Andrew Sarangan wrote:

Rule of thumb for mountain flying is to be *at least* 10% under
the max weight. For my cherokee (that tops out at 2400) that
means absolutely no more than 2160. As a rule, during the summer
I try to keep it under 2100 (thank you, density altitude)

No one will fault you for keeping 10% under gross, but I don't think
that is really necessary. Most runways in the mountains are plenty
long for a 172 or cherokee. If you look up the performance data and
add 20% for pilot and aircraft performance, there will not be many
runways that are shorter. After all, if a runway is too small for a
172, how many other aircraft can really use that runway?

I'm guessing that it's not the runway that's Blanche's limiting factor. I
do not fly in the mountains, but I often do fly my Warrior II up around
10,000 ft to get above the weather and the turbulence, not to mention some
of the bozos flying pretty-much randomly down at the lower altitudes.

Once I get above 6,000 ft or so and am loaded close to my maximum gross
weight, especially on a warm afternoon with lots of thermal activity, my
Warrior's climb becomes unpredictable. On *average*, I still get the climb
rate published in the POH, but sometimes a downdraft will overwhelm me for a
few seconds or even a few minutes, and I am unable to climb or even to
maintain altitude; other times, I'll shoot up like a rocket when I hit an
updraft.

That kind of unpredictability does me no harm when the closest obstacle is
many thousands of feet below me, but I can see how it would be lot scarier
crossing mountain ridges, especially with the stronger downdrafts from
mountain waves, etc. Flying a bit under gross, at least in a
normally-aspirated 160 hp or 180 hp plane, should give you much more of a
fighting chance in a downdraft at high altitude.


All the best,


David