Originally Posted by IO540
Flying any distance without an accurate fuel flow figure always struck me as highly dodgy, but it is normal in GA to fill the tanks to a certain level, and depart, assuming a certain fuel flow rate which has never actually been checked...
Not necessarily dodgy, just a little more limiting than necessary; take a very conservative fuel burn figure, and keep good reserves. I also tend to dip before and after, so I have an idea what it burns flown the way I fly.
Originally Posted by Maoraigh1
"The POH for the aircraft, and the Piper method of leaning (a PA28) for best economy was to push the throttle to max (firewall) and set the RPM using the mixture. This sounds a litttle crazy, but the proof was there! The economy was great."
Were there any other requirements/details for this method?
Can anyone explain the theory for an ignorant PPL such as me?
(I've used the EGT and "rough and back off" methods.)
Search for LOP (lean of peak) and you'll get to fill your boots. Especially look on avweb (pelican's perch) for some good articles. I'm a little suprised (sceptical?) that it'd be in the POH. Every PA28 I've flown had conventional leaning in the POH, so it's not necessarily the 'Piper' way - it may have been an amendment for that particular a/c?
In short it's (theoretically) possible to throttle the engine by reducing fuel as well as reducing air. Problem for 99% of a/c is that the fuel flows are not well enough matched, and one cyl starts to lean cut before the others are fully lean, which is where the 'rough and back off' method comes from. With 'GAMIjectors' and all the other associated setup, the flows for each cylinder are balanced and you can. Would be very suprised to find an 'out of the box' PA28 that would run LOP.
I think barrow makes a very good point about doing it slowly. First time I leaned I cut the engine completely, and stopped messing with it for a long while. With time I learned a more patient approach
