Running a turbine at full power non stop? Damaging?

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Running a turbine at full power non stop? Damaging? - 7/14/2012 10:20 PM

Pepperpete

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So I've decided that the P-100RX is my weapon of choice for my Tamjets F-16. I was curious if it's ok for me to crank the throttle and simply leave it until it runs out of fuel on the ground? I would like to know exactly how long I have at full power and set my timer for that as obviously I won't be flying full throttle all the time. I don't trust Jetcats own fuel consumption rating as it has been reported vastly wrong in the past. I also don't know the tank capacity as they are not the stock tanks and I got the jet second hand.

Or is there an easier way to truly figure out how much fuel the aircraft holds? My fueler only allows me to pump into or out of the fueling container which makes it almost impossible for me to measure. And then I'm told that our measurement system (Glass measuring cups...Pyrex) are different in Canada than the US. Is it possible to weight the amount of fuel (minus the tanks of course) and get a total then?

This is not my strong suite...

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RE: Running a turbine at full power non stop? Damaging? - 7/14/2012 10:31 PM

FenderBean

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well I know some turbines give you the fuel burn at full throttle, but as far as I know nothing wrong with doing a full run on the ground. I did this with my F-16 to see exactly how long at full throttle my fuel would last. I watch the UAT and as soon as I started seeing it drop i cut the throttle but the it was so fast the turbine flamed out anyway.

also weight of fuel is pretty standard so u can weigh it empty then full to get the exact fuel amount it holds, Jet A is about 6.7lbs per gallon.
if plane is 30 pounds dry, and 34lb wets its pretty simple to say you can hold 4 pounds of fuel and convert it to ounces, my 170 burns 18.5oz a min as full throttle
so so 4lbs is 64oz just divide it by your fuel burn, 64/18.5=3mins and 45sec. just an example my f-14 flamed out around 3:37 and I fly about 5 mins and when I land my main is just starting to drop, but I dont fly full throttle all the time. hope this helps and if anyone seed anything wron with my thought chime in

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RE: Running a turbine at full power non stop? Damaging? - 7/14/2012 10:37 PM

sailing1

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It would sure seem unwise to me to run out of fuel and the lubricatioin that is associated with it while the turbine is at full temp and spinning 130,000 rpms or so. Even more so sitting on the ground with no residual air flowing through it.

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RE: Running a turbine at full power non stop? Damaging? - 7/14/2012 10:38 PM

essyou35

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If you do it inside the jet, its not good as you have no cooling air flow for the fuse. Also, the turbine will heat a bit more on the ground.

Also, in general, the more heat something generates, and the faster RPM, will wear it down faster. This is why real jet engines use TACS (rotations) instead of time to keep track of service intervals. Intuitively, 25 hours at throttle and 25 hours at WOT are not going to be the same wear and tear....

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RE: Running a turbine at full power non stop? Damaging? - 7/14/2012 11:04 PM

ozief16

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Pepperpete,

After chasing fuel system issues in a jet, I found a good solution and now I use it as a preflight check before a first flight

I run th engine at full throttle and figure out max pump voltage. I then set up a 4mm tube out of the ball valve festo back Into my filler jug. Under the test menu you can select a pump voltage the same, or even a touch higher than what your previously tested value was, put a clamp on the change value button on the GSU and run the timer

This also allows you to tilt the plane around and see if you have feed or vent problems without upsetting the neighbors!

Dave

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RE: Running a turbine at full power non stop? Damaging? - 7/14/2012 11:10 PM

Pepperpete

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Thanks everyone for the response and Dave that seems brilliant! Can you tell me the easiest way to tell the pump voltage at full throttle?

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RE: Running a turbine at full power non stop? Damaging? - 7/14/2012 11:14 PM

ozief16

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Pete, it's right on the main run screen of the GSU. I can't remember exactly what it says since its not in front of me, but it'll be about 3-4v depending on the turbine. I can look when I get home if you like

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RE: Running a turbine at full power non stop? Damaging? - 7/14/2012 11:16 PM

Pepperpete

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Thanks! That would be great. I've had Kingtech and Jetcat turbines before I did not notice that the voltage was displayed on the GSU.

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RE: Running a turbine at full power non stop? Damaging? - 7/14/2012 11:59 PM

GSR

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Dont overthink this guys. If you want to run a full tank out at full power go ahead. Remember that turbins flame out at full power all the time due to air bubbles. To be on the safe side just watch the uat and as soon as the main tank is dry and you see the UAT level dropping throttle back and shut down as usual. Another way is put a measured amount of fuel in a dry tank, (say 16 oz or so) run at full power till tank empty and calculate based on tank volume. Scotty

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 12:30 AM

highhorse

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quote:

ORIGINAL: GSR

Dont overthink this guys. If you want to run a full tank out at full power go ahead. Remember that turbins flame out at full power all the time due to air bubbles. To be on the safe side just watch the uat and as soon as the main tank is dry and you see the UAT level dropping throttle back and shut down as usual. Another way is put a measured amount of fuel in a dry tank, (say 16 oz or so) run at full power till tank empty and calculate based on tank volume. Scotty

Best post IMO, is the the part about connecting another tank (commonly called a taxi tank) to the vent line and measuring the time it takes to burn that known quantity (as measured by you)

To find the quatity of your onboard tank, simply make an accurate comparison between the time to fill the taxi tank vs the onboard one.

