UH-60 SYSTEMS STUDY
MECHANICAL MIXING
Coll. to Pitch – Compensates for rotor
downwash on the stabilator.
Coll. to Roll – Translating Tendency.
Coll. to Yaw –Torque Effect.
Yaw to Pitch – Lift component of Tail
Rotor.
AFCS
Enhances stability and
handling qualities of the helicopter.
Accomplished with four subsystems:
1.
SAS
2.
Trim
3.
FPS
4.
Stabilator
TRIM
Provides a gradient force, maintains
position of cyclic and tail rotor
controls, and provides muscle for
FPS. Consists of 2
electromechanical actuators (roll and
yaw), & 1 electro-hydro-mechanical
actuator. (pitch)
Boost required for operation.
Slip clutches req. 80 lbs max in yaw
and 13 lbs max in roll during actuator
jam. Hard-over causes
caution/advisory lights and could
move cyclic ½ inch or pedals ¼ inch.
ELECTRONIC COUPLING
Collective to Airspeed to Yaw –
Compensates for torque effect in
addition to Collective to Yaw mixing
based on collective position and
airspeed. Function of Trim Card.
Provides 100% input below 40 kts.
Tapering to 0% at 100kts.
FPS
Basic autopilot – Enhances static
stability through long term rate
dampening in pitch, roll, and yaw. It
is the “Brain”. When coupled with
Trim, FPS has 100% control authority.
Below 60 Kts
Above 60 Kts
AH
Pitch
AH/AS H
AH
Roll
AH
HH
Yaw
HH/TC
These systems must be on and
operational for FPS to function at 100%:
1. SAS 1 and/or SAS 2
2. Boost
3. Trim
4. Stabilator (helps, but not required)
SAS
Enhances dynamic stability through
short term rate dampening in pitch, roll,
and yaw. 5% (elec. limit) control auth.
Each, 10% total (mech. limit).
SAS 1
SAS 2
Brain is SAS amp. in avionics
compartment. 5% cont. auth.
Input:
Pitch - #1 stabilator amp.
Roll – pilot’s vert.gyro
Yaw – in SAS 1 amp.
Airspeed – A/S transducer
Malfunction indicated by erratic
movement of helicopter (no lights).
Brain is SAS/FPS computer under
center console. 5% cont. auth.
Input:
Pitch - #2 stabilator amp.
Roll – roll rate gyro (Nose)
Yaw – yaw rate gyro (Nose)
Airspeed – Air Data transducer
Malfunction indicated by SAS 2 failure
advisory light on AFCS switch panel.
UH-60 SYSTEMS STUDY
STABILATOR
Variable angle of incidence airfoil that
enhances the handling qualities of
the helicopter and improves static
and dynamic stability about the pitch
axis.
SCALP
Functions:
Streamlines w/ rotor downwash at
low speeds (below 30 kts) to min.
nose up attitude. (A/S & Air Data
Transducers)
Collective Coupling to min. pitch
attitude excursions due to collective
inputs. (Collective Pos. Transducers)
Angle of Incidence decreases above
30 kts. to improve static stability. (A/S
& Air Data Transducers)
Lateral Sideslip to pitch coupling to
reduce susceptibility to gusts. Stab
up for nose right, stab down for nose
left. (Lat. accelerometers)
Pitch Rate Feedback to improve
dynamic stability. Dampens pitch
excursions due to turbulence or “G”
forces. (Pitch Rate Gyros)
DRAG BEAM SWITCH (WOW)
ITABUSHEA³
IFF Mode 4-Auto Zeroize enabled in
flight.
Thermal protection for B/U pump
enabled on the ground.
Audio for low RPMR disabled on the
ground.
B/U Pump Auto OPN regardless of
switch position enabled in flight.
Underfreq. protection disabled in flt.
SAS/FPS computer degraded on gnd.
Hydraulic leak test disabled in fight.
ESSS jettison disabled on ground.
Aux. Fuel INCR/DECR disabled flt
AFMS 5 min. delay enabled on gnd
AFMS PBIT/IBIT enabled on gnd.
ECU
Controls electrical functions of engines
and transmits operation information to
the cockpit.
NOT THIS
Functions:
Np reference, set by pilot
(INCR/DECR from 96-100%)
Over-speed Protection. Switches close
when Np reaches 106+1% and open
when Np is below 106+1%.
TQ Match/Load sharing. Torque will
increase to share, but not decrease.
(3% above reference)
TGT Limiting (834-852°C). Except
during start, comp. stalls, or during
ECU Lockout.
History recorder signals sent.
Isochronous Np Governing. ECU
will maintain Np reference set
by the pilot (Primary Function) Trims
the HMU output through the TQ motor
determined by:
Signals to cockpit for Np, TGT, and
Torque.
ALTERNATOR
ANIE
Three windings for three functions:
Ng signal to cockpit. (green cable)
Ignition power to the exciters during
start. (yellow cable)
ECU power (yellow cable)
FUEL FLOW
PFHLP
Pump (Engine Driven Suction)
Fuel Filter
HMU
Liquid to Liquid Cooler
POU
UH-60 SYSTEMS STUDY
HMU
Basic fuel control; Includes high pressure fuel pumping & variable geometry
positioning through mechanical linkage.
PM CAN VETO
Functions:
Pumps fuel at high pressure (400 – 832 psi.)
Meters fuel to POU in response to PAS, LDS, Torque motor from ECU, &
engine variables (T² and Ng).
Collective Pitch Compensation through the LDS. When the collective is moved,
Ng is reset for immediate Np response.
Accel/Decel flow limiting prevents compressor stalls, engine damage, and
flame out. (Ng)
Ng limiting – Limits max torque available under low temp (Compressibility)
conditions. (T², P³)
Variable Geometry Positioning of the inlet guide vanes for optimum
performance. (T², Ng)
ECU Lockout- PAS Override & Control with ECU input from Linear Variable
Differential Transducer bypassed. Allows pilot to mechanically bypass torque
motor inputs.
Torque Motor to Trim Ng Output. To fine tune engine output (Np Governing).
Can be overridden in ECU lockout.
Opens Vapor Vent for manual HMU priming, to remove air from HMU.
POU
MOPS
Main fuel sequencing for engine starting and operation (12 Fuel Injectors).
Overspeed Protection (Np) solenoid activation from ECU signal to limit fuel flow.
Purges start fuel manifold and main fuel manifold and nozzles on shutdown to
prevent coking (carbon build-up).
Sequences start fuel for engine start (2 start fuel nozzles).