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closing a normally open flight power shutoff valve. The flight power shutoff
valve is a mechanically operated shutoff valve located between the
Combined and Flight hydraulic system pressure sources and the elevator
actuator (as well as the aileron, rudder and flight / ground spoiler actuator)
pressure lines. The valve consists of two mechanically connected but
hydraulically isolated sections. A controlex cable connects the valve to a
FLIGHT POWER SHUT OFF handle located on the left aft side of the
cockpit center pedestal. See Figure 8.
Moving the FLIGHT POWER SHUT OFF handle up from its stowed
(horizontal) position to the vertical position mechanically closes the flight
power shutoff valve. With the valve closed, operating pressure is removed
from the actuator, allowing the piston to idle.
The resultant advantage of the flight power shutoff provision is the ability to
bypass a malfunctioning actuator (such as would be the need in the
unlikely event of an actuator jam) and manually fly the aircraft. Although
control column effort and response time to inputs are increased while in
manual reversion, the aircraft remains capable of positive and harmonious
control.
E. Pitch Trim System:
(See Figure 5 and Figure 9.)
(1) Elevator Trim Tabs:
A trim tab is installed on the trailing edge of each elevator. The tabs
are mechanically positioned through cable-driven drum actuators
located in each elevator. The trim actuators can be operated
manually or electrically as described in the following paragraphs.
Elevator trim tab travel ranges from 22 ±1° tab trailing edge down
(aircraft nose up) to 8 ±1° tab trailing edge up (aircraft nose down).
(2) Manual Trim Control:
Manual control of pitch trim is accomplished by an interconnected
manual trim control wheel set. A trim control wheel and elevator trim
scale are provided on each side of the cockpit center pedestal. With
electric pitch trim disengaged, moving either manual trim control
wheel adjusts pitch trim to the desired setting; the opposite wheel
moves in unison. With electric pitch trim engaged, both manual trim
control wheels move in unison corresponding to the amount of
electric pitch trim movement. Each elevator trim scale range is
incremented to a maximum of 22 units aircraft nose-up (22 ±1° tab
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-27-00
Page 9
October 11/02
Revision 8
trailing edge down) and 8 units aircraft nose-down (8 ±1° tab trailing
edge up).
Mechanical stops limit elevator trim wheel movement to 6.6 turns
from each stop. A shear rivet installed in the cockpit portion of the
system prevents application of excessive force by shearing at
approximately 31 pounds of force.
(3) Electric Pitch Trim:
Located on the pilot’s flight panel, the PITCH TRIM ENG / DISENG
switch engages or disengages the electric pitch trim. Pitch trim is
also engaged whenever the autopilot is engaged. With electric pitch
trim engaged (amber DISEN switch legend extinguished), pitch trim
can be adjusted through use of a split-half pitch trim switch
(sometimes referred to as a “beep” switch) installed on the outboard
grip of each control wheel. Switch positions are labeled NOSE
DOWN and NOSE UP. Inadvertent actuation of pitch trim, including
runaway, is minimized through the split-half switch design. In order
for the pitch trim to be actuated, both halves of the switch must be
simultaneously moved in the same direction.
Movement of the electric pitch trim switch to NOSE DOWN or NOSE
UP actuates the autopilot elevator trim servo. The trim servo is
connected to the manual trim control wheel set by a chain. The
chain-driven movement of the manual trim control wheel set in turn
positions the elevator trim tabs.
The electric pitch trim is normally checked by the flight crew on the
first flight of the day, during the Before Starting Engines checklist. A
check usually consists of running the elevator trim fully up, then fully
down, using normal methods, i.e., using both halves of the switch
simultaneously. This is followed by attempting to run the pitch trim
using each half of the switch alone. Any movement resulting from
using either half of the switch alone indicates a malfunction that
should be corrected before flight. The check is concluded by setting
pitch trim for the takeoff Center of Gravity (CG) condition as
determined using the Airplane Flight Manual.
(4) Elevator Trim Tab Actuator Heat System:
Electrically-heated elevator trim tab actuators are incorporated on
airplanes SN 1380 and subsequent and SN 1000 through 1379
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湾流4操作手册 Gulfstream IV Operating Manual 2(9)
