Trim Use
Correct use of the trim requires that control pressures be applied to hold the desired flight attitude. Then the trim is adjusted to relieve present control pressures. Some initial change in trim should always be made since it reduces drag. If the aircraft is in an accelerating or decelerating mode anticipatory trim changes may be desired. Proper trim is a necessary part of flying from both operational and safety standpoints. The skill of the pilot is proportional to ability to trim.

Being able to trim the aircraft for any attitude requires that the pilot adjust the amount of download on the horizontal tail surfaces. It is this downwload that overcomes the nose weight of an aircraft. Download is 'lift' of the tail surfaces directed opposite to the lift of the wing. Refer to the Flight Training Handbook, AC 61-21 Page 277.

The important thing in using trim is always to be able to keep track of where it is. This is the reason I urge you to use a finger tip rather than a pinch. The fuel/pilots location in the c-150/152 are so near the CG that the trim movement will be rather constant. Any variation will be corrected if everything is predicated on beginning at a constant. The constant that I use has always been: Level cruise at 2400 rpm and hands off.

This constant works just a well if using C-172 or C-182. The presence of a rear-seat passenger will be corrected for using this constant. Pipers trim differently. Flaps change pitch attitude significantly but require very little trim adjustment. As you know the indicator markings are often illegible or not calibrated. A slipping trim cable is a frequent problem.

Cruise-Control
Learning to trim for level flight requires that you think in terms of setting as many constants as possible for a given flight situation. First, get a constant level attitude. Using the nose/horizon reference is more difficult than using the wing. The wing level with the horizon works best with the high-wing types. Second, get a constant speed at cruise speed or lower. If you exceed cruise speed without reducing power your trim setting will set for the higher speed. You should practice reducing power to 75% power setting as cruise. 2450 rpm is a good set. Third, trim off the pressure.

Is their only one way to trim? No. With experience you may just give a few flips and make a fine adjustment as required. You can even make numerous small changes. Doing it differently does not make it wrong. There is no one way to do anything in flying. Different aircraft and different trim systems require different techniques. The aim of my following suggestions is that it gets the beginner into anticipating trim movements as may be required for every change of configuration. Trim then becomes another constant.

Trimming off pressure is a search for the trim position that allows the aircraft to be flown with only one finger and the thumb. Which ever one you are using to hold altitude tells you which way to move the trim. Most students tend to move the trim more than required. You might do well as a student to use half as much movement as you think is required. You are trimmed when both finger and thumb need only to lightly brush the yoke. Getting trimmed to this point makes flying enjoyable and relaxing. Unlike an automobile, a correctly trimmed airplane can be flown hands-off. Once this sense of 'feel' is acquired you will not want to fly any other way. Every pilot has a slightly different 'feel' of an aircraft so changing pilots usually involves changing trim.

Every student and pilot should use trim to create opportunities to fly with rudder. Training aircraft usually have a rudder tab that has been set by prior pilots so that very little rudder is required in straight-and-level cruise. You can make slight turns using just the rudder with little difficulty. Steeper turns with the rudder will cause a loss of altitude. Much of this altitude is regained when using hard rudder to level the wings. Practice flying with just the rudder when copying the ATIS, using the sectional, or just for fun.

Once an aircraft is trimmed for a particular airspeed in level flight, additional power or a reduction in power will cause the aircraft to climb and descend at that airspeed. You must exercise some yoke control and rudder to correct for any transitional oscillations. Trim remains the same. Trim is the cruise control of flying an aircraft. I very much recommend not changing trim when descending from cruise to pattern altitude. Descend by reducing power. Enter downwind at cruise speed until abeam the numbers. The deceleration in airspeed while holding altitude on downwind will allow you to trim for the approach speed while reaching the appropriate 'key' position for turning base.

Airplanes should be trimmed for every condition of flight except during times you may be turning or changing airspeeds. Flying an aircraft out of trim makes control difficult and wearisome. Initial trim settings should be just 'close'. Fine trim when the power and airspeed has stabilized. The check of trim setting is confirmed by letting go of the controls.

Every control system has inherent frictions that tend to keep them in position. In some cases this internal aircraft factor may make an aircraft seem out of trim. Occasionally an aircraft may be affected by atmospheric conditions. In turbulence a tight grip will only accentuate the bumps. Single finger control is best in choppy conditions.

If your aircraft has rudder trim, you adjust it only after elevator trim has been fine-tuned. Rudder is trimmed in wings-level flight with a nose-on reference point. Use rudder pressure to maintain the reference point and then trim off the pressure. Confirm rudder trim setting by letting go of all the controls. Aileron trim, if there, is set much the same way.

Once an aircraft is completely trimmed it can be neatly controlled with small brief rudder input. Pitch changes can be controlled with VERY small power changes. Flying with just the rudder is a very useful experience. Even in instrument conditions the rudder can be used. Step on the high wing of the attitude indicator and the turn coordinator. Step on the heading desired of the heading indicator. Such flying removes flying as a problem part of the IFR equation.

