T-34C AIRCRAFT SYSTEMS FAMILIARIZATION
indicator shows whether the selected course will take you to or from the station. The
VOR/TACAN switch located above the CDI (or GPS cockpit - below the altimeter) allows
display of either TACAN or VOR information in the CDI (Figure 11-3).
A transponder is located in both cockpits on the right console outboard of the multifunction panel.
Each transponder is identical and operates independently of the other. The operating transponder
will be in the cockpit having possession of avionics command. When interrogated by ground
search radar, the transponder automatically provides the ground controller with identification,
position tracking, altitude, and emergency identification information. The system is comprised of
the two transponders with their integral control panels and two antennas, i.e., there are no
components in the avionics compartment. The blade type antennas are on the bottom of the
fuselage with one beneath each cockpit. A function selector in the upper left corner of the control
panel is labeled OFF, SBY, ON, ALT and TST and has the following functions (Figure 11-5).
OFF................ No power to transponder.
SBY ............... Warmup. Set inoperable. Selection of ON, ALT or TST not allowed for 20
ON ................. Transmits identification and position tracking, but no altitude information.
ALT ............... Transmits identification, position tracking and altitude information.
TST ................ Illumination of REPLY lamp confirms transponder operation.
Four code selector switches allow the setting of 4096 possible codes. Each selector can set any
number 0-7. The code assigned by Air Traffic Control system will identify your aircraft. A push-
button switch with an integral green light is labeled REPLY, IDENT, DIM. The green REPLY
light flashes on and off automatically in response to ground radar interrogation when ON or ALT
is selected. If the button is depressed, the IDENT function activates. The requirement for IDENT
is initiated by the ground controller to assist in identifying your aircraft. When depressed, the
REPLY lamp goes to steady illumination for 20 seconds and a distinct reply appears on the
ground radar scope. At the end of the 20 seconds, normal response to interrogation resumes. The
DIM feature controls the intensity of the REPLY lamp.
Emergency Locator Transmitter
The ELT, located at the rear of the left console in the front cockpit, transmits a location homing
signal in time of emergency usually associated with a downed aircraft. Operation of the ELT is
controlled by a function switch labeled OFF, ON. The ON position turns the set on and
emergency transmissions are started. With OFF selected, the ELT will transmit only when
activated by a rapid deceleration force. When activated, the ELT transmits a line-of-sight signal
on 121.5 and 243.0 MHz. Batteries provide power for a minimum of 48 hours (Figure 11-1.)