Flight Controls Flashcards
three sections of the flight control system
mechanical control system
flight control servo system
automatic flight control system
control routing
controls are routed aft out and up then combined for each axis at the overhead torque shafts in the hyds bay. these are then passed with trims servo inputs to the pilot assist servos and mixing unit. fore/aft/lateral inputs are passed via the primary servos and bridge assembly to the swashplate assembly and tail inputs go aft to the tail quadrant
what is hyd power used for in the tail
hyd power is what moves the pitch change shaft, responding to mechanical input from the cables
what does the tail rotor quadrant do
transmits tail rotor cable movement to the servo
components of the flight control servo system
primary servos, tail rotor servos, pilot assist servos
components of the pilot assist servos
boost servos, SAS actuators, and hydraulic trim actuators (being pitch and roll trim)
can we operate the flight controls with hyd pressure in the pilot assist servos
yes but it sucks
can we operate flight controls with hyd pressure to the primary servos
no
what do you have to do to secure all hyd power to the pilot assist servos?
SAS/Boost and trim push buttons
what are the 3 boost servos
collective, yaw and pitch
what is the purpose of the mixing unit
to provide uncoupled airframe response characteristics
what portion of control mixing is contingent upon the trim being engaged
the electric collective/airspeed to yaw mixing
control mixing collective to yaw
because the nose would yaw right when collective is increased, tail rotor thrust is increased when collective is increased
control mixing collective to lateral
because the tail rotor would push us to drift right with an increase in collective, the rotor disc is tilted left
control mixing collective to longitudinal
because downwash pushes down on the stab and raises the nose, when collective is increased, the disc is tilted forward
control mixing yaw to longitudinal
because the tail has a mild vertical component, the rotor disc is tilted aft when left pedal is applied
control mixing, collective/airspeed to yaw
due to the aerodynamic characteristics of the tail pylon, at higher airspeeds, we would yaw left, some trim is added to manage this yaw depending on overall torque compensation required as we shift airspeeds
what kind of AFCS system do we have
electrohyrdomechanical
three major subsystems of the AFCS
SAS, Stabilator, and AFCC (advanced flight control computer)
are the three major subsystems of AFCS dependent on each other
no
how many features does the AFCS have
19
What are the AFCS features
5 holds (pitch and roll attitude hold, airspeed hold, heading hold, baralt, radalt)
6 hovers (approach to hover, hover augmentation/gust alleviation, hover coupler, depart from hover, cable angle hover, crew hover)
Stabx3 (pitch/roll/yaw stability augmentation, stabilator control, maneuvering stability)
trim (cyclic, collective, pedals)
turn coordination
blade fold
check preflight
diagnostics
requirements to turn auto pilot on
at least one SAS and trim
what should you do if you have a SAS 1 channel fail and how is this different from SAS 2
disengage SAS 1, SAS 2 will disable the affected system on its own
AFCC inner loop control is
SAS - rate damping to improve helicopter stability
fast, limited in authority, and does not move the controls
AFCC outer loop control is
autopilot - long term inputs by trimming controls
can move controls through full range of travel at up to 10% of travel per second
Where does the AFCC route inner loop and outer loop corrections through
inner go through sas actuators
outer go through trim actuators
purpose of the AFCS voltage sensor relay
basically it is a conditional switch, if #1 ac pri bus is providing power in limits it pulls power from there, if not, it switches to the #2
describe the stabilator system
automatic fly by wire with a back up manual slew control
what does the stab system share with other parts of AFCS
airspeed sensors, pitch sensors, lateral accelerometers, collective position sensor
primary purpose of the stab system
angle of attack stability
below what airspeed is the stab test button functional
50 kias
how is the stab positioned
2 electric jackscrews, each providing one half of the input
stab travel range
42 degrees trailing edge down to 10 degrees up
four inputs to the stab
collective position
lateral acceleration
airspeed
pitch rate
in the event of a failure of the stab actuators what is the range of travel restricted to
35 if failed full down
30 if failed full up
Difference between SAS 1 and 2
SAS 1 Analog, SAS 2 digital part of AFCC and incorporates hover augmentation/gust alleviation and altitude hold and coupler functions, turn coorodination
SAS control authority
+- 10% each channel providing 5
