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SW Aviator Magazine
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3909 Central NE
Albuquerque, NM 87108
Phone: 505.256.7031
Fax: 505.256.3172 |
| publisher@swaviator.com |
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| Flying to Remote Airstrips |
| by Cordell Akin photos by Mark Swint |
For pilots flying in the Southwest, there is something more interesting, more challenging, more demanding and more rewarding than flying somewhere for the $100 hamburger. Is that possible? What could it be? Quite simply, it is to load your tent and camping gear and fly to a remote airstrip far back in the mountains or high atop a plateau and spend a week living beside your airplane. Don’t forget the fishing gear, your hiki ng boots, and the camera. This is an experience you will want to share with the folks back in the fast-paced world that will make them envious of your vacation.
The very geographical nature of the Southwest provides opportunities for pilots to visit airstrips that are short high, sloping, dirt or grass, and with obstacles in the approach and departure path. Anyone flying to such clearings in the trees should become well practiced in the area of flight known as maximum performance maneuvers. You remember what they are from training days: short field takeoffs and landings, and soft field takeoffs and landings. If you stay sharp on these maneuvers your passengers may not talk about you like they did the pilot in this old story: After a successful hunting trip the pilot who was flying the passengers for the second year in a row, loaded three 200 pound hunters and an entire elk in a four place airplane and departed from a short airstrip. They all survived the crash right after takeoff and one hunter said to another, "You know, Charlie, we sure have a skilled pilot. This is only 100 yards from where we crashed last year."
DEPARTING A WILDERNESS AIRSTRIP WITH OBSTACLES
Most short unpaved airstrips will not have a taxiway, so you must back taxi the takeoff runway and turn around, wasting as little runway as possible. Be careful when making the turn that the aircraft tail does not strike something at the end of the runway, like a stump. We're talking real bush here. Straighten the nose wheel, hold the brakes and apply full power. If the strip is at high altitude, lean the mixture at full power to get maximum performance from the engine. Before releasing the brakes, check all the engine instruments for normal readings and normal power. Be ready to abort the takeoff if anything appears, sounds, or feels abnormal. Hold the aircraft on the ground until Vx (best angle of climb) speed is reached. Rotate and maintain Vx until the obstacle is cleared, then increase speed to Vy (best rate of climb). As the aircraft leaves ground effect and induced drag (drag resulting from the production of lift) increases, the initial pitch angle of the nose will need to be lowered slightly to maintain Vx. You must not give in to the urge to lift the nose prematurely when you see trees coming closer at an alarming rate. If the situation is tight, the speed you need is Vx, because it will give you the best angle of climb to clear the obstacles.
So, if you practice short field takeoffs you can depart from an airstrip whenever you want, right? Wrong. Sometimes the density altitude will not allow the clearance of obstacles regardless of your technique. In high hot situations, it will help to plan your takeoff in the early morning when the temperature and density altitude are lower. If possible always take off downhill and avoid tailwinds. Ground roll will be increased about 10% for each 2 knots of tailwind. It is a good idea to increase all Pilot Operating Handbook (POH) figures for 50 foot obstacle clearance by 25% in order to take into account engine hours, extra parasite drag from the addition of antennas or the removal of wheel fairings, and your own skill level. Keep in mind that published obstacle clearance distances do not take into consideration the real world realities of turbulence and downdrafts. These could place you in the position of looking squarely into the face of a knot-hole half way up a tree on takeoff. If the situation is truly marginal, do a pattern with just you on board, than add passengers one at a time in succeeding patterns to see how the aircraft performs under the actual conditions.
SHORT FIELD ARRIVALS
I once flew to a short, rough, steep sloping airstrip carved out of a coffee plantation with 75 foot Eucalyptus trees at the approach end. It could have been an airstrip carved out of Yucca plants or pine trees, it doesn’t matter. The passenger-to-be on the ground held a six foot length of toilet paper into the air for a windsock. The white showed up great against the green coffee trees. On final approach I saw that there was an opening in the trees about 100 yards to the left of the runway. I went through the gap, reduced power and turned right about 50 feet above the ground to line up with the strip. Touchdown was smooth but I bounced down the strip like a basketball due to its unevenness and came to a stop at the far end. The landing required precise airspeed control and accurate, coordinated maneuvering close to the ground. I tell you this story to illustrate the fact that wilderness airstrips can be very demanding of your piloting skills, and you should not attempt to fly to them unless you are proficient in short and soft field takeoffs and landings.
Clearing the trees on takeoff will be a moot question if you run off the end of the runway on arrival, or damage the aircraft by hitting some unseen object on the strip. Of course it could extend your vacation while you try to figure out a way to get back home. If you are not certain about the condition of the strip, fly about 100 feet above the runway along the left side, so the strip is on your side, with 20 degrees of flaps at a slow cruise airspeed and observe the conditions. If it all looks well, climb to altitude and fly a pattern for the landing.
