terry wrote:
I am supposed to
set the wt limit purely on the pressure altitude.
terry


No.. You calculate (or obtain) density altitude for your given condition
and day, then refer to THAT altitude on the pressure charts for
performance.

Density altitude can come from your airspeed indicator (if it has a
bezel ring), your GPS (if you input the other data or have an ADC), your
Dynon (or other glass cockpit AHRS if available) or your trusty E6B. You
might even just tune to ATIS/AWOS/ASOS to get it.

If your density altitude is 4000 feet, your performance charts for 4000
(Std day) apply. If your density altitude is 5000 feet, the chart or
interpolation for 5000 ft pressure alt/standard day apply.

performance at 4000 ft density altitude on a standard day is the same as
performance at 4000 ft density altitude on a nonstandard day (presumably
somewhere else). Make sense?

And 4000 ft density alt on a standard day just also happens to be
Pressure altitude.