It’s easy enough to adapt it to
your airframe by going up and measuring the fuel burn (read off the EM2) for a
few different airspeeds to plug into column B. I did a similar thing by
expanding on the simple spreadsheet Ernest posted some time back. It is
interesting to take the data down to a low enough speed where you see a minimum
cost/mile – the speed below which the cost increases. For my Velocity 20B the minimum cost/mile
(no wind) is at about 130 KTS – a fairly broad minimum so not much higher
at 140-145, but becomes more significant going up from there.
But what does it really mean? You
have to figure out the cost/min saved, and decide what value you put on your
time. If I cruise 160 KTAS vs 170 I find (gas at $3.00/Ga) that saves
about 40 cents for each minute of additional flying time. On a 4 hour
x-country it takes 15 minutes longer and costs about $6.00 less – out of
about $125 fuel bill. When I’m up there just for the joy of flying,
or on a short trip; yeah, go slow – but on a long trip – eh, I
think I’ll go 170 – especially if I can get mogas for $2.00.
It’s all fun.
Al G
-----Original Message-----
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Mark Steitle
Sent: Wednesday, November 26, 2008
1:42 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Fuel Burn
Spreadsheet
The list has been too quiet lately, so I thought I
would post this for the group, but especially for Ed and Tracy. The
spreadsheet was created by Gary Casey, a Lancair driver, to calculate the
fuel/cost penalty related to going fast vs. a little slower, and allows you
to see the difference in fuel burn with specific headwinds and
tailwinds. Gary has graciously permitted me post it on the Fly
Rotary list. Since Tracy has stated on a number of occasions that he is a
"thrifty" pilot, I thought he might enjoy plugging some numbers into
the spreadsheet and seeing how much he is saving. The formulas are based
on a Mooney airframe, so keep that in mind.