Re: Power = f(t) ?

[jdouglas@mitre.org (jason douglas)]

>Universal, not peculiar to piston engines (ask any Vietnam era chopper
>jock).  Hot humid air contains less oxygen per cubic unit of volume.
>Less oxygen results in less energy form combustion.  Cooler air is more
>dense, contains more oxygen, gives more energy.  Purpose of intercooler
>is to make intake air cooler.

Here is a possibly apocryphal story to illustrate the point.  I knew a
military officer who flew  aircraft from strange locations.  For a few weeks
he flew out of Djbouti (sp?) in the middle eas, an extremely hot place.  The
runway there was, according to the story, originally of concrete, but had
been extended with asphalt.  One day an Indian 747 attempted to take off
with a rather full load.  Because it is so hot in Djbouti, he had reduced
power and reduced lift (density affects the operation of the wings too).  In
other words, he needed more speed for take off and he had reduced power for
achieving it..  Well, he got it off the ground and then, at low altitude,
crossed from the old end of the runway to the asphalt part.  The higher
temperature over the blacktop further reduced lift and power and the plane
settled back down on the runway hard enough to blow out  a couple tires.
Nevertheless, the pilot apparently had the right stuff.  He got it back into
the air before the end of the asphalt and continued onto his destination.

Jason Douglas