Engine Fires...
 

Engine fires really scare me. Especially since I don't have a warrantee. I asked a very experienced turbine operator about them and precautions to take to avoid them. To summarize my answer, he basically said you really have to screw up BAD for one to occur. Initially I thought they just happen every so often, regardless of hoe careful the user is.

I had an experience one the 3rd start on my falcon saturday. At first I was not getting any ignition, I was informed that I didn't have enough gas in the tank. That combined with the OAT in the 20's made for weak starting pressure. After I figured that out my next attempt achieved ignition but went out on "weak gas" I don't remember if that was during the preheat or ramp phase. I'm sure you guys would know. I guess it must have pumped some kero during that event because the next start produced a foot long flame, which went out before reaching an idle. I had 3 or 4 starts after that, all normal.

So as I understand from personal experience, overpriming or a shutdown during the fuelramp can leave kero inside the can. I would assume these 2 things are responsible for most fires/hot starts. Is there anything els that can cause a fire?

If one suspects there is fuel in the turbine what is a good protocol? Do you really tip the jet on its nose and run the starter?

Thanks so much, Pete

RE: Engine Fires...
 

leaving the fuel valve open during refueling is a prime culprit as well....

RE: Engine Fires...
 

Should your shut-off be before or after the pump?

RE: Engine Fires...
 

On my P70 I have it between the Fuel Pump and the T fitting that goes to my Solenoids (The P70 is a Kero Start and if I have it between the Fuel Solenoid and the engine, the Kero start line is not protected from the filling.)

My thoughts on the Falcon (I have one of these as well ready to go into an air frame) I'd put the valve between the pump and the fuel solenoid. For me this will be easily accessible and should stop any undue pressure on the solenoid. I'm sure there won't be to much, but I'd rather be safe than sorry.

George

RE: Engine Fires...
 

I agree, this is the most likely scenario.

Regarding placement; this is a debated topic with proponents on both sides.

If the shut-off valve is before fuel pump you can shut off the fuel source to the pump in case of a "wide open" run of the pump (yes I have seen this once when an ECU 'fried' during a start). If the shut-off valve is after the pump, the fuel pump still has a supply of fuel in such an event. I agree, this is such an unlikely occurrence, but nonetheless plausible. I personally place the valve before the pump if at all possible, but I'm sure other people's mileage will vary.

You may get the other view point shortly.

George

RE: Engine Fires...
 

I think the shutoff valve should absolutely be just before the turbine "inlet", downstream of the solenoid and pump. Thats why it is a shutoff valve.

Let me explain myself.....say if you have a very long fuel line after the pump and the engine catches fire. If the shutoff valve is upstream of the pump, you can still have a lot of fuel trapped inside the fuel line that could still make it to the engine, therefore feeding the flame. If the shutoff valve is closer to the engine, any trapped fuel in the engine feed line would be blocked from entering the turbine.


David

RE: Engine Fires...
 

All due respect guys but this would make the most sense to me, Seeing how you can kill all the fuel immediately. Unless there is concern about putting pressure on the pump or solenoid while refueling. But what do I know..

Im interested in seeing the locations that different people choose and why.

Pete

RE: Engine Fires...
 

Flames can also be caused by too much gas or liquid getting into the engine.
Usually big yellow (low temp) flames out the back won't hurt the engine because the flames are out in the air and not inside. However they can cause problems to the airframe if not confined to the pipe. Long blue flames mean high temps inside the engine.

RE: Engine Fires...
 

Good, I should have mentioned the flame I got was a yellowish redish diffuse flame, Only lasted about 5 seconds.

Now you said "too much gas or liquid" in the engine. Im assuming you mean starting gas in the liquid form. Could an incodent with JUST starting gas be dangerous?

Pete

RE: Engine Fires...
 

As causeitflies says, startup fires generally aren't a big deal unless they cause damage to the airframe. They tend to be short lived.

It helps if you start your model pointing into wind and it is imperative that, if you have to use your fire extinguisher, you point it in the engine intake and not up the exhaust.

RE: Engine Fires...
 

I had a little flame problem this past weekend...
Flames were orange/transparent (Hard to see)

The ECU measured the last temp as 1045 degree centigrade (Well over 2000 Fahrenheit) when the normal full power operating temp should read no more than 600 F

This was not caused at engine startup by the way. this was after about 2 minutes into the flight. Looking at the Elevator and rudder servo leads I think I'm lucky to get it back in one piece (So to speak)

RE: Engine Fires...
 

