BEECHCRAFT King Air C90
Equipped With:
•
Swept Blade Turbofan Propellers
•
Dual Aft Body Strakes
•
Increased Gross Weight
•
PT6A-28 Engines
Revision IR: August 15, 2017
7-1
Document No. 16-206CGW-28
Section VII – Systems Description
SECTION VII — SYSTEMS DESCRIPTION
HARTZELL/RAISBECK SWEPT BLADE TURBOFAN PROPELLER SYSTEM
Each engine is equipped with an advanced technology, lightweight, Hartzell/Raisbeck Swept Blade
Turbofan propeller. Each propeller contains four blades, in full feathering, constant speed, counter-
weighted, reversing, variable-pitch, and mounted on the output shaft of the reduction gearbox. The
propeller pitch and speed are controlled by engine oil pressure, through single action engine-driven
propeller governors. Centrifugal counter-weights, assisted by a feathering spring, move the blades
toward the low RPM (high pitch) position and into the feathered position. Governor boosted engine oil
pressure moves the propeller to the high RPM (low pitch) hydraulic stop and reverse position. The
propellers have no low RPM (high pitch) stops; this allows the blades to feather after engine shut-down.
DUAL AFT BODY STRAKES
The Raisbeck Dual Aft Body Strakes are mounted on the underside of the aft fuselage, and replace the
single ventral fin. They are designed and engineered to attach and streamline the airflow over the aft
body reducing drag, improving aircraft stability and V
MC
.
PROPELLER DE-ICE SYSTEM
The Hartzell propeller electric de-ice system includes an electronically heated boot for each propeller
blade, brush assemblies, slip rings, an ammeter, a timer for automatic operation, and a manual control
circuit for backup.
The de-ice ammeter indicates the system amperage (normally 18 to 24 amperes). The timer directs
current to the single-element boot on each blade in the following sequence: right propeller all elements;
then left propeller all elements. Loss of one heating element circuit on one side does not mean that the
entire system must be turned off. The timer switches every 90 seconds resulting in a complete cycle in
approximately 3 minutes.
