Basic Instrument Scan for Airplane

Posted by Admin on

This is for emergency purposes only, and not intended to provide the reader with more than a rudimentary understanding of instrument flight. Proper planning and preflight checking can prevent the majority of accidental entry into IFR or minimal visibility flight conditions. But for those situations where you encounter weather that requires flight by reference to instruments, it is necessary that you understand their function and how to fly properly. Here are the basics of flying on instruments and the best methods for extricating yourself from the situation.

Upon encountering instrument weather conditions, continue to fly the airplane. Panicking and letting the airplane get into an uncontrolled attitude is one of the fastest ways to crash. Begin a regular scan of the instruments as soon as you encounter minimal visibilities and maintain the proper flight attitude. Then contact air traffic control (ATC). While this may seem like asking for trouble, ATC can help establish your position, direct you to an airport that may be in a more favorable weather situation, and keep you clear of other legal IFR traffic.

The primary reference instrument in IFR conditions will be the attitude indicator. Your scan will move to the directional gyro, the altimeter, and airspeed indicator, then back to the AI, essentially working a “T” pattern of instruments. The turn and bank indicator and the vertical speed indicator should also be checked periodically, but use of the other instruments will help you hold the desired attitude and heading. Avoid the tendency to focus on one instrument exclusively, normally the attitude indicator. Keep the scan smooth and constant. This will help you avoid blocking out important information regarding the airplane’s flight status.

Once you have established contact with ATC and have the scan working and the plane in the desired flight attitude, relax as much as possible. Students learning to fly the plane on instruments often establish a “death grip” on the control yoke. This prevents them from feeling the airplane and making smooth inputs on the controls. When flying on instruments, make a conscious effort to use small, smooth control inputs when making changes in bank, pitch, or direction. Pilots often fall into the trap of using too much control input for a given change, then overcompensating once they realize they have gone too far. It is not at all uncommon for pilots to bank well past 30 degrees, then realize as the plane reaches 45 degrees of bank that they are losing altitude, the airspeed is increasing, and they have flown past the heading they wanted to establish. This gets them overcontrolling in an attempt to get back to where they want to be. Be patient. Make small adjustments to the attitude and wait for a response on the other instruments. If a bigger change is needed, make it in increments. Use the AI like the view out the windshield, and note that very small adjustments there go a long way toward speed, altitude, and heading changes. When desired flight parameters are reached, keep the attitude constant. If you keep the control inputs small and scan the gauges rhythmically, you will notice the results of the control inputs and be able to make any needed corrections quickly and efficiently.

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