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HelicopterTurbine Helicopters › PHT3 to exhaust clamping question, but not specific to jetcat
BrooklynJim

Heliman

Starlight, PA

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ive noticed on mine, as well as other helicopters some variations in turbine exhaust mounting, the exhaust does not clamp onto the turbine in some..

all are single wall pipes...

some examples...

1) the turbine exhaust for my bell 230 clamps onto the turbines outlet pipe..

2) in trial fitting the exhaust for my turbine cobra fuse project, its bolted to the side frames but does NOT contact or clamp to the turbine outlet, sits 2-3mm behind it and is a substantially larger overall diameter than the turbine outlet, ide say 6-8mm all around

3) a friends 1/4 hughes, same thing, it doesnt, its mounted to the frame as well and is also spaced 2-3mm behind the pipe and is also oversized in relation to the turbine outlet

4) the NH90 im selling also had the exhaust clamped to the turbine outlet

***************

1) is it to allow suction of cooler air into the exhaust tract?

2) is it clamped to prevent rotor wash from pushing exhaust back into the fuse ( highly unlikely) on vertical exit pipes?

3) we (my hughes friend included) are screwing something up and will burn up our helicopters?

and lets not get into turbine jets.. thats a whole other ball game.. you can fit your fingers between the turbine outlets and pipes..

what gives?

12-01-2016 02:23 AM
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PETER ROB

Elite Veteran

Devon UK

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Jim, To my knowledge with the JetCat/ Vario PHT3 all the exhaust have a 10mm gap all round
As you already stated, it does allow cooler air to be drawn in
If you can check the temperature at the outlet, between direct fit and gap fit, you will notice a lower temperature with the gap fit
Someone will probably say that the exhaust on the Vario Gazelle it a direct fit, this is correct as the mechanics were originally designed for Jakadofsky turbine, and there is not enough space, between side frame, to allow for the 10mm gap
Peter R

12-01-2016 09:26 AM
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BrooklynJim

Heliman

Starlight, PA

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Peter..

hmmm.. ok, but aside from a hotter temp, is there any other detrimental effects of the exhaust being clamped to the turbine?

cause i have to tell ya.. its going to sting taking a flying helicopter and taking it all apart to redesign an exhaust for it.. especially since that helicopter hasnt lost a battle with gravity yet..

anyhow..

can i leave it as is? the fuse is already thermally protected

and yes,, its always gravitys fault.. not mine.. thats my story and im sticking to it!!!

12-01-2016 02:05 PM
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HelicopterTurbine Helicopters › PHT3 to exhaust clamping question, but not specific to jetcat
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