I wholeheartedly disagree, however, with the notion that deliberately running the engine till flameout at max heat and rpm causes no harm. At the very least, I would rather be conservative and assume it does the engine no good :-)

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 12:32 AM

ozief16

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Pete,

Here's the pic. Obviously the turbine isn't running so the screen shows 0.0V for the pump just right of center on the top row. This is the run screen so if the motor is running you'd see the pump voltage adjusting to control RPM/temp.

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 1:06 AM

essyou35

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I dont think running the fuel pump will work like that, as the valves meter the fuel to the turbine. It will be spitting out much more fuel that way I would think.

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 1:23 AM

ozief16

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Ess,

I think you're right if you run the pump at max allowable voltage (4.5V for the P140).

If, however, you check to see the max voltage with the engine running (I think it was 3.8/9 instead of the 4.5 allowable) and then replicate it, you're close enough for what I think he's looking for (Flight time, leaks in the system, collapsing UATs, etc)).

I've done this with my 140RX and it seemed to work pretty darn well. I've since done it with my 120SX and had similar good results.

Additionally, I'm pretty sure the valve is a simple binary valve...open or closed. The fuel pump actually 'meters' the fuel to the turbine through increased/decreased voltage. You can see this if you run the engine and correlate throttle position, turbine RPM and pump voltage.

Dave

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 1:46 AM

highhorse

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quote:

ORIGINAL: ozief16

Ess,

I think you're right if you run the pump at max allowable voltage (4.5V for the P140).

If, however, you check to see the max voltage with the engine running (I think it was 3.8/9 instead of the 4.5 allowable) and then replicate it, you're close enough for what I think he's looking for (Flight time, leaks in the system, collapsing UATs, etc)).

I've done this with my 140RX and it seemed to work pretty darn well. I've since done it with my 120SX and had similar good results.

Additionally, I'm pretty sure the valve is a simple binary valve...open or closed. The fuel pump actually 'meters' the fuel to the turbine through increased/decreased voltage. You can see this if you run the engine and correlate throttle position, turbine RPM and pump voltage.

DaveL

Concur, the valve does not meter, it's either fully open or closed. That said, I'm sure there is some resistance thru the valve even when fully open. I still lean toward the KISS principle.

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 1:55 AM

Kevin_W

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If you want to know the fuel consumption at full throttle without running the entire fuel system dry you can simply put a known amount of fuel into a ground/taxi tank and run a stopwatch to time how long it takes to drain.

1)Put a known amount of fuel into your ground tank (say 6 ounces)
2) Start your turbine without the ground tank attached
3) Run up to full power then attach ground tank to the vent line and start the timer
4) When ground tank is dry stop the timer
5) Do the math
6) Profit.

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 2:06 AM

Pegasus

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I hook up a new line to the pump put the clunk side in a a graduated cylinder, run the engine until it is close to a random graduated number, go to full throttle, time when it hits the random graduation for 15 seconds full out, mark the spot, times by 4 and you got it. I think everyone would be shocked if they see the numbers they get of any turbines out there.

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 8:54 AM

rfbenn

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Thought I might be able to help here, I have a Jet Legends 1/8th F-16 with a P100 which had its maiden flights yesterday at the Long Marston JMA bash. The tanks are plumbed in series and are 2.6litres or 88ozs(US)
First flight was 6mins 40 secs (pretty accurate as a friend took a video) firstly trimming , then general flying to see how the plane responded,on landing the second tank had only just started to be used.
Second flight with a little more spirited flying of 7minutes and the second tank was just under half full at the end.
The F-16 wieghs 18lb without fuel.
7 minute flights with a reasonable reserve looks likely to be about right as with the P100 you really don't need to use full power much except for vertical climbs.
Hope these figures help.

Rob

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 4:48 PM

Pepperpete

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quote:

ORIGINAL: rfbenn

Thought I might be able to help here, I have a Jet Legends 1/8th F-16 with a P100 which had its maiden flights yesterday at the Long Marston JMA bash. The tanks are plumbed in series and are 2.6litres or 88ozs(US)
First flight was 6mins 40 secs (pretty accurate as a friend took a video) firstly trimming , then general flying to see how the plane responded,on landing the second tank had only just started to be used.
Second flight with a little more spirited flying of 7minutes and the second tank was just under half full at the end.
The F-16 wieghs 18lb without fuel.
7 minute flights with a reasonable reserve looks likely to be about right as with the P100 you really don't need to use full power much except for vertical climbs.
Hope these figures help.

