Princeton fuel probe

[kevinh]

Proseal is the same stuff, just a different brand.

Peter

Thanks! Ah yes, I did the proseal dance with my RV. I have yet to install my tank and I was planning on using oops fittings. In your opinion if you had a virgin tank would you do oops or proseal to ensure no leak development? -kevin

[9GT]

Not to be overly critical, but the teflon tape you have used on the fuel selector valve is a never, ever, ever, use item on any fuel lines or fittings. There are so many NTSB reports fatal accidents caused by fuel starvation as a result of using this its not funny.

I get your point but like all sealants, if you only put the tape on the thread and don't have it overlapping the internal end of the fitting it's not going to get into the system. I have never found any traces of it in my fuel filter or gascolator.
Proseal is the same stuff, just a different brand.

Peter

Here is a result of a quick search on the NTSB site for aviation related accidents due to fuel starvation as a result of using teflon tape for sealing fuel supply fittings. http://www.asias.faa.gov/pls/apex/f?p=100:27:0::NO:27:: I am sure most people on this list also thought it was a good idea to use it and that they knew how to use it to avoid problems. It IS NOT an acceptable method for sealing fuel supply line fittings and does not in any way meet any form of standard aviation practice. Here is a link to FAA AC 43:13-1B , FAA Acceptable Methods, Techniques, And Practices-Aircraft Inspection And Repair : http://www.faa.gov/regulations_policies ... ntid/99861 It's a free download or you can order a hard copy from the FAA for a nominal fee. Every home builder should become familiar with it. There is a reason to follow these standard acceptable practices,,,,that's safety. Chapter 8, page 22, 8-38 f. specifically states not to use teflon tape as a fuel fitting sealant. You can take it for what its worth and choose to ignore the standard recommended practices, but doing so shows poor quality workmanship and a cavalier attitude towards safety.

[peter anson]

I think you've won the argument there David. I wasn't aware of all the evidence. I think feel kind of chastised. Incidentally,did you know that the Sonex instruction to use cadmium plated AN bolts through the titanium gear legs is a no-no according to Mil-specs?

I would definitely use the oops fittings Kevin. At the time I was fitting the probe, it was obvious that the standard fittings were fragile, but I wasn't aware that so many people had trouble with them. The leak was so slow that it wasn't obvious what was leaking. The next attempt at fixing would have been an oops, but the bog has worked for 3 years so far.

Peter

[kevinh]

thanks - I'll go oopsy.

[sonex892.]

Hi Steve,
No intention of fitting dual auxiliary tanks. For a start it would be impossible to turn the fuel off, but more importantly it would mean changing the label and after you've gone to that much trouble to produce a beautiful label you don't want to do it all again.

I have one of those valves in a box. They are for 3 inlets and 1 outlet so it wont be impossible to turn off. The opposite position from your ON position (180 degrees) will give the OFF position for all 3 inlets. Yes the label however, is a showstopper.

I actually have considered fitting an auxiliary tank and think I would pump in via one of the fittings intended for the sight gauge. I know this is getting off the subject but have you had much use from your Auxiliary tank?
Peter

I pipe the aux fuel directly to the engine via a 3 way valve similar to your existing valve. That way its kind of like an additional trim with no need for extreme c of g changes required like when transferring to the main. I put the aux tank in whenever I leave the local area. Last time I had it in, I did a 3 hour 375 nm non stop flight to Moruya landed with 30 litres on board.

Your fuel leak on the sender is strange. The only problem I had with my Princeton sender was the 1/8" NPT fitting would only engage 1.5 turns into the fitting moulded into the tank. I ran a tap through the original tank fitting to achieve another few turns. I was expecting it to leak but 6 years on, its still good. No oops fittings anywhere on the tank. Yet.
Steve
Sonex 892

[peter anson]

Here is a result of a quick search on the NTSB site for aviation related accidents due to fuel starvation as a result of using teflon tape for sealing fuel supply fittings. http://www.asias.faa.gov/pls/apex/f?p=100:27:0::NO:27:: I am sure most people on this list also thought it was a good idea to use it and that they knew how to use it to avoid problems.

Having already conceded this argument and at the risk of flogging a dead horse, I'd like to take issue with this evidence against the use of teflon tape. I was rather worried about whether I should be pulling parts of my fuel system apart so delved a bit deeper. It turns out that this link that supposedly is to accidents caused by teflon tape in the fuel system is actually just to any report that mentions the word "teflon", sometimes to where the teflon is used for perfectly legitimate purposes such as teflon O rings and seals, and not necessarily the cause of the accident at all. There are 49 reports from a 34 year period including such things as "teflon coated steel cable " on a Cirrus BRS. If the search is for "teflon tape" there are just 9 reports from the period, and of these, just ONE, Report Number SEA86LA198, where teflon tape was the cause of an engine failure. In 1986 a Cessna 188 glider tug had it's engine fail due to a 1" long piece of teflon tape clogging the fuel pump. The tug and it's towed glider both made forced landings with no injuries.
Now it could be that this lack of evidence against teflon tape is simply because it is no longer used much in aviation circles, but to claim that there have been large numbers of accidents and fatalities caused by its use is dishonest.

I'll leave the last word to Dave Prizio in his article on sealants from the May 2016 issue of "Kitplanes".
Before we leave the topic of thread sealants, we need to talk about Teflon tape. My initial thought was to simply say, “Don’t use it on, in, or near an airplane, ever.” The reason for that is that it is so easy to misuse, leaving a tiny strip of tape in a place where it can clog a fuel line or oil line or lodge in a fuel-flow sensor or carburetor. But there are some aviation vendors, Pacific Oil Cooler for one, who routinely use Teflon tape, so it obviously can be used appropriately. The important thing is to never let the tape cover the end or the first two threads of a fitting. The bottom line is, you can use Teflon tape, but there are better choices available to you.

Peter

[Sonex1517]

So getting back on topic.....

I flew an hour today and the fuel gauge read accurately. I am happy this is solved and to me, the Princeton capacitive probe is a good combo with the Belite LED fuel gauge.

If anyone wants to buy the Belite MMS sensor.....I have one for sale.


Robbie Culver
Sonex 1517
Chicagoland
N1517S

[tljones42]

"I flew an hour today and the fuel gauge read accurately. I am happy this is solved and to me, the Princeton capacitive probe is a good combo with the Belite LED fuel gauge.

If anyone wants to buy the Belite MMS sensor.....I have one for sale."

Thanks Robbie for doing the development work on this. If you hear from anyone who wants two sensors let me know.

Tom Jones
Onex 0133
Turbo Aerovee