SteveR

My Feedback: (1)

I have been flying Jetcat engines for about 5 years and found them to be utterly reliable. On the down side are the constant upgrades to the ECU's which, though sporting more functions invariably leave the turbine performing worse.

I suspect that something has been changed on the later Version 5 ECU's that now leave the engine's very slow to accelarate when in forward flight. One model in particular has been affected by the latest upgrade and the engine, on the ground, accelarates normally (3-4 secs) but in the air the spool up time is around the 10 sec mark. Very hard to fly consistantly with that! I have a fellow Jetcat owner has noticed the same in his model.

What can I do to improve the accel times?

I have wondered if the engine is struggling to pick-up from idle, once the engine note can be heard to change then thrust seems to develop soon afterwards.

Any ideas??

Though I am very happy with the reliabilty of my Jetcats, this accel delay is making me seriously consider another manufacturers product.

Cheers,

Steve

mr_matt

My Feedback: (10)

Hello,

Sorry to hear you are having trouble.

Do you happen to have a way to download the data from a flight into a computer?

I will talk to Bob Wilcox tomorrow to see if he has any ideas.

I will let you know what I can find out.

Regards,

mr_matt

My Feedback: (10)

Hello again,

First some more questions. What kind of plane is the turbine in and what is the firmware version number?

Now to some theories and possible troubleshooting steps.

First, the most likely candidate is some change to the airflow going to the turbine in flight, or a change to the fuel flow. The airflow change might cause a higher temperature and that can slow acceleration, and the fuel flow problem (be it fuel bubbles of vapor lock) would cause not only potentially slower acceleration but lower power.

This is a PERFECT use of the downloading facilities of the JetCat ECU. If you can beg, borrow or steal the adapter and a laptop, download a flight of data and you will be sure of what is happening. Maybe Dave Wilshere can hook you up with the right equipment.

Short of that, the next time you fly, do some ground runs and take careful note of the max temperature at max RPM, and the pump voltage at max RPM. Then just before you take off, clear the maximum readings in the ECU by holding down the "Change Value" key on the GSU while viewing the max temperature and then do it again on the max pump voltage screens. This will clear the max values before the flight, so when you land you might get some idea if the behavior of the turbine is changing in flight.

Let me know what you find out.

Regards,

SteveR

My Feedback: (1)

Thanks for the reply,

The engine is in a non-ducted scale airframe. There are approx 50-60 of these models flying now in Europe so I don't think it is the fault of the non-ducting. (I have 3 models now with no duct and only this one shows these symptoms.) Furthermore the engine ran fine before the change of ECU!

I shall certianly try to check the parameters next time I fly. I don't believe the engine is short of power as the model weighs nearly 20kgs and has very good performance.

If I find that the temperatures are up what do you think would could help remedy the situation?

A friend of mine who also owns a P120 (in a totaly different model) suffers the same problem. Is there something within the latest ECU version that is more susceptable to identifying abnormal parameters and slowing the accelaration accordingly?

I shall have a play next time out, though with the 40-50mph winds we have at the moment it might be a while!!

Thanks again, i'll keep you posted.

Steve