Section 3 Display Symbology
3-70
IDU-450 EFIS Software Version 8.0H (Rotorcraft)
1
st
Ed Nov 2018
Digital readout of AGL altitude is not displayed when it is greater than the
radar altimeter maximum valid altitude nor when it is invalid. The digital
readout of AGL altitude is not displayed when its source is barometric and
indicated airspeed is in the noise range (less than 20 KIAS) due to rotor
wash effects. When AGL altitude source is radar altitude, the digital readout
of AGL indication is smoothed to avoid jumpiness (Table 3-2).
Table 3-20: Analog AGL Indication Designed Parameters
Altitude Range Markings
Notes
0-1000’
Green-filled column
Thermometer fashioned
style. Top of column has a
widened area for better
registration against the scale
accordingly, so the widened
area disappears at AGL
altitudes greater than 1,000
feet (i.e., maximum analog
indication).
Scaling
0 to 100’
Linear
0’ AGL is at the bottom,
50’ AGL is at 25% of height,
100’ AGL is at 50% of
height, 200’ AGL is at 67%
of height, 500’ AGL is at
83% of height, and 1,000’
AGL is at full height
100’-1,000’ Logarithmic
Major Tick Marks
0’, 50’, 100’, 500’, and 1,000’
Minor Tick Marks
10’, 20’, 30’, 40’, 60’, 70’, 80’, 90’, 200’, 300’, and 400’
Color-filled column is not displayed when AGL altitude is invalid. Analog
indication of AGL altitude (including the scale) is not displayed, when its
source is barometric and indicated airspeed is in the noise range (less
than 20 KIAS) due to rotor wash effects.
3.7.10. Decision Height Indication
AGL indication includes a display of the set decision height altitude as
described in § 3.3.5.