Fuel

[Tommy Mc]

I should have said, The Executive Summary starts on page 161

[Warmi]

2 hours ago, Tommy Mc said:

Final_Report_EASA.2008-6-light-2.pdf 7.73 MB · 5 downloads

Hi Guys there is a whole heap of reading in this document if you have the time.  From my reading of it Ethanol is of no use in Aviation it is in fact dangerous as the percentage climbs.  You are not suppose to use it when Temps are higher than 23 degrees C due to Vapor locking or above 6000 feet.  You cannot use standard Icing charts as it can create Carb icing at 10 degrees C higher than the chart indicates for Avgas.  I'm pretty sure the British LAA (Light Aircraft Association) have not approved it for use at 10% yet.   You can not leave it in your Tanks for long periods it will draw in water as it is hydroscopic and it will phase separate given time.  Here we have found that "Milky" substance in the Carb Bowl after a week or so.  If/when the bowl starts to corrode it does not stop even with a change of Fuel type.  There are Aircraft here with leaking wings due to the Alcohol in the Fuel breaking down the Resin....... good new is my Wings are OK still after a long period of mogas use .......  there is so much more in this report...Final_Report_EASA.2008-6-light-2.pdf

Approx two months ago prices were as follows here in Ireland

Mogas  €1.55/ltr  

Avgas  €4/ltr

UL91  €3.50  (I have to import myself as it is not available in Ireland)

UL91 represents quite a hike in cost over mogas but I can't unread this report.

Whoa ...$13 per gallon for UL91 if I converting it right .. with these sorts of prices, I would be seriously thinking about starting a revolution ...

 

[Tommy Mc]

I think I got closer to $14    That's old prices now anyway........

 

Mogas now €1.75 at the Pump not sure about the rest but they usually go up accordingly , dreading my next order of Fuel.  €0.20/ltr increase in 8 weeks and there is no sign of it slowing down.....

 

Guns are Illegal here.

[FlyingMonkey]

14 hours ago, Tommy Mc said:

Final_Report_EASA.2008-6-light-2.pdf 7.73 MB · 5 downloads

Hi Guys there is a whole heap of reading in this document if you have the time.  From my reading of it Ethanol is of no use in Aviation it is in fact dangerous as the percentage climbs.  You are not suppose to use it when Temps are higher than 23 degrees C due to Vapor locking or above 6000 feet.  You cannot use standard Icing charts as it can create Carb icing at 10 degrees C higher than the chart indicates for Avgas.  I'm pretty sure the British LAA (Light Aircraft Association) have not approved it for use at 10% yet.   You can not leave it in your Tanks for long periods it will draw in water as it is hydroscopic and it will phase separate given time.  Here we have found that "Milky" substance in the Carb Bowl after a week or so.  If/when the bowl starts to corrode it does not stop even with a change of Fuel type.  There are Aircraft here with leaking wings due to the Alcohol in the Fuel breaking down the Resin....... good new is my Wings are OK still after a long period of mogas use .......  there is so much more in this report...Final_Report_EASA.2008-6-light-2.pdf

Approx two months ago prices were as follows here in Ireland

Mogas  €1.55/ltr  

Avgas  €4/ltr

UL91  €3.50  (I have to import myself as it is not available in Ireland)

UL91 represents quite a hike in cost over mogas but I can't unread this report.

Well...

I think there are a lot of variables at play.  The design of the fuel system, materials involved, operating climate & temperatures, etc.

Yes, generally ethanol is fuels can be problematic, and are not ideal.  In the case of the CT series of airplanes, there is an excellent operational history of using ethylated fuel.  The CT fuel system is designed to accommodate ethanol in the fuel, and the Rotax engine is approved for use with up to 10% ethanol.  As far as I know there has not been a case of an engine stoppage in a CT related to ethylated fuel, either from vapor lock, seal degradation, or other issues.

As I mentioned earlier, I run 93 octane ethylated fuel that *appears* to have an ethanol percentage around 4-5%.  With this fuel I have had zero issues flying all around the Southeastern US, which is an area of high humidity.  I fly from 1000ft MSL to 10,000ft MSL and have never had a single hiccup.  Here is one of my carb bowls, immediately after coming off the engine:

As you can see, it's completely clear, not milky and with no debris or bowl corrosion from water.

In my area, there are three fuels available to me, and all have drawbacks:

1) 93 octane ethylated MOGAS  --  has the noted issues related to ethanol.

2) 100LL  --  Increased maintenance issues related to lead build up in gearbox, on valves, and in exhaust.

3) 90 octane ethanol free  --  insufficient octane for the Rotax 9-series, requiring mixing with another fuel (100LL) to be usable.

