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loss of r.p.m / thrust

Old 04-27-2010, 02:16 PM
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ron Sweeney
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Default loss of r.p.m / thrust

Hi Marty my TJT 3000 is suffering from loss of thrust. I noticed recently the turbine lacked power on take off but this power improved as the flight progressed. I checked on subsequent flights and the data terminal showed the max r.p.m. was only 122k at take off but was 126k on landing. This situation has now deteriorated to the point where my max r.p.m is 119k and this does not improve and remains at this figure on landing. I noticed that the e.g.t. was 790 c and thought that this may be limiting the r.p.m.
I removed all covers and panels that may have been restricting air flow but this made no difference to either the r.p.m or the e.g.t. I increase the max rpm setting but this had no affect The model installation is quite old and I feed the pump from two pop bottles with felt clunks into a bvm air trap. I am not sure wether there could be a flow restriction or wether the pump would compensate. The radio throttle travel volume is 100% in both directions and I have tried re-setting the ecu learning settings.
Any ideas? Ron Sweeney.
Old 06-07-2010, 11:14 PM
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JET FX
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Default RE: loss of r.p.m / thrust

Hi Ron, The first thing that you need to do is remove either the felt altogether from the clunks if practical or simply replace clunks to standard larger Dubro style. Felt clunks are notorious for restricting fuel flow especially on some larger turbines, I have seen these issues occur before similar to what you describe and problem was traced back to fuel flow restriction caused by the felt clunks. You will find turbine will likely idle fine and due to flow restriction be slow to accelerate and possibly not reach maximum rpm.... Try the clunks and let me know how you go.

Cheers- Marty
Old 06-08-2010, 12:59 AM
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ron Sweeney
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Default RE: loss of r.p.m / thrust

Hi Marty thanks for the reply. I have cured the problem and flown quite a few times since. It was a combination of overstated e.g.t. temperature which and thermocouple position.
I noticed that the e.g.t. was hovering in the high 700s at max r.p.m. and the ecu was limiting the turbine.. At ambient the egt reading was about 15 to 20 degrees too high so I recalibrated it. Also the thermocouple was penetrating too far into the exhaust cone so I reduced this to about 2 mm and it is now back on top form. Regards Ron Sweeney.
Old 07-09-2010, 01:37 AM
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Default RE: loss of r.p.m / thrust

Hi Ron, Glad to here your problems were resolved, yes the thermocouple incorrectly inserted to deep would cause those issues to occur. 2-3 mm inside exhaust tail cone is the manufactured recommended depth for the TJT-3000's thermocouple probe.... I still own a couple TJT-3000's myself and they perform pretty much as good and even better than some of the newer spec turbines Ive seen. They were certainly ahead of their time design wise truly Tonka Tough donks well worth hanging onto ; )

Cheers- Marty

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