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     was wet and he did not feel decelera- tion. The airplane traveled off the end of the runway, coming to rest upright in a grass area. The pilot stated there were no preimpact mechanical malfunctions with the airplane. Weather at the time of the accident included an 11-knot tail- wind. The NTSB determines the probable cause(s) of this accident to be the pilot’s failure to maintain a proper glidepath and failure to perform a go-around once a safe landing could not be accomplished, which resulted in a landing area over- shoot and runway excursion. There are mitigating factors in each of these accidents, and the numerous others like them that happen all too fre- quently in twin and turbine aircraft. Wet runways. Tailwinds. Low visibility. Excessive speed. Improper or ineffective braking. Regardless of the contributing factors, however, all accidents of this type have one thing in common: The pilot did not command the airplane to land in the appropriate runway touch- down zone. Except in unusual cases, the accepted runway touchdown zone is: • Approximately 1,000 feet from the runway threshold, or • At one-third of the total usable runway length, when that usable length is less than 3,000 feet. On paved runways with an instru- ment approach an “aiming point” may be marked with large white markers if the runway is longer than 900 meters (close to 3,000 feet). On these runways, addi- tional “hash mark” stripes are painted 500 feet before and 500 feet after the aiming point marking, defining the lim- its of the touchdown zone. Regardless of the runway, you should positively identify the touchdown zone when landing. The trick is to land in that zone so that there is sufficient runway remaining to bring the airplane to a stop well within the calculated landing roll distance taking into account environ- mental and runway conditions, properly operating braking systems, and correct pilot technique. This brings two vital, often over- looked points: 1. Required runway length does not equal calculated landing dis- tance. Available runway begins at your touchdown spot, so it’s the dis- tance from that point to the end of the runway that must be compared to calculated landing distance. Generally, this means adding 1,000 feet to the calculated distance to arrive at a minimum runway length, because you’ll overf ly the first 1,000 feet aiming for your touchdown spot. Also, you may land a little beyond your aim point but still be within an acceptable touch- down zone, and if you’re like me, you’ll likely use something less than test-pilot-optimum braking tech- nique once you’re on the ground, so you probably want to pad your ground roll requirement by at least 50 percent. Your minimum accept- able runway length, then, may be: (Calculated ground roll distance x 1.5) + 1,000 feet 2. Deciding whether to go around or to continue a landing attempt can’t happen after you’ve touched down with doubts about remaining runway length. It shouldn’t happen during your landing flare. No, your go-around decision should be made on short final before you begin your flare based on measur- able data that will predict whether you’ll land in your touchdown zone. Even if you’re aimed precisely for ground contact at your aim point, it does younogood–andalotofharm–ifthe airplane is not properly configured for landing and in the proper energy state to safely land and come to a stop. These are the things you can judge before you begin your landing flare. If you are not on speed, in landing configuration, on 36 • TWIN & TURBINE / November 2019 Jet Journal 

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