AFCS (in progress) Flashcards
The central component of the AFCS is ______
the digital advanced flight control computer (AFCC)
The _____ is designed to select the source of the single phase, 115 VAC, phase B power to be applied to the AFCC.
Voltage Sensor Relay (VSR)
Normally, the AFCC is powered by the _____,with the VSR energized and the _____ bus relay energized.
#1 AC Primary Bus AC Essential
If voltage is not within tolerance, the VSR deenergizes and the ____ and _____ are powered from the _____.
AC Essential bus and AFCC
No. 2 AC Primary Bus
The stabilator is an ______________ control system with a backup manual slew control
automatic, fly-by-wire
In low speed flight, the purpose of the stabilator’s variable angle of incidence functionality is to ____________ caused by rotor downwash impinging on the stabilator. To accomplish this, the stab was designed to program so it aligns with rotor downwash in low-speed flight regimes.
eliminate undesirable nose-up attitudes
The Stabilator TEST pushbutton is operational below ____ KIAS and is used to check the ______
50, automaticmode fault detector
Two _________, acting in series, position the stabilator.
electric jackscrew actuators
Below ____ KIAS, the stabilator will be 42 degrees trailing edge down.
30
The stabilator electrical screw actuators receive power from the ____ and _____.
dc essential bus and NO. 1 DC primary bus
Four inputs are required to position the stab:
Collective position, lateral acceleration, airspeed, pitch rate
Collective to Yaw (control mixing)
Cause: Main rotor torque
Compensation requirement: Nose yaws right when collective is increased
Compensation: Tail rotor thrust is increased
Collective to Lateral (control mixing)
Cause: Lateral lead (tail rotor propeller effect)
Compensation requirement: Helicopter drifts right when collective is increased
Compensation: Rotor disc is tilted left
Collective to longitudinal (control mixing)
Cause: Rotor downwash on stabilator
Compensation requirement: Nose pitches up and helicopter drifts aft when collective is increased
Compensation: Rotor disc is tilted forward
Yaw to longitudinal (control mixing)
Cause: Tail rotor lift vector
Compensation requirement: Nose pitches down and helicopter drifts forward when left pedal is applied
Compensation: Rotor disc is tilted aft
Collective/airspeed to yaw (control mixing)
Cause: Camber of tail rotor pylon varies side load with airspeed
Compensation requirement: Nose yaws left as airspeed increases
Compensation: A portion of the main rotor torque compensation is provided by a trim input that is proportional to collective position and airspeed. The trim input is then progressively washed out as pylon side loads increase with airspeed.
The AFCS is composed of three major subsystems:
the Stability Augmentation System (SAS), the stabilator system, and the Advanced Flight Control Computer (AFCC)
The AFCC processes incoming information from various sensors and stores the information in its memory. The data is used by the computer’s central processing unit to compute required correction signals. Inner-loop correction signals are routed to the _______ and outer-loop signals are routed to the________.
SAS actuators, trim actuators
The AFCC is powered by the ______. If the voltage is not within tolerance, _________________.
No. 1 AC Primary bus, the VSR deenergizes and the AC Essential bus and AFCC are powered from the No. 2 AC Primary bus.
SAS provides improved stability by ____________.
sensing acceleration rate in the pitch, roll, and yaw axes and applying a control input to dampen out the sensed rate.
SAS 1 is an ________; SAS 2 is a ______ that is part of the _____.
analog system, digital system, AFCC
With both SAS channels engaged, the pitch, roll, and yaw actuators have _______________.
±10 percent control authority with each channel providing ±5 percent
Only SAS 2 commands the collective inner-loop actuator (CILA). The collective SAS operates with ______________ modes engaged and is limited to ±10 percent control authority.
RAD ALT, BAR ALT, APPR/HVR, and DEPART
For each control axis (except vertical), command signals from both SAS channels are applied simultaneously to___________. The two signals are summed to provide a single input into the flight control system through a ___________.
separate coils of an electrohydraulic servo valve; single-series SAS actuator
If ____ has failed, the AFCC will automatically disengage the affected axis. If ____ has failed, the pilot must manually disengage SAS 1 using the AFCS CONTROL panel. The remaining operable SAS channel is limited to ±5 percent authority, but operates at twice its normal gain to partially compensate for the failed SAS channel.
SAS 2, SAS 1
The trim system uses _____ servos for the yaw and collective axes and _____for the pitch and roll axes.
two high-torque electric; two hydraulic servos