Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

I have a Yellow Aircraft F-14 that I have been working on for several months. It's powered by twin P-70's. I've had a flame-out on my Flash before and was lucky enough to land without incident. But a flame-out on the twin, that scares me a little.

I've gotten a lot of helpful information recently on these two threads.

www.rcuniverse.com/forum/m_11390404/anchors_11390404/mpage_1/key_/anchor/tm.htm#11390404
www.rcuniverse.com/forum/m_11385864/anchors_11385864/mpage_1/key_/anchor/tm.htm#11385864

It seems like the guys in the know would really like some way to determine a flameout on a twin other than a spin/stall mishap.

The jury is out on wether an indication alone is enough to save the plane but it would at least help you avoid doing possibly the WRONG thing.

We discussed EGT sensors. RPM sensors and measuring the fuel pump voltage.

I think I've come up with a simple solution that takes advantage of our existing $450 flame out detectors .. The ECU's. It seems like one of their main purposes is to detect a flame out and shut everything down.

I've elected to use the Smoker Valve output as my engine running signal out. It would be just as easy to use the Fuel solenoid voltage out.

The Jetcat ECU is set up so that when the turbine is running normally it outputs a +5 volt output for a solenoid to enable a smoke pump. This is to enable smoke oil to spray only when the motor is lit and running. If the motor quits, so does the +5 Volts.

So that is the "running normally" signal, the +5 volts from the smoke pump.

I played around with relays and diodes and resistors to make it so you would have a different voltage output for the Four States: Right Motor Running, Left Motor Running, Both Motors Running and neither motor running.

Since we are only working with a voltage and no current, relays were not needed and I decided on a very simple voltage divider circuit with parallel resistors to each motor.

My goal is to have

Both motors running - Output 3volts
Right Motor Running - Output 1 Volt
Left Motor Running - Output 2 volts
Neither motor running - Output 0 volts

I can then feed this into the External Voltage input on the Futaba Rx and set up an alarm on the Tx to go off if it reads a voltage below 3 volts.

The alarm would tell me I have a dead motor. If I or my spotter looked at the display I could tell which motor is still running, 1 volt for right, 2 volts for left.

I think this would work for any telemetry system that can read and alarm a dropping voltage.

I will post the circuit shortly.

Steve


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RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Great to see this developing!
thanks Steve!

:)

Joe

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

I did the math and here's the circuit I used. For Resistor R1 I used 10K ohm (Brown, Black, Orange) for R2 I used 4.7K Ohm (Yellow, Purple, Red) and for R3 I used 5.1K(Green, Brown, Red).

I did not get a chance yet to do an operational test yet. I was able to hook up the circuit to both ECU's and using the HDU and the Test Functions menu switch on and off the Smoker Relay. On the output I just hooked it up to a voltmeter.

This is what I got.

Neither relay on ... 0 Volts
Left Relay On ... 1.69 Volts
Right Relay On .. 2.59 Volts
Both Relays On .. 3.03 Volts

I'm looking forward to installing this in the plane and hooking it up to the RX and testing it live!! (on the ground of course)http://www.rcuniverse.com/forum/js/f...ular_smile.gif

Steve<br type="_moz" />

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

I wish you luck with this Steve, I have a vested interest. I have been playing with pump voltages in the “Test” mode and believe the voltage readout on the GSU to be pretty accurate, my transmitter had difficulty in reading such small voltage changes to the point where the alarm was inconsistent.

m

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Clever idea,

Steve where is the relay you are referring too?

What I mean is where is the voltage isolation between the ECUs? I am not sure what state that power pin goes into when it is off.

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

On the Jetcat ECU there is an output called "Smoker", it is located just above the fuel solenoid output. The relay is inside the ECU.

You need to program the ECU for "Smoker" operation. I've done it before but I can't remember all the steps right now. Has to do with enabling smoke and using the Aux input setting it to 1 or 2. Whichever on make it on without any input from the Aux Input.

I would think that you could get the same results tapping off the center pin of fuel solenoid output on ECU's without a Smoker output.

