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Flight Management System (FMS) for the Agusta AW139/AB139 Helicopter
Cruise is flown by the autopilot in the altitude hold mode (ALT). From
cruise, a climb or descent is executed at any time by setting the
altitude preselector to the desired altitude and pushing the IAS
button. There is a 2 to 3 second delay before VNAV resets the
altitude target to the altitude preselector or next waypoint altitude
constraint (whichever is closer).
NOTE:
When in ALT, the flight guidance system (FGS) touch
control steering (TCS) function is used to maneuver the
aircraft. However, when TCS is released, the aircraft
returns to the original ALT altitude.
Automatic changes from cruise are conducted for bottom--of--step
climb (BOSC) and TOD points. In both cases, the altitude
preselector must be properly set (that is., above the current altitude
for BOSC and below current altitude for TOD). When the altitude
preselector remains at the current altitude, the aircraft remains in
cruise as the points are passed.
Top of Descent (TOD) -- The TOD is the location where the aircraft
D
commences a descent. The TOD is displayed on the MFD when in
range, but is always displayed on the PROGRESS pages. Only one
TOD waypoint is permitted at a time.
Descent -- The transition to descent is automatic, assuming the
D
altitude preselector is set lower than the present altitude. On
reaching the TOD, VNAV initiates either a VFLCH or VPATH
descent.
— Speed Descent (VFLCH) -- A speed descent is provided when
no altitude constraints exist in the flight plan during the descent.
The TOD is calculated to place the aircraft at 1500 ft above the
destination 10 miles prior to the destination. Also, the TOD is
based on any speed constraints in the descent, such as slowing
to 250 kts below 10,000 ft.
The pilot initiates a descent anytime by setting the altitude
preselector to a lower altitude and pushing IAS on the guidance
panel. Following an intermediate level off at the altitude
preselector value, the descent is resumed by the pilot dialing
down the altitude preselector and pushing the IAS button again
on the guidance panel.
— Path Descent (VPATH) -- A VPATH descent is provided when
an altitude constraint is in the descent portion of the active flight
plan. The path angle associated with the constraint is either a
default angle computed by the FMS, procedure specified, or
pilot--entered.
Flight Plan
7-28
Honeywell International Inc. Do not copy without express permission of Honeywell.
A28- - 1146- - 181
REV 3 Mar 2009
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