cam arm
• Inertia in the build up of hydraulic pressures in the elevator actuator
• The one tenth (1/10) second delay in electrically latching the shut off
of hydraulic pressure
B. Elevator Disconnect Handle:
(See Figure 4.)
The mechanical torque tube beneath the cockpit connecting the pilot and
copilot yokes may be disconnected if a malfunction in one of the cable
connections, hydraulic actuators or elevators renders the respective
elevator inoperative. Disconnecting the torque tube prevents both elevators
from being disabled by a malfunction in one elevator linkage.
An elevator disconnect handle is located on the pilot side of the center
pedestal beneath a protective cover. The handle is connected by a cable to
a pin securing the two halves of torque tube together. Pulling out on the
disconnect handle removes the pin and allows each yoke to move
independently. If the elevator linkage malfunction has resulted in opposite
movement between the two yokes, making retraction of the mating pin
difficult, a power assist gas-spring cartridge may be activated to provide
additional force to remove the pin. The power assisted disconnect is
activated by pulling a trigger beneath the disconnect handle, and provides
an upward lifting moment of thirty-three feet per second (33 ft./sec).
After the yokes have been separated, the malfunctioning elevator is
isolated and the operable elevator may be used to control the aircraft. with
manual or autopilot inputs. If it is discovered that separating the yokes
freed the previously malfunctioning elevator linkage, the yokes may be
reconnected by pushing in on the disconnect handle when the yokes are
aligned, provided that the power assist disconnect was not used. A reset of
the yoke torque tube coupling is not possible without special maintenance
tools after activation of the power assist disconnect.
C. Pitch Trim System:
(See Figure 4 through Figure 6.)
Each elevator has a trim tab installed on the trailing edge. The trim tabs are
manufactured from the same graphite-epoxy material as the elevators, but
incorporate a ceramic heating element that is continuously electrically
powered to maintain a temperature of one hundred seventy-five degrees
Fahrenheit, plus or minus twenty degrees (175°F±20) around the tab
actuator linkage. Elevator trim heat is powered by 115V AC from the right
main bus. The trim tabs have a range of movement of twenty-two degrees
(22°) trailing edge down (aircraft nose up) to eight degrees (8°) trailing
edge up (aircraft nose down). Limit switches are installed at the travel limits
that will prompt the display of Crew Alerting System (CAS) messages
notifying the crew that the elevator trim tabs are at maximum displacement.
If a trim limit message is displayed while the autopilot is engaged, extreme
care should be taken prior to disengaging the autopilot. An abrupt attitude
change will occur if trim displacement is not moderated prior to
disengaging the autopilot.
Operation of the trim tabs employs aerodynamic force to maintain the
elevator in the desired position. As the trim tab is moved from the neutral
position (faired with the elevator) into the airstream, the air impinging on
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-27-00
Page 11
August 14/03
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