Embraer EMB145 Operation Manual page 2007

FLIGHT CONTROLS
PITCH TRIM CHANNELS PRIORITY
Command priorities are: LH switch actuation overcomes the RH switch
actuation, which, in turn, overcomes the autopilot. There is no priority
with respect to the actuation of the main pitch trim switches and the
backup pitch trim switches, the first being commanded taking priority.
The main and backup pitch trim switches should not be commanded
simultaneously. For the case of a simultaneous command of both
channels, there is an specific logic inside the HSCU:
For airplanes equipped with an HSCU P/N 362100-1009, -5009 or
newer, the message PIT TRIM 1 (2) INOP will be displayed on the
EICAS, associated to the second switch commanded. This message
will disappear around 4 seconds after the second pitch trim switch is
released.
For airplanes equipped with an HSCU P/N 362100-1007, if the
switches are commanded in different directions, the secondly
commanded channel will become inoperative for the remainder of
the flight and the respective message, PIT TRIM 1 (2) INOP, will be
displayed on EICAS.
PITCH TRIM SYSTEM PROTECTION
Switch Protection
When only one half of the main control wheel trim switch or backup
trim switch is commanded for more than 7 seconds continuously, the
control unit will recognize that one half of the switch is failed stuck at
the commanded position and will disregard any other command
coming from that faulty switch.
NOTE: For airplanes equipped with HSCU -1009 or -5009 or newer
and AWU -5 a TRIM voice message is provided to alert pilots
that just one half of switch is being commanded and those
equipped with HSCU -1009 or -5009 or newer and EICAS
version 18 and on the messages PTRIM CPT SW FAIL,
PTRIM F/O SW FAIL and PTRIM BKP SW FAIL will be
displayed on the EICAS.
Runaway Protection
A quick-disconnect button on each control wheel allows disconnection
from the entire pitch trim system. In case of a runaway horizontal
stabilizer, the button must be kept pressed until a definite
disengagement is accomplished through the cutout buttons on the
control pedestal.
Page
2-13-10 8
AIRPLANE
OPERATIONS
MANUAL
Code
01 REVISION 38