MIL-DTL-9490E
3.1.2.9.2 Glide slope mode. The pitch AFCS shall cause the aircraft to maneuver to
acquire the glide slope beam. Neither the position of the aircraft above or below the glide slope nor
vertical speed of the aircraft at time of mode selection shall be incorporated as a precondition for
mode engagement. When preconditions are satisfied, overshoot shall not exceed 0.16 degree (35
μa) of radial error from glide slope beam center when capturing from below the beam in level
flight at an altitude greater than 800 feet above the glide slope transmitter datum altitude in a
no-wind condition. The system shall exhibit a damping ratio of 0.085 or greater subsequent to the
first overshoot for the conditions defined. On a Category II ILS ground facility (including 10,000
foot runway) as defined in ICAO Annex 10, the pitch AFCS shall maintain the aircraft
glide slope antenna 2 σ position within 0.16 degree (35 μa) of beam center or within 12 feet of
beam center, whichever is greater, between the altitudes of 700 feet and 100 feet above the glide
slope transmitter datum.
3.1.2.9.3 Go-around mode. The automatic go-around mode shall be manually engaged
only. The AFCS shall be designed such that no single failure, or combination of failures not
extremely remote, will cause the aircraft to maneuver to increase the rate of descent upon engaging
the go-around mode. If the go-around mode is designed for concurrent operation with
other automatic control systems, a single switch location or pilot action shall engage all systems
into the appropriate mode for go-around. Should one or any combination of concurrently
operating automatic control systems be inoperative at the time of AFCS go-around mode
engagement, the AFCS shall comply with the performance requirements based on normal
go-around procedures including manual management of thrust, flaps, and landing gear.
3.1.2.9.3.1 Pitch AFCS go-around. The pitch AFCS shall cause the aircraft to smoothly
rotate sufficiently to establish a positive rate of climb such that the aircraft will not intersect the
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obstacle clearances planes defined in FAA Advisory Circular 120-29 more often than 1 in 10
events for the wind conditions specified in 3.1.2.9, and including high altitude, hot day conditions
as defined by the procuring activity. In the event of inadvertent loss of an engine just prior to or
during automatic go-around, the system shall not cause the aircraft to approach stall within 30
seconds of mode engagement, based on design approach speed. If operating procedures require the
mode to be disengaged upon inadvertent loss of an engine, a timely warning shall be provided for
the pilot to initiate the disengage procedure. Disengagement under this condition shall be
accomplished manually.
3.1.2.9.3.2 Lateral-heading AFCS go-around performance standards. The lateral-heading
AFCS shall maintain the aircraft 4 σ position within the lateral boundaries of the obstacle
clearance planes during wind conditions as specified in 3.1.2.9. This capability shall be maintained
in the event of the most critical engine failure just prior to or during automatic go-around. If
normal procedure is to disengage the go-around mode after inadvertent loss of one engine, under
the wind conditions cited, a pilot of normal skill shall be able to recover airplane heading such that
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intersection with the obstacle-clearance planes will occur no more than 1 in 10 events during
recovery.
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