Running on mogas?
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Running on mogas?
What's the story in the UK about running on mogas? Operators of 150HP Super Cubs in the US are doing it routinely, as are they in Europe. Is this possible here?
QDM
QDM
Why do it if it's not fun?
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It's only allowed for PFA aircraft, not for CofA. The filling points must be appropriately labelled. I suspect you'll need the PFA to agree to it for your type, but I don't know how this works.
Once you have more than a certain percentage of MoGas in your tank (is it 80%? I can't remember) you're not allowed above 6000', and you're not allowed to fly with a tank temperature of over 25 degrees C.
Also, make sure you have a reliable source of MoGas! My Europa had a serious problem of black bits collecting in the fuel filters. We couldn't figure out what it was. Then the petrol station next to the airfield closed. Although the black bits haven't completely gone, there are far fewer of them now - the local petrol station was obviously supplying contaminated fuel.
The PFA are the people to speak to for definitive answers.
FFF
---------------
Once you have more than a certain percentage of MoGas in your tank (is it 80%? I can't remember) you're not allowed above 6000', and you're not allowed to fly with a tank temperature of over 25 degrees C.
Also, make sure you have a reliable source of MoGas! My Europa had a serious problem of black bits collecting in the fuel filters. We couldn't figure out what it was. Then the petrol station next to the airfield closed. Although the black bits haven't completely gone, there are far fewer of them now - the local petrol station was obviously supplying contaminated fuel.
The PFA are the people to speak to for definitive answers.
FFF
---------------
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u/l mogas
QDM
OK for your PA 18-150 ( if you must !)
Airworthiness notice 98c is where to look !
Unless on public cat C of A
TTH
OK for your PA 18-150 ( if you must !)
Airworthiness notice 98c is where to look !
Unless on public cat C of A
TTH
Last edited by Them thar hills; 12th Oct 2002 at 11:59.
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I use to fly PA 18 150s on mogas in the early 80s glider towing. the best fuel was the old 2 star, lead content i belive. Later we had to fly on 4star as 2 star was not approved.
There were no problems with the Cub but big problems with other types Chipmunks had to leave the cowlings open after shutdown otherwise the fuel will boil in the main pipe next to the engine block. The supermunk was a disaster, lost count how many failours i had with fuel vaporisation. As soon as it vaporised you would lean out till you got to the point where it would rich cut & lean cut at the same time very sporting!
There were no problems with the Cub but big problems with other types Chipmunks had to leave the cowlings open after shutdown otherwise the fuel will boil in the main pipe next to the engine block. The supermunk was a disaster, lost count how many failours i had with fuel vaporisation. As soon as it vaporised you would lean out till you got to the point where it would rich cut & lean cut at the same time very sporting!
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OK for your PA 18-150
QDM
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There are severall aircraft which have STC's to run mogas, but the engine manufacturers do not recommend it and neither do the fuel suppliers.
You might just be cynical and think that this is just a way of making more money out of pilots, but the truth is that the fuels are fundamentally different. Mogas is designed to be used on the road and no consideration is given to the requirements of aircraft in its composition, manufacture or handling.
The most obvious difference is the Octane rating. This is actually around 107 MON lean mixture rating for Avgas 100LL, compared to around 85 for the normal unleaded forecourt gasoline. The 95 octane that is often quoted for Mogas is a RON figure and not comparable to the Avgas octane ratings.
Alright, you may have an engine that does not need all of that octane, so why not use Mogas?
Well there are many differences with the fuels, including:
· Increased Ried Vapour Pressure causing greater potential for engine failure through vapour lock.
· Reduced net specific energy of the fuel (less power).
· Increased risk of elastomer swell and softening in fuel system components.
· Some automotive gasoline can contain ether and / or alcohols, which are not permitted for use in Avgas as they can potentially separate out from the fuel.
· Increased incidence of carburettor icing.
· Poor fuel distribution giving the potential of detonation.
· Fuel washing the lubricating oil off the cylinder wall at low temperatures.
· No consideration for aviation in fuel specifications.
· No consistency in the fuel in different seasons and between countries.
· Ability to change the fuel specification without considering the implication for aviation, or informing aviation customers / authorities.
· Poor storage stability when compared to Avgas.
· No control on the storage and handling of the fuel.
· No control on the water content of the fuel.
· Poor filtration requirements when compared to handling Avgas.
The most incidious of this list is vapour pressure. A high vapour pressure fuel will form a stable vapour at lower altitude and / or lower temperature than a low vapour pressure fuel. Vapours forming in the fuel supply pipes can mean vapour lock and fuel starvation.
