The Lightplane and the Soft, Short Field Take-Off

smooth day, and a little patience, es- tablish a rate of climb curve of your own. Just measure your rate of climb at different airspeeds, jot them down and draw a ...
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(EDITOR'S NOTE: Dave Kerzie graduated with an A.E. degree from the University of Washington (1958), and, at present, is a USAF KC-135 aircraft commander currently flying missions in support of the South East Asia conflict. He enjoys lightplane instructing at the Aero Club for relaxation. Also has a Stits Playboy about 80 percent complete.

Keeps busy between this and a wonderful wife and six fine young sons. ANY OF YOU lightplane pilots and homebuilders read or M should read reports, articles, or bul-

letins on aircraft accidents. Almost everyone of these reports has some mention of a lightplane pilot running out of runway or crashing into some obstacle at the end of the airport. The majority of these misfor-

tunes could have been avoided if the pilot had been better informed on the "whys and what fors" of aircraft take-off performance and take-off techniques associated with soft or short fields and obstacle clearance. Let's sit down together and try to ferret out some of the problems and extend our aeronautical knowledge along this line. Doubts in mind have no place while sitting at the end of a runway with throttle in hand. Soft Field Take-Off

Every pilot should know that a

muddy runway, tall grass, or weeds will extend your ground roll. How much is anybody's guess. Even the big boys with the thick tech orders

and performance handbooks are vague when it comes to relating extended ground run with slush, water, etc. on the runway. If in doubt, wait until the surface drys out or

"THE LIGHTPLANE AND THE SOFT, SHORT FIELD TAKE-OFF By David A. Kerzie EAA 9481 238 East Idaho, Rapid City, S. D. the grass is mowed. You say you have to go? Then try to determine a safe "Go-no Go" point on the runway where, in your mind, an abort can be accomplished in the remaining runway provided the bird is not accelerating properly. Take-off technique here is important. Select the flap setting on your aircraft recommended by the handbook for soft field take-offs. As most homebuilts today are not equipped with flaps, this breed of pilot does not have this decision to be concerned with. Taxi out so that you line up with all of the runway ahead of you. It has been pointed out many times before that the most useless items while flying airplanes are runways behind you and altitude above you. The main thing during a lightplane soft field take off is to get the lift on your wings

and weight off your wheels as soon as possible. Use more than normal back pressure during your roll for

lightplane tricycle gear types to raise your nose wheel off. Lift the airplane off the ground safely but as soon as possible then gently re-establish an attitude to get flying speed. On a Cessna 150, for example, the aircraft can be lifted off with the stall warning horn beep-

ing all the way and once airborne the aircraft attitude is changed to accelerate the desired flap retrac-


tion and climb-out speeds. This acceleration, after a little practice, can be accomplished six inches to a fool off the ground. Remember that you are in a slow flight condition throughout the whole maneuver and. to say the least, smooth aircraft control is paramount. The tailwheel aircraft (don't like the term conventional gear as now days tri-gear seems to be the conventional design) procedure is much the same except you raise the tailwheel off the surface as soon as possible. Try to perfect these techniques on a paved strip with ideal conditions first and work into it gradually. Handle with care as you are flying at the lower airspeed limits of the aircraft. Short Field Take-Off

Running out of runway is the only problem with a short field. Once read about a bloke who loaded a deer in the back of his airplane and tried to take off from a mountain strip in the middle of a hot afternoon. He made like the world's fastest tricycle, needless to say, and coasted off the end. A review of aircraft performance factors here may be a help. You might recall the old basic equation, L = CL y2 PV2 s which states that lift is proportional to some coefficient multiplied by the air density, square of the velocity, and wing surface area. Important here is P or the air density. This air density decreases with rise in temperature and pressure altitude. The hotter the day or the higher the elevation, the longer the take-off roll. So you

have a hot day at a mountain airport. Can you make a safe take-off? Almost all aircraft handbooks have take-off performance f i g u r e s or graphs. All you have to do is look


them up. A Koch chart will convert

your basic ground roll for temperature and pressure altitude if your VELOCITY VELOCITY FOR





handbook is set up only for a standard day or if the figures are based on T, P.A, quite different from existing.

