Whatever is your preferred simulated flight activity with our AW139, from mountain rescue to off-shore operations, you may have already encountered the need to trim your helicopter. In this article we’re going to explain ho to achieve a proper trim for both rotors and flight controls to ensure your flight is comfortable and efficient.
WHAT IS TRIMMING
Trimming means fine tuning your aircraft’s attitude. This is useful in simulated flights as well as in real ones to achieve maximum operational efficiency in terms of lower fuel consumptions, less pilot’s effort and comfort for your passengers. Trimming is related to each of your axis – pitch, roll and yaw – and each function is nicely reproduced and managed from the cyclic and collective sticks.
FORCE TRIM
As the real AW139, our helicopter spots a force trimming device which allows you to get maximum control over the flight attitude. On the interseat MISC panel you have the Force Trim (FT) switch, when both autopilots are engaged (AP1, AP2 on the interseat panel) this little switch puts the AW139 autopilot from SAS mode (Stability Augmentation System or hands-on-controls) to ATT mode (Attitude or hands-off-controls).
ATT mode enables two distinct functions:
- Couples the Flight Director (FD) to servos. Once a FD mode is selected (ie. HDG, ALT, etc…), this function allows the helicopter to fly autonomously and can be switched off by pressing CPL button (when it’s green) or by putting FT switch back to OFF;
- Freezes your cyclic in position. This function in particular is needed to fly hands-off controls, as in reality. The cyclick stick can be kept in position at the desired forward speed and nose pitch angle. To temporarily unlock the cyclic, keep your hands on it and release the locking system by pushing the FT REL button on the cyclic stick. You can even assign a key or a joystick button to it. Pilots normally leave the FT switch ON.
When ATT mode is ON, the cyclic hat switch trims the cyclic left or right. Pressing it up or down increases or decreases airspeed when IAS (indicated air speed) FD mode is activated. When ATT mode is OFF, pressing it left or right set the heading bug left or right. Pressing it at the center activates the HOV (hovering) mode, see here for details.
CLTV/YAW TRIM
At the right of the FT switch there’s the Collective / Yaw Trim switch. Once activated it allows you to:
- Freeze your collective and pedals in position. Unlock them by using the CLTV/YAW REL switch below the collective stick. You can assign a key or a joystick button to it. When the CLTV/YAW trim switch is ON you can trim the collective up or down with the left hat switch (the one at the right controls the third external light spot below the fuseleage); normally the same hat switch has the function to set the reference target up or down once a FD collective mode (ie. ALTA or VS ) is activated;
- Trim your yaw left or right with the collective hat switch (left one). This function is really useful on longer leveled flights to achieve comfort and optimize fuel consumptions. You can reset the yaw trim by pressing the switch on top;