Natural Gas

[Tmpendergrass]

Ethanol is a joke. It is creating a food shortage in the third world and requires more energy to refine then in makes after it's burned.


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[Clark1961]

How well do they hold up under duress? I'd hate to see every garden variety ground loop or runway excursion turn into a fireball. I know that tanks and bladders leak on impact as well, but my impression is that the immediacy and the magnitude of the danger is higher for CNG than 100LL or diesel.

Why do you say this? Methane has a couple characteristics which make it less likely to be a problem than 100LL. The major one is that it is lighter than air so it disperses rapidly upward. Another is that it is lower energy content per unit mass so the un-contained combustion is fairly cool compared to gasoline. The final bit is that a fuel tank is pressurized so no mixing will occur until the methane leaves through a leak or the tank is totally destroyed. Ever see a propane tank in a fire? They generally don't explode but they will vent and create a flame jet.

 

[Henning]

How well do they hold up under duress? I'd hate to see every garden variety ground loop or runway excursion turn into a fireball. I know that tanks and bladders leak on impact as well, but my impression is that the immediacy and the magnitude of the danger is higher for CNG than 100LL or diesel.

I think we (meaning piston aircraft) are going to have to go to diesel sooner or later because then everyone on the airport will be burning one fuel: JetA. We no longer have the demand to support our own dedicated infrastructure, and the ones burning the volume will get to call the tune -- we're going to have to dance to it or go home.

Actually I think CNG will be safer. Methane is lighter than air so everything will go up, no burning fuel on the ground to envelope the plane and pax. Also with a composite tank you don't have quite the same shrapnel issues as with aluminum. If it does rupture since the gas is light and the ignition sources low, they are less likely to ignite, and if they do, you'll get an overhead flame ball. With a composite tank, if that flame all makes it down to the container it will melt it opening the rupture and releasing the pressure.

 

[pilot117]

They generally don't explode but they will vent and create a flame jet.

He's right. Easily demonstrated with a camp fire, 20lb or larger cylinder of gas, and a 12ga slug. Hell of a flame! Best experienced after sunset.

 

[Henning]

Why do you say this? Methane has a couple characteristics which make it less likely to be a problem than 100LL. The major one is that it is lighter than air so it disperses rapidly upward. Another is that it is lower energy content per unit mass so the un-contained combustion is fairly cool compared to gasoline. The final bit is that a fuel tank is pressurized so no mixing will occur until the methane leaves through a leak or the tank is totally destroyed. Ever see a propane tank in a fire? They generally don't explode but they will vent and create a flame jet.

Eesh, propane is a bad example since it's liquid, heavier than air and subject to BLEVE. I haven't seen one in person, but fire school has half a day's worth of BLEVE films to watch. Here's one of the standards: http://m.youtube.com/watch?v=UlYJrI_hk_M

Composite tanks though don't have this failure mode and would be much safer.

 

[Clark1961]

He's right. Easily demonstrated with a camp fire, 20lb or larger cylinder of gas, and a 12ga slug. Hell of a flame! Best experienced after sunset.

Never seen it done that way...don't really want to.

The one truly dangerous condition I've seen was a propane tank thermal plug rupture in an enclosed space (essentially a small shed) - lifted the roof many feet in the air when it ignited. Obviously CNG could do something similar if it vented into the cabin or engine compartment. Tip tanks may make a lot of sense.

 

[John Baker]

So what would actually be involved in converting a Cessna or Piper entry level type thirty year old aircraft over to using natural gas? What would be involved in getting the FAA and NTSB to certify it as being safe, or could that even be done?

I have a hunch that if a person could afford to do those things, the cost of fuel would not be of all that much importance to them, and that it would be highly unlikely that they would even own a 30 year old entry level aircraft.

Then one last thought, how long would it take from the "I aught to do that" light bulb going on in someones head, to the time they make their first take off?

-John.

 

[Henning]

So what would actually be involved in converting a Cessna or Piper entry level type thirty year old aircraft over to using natural gas? What would be involved in getting the FAA and NTSB to certify it as being safe, or could that even be done?

I have a hunch that if a person could afford to do those things, the cost of fuel would not be of all that much importance to them, and that it would be highly unlikely that they would even own a 30 year old entry level aircraft.

Then one last thought, how long would it take from the "I aught to do that" light bulb going on in someones head, to the time they make their first take off?

-John.

If someone wanted to do it, it would take about two weeks and $2000 on an experimental, and you could even have a 'dual fuel' setup where you could keep your gasoline system and run it on gas. All the parts are available "off the shelf" right now.

 

[Clark1961]

If someone wanted to do it, it would take about two weeks and $2000 on an experimental, and you could even have a 'dual fuel' setup where you could keep your gasoline system and run it on gas. All the parts are available "off the shelf" right now.

The "off the shelf" CNG systems use gasoline for engine start then switch to natural gas.

 

[Jimmy cooper]

Boone Pickens was talking mainly trucks as the truck stops could be easily converted to selling NG. If this were done he claimed it would help immensely in our current "scarcity" of fuel, (which I think is a manufactured crisis) General aviation aircraft is not really in the mix. If a major monopoly oil co. Can afford a 370 million dollar retirement bonus (plus regular salary and lifetime perks) they can certainly afford to keep G.A. In proper and affordable fuel. ( Forgot to mention the TREMENDOUS Govt. Subsidies paid to big oil.) Sound right?

 

[John Baker]

If someone wanted to do it, it would take about two weeks and $2000 on an experimental, and you could even have a 'dual fuel' setup where you could keep your gasoline system and run it on gas. All the parts are available "off the shelf" right now.

