REVUE THOMMEN AG
CH-4437 Waldenburg
AD20 Standby Altimeter
Page 24 of 72
07-Sep-2009 Document No: AD-INSOP-800 Revision: 1.6
The following table shows the ARINC labels for various signals used for REVUE THOMMEN AD20
Standby Altimeter :
Label Signal Name Operational
Range 1)
Unit Resolution Update Rate
per s
203 Pressure altitude (1013.25
hPa)
-1000 ..+55,000 feet 1 16
204 Baro corrected altitude #1 -1000 ..+55,000 feet 1 16
212 Altitude Rate 0 .. 20,000 ft/min 16 16
217 Static pressure 0 .. +64 inHg 0.0009765 8
234 Baro Correction mb #1 700 .. 1050 mbar / hPa 0.1 8
235 Baro Correction inHg #1 20.67 .. 31.00 inHg 0.001 8
270 Discrete Word #1 -- -- -- 2
350 Maintenance Word #1 -- -- -- 2
Table 2-2 ARINC 429 Labels
2.3.1.4 Pointer Positioning
The pointer on the dial display of REVUE THOMMEN AD20 Standby Altimeter makes one revolution
(360 deg) for each 1,000 feet (meters) of altitude in reference to the circular scale graduated with 20
ft (meters) increments.
The pointer moves smoothly clock wise and counter clockwise around the dial as aircraft altitude is
increasing or decreasing respectively. When the aircraft altitude sensed and measured internally
exceeds the altitude indicated by the pointer by ± 2 ft (m). The pointer stops at indicated altitude level
when the current aircraft altitude overrides the altitude range design limit of the instrument [maximum
tolerance level (> 55,610 or < - 1,020 feet OR >55000 feet or < -1000 feet) is included in the range
limit].
2.3.1.5 Dial and Display
The analog dial pointer provides altitude information as required to supplement the digital display.
The dial when viewed from a point directly in front of and below the dial centre line, the same
graduations and markings are visible from an angle of 15 degrees. The value indicated on the pointer
is clearly visible and readable from all positions around the dial. The display provides a direct reading
of altitude in feet or meter (as per the scale selected) in a five digit LCD window with the provisioning
of integral lighting. The 1 foot (m) digit on the extreme right is normally displayed as a fixed zero. A
four digit display of barometric setting is also provided to display the setting in inHg or hPa (as per
the scale selected). The display of barometric pressure setting is not affected by altitude display
failures.
The display is consistent all the time with the uniformity of other panel displays and the integral
lighting of the cockpit.
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