 

Based on my experience, having used all of the above, the 93 octane ethylated pump gas is the least of all evils.  Option 3 is okay, but you still have the problems of lead, combined with the hassle of mixing fuels.  I have been using the pump gas 90% of the time (I obviously use 100LL when traveling because that's what's available) without problems.  Is the ethanol an ideal solution?  Of course not.  But *in my area* the fuel seems to contain pretty low ethanol content and runs very will in my CT.  Fuel in other areas or with different mixtures may be more prone to trouble. 

Technical reports are useful and interesting, but might not capture all circumstances or fueling conditions.  I'd certainly pay attention to them, but not necessarily view them as gospel.  Here in the USA, the NTSB investigates accidents, and the FAA regulates aviation.  It's often the case that the NTSB reviews an accident and issues sweeping recommendations...which the FAA then promptly disregards or chooses not to implement.  The NTSB is *only* concerned with safety, while the FAA has to take the totality of aviation under consideration.  Yes, replacing a part may remove the possibility of a failure in an airplane, but if the part only fails under a 6g load on an airplane rated for 4g, and replacing the part costs many thousands of dollars, is it worth it?

My only point in the above paragraph is that you have to balance fuel availability and cost with the possibility of fuel-related failures.  In my case I find the risk profile of locally-available ethylated fuel to be acceptable, but others obviously can make their own risk assessment. 

[Warmi]

The plane I fly (Sting S4) used to be approved for using ethanol based fuel but due to 2 or 3 planes( literally out of 600+ sold planes ) having issues with fuel tank delamination , we no longer can use such fuel.

Again, this had nothing to do with vapor lock or in general any engine issues but rather with delamination (most likely due to manufacturing defects rather than anything else since hundreds of other planes were just fine ) so as far as I know ethanol fuel is just fine for Rotax as long as other parts of the system can handle it.

[FlyingMonkey]

1 hour ago, Warmi said:

The plane I fly (Sting S4) used to be approved for using ethanol based fuel but due to 2 or 3 planes( literally out of 600+ sold planes ) having issues with fuel tank delamination , we no longer can use such fuel.

Again, this had nothing to do with vapor lock or in general any engine issues but rather with delamination (most likely due to manufacturing defects rather than anything else since hundreds of other planes were just fine ) so as far as I know ethanol fuel is just fine for Rotax as long as other parts of the system can handle it.

The engine is fine for 10% ethanol according to Rotax, but it's the other elements of the fuel system that have to be up to snuff.  There have been a couple of CT with leaky fuel tanks.  Not sure if it was caused by ethanol or just bad tank sealing.  Seems like if you have any gaps in sealing the tanks against ethanol you are going to have leaks.

[Mike Koerner]

Tommy,

Thanks for sharing this EASA report. It is well written and interesting.

That said, it’s from 13 years ago. In the US we had just recently started using E10 (gasoline blended with 10% ethanol). It seems to me that this report reflects potential issues and concerns with the use of E10, not actual problems.

Notice, for example, Rotax participated in the FMEA (Failure modes and Effects Analysis, which is essentially brainstorming potential problems and rating their risk based on estimated severity, probability, and detectability. This was used to define areas of concern for the subsequent study.) And yet, Rotax later approved the use of E10 in their engines (and so has Flight Design approved E10 for use in their aircraft). So clearly, subsequent to this FMEA, they collected sufficient data to convince themselves that E10 is not a problem, at least not for the CT aircraft and Rotax engines.

I’m sure I’m guilty of creeping normality (where we decide it’s OK to launch because it’s only a little colder than the coldest temperature the solid propellant boosters have ever operated at before, or we decide that ice falling from the external tank, which has damaged the shuttle’s thermal tiles on every previous flight, probably won’t cause catastrophic damage this time either). Yet, in 2000 hours and 15 years of flying my CT2k, mostly on E10, I have not had (or at least have not detected) any of these problems. And of course, the other members of this forum represent a much greater level of experience with E10.

With respect to phase separation (conclusions on page 74), I’ve left my plane out for up to a week in torrential rain; and I’ve run my tanks from full, down to a couple gallons on each side, during a single flight (which EASA thought might be a problem), without experiencing this. I don’t recall anyone on this forum having a problem with phase separation either, though some concerns are mentioned above. The US Environmental Protection Agency (yes, I recognize they are not responsible for flight safety) has said phase separation won’t happen with E10 over the course of a "winter storage season" (I don’t know what the storage conditions were).

With respect to icing (conclusions on page 79), from the jungles south of Mexico City to the Artic Circle, from Catalina Island to the Bahamas; in rain and in snow: I haven’t experienced this. And again, others on this forum have flown in a wider range of conditions. And yet, only a couple have ever mentioned what they thought was carburetor ice, despite that fact that many of us are using E10 and (improperly) never use our inlet air preheater (carb heat) at all.

