TWO- OR THREE BLADED PROPELLER?
It is no mystery that three bladed propellers run smoother than two bladed ones. The cycles of harmonic vibrations emitted by the engine are clearly better dampened by three bladed propellers. That means less fatigue for material and pilot / passenger. But there are contrary facts to consider as well: The three bladed propeller weighs about 2 kg more – and of course, it is more expensive.
For the 80 hp ROTAX a two bladed propeller is definately a good choice. Even 100 hp can be handled with such a propeller, when always operated with correct max. RPM. But stronger engines need a three bladed prop. ROSPELLER is also available in the pusher configuration.
THE PROPELLER BLADES:
ROSPELLER only has blades of very experienced manufacturers as NEUFORM-Composites and HELIX-Carbon.
NEUFORM blades are made in glass-composite with a foam core, while HELIX blades are made in carbon with a foam core as well. Both blades have an integrated tapered steel root and are to be bolted to the bearing brackets.
left: standard
right: scimitar
NEUFORM blades are common to many different aircraft. HELIX blades come in many variations. Their scimitar and semi-scimitar blades are examples of advanced technology: Low noise – low vibration – low repitching moment.
a) standard scimitar
b) not available anymore
c) wide Scimitar
d) narrow scimitar
DIAMETER and RPM:
Considering an average Takeoff RPM of 2500 – 2600 revolutions, a diameter in the range of 168 – 172cm should be selected, depending also on the ground clearance of the aircraft. Larger diameters make propellers more effective, lower diameters and more prop blades do the same job.
MODULAR CONSTRUCTION:
The hub is precision made of a quality aluminum alloy and it consists of a fork type body, which carries the bearing brackets and the connected blades. The brackets may be used in a modular way on two- or three bladed hubs as well. All aluminum parts are anodized to prevent corrosion.
a: hub
b: front cap
c: bearing housing
d: blade receptor
MECHANICAL EMERGENCY STOP:
In the event of a malfunction, propeller blades tend to revert to fine pitch during flight. We have incorporated a fail-safe mechanical emergency stop in the form of an adjustable locknut, in order to maintain pitch to fly home safely.
adjustable stopnut
ACTIVATION:
The propeller pitch can be changed by a spring loaded toggle switch (standard), or a hand crank (available on request) on the instrument panel. Each input drives a push-pull rod through the hollow engine gearshaft, directly to the central shifting pivot to move the propeller blades. The maximum blade angle that can be controlled is up to 70° depending on the hub model.
scissors drive with pushpull rod
ELECTRICAL ACTUATION:
The DC Linear Actuator is hinged on the cast bracket of the scissors drive and faces forward. A green LED illuminates when “TAKE OFF/LANDING” fine pitch position is selected. A yellow LED indicates coarse pitch for “CRUISE/MAX”. With the electric prop option, any pitch between the two limit stop positions can be selected by a spring-loaded toggle switch. Adjustable microswitches at the scissors drive provide positive power removal from the electrical motor when LED’s light up.
scissors drive on the gear box of a Rotax 912
VACUUM PUMP and ROSPELLER:
On ROTAX engines the vacuum pump has to be installed on the rear side of the gearbox – exactly where the scissors drive for the ROSPELLER has to be mounted. For such applications a different solution has been provided. A new design of mechanism allows for both the pushpull rod control, and the installation of a vacuum pump to be installed together.
vacuum pump and Rospeller actuator
CONSTANT SPEED:
Constant Speed is an option, available at Flybox, for minimizing cockpit load. It comes as a small aircraft instrument of 57mm diameter, and at a very modest cost. Every necessary control device is integrated on the instrument. You simply use a toggle switch to set the engine/propeller revs to whatever you desire suited to the power inputs, and you can change these settings at will. With power applied, these revs are maintained regardless of speed, altitude and cruise or climb power settings.
