# AFCS (Autoflight System)

The H145 autopilot is a comprehensive autoflight system, capable of both basic stabilization and also fully-hands-off upper modes. The system combines redundant Stability Augmentation Systems with redundant aircraft management computers, which take data from aircraft sensors and send commands to the actuators. The systems are monitored by and interacted with through the MFDs, Autopilot control panel (APCP) and controls on the cyclic and collective.

# Background

The H145 flight controls are augmented by parallel actuators, called SEMAs (smart electro-mechanical actuator). These parallel actuators are invisible to the pilot (not felt in the controls) and are controlled by aircraft computers directly. The SEMA are quick and powerful but limited in travel. The total SEMA travel will be only 10% of the pitch axis and 20% of the roll and yaw axis. For this reason, the AFCS also needs the ability to re-center the SEMA. The A.TRIM (auto trim) system is able to receive commands from the AFCS computers and then slowly drive the trim motor in the requested direction. As the trims move, the pilot sees and feels their cyclic moving. It is for this reason that the A.TRIM system must be engaged to use UPPER MODES, as otherwise the saturation of the SEMA could not be automatically resolved by the computers.

Community member Josh has created a detailed H145 Autopilot explanation video (opens new window).

# Trim Release

Trim Release (Cyclic Trim Release) is a button on the cyclic control which the pilot holds anytime they are manipulating the cyclic. This is a very important aspect of H145 and doing so both pauses the AFCS (so it doesn't fight you) and also gives you maximum precision. There is also a Collective Trim Release, but it isn't as necessary as the cyclic version.

Holding Trim Release is known as Fly-Through Action.

# Follow-Up Trim

Follow-Up trim will allow you to manipulate the cyclic without using trim release, however this will only work well if you also have a very small H145 cyclic deadzone setting. Even still, Trim Release is recommended for all users. Note that Follow-Up trim is only enabled on ATT mode (and submodes). When follow-up trim is active, attitude setpoints will be updated for any deflection.

Follow-Up trim has 4 settings. The Only Hover option is considered the realistic setting, but Off is recommended for learning and understanding the systems.

Setting	Mode
Off	Follow-up trim is never active.
Only Hover	When below 30kias, follow-up trim is active.
Only Cruise	When above 30kias, follow-up trim is active.
Both	Follow-up trim is always active.

# AFCS OFF and A.TRIM OFF Operation

Pilots are to fly with AFCS engaged during all normal operations. A.TRIM OFF is advised for sloped landings or with a heaving deck. Turning A.TRIM off ensures that the attitude change sensed does not result in flight control input that could injure those working around the aircraft.

AFCS and A.TRIM may be disengaged for training purposes at the pilots discretion.

# ATT / Attitude Hold

Attitude hold mode (ATT) is the default autopilot mode and available independently on all 3 axis. Attitude hold mode provides long term attitude stabilization. This mode is also sometimes known as basic autopilot. As it is the default mode, it is not visualized on the AFCS Status Strip.

Engagement: ATT is engaged automatically when at least one SAS is available and no other mode is selected. It is automatically engaged when disengaging any upper mode.

Reference Management: Use Cyclic Trim Release or Cyclic Beep Trim to change pitch and roll attitude.

Fly-Through Action: Hold new attitude.

* - ATT mode turn coordination is inoperative.

# DSAS / Digital SAS

DSAS mode is actually a degraded sub-mode of ATT. It is engaged automatically on any axis when the A.TRIM function is inoperative. The mode provides short term attitude stabilization, however long term stabilization is not assured due to lack of auto trim.

Engagement: A.TRIM Toggle or automatically due to trim failure.

Reference Management:

Use Cyclic Trim Release or Cyclic Beep Trim to change pitch and roll attitude.
Use Collective Beep Trim Left/Right to trim the yaw pedals. Fly-Through Action: Hold new attitude.

# HDG and TRK / Heading Hold

Heading hold mode will use yaw in low speed (less than 30kt) and roll and yaw at higher speeds. Track mode will use a GPS ground track. Use the APCP butterfly knob to change to TRK.

Engagement: HDG Toggle on the APCP.

Reference Management: Cyclic Beep Trim Left/Right will change heading reference.

Fly-Through Action: Return to selected heading.

# VS and FPA / Vertical Speed

VS mode will acquire and maintain a vertical speed. FPA (flight path angle) will use a GPS ground reference. Use the APCP butterfly knob to change to FPA.

Engagement: VS Toggle on the APCP.

Reference Management: Collective Beep Trim Up/Down will change heading reference.

Fly-Through Action: Return to selected VS.

# ALT / Altitude Hold

ALT mode will maintain the altitude at engagement.

Engagement: ALT Toggle on the APCP.

Reference Management: Collective Beep Trim Up/Down will change altitude reference.

Fly-Through Action: Return to selected altitude.

# ALT.A / Altitude Acquire

ALT.A mode will use VS mode to acquire and maintain an altitude. Change the ALT.A reference on the APCP, then engage the ALT.A by pushing the knob.

Engagement: ALT.A Toggle on the APCP.

Reference Management: Collective Beep Trim Up/Down will change altitude reference.

Fly-Through Action: Return to selected altitude.

# IAS / Indicated Airspeed Hold

IAS mode will acquire and maintain an selected airspeed.

Engagement: IAS Toggle on the APCP.

Reference Management: Cyclic Beep Trim Up/Down will change airspeed reference.

Fly-Through Action: Return to selected airspeed.

# GA / Go-Around

GA mode will act similarly to IAS and VS. It executes for 15 seconds in cruise and 25 seconds from a hover.

Engagement: Collective GA press.

Reference Management:

Cyclic Beep Trim Up/Down will change airspeed reference.
Collective Beep Trim Up/Down will change the VS reference. Fly-Through Action: Return to selected airspeed and VS.

# GTC / Ground Trajectory Command

GTC mode will maintain current ground-referenced speeds on longitudinal and lateral axis, as well as heading hold on the yaw axis.

Engagement: GTC press once.

Reference Management:

Cyclic Beep Trim Up/Down will change Vy reference.
Cyclic Beep Trim Left/Right will change Vx reference. Fly-Through Action: Update Vy and Vx references.

# GTC.H / Auto Hover

GTC.H is a sub-mode of GTC and will acquire and maintain a fixed ground-referenced position.

Engagement: GTC press twice.

Reference Management:

Cyclic Beep Trim Up/Down will change the longitudinal position by approximately 1 meter.
Cyclic Beep Trim Left/Right will change the lateral position by approximately 1 meter. Fly-Through Action: Update to new position.

LOC mode will track a localizer in order to conduct an instrument landing.