There is a reason why the practical test standards for private pilot stipulate that the aircraft must touch down within 200 feet of a selected point. On a short field arrival you want to touch down as close to the beginning of the runway as possible. The key to doing this involves both pitch and power. Once established on final approach with full flaps, pitch the aircraft to achieve the short field approach airspeed given in the POH. Next reduce power until the aircraft begins to sink, then increase power just to hold a straight glide path to the beginning of the runway (assuming no obstacles). With this approach, when power is reduced, the aircraft will sink and when power is added the sink will stop. This makes possible an accurate straight line descent to the aiming point on the ground that should remain stationary in the windscreen. The most common mistake pilots make is to leave in too much power and get high on the approach. Then, even though power is reduced to idle and the proper airspeed maintained, the landing point is exceeded by a good distance.
At the short field approach airspeed and with just enough power to hold the glide path, reduce power to idle just before the intended touchdown point and there will be no speed left to cause a float down the runway. Allow the main wheels to contact the surface in a modified flare so that maximum braking can begin as soon as possible. A good short field landing will not be a greaser, but a firm touchdown, the opposite of a soft field landing. It is not necessary to retract the flaps immediately after landing since the drag they produce is more beneficial than retracting them to put the weight on the wheels. On a rough short strip the wheels are going to be bouncing without a lot of braking action initially. The drag of flaps will help slow the aircraft.
SOFT FIELD DEPARTURE
It has been said that if it takes full power to taxi you have either forgotten to remove the chocks or the tail is still tied down. I would like to add one more situation. One time I landed on a dirt airstrip after a heavy rain in a pressurized 210. Slowing to taxi speed occurred very quickly and then it took full power to taxi in the red mud with about 2 inches of it on all the wheels.
A soft field takeoff starts with the taxi. The control wheel should be full back to allow the propeller slipstream to increase down pressure on the elevator and lighten the nose wheel. During taxi and takeoff in soft conditions the nose wheel must be protected. If the nose wheel happens to be on the rear of the plane, the soft field task is easier.
Refer to the POH for your aircraft as to flap setting for a soft field takeoff. It will be 10 degrees on some light aircraft. This flap setting allows enough lift in relation to drag to get the aircraft in the air in ground effect as quickly as possible, allowing the weight to be shifted from the wheels to the wings. When full power is applied with the control wheel full back, the nose will initially rise higher than needed. At that point reduce the back pressure just enough to keep the nose wheel off the muddy surface. With the wings in this high angle of attack position, the aircraft will lift off into ground effect at an airspeed too slow to sustain flight above ground effect. Therefore, once liftoff occurs a slow but positive forward pressure must be applied to the control wheel in order for the aircraft to level out in ground effect and accelerate to Vx before trying to climb. The flaps can be retracted once the aircraft is climbing.
Ground effect occurs within one wing span of the runway, increasing closer to the runway. It is the result of the runway surface interfering with the wingtip vortices and the average relative wind around the aircraft that produces induced drag. The reduction of drag in ground effect is quite pronounced, being about 25% at one-forth of the wingspan above the runway.
SOFT FIELD ARRIVALS
If the airstrip is soft, touchdown must be made softly on the main wheels and the control wheel held full back to protect the nose wheel. I once landed on a soft grass strip and held the nose off as long as possible as the aircraft rapidly slowed. When the nose wheel finally touched down at a slow speed it sank into the soft dirt half way up the tire. There was no damage, but the aircraft had to be pushed by hand to firmer ground.
 Assuming there are no obstacles in the approach path, a soft field landing is normally made with half flaps and a normal approach speed. Half flaps work better than full flaps in most cases due to the fact that the pitch change in the flare is less pronounced because the approach angle is not as steep. The most consistently soft landings can be made if the power is reduced to slightly more than idle on short final and left there until the wheels touch. The throttle may then be reduced to idle. In an actual soft field situation the power may be increased after touch down to keep the nose wheel elevated until firmer ground is reached.
It is important to keep raising the nose in the flare to hold the wheels off the runway as long as possible with the stall warning horn activated. Once the main wheels touch, maintain full back pressure to keep the nose wheel off the surface until it falls by itself, then continue the back pressure until the taxi is completed.
Whether or not you ever fly into a remote airstrip in the Southwest with a tent and fishing rod or camera, staying proficient in maximum performance takeoffs and landings will make you a better pilot. Besides, the airplane tires, landing gear and airframe will benefit from soft field landings. So, why not try to make every landing a soft field one, even those you make with full flaps. And by the way, your self esteem will also benefit when your passengers call you a great pilot.
Cordell Akin is a CFII, MEI with a total of 10,000 hours and 3,000 hours as a flight instructor. He spent 15 years in East Africa flying a C-185 and a P-210. He is the owner of Akin Air at Coronado Airport in Albuquerque.
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The material in this publication is for advisory information only and should not be relied upon for navigation, maintenance or flight techniques. SW Regional Publishing, Inc. and the staff neither assume any responsibilty for the accuracy of this publication's content nor any liability arising out of it. Fly safe.
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