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Wolfgang,
Interesting.
In real life and with my power set at a guess of zero thrust, the AOA shows
a best glide of about 106 KIAS. That is 1.767 NM/minute or 10734
feet/minute.
With my prop in cruise pitch the descent rate was about 1500 feet/min or a
glide ratio of 7:1 - drat.
With my prop in coarse pitch, the descent rate drops to about 500 ft/min or
a glide ratio of 21:1 - ooh.....
You are right in that drag is everything. Even small flat plate drag
requires power cubed for overcoming parasitic drag squared. Best glide
speed is at max lift/drag where the induced drag and parasitic drag curves
intersect. Induced drag increasing as speed is reduced and parasitic drag
increasing as speed increases.
Scott Krueger
IO 320
In a message dated 6/25/2010 5:30:14 P.M. Central Daylight Time,
Wolfgang@MiCom.net writes:
Clean up the airframe so it can get a glide ratio of 15:1 at 300mph and
you can keep the same motor and fuel consumption.
The numbers below come out to a glide ratio of just better
than 10:1
Wolfgang
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06/22/10 I was flying from Detroit to Ft
Lauderdale at 11,000. With nothing else to do, I thought that I would
take a few measurements.
Condition LOP Lo ROP Hi
---------
-------- ---------
11,000 IA 2,350RPM 2,700 RPM
13,000 DA 19.3"MP
19.8"MP
30.08 "Hg 6.0 GPH 8.6 GPH
12°C temp 139 kts IAS 152 kts
IAS
35°F dewpt? 168 kts TAS 183 kts TAS
1,670 lbs
For a 43%
increase in fuel, a 9% increase in airspeed doesn't sound like much.
However, 183 kts airspeed at 13,000 ft density altitude, no matter how
you do it, is great.
The LOP reading at .435 BSFC comes out to HP
= 36 * 6 * .435 = 94.0 HP or 94.0 / 160 = 59% power.
Comments
appreciated.
Lorn |
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