Autopilots with Manual Navigation Source Selection

The Flight Guidance Control Panel (FGCP) or Flight Guidance Controller (FGC) as it’s called in some aircraft is the autopilot panel with buttons and knobs that controls the autopilot system.

Familiarize yourself with the panel layout by reading the button and knob labels and texts.

In the Learjet 45 the FGC is split into several columns:

• FD1 and CRS1
• Lateral Navigation
• Autopilot, HSI Side, Yaw Damper
• Vertical Navigation
• Altitude
• FD2 and CRS2

The King Air and CRJ-900 are similar but the columns are rearranged compared to the Learjet. They also feature a vertical wheel for the pitch attitude and vertical speed adjustment.

The Q400 arrangement is different with knobs for the CRS, HDG, NAV Source and Altitude moved to the side, the vertical wheel in the center and vertical mode buttons on the left of the vertical wheel and lateral mode buttons on the right side.

The Flight Mode Annunciator (FMA) is the most important instrument when using the autopilot. It displays the currently active control modes of the autopilot as well as changes of the modes. Particularly in aircraft without auto-throttle it is very important to keep an eye on mode changes like the altitude capture activation because as pilots we have to manually adjust the thrust levers or power levers to control our airspeed when this happens.

To change the displayed mode

• Push the buttons on the autopilot panel

The FMA is located in the upper part of the primary flight display (PFD) and in the Learjet 45, Q400 and King Air C90GTx it has a left column for the lateral mode and a right column for the vertical mode. In the CRJ-900 the flight mode annunciator has two rows, the upper displays the lateral modes and the lower row displays the vertical modes.

• Left column (or first row) displays active lateral mode
• Right column (or second row) displays active vertical mode

An arrow in the center or next to AP or FD points to the HSI side (pilot or first officer side) that is currently in use by the flight director.

The flight director is superimposed on the attitude indicator and shows a bank and pitch command.

The flight director in the CRJ-900 has a magenta vertical and horizontal bar that move left and right or up and down to command changes in bank angle and pitch angle.

The flight directors in the Q400, LJ45 and C90GTx are magenta triangles that move up and down and roll left and right to indicate pitch change and roll commands.

To display or to hide the flight directors

• Push the FD1 and FD2 button to toggle the state of the left and right PFD flight director
• In the Q400 pushing the STBY button hides the flight directors when autopilot is off

When both flight directors are off the FMA is blank and the system resets. Turning on the first flight director engages the basic lateral and vertical modes.

The autopilot manipulates the control inputs of the pilots to steer the aircraft. It affects the elevator and aileron inputs but not the rudder directly. The rudder is controlled only by the yaw damper which suppresses the yawing motions, helps with turn coordination and reduces the Dutch-Roll tendency.

When ever the autopilot is turned on the yaw damper is also turned on. You can manually engage the yaw damper without the autopilot but not the other way around.

• Push the YD button to engage or disengage the yaw damper during manual flight

On the autopilot panel you can find a single button to engage the autopilot.

• Push the AP or AP ENG button in the air to turn the autopilot on or off

Note - In all these aircraft the autopilot has to be disengaged before landing. In the Learjet 45 and King Air C90GTx the autopilot disengagement using the yoke takeover button also disengages the yaw damper because you are not allowed to land with yaw damper engaged.

The Horizontal Situation Indicator (HSI) is found in the lower section of the Primary Flight Display (PFD). The HSI course deviation indicator needle can display the deviation from a VOR radial or localizer beam as well as the lateral deviation from the programmed flight plan, computed by the Flight Management System (FMS).

Pilots have to manually select what navigation source they want to display and use for navigation. The selection affects what the autopilot can follow. You first have to select the FMS navigation source to enable the autopilot to follow the route laterally and vertically and you need to select the ILS source before you can capture and fly an ILS approach.