Add to this that the road fuels change composition between winter and summer, then you really don't know what you are using. The vapour pressure of winter Mogas is high enough to form a stable vapour at around 30 deg C at ground level (less as you climb).
This temperature sounds high for our climate, but tank temperatures of this level are easily achieved by sitting an aircraft in the sun all day - added to this you have the heat from the engine.....
You really do take a risk when using Mogas, you could be lucky, but the truth is that you have to be careful with this - make no mistake, it does kill people.
You might just be cynical and think that this is just a way of making more money out of pilots, but the truth is that the fuels are fundamentally different. Mogas is designed to be used on the road and no consideration is given to the requirements of aircraft in its composition, manufacture or handling.
The most obvious difference is the Octane rating. This is actually around 107 MON lean mixture rating for Avgas 100LL, compared to around 85 for the normal unleaded forecourt gasoline. The 95 octane that is often quoted for Mogas is a RON figure and not comparable to the Avgas octane ratings.
Alright, you may have an engine that does not need all of that octane, so why not use Mogas?
Well there are many differences with the fuels, including:
· Increased Ried Vapour Pressure causing greater potential for engine failure through vapour lock.
· Reduced net specific energy of the fuel (less power).
· Increased risk of elastomer swell and softening in fuel system components.
· Some automotive gasoline can contain ether and / or alcohols, which are not permitted for use in Avgas as they can potentially separate out from the fuel.
· Increased incidence of carburettor icing.
· Poor fuel distribution giving the potential of detonation.
· Fuel washing the lubricating oil off the cylinder wall at low temperatures.
· No consideration for aviation in fuel specifications.
· No consistency in the fuel in different seasons and between countries.
· Ability to change the fuel specification without considering the implication for aviation, or informing aviation customers / authorities.
· Poor storage stability when compared to Avgas.
· No control on the storage and handling of the fuel.
· No control on the water content of the fuel.
· Poor filtration requirements when compared to handling Avgas.
The most incidious of this list is vapour pressure. A high vapour pressure fuel will form a stable vapour at lower altitude and / or lower temperature than a low vapour pressure fuel. Vapours forming in the fuel supply pipes can mean vapour lock and fuel starvation.
Add to this that the road fuels change composition between winter and summer, then you really don't know what you are using. The vapour pressure of winter Mogas is high enough to form a stable vapour at around 30 deg C at ground level (less as you climb).
This temperature sounds high for our climate, but tank temperatures of this level are easily achieved by sitting an aircraft in the sun all day - added to this you have the heat from the engine.....
You really do take a risk when using Mogas, you could be lucky, but the truth is that you have to be careful with this - make no mistake, it does kill people.
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Mogas disadvantages
One is that it can kill you.
A friend of mine had an immaculate restored WW2 trainer that he kept on a private strip.
He went to a rally on a nice warm day and there was a bit of a queue to depart so everything was warm, fuel and engine.
Shortly after take-off he lost power over some trees and stalled it in. He was killed, his passenger seriously injured.
The AAIB found he'd got Mogas in the tank. The a/c was not approved for use with Mogas. The conclusion was that he got vapour lock due to warm fuel, a high ambient, and the long wait at the hold raising teh temperature inside the cowling.
Mogas is more volatile than avgas.
Mike
A friend of mine had an immaculate restored WW2 trainer that he kept on a private strip.
He went to a rally on a nice warm day and there was a bit of a queue to depart so everything was warm, fuel and engine.
Shortly after take-off he lost power over some trees and stalled it in. He was killed, his passenger seriously injured.
The AAIB found he'd got Mogas in the tank. The a/c was not approved for use with Mogas. The conclusion was that he got vapour lock due to warm fuel, a high ambient, and the long wait at the hold raising teh temperature inside the cowling.
Mogas is more volatile than avgas.
Mike
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Some years ago our group used to regularly use MOGAS (the old MOGAS) in our A65 engine. The aircraft used to fly ok, but there were frequent problems with sticking valves etc. When the airfield's MOGAS supply shut the group changed to AVGAS exclusively. After a while, it was noticed that all the previous engine problems had disappeared. Guess which fuel has proved the most economical.
However, I know another owner who has been using MOGAS (unleaded) for over six months now in his C90 engine and (so far) he hasn't had any problems. I've never known him fly above a few thousand feet though.
However, I know another owner who has been using MOGAS (unleaded) for over six months now in his C90 engine and (so far) he hasn't had any problems. I've never known him fly above a few thousand feet though.
Why do it if it's not fun?
