Copyright of RotorSport UK Ltd
Document number RSUK0288
Page 36 of 55
Control: There is no constant-speed controller fitted to the RSUK IVO-prop installations and
pitch adjustment is made manually by means of a rocker-switch mounted on the left of the
instrument panel. There are no micro-switches to limit blade movement so the control system
utilises a bespoke circuit-board (the end position controller) which detects the rapid rise in
current and disconnects motor power when each pitch limit is reached. Two amber LED
indicators mounted adjacent to the rocker switch provide status information:
Both LEDS off
Propeller is not at an end position and no pitch change command active
Upper LED blinking
Propeller changing pitch to FINE
Lower LED blinking
Propeller changing pitch to COARSE
Upper LED steady ON
End position FINE reached and electronic pitch inhibit FINE activated*
Lower LED steady ON
End position COARSE reached and electronic pitch change inhibit COARSE
activated*
Both LEDS flashing fast
Actuating motor does not work despite rocker switch activation.
Possible defects, e.g. brushes worn, cable break.**
*Electronic pitch change inhibit is deactivated after selecting pitch change in opposite direction for at least 1 second
**Indication can only be reset by switching the master switch temporarily to OFF and then back to ON. In order to avoid
pilot distraction, indication of a possible defect is retriggered after another activation of the rocker switch
Both the end-position controller and the propeller are fed from the same 16A circuit-breaker
mounted in the right-hand instrument panel.
The propeller will take up to 10seconds to cycle between fully fine and fully coarse.
Principle of operation:
The propeller assembly is an in-flight variable pitch design. Pitch of the three blades is
adjusted simultaneously via a cam system inside the propeller. The cams are driven by a 12v
motor. The motor is supplied with current via two slip rings in the propeller assembly and a
brush-box mounted on a fabricated bracket at the rear of the engine.
The blade pitch angle is limited by thrust washers (selected for each engine type) and the end-
position controller removes electrical power from the motor when the thrust washers reach
their end-stop.
The propeller pitch angle relationship to engine rpm is managed manually by the pilot with the
aid of a manifold pressure gauge. The characteristics of each engine type (912ULS normally
aspirated or 914UL turbocharged) are different, so the Pilots Handbook RSUK0287 is
furnished with a look-up table for use by the pilot.
ROTAX 912 ULS
Power setting
Engine RPM
MAP
Fuel flow
[ltr/h]
Max. TOP
5800
27.5
27
Max. MCP
5500
27
26
75% MCP
5000
26
20
65% MCP
4800
26
18
55% MCP
4300
24
14
Page issue 4, dated 08.06.15