Wren 44 Gold Helicopter Owners Manual
Page 26
ECU FAILSAFE FUNCTION
The ECU contains a failsafe function that will stop the engine in the event of loss of radio link or
continued radio interference that masks the normal signal, but will allow the engine to continue to
operate in the case of short glitches. The system works with PCM, PPM and IPD systems.
PPM systems
In case of loss of radio link, corrupted or signal pulses outside the programmed window of
operation, for the first 0.5 secs the FADEC will do nothing and keep the engine at its last valid
setting. If during this time the radio link is recovered or signal pulse-width returns to within the
programmed window, control is returned.
If after this 0.5secs the signal still is missing or bad, the FADEC will command the engine to
"idle", and keep it at idle for a further 1.5secs. After this 1.5secs (total 0.5+1.5secs=2secs)
the FADEC will command the engine to shutdown.
If the signal returns during this 2s, the FADEC will take this signal as good and reset the
2secs timer and engine control will return.
PCM/IPD systems
The user should program the “failsafe” function of the radio to send a signal lower than the
normal “stop” signal (ie if normal “stop” is –100%, then program the failsafe to output –125%).
When the receiver enters into "failsafe" mode, it will issue a signal to the FADEC of -125%
that is outside the valid command window, (between STOP (-100%) and Full power
(+100%) . In this case the FADEC will follow same procedure as described in PPM mode
and shutdown the engine after 2s of failsafe. In this event the FADEC will record the cause of
shutdown as a “Failsafe” shutdown.
If the failsafe setting is programmed on the TX to the same point as the “STOP” command,
the system will act exactly the same, except that the FADEC will record in its memory that
the cause of the last shutdown was "User-Off". This could make it more difficult to
troubleshoot a in-flight shutdown.
This system allows the engine to fly through minor interruptions of signal or glitches, thus
avoiding the engine shutting off unnecessarily, while maintaining the safety of automatic
shutdown in cases of loss or corruption of radio link.
IMPORTANT - ALWAYS PROGRAMME THE FAILSAFE TO SHUT OFF THE ENGINE.
NEVER FLY A TURBINE HELICOPTER WITH THE FAILSAFE SET TO “HOLD”.
