Philip Cooper

Hi,

Hope this is in the correct forum. I have a Jetcat p160se which has been modded to kero start by means of a screw in kero plug.

Runs well, but on shut down it seems to emit a fair amount of white smoke from the FRONT (I assume, smoke from the cockpit) of the engine....which the cool down blows out, but inbetween cool down spin, white smoke is coming from the cockpit...

Its in a Skymaster Viper with the carbon bypass. Its not that burning.

Its only for say 10 seconds after shut off.

Any ideas would be appreciated.

Phil

Dave Wilshere

You have it facing into wind on shut down?

Len Todd

Face into the wind and most guys I see with this type setup use a small blower into the air intake right after shutting down. They usually blow the exhaust out and cool it at the same time. I typically don't see them spend more than 30 seconds with the blower.

scoeroo

My Feedback: (9)

Sounds like stagnent kero vapor -
Face the inlets into the wind, this should be also on start-up face it into the wind

bevar

My Feedback: (27)

Running diesel?

Beave

Philip Cooper

Thanks guys for the reply. Dave I fly at North Weald club and the guys recommended you.

I am running it on parafin with mobile jet oil at 5%.

It was facing into the wind, but there was not much wind... To be honest have used and had a few different turbines, and nothing smoke this much... however my other turbines are smaller than a 160.

White smoke, and a decent amount of it, not smelling too bad, would look like unburnt kero? Could the engine on shut off somehow have some excess fuel from maybe the kero starter?

The engine shut off is a result of the fuel pump stopping and the valve closing? So one wouldn't expect the engine to shut and some fuel still go in? Ie a parameter adjustment in the ECU?

Cheers

Phil

Philip Cooper

To add, the engine is not doing long runs, it has just been fitted in the airframe (didnt smoke on the test stand) and I am starting it, running it for a minute or 2 then shutting off..

Si_B

Dave is the expert on Jetcats, but a quick question. Are you shutting the turbine off at idle, or ramping her up to half throttle before shutting down?

That Viper will go well with a 160 in it!!

Simon

Dave Wilshere

Phil

Check for leaks in the fuel system, any residual fuel in the byepass?
You can get ducting that creates a back draft (suction on the inlets) You could try and run it with the duct cover off. What gap do you have between the back of the turbine tail cone and the start of the tail pipe?

Dave

01923 270405 if you want to talk.

Philip Cooper

Cheers Dave,

I will measure again, but think the gap is around 1.5-2cm to the start of the tube.

This was the first run since I had removed the fuel lines (in the week). Presumably that lets some fuel run into the engine, but would evaporate after a day or so?

Thanks for your number, will call if I cant sort it!

Phil

Dave Wilshere

Phil

Needs to be 2.5-3cm!
Yes, so fuel may still be around but will dry up

Regards

Dave

Philip Cooper

Hi Dave,

Just got the ruler back in there. The gap is actually around 3.5cm or maybe even 3.7cm. It is hard to measure exactly with the bypass as the bypass carbon slots into the exhaust tube a bit, but I would say 3.5cm.

Is that a problem?

Cheers

Phil

Philip Cooper

The exhaust tube inner diameter is around 7.5cm. Its the bigger viper not the 2m.

Dave Wilshere

As long as its not whistling its fine!
75mm dia would be tiny for a P-160, should be 95-100mm

Dave

Philip Cooper

Hi Dave,

This is what the plane came with, its outer diameter is around 90mm, and inner 75. Guy before me had a 160 in it. Its 18.5kg

The fuselage at the tail there is only 11cm diameter. The plane couldn't take a bigger outer dia pipe. I thought a 160 was recommended for the larger viper?

What to do?

Dave Wilshere

You have some mixed up sizes there!
11cm is 110mm that's larger at the back than the front!

Check again!

ww2birds

My Feedback: (14)

For what it's worth, I have had two different turbines in my large SM Viperjet and in both cases, if no breeze blowing thru the plane (facing into the wind on shutdown, as Dave W notes), you get a little white "smoke" (or vapor, or whatever...) out the cockpit area. Something about the way gases flow inside the fuse I guess.

Dave

Philip Cooper

Hi Dave,

Sorry if I wasn't clear. The metal exhaust tube is aprox 75mm (all the way ) internal diameter, say 90mm outer diameter, and the complete fibre glass outside of the plane tail cone is 110mm.

I was suggesting I couldn't get a bigger rat in the hole.

Philip Cooper

If I had a slightly leaky start up valve could the pump pressure be forcing fuel into the kero start plug?

Watch for any fuel movement in the start up tube when its running?

I will taxi test it some more and for a longer run, and it it still does it report back.

Philip Cooper

Hi Dave, not sure if you are still reading this thread, but I have noticed now that the fuel is gone in the kero start tube, from the start valve onwards (ie it will nee re-priming). Looks like the fuel from the start valve to the kero start plug has leaked? I would have thought that with the valve shut, the vacuum effect would mean that the fuel couldn't run down. IE the valve is not air tight, or the tube to the valve is not? However there is no fuel leaked from it....

Cheers
Phil

Dave Wilshere

Phil

The Teflon pipe does not seal very well on the kero plug nipple. Are you using the clamp ring? Remove that, and add some lockwire. Its taking in air through the nipple joint.

Dave

Philip Cooper

Thanks Dave for your help it is much appreciated. I will try your suggestions and see if that fixes it.

Cheers

Phil