Basic Instrument for Flying

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Flying by reference to instruments alone is very different from using them in conjunction with outside observations. While you should never go looking for instrument conditions, knowing basically how to use instruments could be very handy if the unexpected takes place. This chapter is by no means comprehensive, but offers only basic guidance for flight in instrument conditions.

The basic flight instruments were discussed previously in regards to their simple functions. The following discussion illuminates the particulars of using these instruments for blind flight, especially as they relate to each other.

Airspeed indicator
In addition to airspeed, the indicator may be a useful cross-reference with the artificial horizon and vertical speed indicator to verify that they are also working correctly. If in a dive, the airspeed will increase. In a climb it will decrease as the nose rises. If you keep power settings constant, a drop in airspeed could mean the nose is rising. Cross-referencing this information with the artificial horizon, altimeter, and vertical speed indicator will help determine a faulty instrument in the system. If the other gauges give an indication that the plane is in level flight but the airspeed indicator is decreasing or increasing, it could be a sign of failure.

During a climb or descent, the attitude indicator can be used to establish pitch, but the airspeed indicator is used to refine the attitude until airspeeds match desired values, such as Vx or Vy in a climb. When pilots become disoriented under instrument conditions, it is not uncommon for the nose to drop and the airspeed to build rapidly. By monitoring the airspeed indicator, this problem can be avoided. The airspeed indicator rises to prominence in pilot attention while the airplane is climbing or on approach and landing phases of flight.

Attitude indicator
The attitude indicator (AI), sometimes called artificial horizon, is one of the most useful, and most abused, instruments in the panel. Both bank and pitch attitudes are available from the AI, making it the center of the pilot’s attention—sort of replacing the view out the windshield. Unfortunately, most pilots have a tendency to focus almost exclusively on the AI to the point of excluding the other instruments. This tendency to “fixate” on a single instrument —even if it’s a particularly valuable one, like the AI, should be avoided.

Next to the AI, the altimeter probably occupies the majority of a pilot’s attention, especially while cruising straight and level. In theory, a pilot flying instruments at a safe altitude should handily avoid collision with anything on the ground. Couple that with air traffic controller demands, and pilots watch the altimeter almost religiously.

Turn and bank indicator
Figure shows a turn and bank indicator, also known as a turn and slip indicator. You can see that it is made up of a vertical white bar, called a needle, and a black sphere in a glass tube, called the ball. If the ball is centered and the needle is located on the center mark, the plane is in a wings-level attitude. Better yet, if the wings are level, the plane is NOT turning. Although simple, this piece of information may be very useful in cross-checking the compass and directional dyro. But if the needle is to the left or right of the center marker, the plane is turning (i.e., changing heading). This can be a useful indicator of the plane’s attitude and a good cross-check of the artificial horizon. If the needle is on the left or right “dog-house,” (or the index mark corresponding to a bank on instruments which depict an airplane) and the ball is centered, the plane is making a turn in that direction at 3 degrees per second of heading change. When flying under instrument conditions, turns are normally made at the standard rate. The timing and layout for most instrument approaches are set up for standard rate turns. Like the artificial horizon, the turn and bank indicator is driven by a gyroscope.

Directional gyro
The DG does not inherently know magnetic directions unless slaved to a magnetic compass. In simple installations, where the DG is unslaved, pilots must set the initial heading on the DG to match the compass before flight, and regularly cross-check compass and DG indications. After the heading is set, the gyroscope in the DG attempts to maintain its alignment with that initial setting. When the plane turns, the card with the compass headings rotates within the DG, showing the airplane’s current directional heading. The DG will maintain a steady indication of the plane’s heading that is not subject to the bobbing and weaving of a magnetic compass.

Vertical speed indicator (VSI)
The VSI is especially useful to pilots for identifying vertical trends. Since the altimeter is graduated in large quantities, the smallest indication usually being 20 feet, holding altitude precisely is vastly simplified by a glance at the VSI, which may depict an up or down trend not yet visible on the altimeter.

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