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vent their separation from the spinner in the
steady-state and transient propeller perform-
unlocked condition.
ances specified in the model specification.
3.25.5 Installation. The spinner shall be
3.28.2 Provisions.  The propeller control
such that when installed it shall in no way im-
system shall include all necessary provisions re-
pair the strength of the propeller and shall not
quired for proper and complete automatic,
interfere with the functioning of the propeller
manual, or emergency control of the propeller.
or propeller controls. Mounting provisions
These provisions shall be specified in the model
for accurately centering the spinner on the hub
specification.  These provisions depend upon
shall be capable of withstanding frequent in-
the requirements for a given application and
stallation or removal of the spinner without
will include one or more of the following:
(a) All elements of self-contained type
3.26 Blade cuff. The type of blade cuff
propeller control systems required for
shall be specified in the model specification.
speed governing in normal or reverse
The attaching means shall be such that injury
pitch, for control in the beta regime,
will not result to the blade from chafing and
and for emergency features shall be
maximum corrosion protection will be afforded.
contained within the propeller and
3.27 Pitch-changing systems.
shall function independently of the
3.27.1 Pitch-changing. The pitch-changing
synchronizer. The only elements that
system shall function satisfactorily throughout
may be mounted remotely are the
all regimes of flight and ground operation and
synchronizers of the governor trim-
shall be described in the model specification.
ming type, the elements that must be Hydraulic operation. When the
incorporated in the pilot's or flight
pitch-changing system is hydraulically actu-
engineer's power control unit, sources
ated, in whole or in part and the source of
of emergency signals such as negative
hydraulic power or fluid is self-contained, the
torque signals (NTS) and items of
system shall be independent of the engine lubri-
secondary importance (i.e., tachometer
cating system and the aircraft hydraulic sys-
generator). In other type systems,
tem. If the engine lubricating oil is used, the
emergency features not self-contained
propeller manufacturer shall utilize the oil pas-
within the propeller shall be specified
sages provided by the applicable engine or ex-
in the model specification.
ternal lines if passages are not provided.
(b) The primary features of self-contained
3 . 2 7 . 1 . 2 Electric operation. When the
type propeller control systems shall
pitch-changing system is electrically operated,
function independently of the engine
in whole or in part, the voltage and frequency
oil system or the aircraft electrical sys-
of the current for which the pitch-changing
tem insofar as flight safety features are
system is designed shall be compatible with the
concerned. Other functions such as
aircraft electrical system. In cases where the
back-up protection or those that do not
propeller manufacturer provides the source of
involve flight safety of the aircraft
power that is independent of the aircraft elec-
such as speed synchronization, phase
trical system, the electrical source shall be con-
synchronizing, or feathering near zero
tained within the propeller.
rpm may utilize electrical power from Mechanical operation. When the
the aircraft electrical system. In other
pitch-changing system is entirely mechanically
type control systems, functions depend-
operated, the pitch change operating force shall
ent upon the engine oil system or the
be available at all propeller speeds. Pro-
aircraft electrical system, shall be
visions for unfeathering of the propeller shall
listed in the model specification.
be provided.
(c) The propeller control system shall in-
3.28 Control system.
corporate the following emergency
3.28.1 Performance. The control system
shall control propeller operation to attain the
(1) A mechanical low pitch stop.

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