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Starting A Twin Turbine Jet

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Starting A Twin Turbine Jet

Old 08-08-2009, 10:15 PM
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BJ64
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Default Starting A Twin Turbine Jet

Can anyone explain the procedure to start a Twin Turbine Jet?

The reason I ask is that I'm fairly new to all this, and have a JJ3000 on a test-bench at the moment, with the view of running a pair of them in a longer-term project I've embarked on. The learning-curve has been rather steep, but deeply satisfying just the same

To start the current single Turbine, the FADEC initially requires calibration of No Stick/No Trim, Full Stick/Full Trim, and No Stick/Full Trim positions so that it can work out if you are trying to start the Turbine, increase the throttle, return to idle, or shut down the Turbine.

In a Twin-Turbine situation, I'm guessing that you'd first need some kind of 'throttle splitter' cable/device so that each FADEC receives the Rx throttle information.

If so, do you start both Turbines together? What happens if one of the Turbines doesn't kick off? How do you then go through the start-up procedure on the failed Turbine while the other one is still running? i.e. to get the duffed one to start, you would need to reset the throttle sticks and trim position - and this would then shut-down the running Turbine, no? Or do you simply shut the whole lot down, and start over?

If you do start them independently, there must be some way to tell the Turbine that starts first to sit and wait at idle while you switch the throttle commands coming out of the Rx across to the second Turbine and go through its spool-up procedure i.e. for the Turbine that's already up and running at idle, my Tx is sitting at No Stick/Full Trim and the FADEC has cycled up to 'running' status. Any throttle changes I make from then on will influence that Turbine.

To get the second Turbine to go through start-up, I have to go from a No Stick/No Trim to No Stick/Full Trim situation. As soon as I'd go from No Stick/Full Trim on the now idling first Turbine back to No Stick/No Trim, it would shut down. Unless there's some way of putting it 'on hold' electronically so that its FADEC still sees the same 'idling' pulse information from the Rx while I jump across to the second Turbine, bring it's FADEC online, and commence its start-up procedure. Is that something that can perhaps be done via the 'Monitor' that you can hook into each FADEC during start-up?

I'm sure there's an easy answer to all of this, as there's lots of twin (and multi-Turbined) models out there.

I just can't figure out in my head how you can start more than one of them given the limited amount of knowledge I have about Turbines so far...

BJ
Old 08-08-2009, 11:58 PM
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David Searles
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Default RE: Starting A Twin Turbine Jet

BJ,

I usually start both turbines together. If set up properly, rarely does one light off and the other fail, but if it does happen and you don't want to start over, their are a couple of solutions.

1. Install an easily accessible power switch between each FADEC battery & the FADEC. Use the switch to turn the power off/on to the non-running turbine. This will recycle the FADEC & allow you to simply move the throttle stick to full for just a moment then back to idle and the start cycle will initiate on the non-running turbine. (The trim was already at full.) The momentary full throttle command will go to the running turbine, but it will be so short that it will have little effect.

2. Set up your throttles on two separate channels mixed together by a switch. Switch on, they are both actuated by the throttle stick. Switch off, you have two separate control and trim positions. You simply use whichever control is necessary to start the non-running turbine. Of course this assumes you're using either a 12X or 14MZ.

In practice, I usually just shut down the other turbine and start over, the few times it has happened.

David S
Old 08-09-2009, 01:14 AM
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Billy
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Default RE: Starting A Twin Turbine Jet

I start them manually. I would encounter a not starting every so often, this way I can give it more gas and try again without shuting down the other. Either way I guess works.
Old 08-09-2009, 01:40 AM
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BJ64
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Default RE: Starting A Twin Turbine Jet

Thanks guys.

I'm running a pretty basic Futaba FP-T17FG/K that a friend has kindly leant me to get my first Turbine up and running on the test-bench. I'm not sure what I will go for further down the track when it comes time to get a decent Tx/Rx - I've spent a squillion on plugs, moulds, a single Turbine, simulator software and hardware, some 'trainer' aircraft and all the other odds-and-sods so far to get this rather ambitious 'project' started. I know I'm going to need at least 9 channels before I blink - a 12 or 14 would be ideal (there's always something nifti you can do with any 'spare' channels, so I've read LoL).

