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HomeTurbineAircraftHelicopterTurbine Helicopters › shorter start motor runs
10-23-2009 08:27 PM  8 years agoPost 1
hazchem88

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W.Mids UK

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I fly a tank of gas,
shut engine down, it goes through its cooling cycle,

then I fill the tank.

but then when I push the throttle to full and down to start the engine the starter only fires for say a 1/3 of the time that it normally does.
It usually takes a few attempty of powering everything off then on to try and get it to start normally.
On a couple of occasions I have had the start on for more than a second (maybe it would go on longer but I shut it down just in case it burns out or something).

I only get this 'unusual' behaviour after its first run of the day.

I can eventually get the starter and start cycle to run OK after a bit of mucking around with powering off etc.

is this normal? is it something to do with a warm (or should I say hot) engine?

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10-23-2009 09:17 PM  8 years agoPost 2
Chris Bergen

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cassopolis, MI USA

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Which motor?

Chris D. Bergen

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10-23-2009 09:24 PM  8 years agoPost 3
hazchem88

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W.Mids UK

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sorry, wren 54

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10-23-2009 09:30 PM  8 years agoPost 4
Chris Bergen

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cassopolis, MI USA

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Next time you fly it, after landing hook up the HDT and watch the cooling cycle.

Fill it up, turn the heli back on, and check the temperature.

I suspect that your temperature has creeped back up, initiating another cool down cycle when you attempt to start it again.

The ECU will NOT allow a start with the temp over 100 C. It will instead do a cool down cycle, then if the temp is less than 100 it will begin a start procedure.

Chris D. Bergen

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10-23-2009 09:49 PM  8 years agoPost 5
hazchem88

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W.Mids UK

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i wondered if it might be something like that.
wasn't sure if a restart straight after a refuel was possible or note

will check it out next time,

thanks chris

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10-24-2009 03:33 PM  8 years agoPost 6
munkey nuts

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wales uk

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can you calibrate the temperature probe ur self. on jet cat you calibrate it at room temp. maybe urs is out.

gaz

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10-24-2009 04:08 PM  8 years agoPost 7
hazchem88

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W.Mids UK

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this might seem a silly question, but why have a cooling cycle anyway?

The hotest part of the engine runs at a few 100degrees C,
surely if it can cope with that, once it's shut down, the temp. will be way below what the engine can cope with.

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10-24-2009 07:55 PM  8 years agoPost 8
seattle_helo

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Seattle, WA USA

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The components running at 100's of °C are designed to do so, of course, and the hottest part of that core is relatively small and limited. If we shut down and have no cooling cycle then "heat soak" can cook other ancillary things via convection. And all else being equal, it's best to cool everything sooner than later simply to help prolong the life of the entire motor.

nick

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10-24-2009 09:34 PM  8 years agoPost 9
Chris Bergen

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cassopolis, MI USA

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While the engine is running, cool air is coming in where it needs to be, and bearings are being lubricated with cool fuel.

After shutdown, none of this is happening and the temp CAN creep up over the allowed limits for soem these components.

Drawing cool air in through the Turbine bring the temps down to a level that the components can handle, as seattle_helo said.

An easy way to check to ensure the engine is fully cooled is this,

After the normal cool down cycle has completed, turn the heli off, then back on again.

Raise the throttle stick up to the top, and back down (do NOT raise the throttle trim however). IF the engine has creeped back up over 100C, then a cool down cycle will initiate AGAIN.

In hot weather, it may take a couple cool down cycles to get the temp down to a point where it won't initiate again.

NOW, after you refuel and attempt another start, it will start off right away without having to cool down first.

Chris D. Bergen

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10-24-2009 09:50 PM  8 years agoPost 10
hazchem88

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W.Mids UK

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thanks chris that explains alot.
didn't realise it would do a 2nd cool cycle. this is what I am hearing.
It just threw me that the starter spins of the 2nd cycle each were much shorter

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