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The Takeoff
2010-03-18

The Takeoff

The runup is completed and the trim is set for takeoff. We have used our pre takeoff and takeoff checklist and have been cleared by the tower. Taxi toward a point adjacent to the runway that will allow a turn that will give a full view toward final and base. Hold a couple of inches of back yoke. Cross the hold bars and align the plane with the runway centerline in a slow taxi. Check that the runway is clear. Smoothly apply full power. Lightly touch and hold right rudder as required to keep nose straight. Quick-check the instruments and listen to the engine. Learn what a normal aircraft engine sounds like during takeoff. With experience in hearing a good engine you will more readily recognize poor engine operation.

I let my students handle the first and all other takeoffs unless a demonstration is called for. Student applies power and rotational forces. Power is applied smoothly, rapidly, and fully. The instructor maintains initial directional control and may reach across to the student's fingers on the left yoke to help as required. The idea is to allow the student to relate pressure with yoke movement and nose attitude. The instructor's hand pressures on the student's is far more indicative of control requirements than if the instructor were to use his own yoke. Instructor maintains active control of rudder.

A takeoff has three distinct phases, first, the takeoff where the initial acceleration occurs and the emphasis is upon directional control and pitch attitude. Second, the liftoff where the pitch attitude is held to let the aircraft fly off around the landing gear rotation axis, only to be changed to adapt to the center of lift horizontal axis for acceleration. Finally, the initial climb out is set by attitude to perform a climb at Vy. This is usually the noise abatement climb speed.

The control position during the takeoff is set for full deflection toward any crosswind. In a crosswind weight is left on the main gear with the nose wheel barely off the ground. Initial directional control is a function of braking, since the rudder is the first control to become effective, use it as soon as it becomes effective. Liftoff is initiated at POH recommended speed by leveling the yoke and increasing the pitch to get liftoff before side loads can develop. Rudder is applied to crab into the wind sufficient to maintain track of runway heading. Do not set climb pitch until reaching Vx or even Vy.

Your problem, should you chose to undertake it, is to draw the diagram and place the words where they belong..

wind into position
direction runway and hold
hold bars
taxiway clearing/closer hold
short position to see runup area landing aircraft
runup
position

Make a guess at a yoke setting that will get and keep the nose wheel off the ground. This setting is usually obtained by moving the control-lock hole about three inches from the panel in a C-150. Every aircraft has such a yoke reference you just need to find it. Lock the elbow on the door. Scan the instruments ;when you first apply power. As acceleration occurs the elevators will become more effective and allow a yoke position to raise the nose wheel off the ground. This is called rotation and in the C-150 occurs at about 45 kts . If the rotation attitude selected is correct the aircraft will lift off at Vso but never any faster than 60 kts. This is the standard from which special circumstances require additional knowledge and skill. Any rotation will require an application of right rudder. Rudder is best applied in anticipation rather than reaction. The higher the nose the more right rudder required.

Rearward yoke pressure is maintained with one finger to get weight off the nose wheel. This pressure and any additional required to obtain lift off at 55 kts is locked by pressing the elbow and arm against the door. Minimum lift off speeds are desirable since higher speeds wear out tires. At lift off the nose is slightly lowered to allow acceleration to best rate of climb of 65 kts. If the initial trim setting was neutral in a C-150, a full downward turn of the trim wheel top button to the very bottom will come very close to being the correct trim setting for a 65 knot climb. Use this first climb out to let the student experiment with the results of full movements of the trim wheel. Trim is the cruise control of flying. Its early introduction and use is essential for developing awareness and a light control touch.

The rotation fault in the beginning is failing to do it at all. The plane proceeds down the runway at 60, 70 or even 80 knots and the student is still waiting for it to fly. Personally, I never let this happen more than once. It is exceptionally difficult on the aircraft. The next rotation fault is called over-rotation. This means that the nose is held so high off the runway that were the aircraft to become airborne it would be unable to climb or to accelerate. It is behind the power curve. The only thing that will get the aircraft flying is lowering the nose. Unless this is slowly and very carefully done a relatively hard contact with the ground will occur. This over-rotation is a practiced procedure used for making soft field takeoffs.

The rotation used for crosswind takeoffs is somewhat different in that the aircraft is lightly held on the runway with yoke held fully into the wind. This prevents the wind from sliding the aircraft sideways on the runway surface. At the moment the aircraft reaches a safe takeoff speed for the existing ground effect the yoke is leveled and the yoke is used to 'hop' the aircraft off the ground while the rudder is used to crab the nose into the wind. Once in the air the airplane is flown in ground effect long enough to reach climb speed. Takeoff stalls often occur if the pilot tries to climb before acquiring POH climb speeds. Through a misunderstanding of how ground effect can give an initial but false indication of climb capability, the pilot will initiate a climb at a relatively low airspeed only to find that his climb capability ceases at about half a wing span height above the ground.

There is an alternative to this minimum speed lift off. Some pilots prefer to let the aircraft accelerate nearly to Vx before lifting off the ground. This greatly increases tire wear and nose strut problems. On the other hand it does let the aircraft climb continuously out of ground effect without the momentary leveling off for acceleration.

Vso or minimum safe operating speed is the most desirable takeoff speed for several reasons. Aircraft tires are relatively small and expensive. The sooner they are off the ground the less wear. Rolling ground contact at high speeds is potentially more damaging to the airframe structure than at slow speeds. We want to get off the grounds as slow as possible. Less runway is required, thus more is available for aborted takeoffs. See Abort

The best angle of climb speed (Vx) is a precise speed at present weight that gives the highest altitude over distance. The hazard of the best angle of climb speed is that it is close to the power off stall speed. A power failure at best angle requires an immediate lowering of the nose to avoid disaster. The best rate of climb speed (Vy) is a precise speed at present weight that gives the highest altitude over time. Any speed different than the precise speed gives reduced performance.

Vx is the climb speed after Vso lift off that will, in the shortest distance and steepest climb, get the aircraft over an FAA tree. All FAA trees stop growing at 50".

The Vy climb would make the aircraft fly through the top branches of the FAA tree but would get the aircraft to a higher altitude in a given time interval.

Once we have established a climb at 65 kts in the C-150 the trim must be fine tuned for hands off. With experience you can pre-set the trim and 'know' the correct pitch attitude.

On takeoff it is a good practice to have the student check his runway alignment between three and four hundred feet AGL. The first time a student does this he will unknowingly pull the yoke and cause dramatic attitude and airspeed changes. Emphasize that the aircraft must be correctly trimmed and yoke released for the runway check. If parallel runways are it use it is well fly a 10 degree divergence from runway heading as a safety measure regardless of the wind and especially if there is a crosswind component that could carry you into the extended line of the adjacent runway. Once you have learned the standard takeoff you must be prepared to exercise different configuration, power control and pitch attitudes for the other types of takeoff.

Since so many takeoffs occur without incident, pilots are given a false sense of certainty that all takeoffs are successful. POH takeoff performance is based on an optimum technique. If you deviate from this optimum the aircraft performance will decline. In addition, with the present average age of operational aircraft you should add at least a 20% fudge factor into the book figures.

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