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01-01-2013, 10:05 AM
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Join Date: Nov 2005
Location: Asheville, NC
Posts: 2,692
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Quote:
Originally Posted by curtis
...there is no indication of negative vertical speed?
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Not always. For example, I was flying a couple of days ago in some strong mountain waves on the east coast (and a quartering headwind gale  ). There were multiple occations where the autopilot pitched up and slowed the craft to around 120KIAS just to keep the VSI on zero. As you fellows know, this speed should have equated to better than 1000 FPM climb.
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Bill Pendergrass
ME/AE '82
RV-7A: Flying since April 15, 2012. 850 hrs
YIO-360-M1B, mags, CS, GRT EX and WS H1s & A/P, Navworx
Unpainted, polished....kinda'... Eyeballin' vinyl really hard.
Yeah. The boss got a Silhouette Cameo 4 Xmas 2019.
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01-02-2013, 03:35 PM
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Join Date: Mar 2008
Location: Albany.NY
Posts: 5
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The VSI on the top shows an ever so small climb and the VSI on the bottom shows a very small descent. Looks like a moving airmass to me.
Why are both tanks full at 24+ in both pictures?
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01-02-2013, 06:37 PM
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Join Date: Apr 2007
Location: Lexington Park, MD
Posts: 14
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I don't see much of a difference from an airspeed perspective. If you take your trusty E6B and use IAS and Dens Alt to convert to TAS you get a number in the ballpark of the TAS shown on each of the screens. In this case the TAS calculated and the TAS shown are different by 4 to 5 knots which is probably position error or some other errors (e.g. OAT) built up in the calculations of the EFIS.
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01-02-2013, 06:57 PM
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fugio ergo sum
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Join Date: Apr 2006
Location: Carlsbad, NM
Posts: 1,912
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I think there are some exceptions (advection fog?), but a meteorologist I know made a flat declaration this year at a weather spotter meeting that all clouds are formed by rising air. Even if it is just "almost" always the case, that is reason enough for higher speed in clouds.
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Larry Pardue
Carlsbad, NM
RV-6 N441LP Flying
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01-02-2013, 07:06 PM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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Except, it was slower in the clouds. If the OAT was colder I would have guessed ice. But I'll go with the clear air updraft theory for now. Certainly is a difference in nose attitude.
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01-03-2013, 01:44 AM
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Join Date: Nov 2010
Location: Australia
Posts: 53
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I think what has happened here is that you have identified one aspect of being in a cloud (high moisture content) and assumed it is the significant cause of the performance difference.
As others have noted, the velocity vector is on the horizon and the vsi is reading zero. There is a difference in attitude, with the lower nose attitude associated with higher airspeed. This would indicate that the aircraft is moving through an air mass that is rising. Both wave action and convection can be associated with cloud formation and both of these effects would be consistent with the performance difference noted.
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01-03-2013, 06:19 AM
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Join Date: Nov 2010
Location: Monroe, La
Posts: 39
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Looks like you picked up some more tail wind
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01-03-2013, 06:51 AM
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Join Date: Feb 2009
Location: Brooksville
Posts: 282
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Some good discussion here! Great to hear your ideas.
I think like some have said there is some variation in attitude due to atmospheric conditions that is changing TAS but will take some more testing to confirm.
however, I have noticed a drop in air speed almost every time I have been IMC while this particular flight was (probably) influenced somewhat by the atmospheric conditions, I still am seeing a drop in airspeed when in the clouds accross the board.
Does anyone else that flys IMC out there see this?
Another thing that happens when the air is saturated with water is there is work lost in the engine due to it having to evaporate the moisture. I have no idea how much intake air humidity has to do with HP output.
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Weasel
RV-4 715hr Sold 
RV-10 "School Bus"
I have changed my User Name to the correct spelling as it became availible. Please direct all correspondence to Weasel
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01-03-2013, 06:55 AM
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Join Date: Feb 2009
Location: Brooksville
Posts: 282
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Quote:
Originally Posted by rocketbob
Unrelated to this topic but man all that stuff on the left makes my head hurt. You'd think that some of the EFIS manufacturers could use UI-design inspired by an iPhone.
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Sorry Bob, That is due to me trying to cram all that I like to monitor into the 20% engine monitor section of the screen.
The Skyview engine monitor section is fully costomizable to what ever you like with may widgets and size/arrangement to your liking. my bad 
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Weasel
RV-4 715hr Sold 
RV-10 "School Bus"
I have changed my User Name to the correct spelling as it became availible. Please direct all correspondence to Weasel
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01-03-2013, 08:45 AM
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Join Date: Oct 2005
Location: 08A
Posts: 9,500
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Quote:
Originally Posted by Wesael
Another thing that happens when the air is saturated with water is there is work lost in the engine due to it having to evaporate the moisture. I have no idea how much intake air humidity has to do with HP output.
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Ahhhhh....power loss. Hadn't thought of that. Good point. Water vapor changes inlet air density, fuel/air ratio, and thermal efficiency.
The equations for each are found in Taylor's " Internal Combustion.."
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Dan Horton
RV-8 SS
Barrett IO-390
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