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of Federal Regulations (14 CFR) part 23 for IFR flight, redundant instrumentation is required for electronic displays of airspeed, altitude, and attitude indications. Dedicated standby instruments or dual independent pilot flight displays (PFD) must be installed in the aircraft. Many of the light aircraft equipped with glass cockpits typically share the same pitot-static inputs for the backup instrumentation. Since both systems are receiving the same input signals, both may be adversely affected by obstructed or blocked pitot tubes and static ports making redundancy much less than desired. Some manufacturers combine both the air data computer (ADC) and the attitude and heading reference system (AHRS) functions so that a blockage of the input system may also affect the attitude display. 

With conventional instrumentation, the design and operation are similar regardless of aircraft or manufacturer. By comparing information between the six conventional instruments, pilots are able to diagnose common failure modes. Instrument failure indications of conventional instruments and electronic flight displays may be entirely different, and electronic systems failure indications are not standardized. With the wide diversity in system design of glass cockpits, the primary display and the backup display may respond differently to any interruption of data input, and both displays may function differently than conventional instruments under the same conditions. 

It is imperative for pilots to obtain equipment-specific information in reference to both the aircraft and the avionics that fully prepare them to interpret and properly respond to equipment malfunctions of electronic flight instrument displays. Rapidly changing equipment, complex systems, and the difficulty or inability to simulate failure modes and functions can impose training limitations. Pilots still must be able to respond to equipment malfunctions in a timely manner without impairing other critical flight tasks should the need arise. 

## Abnormal Engine Instrument Indication 

The AFM/POH for the specific airplane contains information that should be followed in the event of any abnormal engine instrument indications. The table shown in Figure 17-11 offers generic information on some of the more commonly experienced in-flight abnormal engine instrument indications, their possible causes, and corrective actions. 

## Door Opening In-Flight 

In most instances, the occurrence of an inadvertent door opening is not of great concern to the safety of a flight, but rather, the pilot’s reaction at the moment the incident happens. A door opening in flight may be accompanied by a sudden loud noise, sustained noise level, and possible vibration or buffeting. If a pilot allows himself or herself to become distracted to the 

