Tuesday, December 02, 2008


I did another 2 hours in MTW today. It was hot. 36'C on the ground. I
was soaked in sweat before I got into the air, once clear of airspace I
enjoyed a little while at 4000ft where the outside air was a relatively
cool 18'C. I got the aircraft trimmed at 2500RPM and 4000ft indicated
and then got the gps to average the ground speed over a 2 minute run, I
spent 2 mins going first South, then West, then East, then North and at
the end had accurate average speeds for the 2 mins in each direction.
When I got home I worked out that the density altitude was over 5000ft
and 2500RPMs equates to approx 72.5% throttle. The result of the timed
runs was a 104knot average speed, this was actually pretty close to what
the ASI was showing me after I dialled in the height and outside air temp.
The book says I should be doing 108knots in this configuration, so I am
within 5% after 30 years, nothing to complain about there.
With the aircraft leaned correctly 2500RPM burns 28 litres per hour of
fuel, this equates to 14.6 litres per hundred kilometres at a ground
speed (assuming NIL wind) of 191km/h and gives a max range of 5 Hours 40
Mins plus a 45 Min reserve or 1073km or 580nm.

I spent another hour doing unusual circuits at Murray Field and then
30mins of PFL practice before returning to Jandakot.

No comments: