Mailing List lml@lancaironline.net Message #67438
From: <Sky2high@aol.com>
Subject: Re: [LML] LOP power
Date: Wed, 16 Oct 2013 17:13:01 -0400 (EDT)
To: <lml@lancaironline.net>
Chris,
 
Below are a couple of old emails with some data.  I know there are more - I just have no idea what the topic was....................
 

Scott

 

====================

 

Efficient little suckers, aren't they?

 

I don't have any recent precisely comparable numbers but here are some from my April trip to SNF (actually, the return, 30 minutes NW of KGAD):

 

WOT, 10550 MSL, 11360 Dalt, 10C, 21.5" MAP, 2500 RPM, ~100F ROP, 8.3 GPH, 27 DBTDC === 168 KIAS, 198 KTAS, 193 Kts Ground Speed. I was in a hurry to get home.

 

The previous April on my way to Austin, TX (to 3R9 from KARR, I did not want to stop for fuel) and over Lebanon, MO:

 

WOT, 8500 MSL, 8240 Dalt, 2C, 23.3" MAP, 2480 RPM, ~20-30F LOP, 6.9 GPH, timing not recorded === 171 KIAS, 193 KTAS, 208 Kts Ground Speed.  Block to Block 4 hr 25 min and 31 gallons used (avg 7.05 GPH over 826 NM and 30.7 SM per Gallon).  Wow!

 

Scott Krueger

IO 320

TAS is from my on board air data computer.

 

In a message dated 6/25/2010 1:00:17 P.M. Central Daylight Time, lorn@dynacomm.us writes:

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

--
Lorn H. 'Feathers' Olsen, MAA, ASMEL, ASES, Comm, Inst
DynaComm, Corp., 248-345-0500, mailto:lorn@dynacomm.us
LNC2, FB90/92, O-320-D1F, 1,700 hrs, N31161, Y47, SE Michigan


--
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The flight was flown to 3R9 at 8500 MSL, WOT, LOP (eliminated a fuel stop) with the XM radio providing more entertainment than the interruptions from ATC could.  4.3 hours to 3R9 (Lakeway airpark, about 15 west of Austin), covering 951 statute miles and consuming slightly less than 31 gal for 31 mpg at an average GS of over 222 mph (43 gallon max capacity).  My son picked me up for the 30 minute drive to his house.  About 5.8 hours, door-to-door.

 

The next day’s return was similarly conducted under blue skies at 9500 MSL (avg 12 mph headwind instead of the 14 mph tailwind enjoyed on the way down) and, after a nice landing, I got the luggage from the carousel (cockpit), pitched it in the car and was on my way home in  amoment (no bugs to clean off yet!).

 

For those interested in stats, heading north around Fort Smith, AR:

 

@ 9500 MSL (baro = 29.92, 10C OAT), 10600 density altitude.  166 KIAS, 193 KTAS, 186 Kt Ground Speed.  WOT, 22” MAP, 2490 RPM, 27 Deg BTDC, 6.9 GPH.  CHTs = 320F to 340F and EGTs = 1370F to 1410F with the first to peak running at 30F LOP.

 

I took regular readings, observed certain environmental changes and made adjustments.

 

Maintaining same MSL while baro decreased and as OAT decreased: IAS/TAS increased slightly, Density Altitude decreased, Mixture (fuel flow) increased to keep LOP EGT temp the same.  Also, as speed increased, AOA decreased.  The air mass change was to drier air and as OAT decreased so did the CHTs by as much as 30F (+13C to 0C at altitude, a 23 F spread).

 

The oil cooler air door was adjusted to keep the oil temps between 175F and 180F.

 

On the trip down, as the OAT and density altitude increased, the fuel flow was slightly reduced to keep the LOP EGT the same.  Interesting.

 

I chose to fly LOP to eliminate a fuel stop and even though the FF was maybe 2 gph less than best power, the KTAS was always above 190 Kts.  Try that in a spam-can.

 

===================

In a message dated 10/16/2013 12:05:43 P.M. Central Daylight Time, chris_zavatson@yahoo.com writes:
 
What is the minimum expected power loss between running ROP best power and LOP operation?  I understand the more LOP you are, the lower the power.  I am trying to get some ball park values for performance calcs.
thanks,
Chris Zavatson
N91CZ
360std
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