JetCat quite specifically wants the valve after the pump.

I, however, (based upon my limited model but considerable full scale jet experience) place the valve BEFORE the pump. It's my view that this will ensure that the fuel pump does not have an unlimited supply if it "runs away" as I've read can happen, AND that the flow AFTER the pump will also stop immediately (or almost so) because the pump will cavitate.

I might try an experiment to see if I'm correct.

RE: Engine Fires...
 

I go a little bit farther, in my jets I have one before the pump,
and one after. Just in case the pump starts accidentally.


Hector

RE: Engine Fires...
 

At what point does one decide it is feasable to use the fire extinguisher? What would that scenario be like?

Id imagine the obvious, such as a crash or loss of battery power where the engine is stopped while hot and doesn't enter cool down mode but, how does it work during a start?

Pete

RE: Engine Fires...
 

It depends on the model.

If it is an internal engine and you have a start fire and it hasn't gone out by the time you pick up the extinguisher I would give it a squirt. You shouldn't do any damage to the engine with a CO2 extinguisher.

If externally mounted I would give it a few seconds to see if it clears. If in any doubt then give it a squirt. It is generally a judgement based on experience but it won't take you long to figure out what is right and what is wrong.

p.s. if the engine doesn't enter cooldown then it won't catch fire. Don't use the extinguisher to cool it down in this case; just let it cool naturally. The only model I've seen crash and catch fire couldn't be put out with 4 full extinguishers[X(]

RE: Engine Fires...
 

My point is; if you do what you are saying, then when you shut the valve off after the pump and before the turbine, then the pump is still trying to pump fuel and has a source (the tank/s) and could spray fuel inside the plane if a line or fitting leaks or breaks (Again, I have seen this). If you have never witnessed any situations that can lead to these conditions then I understand where you are coming from. There is nothing better than experience to learn these lessons and your location should be fine 99.9% of the time. I'm just trying to pass on knowledge I have learned and witnessed. Your valve location is up to you.

George

RE: Engine Fires...
 

Exactly!

RE: Engine Fires...
 

Ok thanks, This is my first turbine and turbine jet that Ive ever seen in person. I have not even been to a jet meet so there are loads of scenarios of which I have no idea exist. I didn't know the pump makes enough pressure to rupture fittings.

I guess having one before and after is the way to go.

Pete

RE: Engine Fires...
 

Pete,

Under normal conditions it will not burst lines, just is possible.

And yes, I know you are new, the reason for my trying to help you out. We all want everyone to succeed.

You'll enjoy every minute of it, well most. :D

George

RE: Engine Fires...
 

A good spot for a manual valve is in the 6mm clear line between the UAT and the pump. Locating one next to the motor might actually be hard to reach if there is flame around the motor and for the above reasons.
V..

RE: Engine Fires...
 

George is right on target. I ALWAYS suggest the shutoff valve to be placed before the pump! A runaway pump can either rupture a line or blow the line off the fitting when abruptly closing the valve on the pressure side, IT HAS HAPPENED and the results are not pretty! If installed before the pump, the pump will simply cavitate, no further fuel will enter the engine. If there is nothing entering the pump, nothing can exit!
For safety sake, place the shutoff before the pump ;)

RE: Engine Fires...
 

Just wanted to add that damage to the airframe is not the only thing we need to be concerned about. We also need to consider damage to the pipe itself.

A pipe can sometimes do a great job of preventing a fire damaging the airframe, but become so weakened that it is just a time-bomb waiting to go off ; at some random time later, the weakened pipe collapses and the results are not pretty.

Gordon

RE: Engine Fires...
 

Thanks Gordon. I was thinking "damage to the airframe or to the pipe itself" but forgot to type it.

RE: Engine Fires...
 

Georbeckha, hate to see that man. You can rebuild though. Pete. I am afraid of those fire as well. Thats why I have a Man cut-off in between the fuel solenoid and the turbine itself. When I'm starting, I never cut the Man valve on intill I hear a pop. That way if I don't get a propane light-off I don't pump the turbine full of Jet-A. I have never had a miss-start since i started doing that. Thats if and when all else is right. Plenty of gas, plug voltage right and all that. Good luck

RE: Engine Fires...
 

That is a technique that would really give me piece of mind.

