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Flight Management System (FMS) for the Agusta AW139/AB139 Helicopter
VERTICAL NAVIGATION
VNAV is the function in the FMS that provides vertical flight information
to the operator. Using FMS VNAV, the operator defines vertical profile
information used by the operator to assist in control of the aircraft.
VNAV is advisory only and provides no automatic vertical control
functionality. FMS VNAV is used for all phases of flight. In addition,
descents are set up for a path mode (similar to glideslope) to cross
waypoints at a specified altitude. The two main areas for VNAV
information to be displayed are the ACTIVE FLT PLAN page and
PROGRESS 2 page.
General VNAV Rules
VNAV does not function until all PERFORMANCE INIT information
D
has been programmed into the MCDU and the altitude preselector
has been turned up.
VNAV guidance is available for all phases of flight.
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The pilot must set the altitude preselector only to ATC cleared
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altitudes.
VNAV keeps the aircraft as high as possible, for as long as possible.
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VPATH angles are from 1_ to 6_.
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Path guidance is always provided during VPATH descents unless
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the FMS transitions to speed reversion. In this condition, the FMS
transitions out of VPATH.
Default descent angle is part of performance initialization. Changing
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of the default angle is permitted by the crew after the angle is
displayed for each waypoint.
When the altimeter is adjusted for the height above the ground (Q
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to be displayed rather than sea level, VNAV must not be used.
VNAV Submodes
VNAV Flight Level Change (VFLCH) -- This mode is vertical flight
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level change. When applicable, aircraft speed is controlled by the
flight guidance computer (FGC) by the pitch of the aircraft. This
mode is also referred to as speed on elevator. The speed command
is displayed on ACTIVE FLIGHT PLAN page 1 and the guidance
panel (when supported). For most operations, the autothrottle is set
to climb power rating for climbs and idle for descents. Exceptions
are when climbing or descending only a short distance. In this case,
the throttle is set to less than climb power or more than idle to avoid
abrupt changes. Moving the throttle during VFLCH changes the
aircraft pitch and vertical speed. However, the aircraft speed
remains the same.
Flight Plan
7-24
Honeywell International Inc. Do not copy without express permission of Honeywell.
)
FE
A28- - 1146- - 181
REV 3 Mar 2009
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