• Push the FMS or NAV button several times to set FMS1, FMS2 or NAV1, NAV2
• Or rotate the NAV SOURCE knob to change through the installed sources
• Or push the NAV/BRG button and select the source from the menu with the knob

We describe how to select the navigation source in greater detail below.

The Flight Management System (FMS) is a computer that stores the flight plan for us and selects the currently active flight plan segment for the autopilot to follow. When a departure or arrival and approach are loaded then the FMS also computes the most economical descent profile to comply with the altitude constraints on the route. The FMS can be programmed using the Control Display Units (CDUs) in the cockpit as described in our wiki-tutorial:

Per default the flight directors are usually already turned on for your convenience. To turn them on manually:

• Fly straight and level and trim out the aircraft
• Push the left and right FD buttons (FD1 and FD2) on the autopilot panel to turn on the flight directors
• Or push the Go-Around button on the thrust lever
• Or select a mode on the autopilot panel

The Flight Mode Annunciator (FMA) now displays the selected lateral and vertical modes, for example:

• HOLD, WING LVL, ROL or ATT
• PITCH, ATT or GA

To successfully engage the autopilot a couple of conditions have to be met first:

1. Airspeed above stall speed and below maximum speed, check that you are not currently flying too fast for the flap setting you have
2. Pitch angle between about 25° and -15° and bank angle less than 45°
3. Flight control inputs neutral and aircraft trimmed out
4. Aircraft in the air at least 100 feet above the ground after takeoff or above 400 feet prior to landing

• Turn on the autopilot by pushing the AP or AP ENG button
• Release the yoke and neutralize your hardware control inputs within one second after the autopilot engagement

We can instruct the autopilot to fly a specific heading. The autopilot will then turn left or right to fly the selected compass heading. The autopilot will turn the aircraft in the direction that you turn the heading knob.

• Push the HDG button next to the heading knob to engage HDG or HDG SEL mode
• Rotate the heading knob to set the desired heading

If you want to set the current heading you can use the heading synchronize feature

• Push the heading knob to set the selected heading to your current heading

The autopilot can maintain altitude for us. We can either climb or descent to the selected altitude and the autopilot will capture it or we can command an immediate level-off at our current altitude.

• Push the ALT button to command a level-off at the current altitude
• Adjust thrust lever or power lever position to maintain desired airspeed

The autopilot will level off and fly back to the altitude at the time of the ALT HOLD engagement and maintain that altitude.

Using the vertical speed mode allows us to set the climb and descent rate directly. The autopilot will target the vertical speed and then level off at the pre-selected altitude once it comes near it.

• Rotate the altitude knob to set a new target altitude
• Push the V/S button to engage vertical speed mode
• Rotate the knob next to the V/S button or rotate the vertical wheel (nose up/nose down) to adjust the target vertical speed
• Adjust thrust lever or power lever position to maintain desired airspeed

The CRJ-900, Dash8-Q400 and Learjet 45 have an airspeed hold function. In this mode the autopilot increases the pitch angle to slow down and pitches down to gain speed. Your thrust lever or power lever inputs then affect how rapidly you climb or descent.

• Rotate the altitude knob to set a target altitude
• Push the SPD or IAS button to engage SPD or IAS mode, the autopilot then pitches the nose up and down to maintain speed
• Rotate the speed knob or rotate the vertical wheel (nose up/nose dn) to adjust the target airspeed
• Move the thrust levers or power levers to change the rate of climb or rate of descent

Note - A very similar mode is the flight level change mode (FLC), which is activated using the FLC button, which is available in the King Air C90GTx and Learjet 45.

To the left of the pilot PFD and to the right of the first officer PFD you can find the EFIS controllers.

