1. Failure Warning Flag
2. Altitude Alert Annunciator
3. Altitude Scale
4. Barometric Pressure Counter Drum
Indicator Window (inches of Mercury)
5. Barometric Pressure Counter Drum
Indicator Window (Millibars)
6. Manual Barometric Pressure Setting
7. Altitude Indicator Needle
8. Counter Drum Altitude Display
Figure 3C-143. Pilots Altimeter (BA-141)
In the event of a total ac and dc electrical
power loss, the warning flag will be in view,
the altimeter will be inoperative, and the
indicated altitude will remain as existed at
the time of failure.
(2) Altitude Alert Annunciator. The altitude
alert annunciator illuminates to provide a visual
indication that the aircraft is within 1000 feet of the pre-
selected altitude during the capture maneuver and
extinguishes when the aircraft is within 250 feet of the
annunciator on upper right corner of pilot's altimeter
and ALT ALERT annunciator in the annunciator block
above the copilot's airspeed indicator will illuminate if
the aircraft departs more than 250 feet from the
selected altitude, and will extinguish when the aircraft
has departed more than 1000 feet from the selected
(3) Altitude Scale. The face of the altimeter
has a marked scale from 0 to 9 in 20-foot increments.
Indicator Window (Inches of Mercury). This window
indicates barometric pressure as set by manual
barometric pressure setting knob.
Indicator Windows (Millibars).
pressure and millibar counter-drum indicator windows,
display barometric pressure in millibars.
Knob. The manual barometric pressure setting knob,
placarded BARO, is used to set the barometric
pressure and millibar counter-drum indicators.
(7) Altitude Indicator Needle. The altitude
indicator needle points to the altitude on the pointer
(8) Counter-Drum Altitude Display. The
counter drum displays altitude and is marked in 20-foot
annunciated by a black and white crosshatch on the
left-hand digit position of the counter display.
c. Operating Procedure.
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
1. BARO knob Set desired altimeter
2. Warning flag Check not visible.
3. Needle indicator Check operation.