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Posted on 11/30/2004 10:13:12 AM PST by presidio9
BTTT
Old Fossett doesn't have to worry about collecting any moss on his private parts. :)
,,, he doesn't seem to have any funding problems either.
More power to him!
There are several problems with your numbers which make the amount of additional fuel required much less than an order of magnitude.
The biggest problem is in your choice of the circumference of the earth as the required distance. None of the "around the world" flights have taken place over the equator. In fact most of them have taken place mostly north of 30 degrees. So the actual flight distance will be substantially less than ~24000 mi, probably more like 16 to 18000 miles.
Second, the range you state for a 747 includes a significant amount of fuel reserves per FAA mandates to allow for diversions and wind conditions. Since any "around the world" attempt would be flown from west to east and using the jet stream as much as possible and since this would be an experimental flight, not a passenger flight, no fuel reserves would be required.
Yes, GW would affect the range, but at the end of flight you'll be much lighter than a regular, empty 747, so you'll regain some of that loss. Also, you'd be flying at the maximum altitude that you can reach for the entire flight and at the minimum airspeed (this is another thing that the standard range numbers do not include since it would never be done on a passenger flight due to safety concerns).
Add to that the fact that you would run the engines as lean possible since you wouldn't care about reducing their lifespan (yet another thing not included in the standard range number).
Also, anyone who was serious about attempting this, would go over the airframe and clean it up as much as possible, so it would have significantly less parasitic drag than the average 747.
Add all this up and I think the numbers would be closer to 3 times more gas rather than 10 times. Still a hell of a lot of extra gas and it might not be possible. But I think its a heck of lot closer than you think.
Fuel burn during ascent would be a killer at this higher GW / trim attitude. A diminishing problem as you indicated but bad none the less.
I don't believe there is that high of a knockdown in fuel consumption for jet engines due to durability issues. I don't even see that in turboprops.
But like I said you present a compelling case.
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As you said, I think the GW problem is the biggest issue.
The fuel burn during climb out would definately be brutal. And it would probably need a couple of JATO bottles and using Groom Lake in winter to get off the ground.
I suspect it would also need some kind of dolly, which would fall off at take off, because I doubt the landing gear would support that much weight (or the rolling resistance would be way to high at that weight).
I did find some other specs for the 747-400ER, which also improved on your numbers, but it wasn't clear to me under what conditions those numbers were valid, so I didn't quibble with your numbers. For instance, I found a specs on the Boeing website of over 7000 nautical miles, a cargo weight of just under 200,000 lbs with a gross weight of almost 1,000,000 lbs for the 747-400ER.
So a 747-400ER can do almost 8000 statute miles and the cargo weight is about twice your estimate, so I'm getting close, but I'd still have to load it well above spec.
Heh, I think I might need to change over to an A340-500.
I was just reading Aviation Week and an ad for Airbus said that an A340-500 has made a 9000nm commercial flight from Singapore to NYC flying east to west.
So a commercial flight, chasing the earth's rotation and probably having to fly at crummy altitudes in order to avoid the jet stream, managed to do a 10,000 statute mile flight. I wonder how much fuel he had in reserve.
Actually, I think the 747-400er would probably still be the better choice, because it probably has a higher max GW and max thrust.
I will venture to guess that Rutan's designing/building/test flying of this plane costs magnitudes less money than buying a 747 and then installing tanks and modifying it. Sure, a billionaire is funding the flight but there's no fun in using a 747.
Sorry for the late response...I've been offline for a week and just saw this thread.
That part of the trip over Egypt, Saudi Arabia, S. Iran and S. Afghanistan, Pakistan and India would help keep me awake...to be sure.
Your fuel calcs also don't take into account shutting down two engines once you get to cruising altitudes. Navy ASW pilots do it all the time in a P-3 Orion.
Just a thought ;-)
RE: "Your fuel calcs also don't take into account shutting down two engines once you get to cruising altitudes. Navy ASW pilots do it all the time in a P-3 Orion. "
Actually, I thought of that. But I'm guessing that for at least the first half of flight you'd probably need the thrust from all four engines to lift the huge amount of weight to as high an altitude as possible (for both the reduced drag and to get into the jet stream).
Since it would probably only affect the last half or quarter of the flight, I didn't bother to mention it (also the post was getting pretty long without it).
RE: "I will venture to guess that Rutan's designing/building/test flying of this plane costs magnitudes less money than buying a 747 and then installing tanks and modifying it. Sure, a billionaire is funding the flight but there's no fun in using a 747."
Yeah those are good points and Rutan's forte is his ability to do minimalist designs. Like I said in my original post, I was probably being a spoil sport.
But, if I was the pilot, I'd sure feel a lot safer in a 747 that could do the trip in under 40 hours rather than Rutan's design which will take 70 hours and who's airspeed will need to be carefully monitored (the wing design he uses is very efficient, but the penalty is that the cruise speed is very close to the stall speed).
"since this would be an experimental flight, not a passenger flight, no fuel reserves would be required."
It would be an IFR flight and the fuel reserves would be required.
You must not be a pilot.
Youo can't fly a 747 single pilot either.
It's illegal!
There I was just minding my own business searching for a particular John Kerry article. I typed in one of the keywords I had given it and to my absolute surprise (and delight!), I found that mine wasn't the only "OOPSICRAPPEDMYPANTS" article!!! I am just crying with laughter! I love this sketch and haven't seen it in ages. Thanks for making my morning! And two years ago, at that!
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