• Rotate the NAV SOURCE knob to change the navigation source on the left or right side HSI
• Push the XFR button to change which HSI side is used by the autopilot

The navigation source in the Q400 is adjusted using the knobs in the autopilot panel

• Rotate the NAV SOURCE knob on the left to set the navigation source for the pilot and the knob on the right for the first officer navigation source
• Push the HSI-SEL button to change which HSI side is used by the autopilot

The navigation source in the Learjet 45 is set by pressing the FMS or NAV buttons in the EFIS controller

• Push the FMS button to set FMS1 as source. A second push selects FMS2
• Push the NAV button to set NAV1 (ILS1 or VOR1) as source. A second push sets NAV2 (ILS2 or VOR2)
• Push the XFR button to change which HSI side is used by the autopilot

The navigation source selection in the King Air C90GTx with Proline 21 avionics is using the menu system of the Proline 21.

• Push the NAV/BRG button to display the navigation source and bearing source menus
• Rotate the small knob next to the button until the menu highlights the navigation source that you want to use
• Push the small knob in to confirm the selection and change the source

You can decide which HSI side is used by the autopilot:

• Press the CPL button to change the coupled side

The CRJ-900 can tune the ILS frequency of the destination runway for you automatically, using the auto-tune feature.

You can also manually set the navigation frequencies for the NAV1 and NAV2 receivers using the Radio Tuning Unit (RTU). This device is located in the pedestal. Per default the left RTU controls COM1 and NAV1 and the right RTU controls COM2 and NAV2.

• To edit NAV2 on the left side or NAV1 on the right side push the Page 1/2 button on the RTU first
• Select the NAV1/NAV2 frequency with the second RTU line select key on the right side
• Rotate the large and small adjustment knobs to set the selected standby NAV frequency
• Push the second line select key on the left side to transfer the standby frequency to the active side

The Audio and Radio Control Display Unit (ARCDU) automatically tunes the ILS frequency for us.

To turn off the auto-tuning:

• Rotate the mode knob on the left side of the ARCDU from FMS to BOTH or ON

To then set a frequency:

• Press the line select key next to the ILS1 or VOR1 frequency to select it
• Rotate the large and small knobs on the ARCDU to change the standby frequency
• To transfer the frequency from standby to active push the line select key a second time

The Learjet 45 doesn’t automatically tune the ILS frequency for us but using the CDU we can manually tune the approach frequency still quite easily.

• On the CDU push the NAV button to display the navigation page
• On the right hand side a TUNE APPR option is visible when you are within range, push the option to tune the NAV1 frequency

Using the Radio Management Unit (RMU) we can manually tune any frequency

• Press the second line select key on the right hand side next to the NAV1 frequency
• Rotate the small and large knob of the RMU to set the standby frequency
• Transfer the standby frequency to the active frequency by pressing the first line select key next to the NAV1 frequency

The Radio Tuning Unit (RTU) in the King Air C90GTx works similar to the Learjet 45 RMU and CRJ-900 RTU.

• To set the NAV2 frequency select NEXT PAGE in the lower left first
• Press the line select next to the NAV frequency on the right side
• Rotate the small and large knobs to set the standby frequency
• Transfer the standby frequency across to the active side by pressing the line select key next to the active NAV frequency

To set the course for a particular NAV source we first have to select it.

• Select the NAV source 1 or 2 (ILS1, ILS2 or VOR1, VOR2) for which you would like to set the course
• Rotate the CRS knob to adjust the course of the displayed source

In all aircraft you can select a navigation source on the first officer side and set the course there to prepare the navigation source for later use without affecting the currently engaged navigation source.

In the CRJ900, with FMS1 or FMS2 as active source you can also adjust the ILS course when the ILS source has been preset and is still in standby mode. In the Q400 you can press and hold the FORMAT button on the EFIS controller to display the NAV1 or NAV2 HSI on the navigation display and then rotate the course knob to set the course that way.

To let the autopilot follow the flight plan laterally we first have to select the FMS navigation source and then use the autopilot navigation feature.

• Set heading mode first
• Select the FMS1 or FMS2 navigation source and make sure the HSI selection points to your side
• Push the NAV button on the autopilot panel to arm the route capture

When you intercept the route the lateral FMS or LNAV mode engages and the autopilot turns onto our programmed route.

