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  #11  
Old 09-14-2020, 10:48 AM
Vans101 Vans101 is offline
 
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I am about to go up and do this flight test protocol and I want to verify my Calibrated Airspeed and pitot and static system.

So I get the part about flying three or four headings at a constant altitude and power setting and then letting my EFIS record the data.

Does anyone have the spreadsheet that has blank fields for data that needs to be acquired and I ask because the PEC spreadsheet that the Test Pilot School is already filled out so I was looking for something that made the data points obvious.

Also if you perform this test protocol at only one altitude and only one airspeed then there could be significant static port location errors based on different IAS due to the the different pitch attitudes and or boundary layer turbulence from high speed to low speed so the questions is...I presume you want to do this test at the same altitude but at a number of different IAS from VS+5 to whatever the airplane can maintain with max power in level flight.

Would it be prudent to do this test protocol at a number of different altitudes as well or at least 1000 MSL and then 15000 MSL so as to determine if the altimeter indication is programmed correctly.

Thanks again for your help
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  #12  
Old 09-14-2020, 01:35 PM
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rv8ch rv8ch is offline
 
Join Date: Feb 2005
Location: LSGY
Posts: 3,208
Default just math

One thing that's not clear to me, it seems like the EFIS manufacturers are missing an opportunity. They have all the data to figure out if the IAS is accurate or not - why don't they just figure this out for us?

Either manually calibrate it, by telling us to fly a heading and altitude and airspeed, or just gradually figure it out based on the reams of data they have.

Am I missing something?

BTW, here's a sample spreadsheet that might be helpful:

http://www.lightaircraftassociation....%20Method.xlsx

and more:

http://www.lightaircraftassociation....t_testing.html
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  #13  
Old 09-14-2020, 11:00 PM
krwalsh krwalsh is offline
 
Join Date: Nov 2009
Location: San Francisco, CA
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Default GPS-PEC

Quote:
Originally Posted by Vans101 View Post
Does anyone have the spreadsheet that has blank fields for data that needs to be acquired and I ask because the PEC spreadsheet that the Test Pilot School is already filled out so I was looking for something that made the data points obvious.

Also if you perform this test protocol at only one altitude and only one airspeed then there could be significant static port location errors based on different IAS due to the the different pitch attitudes and or boundary layer turbulence from high speed to low speed so the questions is...I presume you want to do this test at the same altitude but at a number of different IAS from VS+5 to whatever the airplane can maintain with max power in level flight.
The GPS-PEC from NTPS is basically the correct way to do this. I have a version of it I modified to only have the 4-leg version, that I have posted here:

https://drive.google.com/file/d/1x1H...ew?usp=sharing

You can save a copy locally, but you still have to fill it out and fly it. Each test point is a different KTAS point, so record all of the pertinent information (temperature, altitude, indicated airspeed, barometer setting, etc)

Yes, in general this should be flown at a range of altitudes to verify the data. Essentially what you are looking for is "is my static port influenced by airflows at certain speeds or angles of attack and giving me errors?" I will hazard a guess that most people never even bother to determine their pitot-static error at any speed, much less a range. But I found it very informative to fly from as near stall as I could to WOT at three different altitudes (~1000 ft, ~8000ft, and 12,000). What I found was my error at stall at any altitude was nearly zero. My error at WOT was ~13 knots optimistic (displayed 180 KTAS, actual 167). I've been adding steps to my pitot ports since then trying to dial it it. Getting closer, but still not perfect.
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  #14  
Old 09-15-2020, 12:44 AM
BobTurner BobTurner is offline
 
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Location: Livermore, CA
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Heading or track? I donít know. You can write formulas (different formulas) for either. But Iím with Ed. One source of error for all of these methods is the assumption that the wind is constant. The quickest method (Edís) minimizes the total time, so it makes it more likely the wind wonít change. Just make a very gradual turn, monitoring ground speed. Note the heading (it should match the ground track) where the ground speed is maximum. Fly that heading, note gps ground speed. Turn 180 deg and repeat. Average the two ground speeds, thatís your TAS. Use an on-line calculator, or an electronic one, or an E6B, feed in TAS, pressure alt and temp, solve for IAS. Compare to your airspeed indicator.
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  #15  
Old 09-15-2020, 08:43 AM
krwalsh krwalsh is offline
 
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Quote:
Originally Posted by BobTurner View Post
Heading or track?
Doug Grayís method and the math in the provided GPS-PEC specify flying a constant ground track.
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