Ethanol

[howard bradley]

Gents , the CAA have said Ethanol can be used in Microlights but not in Cat A aircraft has anyone any information why this is when the same engine is used and airframe as in a Jabiru UL450 ,the only difference being the flap setting

[Barry Plumb]

Howard, You may well ask, it does not seem at all logical, and it isn't.
You are absolutely correct that there are types of aircraft which are either group A or microlight, with virtually no difference.
The problems of using fuel containing ethanol have been fairly widely discussed in the magazine, but to summarise they are
a) Octane rating. The ethanol is used as an octane boost and if it is lost from the fuel by evaporation in warm weather then a lower octane fuel remains leading to possible detonation (pinking or knocking)in the engine. b) Water solubility. The ethanol will take in water vapour from surroundings and ultimately will separate out in the tank. This can cause engine stoppage in the same way that any other source of water entering the tank would. Also the ethanol is now separated out from the fuel resulting in low octane as in a) above
c) Corrosion of metalic components. Ethanol will attack some metal components in the fuel system, such as aluminium.
d) Chemical compatibility. Here the fuel may be incompatible with materials of construction such as GRP resins, rubber or synthetic rubber seals and hoses etc
e) Vapour pressure. The fuel vapour pressure is increased leading to a higher possibility of vapour locking etc.

Most engine makers confirm that up to 5% ethanol is no problem for their engine. The problem comes about when the base fuel no longer contains 5% ethanol due to the factors in a) and b) above. The reduction of octane rating may be enough to result in detonation and rapid engine damage.

So it may in fact be legal to fly a microlight on mogas containing ethanol, but whether is sensible or not is another matter.

Happy Landings

Barry Plumb

[howard bradley]

Thanks Barry for your input , information regarding Jabiru engines and Ethanol is about to be published ,methods of sloshing out the fuel tank using Kleem are now available , information from Australia , America , and many other countries indicates min problems ,
In Jan this year a topic under the heading Mogas on this forum was answered in the main that the LAA was in discussion with the CAA regarding the problem the question to be answered is what if any agreement has been reached , the difference in price now ref Avgas it is twice the price of Mogas for OAPs this is significant .

[Alan Adams]

I am also confused regarding the inconsistencies with the use of mogas in microlight/Group A aircraft, regardless of ethanol content.

Mogas has a much higher vapour pressure than avgas which is why presumably AN98, AN98A and AN98C put limits on pressure altitude and fuel temperature but these restrictions do not apply to microlight aircraft! I struggle to see the difference between a modern microlight and VLA/LSA particularly when using an engine such as the Rotax 912 which is designed for operation on mogas to the European specification EN 228 that permits up to 5% ethanol.

In Brian’s response to Howard he indicates that one of the problems with ethanol is increased volatility (vapour pressure). Pure ethanol has a very much lower vapour pressure than mogas but when 5% ethanol is blended into mogas the vapour pressure of the blend does indeed increase significantly over the base mogas vapour pressure. Typically, the level of vapour pressure increase would put the blended mogas outside the limits of the current specification for unleaded mogas, EN 228. Consequently, in the UK at least, the base fuel that will be used for blending with ethanol will be manufactured with an adjusted vapour pressure and octane to accommodate the changes that occur when blending to ensure compliance of the final blend. As a result, I would have thought that the fuel we purchase at the pumps will have similar vapour pressure and volatility behaviour to current unleaded 95 and this seems to be borne out by research work done in a number of countries (albeit in relation to motor vehicle applications).

Many of the material compatibility problems that have been experienced occur with pure ethanol but are either less or no issue with blends of E5 or E10 (5% or 10% ethanol blends). For example, aluminium is not recommended for continual contact with pure anhydrous ethanol but it is my understanding that aluminium has been shown to be compatible with E5 and E10. There are some compatibility issues with non metallic components such as seals and hoses but is this likely to be more of a problem for older aircraft systems than for the new breed of Rotax and Jabiru powered aircraft? In any case there should now be a substantial amount of information on compatibility available since E5 and E10 blends have been in use in a number of countries for around 10 years. Also, whilst obviously less of a problem if it all goes pear shaped these fuels do have to work in the current motor car population without causing deterioration of components. Are there significant differences in the materials used in fuel systems in modern cars compared to modern light aircraft?

