bravogolf
Posts: 359
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Lack Of High Octane Avgas

Sat Feb 18, 2006 2:02 am

I read a while ago that 120-130 octane was no longer available now that the military no longer neeeds it. What do the still flying Connies and the like do for fuel? Did they reduce compression of what?
 
IAHFLYR
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 2:13 am

They head down to the closest NASCAR/INDY Car track!  Smile
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bravogolf
Posts: 359
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 2:17 am

I can see them flairing on the strightaway, but the first turn must be a bitch!
 
Fly2HMO
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 2:35 am

Quoting IAHFLYR (Reply 1):
They head down to the closest NASCAR/INDY Car track!

I don't think those big radials would like to burn methanol....
 
IAHFLYR
Posts: 3941
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 2:47 am

Quoting FLY2HMO (Reply 3):
I don't think those big radials would like to burn methanol....

Hey never know till ya try! lol
Any views shared are strictly my own and do not a represent those of any former employer.
 
Tornado82
Posts: 4662
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 3:13 am

Quoting FLY2HMO (Reply 3):
I don't think those big radials would like to burn methanol....

NASCAR runs on gasoline still.
 
2H4
Posts: 7960
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 4:00 am




Quoting Tornado82 (Reply 5):
NASCAR runs on gasoline still.

...And here I thought those things ran on coal.




2H4 - Formula One Fan  Wink


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MrChips
Posts: 933
Joined: Wed Mar 30, 2005 2:56 pm

RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 4:55 am

Quoting Bravogolf (Thread starter):
I read a while ago that 120-130 octane was no longer available now that the military no longer neeeds it. What do the still flying Connies and the like do for fuel? Did they reduce compression of what?

If I'm not mistaken, those aircraft can run on either 100 or 100LL gasoline with little or no difficulty. With the earlier of the large piston airliners (DC-3s, DC-4s, DC-6s and early model Constellations), they can run on 100 or 100LL gasoline with no restrictions or modifications, as that gasoline is of an equal grade to what they were designed for.

The later models (DC-7s and late model Constellations) can run on 100 gasoline with only a placard indicating permissible manifold pressures, as they have to sacrifice some power for the sake of keeping the engine intact.
Time...to un-pimp...ze auto!
 
KELPkid
Posts: 5247
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 5:36 am

Quoting Bravogolf (Thread starter):
I read a while ago that 120-130 octane was no longer available now that the military no longer neeeds it. What do the still flying Connies and the like do for fuel? Did they reduce compression of what?

I talked to the flight crew of the Commemorative (used to be "Confederate") Air Force's "FiFi", the world's last airworthy B-29, the last time I saw her. Their engines were designed for 130 octane (purple) avgas. They said that they are basically using emergency procedures every time they fly her...(there were operating procedures in the Air Force operating manual [dash-2?] for operating on 100 octane gas, and they use these). They basically can't get the full rated power out of their "corncob" (4-row!) raidals because of the octane limits. The flight engineer handles most of the work related to keeping the engines from detonating. Not sure what he really does, I don't think the flight engineer can handle things like ignition timing...maybe he can, but I don't know.

There is at least one time a year, however that 130 octane is brewed again: the Reno Air races  Cool (and I read this in "Flying" magazine a couple of years ago!).
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bravogolf
Posts: 359
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 5:52 am

Wouldn't retarding the ignition timing cause overheating?
 
KELPkid
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 6:07 am

Quoting Bravogolf (Reply 9):
Wouldn't retarding the ignition timing cause overheating?

I'd imagine, but they can also run the mixture rich of peak, which would keep the engines from detonating...the problem with this is that the plugs would foul with carbon.
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bravogolf
Posts: 359
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 6:43 am

How many plugs on FIFI?
 
KELPkid
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 7:02 am

Oops, FiFi's engines aren't 4 row, only two row:

http://itfp.lps.org/fifi2/b29.html

2x18 cylinders=36 plugs per engine, a mere 144 plugs to clean after a flight  Big grin
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
 
Buzz
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 3:42 pm

Hi BravoGolf, Buzz here. We've been using 100LL (the blue gas) on DC-3's and Lockheed Harpoons. 48 inches MP for takeoff is still permitted, and we pull the power back a few times during climb.
Regarding FiFi (the B-29) you shouldn't need to clean sparkplugs very often. Ours run clean, we don't run really rich of peak. The F/E pretty much sets the power (MP and RPM) and mixture, per the left seater's request. I don't think anybody has the engines that adjust the timing anymore, the P+W 1830-75 engines were made to advance the timing for better efficiency in cruise. Most of them are secured to 25 degrees BTC.
I'm not looking forward to the demise of 100LL avgas, it's a concentrated, useful fuel... although rather poisonous.
You can get the STC to run many of the smaller aircraft engines on auto gas, but you need to check the fuel for alcohol before use. Alcohol is good for cars, but a lot of the aircraft hoses / seals soften in alcohol.
 
