BY ORDER OF THE SECRETARY OF THE AIR FORCE AIR FORCE ...

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AFMAN 11-217V1 3 JANUARY 2005
Figure 3.4. Factors Influencing Cross-Check Techniques.
3.3.6. Factors Influencing Instrument Cross-Checks (Figure 3.4).
3.3.6.1. Instrument’s Response to Attitude or Power Changes. A factor influencing
crosscheck technique is the characteristic manner in which instruments respond to
changes of attitude or power. The control instruments provide direct and immediate
indications of attitude or power changes.
3.3.6.2. Performance Instrument Lag. Changes in the indications on the performance
instruments will lag slightly behind changes of attitude or power. This lag is due to
inertia of the aircraft and the operating principles and mechanisms of the performance
instruments. Therefore, some lag must be accepted as an inherent factor. This factor
will not appreciably affect the tolerances within which you control the aircraft;
however, at times a slight unavoidable delay in knowing the results of attitude or
power changes will occur. Lag in the performance instruments should not interfere
with maintaining or smoothly changing the attitude or power indications. When the
attitude and power are properly controlled, the lag factor is negligible and the
indications on the performance instruments will stabilize or change smoothly. Do not
be lured into making a flight control movement in direct response to the lag in the
indications on the performance instruments without first referring to the control
instruments or allowing performance indications to stabilize. Sufficient reference to
the control instruments will minimize the effect of lag on the performance