which SAS channel can affect collective
SAS2 via collective inner loop actuator with +-10% authority
one SAS channel inop control authority
limited to +-5% but operates at 2x the gain
what causes SAS caution
loss of electrical power to SAS 1 or 2 or loss of hyd power to actuators
which trim servos are electric and which are hydraulic
yaw and collective are electric
pitch and roll are hydraulic
trim has how much control authority at what rate
100% at a 10%/sec rate
yaw pedal trim with respect to airspeed
below 50 kias only need pedal microswitches
above 50 both pedals and cyclic
autopilot functions
pitch and roll attitude, airspeed and heading, coordinated turn
attitude vs airspeed hold
attitude less than 50
airspeed greater than 50
less than 50 kias 4 way trim switch rate
pitch at 5 deg per second
angle of bank limit for airspeed hold
30 deg
above 50 kias airspeed hold 4 way trim
6 kias per second
4 way trim switch lateral rate
6 deg per second
heading trim switch below 50 kias
3 deg per second
heading trim above 50 kias
one degree per click or 1 degree per second of coordinated turn
what conditions must be maintained for heading hold to reengage
for 2 seconds
roll within 2 deg of wings level
yaw rate less than 2 deg/sec
torque limits for alt hold
will stop raising collective at 106%Q if above 80 kias
120% if less than 80
radalt hold range
0-5000AGL
coupled hover altitude adjustment rates
1000 fpm climb
200 fpm descent
radalt/baralt back up
bar alt will kick on if radalt suddenly disengages
what airspeed is required for turn coordination
50 kias
AFCS auto switches from heading hold to turn coordination under what conditions
roll attitude greater than 1 deg and:
lateral cyclic of at least 3% or
cyclic trim rel button pressed or
roll attitude > 2.5 deg with 4 way trim or
coll heading trim actuated for more than one second
what angle of bank must be exceeded to feel the maneuvering stability function
30 deg
maneuvering stability numbers
1% fwd cyclic for every 1.5 degrees past 30 AOB up to 75 AOB
when does the aircraft assume a wing level attitude in auto approach
80 kias
at what speed does the aircraft on auto approach reset any trim inputs
40 KGS
Automatic approach profile
on profile while greater than 40 KT 2.5kt/sec decel and 215 ft/min descent
less than 40 kt: 1.5 kt/sec decel 130 ft/min descent
auto approach above profile
airspeed hold
360 ft/min descent
auto approach below profile
radalt hold
2.5 kt/sec decel
4 way trim switch authority in coupled hover
+- 10 KGS
when will the aircraft switch from approach to hover
longitudinal ground speed within 1 KGS of selected or 5KGS when manually engaged
when will radalt engage from approach to hover
when within 2’
what torque is the AFCC going to limit itself to in a coupled hover
116%
concern in coupled hover with >50 kias
if you press the cyclic trim button it will switch to turn coordination
when can auto departure be engaged
need auto pilot
airspeed less than 50 kias
radalt hold operable
on a departure, when will the aircraft assume a wings level attitude
50 kias if angle of bank is 5 deg or less
what torques will AFCS not raise the collective through on departure
106% above 80 kias
120 below 80 kias
max AOB to engage approach
20
what will the a/c do if you select depart on an approach
will auto assume a 2 degree nose down attitude
crew hover authority
+- 5 KGS after what is set up front
departure profile
240 ft/min climb
while below 85 KIAS 3 kt/sec accel
then fade so that once above it is at 1 kt/s above 100 kias
how long after we start moving the dome in the water is the cable angle signal decoupled
9 sec
when do we get cable angle at limit
7.5 degrees of deflection
normal left wing down in hover
2-3 deg
what does subm override do
overrides the 27 +- 12 ft requirement to engage cable angle hover
requirements for cable angle engagement
groundspeed less than 5 knots
radalt within 10’ of selected alt
dome wet indication
afcs degraded not on
auto plt on
dprt or crew hover not engaged
main input to cable angle hover
cable angle sensors in alfs reeling machine
less important inputs to cable angle hover
pitch/roll/horizontal ground speed signals from EGIs
horizontal and vertical acceleration from accelerometers
pitch and roll signal from rate gyros
pitch/roll/collective from SAS and trim servos
rad alt reading
when does cable angle turn off
when the dome passes through 27 +- 12 feet on the way up if not subm override
pushing the button
radalt selection and actual alt differ by 10’
both long and lat signals fail
when cpld hover manually disengaged
how long are cable angle controls input suppressed after flight control trim inputs are made
20 seconds
what to expect if an EGI fails in a hover, approach, departure
radalt hold will hold but may experience up to 40 feet of change
may develop a slow pitch roll or yaw rate
