PRIMUSr 1000 Integrated Avionics System
A28--1146--112--00
8-29
Modes of Operation
The SPD mode is basically an airspeed mode, however, it differs from
a standard IAS or Mach mode in the following ways:
D Although SPD mode (in the long term), tracks the referenceairspeed,
short--term emphasis is on vertical speed. This minimizes vertical
speed excursions due to disturbances or large airspeed changes.
D Vertical operations are monitored to prevent the aircraft from flying too
slowly. Below 120 knots, the vertical mode is overridden and is
replaced by SPD hold mode. This is underspeed (MIN SPD)
protection.
D Allverticaloperationsmustbemonitoredtopreventtheaircraftfrom
exceeding V
mo
/M
mo
. If, however, V
mo
/M
mo
is exceeded, the flight
guidancesystemswitchestotheSPDholdmode.This isoverspeed
(MAX SPD) protection.
NOTE: The only annunciation of MIN SPD or MAX SPD
submodes is displayed on the left side of the attitude
director indicator (ADI).
The SPD mode isannunciated on the PFD by a green IASor MACHat
the vertical capture location, as shown in figure 8--23.
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