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Before you accept total defeat, QDM, bear in mind that Rotax recommend that their engines be run on MoGas when possilbe. They'll run off of AvGas, for example when high tank temperatures are expected, or when no source of MoGas is available, but the plugs tend to get fouled up by the lead if you use too much AvGas.
But that's not relevant to your Super Cub, which doesn't have a Rotax, so maybe you should admit defeat!
FFF
------------
But that's not relevant to your Super Cub, which doesn't have a Rotax, so maybe you should admit defeat!
FFF
------------
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Wyrmio and mrcross both make sound technical points. However, I worked in the research department of an oil company in the early 1980s, when Dick Stratton was doing a fine--and technically sound--job in demonstrating that, subject to sensible limitations, there was no problem in running mogas in certain glider-towing types.
On a pragmatic level, I have--let's say--a friend who has been running his A-65 on mogas since 1981. This is in a high-winged type, not unlike QDMQDMQDM's usual mount. My friend has not encountered a single problem with this fuel. Indeed, when he changed to mogas, he suffered much less lead fouling with the aviation plugs he used to run. (Avgas left little lead balls behind the electrodes!)
Now I am not suggesting people go out and blindly copy my friend's approach. Not everybody enjoys gravity-feed from high wings (getting around the vapour lock problem). However, avgas has too much lead for engines like the A-65, and aerodrome fuel storage/throughput can, I suspect, be poor enough to allow more water into the fuel than happens at busy--and well-run--garage forecourts.
Now the price differential has been eroded by changes in fuel duty, there is less pressure to substitute on fuel for the other. However, it is not easy for strip flyers pick up a regular supply of avgas. On the technical side, I would suggest that it is horses for courses: the most expensive and highly-regulated answer is not always the right one!
On a pragmatic level, I have--let's say--a friend who has been running his A-65 on mogas since 1981. This is in a high-winged type, not unlike QDMQDMQDM's usual mount. My friend has not encountered a single problem with this fuel. Indeed, when he changed to mogas, he suffered much less lead fouling with the aviation plugs he used to run. (Avgas left little lead balls behind the electrodes!)
Now I am not suggesting people go out and blindly copy my friend's approach. Not everybody enjoys gravity-feed from high wings (getting around the vapour lock problem). However, avgas has too much lead for engines like the A-65, and aerodrome fuel storage/throughput can, I suspect, be poor enough to allow more water into the fuel than happens at busy--and well-run--garage forecourts.
Now the price differential has been eroded by changes in fuel duty, there is less pressure to substitute on fuel for the other. However, it is not easy for strip flyers pick up a regular supply of avgas. On the technical side, I would suggest that it is horses for courses: the most expensive and highly-regulated answer is not always the right one!
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Big Bad Wolves
Read the CAA AD and Note 98.
All the isues which people have raised here have all been addresed within that note and the subsequent approvals.
The simple fact is that low compression engines were not designed to run on 100LL and all this stuff about how dangerous Mogas is in comparison conveniently ignores the fact that these engines were not certified to use 100LL.
They were approved on a paperwork basis because it was the only fuel available.
Anyone remember all the issues flying clubs had with O-235s running on 100LL?
Anyone tried running a Gipsy continuously on 100LL?
I have run my all the aircraft I have owned on it (they all fit within the CAA approved list). No problems, no issues.
Follow the steps outlined in the CAA note and enjoy some flexibilty and cost reduction in your choice of fuel.
All the isues which people have raised here have all been addresed within that note and the subsequent approvals.
The simple fact is that low compression engines were not designed to run on 100LL and all this stuff about how dangerous Mogas is in comparison conveniently ignores the fact that these engines were not certified to use 100LL.
They were approved on a paperwork basis because it was the only fuel available.
Anyone remember all the issues flying clubs had with O-235s running on 100LL?
Anyone tried running a Gipsy continuously on 100LL?
I have run my all the aircraft I have owned on it (they all fit within the CAA approved list). No problems, no issues.
Follow the steps outlined in the CAA note and enjoy some flexibilty and cost reduction in your choice of fuel.
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We run our pa18-95 on mogas never had any probs ( touches wood) it's PFA and a C90 Continental. Always generous with the carb heat. They're supposed to be more iffy at higher altitudes, but who goes up there in a Cub?
Sorry it doesn't help your situation but just letting you know that mogas in some engines is not a problem.
CC
PS Can Dakotas run on mogas? ;-)
Sorry it doesn't help your situation but just letting you know that mogas in some engines is not a problem.
CC
PS Can Dakotas run on mogas? ;-)
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The last owner of my aircraft used mogas for the cruse and avgas for take off and landing , when I picked the aicraft up from him it had one tank full of mogas.
