Some JetsMunt engine models (currently VT80BL and M100XBL) include AUTO restart function.
This function can quickly restart an engine automatically in Flight, but it should be understood that such a system may cause damage to people and property.
By default this function is disabled in the ecu, the user should expressly enable it. By enabling this function, the user agrees that he/she has understood the working principles and understands its limitations.
Restart options and how to enable them:
Within the “Radio” menu, a new choice has been added to define the restart operation.
The ecu offers 3 choices:
- Standard operation. After the shutdown the ecu should be reset (power cycled) to enable another startup cycle. Engines are supplied in this mode.
- Manual Start: user can normally shutdown the ecu trough the transmitter (by lowering the stick and trim). The ecu will execute the normal shutdown and post run cooling. Once the cooling is finished (temperature below 100ºC), the ecu will return to power-up state, allowing the engine to be restarted through the normal procedure (Trim-up, cycle stick). The time to shut down and later start is exactly the same as standard operation. This mode is useful for gliders, where the engine is used to climb to height, shutdown, soaring, restart, climb, etc. This mode does not pose any safety hazard.
- Autorestart: In particular case of a fuel bubble that momentarily stops the combustion, the ecu will detect this condition by monitoring the rpm, temperature and pump power, the ecu triggers the auto restart sequence. This sequence is done with the engine hot, so the power is restored quickly. This restarting function can help save the plane in few limited circumstances, but it can also greatly increase the risk of fire, so before to enable this function, please read and understand the following:
What does the auto-restart function do:
It automatically tries to restart the engine quickly and restore the power setting that is being asked by the transmitter.
To trigger this function, the ecu checks:
-the radio signal is valid, no failsafe condition.
-The readings of the RPM are consistent with a flameout condition (the speed of the RPM coasting down is between preset limits).
-The readings of the EGT are consistent with a flameout condition.
-The battery voltage is good.
-No other faults detected.
Once the ecu is satisfied that the shutdown/flameout was most likely caused by an interruption of combustion, usually caused by an air bubble, the ecu triggers the quick restart function, where the ignitor is energized to full voltage and the pump is started at a power dependent of the current engine status (RPM and EGT). Once the ecu detects that the combustion has reassumed, the starter power is set to full power to reach the idle rpm as quickly as possible, and the pump power is increased accordingly to the real RPM increase, allowing for delays caused by bubbles arriving to the engine. If after 10 seconds of restart the ecu doesn’t detect a stable combustion, the procedure is aborted and the normal cooldown initiated.
What the autorestart function will not do:
-It will not restart the engine if the shutdown was caused by any fault other than a typical flame out caused by air in the fuel system.
-It will not monitor and confirm flight conditions are optimum for a restart. Leaving the restart to progress is the pilot responsibility and decision, depending on each particular case.
When should Re-Start function be Enabled?
Restart takes an average time of 15s to establish restored level of pre-shutdown power, including coast down time. It is highly recommended that Re-Start only be used on airframes capable of sustaining enough flight for the re-start to be complete. Some aircraft examples include: lightly loaded planes, gliders, or multiengine planes.
It is highly advised a shutdown simulation be done before selecting Re-Start option in the ECU Menu. Do this during a normal flight at a high altitude and throttle down to idle then begin a 15sec count down. From this try to gauge if the aircraft can maintain flight during this low power setting.
If your plane cannot maintain flight for a minimum of 15sec without engine power, do not enable the restart function.
I’m flying my plane and the engine has shutdown with restart enabled, what should I do:
- Think that the chances of that the engine restart are slim. You don’t know why it has shut down, so likely it will not restart, DO NOT RELY on it.
- FLY YOUR PLANE. Leave the throttle at mid setting and fly your plane for a dead stick landing.
- In case you see the plane begins to stall or an uncontrolled landing is most likely, IMMEDIATELY set the trim and stick to STOP position to abort the restart function. A crash with the engine running normally ends with a fireball; a crash with the engine off is not likely to catch fire. Do not use the “digital trims” to shut down the engine, use a dedicated switch to be operated quickly.
- If the engine restart is initiated while on approach, evaluate the speed/position of the plane is still good for a safe landing, if so, land immediately, you don’t know why the engine stopped and may stop again during a “go around” but this time the aircraft may not be in an as favorable position. If the position/speed of the plane is not convenient, use the engine power to go around and plan for a normal landing, BUT land as soon as possible.
- Once the plane is on the ground, even in normal landing or crash landing, set the transmitter in STOP position. The engine could restart and go to full power on its own; the ecu does not know when the plane is on the ground.
Can I use the restart function many times?
Restart function is an emergency procedure and places a high stress on the engine ancillary components. The starter and ignitor are fed with extra power that is not used in normal startups, this places considerable more wear on them, also the engine is subjected to abrupt temperature changes that could shorten its life.
Restart function is not the replacement of a poor fuel system. It can save a plane in particular circumstances, but it can do much more harm than good. A belly landing or landing gear damage due to a flameout induced heavy landing is more favorable than a similar landing arrival with the engine in start phase that can possibly cause a fire and result in total destruction of the model and or property.
Please Think twice before enabling the auto restart feature.
There are no circumstances Jets Munt P/L or any of its Service Agents and employees will accept or be held responsible for any losses or damages the Auto Restart feature causes should the owner operator choose to enable this function.