When an ILS has been tuned we can let the autopilot capture the ILS localizer for us.

• Tune the ILS frequency on NAV1 or NAV2
• Select heading mode first
• Select the ILS1 or ILS2 navigation source that you want to use
• Make sure the approach course is set correctly
• Push the NAV button on the autopilot panel to arm the localizer capture for a LOC only approach or interception
• Or push the APPR button on the autopilot panel to arm the localizer and glide-slope capture for a full ILS approach

When the ILS localizer needle starts moving to the center the autopilot turns towards the selected course and then captures the localizer beam. The active mode then switches to ILS1/ILS2 or LOC1/LOC2.

When a VOR station has been tuned the autopilot can capture a VOR radial, fly to the station, over the station and then fly outbound away from it.

• Tune the VOR on the NAV1 or NAV2 receiver
• Select heading mode first
• Select the VOR1 or VOR2 navigation source that you want to use
• Adjust the VOR radial using the course knob
• Push the NAV button to arm the VOR capture mode

When the VOR needle moves to the center the autopilot turns to the selected course and captures the course deviation indicator (CDI). You can then see the VOR mode activate. When the aircraft gets close to the station it internally switches to a heading select mode and flies the selected course until the station has been overflown. Then it switches back to holding the needle centered.

Only in the Q400 you have to manually arm the selected altitude if you want the autopilot to level off and stop climbing or descending at the selected altitude. In other aircraft the selected altitude is always captured when you fly near it.

To set a new target altitude in the Q400 you need to always do two steps

• Rotate the altitude knob
• Check if ALT SEL is shown in white on the flight mode annunciator. If not: Push the ALT SEL button to arm the selected altitude capture

To disable the altitude capture of the selected altitude

• Push and hold the ALT SEL for about one second

This mode is used quite often in this type of autopilot. In the vertical speed mode we manually command a vertical speed for the autopilot to fly. This gives us direct control over the rate of climb or rate of descent.

• Rotate the altitude knob to set a new target altitude, in Q400 arm ALT SEL
• Push the vertical speed button to engage the V/S mode
• Rotate the vertical wheel (nose up/nose dn) or knob associated with the vertical speed to adjust the target vertical speed
• Adjust the thrust levers or power levers to maintain desired airspeed

Try to limit the target vertical speed between +/- 2000 feet per minute and watch your speed closely. You have manual control over the airspeed with engine thrust or power.

Caution - If you use the V/S mode for climbing the aircraft airspeed can drop too low and the autopilot disengages close to a stall. If you use the V/S mode during descent at set a too high rate of descent the aircraft can fly into the overspeed range and the autopilot disengages.

In the IAS mode the autopilot pitches up or down to maintain a target airspeed. The thrust or power of the aircraft then defines the rate of climb or rate of descent. We as pilots have to manually adjust the thrust or power levers to affect the vertical speed.

• Rotate the altitude knob to set a new target altitude, in Q400 arm ALT SEL
• Push the IAS button to set the airspeed hold mode
• Adjust thrust or power lever position to start climbing or descending
• Rotate the speed knob or vertical wheel to adjust the target airspeed

Note - When you are trying to climb in IAS mode the autopilot might pitch down to regain the target airspeed. Similarly during the descent the autopilot might pitch up and fly a positive vertical speed to loose airspeed. Make smooth adjustments to the thrust levers or power levers as well as change the target airspeed slowly. The FLC mode described next doesn’t have this flaw and is preferred over the plain IAS speed hold.

The Learjet 45 and King Air C90GTx have a flight level change mode which can be used for climbing or descending to a preselected altitude.

• Rotate the altitude knob to set a new target altitude
• Push the FLC button to activate the flight level change mode
• Adjust the thrust lever or power lever position to change the rate of climb/descent

In the FLC mode the autopilot pitches the nose up and down to acquire the target airspeed. However, unlike the IAS mode the autopilot doesn’t just pitch for speed right away, it maintains a positive climb rate or descent rate throughout.

