Reason for Engine Shutdown Identified?
10-22-2009, 07:48 PM
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Reason for Engine Shutdown Identified?
We had a great discussion the past couple of days in another thread about why the engine shut down on my Bandit earlier this week. The evidence (a power-fail report from the ECU) pointed to either an intermittent battery connection or possibly a static discharge. I thought of something this afternoon that might explain what happened.
Just before the flight in which the engine shut down, I had the jet upside-down while I attached the wings. When I turned it back upright, one of the satellite receivers had fallen out. I replaced the receiver, finished my prep work, and took off. Normally, the satellite receiver that fell out sits on top of my turbine bypass. Because I've made the last few flights without the lid on the bypass (I installed a new FOD screen and wanted to make sure it didn't restrict airflow around the turbine), I attached the satellite receiver to the inside of the fuse next to the turbine. When I did, I draped the lead connecting the satellite receiver to the main receiver over one of the wing tanks.
If static electricity was generated by fuel sloshing in the tank, it had a direct conduit to the receiver through the satellite lead. In most of the flights prior to this one, the lead sat on top of the turbine bypass and never touched the tank.
We'll never know for sure, but a static discharge from the tank to the receiver through the satellite lead seems like a possibility. In the future, I will be a LOT more careful how I route my satellite leads...just in case.
Just before the flight in which the engine shut down, I had the jet upside-down while I attached the wings. When I turned it back upright, one of the satellite receivers had fallen out. I replaced the receiver, finished my prep work, and took off. Normally, the satellite receiver that fell out sits on top of my turbine bypass. Because I've made the last few flights without the lid on the bypass (I installed a new FOD screen and wanted to make sure it didn't restrict airflow around the turbine), I attached the satellite receiver to the inside of the fuse next to the turbine. When I did, I draped the lead connecting the satellite receiver to the main receiver over one of the wing tanks.
If static electricity was generated by fuel sloshing in the tank, it had a direct conduit to the receiver through the satellite lead. In most of the flights prior to this one, the lead sat on top of the turbine bypass and never touched the tank.
We'll never know for sure, but a static discharge from the tank to the receiver through the satellite lead seems like a possibility. In the future, I will be a LOT more careful how I route my satellite leads...just in case.
10-22-2009, 09:24 PM
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RE: Reason for Engine Shutdown Identified?
Interesting thoughts above. I will say if your ECU showed a PowerFail, you did not have a static discharge shutdown. That I am sure of. When the ECU sees a shot of static electricity and shuts down it will record a "watchdog" for the off condition. A static discharge will trigger noithing else inside the ECU.
I find it odd that you would fly the model with the bypass cover removed. After better than 10,000 plus bandit flights occuring throughout the world for the last 12 years I believe it is proven the cover should be installed per the manufacturers directions. A FOD screen will not hinder air to the turbine much at all in the engine size that lives inside the Bandit. Keep the FOD screen and keep the cover on in the motor department. I personally never use a FOD screen in a bypass installation.
Now for the satelite receiver location and situation. I personally would install it behind the aft engine hatch at the top of the fuselage. Definitely a far better place than directly on top of a solid carbon bypass cover.
A PowerFail is a disruption in power to either the ECU or the Receiver. So lets look at the data. Where any of the remote receivers LED's blinking after the flight? If so then you saw a brown out and would have seen a disruption in power to the receiver. Would love to know what the current battery/power source configuration is for the receiver.
Next question is what is the battery/power configuration for the ECU. Is there a switch installed inline on the ECU battery to the receiver? What were the info readings from the ECU after shutdown. This is that neat little blue button on the GSU, it will give you all kinds of information that can help us detect the failure.
If you have started the engine since the shutdown then all the info inside the ECU is gone. If not it is still there. Would be happy to discuss this with you and help you understand more of what is going on. Call me.
217-778-7680
I find it odd that you would fly the model with the bypass cover removed. After better than 10,000 plus bandit flights occuring throughout the world for the last 12 years I believe it is proven the cover should be installed per the manufacturers directions. A FOD screen will not hinder air to the turbine much at all in the engine size that lives inside the Bandit. Keep the FOD screen and keep the cover on in the motor department. I personally never use a FOD screen in a bypass installation.
Now for the satelite receiver location and situation. I personally would install it behind the aft engine hatch at the top of the fuselage. Definitely a far better place than directly on top of a solid carbon bypass cover.
A PowerFail is a disruption in power to either the ECU or the Receiver. So lets look at the data. Where any of the remote receivers LED's blinking after the flight? If so then you saw a brown out and would have seen a disruption in power to the receiver. Would love to know what the current battery/power source configuration is for the receiver.
Next question is what is the battery/power configuration for the ECU. Is there a switch installed inline on the ECU battery to the receiver? What were the info readings from the ECU after shutdown. This is that neat little blue button on the GSU, it will give you all kinds of information that can help us detect the failure.
