Private Pilot Flight Training and Instruction Flight Training Article Library | Back To 4VFR.COM Takeoff Factors Many airports of the U.S. are long enough and wide enough for all G.A. aircraft. Oddly, most are not. When the runway has variations of length, obstacle clearance, surface texture, slope, and density altitude the pilot is called upon to do some combination of artistic and technical figuring. He must figure the foregoing variables into the POH as they apply along with the aircraft weight and balance. He must factor in his pilot skills and knowledge of technique which is, perhaps, the most unknown variable. An airplane can land in considerably less distance than it needs for takeoff. Pilots tend to over-estimate their skills. The POH is required reading. Every takeoff is as unique as every landing. Every takeoff occurs in unique conditions. After landings, takeoffs are the most frequent source of accidents. The minimum safe runway takeoff length should be one and a half times that indicated by the POH. The extra 50% is required to cover pilot optimism. The first warm day of spring gives a completely different takeoff than those you have made all winter. Also, this takeoff will be different from the first 100° takeoff of summer. The hotter it is, the less pitch attitude recommended during acceleration. For standard temperatures you should increase takeoff distances by 25% for each 1000 feet of elevation. Increase POH distances by 10% for every 25 degrees Fahrenheit above standard for any altitude. Every 2500' of increased elevation causes 10 degree standard reduction in temperature. If an airport at 2500' elevation is warmer than 70 degrees you have a density altitude situation. Factors that make a difference have some rules of thumb that a pilot should know and perhaps reference on his lap board. For every 15°F above standard temperature raises density altitude by 1000'. Every 2 knots of tailwind increases takeoff distance by 10%. A firm turf takeoff requires 7% more distance, short grass requires 10% more distance, and soft surface/tall grass requires 25% more distance than recommended by a POH for a macadam runway. By listening on the radio you can get insight into the ATC mind and prepare for such things as "taxi closer and hold, prepare for an immediate", "taxi into position and hold", etc. You must become aware as to what is occurring with other aircraft in the air and on other runways. The mental process required to execute a safe takeoff extend far beyond just moving the aircraft. Consider: 1. Pretakeoff checklist/position Emergency list 2. Clearing the approach area both base and final 3. Configuration and yoke set for wind direction 4. What-if considerations such as power, aborting, emergency, etc. 5. Vso speed for rotation and attitude for Vy climb The POH (Pilot Operations Handbook) has compiled the manufacturer's experience with wind velocity and direction, flap configuration, density altitude, runway surface, and slope to determine the performance capability of the aircraft for a given weight to lift off and overfly the FAA 50' obstacle. The POH has determined the flap requirements, the rotation speed, tire inflation, and the climb speed. If the surface is firm an over-inflated tire is preferred, under inflation can increase required distances by 15%. Many POH charts fail to provide for variables of runway surface, for this we must use 'rules of thumb' that provide safety margins. For grass runways increase lift-off distance by 20%. If the grass is long or damp add 50%. Slope of the runway and wind direction can be compounded by the slope and turn clearance area of the departure path. For specifics you must consult with the locals. Distances can be reduced by 5% for every 100 pounds below gross or POH weights. A 3000' runway becomes very short when temperatures exceed 80 degrees at 3000' elevation In the aircraft POH there is reference data that show how the aircraft will perform under a variety of conditions. One of these conditions is going to be an appropriate fit for most any takeoff you will make. You should make a practice of referencing some of your takeoffs with the information contained in the POH. The more often you do this the least likely will you be a pilot who if found by the NTSB (National Transportation Safety Board) as not understanding takeoff data and responsible for improper decision-caking. The POH will have charts that cover the takeoff influence of weight, power, runway surface, wind and density altitude. Any one of these factors can alone or in combination cause a takeoff accident. The worst thing that can happen to a pilot is to get-away-with-it one time. An overweight aircraft may be pitched too high during the takeoff roll. This pitch limits the ability of the aircraft to accelerate. The perception of attitude improving takeoff from previous flights or even a flight simulator may get you off the ground only to cease flying out of ground effect and stall to the surface. The pitch attitude puts the aircraft behind the power curve. The aircraft may fly off the runway but it will crash because once behind the power curve, you must lower the nose and lose altitude before gaining flying speed. Written by Gene Whitt Flight Training Article Library | Back To 4VFR.COM