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  #71  
Old 01-18-2018, 04:54 PM
TS Flightlines TS Flightlines is offline
 
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Location: Ridgeland, SC
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Julian----I was told the pump was clean, with no traces, so I was concentrated on the discharge hose. Did find that anomaly with the liner, that isnt present anywhere else. Did section a piece out of the -6 supply hose and the anomaly isnt there. Clean as a whistle, as you would expect a teflon hose running fuel through it would be.

Agreed---inspection is a good course of action, and even flushing the hoses. But if there wasnt any debris in the gascolator, or the supply hose, then it got there some how, and the size of the debris is much larger than would have passed through the gascolator screen.

Tom
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Tom Swearengen, TS Flightlines LLC
Teflon Hose Assemblies for Experimentals
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RV7 Tail Kit Completed, Fuse started-Pay as I go Plan
Ridgeland, SC
www.tsflightlines.com
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  #72  
Old 01-18-2018, 06:21 PM
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Phantom30 Phantom30 is offline
 
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Quote:
Originally Posted by Azjulian View Post
What I should point out is that all the debris on Rics plane was in the adapter on the outlet side of the fuel pump. I had run the fuel flow test in the Vans manual (which is at the gascoloator) and then because of the issues Ric and Mark were experiencing ran it again at points up the fuel system, seeing a noticeable degradation in fuel flow after the pump. How the debris got there and got compacted in the adapter I have no clue (when they took the pump apart it looked brand new).

So I would suggest that on condition inspect people remove the adapters and inspect.

I don't have the TS flightlines on my plane, but it looks from the instructions that the adapters are replaced by that solution.
Azjulian....the material did not come through the pump. It was moving around in the fuel line between the banjo fitting that attaches to the fuel block assy and the outlet fitting of the fuel pump. The material being debris from the Teflon hose liner left there following manufacture of the hose. And it had been previously flow tested with okay results. Did I look down the bore of the hose...no; I guess my mistake. As it was part if the equipment received from Rotax I assumed it was okay.
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  #73  
Old 01-18-2018, 07:05 PM
RFSchaller RFSchaller is offline
 
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Wherever it came from itís scary. I blew out out my fuel lines with air and a flush cloth over then end when I installed them. I never got anything on the cloth. That amount of debris is just bizarre!
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  #74  
Old 01-18-2018, 07:25 PM
TS Flightlines TS Flightlines is offline
 
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Rich, it IS bizarre.

Tom
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Teflon Hose Assemblies for Experimentals
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RV7 Tail Kit Completed, Fuse started-Pay as I go Plan
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  #75  
Old 02-16-2018, 11:45 PM
cyamaha2007 cyamaha2007 is offline
 
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Location: Wright City, MO
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TS FLIGHTLINES keep up the good work! Thanks for dedicating time and money to figuring out our problem. We also have a low fuel pressure readings from time to time. I've ruled out the sending unit but that's as far as I've made it. Our problem is hit or miss as of now making it hard to duplicate.
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  #76  
Old 02-17-2018, 08:38 AM
TS Flightlines TS Flightlines is offline
 
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Chuck---thats one of the strange things about this whole deal. Some Rotax 912's have it, some dont. It doesnt seem to be geographical, altitude, RPM, fuel blend, or any other obviously related items. Some with the old rubber hoses were fine, some werent. Some with the Rotax version teflon were fine, others werent. WE did take Scott's advice and ask for testers that were having pressure issues to contact us, AND several have. Interesting results.
We are still gathering data--because all of you want to know. We're down to the last 5 testers that are helping us (Aircraft Specialty and TS FLightlines) gather this data. Weather, schedules, and gee sometimes life happens that throws a kink in plans, so its taken longer than we wanted, but its been methodical.
Oh and this isnt just US based planes, we have an Australian based 12 that is also involved, as well as a European owner.

Tom
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Teflon Hose Assemblies for Experimentals
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RV7 Tail Kit Completed, Fuse started-Pay as I go Plan
Ridgeland, SC
www.tsflightlines.com
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  #77  
Old 03-03-2018, 08:37 PM
Aircraft Specialty Aircraft Specialty is offline
 
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In response to requests from many RV-12 owners to publish more data regarding what we have uncovered throughout our multiple fuel system dissections, we are releasing a follow up report to our original report issued in January.

This one is much more detailed with pictures of what we have found.

http://www.aircraftspecialty.com/PDF... Pressure2.pdf

As always, Tom and I want to thank ALL of you for the help we have received throughout this process.

