Maintenance Manual STEMME S10-VT
Date of Issue: Jan. 01, 1998
Page 3-28
Amendment Nr. 0
Date: --
A4011121_B23.doc
Doc. No. A40-11-121
3.4.13 Operation Mechanism of the Propeller Folding System
3.4.13.1 Propeller dome assy
The propeller dome forms the fuselage nose in front of the cockpit section and covers the folded propeller
during flight in glider configuration. To change from gliding to powered flight, the dome can be shifted forward
to allow the propeller unfold and rotate after starting the engine. In the forward position locking and unlocking
of the dome lever at the same time operates the engine master switch (see section 3.7.11).
The dome consists of a CFRP shell, a GFRP frame and an aluminium tube, which makes the suspension of
the dome at the front fuselage. The aluminium tube is guided through the hollow propeller drive shaft into an
aluminium tubular guided pipe, including teflon sliprings to allow axial sliding of the dome tube. The tubular
guided pipe is firmly stuck to the GFRP guide block in the forward cockpit.
Shifting the dome is by means of the propeller dome handle, installed in the lower section of the instrument
panel (see Fig. 3.2.a). The pull rod of the handle is connected to the dome sliding tube via a milled aluminium
bracked, which is screwed to the rear tube terminal and guided in a slot at the guide block. The bracket and
the handle guide assy prevent rotation of the dome. The handle assy includes a spring which acts towards
the locked (down) position of the handle.
3.4.13.2 Propeller positioning assy
The propeller positioning assy allows to rotate the propeller drive shaft after engine shut down and braking
the propeller to full-stop, to the position so that the folded propeller fits into the propeller dome contour. It is
operated by a pull handle on the lower instrument panel next to the propeller brake handle (see Fig. 3.2.a).
The propeller positioning is driven by a bowden cable. The bowden cable is routed from the handle to and
around an aluminium disc, which is pivoted on the guide block of the propeller dome sliding tube in the
forward cockpit. When pulling the handle, the disc rotates against a circumferencial spring force until
reaching a screw stop, which is adjustable and defines the final position of the propeller. The spring is winded
round the propeller dome guide block and rotates the disc towards its initial position when releasing the
handle.
On the disc a spring-loaded catch lever is installed, which is connected to the bowden cable rotating the disc.
If not operated, the spring acts on the catch lever, so it is clear of the propeller brake drum (see below),
mounted on the rear propeller drive shaft of the front gear. During pulling the handle, the spring force
unlocking the catch lever is over-balanced by the circumferencial spring force acting on the disc and the
catch will engage in one of two notches of the brake drum, thus rotating the drive shaft until reaching the
screw stop of the disc. The two notches of the brake drum are opposite, therefore the propeller rotates
maximum 180° during pulling the handle to the stop.
3.4.13.3 Propeller brake assy
The propeller brake is used to brake the propeller rotation to full-stop after engine shut down in flight, to allow
folding of the propeller by spring forces. It is operated by a pull handle on the lower instrument panel (see
Fig. 3.2.a).
The propeller brake is driven by a bowden cable, routed from the handle through the front fuselage frame to
the propeller brake assy, which is mounted on the rear housing of the front gear.
The cable is connected to a spring-loaded shift lever, which is mounted on the lower front gear housing and
pulls down one terminal of a brake band during operation of the brake. The brake band consists of a steel
sheet with a riveted brake lining. The brake band is built round a brake drum mounted on the propeller drive
shaft of the front gear. The second brake band terminal is fastened on the gear housing opposite to the other,
driven terminal. Some adjustment of the clearance between brake lining and drive shaft is possible by
loosening and shifting the bowden cable support.
