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  #1  
Old 07-30-2013, 05:17 PM
srv srv is offline
 
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Default CNG alternative? Dual-fueled Husky to be at AirVenture

http://www.aviataircraft.com/cng/

Kinda surprised by this, but can't tell if the 7 hour claim is CNG only or CNG + LL tanks from the story:

Q: How long can you fly the Husky CNG on full fuel tanks?
A: The demonstration aircraft can be flown approximately seven hours at a 65 percent power setting.

Q: What does GGE mean and how does that relate to AVGAS?
A: GGE stands for ?gas gallon equivalent,? that is the amount of compressed natural gas it takes to equal approximately one gallon of gasoline in terms of energy. One GGE of natural gas is 123 cubic feet and weighs approximately 5.66 lbs. vs. 6.01 lbs. for 100LL AVGAS.
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  #2  
Old 07-30-2013, 05:29 PM
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So the fuel is close in weight, not surprising considering they both come out of the same hole in the ground.

What comes immediately to my mind is;

What is the tank weight????

If it is hard to find Mogas at an airport, what do you think it is going to be like to find a CNG pump??
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Last edited by Mike S : 07-30-2013 at 05:47 PM.
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  #3  
Old 07-30-2013, 05:40 PM
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I saw these guys yesterday. I was going to stop and ask the same question about the tank. I'm also curious how they maintain a consistent pressure. I'm going back on Thursday, I'll ask when I go by.
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  #4  
Old 07-30-2013, 05:59 PM
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Default Neat

All the way at the bottom of the page...

Quote:
Q: What is the additional weight of a typical CNG system in a GA aircraft?
A: Of course that depends on the aircraft, and the CNG system being installed. The tank is definitely the largest factor. For example the all-composite “Type 4” tank we installed for this demonstration aircraft has a GGE of 9.2 gallons (35 liters) and weights 95 lbs. empty. In this rapidly advancing field, tanks keep getting lighter and are available in a variety of capacities with even greater weight efficiencies. The balance of the non-structural materials is perhaps 10 lbs.
Given the tank capacity of 9.2 gallons I suspect their 7 hour claim is burning avgas. Still. Neat stuff. I've driven natural gas vehicles and you can't tell the difference in any way.
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Old 07-30-2013, 06:07 PM
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Default After reading the linked info.........

So, the full tank weighs just under 150 pounds, and it seems that you would usually have to take it somewhere to fill it.

Then, put it back in the plane------oh my aching back

Here is an interesting quote lifted from the link, " We have noted several performance advantages using CNG over aviation gasoline. One is increased power output given that octane rating of natural gas is typically 138 vs. aviation gasoline?s 100."

Am I the only one who has a bit of trouble with this statement???
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"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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Old 07-30-2013, 06:55 PM
aerhed aerhed is offline
 
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Quote:
If it is hard to find Mogas at an airport, what do you think it is going to be like to find a CNG pump??
Don't you just steal the bottles off your grill and throw them in the back seat?
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Old 07-30-2013, 07:32 PM
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Quote:
Originally Posted by aerhed View Post
Don't you just steal the bottles off your grill and throw them in the back seat?
At 40 or so pounds full, not an issue.

Also, the BBQ runs on propane, not CNG.
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Flying as of 12/4/2010

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"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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Old 07-30-2013, 09:11 PM
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Quote:
Originally Posted by Mike S View Post
Here is an interesting quote lifted from the link, " We have noted several performance advantages using CNG over aviation gasoline. One is increased power output given that octane rating of natural gas is typically 138 vs. aviation gasoline’s 100."

Am I the only one who has a bit of trouble with this statement???
Actually, that's about right. It varies from around 125 to 140 depending on the exact mix, but the common "pipeline" gas running into peoples homes and compressed for CNG is typically going to yield 135 octane, plus or minus a couple points.

The increased power output is a bit of a stretch - cube for cube and all other things being equal, CNG engines normally deliver about 80% of the horsepower that an equivalent gasoline engine will at the same RPM and manifold pressure.
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  #9  
Old 07-30-2013, 09:44 PM
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Quote:
Originally Posted by airguy View Post
The increased power output is a bit of a stretch - cube for cube and all other things being equal, CNG engines normally deliver about 80% of the horsepower that an equivalent gasoline engine will at the same RPM and manifold pressure.
Exactly what I was referring to.

Horse power is not effected by octane. http://www.whitfieldoil.com/www/docs...p-racing-fuel-
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"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
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  #10  
Old 07-31-2013, 11:20 AM
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Correct, but higher octane fuels have higher detonation margins can be run leaner and with more advanced timing, which directly leads to more power.
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