Mr Matt,

I have P-120 that has 2hr 34min runtime on it that rec'd a fuel failure today about 3min 43s into the flight. Caused some minor damage to the airframe as I was unable to make it back to the runway. It was straight and level flight, about 73k rpm. I did not see the "white plume of smoke" to indicate an air bubble. Last off condition was "fuel failure". I checked the parameters that show the last 8 seconds of flight in .2 second intervals. Throttle stick never changed for those last 8 seconds. (pulse width the same all the way through). I am showing you the last 8 seconds to see if you can determine why I may have seen this fuel failure.

Was there any fuel left in the UAT??

UAT was full.. I willl double check tonight when i get back home.. but i am pretty sure it wsa full..

thanks
Sean

The pump was working harder trying to maintain throttle position so either you ran out of fuel or the supply was blocked causing starvation.

Check all your lines and backflush all your filters.

Bob

Thanks for the reply's gonna try to run the pump tonight by disconnecting the fuel line at the turbine and manually running the pump. See if that shows anything. Gonna try not to disturb the tubing. (the hard landing may have done that for me though)


thanks
Sean

Hi Sean,

Do you have any record of your max pump voltage (at max RPM) trend? In other words, was the pump working consistently harder "flight to flight" to keep the power up?

This is a very important indicator of the effectiveness of the pump and the plumbing (including the filter) going to the turbine.

Regards,

Sorry matt i do not.....

jetcatts have been so reliable that I don't normally get up with it....

Matt,

I talked with Bob on my issues and determined it could be a pump or "sucked air" or possibllt an RPM sensor type failure. He told me the last 8 seconds of data gets kinda screwy if you scroll up and down/left and right repeatedly. I fired up the turbine the other day pushed the rpms up to about 85k sitting on the ground. Basically I wanted to see if it would fail again around the same level of fuel or just fail periode. While running at 85k I was periodically shaking the plane around trying to induce a failure. I was not able to produce a "fuel failure" but what I did notice on two or three occasions was that the rpm's would drop down to about 75k. I thought it was based on me shaking the model but also noticed it doing it without me shaking the model. When the rpms would decrease you would notice the PV jump up around .3 or .4 volts to get the rpm back to 85K.. then it would over shoot it and drop the pump voltage back down. This kinda goes along with what I was telling bob that since day 1 on the turbine I noticed the rpm would surge a bit on the ground after a flight. Not so much on startup/learn low only when I returned from a flight. I never second guessed the symptom because it dsplayed this behavior from day 1. Sorry to be so long winded just wanted to get your thoughts on this and see what you thought about the following.

1. If I manually run the pump at a set voltage (fuel line disconnected from turbine) for 3-6 min, do you think that might help determine if it is a bad pump? (pump surge/ bad brushes/ etc etc)
2. Kinda hard to determine if it is sucking air while turbing is running. Do you have any tips/ideas on how to find something of this nature if it is sucking air (avonds F-15)
3. watching the rpms on GSU I am not seeing any fluctuation (sp) except described as above. Don't know if that could be a bad RPM sensor. Any thoughts on determining a bad RPM sensor. When I manually spin the turbine it spins up to about 7-8k starter alone. As it is rising I am not seeing any "jumping" of rpm either. doubtful of rpm sensor but want to hear what you think.

Thanks Matt
Sean

Possibly, but if I were you I would beg/borrow/steal another known good pump and see if you get the same problem. I think it will be tough to isolate this from an air problem.


At the relatively low power, it is less likely that you are sucking air through a connection, but I would look close on the suction side of the pump through to the suction outlet of the UAT, and make sure the outlet of the UAT does not take a sharp bend near the UAT nipple. I have seen leaks develop these over time.


Again, hard to troubleshoot. You might want to try another data cable to see if the plug is OK, all of the supplied cables can be interchanged.

Good luck, let me know how it goes.

Regards,