Gulfstream G550 Operating Manual Download

Page: 49 / 94

(The operation of the aircraft flaps is described in the following sections.)
The FCU moves the horizontal stabilizer to compensate for the change in
the center of lift on the wing as flaps are extended. The FCU processor
schedules stabilizer position according to the following table:

Flap Position

Horizontal Stab Position

0° (flaps up)

−1.5°

.1°

10°

−2.7°

.1°

20°

−3.6°

.1°

39° (flaps down)

−4.6°

.1°

If a malfunction such as a flap asymmetry prevents the flaps from moving,
the FCU cancels movement of the horizontal stabilizer. The horizontal
stabilizer remains operative in the EMER STAB mode, and can be
positioned with the cockpit yoke trim switches.

If the EMER STAB mode is used to control the horizontal stabilizer, and
subsequently control of the horizontal stabilizer is returned to normal
operation (by deselecting the ARM state with the EMER STAB pushbutton),
the FCU will move the stabilizer to align with the existing flap setting
according to the processor internal schedule. During this process, an
advisory (blue) CAS message of “Stabilizer Syncing A - B” will be
displayed.

C. Wing Flaps:

A Fowler-type flap is installed on the trailing edge of each wing. Fowler
flaps, when extended, move aft and down from the wing trailing edge,
increasing wing area to generate additional lift for low speed flight. Fowler
flaps have a cross-section similar to wing airfoils, and by deploying aft of
the wing trailing edge, open up a gap between the wing and flap allowing
additional airflow over the flap. RVDTs are installed on the outer section of
the flaps to provide position feedback information to the FCU.

Flap extension and retraction is controlled with the flap handle on the
copilot side of the center console, shown in Figure 16. Each flap extends
back from the wing along four tracks with rollers attached to the flaps
moving within the tracks. The two middle track installations on each wing
also contain the jackscrews that extend or retract the flaps. The jackscrews
on each wing are driven by torque tubes installed on the aft section of the
wing running inboard to a hydraulic Power Drive Unit (PDU) located in the
main landing gear wheel well. The PDU is powered by the left hydraulic
system and uses a gearbox to transmit hydraulic pump rotation to the
torque tubes. If the left hydraulic system is not available due to a
malfunction, the auxiliary (AUX) hydraulic pump or the Power Transfer Unit
(PTU) can be used to pressurize left hydraulic system fluid to operate the
PDU. A schematic of the wing flaps system operation is shown in Figure
15.

The direction of PDU rotation is controlled by two solenoid valves, one to
extend the flaps and the other to retract the flaps. Each solenoid valve has
dual control channels (A and B) from the FCU. The FCU compares the
position of the RVDTs on the flap handle in the cockpit to the position
indicated by the flap RVDTs, and signals the extend or retract solenoid
valve on the PDU, powering the PDU in the required direction to extend or

OPERATING MANUAL

PRODUCTION AIRCRAFT SYSTEMS

2A-27-00

Page 49

August 14/03

Title Page

Prev Page

Next Page

TOC