HarryC

My Feedback: (1)

I am having some odd behaviour from my 600R, any ideas what I should do? Does it needs servicing etc?

In recent weeks I have had to use the auto calibrate full throttle a few times because full power revs were down in the mid 140k to 150k. It never remained working from one day to the next, I had to auto calibrate at the start of each day. This after 3 years of faultless operation. I had to replace the fuel pump a few months ago and initially put it down to the settings needing adjustment as the pump bedded in, but the need for adjustments has become more, not less, frequent.
I have been having problems getting to fuel ramp during start up because the temp isn't high enough on gas and the thermocouple seemed to be under reading the running temp, so before flying today I carefully adjusted the tip to what the instruction manual says, no more than 2mm into the jet pipe. This under read the temp so badly that at full power it read around 350C and coming back to idle was 250C and the ecu shut down the engine. So I pushed the tip in as far as it will go, around 4-5mm and now it reads realistic temps around 650C at full throttle and somewhere in the 400s at idle, and starts instantly too.
But on every start up today I couldn't get more than 145-155k rpm and had to use autocalibrate before every flight, and then the idle rpm was 60-65krpm instead of 55k and I had to adjust that - before every flight! It's not holding the settings from one flight to the next. I also noticed on slamming the throttle up that it pauses around 145k rpm for say a second and then bangs up to 160krpm. It never used to do that. There are no odd noises from it at any stage of operation. During autocalibrate it has no problem reaching full rpm. Unfortunately I didn't think to check what the pmp values were on each run.

This engine has been a paragon of reliability for the last 3 years. What's going on now?

Harry

B777

Hi Harry,

The problem is patly pointing to the fuel line. Please check that there is no restriction in the fuel system and that all filters, including the one inside the engine front cover, are not clogged. On your next run, please observe the pump battery voltage at idle and max rpm. At full throttle, the pump should be using around 5V. If the voltage is excessively over 5V, there are restrictions in the fuel system or the pump itself is going bad.

While you have the front cover open to check the filters, please make sure that the gas and fuel lines are in good condition. These lines can become brittle after 3 years depending on usage and storage time.

After checking all the plumbing and filters, recalibrate again at your next start before flying.

Hope that the above will help. Please do not hesitate to contact us direct at [email protected]

Regards,
Kraivuth S.

HarryC

My Feedback: (1)

Will do, thanks Kraivuth.

Harry

HarryC

My Feedback: (1)

You are right on target there Kraivuth, the filter inside the cover was restricted with a coating of very fine particles. I haven't had an opportunity to run the engine since cleaning it but it is just about due another service so I think I will send it back to the factory anyway and let them check it thoroughly.

The instructions say the thermocouple must be no more than 2mm inside the tailcone. If I do that it under reads by maybe 200degrees. It works if I push it in about 4mm. Does that indicate a problem?

Harry

B777

Hi Harry,

Thanks for the info. We recommend that you run the engine again and see if it is still operating normally with no unusual noise and vibration before sending the turbine for service.

My only guess is that thermocouple's material and sensitivity may have been deterorated with operating time. Even if the probe's tip is designed to withstand high temperature, repetiitve exposure to turbine's operating environment may have effect on the sensitivity. Aging?

Regards,
Kraivuth S.

HarryC

My Feedback: (1)

If it is working normally do you suggest not sending it for a service until it seems to need it?

Harry