• In the Learjet 45 you can push this button a second time to activate the FLCH, flight level change highspeed mode. Both the FLC and FLCH use a fixed airspeed profile that changes with altitude which differ above 10,000 feet.
• In the King Air you can manually adjust the target airspeed after activating the FLC mode.

The Q400, Learjet 45 and King Air C90GTx all have vertical navigation (VNAV) capability for the descent and arrival part of the route. The flight management system (FMS) computes the optimal target altitude to comply with all altitude constraints during the descent. The vertical deviation is shown on the primary flight display regardless of weather the VNAV mode is used or not. Because this type of autopilot doesn’t have an auto-throttle the VNAV mode is rarely used by pilots in the real world because of the increased workload.

The CRJ-900 displays a target VNAV profile during descent but the autopilot cannot fly it on its own.

• Check that your are flying near the route, ideally the route is flown in LNAV or FMS lateral mode. The vertical deviation has to be displayed next to the attitude indicator
• Select a lower altitude with the altitude knob, in Q400 arm ALT SEL
• Push the VNAV button to arm the vertical navigation mode (VNAV or VNAV PATH)

When the aircraft intercepts the vertical path of the route the VNAV mode engages and the autopilot pitches up and down to stay on the pre-programmed vertical path. You may have to set V/S or other vertical modes to intercept the profile at first.

To fly a FMS approach we first need to program it into the Control Display Unit (CDU) or use the Aerofly FS navigation menu to select it. When it has been inserted we have to position the aircraft in such a way that we can capture the lateral and vertical path of the approach.

• Select heading mode first and fly an intercept to the planned route
• Fly in ALT HOLD, ALTS or V/S mode to be able to intercept the vertical profile
• Select the FMS1 or FMS2 navigation source and make sure the autopilot HSI selection arrow (XFR) is pointing to your side
• Push the APPR button to arm the approach using LNAV/VNAV or FMS/VNAV

When the lateral profile has been intercepted the active lateral mode switches to FMS, FMS APPR or LNAV. When the vertical profile is captured the vertical mode switches to VNAV or VPATH or similar.

Note - You do not need to select a lower altitude for the FMS approach. You can set the selected altitude to your minimum descent altitude for reference but we recommend setting it to the go-around altitude instead once the vertical profile for the approach has been intercepted.

The autopilot is able to fly the ILS down to the approach minimum. After that a manual landing always has to be made, you cannot land with the autopilot engaged in these aircraft. At 50 feet above the ground the autopilot will disengage itself.

To fly the ILS approach we first need to tune the ILS frequency and set the ILS course as described above. We then fly at an intercept heading to capture the localizer first, when LOC captures the glide slope can be captured as well.

• Tune the ILS and set the approach course, ideally on both NAV1 and NAV2
• Use heading select mode (HDG, HDG SEL) to intercept the localizer
• Switch to the ILS navigation source (“green needles”) and make sure the autopilot HSI selection arrow points to your side (XFR)
• If possible set the other HSI to the other NAV receiver (e.g. ILS1 on left, ILS2 on right)
• Push the APPR button to arm the LOC and G/S modes

When the localizer can capture the active mode switches to LOC. When the glide-slope is intercepted then the G/S mode activates as well.

For a VOR or localizer only approach we first have to tune the station and then intercept the VOR radial or LOC beam. The vertical profile is flown manually using the vertical speed mode (V/S).

• Tune the VOR or LOC and set the approach course on NAV1 or NAV2
• Use HDG mode to fly an intercept course and V/S or ALT for the vertical profile
• Switch to VOR1/VOR2 or LOC1/LOC2 navigation source (“green needles”)
• Push the NAV button to arm the lateral VOR or LOC capture mode

When the VOR or LOC are capturing you can see the active mode switching to VOR or LOC.

• Fly the vertical profile using the dive method or the continuous descent method as desired