It's pretty confusing out there regarding what is 'better' - Spektrum, Futaba, Aurora, JR etc etc etc. Whichever way I end up going, it sounds like 2.4GHz is the way forward and I particularly like the sound of Rx's that can bind to the Tx so that you virtually can't get any stray signals affecting your craft. The 'double channel' thingies sound like they make it almost bullet-proof.

The high-end stuff sells for around 3 grand down here, but I guess it's like anything - if you want something decent, you have to pay for it - so long as the quality, performance and future-proofing are there I guess it's worth it in the long run. But that's a whole 'nother ball-game, and I'll probably be pestering everyone in other Forums when I get that far...

BJ
Old 08-09-2009, 06:10 AM
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CraigG
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Default RE: Starting A Twin Turbine Jet

BJ,

I use the same method as Billy. It's generally best to start them individually because you do get the occasional bad start and it's a lot easier to deal with. If you get to the point where both are starting reliably and consistently, then David's method of starting both is fine.

David is also absolutely correct in recommending an easy method to disconnect and/or recycle power to your ECU's individually. Otherwise, you have to shut down both engines, wait for them to cool etc., prior to restart.

JetCat gives you the option of starting twins individually from the TX or manually via the GSU. Not sure about JJ. If not, you might consider this product from Mini Hobby: http://www.minihobby.com/electronics/twin.htm I used something similar from them during my twin engine ducted fan days and it worked great.

Craig
Old 08-10-2009, 07:56 AM
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BJ64
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Default RE: Starting A Twin Turbine Jet

Thanks Craig.

I've got a few options open to me now, as well as buying the minihobby lead.

Next cab off the rank is to get my hands on the second Turbine and have a bit of a fiddle...

BJ
Old 08-10-2009, 08:38 AM
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ddennison
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Default RE: Starting A Twin Turbine Jet

Regarding the Jetcat twin manual start-up,

Will the GSU automatically give control back to the RC/Tx once stabilized or do you need to hit a command on the GSU to transfer control back?

I just setup my two v6.o ECUs on p120s for my A10....Ready to test run....

Thanks
Dave
Old 08-10-2009, 08:29 PM
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CraigG
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Default RE: Starting A Twin Turbine Jet


ORIGINAL: ddennison

Regarding the Jetcat twin manual start-up,

Will the GSU automatically give control back to the RC/Tx once stabilized or do you need to hit a command on the GSU to transfer control back?

Thanks
Dave
Here's how you do it Dave;

Hook up your GSU to one of the turbines, turn everything on and put the throttle trim to HI (but keep the throttle at idle). Push MANUAL and IGNITION simultaneously on the GSU and the start sequence will begin. After the engine is started and after the LEARN LOW message goes away, control is automatically transferred over to the transmitter. Plug the GSU into the other engine and start it the same way. The first one will stay in idle because that's where the throttle is the whole time.

You can manually switch control back and forth between the GSU and Tx by pushing IGNITION and SELECT MENU simultaneously. You can stop a manual start with the GSU by pushing MANUAL and IGNITION during the start. You can use two GSU's with one hooked up to each turbine or just one as described above.

After you have started both engines manually, run them up a little to be sure both are being controlled by the transmitter. I managed to takeoff once with both engines runnng but only one responding to the tx. That's when I learned to have to wait until after LEARN LOW to advance the throttle. Other wise is cancels the auto switch to the tx from the GSU.

Craig
Old 08-10-2009, 10:53 PM
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ddennison
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Default RE: Starting A Twin Turbine Jet

Hi Craig,

Thanks for the lesson!

Darrell is sending my stuff to be here tomorrow..we'll see, the maiden may be back on track.


Once I get the scale work done it would be fun to get some of these together!

Dave

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