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ProAct P-Series FL Position Controller
Manual 26659
10
Woodward
Figure 2-1. Fuel Stops
Linkage
Proper design and installation of the actuator linkage is necessary for the ProAct
P-Series FL actuator to provide the best possible speed control. Certain
applications with low inertia may be unstable with high impulse loads and may
require additional system inertia. See troubleshooting guidelines or contact
Woodward for more information. Ensure the actuator has ample work capacity to
control the fuel supply under maximum load conditions.
Manually stroke the fuel-control linkage from stop to stop as if the actuator were
moving it. The linkage must move freely, without friction and backlash. Lubricate
or replace worn linkage or fuel control parts as required.
The actuator contains no internal return spring; therefore an external
positive shutdown is necessary in the event of a loss of power to the
actuator.
The actuator’s maximum slew rate can place stress on the fuel
system stops and on the linkage between the actuator and the fuel
system. The maximum actuator speed is 1000 degrees per second in
both increase and decrease fuel directions.
The Mass Moment of Inertia (MMOI) for the ProAct P-Series FL actuators:
Model II is 5.5E-4 kg-m² (4.9E-3 lb-in-s²)
Model III is 6.4E-4 kg-m² (5.6E-3 lb-in-s²)
Model IV is 8.2E-4 kg-m² (7.2E-3 lb-in-s²)
The fuel system stops must be adequate to absorb the actuator MMOI in addition
to the linkage inertia without damage. ProAct P-Series FL actuator internal stops
are designed to absorb 0.011 J (0.097 in-lb) of kinetic energy with 1.5 degrees of
over travel. If the actuator stops are used, the load inertia must not exceed
4.25E-4 kg-m² (3.76E-3 in-lb-s²), and the linkage must be designed to allow the
1.5 degrees of over travel on each end. Use of good rod-end connectors with as
little free play as possible is essential. Select rod ends that will remain tight and
wear well during the nearly constant movement associated with precise speed
control. Low-friction, long-wearing rod ends are available from Woodward. The
link connecting the actuator lever to the fuel-control lever must be short and stiff
enough to prevent flexing while the engine is running.