2H4
Posts: 7960
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RE: Lack Of High Octane Avgas

Sat Feb 18, 2006 3:56 pm




Quoting Buzz (Reply 13):
You can get the STC to run many of the smaller aircraft engines on auto gas

I've always wanted to roll up to an FBO and tell them I need mo' gas...


 rotfl 




2H4


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bravogolf
Posts: 359
Joined: Thu Apr 21, 2005 6:18 am

RE: Lack Of High Octane Avgas

Sun Feb 19, 2006 12:14 am

Being at the south tip of Lake Michigan we get treated to an airshow of sorts just before Oshkosh. You hear the sound of multiple heavy radials and start looking. The best was a few years ago when two B17s came over in formation. A short time later here comes FiFi. Lets hope that these warbirds and the Connies can keep flying. Nothing else sounds so good.
 
L-188
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RE: Lack Of High Octane Avgas

Tue Feb 21, 2006 2:14 am

We filled up DC-6's and DC-3's tanks with the same 100LL that everybody else was burning.

It has been a while since I have looked at the list, but I think the R1830 and the R985 both have the Autogas STC available to them.

Where I used to work, we we cleaning up some old fuel tanks from the 1950's and found one that has some purple gas in it. One of the guys ran it in his pieced together chevy that he had.....that 350 supposedly ran...real good on it.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
Tod
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RE: Lack Of High Octane Avgas

Tue Feb 21, 2006 3:15 am

Quoting L-188 (Reply 16):
Where I used to work, we we cleaning up some old fuel tanks from the 1950's and found one that has some purple gas in it. One of the guys ran it in his pieced together chevy that he had.....that 350 supposedly ran...real good on it.

You can run high octane avgas in a car, but generally speaking it will produce slightly less power. The higher the octane rating the lower the BTU output. Your best performance comes from running a octane level just high enough to prevent preignition and no higher.

Tod
 
rkmcswain
Posts: 206
Joined: Tue Dec 12, 2000 10:35 pm

RE: Lack Of High Octane Avgas

Tue Feb 21, 2006 4:05 am

Nice explanation Tod.

I don't know much about aircraft piston engine fuel requirements, but 15 years ago I knew a guy with a jet drive boat. He ran a Chevy big block (468 cu.in) with ±13:1 compression. We used to go fill up at a local airstrip. I want to say it was about 108 octane, and even at that time, it was US$3.00/gallon. There would always be some kids there filling up a 5 gallon can for their "street hot rod" -- little did they know some 93 octane (@ US$0.95/gallon) would have probably been good enough.
 
A342
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RE: Lack Of High Octane Avgas

Tue Feb 21, 2006 4:38 am

On www.worldaerodata.com some airports are listed which have 145 octane avgas available, and others with 130 and 115. But I´ve also seen one with 73 octane avgas. Which engine could be properly run on this fuel ?
Exceptions confirm the rule.
 
L-188
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Joined: Wed Jul 07, 1999 11:27 am

RE: Lack Of High Octane Avgas

Tue Feb 21, 2006 4:41 am

Quoting A342 (Reply 19):
But I´ve also seen one with 73 octane avgas

No clue. What airport was it?

I know the german war machine ran mainly on 92 octane.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
 
A342
Posts: 4017
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RE: Lack Of High Octane Avgas

Tue Feb 21, 2006 5:43 am

Quoting L-188 (Reply 20):
Quoting A342 (Reply 19):
But I´ve also seen one with 73 octane avgas

No clue. What airport was it?

It´s TMS, Sao Tomé. Both extremes are available there, 145 as well as 73 octane avgas. Here´s the link:

http://www.worldaerodata.com/wad.cgi?id=TP57651
Exceptions confirm the rule.
 
Pope
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RE: Lack Of High Octane Avgas

Tue Feb 21, 2006 7:24 am

Quoting Buzz (Reply 13):
Alcohol is good for cars, but a lot of the aircraft hoses / seals soften in alcohol.

Alcohol based fuels also have a big problem in cold temperatures. They tend to accumulate a lot of water and icing becomes an issue.
Hypocrisy. It's the new black for liberals.
 
MrChips
Posts: 933
Joined: Wed Mar 30, 2005 2:56 pm

RE: Lack Of High Octane Avgas

Tue Feb 21, 2006 8:12 am

I think the biggest issue with alcohol in aviation fuel is the high vapour pressure of ethanol, in turn causing a huge increase in the potential for carburetor icing or vapour lock (in FI engines).

