"Douglas Paterson" wrote in message
. ..
Still getting to know my new baby (1990 TB-20, normally aspirated 250hp
Lycoming IO-540). I imagine my question here must apply to most
non-turbo, non-FADEC pistons (though I gather there's some sort of
altitude compensator on some airplanes' engines?). I live in Colorado,
which means routine high-elevation airport ops.

I'm looking for guidance on proper mixture setting for takeoff & landing
at high-elevation (with correspondingly high DA) fields. What's the best
way to achieve maximum power in these conditions?

The "book" answer, per the POH, of full rich for takeoff and landing is
clearly wrong--indeed, I stalled the engine on my first landing roll-out
back here (I was lean of full rich, but, obviously, not enough!). I'm
looking for some "science" to put behind this, instead of "mmm, about
*there*".... I've been tweaking the mixture for highest rpm during the
run-up (2,000 rpm), then looking for a couple of gph above the book's
climb fuel flow for the existing DA on takeoff roll. That seems to work
OK for takeoff, but, of course, I'm somewhat back to guessing for landing
(especially at a different field or if the DA has significantly changed).
Any suggestions or comments?

FYI, the field I'm basing from is 7,030' elevation, with 9 - 10K' DAs
typical; and we've been to Leadville (LXV)--elevation 9,927', North
America's highest municipal airport & highest paved runway, DA of 11,700'
when we visited. This is far more than just an academic discussion for
me!!

http://www.avweb.com/news/pelican/list.html (Start with #18 and go through
the entire "Engine-Related Columns" series)


--
Matt Barrow
Performance Homes, LLC.
Cheyenne, WY