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Propellers
These propellers are variable pitch, and contain and electric heater to melt ice
(the black stripson the edge).
Piston engines are typically connected to a fixed-pitch or a constant-speed propeller.
 | Fixed-pitch propellers are bolted directly to the crankshaft of the engine and therefore
always turn at the same speed as the engine. A fixed-pitch prop is somewhat like a
transmission with only one gear. This configuration makes up for its lack of efficiency by
being very simple to operate. The only gauge that you need to monitor is the tachometer. |
| A constant-speed propeller has a governor that adjusts the angle of the blades to
maintain the RPM you select. This type of propeller makes much more efficient use of the
engine's power. At low speed when maximum power is required (as during takeoff), you
select maximum RPM or "full increase" with the propeller control, and the prop
blades meet the air at a small angle. During cruise, you adjust the RPM to a lower
setting, and the prop blades take a bigger bite of the air while turning a lower speed. |
Managing the Power
With a fixed-pitch propeller, managing power is simple. Push the throttle in, and RPM
(and power) increases. Pull the throttle out, and RPM decreases. Be aware, however, that
as airspeed increases, RPM tends to creep up, too. Monitor the tachometer carefully during
descents at high speed to make sure that the RPM stays within limits.
A constant-speed propeller makes power management a bit more complicated. You must
monitor the manifold pressure gauge, controlled by the throttle, and the tachometer, which
shows the propeller RPM. You adjust RPM with the prop control.
When setting power with a constant-speed propeller, remember these basic rules to avoid
overstressing the engine:
- To increase power, first increase RPM by advancing the prop control, then increase
manifold pressure with the throttle.
- To decrease power, first reduce manifold pressure with the throttle, then decrease RPM
with the prop control.
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