MIL-DTL-9490E
3.1.2.4 Lateral acceleration and sideslip limits. Except for flight phases using direct side
force control, the following performance shall be provided whenever any lateral-directional AFCS
function is engaged. Lateral acceleration refers to apparent (measured, sensed) body axis
acceleration at the aircraft center of gravity.
3.1.2.4.1 Coordination in steady banked turns. Sideslip angle shall not be greater than 2
degrees and lateral acceleration shall not exceed 0.03g. While at steady bank angles up to the
maneuver bank angle limit reached during normal maneuvers with the AFCS engaged. For rotary
wing aircraft, only the lateral acceleration limit applies.
3.1.2.4.2 Lateral acceleration limits, rolling. Body axis lateral acceleration at the cg
shall not exceed ± 0.lg for aircraft with roll rate capability up to 30 deg/sec and ±0.2g for aircraft
with roll rate capability of 30 to 90 deg/sec. or +0.2g for aircraft with roll rates over 90 deg/sec.
These limits shall be satisfied for aircraft in essentially constant altitude flight while rolling
smoothly from one side to the other at bank rates up to the maximum obtainable through AFCS
modes.
3.1.2.4.3 Coordination in straight and level flight. The accuracy while the aircraft is in
straight and level flight shall be maintained within a sideslip angle of ±1 degree and a lateral
acceleration of ±0.02g at the cg, whichever is lower. For rotary wing aircraft, only the lateral
acceleration limit applies.
3.1.2.5 Altitude hold. Engagement of the altitude hold function at rates of climb or descent
less than 2,000 feet per minute (fpm) shall select the existing indicated barometric altitude and
control the aircraft to this altitude as a reference. The resulting normal acceleration shall not
exceed 0.2g incremental for MIL-F-8785 Classes I, II and III aircraft, or 0.5g incremental for
MIL-F-8785 Class IV aircraft. For engagement at rates above 2,000 fpm the AFCS shall not cause
any unsafe maneuvers. Within the aircraft thrust-drag capability and at steady bank angles, the
mode shall provide control accuracies specified in table I. These accuracy requirements apply for
airspeeds up to Mach 1.0. Double these values are permitted above Mach 1.0 and triple these
values apply above Mach 2.0. Following engagement or perturbation of this mode at 2,000 fpm or
less, the specified accuracy shall be achieved within 30 seconds. Any periodic residual oscillation
within these limits shall have a period of at least 20 seconds.
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