Figure 16-40.--Speed brake control system.
Wingtip Type
handle is released. If electrical power is applied while
the manual override handle is actuated, the system will
The wingtip speed brake system is an electrically
remain in the position selected by the handle. If the
controlled and hydraulically operated system. It
handle is released, the system actuates to the position
operates either alone or with the fuselage speed brakes.
selected by the control switch on the throttle lever. The
See figure 16-41.
speed brakes cannot be stopped at intermediate
positions between fully closed and fully open. The
The wingtip brake consists of a set of trailing edge
restrictor in the open line restricts return fluid flow
surfaces for each wing. The lower half attaches to the
from the actuating cylinders when the speed brakes are
wing structure with two external fixed hinges. The
being closed.
upper half is attached to the wing at the same wing
station with two adjustable tension lengths. An
If the hydraulic system fails, the check valve in the
interconnecting hinge between the upper and lower
pressure line traps pressure between the control valve
halves provides a common connection point for the
and the actuating cylinders. If the speed brakes are
actuating cylinders. The hinge provides symmetrical
open, this pressure will hold them open. If the speed
deflection of upper and lower panels. Each panel can
brakes are actuated to the closed position, the pressure
open up to 60 degrees for a total angle of 120 degrees
in the system will shift the primary slide in the control
for each wingtip brake. When retracted, they lie flush
valve. This movement will relieve the trapped pressure
with the wing surface. They can extend and hold at any
and allow the speed brakes to close from the air load
angle between 0 and 60 degrees, depending upon the
against them.
amount of aerodynamic braking desired.
A blowback relief valve, installed in the hydraulic
A mode selector switch permits simultaneous or
return line, allows for automatic retraction of the speed
independent operation of the wingtip and fuselage
brakes under high air loads. When the speed brakes are
speed brakes, with the speed brake control switch
open, the force of the airstream against the surfaces
located on the right throttle quadrant power lever.
tends to force them closed. The force builds up the
Moving the SPD BRK switch to the forward position
hydraulic pressure in the speed brake system. When
closes the brakes. Moving it to center position holds
the pressure reaches a maximum of 3,650 psi, it
relieves through the blowback relief valve.
the brakes at any desired angle. Moving it aft opens the
16-45
