Flight Instruments

to the center of the wind screen. When in coordinated flight, the string trails straight back over the top of the wind screen. E D L . E C C . . E D L . E C C . . When the aircraft is either slipping or skidding, the yaw string moves to the right or left depending on the direction of slip or skid. TURN COORDINATOR TURN COORDINATOR L R L R 2 MIN. 2 MIN. Instrument Check NO PITCH NO PITCH INFORMATION INFORMATION During preflight, ensure that the inclinometer is full of fluid and has no air bubbles. The ball should also be resting at Slipping turn Skidding turn its lowest point. When taxiing, the turn coordinator should indicate a turn in the correct direction while the ball moves D.C. opposite the direction of the turn. ELEC. Attitude Indicator TURN COORDINATOR The attitude indicator, with its miniature aircraft and horizon L R bar, displays a picture of the attitude of the aircraft. The 2 MIN. IN N FO O R P M I A TC TI H ON relationship of the miniature aircraft to the horizon bar is the same as the relationship of the real aircraft to the actual Coordinated turn horizon. The instrument gives an instantaneous indication of even the smallest changes in attitude. Figure 8-22. If inadequate right rudder is applied in a right turn, The gyro in the attitude indicator is mounted in a horizontal a slip results. Too much right rudder causes the aircraft to skid plane and depends upon rigidity in space for its operation. through the turn. Centering the ball results in a coordinated turn. The horizon bar represents the true horizon. This bar is fixed to the gyro and remains in a horizontal plane as the Inclinometer aircraft is pitched or banked about its lateral or longitudinal The inclinometer is used to depict aircraft yaw, which is axis, indicating the attitude of the aircraft relative to the true the side-to-side movement of the aircraft’s nose. During horizon. [Figure 8-23] coordinated, straight-and-level flight, the force of gravity causes the ball to rest in the lowest part of the tube, centered The gyro spins in the horizontal plane and resists deflection between the reference lines. Coordinated flight is maintained of the rotational path. Since the gyro relies on rigidity in by keeping the ball centered. If the ball is not centered, it can space, the aircraft actually rotates around the spinning gyro. be centered by using the rudder. To center the ball, apply rudder pressure on the side to Bank index Gimbal rotation which the ball is deflected. Use the simple rule, “step on the ball,” to remember which rudder pedal to press. If aileron and rudder are coordinated during a turn, the ball remains centered in the tube. If aerodynamic forces are unbalanced, t i h n e F b ig al u l r m e o 8 v -2 e 2 s , a i w n a a y s f l r ip o , m th t e h e r a c t e e n o te f r t u o r f n t h is e t t o u o b e s . l o A w s f s o h r o w th n e 20 I 0 I 02 2 0 0 I 0 I 0 20 a a n s g k l i e d , o t f h b e a r n a k te , a o n f d t u th rn e b is a t l o l m o g o r v e e a s t t f o o t r h t e h e in a s n id g e le o o f f t h b e a n tu k r , n a . n I d n 20 I 0 I 0 2 0 2I 0 0 I 0 20 the ball moves to the outside of the turn. To correct for these TEST STBY PWR conditions, and improve the quality of the turn, remember to “step on the ball.” Varying the angle of bank can also help Roll gimbal restore coordinated flight from a slip or skid. To correct for a Horizon reference arm slip, decrease bank and/or increase the rate of turn. To correct Gyro Pitch gimbal for a skid, increase the bank and/or decrease the rate of turn. Yaw String Figure 8-23. Attitude indicator. One additional tool that can be added to the aircraft is a yaw string. A yaw string is simply a string or piece of yarn attached 8-18