What are the Auto Flight Control System (AFCS) components in the PC-21?
- Autopilot and Flight Director System (AFDS), also commonly called the autopilot
- Trim Aid Device (TAD)
Does the AFDS operate independently of the TAD?
What axes does the AFDS control the aircraft?
What does the TAD provide?
Automatic rudder trim
What are the AFDS components?
1) Flight Guidance Computer (FGC)
2) Pitch servo
3) Roll servo
4) Mode Control Panel (MCP) in the front and rear cockpits.
How is the autopilot and related servos powered?
From GEN 1 BUS
How is the autopilot engagement/disengagement circuitry powered?
By the BATT BUS
Where is the FGC located?
In the avionics bay
What are the functions of the FGC?
1) Management of dual axis digital autopilot
2) Control and monitoring of the autopilot or FD state
3) Provision of the FD cue and the autopilot related annunciators on the PFD
4) Provision of auto trim
5) Flap compensation
6) Malfunctions signaling through the EICAS
At what pitch and roll angle is the autopilot disengaged?
If pitch angle is > +- 22 deg and angle of bank > 38 deg
At what pitch rate is the pitch servo disengaged?
> +- 4 deg/s
At what roll rate is the roll servo disengaged?
> +-15 deg/s
At what G does the pitch servo disengage?
> 1.8 g or < 0.2 g
How are the pitch and roll servos connected to their respective control surfaces?
Through control cables.
What component allows the pilot to manually overpower the servo in the event of a mechanical jam?
A built in mechanical slip clutch
What engagement/selection keys does the MCP provide?
What lateral mode selection keys does the MCP have?
What vertical mode selection keys does the MCP have?
What approach mode keys does the MCP have?
What autopilot related switches are on the control column?
- Pitch and roll trim switch
- AP disconnect switch
What is the PCL used for?
- Yaw trim
What does the AP disconnect switch on the Control Column do?
- It disengaged the autopilot and cancels all operating flight director modes
- Auto trim function is inhibited and pitch and roll servos are disconnected
What does the TCS switch do?
It disconnects the pitch and roll servos for such time that the TCS is operated.
Where are autopilot control selections, target datum, autopilot status and the flight director cue displayed?
Where is the flight plan routes and autopilot related cautions and advisories displayed?
What do green autopilot annunciators on the PFD mean?
What occurs when the autopilot is disengaged ?
- AP flashed in red for 5 seconds then disappears
- Aural tone is present as well.
What is displayed on the top left corner of the HUD when the autopilot is engaged?
What occurs if the autopilot data input is invalid?
All indicators are occulted
What is shown on the left hand side of the AP on the PFD?
What is shown on the right hand side of the AP on the PFD?
How is the autopilot powered?
From BATT BUS and GEN 1 BUS
What occurs when the TRIM/AIL PWR switch is operated?
The autopilot will be disengaged to prevent trim runaway.
Where does the FGC receive inputs from?
2) Front PFD
4) SFD provides independent source of intertial data for comparison and monitoring purposes
5) Control column from TCS and AP disconnect switch
6) RIOC 3 sends stall warning discrete input
8) TRIM/AIL PWR
9) Safety monitors
Where does the FGC send outputs to?
1) Pitch and roll servos
What does the AP key on the MCP do?
- Connects the two basic PITCH attitude hold mode and ROLL attitude hold mode
- Flight Director cues are shown on PFD.
Under what 7 conditions is the autopilot disengaged?
1) The AP key on either MCP is pushed
2) The AP disconnect switch on either control column is operated
3) Either pitch trim switch is operated for more than 1 second
4) The TCS switch is operated and the aircraft exceeds +- 50 deg pitch and/or 75 deg AOB
5) The FGC monitors detect parameters exceeding the attitude and reate servos limits
6) Stall conditions are reached
7) Either TRIM/AIL PWR switch is set to the OFF position.
What does the FD cue show the pilot?
- Pitch and roll commands to follow manually.
- When autopilot is engaged, the aircraft follows these pitch and roll commands automatically.
Between what AOB limits will the autopilot function if the AP switch is pressed while the A/C is in a manual turn?
> 6 and < 30 deg
What will occur if AP switch on the MCP is pressed when AOB > 30 deg ?