Henning, thank's for your input. No disrespect intended, this is an honest train of thought; You make it seem simple and inexpensive, why, if NG is only 85 cents a gallon, isn't anyone doing it? I would think that flight schools especially would be all over this like a cheap suit.

Could I do it to my old Jeep for around the same price?

-John

 

[Henning]

Henning, thank's for your input. No disrespect intended, this is an honest train of thought; You make it seem simple and inexpensive, why, if NG is only 85 cents a gallon, isn't anyone doing it? I would think that flight schools especially would be all over this like a cheap suit.

Could I do it to my old Jeep for around the same price?

-John

Yep, the kits are available. Propane is easier and more practical. In Australia the kits are commonplace, even factory cars come with straight 'gas' systems, and most every servos hat has petrol (that's a gas station around here selling gasoline) has a 'gas' pump as well. Probably 30% of cars there are 'dual fuel' equipped and most all the taxis are straight gas so they only have to give up the space for tanking one fuel. The kits have been available from J.C. Whitney (among many other distributors) for over half a century now.

 

[txflyer]

Back in the seventies, we had a farm truck you could switch from gas to LP. It had a bottle sideways in the front of the bed. I think it was a 80 gallon LP tank.

That was a good truck. Very versatile and long range.

 

[Everskyward]

Henning, thank's for your input. No disrespect intended, this is an honest train of thought; You make it seem simple and inexpensive, why, if NG is only 85 cents a gallon, isn't anyone doing it? I would think that flight schools especially would be all over this like a cheap suit.

Could I do it to my old Jeep for around the same price?

Pretty sure part of the problem is that you need more volume to get the same range, both on cars and airplanes. I loaded bags into someone's natural gas SUV and a large part of the baggage area was taken up by the tank. I know it was the tank because I asked him. So if you are used to going 400 miles on a tank of car gas or 4 hours on an airplane tank you will be getting less than that unless you add extra tanks. Someone else could probably estimate how much less.

 

[N801BH]

Eesh, propane is a bad example since it's liquid, heavier than air and subject to BLEVE. I haven't seen one in person, but fire school has half a day's worth of BLEVE films to watch. Here's one of the standards: http://m.youtube.com/watch?v=UlYJrI_hk_M

Composite tanks though don't have this failure mode and would be much safer.

Hmmmm...

I could be wrong.. But... I thought when you fill a CNG tank the product turns to a liquid just like propane does under pressure...

 

[Cap'n Jack]

Hmmmm...

I could be wrong.. But... I thought when you fill a CNG tank the product turns to a liquid just like propane does under pressure...

Not methane. You're thinking of LNG, liquified natural gas. Most vehicles seem to use compressed natural gas.

 

[Cap'n Jack]

Pretty sure part of the problem is that you need more volume to get the same range, both on cars and airplanes. I loaded bags into someone's natural gas SUV and a large part of the baggage area was taken up by the tank. I know it was the tank because I asked him. So if you are used to going 400 miles on a tank of car gas or 4 hours on an airplane tank you will be getting less than that unless you add extra tanks. Someone else could probably estimate how much less.

Unless you liquefy it, which doesn't seem to be done often in vehicles, that's the problem. Same issue as hydrogen, but not nearly as bad as hydrogen.

 

[PPC1052]

The ONLY people who benefit from this screwy mandate are corn farmers. Everyone else loses...

That is SO rediculous.



The congress-critters and the lobbyists get fat, too.

 

[Henning]

Hmmmm...

I could be wrong.. But... I thought when you fill a CNG tank the product turns to a liquid just like propane does under pressure...

Nope, CNG is methane, it has to be run through an LNG plant to be changed to liquid. Many boats have switched to "SafeGas" which is compressed natural gas.

 

[Henning]

Not methane. You're thinking of LNG, liquified natural gas. Most vehicles seem to use compressed natural gas.

Most vehicles currently use LPG, although CNG is on the rise in the public transport sectors as well as shipping.

 

[airguy]

Henning, thank's for your input. No disrespect intended, this is an honest train of thought; You make it seem simple and inexpensive, why, if NG is only 85 cents a gallon, isn't anyone doing it? I would think that flight schools especially would be all over this like a cheap suit.

Could I do it to my old Jeep for around the same price?

-John

It's not commonly done because if you do it yourself there is no guarantee that it won't blow up in your face and most people don't want to take the chance, and it will void your vehicle warranty to boot. To do it professionally with current emissions standards requires the company to prove conformance of the conversion, which is time consuming and expensive, and they then charge a high price to install that in your vehicle to recover that cost.

If you start researching propane conversions, you'll find many for sale but they all state that they are not legal for on-road use (emissions requirements). CNG conversions ARE available, but at prices ranging from $8k to $12k per vehicle, and only for the vehicles that they have type-certified for the conformance test. It's very similar to an STC for aircraft.

 

[denverpilot]

Boone Pickens was talking mainly trucks as the truck stops could be easily converted to selling NG. If this were done he claimed it would help immensely in our current "scarcity" of fuel, (which I think is a manufactured crisis) General aviation aircraft is not really in the mix. If a major monopoly oil co. Can afford a 370 million dollar retirement bonus (plus regular salary and lifetime perks) they can certainly afford to keep G.A. In proper and affordable fuel. ( Forgot to mention the TREMENDOUS Govt. Subsidies paid to big oil.) Sound right?

It's not a manufactured crisis. But it has more to do with not building any new refineries in a very long time, than supply of crude.

Buffett cashed in on the Dakotas by buying a railroad to get product to Texas and the pipeline companies are building like mad. In theory it'd be cheaper to put another refinery up there, but not in the current regulatory environment. Tesoro is the only game in town.