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Reb EMS rotax 915is 3A (specifically

I'm interested in gaining a deeper understanding of the EMS warning light system. My question is not concerned with the advised pilot action in the event of lights illuminating.
I'm more interested in confirming the specific reasons that cause lights to flash, or showing fully on, what the ECU is monitoring in each case.  E.g., Generator zero output, irregular output, etc 

Why?  I have also noted that within my Rotax manual  it details flashing lights as indicative of less serious issues. but within the easy read chart  it confirms the same action as stated within, e.g the POH's of the Bristell B23 and JMB Aviation VL3  both detail flashing A & B as the most serious of issues (both generators failed and use of battery backup to run the engine). 
Ive also read that both lights may come fully on even when they are outputing 12 volts, indicating  any reason between  LOPC up to IFSD (there is no detailed description within the rotax manual of  what LOPC or IFSD are, let alone the in-between reasons).

attached:
ems reasons.pdf >JMB EMS POH page  (note reasons column,my addition)
bristell b23 extract.pdf> Bristell B23 POH pages
ems rotax915.pdf > Extract from Rotax manual

Thanks in advance
J

 

  • Re: EMS warning lights

    by » one month ago


    Julian

    The lane warnings lights indicate the severity of the fault, but not what the fault condition is.  I suggest following the EMS warning light matrix provided in the Rotax 915 operating manual. In general, a solid light is higher risk condition than a flashing light. The actual fault must be diagnosed using the BUDS software, or the information provided by some EFIS.  

    From the list of abbreviations in the 915 Operating Manual:

    LOPC = Loss Of Power Control

    IFSD = In Flight Shut Down

     


  • Re: EMS warning lights

    by » one month ago


    Hi Jeff 
    Judging by the lack of replies to my question, I get the feeling that this is a subject that is poorly understood. accept to follow the matrix blindly.   Off course, Ive read the manual, which actually just adds confusion to the matter.  E.g., the manual  states flashing Lights  are low-risk Yet at least two aircraft manufacturers detail two flashing lights  as basically a complete generator failure. So there's a problem! The aircraft manufacturers state that two flashing lights are as bad as it gets, load shedding and battery consevation while attempting to reach your nearest landing opp bad.


    The ECU is monitoring, E.g the Generator outputs  My question wasn't requesting an after-the event  standard plug in means of identifying faults.  Its very much more related to what specific problems cause the ECU to divert or not. The ECU will be programmed to recognise only specific  circumstances that will or won't cause the lights to flash or illuminate. What are they?

    Regarding:

    LOPC = Loss Of Power Control

    IFSD = In Flight Shut Down.  

    Yes,yes! Nothing new here! I suggest you search these descriptions in the Rotax manual.   You won't find any further detail on them, or more specifically, any reason in between, which is what the matrix  states as a cause for two illuminated lights. 

    Unfortunately, your answer was not at all helpful in any way.  But thanks for giving it ago.

    J

     

     

     

    The lane warnings lights indicate the severity of the fault, but not what the fault condition is.  I suggest following the EMS warning light matrix provided in the Rotax 915 operating manual. In general, a solid light is higher risk condition than a flashing light. The actual fault must be diagnosed using the BUDS software, or the information provided by some EFIS.  

    From the list of abbreviations in the 915 Operating Manual:

    LOPC = Loss Of Power Control

    IFSD = In Flight Shut Down


  • Re: EMS warning lights

    by » one month ago


    Julian

    Regarding an alternator failure, or a dual alternator failure, I have also wondered exactly what the notification would be for this.  I have seen an alternator B failure, but never an alternator A or both failure.  Here is what I know, and also what I assume.  

    If alternator B fails, I know that you will not get any fault notification via the EMS lights. Since alternator B is supplying power to the airframe loads, not the engine, your only notification will come from the EFIS showing a discharge and subsequent decline in voltage of the battery. I have seen this on several aircraft.   

    If alternator A fails, the ECU takes over alternator B, and again the airframe would then be powered only by the battery.  However, with this condition you would get a notification from the EMS lights.  It's my understanding that the indication would be both lanes flashing since both lanes are affected (running on the backup alternator). Also, you would see a gradual discharge of the battery because it’s not being charged.  From the Rotax point of view, the ECU would not see this as the most critical failure, since the engine will keep running on the B alternator indefinitely. However, its logical that the aircraft manufacturers would see this as a critical fault for the overall aircraft because the battery is not being charged. So, in that way, both the aircraft and Rotax operating manuals make sense.  

    If both alternators fail the engine quits immediately as it has no electrical power.  I assume the lanes lights would go red for an instant and then go out since there is no power to the ECU. If there was still some voltage being produced, then the lane lights may remain on (not flashing) indicating a critical low voltage condition at the ECU.  As you already stated, you would then apply the Emergency Power switch and restart the engine.  It’s unclear to me if you would need to cycle the lanes before re-starting the engine, I think that would depend on if the voltage had fallen low enough to drop the ECU out completely.

    There are other conditions that would cause both lanes to flash, say two different sensor failures with one being on each lane. Thus, two flashing lane lights does not indicate a specific condition.  The same is true with two solid lane lights.

    Maybe this will help get the conversation going and we will hear from others who may have a deeper knowledge. 

     


  • Re: EMS warning lights

    by » one month ago


    Julian , Jeff B

    I have imported into New Zealand numerous 915 powered Magni Gyros. I too have made a point of trying to learn more about the 915 electrical system. We operate over some very hostile country especially in the far south west so in my opinion a very sound understanding of the electrical system is essential. To be able to teach this to my customers / students I have undertaken numerous practical tests. Eg gyro chocked & tethered & engine at 3000rpm. Then carefully ( so to avoid frying any components) failed each generator by unplugging.

    Jeff I can verify all you say above is correct from what I have seen. The Magni Gyros do not have a gen B / batt Volt meter only the one on the EMS display. Therefore I fit to out gyros a simple plug in one to a lighter socket. This allows us to monitor  gen B.

    I will in a few days do more checks regarding those few issues your unsure of & report back.

    Pete


  • Re: EMS warning lights

    by » one month ago


    Hi Peter,

    Thanks for sharing the results of your testing.  I’ve seen a few Alternator B failures on earlier 912iS engines.  There is no indication from the Rotax EMS so it’s easy to miss during flight. Monitoring the voltage is good, but the voltage may decrease slowly and won’t alert you right away.  The best instrument for this is an amp meter set up to look at the battery charge/discharge amps. Most EFIS will let you set an alarm, I have mine set at -1 amp.  


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