When the ECU is programmed for smoke it will send a +5V to the center pin of that output for the smoke solenoid. It's very convenient because it's a regulated, steady 5 volts not dependent on the batteries. I think that will help with the consistency of the output voltage.

Steve<br type="_moz" />

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

I haven't tested it but I think the center pin goes to an open circuit which would be isolated nicely. I guess a pretty good way to check it would measure the resistance from that center pin to ground when it is off.
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RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Would this work only for Jetcat ?

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

It will work for any ECU's that have an output for a Smoke Pump Solenoid.

Mr. Matt brought up a good point about isolation.

If your ECU's dont have a seperate Smoke Solenoid output you could use the +5V going to the Fuel Solenoid. It may work fine as is but it is possibe there may be a trickle voltage that backfeeds through the dead motors fuel solenoid. That could probably be fixed with a diode.

Perhaps someone else out ther would have a better answer.<br type="_moz" />

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

I think I would design it around an XOR Gate, that way when both engines are off or running, the output would be 0, but if either engine is out, the output would be a "high" (design for 5v) , and that would be your trigger for your alarm. That's what I'd do. I'd use the rx power to power the circuit.

Dan

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Hey Sparhawk, thanks for your input.

We have an issue with the Futaba telemetry alarm. It doesn't like an On/Off voltage for a trigger. You can feed it +5 Volts, set the alarm for say below 4 volts. If you go to 3 volts the alarm will trigger. If you go to 0 Volts the alarm WON"T trigger. Not sure why but that's the way it works. I think if it sees 0 volts it just thinks it's not connected and not being used.

Showing different voltages for different motors gives us the limited ability to tell which motor quit which is as important as knowing that we have a failed motor.

Steve

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Ok, let's take it from another angle. Using the XOR, which feeds an inverter, here is what the states would be:
1) both engines off, active high signal to give 5v output, required for the telemetry, ie- no alarm.
2) start one engine, output goes low, alarm sounds
3) start second engine, output goes back to a high, alarm is off
4) if you lose either engine, output goes low causing alarm.

You would need the XOR / inverter output to trigger an output circuit that is 5v active high, but instead goes to a preset output level (3v) when a low is triggered.

Follow?

Dan

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Hey Steve,

OK AFAIK there are no relays in that ECU, so be careful. As you know relays have very high isolation, that ECU smoke output is probably just some TTL level driver. It will likely be fine, but be careful.

Futaba just confirmed that this item should be out by the end of February, it would let you have a completely separate voltage alarm for the second turbine (in addition to the port on the RX). And you are right, you could just check the voltage across the fuel shutoff coil (maybe with a little diode across it to protect from EMF kickback), that should work on any turbine not just JetCat.

http://manuals.hobbico.com/fut/sbs-01v-manual.pdf

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Steve, in your circuit diagram everything would need to be on a common ground. I suppose the throttle lead ground to each ECU already does that to some extent. maybe.

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Matt, thanks for the heads on the output being a solid state type output and not a relay. It shouldn't affect the performance but I'll be extra careful not to short it out. That extra voltage sensor opens up a lot of possibilities. It does seem to take a long time for their products to ever show up in the market.http://www.rcuniverse.com/forum/js/f.../sad_smile.gif

I think this circuit could be easily modified to use fuel solenoid outputs. Maby place a couple diodes just upstream of R1 and R2. There would be a voltage drop accross the diodes so the resistor values might need to be adjusted to show the 3volt, 2volt, 1volt output.

DbSonic, you are exactly right, the throttle input links the two grounds together

I should have actual operational tests by tomorrow, fingers crossed. Matt, I will also try it with the little Robbe Telemetry box you turned me on to.

Steve<br type="_moz" />

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

<span style="font-size: large;">Ok I'm Happy!

