DOCUMENT NUMBER:
L500-912.820 ISSUE JUL 20, 2016
AMENDMENT: 00
DATE: --
CHAPTER-
PAGE 3-33
MAINTENANCE MANUAL STEMME S12
3.5 LANDING GEAR
3.5.1
MAIN LANDING GEAR
The landing gear (L/G) consists of a tail wheel and two retractable main landing gear legs, hinged
at the center fuselage frame with the hinge axis in flight direction and locked in the extended
position by means of an over-center locking strut (“elbow lever”) for each leg. The wheel is
mounted on a trailing arm that is supported against the leg’s frame by a pre-loaded elastomeric
spring for shock absorption purposes.
Retracting of the L/G legs and doors is managed by an electrically driven linear actuator for each
leg that is built up around a high precision ball screw. Each of the linear actuators is hinged with
the top end at the fuselage frame; the bottom end is coupled to the respective elbow strut by
means of a locking mechanism which can be released for emergency landing gear extension by
pulling a T-handle in the cockpit (one for each of the legs) and via a bowden cable. In case of
an emergency extension the two legs should be released in succession (right-side-first order is
suggested, but wrong order is not critical), they then extend out by gravitational force. Secure
locking in the extended position is achieved by a spring that forces the over-center strut into its
end position.
The actuators are controlled and sequenced by stop switches, the switches for EXTENDED be-
ing integrated in the elbow struts and detecting the over-center position, those for RETRACTED
mounted at the fuselage frame and detecting the top position of each L/G leg. All these switches
are in duplicate, the second one giving the signal for the indication and warning system, which is
displayed by focused green and red LED’s on the right face of the instrument panel (refer to the
S12 Aircraft Flight Manual).
Both L/G doors are actuated by the landing gear legs. The RH landing gear door is coupled directly
to the RH landing gear leg via a spring device. The LH door is controlled by a cable mechanism.
During retraction, the LH landing gear leg starts closing the LH door by means of a cable, but
it remains open enough to allow retraction of the RH landing gear leg. The RH landing gear leg
effects complete closing of the LH door via the cable during the last portion RH main gear re-
traction. Opening of the LH door is by a spring loaded roller strut, which rolls on the LH door. It
pushes the door to the outside against the cable to keep the door from moving due to air loads,
and is blocked with the landing gear retracted, thus locking the door. In closed position the doors
are additionally locked at the rear by means of magnets.
The disk brakes on the main L/G wheels are operated hydraulically. The master cylinders for both
the left and right wheel are located on the control sticks. The pressure line from the master brake
cylinders to the brake calipers of the wheel brakes in the center fuselage are designed as met-
al-shielded brake hoses. The brake fluid reservoir is located in the landing-gear bay, cabin rear
wall.
The parking brake valve to set and to release the parking brake is located on the floor panel console
in front of the LH control stick. The parking brake valve is operated by a lever respectively rotary
handle. Braking action is simultaneous on both main wheels. Maximum brake pressure for the
system layout is 115 bar / 1668 psi, maximum allowed system pressure is 200 bar / 2900 psi.
Summary of Contents for S12
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Page 255: ...A FLIGHT CONTROLS PITCH CONTROL AND TRIM ...
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