AP will roll the aircraft back to 30 deg
What will occur if AP switch on MCP is pressed when AOB < 6 deg?
AP will command the aircraft to roll out to wings level
What occurs when the HDG key on the MCP is pressed?
- The aircraft receives steering commands from the FGC to turn to the target heading.
- The heading is set by the HDG rotary switch on the PFD bezel
What does the NAV switch on the MCP do when pressed?
The autopilot will intercept and track various navigations sources.
When the navigation source is VOR, ILS or TACAN, what occurs when the NAV mode is armed through the NAV key on the MCP?
The autopilot follows the roll steering commands to intercept the navigation source on the course (CRS) set by the pilot with the CRS rotary switch on the PFD bezel.
What occurs when the FMS or MC is the navigations source and the NAV mode is engaged?
The autopilot receives roll steering commands to follow the Desired Track of the active flight plan.
What occurs if the NAV mode is selected from the HDG mode engaged?
The aircraft must be on an intercept course with the CRS
What occurs if the NAV mode is selected from the ROLL mode ?
The autopilot will command a lateral guidance to intercept the CRS with an angle of 45 deg.
What does the Back Course mode do?
Gives steering commands to the reciprocal heading for the ILS course.
What is the basic vertical mode when the AP is engaged?
What will occur with the pitch if the AP key is pushed?
The aircraft will hold the current pitch attitude.
Between what angles will the pitch attitude be held?
- If the pitch angle is within +- 20 deg
- If outside this limit, the autopilot with bring the pitch back to converge on this limit.
What will occur when the ALT key on the MCP is pressed?
The autopilot will hold the current altitude.
Can the autopilot be commanded to capture a target altitude?
Yes if PITCH, P/S or VS mode is engaged.
How can target altitude be set?
By the pilot on the ALT function and multi function rotary switch.
What does the Pitch/speed autopilot mode allow the aircraft to do?
Maintain the current airspeed.
How does the autopilot maintain the airspeed?
By altering the commands to the pitch servo.
What must the pilot do to change the commanded IAS?
The TCS must be operated and the aircraft flow manually to the desired airspeed, before the TCS switch is released.
What does the V/S autopilot mode allow the aircraft to do?
Allows the aircraft to maintain a vertical speed.
What is the default V/S speed if one hasn’t been set?
How can pilot change the vertical speed?
- Increment or decrement the target VS value on the PFD
- Operate the TC to fly the aircraft manually to the desired vertical speed.
What does the APR autopilot mode provide ?
A horizontal guidance on a set course during a VOR, TACAN, ILS or FMS approach and a vertical guidance during an ILS or an FMS approach.
What occurs when TCS is pressed, operated for a period and then released?
- If in HDG mode, it will rever to the previous set heading.
- If in NAV mode, NAV will intercept the course if it is intercepting.
- If in APR mode, the aircraft steers back to intercept course and glideslip.
What AOB and pitch angle will autopilot disengaged when TCS switch is operated?
1) +- 50 deg of pitch
2) +- 75 deg AOB
What are the normal autopilot operating limits when AP engaged?
1) +- 20 deg in pitch
2) 30 deg AOB
What will occur if the autopilot is engaged outside these limits?
It will revert to its operating limits values
What are the maximum attitude angles for autopilot engagement?
1) +- 50 deg pitch
2) +- 75 deg AOB
What is the maximum V/S that the autopilot can hold?
+- 6000 ft/min
When will pitch and roll attitude monitors disengage the autopilot, if the autopilot is engaged?
If aircraft exceeds +- 22 deg of pitch and 38 deg AOB
Will the autopilot be disengaged if the EICAS stall advisory comes on?
Can the APR mode function when MC is the primary navigation source?
What is the minimum speed for autopilot engagement ?
1.3 * Vstall
What is the maximum speed for autopilot engagement?
What is the minimum height for autopilot engagement after takeoff?
What is the max altitude for autopilot engagment?
What will occur if the primary navigation source stops transmitting a valid signal?
Automatic NAV or APR modes will revert to basic lateral attitude hold mode.
When is amber AP TRIM caution is displayed on MFD?
If trim monitor detects a fault.
What occurs the pitch and roll servos are disengaged?
1) Red AP disconnect is shown
2) Warning tone is sounded.
What does a grey AP FAIL advisory means?
A failure in the system prevents autopilot engagement