With respect to vapor lock (conclusions on page 93), though I’ve never let any of my engine temperatures get near critical levels, others on this forum have, and again, I recall only one or two mentions of possible vapor lock.

With respect to material compatibility (conclusions on page 125), there was a problem with our original plastic fuel filters. A service bulletin was issued to replace them, and new metal filters were distributed free of charge. If I remember correctly, my plastic one was substantially deformed at the time of removal, but not yet leaking. With respect to elastomers, I know of at least one owner (whose name I shall not mention) who let his rubber parts go well beyond the manufacture’s recommended 5-year replacement interval, with no fuel compatibility issues evident. And the wing’s thermoset resin is (at least mostly) protected from the fuel by a special coating applied to the inside of the fuel tanks.

The EASA document also includes a discussion of water detection (conclusions on page 135), but absent a problem, I don’t see the need for detection.

And finally, there is an analysis of whether adding alcohol to fuel is going to save the world or not (conclusions on page 143). That would be a subject for a different forum.

Despite the title, the “Executive Summary” on page 161 is actually just a tabulation of FMEA, which they did not include in total because, they say, it’s in German. At 36 pages, this appendix was the source information they used for the FMEA section of the main report, which covers 10 pages (51 – 61) and has its own conclusion (page 61).

So, I don’t know… but I’m going to continue using E10.

[Anticept]

Piggybacking: Here's my experiences, dealing with a flight line of 4 CTLS and a collective 10,000 hours between them:

Never seen ice.

I've had phase separation once in wings with low fuel, and multiple times in carbs. Ohio's temperatures swing wildly for about 6 months out of the year, and we're a very wet state when that happens. We call it mud season instead of spring for example! Our winters are also cold, but also hot and wet. Can see huge swings in temperature in a day, multiple times in a week.

Carb icing: only one time do we suspect it was carb icing, it was during taxi back after a flight in almost freezing, wet conditions.

Vapor lock: Not possible in a high wing aircraft with a functioning fuel system and a low engine (aka, doesn't apply to wing mounted or above mounted engines!). Vapor lock is caused by drawing fuel vertically instead of pumping it, dropping pressure and allowing it to start vaporizing. Flight designs always have head pressure due to the high wing design. I CAN, however, attest to frequent vapor issues (not locks). It loves to make my damn fuel pressure go wild, and it happens in FIVE carb CTs that I know here. Adding 20% avgas stops the issue entirely, which I'll do if I have a nervous passenger.

[procharger]

Never seen a drop of water in mine 6 years now running 93 pump gas.

Real humid here in Va.

[procharger]

Fuel at KSFQ in Suffolk Va.  93 mogas $4.39 keeps going up.

[Anticept]

Some more interesting reading:

https://southeastpetro.com/wp-content/uploads/2015/08/Veeder-Root-Ethanol-Water-Phase-Separation-Facts.pdf

Of interest: partial phase separation can occur at very low percentages, far below 0.5% depending on conditions, though agitating the fuel can cause re-absorption.

Of particular *warning*: Phase  separation  contains  a  lot  of  ethanol,  some  water,  and  a  small  amount  of  gasoline. [...]  This  mixture  is  highly
corrosive compared to pure water or E10 gasoline.

This is also mentioned in Flight Design Service Bulletin SN-ASTM-CTLS-01-en https://flightdesign.com/wp-content/uploads/2020/09/SN-ASTM-CTLS-01-en.pdf .

[FlyingMonkey]

On 10/30/2021 at 9:57 AM, procharger said:

Fuel at KSFQ in Suffolk Va.  93 mogas $4.39 keeps going up.

Cost of fuel is a definite issue for all of us at the moment, sadly.  Right at $4/gal here in Georgia, which is very high for this area.  100LL seems to swing more slowly in this area, so the delta between 100LL and 93 pump gas narrows, at least temporarily, when fuel gets expensive.  Self serve 100LL is $5.09 currently at my home drome.

[207WF]

Not worried about water, but I made the mistake of leaving e10 in the tank unflown for too long one time, and the alcohol starting eating my fuel tank sealant.

Caught it in time and switched to 100LL only.

WF

[Roger Lee]

E10 should not have bothered your kreem Weiss tank coating. The coating should be impervious to the fuel and ethanol.You may have had some flaking or degeneration, but the coating should not have been affected by E10 or most of us would have issues. Some leave it in all winter long. In parts of Europe and they use 17% - 18% ethanol and in South America up to 23%. You may have had a leak like lots of others, but I don't see it from E10.

[207WF]

well, after going back to 100LL the wing has remained stable.  

Maybe I have just been lucky!

WF