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Roger Lee
Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.
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 Posted: Sat Apr 21, 2012 8:35 pm Post subject: Fuel filters |
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The issue with some filters is that the ethanol will make them swell and reduce flow. Make sure you use a good quality filter meant to handle any fuel you may use. Some filter elements will break down after long exposure to ethanol. Ethanol will cause many plastic filters to become soft. It is advisable to use a metal filter with a metal mesh screen. Then there is never a worry. There is no need to have a clear filter so you can see through it because you should be checking the filter every 100 hours or each annual.
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Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Sun Apr 22, 2012 6:54 am Post subject: Fuel filters |
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Where are you guys getting your fuel filters from?
If they are automotive, read the packaging, does it state acceptable for ethanol?
If they are aviation, does it state acceptable for ethanol?
If they are automotive CAN one ASSume the manufacture has run test to make sure they are acceptable for MoGas?
If you do not have PROOF then run your own test for a couple of MONTHS - By having the fuel filter filled and sitting in MoGas AND by exchanging (flowing) (replacing) the gas every week.
FLOW RATE - I know you guys are EXPERIMENTAL - But did you know there is an FAA requirement AC43.13 that states that in a gravity system the free flow rate of a system should be 8 times the fuel requirement of an engine at cruse. So, lets say you burn 2.5 GPH the free flow rate should be: 2.5 x 8 = 20 GPH. That means the DIAMETER of your fuel lines, the SIZE of your FUEL FILTER and the restrictions of your fittings should allow 20 GPH. That is NOT MUCH. Does your system comply? Can you say Fuel Starvation, can you say Vapor Lock?
I am very much in favor of CLEAR 'plastic' fuel filters. And I would, if your fuel system takes the fuel flow through the cabin - I would like to see them placed where you can SEE them during flight if at all possible.
Metal fuel filters work just fine. But, Roger, 100 hours or not, how are you going to inspect them? You can't - You sure can replace them. You can back flush them - - BUT! You still do not know how clean you got them, even after back flushing them. IF you want to reuse a filter (Metal or Plastic) you could always set up an apparatus and TIME the flow rate for a NEW filter and re-time it after back flushing it. That way you will have real data to verify a safe fuel system. Otherwise replace filter or play Russian Roulette.
Barry
On Sun, Apr 22, 2012 at 12:35 AM, Roger Lee <ssadiver1(at)yahoo.com (ssadiver1(at)yahoo.com)> wrote:
[quote]--> RotaxEngines-List message posted by: "Roger Lee" <ssadiver1(at)yahoo.com (ssadiver1(at)yahoo.com)>
The issue with some filters is that the ethanol will make them swell and reduce flow. Make sure you use a good quality filter meant to handle any fuel you may use. Some filter elements will break down after long exposure to ethanol. Ethanol will cause many plastic filters to become soft. It is advisable to use a metal filter with a metal mesh screen. Then there is never a worry. There is no need to have a clear filter so you can see through it because you should be checking the filter every 100 hours or each annual.
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Roger Lee
Tucson, Az.
Light Sport Repairman - Maintenance Rated
Rotax Repair Center - Heavy Maint. Rated
Home [url=tel:520-574-1080]520-574-1080[/url] TRY HOME FIRST
Cell [url=tel:520-349-7056]520-349-7056[/url]
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Thom Riddle
Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)
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| Posted: Mon Apr 23, 2012 3:55 am Post subject: Re: Fuel filters |
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Barry,
43.13 concerns maintenance, repair and inspection of type certificated aircraft.
The FAR that covers fuel flow requirements for type certificated aircraft is 23.955, excerpts of which follows:
§ 23.955 Fuel flow.
(b) Gravity systems. The fuel flow rate for gravity systems (main and reserve supply) must be 150 percent of the takeoff fuel consumption of the engine.
Notice that the gravity feed system flow requirement is only 50% greater than max fuel flow demand at take-off power.
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Thom Riddle
Buffalo, NY (9G0)
Don't worry about old age... it doesn't last very long.
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BARRY CHECK 6
Joined: 15 Mar 2011
Posts: 738
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| Posted: Mon Apr 23, 2012 1:09 pm Post subject: Fuel filters |
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Tom:
AC43.13 a/b are " Acceptable Methods, Techniques, and Practices - Aircraft Inspection and Repair". It does go one step further in that it says AC Large... As in Aircraft Large. BUT, as any builder will attest to - Try to get a experimental aircraft approved by a DAR (at least any DAR worth his weight in dirt) without referencing AC 43.13. But, I took your lead and searched and searched for the number '8' times I mentioned but could not find it. I remember that number from a Build Clinic I went to at Sun'nFun. I did go to the FAR 23.955. It does state 150% of Full Power (Take Off) fuel flow for a gravity feed system. But, maybe the difference comes from the statement that it is 8 times the 'Cruse' fuel flow. I can see where that would create a area of great question. Example: If we both have the same engine and I cruse at 85% power and you cruse at 55% power - 8 times 55% is a lot less than 8 times 85%. So the fuel flow rates would be different... Maybe that is where 8 comes in??? I will commit that 150% at Full Throttle to memory. BUT! Remember that is MINIMUM NUMBER for acceptance. And here is another area where the FAA messed up... They did not state at What Density Altitude.
Fuel consumption at Colorado Springs, Co (~5280 Ft) would be a lot less that at Ocean City, NJ (~10 Ft). So if you were to install a small diameter fuel line and be happy at 150% flow in Colorado you could be running Lean at New Jersey.
Maybe that is also where the speaker at Sun'n Fun came up with the number 8 from.
Barry
Experience is what you get from failures.
- Barry
On Mon, Apr 23, 2012 at 7:55 AM, Thom Riddle <riddletr(at)gmail.com (riddletr(at)gmail.com)> wrote:
[quote]--> RotaxEngines-List message posted by: "Thom Riddle" <riddletr(at)gmail.com (riddletr(at)gmail.com)>
Barry,
43.13 concerns maintenance, repair and inspection of type certificated aircraft.
The FAR that covers fuel flow requirements for type certificated aircraft is 23.955, excerpts of which follows:
§ 23.955 Fuel flow.
(b) Gravity systems. The fuel flow rate for gravity systems (main and reserve supply) must be 150 percent of the takeoff fuel consumption of the engine.
Notice that the gravity feed system flow requirement is only 50% greater than max fuel flow demand at take-off power.
--------
Thom Riddle
Buffalo, NY (9G0)
Kolb Slingshot SS-021
Jabiru 2200A #1574
Tennessee Prop 64x32
Truth is what stands the test of experience.
- Albert Einstein
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