Flight director Flashcards
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)
When is heading hold re-engaged following a turn
-Within 2 degrees of wings level
-With yaw rate less than 2 degrees per second.
How to use heading hold below 50 knots
Engage both pedals, set heading, release
AFCS trim beeper
When does heading hold engage in a hover
When yaw rate reaches 0, not when pedal switches are engaged.
What is a standard rate turn?
3 degrees per second. 360 in 2 minutes
How do you calculate standard rate turn?
15% of your true airspeed as bank angle.
100 knots = 15 degrees. 10% of airspeed, take half of that, add it.
120 knots. 10% = 12 + 6 = 18 degrees bank
Warning:
-During moderately aggressive approaches, selection of the coupled FD (hover) can result in __________
-In DVE do not engage coupled FD (hover) unless ________
-unpredictable AC responses and excessive rates.
-Unless in a stabilized hover
Caution:
During reduced vis at a hover, crew shall not __________
Shall not depend on coupled FD (hover modes) to recover aircraft in brownout/whiteout
Caution: Beyond pitch attitudes of ________ coupled FD may not be able to recover AC to stabilized hover
25 degrees
State “Logic for IAS mode” after a z axis plunge on cyclic trim beeper
60 to 80 - goes to 80
80 to 120 - goes to current airspeed (Dave nuance)
Above 120 - goes to 120
What about using the coupled FD in ILS mode can overtorque the AC?
If lateral intercept angles are greater than 60 degrees, the glide slope may capture prematurely. If AC is below glide slope, the FD may greatly increase torque.
There is no limiting in which axis of the coupled FD. What responsibility does this leave us?
Collective axis
Dont let mike overtorque
Above what speed do coupled FD functions engage, below what speed do they disengage
50, 48
Max rate of climb/descent in vertical speed?
2000fpm
Radar altitude dial goes to _____ feet. Radar altitude digital readout goes up to
When descending from 2000ft, when would you see the digital readout for RALT reappear? How about the dial?
1050 feet (dial only reads to 1000)
1500 feet
1450
1000
What does Go Around give us?
750fpm rate of climb
70 knots
wings level
If you double tap go around on the cyclic, will it disengage?
What about on the FD?
No, cyclic has “engage only” function
Yes, you can double tap Go Around on the FD engaging, then disengaging it
What happens if you Z axis plunge below 50 knots?
What happens if you Z axis plunge between 50 and 70 knots?
HVR Velocity
FD will capture and engage current airspeed
What happens on the bottom of an ILS captued to ILS glide slope mode, if the pilot does nothing
Rides GS to 200’
ALVL (Auto level off) kicks in commanding a level off at 100’
Radar ALT comes on, captures at 50’ AGL
What does ILS decel give us?
What conditions must be met to use ILS decel?
Can you adjust parameters of ILS decel?
slows to 70 knots by 200ft AGL
AC must be able to achieve 70 by 200 using a 0.5 knot per second DECEL. Aka you cant engage last second and woah boy it.
no
What must be engaged prior to using ILS decel?
IAS, LOC, and GS modes must be engaged to use DECL, and must be far enough out to get 70 by 200’
Max speed for IAS hold?
150?
Hover decel
-How fast does it slow us
-When can I use it
-2.5 knots per second, beep forward for 1.5, back for 3.5
-Below 60 KIAS
What do you get if you press TRIM REL during hover decel?
It will engage hover velocity hold with the present velocities fore/aft left/right
When you are in velocity hold and press TRIM REL, what happens?
It temporarily suspends velocity hold. When you release trim, it will recapture velocity hold with the current velocities
How fast can you go in hover velocity?
60 knots forward
20 knots aft left right
What happens if you have a sick headwind, beep forward for 60 knots in Hover Velocity mode, but hit 60 KIAS at 40 ground speed?
FD will switch from hover velocity to IAS and capture at 60 KIAS
When will Hover position mode automatically engage
When below 1 knot in either hover decel or hover velocity