Im a bit confused though, If the ecu doesn't see a temp increase consistent with gas combustion why would the solenoid open up for the Kero? Wouldn't that be a precaution against a shutdown due to improper gas flow?

Pete

RE: Engine Fires...
 

Personally I would be very careful with that technique. As long as you are on the ball it is fine but if you are a bit slow and open the tap a bit late you risk an overtemp.

As Pete says, the ECU shouldn't pump fuel if the gas doesn't raise the temp beyond a pre-set limit. If the gas doesn't light, the fuel shouldn't flow.

RE: Engine Fires...
 

oops

RE: Engine Fires...
 

And, if you forget to open the fuel shut-off valve before attempting a start, which I've never done [sm=red_smile.gif], immediately abort the start. If you open it after the pump has started the ramp and is now trying even harder to build up pressure, and suddenly release it, you are sure to get flames and an over temp with the sudden dump of fuel.

RE: Engine Fires...
 

Pete, The Kero solenoid would still open but it don't know that you have the manual valve off. All the ECU wants to see is that the solenoid did open. It's up to you if you have the manual valve open or closed. It all happens in a matter of a Sec or a little more. Your fuel line is full and when you cut the valve on yourself it's right there in your turbine. Now-I don't know if every ECU is like mine. Mine is a modellbau. Your ECU is not going to send a fuel pump on Sig until it sees the right EGT. The gas ramp up does that. It has never failed on mine. Try it sometimes. Put a valve inbetween your solenoid and the turbine and don't cut it on intil you hear the gas light off, then cut the valve on. I have never had a hot or wet start. if you miss the cue and the jet-A don't make it to the combustion chamber than your RPMs and EGT tells the ECU not to cut on the fuel Solenoid. It's fast matter of timing. Your cue to hit the valve is the gas pop. Let me know how it works for you.
Hooker

RE: Engine Fires...
 

I have never done that either ;)

RE: Engine Fires...
 

georbeckha

What were the results after talking with the folks at Jetcat? Are you still running your fuel pump filter on its side like in the pictures of the Shock Jet? I think they recommend mounting it vertical to eliminate any air that could get trapped. I am interested in learning what is causing your overspead and overtemp problems.

MACE

RE: Engine Fires...
 

Mace,

The first time they said that the speed sensor magnets got demagnetized so it didn't know exactly how fast the engine was running. This caused the shaft to bend and the result was the destruction of the engine, flames and a little singing of the wood.
The pictures up there are of the rebuilt engine doing pretty much the same thing, but this time the flames took hold.

In the picture attached here you can see a white patch in the middle of the runway behind the model. that is where it come to rest. Probably my best landing job so far with the ShockJet. It's amazing considering I was yelling to the peanut gallery that there was a fire and they just sat there watching (They say they didn't hear me) and I was watching the flames eating my plane.

The Filter I have in line was actually standing upright. I think it got twisted around when the fuel line got pulled tight when the engine seized and torqued around.

George

RE: Engine Fires...
 

Pete, i would just run it the way the scematic depicts......Should work great!

RE: Engine Fires...
 

I hate engine fire. This was the aftermath of my first and only engine fire about 8 years ago.

My airplane went from this:

http://image2-1.rcuniverse.com/e1/fo.../13093_521.jpg

to this:

http://image2-1.rcuniverse.com/e1/fo.../13094_521.jpg

RE: Engine Fires...
 

You should have had one of these.... [link]http://www.speedfreaks.net.au/index.php?page=shop.product_details&category_id=10 &flypage=flypage.tpl&product_id=103&option=com_vir tuemart&Itemid=1[/link]

RE: Engine Fires...
 

That says it all, quite agree.

RE: Engine Fires...
 

Do any of you use any form of heat protection on the inside of the fuse where the thrust nozzle is? I would imagine the area around the nozzle and tailpipe gap must be the hottest. I used some heat tape over my servo leads.

Thanks! Pete

RE: Engine Fires...
 

BVM

Has ceramic heat paint that works great. My friend also uses automotive high heat insulating sleeves to run his wires in that area.

RE: Engine Fires...
 

I should have asked if it is even necessary to prep the fuse for heat from the turbine. Wouldn't something like that be provided in the ARF if it was an issue?

Thanks! Pete

RE: Engine Fires...
 

As afar as the valve goes, i like to install it before the pump as well, for the same reasons mentioned here.