Boomerang1

I recently bought a new Jetcat P-60 with the V6.0 ECU.

I can sort of remember a thread with the pros & cons of using one RX channel or two to control
the ECU but cannot find it.

What's the advantages/disadvantages of both setups?

I'm leaning towards the one channel setup because it's similar to the Wren's that I currently fly.

Thanks in advance, John.

icepilot

I have never seen the use for 2 channels, I use one in my F-16 with the JC P180, and I know several guys in
my club are using only one channel, works like a charm![8D]
Tor

KC36330

you can use either one, but if you only use one channel at least plug the second channel in as a backup for receiver power to the ECU, it'll help keep you from getting a 'Power Fail' flame out if receiver voltage should drop unexpectedly.

Jack Diaz

My Feedback: (1)

KC, very good idea !!! I will do it in all of mine.
But, how will it help in case of a receiver momentary voltage drop? I see it more as safety measure against any loose connector or bad contact for any reason

Jack

KC36330

during low voltage conditions there are several thing that can drop your voltage to the ECU (loose power/ground wire, pinched wire, corrosion on the connector, etc....) the two wire hookup just gives you a redundant power source to the ECU and helps insure receiver power is always detected. if you loose signal for any reason for more then 2 seconds the ECU is going to shut down in a failsafe condition. HTH.

flyinfool1

My Feedback: (2)

I use the 2 channel setup.
Main reasons are;
My TX has digital trim so it is inconvenient to move the trim up and down all the time. especially in an emergency.
The AUX input to the ECU is on a 3 position switch, position 1 is Off/normal shutdown, position 2 is run/start, position 3 is emergency shutdown.

The start sequence is simply, put the switch in position 2, move the stick from idle to full. The turbine will now start, the ECU will not hand over control till the stick is back at idle.
As an extra safety I do not move the stick back to idle till I am ready to taxi, this makes it harder to accidentally bump the throttle into action.

With a single channel installation you do not have the option of the emergency shutdown.
The emergency shutdown does just that, it shuts down the turbine and does NOT run the cooling cycle.
I have had to use this once when the jet had a structural failure in flight and I could shut down the turbine so that it was dead before the crash.
If it were in a cool down mode, there would be a greater chance of fire, since things are going to be moving around and breaking up on impact, if there is power going back to the starter for the cool down there is a greater chance of those wires getting damaged in the crash and causing a fire to start, and if a fire started it would be a fan blowing fresh air into the fire and helping it spread.
Also since the turbine is not still spinning it can not suck in the FOD cloud that is likely to occur at impact, thus reducing the potential of engine damage. Jetcat has told me that the rare emergency shutdown will not hurt the engine but do not make a practice of it.

On the other hand, if your radio is channel challenged for the installation, then using single channel is not all that bad so that you can use that channel for something else that is needed.

flyinfool1

My Feedback: (2)

Here is a perfect example of wishing there was an emergency shutdown mode. You can see the air still blowing thru the turbines and relighting the flames.
http://youtu.be/nMxzL7E3Z7s

Duncan

If that's the case can you plug in the second lead, but remove the signal wire so it's possible to plug it into any spare channel where you can't disable the signal, like plugging it into a JR matchbox for instance?

KC36330

no need to remove the signal wire, if you don't have aux control enabled in the ECU it will ignore the input on that line, and yes you can plug it anywhere in the system you wish.





if you watch the whole video he was experimenting with an afterburner, nothing to do with the ECU being single or dual channel.

Gary Jefferson

My Feedback: (167)

The biggest concern with running the two channel method is that you now have a switch on your transmitter that can be accidentally switched off during flight. I have seen it happen to pilots more than once.

When I first started flying turbines I ran 2 channels but the first time I saw someone accidentally hit the switch and shut their turbine off in flight I quit using the second channel setup.

flyinfool1

My Feedback: (2)

I never said single channel caused the fire.
But if you really watch the whole video, you can see that the after burners were most likely the cause of the fires. This we agree on. The afterburners were mentioned at the very end of the vid.
Not being able to stop the cool down made it worse after landing. At the 2:13, 2:27, and 2:56 marks you can see from the smoke that as the cooling spun up the turbine, you can see the smoke (CO2 condensation) start blowing out the back, the flames reignited with the fresh source of oxygen, there was still spilled fuel from the after burner and hot metal parts to provide the source of ignition. Had the turbines not spun up, the nacelles could have remained full of CO2 for possibly long enough for things to cool to below the ignition point. We will never know for sure.