When in the cruise I switched from the avgas to the mogas the EGT climbed by about 20F ans the RPM droped by about 25 RPM , I have not used mogas since.
When in the cruise I switched from the avgas to the mogas the EGT climbed by about 20F ans the RPM droped by about 25 RPM , I have not used mogas since.
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Gypsy Engines/ 100LL
Hi Gasax,
I operate 2 Gypsy engines (I call them Pykies!) - a 1 and a 10/2.
THe 1 is unmodded apart from the valve seats, the 10/2 has all the mods.
Both purr away happily on 100LL.
In fact I flew behind the 10/2 to Sweden and back in June (see next issue of Plot) - it was sweltering.
THe thought of Mogas over all those lakes and trees is unthinkable.
Stick it in your car - use aeroplane fuel for aeroplanes.
Too many accidents have occurred as a result of vapour lock.
I feel that there are too many people prepared to take short cuts just to save money. At the end of the day, flying costs. I think you will be surprised how many people don't even insure their aircraft for 3rd party risks.
Pay the money, fly safe. If you can't afford it, join a group.
I operate 2 Gypsy engines (I call them Pykies!) - a 1 and a 10/2.
THe 1 is unmodded apart from the valve seats, the 10/2 has all the mods.
Both purr away happily on 100LL.
In fact I flew behind the 10/2 to Sweden and back in June (see next issue of Plot) - it was sweltering.
THe thought of Mogas over all those lakes and trees is unthinkable.
Stick it in your car - use aeroplane fuel for aeroplanes.
Too many accidents have occurred as a result of vapour lock.
I feel that there are too many people prepared to take short cuts just to save money. At the end of the day, flying costs. I think you will be surprised how many people don't even insure their aircraft for 3rd party risks.
Pay the money, fly safe. If you can't afford it, join a group.
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It's a few days since I have been able to log on to PPRuNe, so quite a few replies on this since I last visited !
I just want to clarify a couple of points.
Gasax says, quite correctly that
Well true, the early engines were not certified on Avgas 100LL as it did not exist at the time. Neither were these engines certified on Mogas. Avgas 100LL is a closer in its properties to the fuels that the early engines were originally certified on in terms of boiling point range and hydrocarbon content. Believe me, I work in this field.
Don't be fooled into thinking that because Mogas is an unleaded fuel of mid 80's MON octane number then this is a close analogue of leaded Avgas 80/87, or even the pre war unleaded Avgas 80; the base fuel composition and properties are quite different.
All of these engines are now certified to run on Avgas 100LL, but only some aircraft carry limited use STC's to use Mogas. The use of Mogas is not approved at all by the engine manufacturers (Rotax aside). This should tell you something.
As I have said in my earlier posting, Notice 98 does put a limitation on altitude and tank temperature for Mogas use, and notice that it is a tank temperature NOT an air temperature.
Think about this for a minute in this scenario.
You fly on a nice summer's day to visit another airfield and leave your aircraft parked outside in the sun. Air temp can be low 20's, but the sun beating down on the tank can easily raise it's temperature significantly above the air temp. You have no way of measuring the tank temperature, so you have to guess you could be OK, but don't know.
What will you do if you suspect that you are near the limit, drain the fuel and replace it? Postone your flight until the next day? Or will you do what most people do, not even realise that it could be a problem and set off for home. The AAIB will investigate the crash and conclude that you were probably outside the guideance of Notice 98 and so the CAA is in the clear. The fault is yours. Notice 98 does not get changed, as there is no need to -you did not observe the restrictions. People will also continue to read notice 98 and assume that, if their aircraft has an STC then they have carte blanche to use Mogas, but they do not.
As has been said before, Avgas is for aircraft, Mogas is for cars. If you use Mogas for aircraft do not think for one minute that it is as safe and controlled as using Avgas.
This brings me on to another point.
Philip Whiteman makes another point.
Well fair point on the Lead levels for some engines that run notoriously low combustion temps like A series Continentals, but fiitting a hotter plug and doing an engine run up at the end of a flight is normally enough to let the Lead scavenger in Avgas 100LL to do it's job and clear plugs. The run up involves getting to the parking spot, stabalising the CHT and running at 1800 rpm for 20 - 30 seconds before going back to idle and immediately bringing the mixture lever back for a lean cut.
More info on this can be found in Lycoming's excellent "Flyer" publication - advice that transers to the TCM engines just as well.
As for the water issue - I would have to differ with Philip.
