air data computer. Altitude is displayed by a 10,000 foot
counter, a 1000 foot counter, a 100 foot counter, and a
single needle pointer (coupled with the 100 foot counter)
which indicates hundreds of feet on a circular scale in
20 foot increments. Below an altitude of 10,000 feet, a
diagonal striped symbol will appear on the 10,000 foot
counter. The barometric pressure knob allows ground
supplied altimeter setting to be manually set. Altimeter
setting is displayed in inches of mercury and millibars on
Controls, Indicators and Functions.
Failure warning flag. The failure
warning flag, placarded OFF, comes into view when the
error between the altitude displayed and the signal
received is too great, the air data computer goes invalid,
or the barometric altimeter loses primary power.
Altitude alert annunciator. The altitude
alert annunciator, placarded ALT, is illuminated when
aircraft is within 1000 feet of preselected altitude during
capture maneuver and extinguishes when aircraft is
within 250 feet of preselected altitude. After capture,
annunciator will illuminate if aircraft departs more than
250 feet from the selected altitude.
Altitude scale. Used in conjunction
with altitude indicator needle to indicate aircraft altitude
in hundreds of feet Subdivided into 20 foot increments.
indicator (inches of mercury). Indicates barometric
pressure in inches of mercury that has been set by the
barometric pressure setting knob.
indicator (millibars). Indicates barometric pressure in
millibars that has been set by the barometric pressure
Used to manually set barometric pressure displayed in
the MB pressure displayed in the IN HG and MB
Altitude indicator needle. Used in
conjunction with altitude scale to display aircraft altitude
in hundreds of feet.
thousands, and hundreds of feet above sea level.
Altimeter Operating Procedure.
Barometric pressure setting knob - Set
desired altimeter setting.
Failure warning flag - Check not
If the altimeter does not read within 70 feet
of field elevation, when the correct local
barometric setting is used, the altimeter
needs calibration or internal failure has
occurred. An error of greater than 70 feet
also nullifies use of the altimeter for IFR