Pressure altitude can be obtained by setting your corrected altimeter to

easy to see that the maximum rate of climb occurs at V.,. This is very good when climb to an altitude in minimum time is desired. What if you want to climb over a certain height in a minimum distance? Can you see that if we draw a tangent line A to our rate of climb curve from the origin on the axis that we can determine the airspeed V, for best angle of climb or obstacle clearance (feet obtained vertical for horizontal distance traveled?) Certainly it can be seen that line B at max rate of climb airspeed does not give near the same angle as line A at max angle of climb airspeed. You would be surprised how many pros do not know that the airspeed for max angle of climb is less than the airspeed for max rate of climb. How about technique now that we are armed with this knowledge? The The Obstacle handbook for your particular aircraft How about the hot shots who prowill have airspeeds listed for max anceed to crank up, take off and fly gle of climb and max rate of climb. into trees or power lines at the end Pay attention to them and know when of the airport? Again a little bit to use them. Again, as with a short of aerodynamics to explain our point or soft field, line up at the very may be helpful. end. My procedure for an obstacle Take a look at Fig. 1. This shows clearance take-off (this could vary dethe characteristic power available and pending on type aircraft) is to roll the power required curves for a typical airplane normally to a couple knots reciprocating engine powered air- below best airspeed for max angle plane. Notice that there is a V STALL climb. Then rotate the airplane to and V M A X . All kinds of goodies can an attitude that will hold or mainbe found or derived from this graph. tain your max angle climb airspeed. Nine times out of ten you have your One that we are interested in is rate airspeed by the time your attitude is of climb. The excess horsepower (difestablished. Hold your attitude and ference between power available and airspeed until over the obstacle and power required) for each airspeed is then pick up your recommended en located. This is cranked into an equation route climb speed. Do not bank the airplane, unless absolutely necessary, to determine rate of climb and graphto keep that lift vector pointed ed against velocity. See Fig. 2. It is

29.92. Sounds like maybe a long complicated process but it takes only a minute once you have gone through it. It might save a life or broken airplane some day. The problem is a little tougher for the troops with homebuilts and no established take-off performance. One solution is to mark the roll together with existing temperature and pressure altitude every time you make a take-off in the new bird. A good batch of figures is developed, after a while, and a take-off performance graph or table of your own can be made up. Don't forget to take weight into consideration if you're carrying extra fuel, passengers, or baggage. Another factor to take into account is the age and operating condition of your aircraft and engine.

straight up. This all comes with practice and, again as before, practice your techniques and procedures under ideal conditions. Using flaps will usually degrade your climb-out performance, but check your manual. Again the homebuilder, with no established performance figures, is a little behind the eight ball. You can, however, with a stop watch, pencil and clipboard, smooth day, and a little patience, establish a rate of climb curve of your own. Just measure your rate of climb at different airspeeds, jot them down and draw a curve. You have some info now when you need it even if it is a little rough. Summary

We have talked about soft field, short field, and obstacle clearance take-offs. Some day you might run into a couple or even all three problems during one take-off. Here you're going to have to use a combination of procedures and techniques, pilot judgment, and plain common sense. There is no excuse for not knowing your airplane, its limitations, and your own limitations. Study the manual you received with the bird. Have an instructor demonstrate these take-offs if you are getting checked out in a new type. Practice makes perfect. Try out the procedures first under ideal conditions before you're faced with them in the rough. Be a smooth pilot since the aircraft will be flying at the lower airspeed limits during these maneuvers. Wait for another day if in doubt about making a safe takeoff. Pride has accounted for the death of many good pilots. Above all, be a thinker and fly safely. ®


The National Pilots Association announced on September 3, 1966, that Paul Poberezny, founder and president of the Experimental Aircraft Association had been named National Pilots Association Pilot of the Year for 1966. In making this presentation at NPA's annual meeting at the Grand Hotel on Mackinac Island, Willard W. Shepherd, president of the National Pilots Association said: "Paul Poberezny has made a unique contribution to aviation not only in the United States but throughout the world by his inspiring leadership of the Experimental Aircraft Association. This fine group of pilots serves as an outstanding example of what the individual can do to create practical small aircraft for sport and pleasure at minimum cost through devotion to an ideal combined with fine workmanship. We salute Paul Poberezny also

for his leadership in aviation education and the establishment of one of the finest private aviation museums in the world at Franklin, Wisconsin." Some of the previous winners of the NPA Pilot of the Year Award have been: William J. Schulte, Assistant Administrator for Gen-

eral Aviation Affairs of the Federal Aviation Agency in 1965.

Jerrie Mock of Columbus, Ohio in 1964 for her round the world flight. The late Joe Walker of NASA for his X-2 flights in 1963. Max Conrad in 1959 for his many long distance record breaking flights. ® SPORT AVIATION