REFLECTOR: Takeoff roll - fuel burn

[Douglas Holub]

Just got back from a 260 nm round trip. Here's some real-world data points for reference: 2.3 hrs on the Hobbs including about 15 minutes total taxi time at both airports, 14 total gallons of fuel consumed. Cruising at 4500 feet lean of peak and winds weren't much of a factor. Two passengers in front and 40 lbs of baggage in back. 

Doug Holub
N2980W
  ----- Original Message ----- 
  From: Al Gietzen 
  To: reflector 
  Sent: Friday, May 22, 2009 1:47 AM
  Subject: REFLECTOR: Takeoff roll - fuel burn


  Here's a bit of data from today's measurements.

  The question came up here awhile back about fuel economy vs CG.  I did flights today in my SE RG with CG at 120", total weight about 2060; and at 116", total weight about 2270.  The CG was shifted by adding a person in the right seat. Surprising; within the accuracy of the measurements, both cases were the same: 160 KTAS burning 9.5 gph at 2500 rpm on a fixed pitch prop (rotary 20B, lean cruise). At pattern speed of about 100 KIAS I noted the heavier, forward CG took more power; but I didn't take any data.



  Takeoff roll - 85F; 1400' field elevation, roughly 8-10kt wind component down the runway, fixed pitch cruise prop.



  Weight - 2100; CG - 120"; about 1630 ft

  Weight - 2300; CG - 120"; about 1730 ft

  Weight - 2300; CG - 116"; about 2300 ft



  These are all single run measurements, taken by spotting relative to taxiway exits and edge lights, and taken from a rolling start - rolling on to the runway, getting it straight and adding power. Moving the CG forward made a more dramatic difference than adding weight, and I didn't like the way it handled at pattern speed, or landing.



  The first case above was repeated using so-called 'Short field takeoff' procedure - getting lined up near the end of the runway, and applying power while holding brakes; then release.  Takeoff roll was the same as the rolling start. My rotary spools up very quickly when I push in the throttle; things may be a bit different with a Lyc.



  Al







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