Garmin G3X Installation Manual page 543

For certain aircraft types, maximum airspeed is additionally limited by true airspeed (TAS). A secondary
airspeed limit expressed as true airspeed may optionally be configured using the VNE (TAS) field. This
airspeed is marked on the PFD airspeed tape with a second red color band, which shows the equivalent
indicated airspeed at which the aircraft's true airspeed will exceed the configured true airspeed limit value.
At low altitudes where true and indicated airspeed are similar, the PFD airspeed tape will show only the
indicated VNE limit. At higher altitudes where true airspeed increases, a second red color band will begin
to appear on the PFD airspeed tape to indicate the point where the aircraft will exceed the true airspeed
limit at the current pressure altitude.
In this example, the aircraft's VNE values have been configured as 205 knots indicated airspeed, and 270
knots true airspeed. At high altitudes, the aircraft can reach the true airspeed limit even if its indicated
airspeed is below the normal indicated VNE "red line". The second red band on the PFD airspeed tape
alerts the pilot to this condition.
A third way to configure the aircraft's maximum airspeed limit is to enter a value for Maximum Operating
Mach Number (MMO, see Section 31.4.7). As with TAS-based VNE, the value for MMO will be
displayed on the PFD airspeed tape using a second red band that shows the equivalent indicated airspeed at
which the aircraft's Mach number will exceed the configured maximum Mach number. At high altitudes,
the aircraft can reach the maximum Mach limit even if its indicated airspeed is below the normal indicated
VNE "red line". The second red band on the PFD airspeed tape alerts the pilot to this condition
190-01115-01 G3X/G3X Touch Installation Manual - GDU 37X Config and Post Install Checkout
Rev. AA Page 31-91