747-400 range performance

[jlstrum]

According to online sources, a 747-400 should burn about 20,000 lbs of fuel/hour at maximum range cruise of Mach 0.80 at 35,000 feet.  Using those parameters in FS2002, I get less than 8000 lbs/hour.  I was able to complete an unrefueled around-the-world flight (49 hours!), which the real bird would certainly never do.  Is there a patch for this anomaly?

[Whiskey_Zulu]

I've also noticed that the thing seemed to have an excessive range, but I never tried to fly around the world in it!  I was also able to fly the default Lear 45 from Bermuda to Malta.  The generic turbofan engine model that MS uses seems to be too fuel-efficient to me.  It also seems the same even in CFS3.

I don't know of any specific patches, but a Quik & EZ thing you might try is open the aircraft/747_400/aircraft.cfg file with Notepad, find the "fuel_flow_scalar= 1.000" field, and change it to read "fuel_flow_scalar= 2.5", since 20k/8k = 2.5.  This will make the aircraft burn 2.5 times the amount of fuel as the MS flight model says it should.

I think it is excessive that the MS engine model is off on fuel burn by a factor of 2.5.  How could it be so far off?  It's not like we're trying to model some low-bypass military turbofan, this is exactly the sort of engine the sim should model quite well!

[jlstrum]

I've found that at higher power settings, the FS 747-400 burns considerably more fuel, maybe even close to 'real-world'.  

Thanks for your message.

Jim

[Whiskey_Zulu]

What settings would that be?  I was doing Mach .85 at 35,000 in the 747-400 and burning only 7,200 # per hour.

[jlstrum]

I derived w/ some 'pounds of jet fuel-per-nautical mile' numbers.  With a heavy fuel load (several hours into a really long flight), I got 31.8 lbs/mile at 491 kts. groundspeed (off the GPS) at Mach .85 and 35,000 ft.  At Mach .90 and 20,000 (quite low, I realize), it was 101.3 lbs/mile at 553 kts.

What do you think?

Jim

[Whiskey_Zulu]

I didn't see any reference to what #/NM numbers are typical for the 747 when I did a search on the web.  However, I did see #/hr figures which were close to what you said in your first post, 20,000 #/hr.  Basically, I think you were right in your first post.

I don't think a 747 would ever cruise at Mach .9 and 20k feet.  Fuel economy is vital for airlines.  I don't think a 747 would every cruise at Mach .9 at any altitude.

And one more thing, there is absolutely no way a 747 could fly around the world without refueling (it took Rutan's Voyager to do that), so I think the fact that you did so pretty much clinches that the fuel economy of the plane is far too high in FS2002.

[jlstrum]

747-400s are, I believe, the fastest subsonic airliners in service today, which is remarkable considering the basic design was created in the 60s!  I also understand that they do indeed cruise at Mach 0.9 or faster on occasion, though certainly with a fuelburn penalty.

Jim

[cwloew]

Please forgive my ignorance, but it seemed to me that the Deault 747 was not a very good aircraft.

If I use the numbers for instance from the "Create a Flight" utility within FS 2K2, it is not very cost effective to send the aircraft out of the US.

Fuel capacity, time in flight, fuel needed for flight (without the astro-science mathmatics, all seem to indicate that using a Triple Seven 200 to Europe from Boston (as my example) is actually more cost efficient than using the Jumbo Jet.

Please don't get me wrong here I happen to like the Jumbo, but as a manager of a VA I have a problem with scheduling the trans pacific or trans atlantic flights with her.

I am always open for discussion, if I'm wrong, please show me the error of my ways :-)

[Whiskey_Zulu]

Do you take into account that a 747 carries more passengers than a 777?  You get increased efficiency due to economy of scale.