Flight director Flashcards
(51 cards)
Components of AFCS
SAS, Trim, FPS, Stab, FD
4 MMU function
Collective to pitch - Compensate for downwash on stab
Collective to roll - Compensate for translating tendency
Collective to yaw - compensate for torque effect
Yaw to pitch - Compensate for vertical thrust component of tail rotor
What does AFCS do
Enhances stability and handling of helicopter
Provides autopilot functions
What does SAS do
provides short term rate dampening in pitch, roll, yaw axes. Enhances turn coordination
What does trim do
Provides control positioning and force gradient functions as well as autopilot functions when used with FPS
What 9 functions does AFCS provide
Pitch, roll, yaw stability augmentation
Stab control
Cyclic, collective, pedal trim
Pitch and roll attitude hold
Heading hold
Pitch/roll hover augmentation and gust alleviation
Turn coordination
Fault detection/annunciations
Coupled FD integration
What does FLT DIR FAIL actually mean
One or more FD functions have disengaged.
What do FCCs do
They take signals from controls, motion sensors, control panels, and avionics to generate commands for the trim actuators, sas actuators, and STAB
Which system is inner loop, which is outer loop
SAS is inner loop
Trim is outer loop
What is trims authority and rate
100% authority over range of motion of controls, 10% per second
What is the authority SAS
10% max authority
(5% authority when SAS 1 or 2 is off - SAS DEGRADED)
Where do signals from FCC 1 and FCC 2 go
FCC 1 - SAS 1 actuators, No 1 STAB actuator
FCC 2 - SAS 2 actuators, no 2 STAB actuator, Trim
Define static stability
Tendency to return to pilots desired attitude or heading
Define dynamic stability
Tendency to resist movement (porpoising, rocking, fishtailing)
Describe the flow of input to output through AFCS
Input - Attitude/rate signals from EGIs, airspeed from ADC, position and accelerometer signals, stabilator position transmitter
Processor - FCCs
Output - Trim, SAS, stabilator actuators
How to the FCCs compare information
Cross channel data link
Describe the stab
Variable angle of incidence airfoil that enhances handling in the pitch axis
What range can the stab position indicator read between
-10 and 45
What can lead to limited auto mode (STAB DEGRADED)
How does it affect stab function
-1/2 signals lost from collective stick position, lateral accelerometers, or pitch rate data, or 1/2 actuators fail.
- half movement speed
-30 degrees total range of motion if STAB DEGRADE with stab full up
-35 degrees total range of motion if STAB DEGRADE with stab full down
What will cause STAB MANUAL MODE
-Any ADC airspeed sensor becomes invalid
-Miscompare of ADC airspeeds
-FCC failure (Only #2?)
-Stab actuator position becomes unknown
-Stab position transmitter fails
Stab functions
-Streamlines into rotor downwash at low speed
-Collective coupling - minimize pitch excursions from collective input starting at 30 knots
-Angle of incidence decreases with airspeed
-Lateral sideslip - Nose left (right slip) programs down (more rotor wash on advancing side)
- Pitch rate feedback - Hawks tail, dynamic movement to stabilize pitch attitude
Attitude hold - When and what rate when thumbing TRIM switch
Engaged at all airspeeds
-5 degrees per second pitch, 6 degrees per second roll
Heading hold - What airspeeds, what actuator is used, inner or outer loop?
Above 50 = heading hold/turn coordination
below 50 = heading hold
Yaw trim actuator
Outer loop
When is heading hold disengaged and turn coordination engaged
-Trim beeper actuated in lateral direction
-Trim REL switch pressed and roll attitude > 2.5 degrees
-1/2 cyclic displacement with 1 degree roll attitude
-Using lateral AFCS beeper when not coupled to HDG (Standard rate turn)
