted for weight.To get the handbook-predicted landing performance, you need to fly at the recommended speed. I’ve done some calculations of energy dissipation with a number of types of light twins and estimate that, as a rule of thumb, each additional five knots of airspeed at the beginning of the flare results in a 10% increase in distance to land over a 50-foot obstacle. So, although you might add a few knots for landing in gusty wind conditions (one-half the gust factor, so generally no more than five to, at the very most, ten knots), coming in “just a little hot” under any conditions can be a major factor in runway overruns.Committed to LandWe aero-educators often throw out the term “committed to land” when presenting the appropriate time to extend full flaps or abandon the relative safety of blue line and reduce to final approach speed. Being “committed to land,” however, is a misnomer. With the probable exceptions of coming in on one engine or into some unusual airport with extreme obstacles off the far end of the runway, there’s always the option of going around to try again or divert to a more suitable airport. Saying you’re committed to land suggests the go-around option no longer exists.However, avoiding a runway overrun is the combination of two factors: proper airspeed, and proper glide path control to arrive at the intended touchdown zone (usually 1,000 feet from the threshold or one-third the total runway distance, whichever is less). If you’re not on speed and on glide path when you cross the runway34 • TWIN & TURBINEthreshold, it’s probably too late to correct both before you land. Not on speed and on glide path when the runway comes under the wheels? Power up, accelerate carefully to blue line or above, and climb away. Float past the end of the touchdown zone before the airplane is firmly on the ground? Go around. Use the term “on targets to land” instead of “committed” to landing, and you’ll be less likely to fall into this human factors trap.The NTSB report for the mishap example at the beginning of this article does not go into any more detail as to the “why” of the mishap. Given the enormous workload of the very few Air Safety Investigators in NTSB, when there are no serious injuries or fatalities, the investigations rarely do. But, we can infer a couple of things from this sort of narrative, not to assess blame or point fingers, but so that we may learn something that makes us all better pilots.When the pilot found himself high on short final he“reduced the engine power and lowered the nose.” Thedegree to which he lowered the nose, and the airspeed hewas at before doing so, would have a tremendous effect onhis glide path runway distance required to land. His laterstatement that “the airplane floated much farther thanhe expected during landing” appears to confirm that theresult was a speed much faster than that recommendedfor landing. With energy being related to the square ofspeed, being even “a little fast” in the flare will result ina much greater distance traveled before touchdown—what we sometimes call “floating.” Avoid one of the mostand maintaining—the appropriate speed for landing. T&T •common causes of multiengine airplanes by choosing—Thomas P. Turner is an ATP/CFII/MEI, holds a Masters Degree in Aviation Safety, and was the 2010 National FAA Safety Team Representative of the Year. Subscribe to Tom’s free FLYING LESSONS Weekly e-newsletter at www.mastery-flight-training.com.OCTOBER 2012