Appendix G. Failure Mode Loading.
V3.14 of the CL Software adds failure mode
loading. Use Tab 10 in the Configuration Manager to make the
A single byte FSUIPC offset is used to indicate a
failure mode is active (eg hydraulic systems failure). When failure
is indicated by the offset the CL software adds additional loading
to the affected control axes. The failure loading is ramped up over
a specified transition time.
The additional load components that are available
are Spring Stiffness (cf Lift Gain), Damping and Mass. Reference
should be made to the values for these terms used in the normal
flight loading settings for each axis (Tabs 1, 2 & 3) when setting
the additional values for failure loading.
Implementing effective failure mode loading which is significantly
heavier than normal flight loading requires that the mechanical
transmissions are designed with sufficient loading capacity from the
Therefore the failure load requirements and their effect on
transmission ratios need to be considered at the project design
If the system loading capacity is designed to cover only normal
flight loading then it can be very easy to set additional failure
mode loading which will quickly drive the motors to full output.
This can potentially damage the drive cards if failure conditions
and loading is held for extended periods.
If your system does not have the load capacity for additional
failure loading then it is recommend that only additional Damping is
added in the case of failures. This can be used to generate a
sluggish/heavy feel to the controls in the event of system failures
without substantially increasing the sustained loading magnitudes.
- In Configuration Manager (V1.10 or
later) go to Tab 10 and set Item 1 (Enable Failure
Loading) = 1.
- Item 2 (Failure Indicator Offset) is the
single byte FSUIPC offset read to determine system failure
status. The byte is bit significant -
b0 = All axes failed (= 1)
b1 = Elevator axis failed
b2 = Aileron axis failed
b3 = Rudder axis failed
This offset should be written by the flight sim software or 3rd
party application as required for the failure modes required.
- Items 3 to 11 allow additional Spring
Stiffness (Lift Gain), Damping and Mass settings to be made for
each axis. In the event of a failure being indicated on an axis
the CL software will ramp up these additional loading
Note: An individual component will only be active if it is
active in the normal flight loading settings for that axis. For
example if Mass effects are disabled for normal flight then they
will also be disabled for failure loading regardless of the
setting made here.
- Item 12 (Load Transition Rate) sets the
transition period over which the additional loading is ramped
up. It also applied when the failure offset is cleared and the
failure loading ramps down.
- Remember to SAVE your configuration settings.
The settings can be tested using the Fail_Load
buttons in the Show_Elev, Show Ail and Show_Rud windows. Click the
button to toggle the failure mode loading on and off.
WARNING: Take care with the levels of additional failure
loading that is set. If the mechnical transmissions in the controls are not designed to
deliver the higher levels of failure loading then it can be very easy to induce full
scale output in the motors, which if held for extended periods may
cause heating damage to the cards.