Hi All,

I hope someone can help as I'm really keen to get some air-time in during this festive break.

I fired up my Predator Turbine on Christmas Eve and all was well. I then retired her to my garage, but the following morning she simply wouldn't start. The starter-motor didn't spin - I got nothing but eery silence. After several attempts I gave up, putting her away in the belief that the ambiant air temperature must have been too cold and the FADEC ECU wasn't allowing things to continue (it was around 1'C)

Today I have just tried to start her again and once more, nothing. This time however I plugged in the Hand Data Terminal and the report I get is "Glow Bad". The turbine has probably had no more than 5 hours of use and I'm not sure what could have changed from putting her away to getting her out again 12 hours later.

I've put a multi-meter across the + and - outputs indicated on the FADEC ECU as being for the glow plug and it measures a constant 7.85V. It doesn't change when I initiate a start, it just stays at 7.85V.

Has anyone any idea what might have happened, or what further tests I could do?

Many thanks,

Ian

Hi Ian

There is a couple reasons you may get that message,

1 Blown glow Plug

2 Connected wrong/loose glo plug lead, or the element not teased out correctly.

As to putting a voltage test on the fadec,it will give you a misleading reading, as the voltage at the plug end is only just over 1 volt,

I tend to connect up the glow and ensure it is touching the case so it is earthed, and see if it glows, when a test is done.
if it blows then you are putting too higher voltage through,re set back to standard settings, if it is glowing but not igniting when you screw it back then tease out the element further to ensure it is in the gas flow on startup..

i flew my predator in - 6 last week with snow, i had no issues at all with start up..so do not worry and think you cannot fly these machines in cold temps.. just keep your gas filler bottle in your pocket, so it keeps warm.

Hi MattJen,

Many thanks for responding so quickly and thanks also for the reassurance that trying to start the turbine in cold temperatures (as long as the gas is warmed) shouldn't be a problem.

I've done some more probing and although I haven't yet removed it, I'm convinced the glow plug must have blown. According to the Hand Data Terminal, my 'Glow plug power' is set to 033 and this is something I've never changed.

However, if I do a continuity test between the outer casing of the turbine and the centre/top of the exposed glow plug, then I get nothing. I'm assuing that a glow plug is just like a light bulb filament, so if there is no continuity then it must have blown?

As for why it might have blown, what still puzzels me is why I'm getting a contstant 7.85V going to the glow plug and I get this even when the 'receiver' battery (which is also the power source for the FADEC ECU) is not connected, only the power source connected which I assume is solely for the fuel pump, starter motor and glow plug.

Is it possible someone could please confirm what voltage they are measuing across the wires going to the glow plug and exactly when they see this voltage, only when initiating a start, or all the time?

Many thanks.

Well, I've removed the glow plug (sorry, I'm rather new to turbines so do everything rather slowly and with an air of caution) and it has defintely blown - one can only assume because it's being constantly driven at 7.85V.

Does anyone have any idea why this might be, and what could have possibly caused it, from being placed in my garage at 15:30 one day and taken out at 11:00 the next?

Hello Ian,

Well the power on the glowplug should not exceed way over 2 Vdc, this can only be measured during startup the gasvalves opens and also the plug need to get powered up. After the gas valves shuts down also the glowplug will stop glowing.

Are you using 6 cell Nimh or 2S lipo to supply power to the fadec?

Ed

I've found on my ECU (Wren 44) that the output will read 7 something volts unless there is an actual load on it. This was the pump output, but I bet the same is true for the glow plug output. When I measured the voltage to the pump during a start sequence it was normal.

The supply to the glow plug is the battery voltage switched on and off rapidly, more off than on. The average is 2.0v or something depending on your Fadec setting. When you attach your meter to it, it can only read either 0v or battery voltage, so, it says 7.4V.

Put another glow plug on it and hold it against the casing, it will light normally.

Peter Wales
http://scalehelicopters.org

As peter said, the voltage is modulated. If you put your volt meter on AC you will get the proper voltage, or better yet just put a glow plug on it and test it out.

Dale

Load "*",8,1

Many thanks to everyone for your helpful advice - and a Happy Christmas too!

As has been suggested, I think my glow plug must have simply died of 'natural causes' and the voltage reading I'm getting is meaningless, either becuase it is 'off load', or my meter isn't detecting it being pulsed.

This being the case (and sorry for asking what must seem like a very elementry question), but will my local model shop which stocks nitro cars/helicopters stock a suitable glow plug, or is the glow plug needed for the Wren 54 turbine unique in some way?

but will my local model shop which stocks nitro cars/helicopters stock a suitable glow plug, or is the glow plug needed for the Wren 54 turbine unique in some way?

They will have the glow plug (there is nothing special about the glow plug, it is a standard glow plug), you will need to get a long plug. Bring in the one you have and they can match it up. You will need to tease the element out of the body. I would get a couple in case you screw up the teasing part.

I use a small jewelers screwdriver to pull out a couple coils out of the plug.

Dale

Load "*",8,1

That's great - many thanks again for everyone's help!

I had a similar symptom, the ecu was reporting a bad glow plug. There was nothing wrong with either the plug or the plug power output from the ecu. Instead it turned out to be a bad cable/connection between the ecu and receiver.

I've had my Wren 44 for about 2 weeks and I've run about 9 lt of fuel through it to date. Today the glo plug decided to die. I replaced it with a OS F four stroke plug, teased out the coil just a little without shorting it and everythings back to normal now.