Saab 340B, Operation Manual, Page: 652 / 670

LANDING GEAR
Description
Aircraft Operations Manual
13.1
PAGE 2
Apr 01/15
connected from the gear, leaving the doors in fully
open position. The disconnection is made by an
explosive separation bolt that is electrically acti-
vated by the emergency extension handle when
pulled. The electrical circuits are deactivated on
ground.
If the landing gear was emergency extended due
to loss of hydraulic pressure/fluid or a fault in the
landing gear control valve, the nose wheel steer-
ing will be inoperative.
NOTE
When retracting the gear, the indications are as fol-
lows:
− When gear UP is selected, the amber disagree-
ment light in the gear handle knob will come on
to indicate disagreement between the handle and
gear positions. After a few seconds the green
downlock lights go out.
− When the gear is up and locked, the light in the
gear handle knob goes off.
When extending the gear, the indications are as
follows:
− If all gears are up and the gear handle is UP,
there is no light indication.
− When gear DN is selected the disagreement light
in the gear handle knob comes on to indicate ini-
tial disagreement between handle position and
actual position of gear.
− When a gear is down and locked, the respective
green downlock light comes on. When all three
gears are down and locked the amber gear han-
dle disagreement light goes out.
During emergency extension, the green down
locked gear lights come on irrespective of gear han-
dle position. The amber disagreement light goes out
when the gear handle is selected down.
The integrity of the indicator lights is tested by
pressing the test button on the gear handle unit.
2.2 Brakes (Fig. 1)
The main landing gear wheels are fitted with self −
adjusting hydraulic disc brakes.
There are two brake circuits − one for the outboard
and one for the inboard brakes. Each circuit has its
own accumulator. Hydraulic pressure is normally
supplied by the electrical hydraulic pump but the
hand pump may be used as an alternative.
The different brake functions are:
− Normal braking (anti − skid).
− Emergency braking (anti − skid).
− Parking brake.
Normal braking
Braking is controlled by the rudder pedals in the
conventional manner. Each pedal is connected to
one outboard and one inboard brake power valve
and, consequently, each brake has its own power
valve. The four power valves are installed on a
common assembly in the nose wheel well ceiling.
An anti − skid system modulates brake pressure for
maximum braking efficiency. The system consists of
an anti
− skid control box, one wheel speed transduc-
er on each main wheel, two anti − skid valves and an
anti − skid ON/OFF switch on the hydraulic panel in
the center pedestal.
The anti − skid system also incorporates ”Touchdown
Protection”. This function prevents braking whilst in
flight in order to avoid landing with braked wheels
and consequent damage to the tyres.
In order to obtain braking with anti − skid protection
the following is required:
− Anti − skid switch ON
and (for each circuit)
− appropriate power lever (see Fig. 1) below flight
idle, plus 3 seconds delay
or
− appropriate left or right weight on wheel switch
(see Fig. 1) activated to ”ground” position, plus 3
seconds delay
or
− average wheelspeed over 50 kts.
The activation logics for the inboard and out-
board circuits are independent.
NOTE
Throughout the landing roll, the wheel speed trans-
ducers send signals via the control box to the anti
−
skid valves which modulate the brake pressure.
Should a skid begin, e.g. on an inboard wheel,