I simply stated my own personal preference and gave the reasons why and then found a vid to back it up.

I have never had a problem with hitting a switch accidentally in flight. That would be the same to me as accidentally giving full down elevator at the end of a low upright pass. It is an incorrect control input by the pilot either way. The only time I have seen someone hit the switch accidentally, they were talking and not paying attention to the task at hand, FLYING. I have also seen experienced pilots that were distracted, give the wrong elevator input at the end of a low pass. The only sure fire way to prevent dumb thumbs is to not fly, or at least pay attention to what you are doing. Think about it.

But then that is why JetCat gave us the choice to pick our poison of one channel or two. Do what works best for you.
The 2 channel option is one of the significant reasons I have not yet talked myself into anything other than a JC.

Boomerang1

Thanks for all the replies guys, seems the only downside is the lack of the emergency shutdown feature.

In Australia our turbine regs require us to have an emergency shutdown independent of the ECU (I drive
the manual fuel valve with a servo to achieve this) so I can see no reason to use both channels.

Like I said earlier this would also mean the start up procedure would be the same as my other engines,
only one switch but it's the one I would get in trouble with! - John

wojtek

My Feedback: (73)

I use two channels on my JC ECUs , however the aux is for control of the pitot tube assisted cruise control mode .. basically put, allows you to turn your left stick from thrust control, to speed control ( within ECU definable ranges ) This is a great feature for scale flying and maintaining uniform flight speeds throughout maneuvers.

Be careful plugging both channels into a powerbox however as under certain configurations it for some reason shorts through the ECU potentially frying the servo wire connectors .. had this happen to me with a P-200 ECU connected through a power box cockpit . There was no damage to the powerbox or ECU but i had some cables melt and smoke [X(] .. I wish i had more info on how / why this happens, but i did not troubleshoot any furhter, and just plugged the cables directly into the Rx

~V~

Boomerang1

Thanks Woj.

I checked the manual (why do we always consult the instructions last? [])
& noticed the Aux channel can also control the smoke pump function.

Thanks also for the tip of the hazard with the Powerbox. I don't use them but
it's always good to know. Perhaps you had the smoke pump function selected
but no pump fitted so the ECU found something else to make smoke?

Clever those Germans. - John.

scraper

How the hell do you think he was "experimenting" with a afterburner? because sum chump on you tube said so? Why on earth would you put a afterburner on a A-10.

The A-10 Is mine, and a shutdown mode on the ecu wouldnt have done a thing! Both ecu's went crazy delivering max power to the pumps. The only thing that would have helped would have been a manual shut off on the fuel line. Eg a servo on a festo ball valve.

scraper

Do you really believe what you wrote? god help us...... lets just go over the crap you wrote

There were NO freaking afterburners on the model! Cool down mode? for a start they were manual start turbines, no on board start here (you can clearly see that at the start of the vid) Both turbines were seized. The reason why it kept igniting was that the pumps were still running at full noise, the only way they stopped was to cut the power to the ecu's, Why did they both fail? i have no idea, im just stuck having to replace 2 turbines.

Pat Barnes

Thanks for clarifying what happened, Scraper. The servo operated ball valve is, IMO, the best (sometimes only) solution for a shutdown if and when the ECU goes haywire (and even JetCat ECU's do this occasionally!). It is the equivalent of the Low Pressure Fuel Cock that is fitted to some full size aircraft. I really like the idea because of it's independence from the ECU, and the risk of accidentally knocking a switch in flight can be minimised by programming a mix to disable the fuel cock switch except in certain modes (eg - gear down and throttle idle, but any combination that suits the individual).

For what it's worth, I operate my ECU using a single channel for simplicity.

Cheers - Pat

ameol

I thought that in two channel operation the manual off only excluded the idle increase for cooling, but still did the cooling cycle after sht down.

flyinfool1

My Feedback: (2)

First I would like to thank you for clarifying this.

Actually I did believe what I wrote based on the evidence at hand.
At the end of the vid when you were asked if you "had given up on the afterburner idea" you acknowledge with a "Yea", both KC36330 and myself both interpreted that to mean the you had some afterburner system in there.
The vid of the start was from behind, even knowing that you said it was manual start, that is not apparent in the vid.

From what you have described my conclusions were incorrect and having a 2 channel setup would not have made a difference. I stand corrected.

Out of curiosity, did you send the ECUs back to the manufacturer to see if they could determine the root cause of both ECUs failing at the same time and in the same way? The engineer in me always wants to know the true cause of any failure.