Specifications

SECTION III
INSTRUMENTATION AND AVIONICS
MODEL 560
For a VOR approach (VAPP mode), the desired VOR frequency is selected on the NAV receiver, the
course bearing set on the EHSI, and the APR mode is selected on the flight director mode selector. The
green light will illuminate in the APR button and, if outside the capture limits, VAPP will illuminate in white
on the top left side of the EADI. HDG will annunciate in green in the top right side of the EADI.. When the
airplane maneuvers into capture range, HDG mode will cancel and VAPP will annunciate in green in the top
left side of the EADI. A white box will be drawn around the capturing mode for five seconds.
In both NAV and APP modes, a station passage feature is provided that incorporates bank angle limits
and a course hold (plus wind drift) mode. The station passage mode for enroute tracking (NAV mode) is of
long enough duration to provide smooth transition of a VOR station at any altitude. The station passage
mode for APP mode is of short duration to provide approach accuracy. This does not provide the degree of
ride smoothing that is present in the enroute case.
Autopilot coupling during VOR approaches is limited to airports at elevations at or below 3,300 feet.
Pilot flown approaches with flight director guidance may be conducted, however.
ILS APPROACH (LOC) OR (LOC GS)
With a localizer frequency selected in a NAV receiver, operation is similar to capturing and tracking a
VOR radial. Selecting APR on the mode control panel with a localizer frequency tuned, arms both the LOC
and GS modes and engages HDG, if not previously selected and the airplane is outside the capture
parameters of the mode. It is imperative that the APR button be pressed when the airplane is within less
than 90 degrees of the final approach course of the published ILS course; otherwise the system will assume
that a back course is being selected, and will so annunciate. HDG will be displayed in green at the top right
of the EADI and the green light in the APR button of the mode selector will illuminate; LOC and GS will be
illuminated in white on the upper left and right, respectively, of the EADI. When inside the LOC capture
limits, LOC will illuminate in green at the top left of the EADI and HDG will extinguish. At glideslope capture
(approximately 1/2 dot), GS will illuminate in green on the EADI. During transition to both the LOC and GS
capture modes a white box will be drawn around the respective mode annunciations. During ILS
approaches, the FD gain is progressively adjusted during the approach using GS deviation, radio altitude,
and middle marker passage for gain programming. If the radio altimeter is not operational, this function is
performed as a function of glideslope capture and middle marker passage.
The capture limits for VOR and LOC captures are variable depending on DME distance, speed and
intercept angle. Glideslope capture is locked out until localizer capture occurs. If the localizer mode
becomes invalid for any reason, the glideslope mode will also be cancelled.
The glide slope indicator, located on the right side of the EADI presentation, is green unless there is a
cross-side selection, in which case it will be yellow.
BACK COURSE LOCALIZER APPROACH (BC)
A back course localizer approach capability is provided using either flight director or autopilot or both.
With a localizer frequency set in the selected NAV, selecting APR on the mode selector arms the
system for a back course localizer approach. The front course of the ILS must be set into the EHSI to give
proper indications on the course deviation bar and for the flight director computer to compute correct back
course corrections during the approach. If the back course is set on the EHSI the command bars and
autopilot will be given incorrect steering commands. When APR is selected on the mode selector, the
green light in the button will illuminate and BC will be annunciated in white on the left top side of the EHSI.
HDG may illuminate in the top right side of the EADI if the airplane is outside of capture parameters for the
mode and heading mode engages in order to effect capture. It is imperative that the APR button be
pressed when the airplane is within less than 90 degrees of the final approach course of the published back
course; otherwise the system will assume that a front course is being selected, and will so annunciate.
When the back course is captured, BC will be illuminated in green on the top left side of the EADI and HDG
will extinguish if heading mode was engaged to accomplish intercept. The system will not annunciate the
back course mode until localizer capture occurs and the system confirms that the heading is in excess of
90 degrees from the selected (front) course.
I 3-44 Configuration AA 56OMB-01