Why can't we use Ethanol

[blue eagle]

Dear Mooniacs,

Would it not be nice to sit in the cockpit and flying on bio Ethanol knowing that only carbon dioxide and water is leaving the exhaust. Also that your Lycoming or Continental engine is running cooler, giving more horses and never ever fouling your spark plugs again. Your engine is running with a full synthetic engine oil making it last longer and you are able to fly for many years with your same current engine.

 

Let's go over some topics:

 

- Octane number of ethanol is higher than that of 100LL making it a perfect replacement.

 

- Energy density is slightly lower compared with Avgas, so the mixture needs to adjusted to a higher value. This can be doen exact the same way as we do it today by leaning and using the EGT as parameter. Our Lycoming and Continental engines are a perfectly designed for this.

 

- Ethanol can be solved in water, so it is not (easy) to detect if there is water in your fuel. I hear you saying that is a risk and therefor don't use Ethanol as a aviation fuel. I disagree, let me explain : If water is soluble  in Ethanol it makes a homogeneous mixture. So If I would use it I would always have the same fuel and no pockets of water that could kill my engine if I switch tanks. When I perform a run up prior to releasing the brakes, I actually execute a performance test. With pitch fully fine and throttle fully forward I know what MAP and RPM I have to expect. If these values are off I would abort the take off and go check what is wrong. Now if I  would take of with ethanol after a good performance check I know that I will get the same power because the fuel is exactly the same. With Avgas this is a different story, I know I have now good fuel and power but if there is a pocket of water because I failed to drain all the fuel point in my pre-check, I could loose my engine. The Question is what is safer?

There are some other things you should know, tests have revealed that there needs to be a considerable amount of water to have a noticeable drop in power. We are talking more than 20 percent water content. Water content can be determined by measuring the specific gravity (talking a sample of 1 pint and weighing it precisely (like battery acid). This could be performed every morning by the Supplier as some kind of batch release that day. There are solutions to control this risk, but then the ethanol would be safer on the risks caused by water.

 

- Pure Ethanol burns with less visible flames compared to Avgas (because it is cleaner). Top Fuel racers know this problem and act accordingly. With some additives the flames could be made visible if that is what some would like.

 

- Compatibility with materials is different between Avgas and Ethanol. Ethanol can cause swelling of some hydrocarbon materials. I did some internet study on the materials in my 1998 Mooney M20J turbo-normalized (M20-turbos) with following interesting results:

 

  

 

 

 

[MARZ]

Don't know for sure but judging from what it does to aluminum carbs in my motorcycle and little used generator I'd say it has higher corrosive properties - additionally a quick web search shows this -

 

Quoting from a position paper from the National Marine Manufacturers Association (NMMA)

 

Aluminum Fuel Tanks

 

In the case of aluminum tanks, aluminum is a highly conductive metal that relies on an oxide layer for its corrosion protection properties. Low levels of ethanol, such as E10 (10%), are usually not a problem in aluminum tanks because the oxide layer provides a good measure of protection. The problem occurs when the ethanol content is increased.

 

There are two mechanisms that occur with ethanol. Both mechanisms are a result of the hydroscopic property of ethanol, meaning it absorbs water. The more ethanol in the fuel, the more water there will be in the fuel tank. Water not only causes the tank to corrode, it also causes the corrosion particles to clog fuel filters, fuel systems, and damage engine components. The corrosion rate can be accelerated under a number of conditions if other contaminating metals are present such as copper which may be picked up from brass fittings or as a low level contaminant in the aluminum alloy. Chloride, which is a chemical found in salt water, will also accelerate corrosion. In the long term, corrosion can perforate the aluminum to produce leaks that would cause fuel to spill into the bilge and end up in the environment. In the worse case it could cause a fire and/or explosion hazard. Boat fuel tanks are often located under the deck next to the engine where the operator might not be aware of a leak until it was too late.           .  

 

The second mechanism that can occurs with the increased use of ethanol based fuel in aluminum tanks is galvanic corrosion.  Gasoline fuel is not conductive, but the presence of ethanol or ethanol and water will conduct electricity. The galvanic process that occurs to aluminum trim tabs, stern drives, shaft couplings, etc. will occur within the aluminum fuel tank. Boat builders are able to protect exterior aluminum boat equipment with sacrificial anodes known as zincs. Sacrificial anodes are not a feasible option for the interior of a fuel tank.

 

 

 

[N201MKTurbo]

Dear Mooniacs,

 

- Energy density is slightly lower compared with Avgas, so the mixture needs to adjusted to a higher value. This can be doen exact the same way as we do it today by leaning and using the EGT as parameter. Our Lycoming and Continental engines are a perfectly designed for this.

 

The energy density of ethanol is way lower then avgas. Your range would be cut by a third.

Avgas 44 MJ/kg 31.59 MJ/L

Ethanol 30 MJ/kg 24MJ/l

[N201MKTurbo]

I remember back in the eighties there was an SF260 flying around the pancake breakfast and airshow circuit touting the joys of ethanol. I wonder what happened to him?

[blue eagle]

You are right for the same amount of energy you will need 31.6 % more ethanol if measured volumetric.

Your number of Avgas is not correct it should be 31.59.  Having only a range of 68.5% besides replacing some o-rings and seals it would be still interesting because  80% of my trips are shorter than 60 % of the maximum range of my aircraft. If I really require a longer range then i would have the option of selecting another fuel without having any problem, or planning an extra stop which is often preferred by passengers. 

 

There is a team called vanguard squadron and they fly many years on pure ethanol, and proving that it is possible. I have no relation with them but come to the same conclusion after thinking about it. They managed solve all  issues and replaced the Lycoming engine  fuel pump by an ethanol approved electric fuel pump.

 

Regards,

 

BA

[KSMooniac]

It is a very high-cost alternative, and nobody in the fleet will spend the money to certify and replace all of the necessary components in every airframe, and especially not the tank sealant in our Mooneys!  If it cost $1.00 a gallon, then perhaps there would be a sufficient financial incentive to do so, but not at $8 a gallon!  No way.

 

There is a drop-in solution today called G100UL that is operationally transparent to the owner/pilot, and it very well should end up costing us less than 100LL as well.  The FAA is the biggest obstacle since they don't want to actually solve any problems any more...just study them endlessly so they can stay busy.

[carusoam]

No.

Good morning Blue Eagle. Feel free to introduce yourself or risk receiving some less than stellar replies.

Your statements, offered as fact, are lacking.

Alcohol is an inferior fuel for our planes.

Good luck either educating people on how it could work or getting educated yourself.

Best regards,

-a-