MIL-DTL-9490E
2.4 Order of precedence. In the event of a conflict between the text of this document and
the references cited herein, the text of this document takes precedence. Nothing in this document,
however, supersedes applicable laws and regulations unless a specific exemption has been
obtained.
3. REQUIREMENTS
3.1 System requirements. The FCS shall comply with the following requirements.
3.1.1 MFCS performance requirements. The MFCS shall comply with applicable general
flying quality requirements of MIL-F-8785 or MIL-F-83300 and the special performance
requirements of the procurement detail specification.
3.1.2 AFCS performance requirements. When the following AFCS functions are used,
the following specified performance shall be provided. Unless otherwise specified, these
requirements apply in smooth air and include sensor error. Except where otherwise specified, a
damping ratio (see 6.6.16) of at least 0.3 critical shall be provided for nonstructural AFCS
controlled mode responses. Specified damping requirements apply only to the response
characteristics for perturbations in order of magnitude greater than the allowable residual
oscillation.
3.1.2.1 Attitude hold (pitch and roll). Attitudes shall be maintained in smooth air with a
static accuracy of ±0.5 degree in pitch attitude (with wings level) and ±1.0 degree in roll attitude
with respect to the reference. RMS attitude deviations shall not exceed 5 degrees in pitch or 10
degrees in roll attitude in turbulence at the intensities specified in 3.1.3.7. When using a flight
controller (turn knob) the aircraft shall return to a wings level attitude when the turn control is
placed in the detent position. Accuracy requirements shall be achieved and maintained within 3
seconds of mode engagement for a 5 degree attitude disturbance for MIL-F-8785 Class IV aircraft,
and within 5 seconds for MIL-F-8785 Classes I, II and III aircraft.
3.1.2.2 Heading hold. In smooth air heading shall be maintained within a static accuracy of
± 0.5 degree with respect to the reference. In turbulence, RMS deviations shall not exceed 5
degrees in heading at the intensities specified in 3.1.3.7. When using a flight controller, heading
hold shall automatically engage as the controller is returned to the detent position.
3.1.2.3 Heading select. The aircraft shall automatically turn through the smallest angle to
any heading selected or pre-selected by the pilot and maintain that heading to the tolerances
specified for heading hold. The contractor shall determine a bank angle limit which provides a
satisfactory turn rate and precludes impending stall. The heading selector shall have 360 degrees
control. The aircraft shall not overshoot the selected heading by more than 1.5 degrees with flaps
up or 2.5 degrees with flaps down. The roll rate shall not exceed 10 deg/sec and roll acceleration
shall not exceed 5 deg/sec/sec for MIL-F-8785 Class I, II and III aircraft, or double these values for
MIL-F-8785 Class IV aircraft.
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