If you have started the engine since the shutdown then all the info inside the ECU is gone. If not it is still there. Would be happy to discuss this with you and help you understand more of what is going on. Call me.
217-778-7680
10-22-2009, 10:13 PM
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RE: Reason for Engine Shutdown Identified?
I should have included a link to the previous thread because it answers many of your questions:
[link]http://www.rcuniverse.com/forum/m_9189256/tm.htm[/link]
Many have told me that a static discharge can indeed cause the ECU to report a power failure, although not everyone agrees. I didn't notice any of the receivers blinking, but to be honest, I might have overlooked it. I don't mount the satellite receiver directly on top of the bypass cover; it's on a mount that's glued to the cover. I'm going back to that configuration because the engine seems to run equally well with or without the cover.
Thanks for your help, BTW!
[link]http://www.rcuniverse.com/forum/m_9189256/tm.htm[/link]
Many have told me that a static discharge can indeed cause the ECU to report a power failure, although not everyone agrees. I didn't notice any of the receivers blinking, but to be honest, I might have overlooked it. I don't mount the satellite receiver directly on top of the bypass cover; it's on a mount that's glued to the cover. I'm going back to that configuration because the engine seems to run equally well with or without the cover.
Thanks for your help, BTW!
10-23-2009, 01:01 AM
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RE: Reason for Engine Shutdown Identified?
Jeff
I know what you are feeling I went through the same things earlier this year. I sent the ECU back to Jetcat had them go through it. I also replaced the connectors to the ecu battery just for good measure and piece of mind. It lost power so I did what I could to all the power supply lines to the ECU. I have not had the problem since.
good luck with yours
Sincerely
Justin Sands
BVM rep
Team JR/Horizon
I know what you are feeling I went through the same things earlier this year. I sent the ECU back to Jetcat had them go through it. I also replaced the connectors to the ecu battery just for good measure and piece of mind. It lost power so I did what I could to all the power supply lines to the ECU. I have not had the problem since.
good luck with yours
Sincerely
Justin Sands
BVM rep
Team JR/Horizon
10-23-2009, 09:06 AM
#5
RE: Reason for Engine Shutdown Identified?
Any processor system can suddenly "reset" by static, even if there is a watchdog incorporated. It all boils down to the contents of memory (that is not used by the program running), so by pure luck, a "runaway" CPU can easily go "directly" to reset instead of the WD firing, a lot of chaos is going into this equation!
Isn't it correct that the ECU's with the "#" after the version number identifies the ECU as a "fast" reset type, if a "powerfail" occurs, the engine will be kept running after such a reset situation ?
I have had 1 shutdown because of the "PwrFail" message, this was in a baby boomerang with a P60SE, 4 minutes into the flight. I touched nothing in the plane, and it has since flown 100's of flights (and maybe 50 before it happended), never seen it before (or after) this single incident.
In my honest opinion, I think that there was/is some software bugs inside the ECU, JetCat had in a litlle over a year made many releases of their firmware (which is on one hand good, as it shows that "something" is being done, on the other hand bad, as it shows that something is/was wrong
)
Anyway, I have fairly large number of JetCat's here, and I have never seen any problems with them than this single "PwrFail"
Isn't it correct that the ECU's with the "#" after the version number identifies the ECU as a "fast" reset type, if a "powerfail" occurs, the engine will be kept running after such a reset situation ?
I have had 1 shutdown because of the "PwrFail" message, this was in a baby boomerang with a P60SE, 4 minutes into the flight. I touched nothing in the plane, and it has since flown 100's of flights (and maybe 50 before it happended), never seen it before (or after) this single incident.
In my honest opinion, I think that there was/is some software bugs inside the ECU, JetCat had in a litlle over a year made many releases of their firmware (which is on one hand good, as it shows that "something" is being done, on the other hand bad, as it shows that something is/was wrong
)Anyway, I have fairly large number of JetCat's here, and I have never seen any problems with them than this single "PwrFail"
10-23-2009, 12:40 PM
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RE: Reason for Engine Shutdown Identified?
I don't know Jeff, I'm not very convinced. All the reading and all the statements I've done and seen DEFINATELY point to a very REAL
"black magic" component to ESD.
The most I can sink my teeth into is to make sure there is some large conducting electron sink that the charge can dissapate throughout and back into the atmosphere and/or ground. I.e. just wire all the metal parts together, INCLUDING the fuel tanks somehow....
Raf
"black magic" component to ESD.
The most I can sink my teeth into is to make sure there is some large conducting electron sink that the charge can dissapate throughout and back into the atmosphere and/or ground. I.e. just wire all the metal parts together, INCLUDING the fuel tanks somehow....
Raf