The water solubility issue is a problem since water cannot be drained off from E5/E10 in the normal manner. But where will water come from? Experience with large ethanol storage tanks in areas of high humidity and/or temperature swings has not shown any particular problem with water ingress from normal tank breathing. Are aircraft fuel tanks likely to behave differently? I would have thought that water is most likely to be introduced at the retail site due to poor operational/maintenance practices or through using contaminated jerry cans. The normal precautions for mogas of using clean jerry cans, not storing fuel for long periods and sourcing fuel from retail sites with a high turnover should minimise the likelihood of unacceptable water levels and other contamination. The potential for increased carburettor icing will of course be another consideration since there is the likelihood that the fuel will contain some water in solution.

From what I read on various aviation forums, mogas with up to 10% ethanol seems to be widely used in Rotax engined aircraft, particularly in the USA, with less issue than running the same engines on avgas! Are we therefore being overly conservative in the UK as well as being inconsistent?

Ethanol is here to stay and will be a challenge for us, so like Howard, I would like to know if there is any work underway, within the LAA or elsewhere, to find ways of coping with it in our aircraft.

If there is nothing in the offing then I guess we need to start saving up so that we can change to the more expensive, less (Rotax) engine friendly and less environmentally friendly option of avgas when E5 becomes the norm at our retail sites within the next 12 months or so! In any case it would be useful to have some guidance on the use of mogas with ethanol in microlights in the hope that we can make it sensible as well as legal.

[Rod1]

Alan,

It is expected that around 1/3 of UK biopetrol will use ETBE, instead of Ethanol. ETBE has none of the problems of bioethanol.

Rod1

[ian herdis]

With the ever increasing price of avgas its soon going to be a case of mogas or no gas !!!!!!

I am about 2 years away from engine selection/install and hope that a suitable diesel will be available by then.

[howard bradley]

Rod 1 thanks for your input ,where did you find the info regarding the none use of Ethanol in Mogas , and that a 1/3 would not have it .
With ref to your answer Barry I did not appreciate you were on the LAA commitee , if this is correct , will the LAA be in discussion with the CAA regarding Ethanol loaded Mogas for Cat A aircraft , and the fact they have given clearance for Microlights ? The subject is hotting up in the GA forums

[Rod1]

A flying friend who is a consultant in the fuel industry. ETBE has been discussed on numerous occasions including in the mag. I have some emails I exchanged with PFA eng about 3 years ago indicating they were aware of the problem and working on it (John T specifically).

Rod1

[Mark A]

Rotax provide a good summary of their position in http://www.rotax-aircraft-engines.com/p ... d03830.pdf (page 8 and 9).

Having flown to Sweden a few times, I've been impressed with the way Hjelmco have been reacting in producing Avgas 91/96UL which is approved for nearly all piston aircraft except a few high compression or turbocharged cases. They have produced an Avgas 100UL, but are still trying to get ASTM to accept the different anti-knock ingredients in the D910 Avgas spec. They are one of 4 Avgas producers left in Europe and the only one producing unleaded.

Most airfields are only likely to keep one grade of fuel so the goal would be a universal unleaded Avgas. I think we will always be paying a premium for a high quality aviation fuel (notwithstanding a viable Diesel).

The Swift bio-AVGAS seems to have gone quiet since their announcement, but we live in hope.

[Mike Fortescue]

Heard on R4 'PM' tonight (feature on how demand for 'biofuels' is leading to harsh working conditions for cane cutters in Brasil) that Mogas in UK forecourt pumps already contains typically 2.5% biofuel. Not necessarily reliable (R4 after all!) nor necessarily alcohol ..

[Rod1]

Biofuel does not necessarily contain Ethanol, ETBE based biofuel is likely to be widely available in the UK as well as Bioethanol.

The Max concentration of “bioagents” in UK fuel is 5% (up to 2020 I think). Most is 0% as of today.

Rotax say;

http://www.rotax-aircraft-engines.com/p ... d03830.pdf

This allows 5% Ethanol as far as the engine is concerned. (Your fuel system may or may not be ok).