Rob

That is fantastic info as both our F-16s are nearly identical in weight. I'm used to flying electrics that give 4 minute flights with one go around before bone dry. So 7 minute flights will be fantastic. Are you pretty happy with the P-100? Any concerns? What's your AUW when loaded? And thanks again!

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 4:51 PM

Pepperpete

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Just curious but did you notice a change in trim with running the fuel cells in series? How many tanks do you use? Mine has two saddle tanks and a center tank (plus the uat) I was told it's better to run them in Parallel to keep the weight distribution accurate but I would much rather run in series if it's ok to do so. That way I could tell without a shadow of a doudt how much fuel is left.

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 5:33 PM

Kelly W

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I run my old cermark / TJ F-16 with a saddle tank, fed by the 2 main tanks in a parallel setup. I have always looked to see if they are uneven out of curiosity, but I'd guess they were never more than an ounce or two different... Overall a parallel tank setup will give you a lower restriction fuel system, which may pay off in terms of wear n tear on fuel pumps and so on. Its safe to do this, as many will agree, but just make sure to run the fuel lines as symmetrical as you can in length and shape to ensure equal resistance to flow.

Kelly

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 8:03 PM

Pepperpete

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Kelly whats your opinion on running the tanks in series?

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 8:32 PM

B.S.

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I fly with F16 1/8 with 2 x 1 liters tanks in serie with P100RX

My beeper is sat to 6 minutes and is almost 25% left.

One of the great things with the P100 is the low fuel consumption.

(If you want to check your own tanks just fill it up and then reverse your pump and fill a measuring cup)

BR

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 8:41 PM

Aero65

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Hi Everyone
I also have been wondering on how to get a accurate measurement for fuel burn for awhile. Thought of fuel flow meters, calibrated fuel flow etc... all too expensive, complicated or inaccurate. So on the line of the other thinking I came up with this.

I put together a 2 tank bench run tank, and used velcro to mount it to a postal scale that can Tare and has Gram measurement. To get fuel flow you first get your turbine up to 100% then press tare and the stopwatch a moment later (to give time for the scale to read zero) The amount of fuel burnt in 1 min will read in negative grams. Then go to www.convert-me.com and there is a conversion for Kerosene grams to volume.

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 8:45 PM

Kelly W

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Like I said, I ran them in parallel. However, with the JetCat ECUs system of self calibration on the fly, it will easily handle the change in restriction through multiple tanks. The current draw will be higher, and the roll trim may change by a noticeable amount in flight. It comes dow to preference but I wouldn't do it... IMO Those two downsides do not overrule the lower overall restriction and a low probability of uneven fuel burn. I'm currently rebuilding my F-16 (don't ask...

) but I intend to do it again with parallel feeding a hopper, then the UAT.

One other point to consider, in general...
Most ECUs these days will auto calibrate. If you were running an ECU that did not auto calibrate, such as the older 'TEMS' ECU that was used on TJT's and PST turbines for a while, I would recommend against multiple tanks in series. The TEMS ECU was made by GB Hobby in South Africa. The idle pump voltage was calibrated after start up every flight, and my understanding was that the same pump voltage held true for the remainder of the run, unless the user got in and adjusted the calibration with the data terminal. The net result, on a series tank system there would be a few sudden drops in restriction, as one tank would empty after another. This is due to the difference in viscosity between fuel vs air in the lines... Short story, an ECU that doesn't self calibrate would keep the same idle voltage, which in combination with lower restriction later on would produce an abnormally high fuel flow rate at idle and higher residual thrust upon landing.

To be clear, JetCAT and FADEC ECUs are auto calibrating, along with most others that I'm aware of, so the above is probably just a concern for those running older hardware.

Kelly

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RE: Running a turbine at full power non stop? Damaging? - 7/15/2012 10:35 PM

rfbenn

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Mine only has the 2 tanks and a UAT, fuel weighs about 4.5lbs so all up weight with full fuel load is about 22.5lbs.
I chose the series plumbing after reading the review done in RCJI a few years ago as the the writer felt that the tanks were so close together it wouldn't make too much difference to the flying, lets hope he's right.
It meant that you didn't need to to have the identical lenght tubing from each tank as with the UAT being on one side would mean making a loop in one side to lose the extra length.
I did compensate by increasing the size of the tank brass tubing and drilling out both clunks to improve flow/reduce frictional losses.

There was no noticeable effect on flying so far.

As for the P100 it starts easily and smoothly, responds to the throttle really well , all you could want .

Rob

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