IFR Written Test – IFR Aerodynamics (1) [항공사 기출문제]

An airplane, like any object, requires a sideward force to make it turn. This force is supplied by banking the airplane so that lift is separated into two components at right angles to each other. The lift acting upward and opposing weight is the vertical lift component, and the lift acting horizontally and opposing centrifugal force is the horizontal lift component. The horizontal lift component is the sideward force that causes an airplane to turn.

At a given airspeed, the rate at which an airplane turns depends upon the amount of the horizontal component of lift.

When a turn is coordinated, horizontal lift equals centrifugal force. This is indicated when the ball on the turn coordinator or turn-and-slip indicator is centered.

In comparison to level flight, a bank results in the division of lift between vertical and horizontal components. To provide a vertical component of lift sufficient to maintain altitude in a level turn, an increase in the angle of attack is required.

Illustration 2 in Fig. 144 indicates a slip, in which the rate of turn is too slow for the angle of bank, and the lack of centrifugal force causes the ball to move to the inside of the turn. To return to a coordinated standard-rate turn, you should increase left rudder (i.e., step on the ball) and increase the rate of turn. A standard-rate turn is indicated when the needle is on the "doghouse" (i.e., standard rate) mark. It is presently indicating a half-standard-rate turn.

A coordinated turn is one in which the ball is centered as indicated in illustration 3. The horizontal component of lift equals centrifugal force.

Illustration 1 in Fig. 144 indicates a skid, in which the rate of turn is too great for the angle of bank, and excessive centrifugal force causes the ball to move to the outside of the turn. To return to coordinated flight, you should increase right rudder (i.e., step on the ball) to center the ball. A standard-rate turn is indicated when the needle is on the doghouse mark. Thus, the rate of turn must be increased to result in a standard-rate turn.

A skidding turn occurs when centrifugal force is greater than horizontal lift. As shown by illustration 1, the ball is outside the turn.

A slipping turn is one in which the centrifugal force is less than horizontal lift. As shown by illustration 2, the ball is inside the turn.

In skidding turns, centrifugal force is greater than horizontal lift. The load factor increases in level turns.

To compensate for added lift, which would result if airspeed were increased during a turn, the angle of attack must be decreased and the angle of bank increased if a constant altitude is to be maintained.

To compensate for the decreased lift resulting from decreased airspeed during a turn, the angle of bank must be decreased and/or the angle of attack increased.

To compensate for the decreased lift resulting from decreased airspeed during a turn, the angle of bank must be decreased and/or the angle of attack increased by increasing the pitch attitude.

A standard-rate turn means an airplane is turning at a rate of 3°sec. A left turn from 090° to 300° is a total of 150° (90° to north and another 60° to 300°. Thus, at standard-rate, it would take 50 sec. (150° /
3°sec.).

A standard-rate turn means an airplane is turning at a rate of 3° sec. Thus, a half-standard-rate is a turn at the rate of 1.5° sec. To turn 135° at half-standard-rate would take 90 sec. (135° / 1.5° sec.) or 1 min. 30 sec.

A standard-rate turn (3° sec) takes 2 min. for 360°. A half-standard-rate turn (1.5° sec.) would thus take 4 min. for 360°

A standard-rate turn means an airplane is turning at a rate of 3° sec. To turn 180° at a standard-rate would take 60 sec. (180° / 3° sec.), or 1 min.

A half-standard-rate turn means an airplane is turning at a rate of 1.5° sec. A turn clockwise from 090° to 180° is a total of 90°. Thus, at a half-standard-rate, it would take 60 sec. (90° / 1.5° sec.).

The radius of turn at a constant-bank level turn varies directly with the airspeed, while the rate of turn at a constant-bank level turn also varies with airspeed. If airspeed is increased during a constant-bank level turn, the radius of turn will increase, and rate of turn will decrease.

To increase the rate and decrease the radius of turn, you should decrease airspeed and increase the bank angle.

A standard-rate turn means an airplane is turning at the rate of 3° sec. A turn to the right (or left) from 090° to 270° is a total of 180°. Thus, at standard- rate, it would take 60 sec. (180° / 3° sec.), or 1 min.

Conditions that determine the pitch attitude required to maintain level flight are airspeed, air density, wing design, and angle of attack. At a constant angle of attack, any change in airspeed will vary the lift. Lift varies directly with changes in air density. An airplane's wing has lift characteristics that are suited to its intended uses. Lift increases with any increase in the angle of attack (up to the critical angle).

To level off from a climb and maintain a specific altitude, you should start the level-off before reaching the desired altitude. If your airplane is climbing at 500 fpm, it will continue to climb at a decreasing rate throughout the transition to level flight. An effective practice is to lead the altitude by 10% of the indicated vertical speed (i.e., at 500 fpm, use a 50-ft. lead).

To level off from a descent to a specific altitude, you should start the level-off before reaching the desired altitude. If your airplane is descending at 500 fpm, it will continue to descend at a decreasing rate throughout the transition to level flight. An effective practice is to lead the desired altitude by 10% of the indicated vertical speed (i.e., at 500 fpm, use a 50-ft. lead).

As a general rule, altitude corrections of less than 100 ft. should be corrected by using a half-bar-width (i.e., less than a full-bar-width) correction on the attitude indicator.

The pitch instruments are the attitude indicator, the altimeter, the vertical speed indicator, and the airspeed indicator. The attitude indicator gives you a direct indication of changes in pitch attitude when correcting for altitude variations. The rate and direction of the altimeter and vertical speed indicator confirm the correct pitch adjustment was made, and the altimeter is used to determine when you have reached your assigned altitude.

As a general rule, altitude corrections of less than 100 ft. should be corrected by using a half-bar-width correction on the attitude indicator.

To enter a constant-airspeed descent from level cruising flight and maintain cruising airspeed, you should simultaneously reduce the power smoothly to the desired setting and reduce the pitch attitude slightly by using the attitude indicator as a reference to maintain the cruising airspeed.

To level off from a descent at an airspeed higher than the descent speed, it is necessary to start the level-off before reaching the desired altitude. At 500 fpm, an effective practice is to lead the desired altitude by approximately 100 to 150 ft. above the desired altitude. At this point, add power to the appropriate level flight cruise setting.

To level off from a descent at descent airspeed, lead the desired altitude by approximately 50 ft., simultaneously adjusting the pitch attitude to level flight and adding power to a setting that will hold airspeed constant. Trim off the control pressures and continue with the normal straight-and-level flight cross-check.

To enter a constant-airspeed climb from cruising air-speed, raise the miniature aircraft in the attitude indicator to the approximate nose-high indication appropriate to the predetermined climb speed. The attitude will vary according to the type of airplane you are flying. Apply light elevator back pressure to initiate and maintain the climb attitude. The amount of back pressure will increase as the airplane decelerates.

The three fundamental skills involved in all instrument flight maneuvers are instrument cross-check, instrument interpretation, and aircraft control. Cross-checking is the continuous and logical observation of the instruments for attitude and performance information. Instrument interpretation requires you to understand each instrument's construction, operating principle, and relationship to the performance of your airplane. Aircraft control requires you to substitute instruments for outside references.

The third fundamental skill in instrument flying is aircraft control. It consists of pitch, bank, and power control.

The correct sequence in which to use the three fundamental skills of instrument flying is cross-check, instrument interpretation, and aircraft control. Although you learn these skills separately and in deliberate sequence, a measure of your proficiency in precision flying will be your ability to integrate these skills into unified, smooth, positive control responses to maintain any desired flight path.