106
THIS IS AN UNCONTROLLED DOCUMENT.
THIS ELECTRONIC DOCUMENT MAY HAVE BEEN SUPERCEDED.
THE MOST CURRENT DOCUMENT INFORMATION IS AVAILABLE
FROM YOUR BELL HELICOPTER TEXTRON REPRESENTATIVE.
PRODUCT DATA
JANUARY 2003
POWER UP FUNCTION CHECK
a c c e l e r a t i n g t o g r o u n d i d l e . P i l o t f u e l
modulation is not required. Additionally,
t h e c o n t r o l c a n p r e v e n t m o s t
overtemperature starts by automatically
shutting fuel flow off should NG speed,
battery voltage, or MGT exceed “boundary
limits” during the start.
Continuous checks occur during normal
engine operation. These checks monitor
the functionality of the NP speed signals,
which supply the overspeed system. The
t w o N P s p e e d s i g n a l s t h a t s u p p l y t h e
o v e r s p e e d s y s t e m a r e c o n t i n u o u s l y
compared for differences, and should a
d i f f e r e n c e b e c o m e l a r g e r t h a n a
predetermined limit, a fault is declared.
The FADEC system incorporates logic and
circuitry to perform a high level of self-
diagnostics, some of which are described
herein. In general all sensors are checked
for continuity, rate, and range. Discrete
inputs are checked for continuity. Output
drivers are monitored for current demand
to sense failed actuators. Output drivers
are current limited. A FADEC power up
c h e c k e x e r c i s e s a l l o u t p u t d r i v e r s a n d
actuators to ensure system functionality
and readiness. All failure information is
r e c o r d e d b y t h e F A D E C E M S a n d i s
available to the maintenance crew via the
RS-423 maintenance data bus.
The power up check occurs when the ECU
i s f i r s t t u r n e d o n . T h i s c h e c k e n s u r e s
electrical continuity of the overspeed circuit
and the ability of the ECU to power the
overspeed solenoid. This test is performed
b y t u r n i n g o n e a c h o f t h e o v e r s p e e d
solenoid drivers and measuring the voltage
and current draw across the overspeed
solenoid valve. The measured voltage and
current are then compared to limits.
P o w e r t u r b i n e o v e r s p e e d l i m i t i n g i s
provided by an analog electronic control
that is integral to the ECU. The engine fuel
flow is reduced to zero flow upon activation
o f t h e o v e r s p e e d s o l e n o i d v a l v e ( a t
115%NP). The engine shuts down. The
overspeed limit control design incorporates
FOUR analog speed sensing circuits driven
by two NP speed signals. Two of the sensing
c i r c u i t s a r e i n d e p e n d e n t l y c a p a b l e o f
sourcing current to the overspeed solenoid
valve in the HMU. Two are independently
c a p a b l e o f p r o v i d i n g a g r o u n d t o t h e
overspeed solenoid valve. False trips are
unlikely since a false trip requires that two
i n d e p e n d e n t s e n s i n g c i r c u i t s f a i l .
A d d i t i o n a l l y , t h e a v a i l a b i l i t y o f t h e
overspeed protection is high since up to
two sensing circuits failures can occur
without affecting capability. The power
turbine overspeed limiter operates while
t h e E C U i s i n e i t h e r t h e a u t o m a t i c o r
m a n u a l m o d e . F u n c t i o n a l i t y o f t h e
overspeed system is evaluated by three
m e t h o d s , p o w e r u p c h e c k , c o n t i n u o u s
checks, and an automatic overspeed test.
The power supply for the power turbine
overspeed limiting circuits is independent
of the power supply for the remaining ECU
circuits and is sourced by both the aircraft
power bus and the engine mounted PMA.
NP OVERSPEED SYSTEM
SYSTEM BUILT IN TEST
CONTINUOUS FUNCTIONAL
CHECK
Содержание BELL 430
Страница 1: ...Product Data ...