Even mogas (with a higher vapour pressure than avgas) will increase the likelihood of both of these events.
Time...to un-pimp...ze auto!
 
vc10
Posts: 1339
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RE: Lack Of High Octane Avgas

Tue Feb 21, 2006 8:49 am

The Wright 3350 engine [ non PRT ] as used on the Constellations up to and including the 749 variant were actually initially rated using 100 octane fuel , not necessarily low lead though, so all they do is slightly alter the ignition timing [set on the engine ] to cater for the low lead of fuel now.

Full RICH mixture is used for all powers until cruise power is set so as to avoid detonation or even the risk of it.

In their day they would have a single stage, two speed supercharger, but as the aircraft these days are not pressurized there is no need for the high speed on the supercharger and so this option is now normally locked out., and the option to advance the spark is also locked out as this was needed in high speed blower.

I have to say the 3350 is notorious for spark plug fouling resulting in two procedures on the ground, one to try and keep the plugs clean and the other to clean a plug in a cylinder that has fouled up. The engine analyzer thus became the crew's friend but also sometimes the F/E nightmare as he had to try and interpret all the squibbles on the screen

still be happy little vc10
 
Buzz
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RE: Lack Of High Octane Avgas

Thu Feb 23, 2006 10:34 am

Hi VC-10, Buzz here. I realize that most people won't need high blower on their big radial engines. But there's a problem to putting a bolt in the linkage so she stays in low blower. About 10 years ago in a Lockheed Harpoon we had a supercharger form enough sludge to partially shift into high blower at takeoff power. There was a noisy backfire (2800 cubic inch size belch) and the engine RPM wound down for a couple seconds - the mixture in the intake had been blown out. Then the engine came back up to takeoff power... we recovered from heart stoppage and flew the pattern looking for things amiss.
Anyway, if you regularly cycle the supercharger clutch you don't have a sludge problem there. Oh yes, the owner did not want the modern AD oil in his engines.

And to answer the question about who can use 73 octane Avgas, the little flat engines can: Think of Aeronca Champs, Piper Cubs, Luscome... airplanes with an A-65 Continental. I tell people that i get a lot of G.P.H. in those airplanes: grins per hour.

g'nite
 
MissedApproach
Posts: 678
Joined: Thu Oct 14, 2004 10:12 am

RE: Lack Of High Octane Avgas

Thu Feb 23, 2006 12:09 pm

Quoting 2H4 (Reply 14):
I've always wanted to roll up to an FBO and tell them I need mo' gas

Oh, that reminds me of a question I occasionally ask co-workers, but I've never gotten an answer. I have seen some refuelling trucks labelled MO GAS & other marked ME GAS. What is the difference?
 Confused
Can you hear me now?
 
KELPkid
Posts: 5247
Joined: Wed Nov 02, 2005 5:33 am

RE: Lack Of High Octane Avgas

Fri Feb 24, 2006 4:41 am

Quoting Buzz (Reply 25):
Oh yes, the owner did not want the modern AD oil in his engines.

Can modern AD oil even be purchased by the gallon?  Wink I worked at an FBO that had some radial engine oil on hand (Aeroshell), and it was sold in 1-gallon bottles...the only AD oil we had was sold by the quart, as it was intended for use in flat engines.
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deltagator
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RE: Lack Of High Octane Avgas

Fri Feb 24, 2006 4:56 am

Quoting 2H4 (Reply 6):
ado82 (Reply 5):
NASCAR runs on gasoline still.

...And here I thought those things ran on coal.

IIRC not only do they run on gas/petrol but it is the old Leaded variety. When I lived in Hunstville, AL (not exactly a hillbilly town but merely an outcropping of rocket scientists surround by rednecks) quite a few of the gas stations would have Regular, Mid-Grade, Premium, and Racing Gas. The racing gas was well over 100 octane.
"If you can't delight in the misery of others then you don't deserve to be a college football fan."
 
vc10
Posts: 1339
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RE: Lack Of High Octane Avgas

Fri Feb 24, 2006 7:16 am

Buzz, Those old radials often had a mind of their own, but never experienced anything like you, but we did use detergent oil all the time, and not only that those 3350s used oil so quickly that it did not have time to sludge up  Smile

little vc10
 
L-188
Posts: 29874
Joined: Wed Jul 07, 1999 11:27 am

RE: Lack Of High Octane Avgas

Fri Feb 24, 2006 2:03 pm

Quoting KELPkid (Reply 27):
I worked at an FBO that had some radial engine oil on hand (Aeroshell), and it was sold in 1-gallon bottles

The only time I have seen Radial engine oil....god I can't remember the weight. It came in a 55 gallon drum and the mechanic had to fill the DC-3 oil tanks from a 5 gallon jerry can that he filled from it.

It took several trips.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.

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