"Rolf T. Kappe" wrote in message
...
On Sun, 30 Sep 2007 21:48:14 GMT, "octothorpe"
wrote:


"Zomby Woof" wrote in message
news:0sULi.28297$x%6.23120@pd7urf2no...




42 Tons of air per minute. At that rate it could stay aloft for ~15
minutes. That's assuming a 14.7 to 1 air to fuel ratio.

All of which shows that a TF-39 engine has a lot higher air to fuel
ratio. There is no particular reason for a jet engine to fully
combust the oxygen in the air, which is where that 14.7 figure comes
from. Secondly, the TF-39 has a bypass ratio of 8 to 1, meaning 8
times as much air goes around the hot section as through it, and never
gets combusted at all.
Try
http://www.grc.nasa.gov/WWW/K-12/airplane/ngnsim.html
(especially the CF6 model)
If you play with this, you can see a jet engine at full power could
could have a air fuel ratio of 60. With the 8:1 bypass ratio, the
overall number could be 540. This would give an answer of about nine
hours at full power.

--Rolf

I suspected there would be a problem with the calculation. I completely
forgot about "bypass".
Thank you for the informed answer and the URL. That looks especially
interesting.

--
Tom