The CAA say that me must not use fuel with Ethanol in it. There is a CAA approved test for Ethanol. Any fuel which passes this test is OK to use. The test will not detect 5% concentrations of Ethanol.

If you run a Rotax 912 engine for more than 30% of the time on Avgas you will have to ½ the service intervals and it is not recommended by the manufacturer (see above link).

There has been some scare mongering over this issue. It is important and there are some problems, but it is not as black as some are painting it.

Rod1

[Alan Adams]

Mogas with ETBE will certainly make life a bit easier for mogas users but not sure how widely available it will be. In any case, as long as the fuel meets the EN 228 specification, it is most likely there will be no indication on the retail pumps as to whether the mogas contains Ethanol, ETBE or any other oxygenate so it may not be easy to find an appropriate source of supply.

I agree with Rod that the issue “is not as black as some are painting it” but some enlightened guidance on the subject for aviators would be very welcome.

[Barry Plumb]

Gents,

Hidden away in the pre-budget report is a section on Hydrocarbon Oils ; Duty Rates.

Item 8 notes that :-

The current duty differential of 20 p per litre for biofuels for road use will cease from 2010 and duty will thereafter be charged at the same rate as main road fuels.

This has, at a stroke, removed any financial incentive for Fuel manufacturers and distributors to blend bioethanol or biodiesel into forecourt fuels. Bearing in mind the acute technical difficulties involved in the manufacture, distribution and supply chain for these fuels, why would any manufacturer now bother with biofuels.

We will see what happens.

Safe Landings

Barry Plumb

[Alan Adams]

The loss of the duty differential does not make the problem go away! The European Bio-fuels Directive 2003/30/EC requires member states to have national targets for the introduction of bio-fuels for road transport. The UK response to this directive is the Renewable Transport Fuels Obligation Programme which came into force earlier this year with stage targets for bio-fuels up to 5% in 2010/11. There is however a proposed amendment to the RTFO, currently out to consultation, to extend the timeframe from 2010 to 2013 to reach the 5% target. The duty differential was only in place to help get the necessary investment kick started and was planned to disappear in 2010/11. In fact there is a penalty to suppliers who do not meet the annual bio-target!

The bio fuels target percentage increases year by year and should already be around 2.5%. This percentage is of total road fuels so covers both mogas and diesel and currently the target is likely to be largely met from bio-diesel and with only relatively small quantities of mogas affected. However, next year will see the availability of mogas with up to 5% ethanol begin to ramp up as the ethanol investment projects currently underway begin to come on line. Even if an extended timeframe is agreed it may not have any major impact on the big suppliers/retailers since the rather complex supply chain will already be largely committed to producing mogas with ethanol.

I see in this month’s Light Aviation there is a letter on the subject of ethanol in mogas in which “Name and address supplied” is hoping that the LAA is taking up the issue with the CAA. It is a pity that the “Ed’s Comment” did not comment on this aspect of the letter.

[rkeech]

I thought that you would like to know this, especially those
who regularly use mogas in their aircraft as do I.
You're no doubt well aware that it is not approved to use
fuel that contains any alcohol in aircraft because it is feared that this would lead to deteriortion/softening/corrosion etc of components of the fuel system. I've always tested my mogas for the presence of alcohol using the "water in a tube" method, but a few weeks ago I did purchase a much more sensitive fuel testing kit from Pete Smoothy at Airworld. Using this new kit I never was able to detect any alcohol in my fuel
(always puchased from Morrisons), that is, until today when the test
revealed its presence. I repeated the test with a different test
bottle and achieved the same result. Therefore, from this I can
certainly conclude that certain refineries are actually using alcohol
rather than merely just threatening to (they're allowed to use up to
5% alcohol).

Out of interest I then re-tested the fuel using the old "water in
the tube" method and was not able to detect the presence of alcohol
which just goes to show that this test just isn't sensitive enough to
show up the small quantities of alcohol that are allowed in the UK.
Given that I had never detected any alcohol before, even using the
new sensitive test kit, I had almost assumed that, whilst being
allowed to contain alcohol, our petrol was actually free of it. I
suppose the moral of this is that the old maxim, "Don't Assume -
Check" still holds good! Richard Keech.