Have a great weekend, and happy flying/building

Steve and Tom
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  #78  
Old 03-04-2018, 12:32 AM
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Piper J3 Piper J3 is offline
 
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Did you do a fuel flow analysis with 0.021 Vs. 0.014 restrictive orifice at the low ~ 5 psig fuel pump delivery pressure? At such a low pressure the flow difference may be significant.

Vans may specify a larger orifice for more return fuel flow to the tank for a specific reason and that might be to prevent vapor lock on engines that are heat-soaked. The 912 installation in the RV-12 is tightly cowled with minimal air flow during ground operations. Perhaps Vans wanted additional cool fuel flow to prevent fuel from vaporing in the carburetor float bowls.

I suspect a higher fuel flow back to the tank would be beneficial when re-starting a hot engine that has sat for some period of time where the fuel in the carb bowls, if not beginning to vaporize, would surely be heated above ambient temp. Having an abundance of cool fuel in the fuel delivery rail located on the top side of the hot engine sounds like a good idea.
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  #79  
Old 03-04-2018, 02:31 AM
Aircraft Specialty Aircraft Specialty is offline
 
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Quote:
Originally Posted by Piper J3 View Post
Did you do a fuel flow analysis with 0.021 Vs. 0.014 restrictive orifice at the low ~ 5 psig fuel pump delivery pressure? At such a low pressure the flow difference may be significant.

Vans may specify a larger orifice for more return fuel flow to the tank for a specific reason and that might be to prevent vapor lock on engines that are heat-soaked. The 912 installation in the RV-12 is tightly cowled with minimal air flow during ground operations. Perhaps Vans wanted additional cool fuel flow to prevent fuel from vaporing in the carburetor float bowls.

I suspect a higher fuel flow back to the tank would be beneficial when re-starting a hot engine that has sat for some period of time where the fuel in the carb bowls, if not beginning to vaporize, would surely be heated above ambient temp. Having an abundance of cool fuel in the fuel delivery rail located on the top side of the hot engine sounds like a good idea.
Jim,

In short.... yes. We know what the fuel flow differences are. If we wanted to utilize a larger return orifice it would be very easy to swap out the restrictor for a larger diameter one.

However, our system utilizes the size specified in the Rotax manual. (within .001”) Our system is NOT the one having fuel pressure issues and is not having ANY issues with the starting of a hot engine. So, there is no reason for us to go against what the manual specifies.

Personally, I think that there are much more intriguing elements to this document than the restrictor orifice size.

Steve

P.S. As Tom mentions below, and has been documented previously......the Stock OEM Rotax fitting is sized differently than what they specify in their own manual. A #75 drill bit would easily enlarge our orifice out to the actual size of the Rotax OE fittings. However, doing so would enlarge the orifice size beyond what Rotax specifies in their manual. Based on real world testing in customer aircraft, it certainly does not appear that there is ANY meaningful difference in operation or performance between the .015 and .021 restrictor sizes.
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Last edited by Aircraft Specialty : 03-04-2018 at 08:45 AM. Reason: P.S.
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  #80  
Old 03-04-2018, 06:43 AM
TS Flightlines TS Flightlines is offline
 
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Jim---the Vans restrictor is a .021 orifice. Its a STOCK Rotax fitting, as compared to a OE Rotax fitting---yes the WHOLE banjo fitting that I purchased from a Rotax parts distributor in Florida---dont know If I can mention the name here---but they are prominent. I also purchased the restrictor separately. Compared ALL of them. They are the same. Vans doesnt specifiy a larger restrictor.
3 different return hoses were checked, and all 3 had the same restrictor. MY conclusion, was that the restrictor size was the same as the OE Rotax----since I also had theirs to compare.

AND--what I really wanted to do was do a test on an ENTIRE fuel system, as installed in a RV12. Yep, tank, boost pump, lines, gascolator, engine, etc. THAT way you have all the components, not just the hoses off the engine. Utilizing just those hoses would mean some creative adapter fittings to connect sensors, and may or may NOT be entirely accurate. Steve and I had discussed contracting with a well known fuel systems manufacturer to utilize their flow bench, but after some of the results we decided that wasnt necessary. BUT, certainly if someone wants to donate their plane for that its would be great. Dont know how we'd get the plane into their flow bench room, even with the wings off. Thus the multiple testers in different parts of the country, and several overseas in an unofficial capacity.

Tom
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Tom Swearengen, TS Flightlines LLC
Teflon Hose Assemblies for Experimentals
Proud Vendor for RV1, Donator to VAF
RV7 Tail Kit Completed, Fuse started-Pay as I go Plan
Ridgeland, SC
www.tsflightlines.com

Last edited by TS Flightlines : 03-04-2018 at 07:05 AM.
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