<a href="https://www.youtube.com/watch?feature=player_detailpage&amp;v=nrVKjQZQJYU" target="_blank">Tests went well
<br type="_moz" /></a><br type="_moz" /></span>

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

<a href="https://www.youtube.com/watch?feature=player_detailpage&amp;v=nrVKjQZQJYU" target="_blank">

www.youtube.com/watch</a>

Ok I'm Happy!!!http://www.rcuniverse.com/forum/js/f...ular_smile.gifhttp://www.rcuniverse.com/forum/js/f...ular_smile.gif

At 0:36 you can the 1.6 Volts (left turbine only) come up and go to alarm at :41
0:43 the right turbine stabilizes both are running and the voltage displays 3 Volts (both turbines running) and shuts off the alarm.
0:59 I shut off the fuel to the left turbine. 4 seconds later the display reads 2.5 Volts (right turbine only) and the alarm and vibration comes on.

When the Tx is in alarm it is speaking "External Battery 2 point 5 volts" so you can actually tell which motor is out without looking at the display.

Steve<br type="_moz" />

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Cool, I built my own sequencer from an arduino, but decided to use it for just the canopy. The real problem is, any short in the system at all, will cause RX loss while flying.

Do you really want to test a twin turbine jet with your new project, something untested and unproven?

Thats the question I asked my self and decided to keep the arduino separated from the entire RX system. It runs on its own lipo and is operated with a switch on the outside of the airframe to operate the canopy. Perhaps you could optically isolate it and run it off button batteries?

Good luck with this. Hope you have more confidence than I did. I can think of all kinds of cool projects I could do but in the end I feel I was just putting my expensive jet at risk.

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

The point is valid, that this thing should be electrically sound before flying. As a baseline the rx and the ecu are already tethered via the throttle so I dont know that things needs to be opto-isolated. Personally I would want a schematic from Jetcat for the IO drivers of the ECU smoke port and then go through the various states this design can have. I liked the idea of an XNOR because it effectively buffers the drivers from each other. Right now the "off" turbine smoke port will sink the current from the "on" smoke port. Which may be fine but would be reassuring to see the type of IO driver we are dealing with. both fail condition voltages should really be the same assuming the circuit is symmetric...

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Woah lighten up guyshttp://www.rcuniverse.com/forum/js/f...ular_smile.gif. This solution is NOT UNtested ... I tested it last night!!http://www.rcuniverse.com/forum/js/f...eeth_smile.gif

<span style="font-size: larger;">There is no such thing as a foolproof solution in the Model Aircraft hobby because us pilots can always find an ingenious way to defeat it.</span>

Those solenoid output on the ECU are designed to drive a coil with a resistance of 45 Ohms. The resistors in this circuit are 4.5K to 10K ohms. Even if they shorted out were talking 1/1000 the amount of current of the solenoid valve. When not energized the center smoker port has no resistance to ground so it looks like an open circuit.

There is no such thing as a perfect solution. Everything is a risk/benefit solution. The risk with this solution is that some remote unforseen electronic phenomena might occur that would have an unknown consequence. The benefit is I know that seeing 3 Volts on my Tx means everything is fine. If it goes "beep beep warning " one of the motors quit. Reduce power, Lover the nose. And if it speaks "1.6Volts" the Left motor is still running and if it speaks "2.5Volts" the Right motor is running. I will know whether to apply right or left rudder and plan my landing to NOT turn into the dead motor.

When Futaba releases their separate voltage sensor that Mr. Matt mentioned, that will be a better, more isolated solution. You most likely will still need some sort of voltage divider as it probably won't alarm with 0 Volts.

Happy Flying,
Steve<br type="_moz" />

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Steve, where did you get the neck strap adapter for your radio? Been looking for a good one for my 14mz

Dan.

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

I got it here:

www.hobbyking.com/hobbyking/store/__12991__Transmitter_Neck_Strap_Balancer_Futaba_.h tml

I do like it. I had the Factory strap unhook on the stock one, cracked my LCD, that was a bad day!<br type="_moz" />

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Excellent! Thanks

Dan

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

Hello
Great system but How can we do that with the last generation of engine which have internal kero valve? (As the Jetcat RX series?)
Thanks for your help.
regards.
Fifou

RE: Telemetry Flame-out Detector for Twin Turbines .. for less than $5
 

If all you had was the pump output you could use the pwm output to retrigger a 555 via a small capacitor. The output state of the 2 x 555's could be used in the same fashion as the circuit above. The circuit is sort of DC isolated and would not interfere with the pump.
Andre