Maintenance Manual STEMME S10-VT
Date of Issue: Jan. 01, 1998
Page 3-31
Amendment Nr. 22
Date: Jan. 10, 2014
A4011121_B23.doc
Doc. No. A40-11-121
3.5 Landing Gear
3.5.1 Main Landing Gear (Fig. 3.5.1)
The landing gear (L/G) consists of a tail wheel and two retractable main landing gear legs, hinged at the
centre fuselage frame with the hinge axis in flight direction and locked in the extended position by means of
an over-centre locking strut ("elbow lever") for each leg. The wheel is mounted on a single trailing arm that is
supported against the leg's frame by a pre-loaded elastomeric spring for shock absorption purposes.
Retraction 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 lower end is coupled to the respective elbow strut by means of a locking mechanism
which can be released for an emergency let-down by pulling a T-handle in the cockpit (one for each of the
legs).
The actuators are controlled by limit switches, the ones for EXTENDED being integrated in the elbow struts
and detecting the over-centre position, those for RETRACTED are mounted at the fuselage frame and detect
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 processed by a TTL-logic and displayed by focused green and red
LED's on the right face of the instrument panel (ref. to the Flight Manual).
Both LG 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 so far as to allow retraction of the RH
landing gear leg. The RH landing gear leg effects complete closing of the door via the cable during the last
portion of its retracting. 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 waving, 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 main cylinder for both the left and
right wheel is located on the LH control stick, on RH stick optional. The pressure line from the main brake
cylinder to the brake callipers of the wheel brake in the center fuselage are designed as metal-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.
Only for hydromechanical Brake System:
The master cylinder for both the left and right wheel is located in the wheel well at the front wall. The
connection to the hand operating lever on the left stick is made by a bowden cable, adjustable at the master
cylinder. The hand lever can be locked in the operated position for use as a parking brake. A second lever on
the right stick, NOR-type coupled to the system, is available as an option. Plumbing from the master cylinder
to the wheel cylinders is realised by a short metal tube, T-type distributor and metal-shielded brake hoses.
The brake action is simultaneously 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.
Main Landing Gear Emergency Extension
By pulling two T-handles in the cockpit one after the other, the landing gear actuators are disconnected from
the locking elbow struts by means of a bowden cable and the landing gear legs extend by gravity to the "gear
down" position. The secure locking of each leg in the extended position is achieved by a spring that forces
the elbow lever into its over-centre position.
In case of an emergency let-down the two legs should be released in the recommended sequence (T-
handles marked 1 & 2, wrong order is not critical). The RH gear strut is equipped with a mechanism to avoid
jamming of the struts in case of an incorrect sequence.
3.5.2 Tail Wheel
The tail wheel is not sprung and fits in a trailing fork mounted in two bearings. The upper bearing is a
combined radial/axial sleeve bearing. The journal is constructed so that a certain friction damping is produced
at the axial sleeve surfaces when loaded in axial direction in order to avoid tail wheel flutter whilst taxiing. For
steering on the ground the tail wheel fork is coupled with the rudder by means of two pre-tensioned tensile
springs.
