2A-27-60: Flaps System
1. General Description:
The flaps system for the Gulfstream IV provides a means for the flight crew to
control the position and movement of the trailing edge flaps, in order to allow
steeper approach and climb angles, and lower takeoff and landing speeds.
The flaps are manually operated, electrically controlled, hydraulically powered,
mechanically actuated airfoils located on the inboard trailing edge of the left and
right wings. Designed as single-slotted Fowler-type flaps, they ride on rollers
along four curved flap tracks attached to the rear beam of each wing.
Mechanical actuators (commonly referred to as screwjacks), driven by a hydraulic
motor through a central gearbox, extend and retract the flaps. As the screwjacks
extend the flaps, the flaps move aft and downward to increase wing area and
camber.
An asymmetry protection system monitors flap position to prevent unequal
movement. If one flap moves further than the other, the protection system stops
flap movement by shutting off the hydraulic pressure source to the hydraulic
motor.
A FLAP handle, located on the center pedestal, controls normal flap extension
and retraction to four positions. Emergency flap control is provided by an EMER
FLAP handle located on the copilot’s right console. Flap position is displayed on
the FLAP / STAB position indicator located on the copilot’s skirt panel.
Extending the flaps normally results in a nose pitch down movement as the flaps
increase wing lift. To compensate for nose pitch down, the horizontal stabilizer
leading edge moves down corresponding to flap extension. Horizontal stabilizer
operation is described in Section 2A-27-50, Horizontal Stabilizer System.
Units and components in the flaps system receive electrical power from the
Essential DC bus. The primary source of hydraulic power for the system is the
Combined hydraulic system, with the Utility hydraulic system available as a
backup source. If both the Combined and Utility hydraulic systems are not
available, the Auxiliary hydraulic system can be used to position the flaps using
the AUX pump.
The flap system is composed of the following subsystems, units and components:
• Flap handles
• Flap shutoff valve
• Flap selector valve
• Hydraulic motor and central gearbox
• Flap actuators
• Flap follow-up switches
• Flap asymmetry protection system
• Flap position indication system
• Aircraft configuration warning system
• Flap control circuit breakers
A description of flap operation is also provided in this section.
2. Description of Subsystems, Units and Components:
(See Figure 17 through Figure 20.)
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-27-00
Page 55
January 31/02
Revision 6
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