Tight Grip vs light touch
The left hand has only two useable digits while flying. The forefinger is behind the yoke for back pressure and the thumb is for forward pressure. You cannot feel the pressures requiring trim if a heavier touch is used. Tension is the greatest single cause of a full tight grip. Note how a beginning driver grips the wheel. The sooner the student learns that a light touch with proper trim gives more positive control, the better. There is a safety factor in this. Any distraction or movement of the body will affect yoke pressure. This is especially true if the pressure is being held tightly against the trim. The pilot with a light touch can let go of the yoke and the plane will fly as trimmed. The tight grip increases fatigue as a factor. Easy to say; difficult to do. IFR pilots do it better with a light touch. A full grip on the yoke seems to result in inadvertent climbs and turns. Tension is the greatest single cause of the tight full grip on the yoke. The best analogy is the differences between student and experienced drivers in holding the steering wheel of a car.

One Finger and a Thumb Flying
Over controlling is a symptom. A student or pilot who is heavy, reactionary, or hesitant on the controls is not yet a believer. The proficient pilot has faith in the airplane’s ability to perform in a particular manner. All proficient flying is an act of faith just as is having the runway disappear during a landing.

Students do not begin as believers. The instructional process is supposed to turn students into believers. I had to fly 200 hours before I began to believe. Prior to that point I controlled with a tight grip on both the yoke and the seat cushion. I tore two seat cushions out of the C-150 I learned in, because I could not accept the fact that the plane could fly without my ‘firm’ hand on the control. Occasionally, after a flight I would need to unwind my fingers off the yoke with my right hand. My instructors told me to relax but never showed me how to do it.

Now, I think I know how to show a student how to avoid over-controlling. I nag at them for the way they trim, apply and take off power, hold the yoke, and see what is happening. Most of all, I insist that they let go of the yoke and try to SEE what the airplane does without their input. Initially, students lack the faith necessary to believe that the plane will actually fly without their help. In time, they will learn that the plane, properly trimmed will perform better without their meddling.

Turbulence is one of the best opportunities for the pilot to see this. The natural, normal reaction of a student pilot in turbulence is to grip the yoke more firmly. This is what you do going over chuckholes in an automobile. In an airplane a firm grip gives you a two-for-one bump. A light touch will reduce the extent of light to moderate turbulence significantly. When students turn the plane over to me in turbulence they always contend that it stopped just as I take the controls. The real difference is that I have faith in the plane’s ability to do a better flying job than I can.

If, from the very first moment of sitting in an airplane, a student is ‘required’ to limit his touching of the yoke to just forefinger in back and thumb in front a considerable amount of instructional time and money could be eliminated from learning to fly. Unfortunately, the student usually gets off on the wrong foot (hand). The design of the yoke with its scallops for the full fist grip leads to the belief that it is designed that way for a purpose. A student has probably been on several demo-rides where the idea is to suck the student into a flight program. The initial acceptance of a full fist grip on the demo-rides means that unlearning is going to be necessary. There is enough unlearning required in learning to fly as it is. To add the way you hold the yoke to the mix just makes the process more difficult.

I once had a student come to me with a few hours in the C-150. He had never used the trim wheel. He could fly quite well without using the trim wheel. He just set it at a level flight setting and left it there. Reducing the power to 1500 and adding full flaps brought him down to a fine approach and landing. Remove the flaps and a bit of backpressure he could climb reasonably well. No problem except that he was usually exhausted after a flight from the constant strain of holding the yoke during maneuvers. There are still pilots flying C-150s this way because it can be done and you don’t mess with the trim. These pilots probably soled in ten hours or so. The shock came when they tried to transition to a more complex or powerful aircraft.

I do not teach students to fly the C-150. I teach students to fly the C-150 as though it were a complex powerful aircraft. We trim for every configuration to hands-off flight. We fly only with forefinger and thumb, and preferably only one or the other until neither are required. To fly this way the student must be taught to SEE ahead of the airplane. (See Budd Davisson’s article in Dec. 1997 of Flight Training magazine pg 28-31) My first ten hours of flight training are devoted to teaching the student to SEE and TRIM the plane for hands-off flight. Not all are proficient in the ten hours but I don’t solo them until they trust the plane to stay at the selected airspeed and flight path.

I once facetiously suggested that a student sandpaper his finger tips to force him to lighten up on the controls. Next flight he showed up with red, raw fingers. Didn’t help all that much but I’m more careful in my suggestions now. Just finished checking him out in the C-182RG, he remarked about how stable the plane was. Interesting, how he gave the plane credit for his ability to fly hands-off. A universal comment that comes back to me from my students who progress into instrument flying, is that the instrument instructors are always pleasantly surprised how my students all have a light touch. As a school teacher, the highest praise I ever received was when a student would thank me two years after leaving my classroom.

So, what does all this have to do with over-controlling? Pilots over control because they have not learned to SEE, TRIM and LET GO. To a degree, I cannot tell a student just when and where to look out the windshield. It is a
very individual problem and solution. I can point out the necessity, and by repetition help the student anticipate the nose position, trim setting, and power for the most difficult of these configurations. I’m talking about level cruise.
With practice you can do it with your eyes closed. You will need to SEE only to confirm. Then just for fun you can move your arms forward and back to initiate shallow climbs and descents. Notice I haven’t mentioned the rudder. That’s desert.

I you find that you are consistently having to correct for climb or descents, change from two finger flying to appropriate one finger flying.  until you find the pressure required for level flight at this configuration and power setting.  THEN make your slight trim adjustment.

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