Marv,

 

Your curiosity is my curiosity. 

 

I flew today at a gross weight of 1600 pounds with the CG at 24.9 in mild turbulence at 3200 feet (3150 p-alt) and a baro setting of 29.93, temperature of 50F.  The idea was to fly at L/D max and 25% below that (max endurance) at –7, 0 and + 7 degrees of flap.  Additionally, I wanted to look at different rpm/map combinations to see if I could save more fuel.  I was not able to complete all of these conditions because only a nut would do so.  Thus:

 

 Reflex      -0-      down 14* from normal flight

-00007  000000 +00007     Flap settings

    5.8        4.2         5.6       AOA

    2.6        1.2           .5(-?)  Longeron angle

  1880     1800      1800      RPM

   20.5      18.6       18.6      MAP

   50%      42%       42%     % power via formula

   3.9        3.5          3.5       GPH

   118       108          98       KIAS at max L/D or one green bar more

   123       111                     KTAS

 

The mixture was set about 30F LOP.  At the specific rate of 3.9 gph, I could fly for 10 hours with a 1 hr reserve (43 gal tanks).  In a no wind (hah!) hallucinatory state, I could cover 1230 NM (10*123).  However, we must remember that weight affects AOA so the fuel burn would alter the range.  I could stay in the air 1.25 additional hours at the 3.5 gph setting (111 KTAS) and could reach 1248 NM.

 

Note that the power settings were weird.  Exotic vibration (maybe from prop pulses to the tail?) at such low rpm and cyl head temps running between 270 to 290 made further power reductions unwanted.  Reduction of airspeeds to 75% of those listed above are not recommended whilst in turbulence with one’s head in the cockpit.  I just couldn’t wrap my mind around trying to advance the MAP and further reducing the RPM to see what would happen at other means to the same power.  Maybe some other person would be willing to try.