There are rules covering the storage and handling of Avgas in a CAA publication called CAP 434. This stipulates not only equipment standards for storage that are beyond those required for storing Mogas, but also that Avgas tank and filter drains must be checked and cleared of water and debris every day, after a bulk fuel receipt and after rain or snow. Not so for Mogas.
There are also filtration requirements. Speaking for Shell supplied Avgas sites, the final filtration before aircraft delivery is a water absorbant filter. This contains media which chemically reacts and traps any water in the fuel and so Shell can, hand on heart, say that the fuel supplied is filtered to 5 microns for particles (human hair is about 20 microns in diameter) and contains less than 10 parts per million of water.
There are no tank draining or sump inspection criteria for Mogas tanks, and neither is there any filtration requirements for the outflow. If you are lucky your local Mogas forcourt may have a plain mesh filter of about 200 microns. If you are lucky.
There are plenty of people who have run for years on Mogas without a problem, but my point is that it is incurring an additional risk that one day might catch up with you. Remember that no public cat aircraft are allowed to use Mogas. Ask yourself why this might be? It is because inflicting this additional risk on the fare paying public has been deemed unacceptable.
My view is that it is unacceptable for me and my loved ones also.
Good luck.
I just want to clarify a couple of points.
Gasax says, quite correctly that
The simple fact is that low compression engines were not designed to run on 100LL and all this stuff about how dangerous Mogas is in comparison conveniently ignores the fact that these engines were not certified to use 100LL.
Don't be fooled into thinking that because Mogas is an unleaded fuel of mid 80's MON octane number then this is a close analogue of leaded Avgas 80/87, or even the pre war unleaded Avgas 80; the base fuel composition and properties are quite different.
All of these engines are now certified to run on Avgas 100LL, but only some aircraft carry limited use STC's to use Mogas. The use of Mogas is not approved at all by the engine manufacturers (Rotax aside). This should tell you something.
As I have said in my earlier posting, Notice 98 does put a limitation on altitude and tank temperature for Mogas use, and notice that it is a tank temperature NOT an air temperature.
Think about this for a minute in this scenario.
You fly on a nice summer's day to visit another airfield and leave your aircraft parked outside in the sun. Air temp can be low 20's, but the sun beating down on the tank can easily raise it's temperature significantly above the air temp. You have no way of measuring the tank temperature, so you have to guess you could be OK, but don't know.
What will you do if you suspect that you are near the limit, drain the fuel and replace it? Postone your flight until the next day? Or will you do what most people do, not even realise that it could be a problem and set off for home. The AAIB will investigate the crash and conclude that you were probably outside the guideance of Notice 98 and so the CAA is in the clear. The fault is yours. Notice 98 does not get changed, as there is no need to -you did not observe the restrictions. People will also continue to read notice 98 and assume that, if their aircraft has an STC then they have carte blanche to use Mogas, but they do not.
As has been said before, Avgas is for aircraft, Mogas is for cars. If you use Mogas for aircraft do not think for one minute that it is as safe and controlled as using Avgas.
This brings me on to another point.
Philip Whiteman makes another point.
However, avgas has too much lead for engines like the A-65, and aerodrome fuel storage/throughput can, I suspect, be poor enough to allow more water into the fuel than happens at busy--and well-run--garage forecourts.
More info on this can be found in Lycoming's excellent "Flyer" publication - advice that transers to the TCM engines just as well.
As for the water issue - I would have to differ with Philip.
There are rules covering the storage and handling of Avgas in a CAA publication called CAP 434. This stipulates not only equipment standards for storage that are beyond those required for storing Mogas, but also that Avgas tank and filter drains must be checked and cleared of water and debris every day, after a bulk fuel receipt and after rain or snow. Not so for Mogas.
There are also filtration requirements. Speaking for Shell supplied Avgas sites, the final filtration before aircraft delivery is a water absorbant filter. This contains media which chemically reacts and traps any water in the fuel and so Shell can, hand on heart, say that the fuel supplied is filtered to 5 microns for particles (human hair is about 20 microns in diameter) and contains less than 10 parts per million of water.
There are no tank draining or sump inspection criteria for Mogas tanks, and neither is there any filtration requirements for the outflow. If you are lucky your local Mogas forcourt may have a plain mesh filter of about 200 microns. If you are lucky.
There are plenty of people who have run for years on Mogas without a problem, but my point is that it is incurring an additional risk that one day might catch up with you. Remember that no public cat aircraft are allowed to use Mogas. Ask yourself why this might be? It is because inflicting this additional risk on the fare paying public has been deemed unacceptable.
My view is that it is unacceptable for me and my loved ones also.
Good luck.