---------------------------------------------------------- RV-List Digest Archive --- Total Messages Posted Mon 01/02/12: 8 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:11 AM - Re: Dynon Skyview Airspeed Calibration... (Bubblehead) 2. 06:28 AM - Re: Re: Dynon Skyview Airspeed Calibration... (Linn Walters) 3. 07:39 AM - Re: Dynon Skyview Airspeed Calibration... (Jim Ayers) 4. 09:25 AM - Re: Re: Dynon Skyview Airspeed Calibration... (Kevin Horton) 5. 09:41 AM - Re: Dynon Skyview Airspeed Calibration... (Kevin Horton) 6. 12:42 PM - Re: Dynon Skyview Airspeed Calibration... (Bubblehead) 7. 03:14 PM - Re: Re: Dynon Skyview Airspeed Calibration... (Bob Mills) 8. 03:31 PM - Re: Re: Dynon Skyview Airspeed Calibration... (Kevin Horton) ________________________________ Message 1 _____________________________________ Time: 06:11:03 AM PST US Subject: RV-List: Re: Dynon Skyview Airspeed Calibration... From: "Bubblehead" One big question: Does changing the geometry of the static port change indicated altitude when flying? It seems like if we change the static pressure by applying washers or lips we would change indicated altitude along with IAS. -------- John Keller, TX RV-8 N247TD Read this topic online here: http://forums.matronics.com/viewtopic.php?p=362222#362222 ________________________________ Message 2 _____________________________________ Time: 06:28:30 AM PST US From: Linn Walters Subject: Re: RV-List: Re: Dynon Skyview Airspeed Calibration... On 1/2/2012 9:07 AM, Bubblehead wrote: > --> RV-List message posted by: "Bubblehead" > > One big question: > > Does changing the geometry of the static port change indicated altitude when flying? Yes, it surely could. If the static system isn't truly 'neutral' ..... no pressure or suction on it .... it really messes things up. > It seems like if we change the static pressure by applying washers or lips we would change indicated altitude along with IAS. The reason for the 'washer' or 'rivet head' (whatever you use) is to get the port out of the laminar flow down the fuselage into undisturbed (relatively) air. That makes location pretty important. It also means that port location/thickness/shape/ ....... is the ONLY thing you can change to fix airspeed/altitude errors in flight AFAIK. It also means you need two ports, one on each side to cancel induced errors due to uncoordinated flight. Linn. > > -------- > John > Keller, TX > RV-8 N247TD > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=362222#362222 > > ________________________________ Message 3 _____________________________________ Time: 07:39:05 AM PST US Subject: Re: RV-List: Dynon Skyview Airspeed Calibration... From: Jim Ayers Do you have a test method that we can all use to calibrate the alimeter at cruise speed? The altimeter only has the static system for its input. Calibrating the static vents in cruise conditions for the altimeter could p rovide a correction for airspeed readout errors. Correcting airspeed readouts errors by changing the static vent geometery l eaves your altitude readings at cruise speeds as a total unknown. Jim Ayers -----Original Message----- From: Kevin Horton Sent: Tue, Dec 27, 2011 11:50 am Subject: Re: RV-List: Dynon Skyview Airspeed Calibration... Checking altimeter accuracy against tops of ridge lines only works if the emperature is close to standard temperature. If the temperature differs from standard, the error is about 4 ft per 1000 ft er degree C of difference from standard temperature. E.g., if the top of t he idge line is 2000 ft above the airport where the altimeter setting came fro m, nd the temperature is 15 deg C warmer than standard temperature, the altime ter ill read about 4/1000 * 2000 * 15 = 120 ft lower than the actual altitude .. See: http://bathursted.ccnb.nb.ca/vatcan/fir/moncton/WeeklyTopics/Archives/20040 104/CurrentTopic.html ttp://44rf.com/misc/USAF_AIS_Cold_WX_Altimeter.ppt Kevin Horton On 2011-12-27, at 12:44 , Jim Ayers wrote: > An easy way to check the static side of the airspeed indicator is to use your ltimeter. I flew along a ridge line at cruise speed that has a 2200 feet peak as sho wn n my sectional. I may not have been exactly at the same level. Could have been 10 or 20 f eet ff in hieght. My altimeter read 2,210 feet. So, at that time, my static system was pretty close. Jim Ayers Less Drag Special sn 1 (Modified HR2) -----Original Message----- From: David Maib To: rv-list Sent: Mon, Dec 26, 2011 8:03 pm Subject: Re: RV-List: Dynon Skyview Airspeed Calibration... > Maybe a static port error? Check out some of Kevin Horton's articles in Kitplanes. Static port errors can, and do, cause "fast" errors. IIRC, Kevin says that pitot alignment does not have to be very precise to be pretty accurate. David Maib Rv-10 40559 Flying. On Dec 26, 2011, at 10:39 PM, Matt Dralle wrote: dralle@matronics.com > > > Dear Listers, > > I've been flying the new 10" Dynon Skyview in the RV-6 for a few > weeks now and it seems like the airspeed is reading maybe 10mph > fast. The GS always reads 10mph or more slower than the True > airspeed, no matter which way I fly with respect to the current > wind. Looking through the configuration options on the Skyview, > I'm not seeing parameters to calibrate the airspeed. If the > airspeed were *slow* compared to the GS, I could envision making > adjustments to the Pitot tube to get it in better alignment with > slipstream. But *fast* is a head scratcher. If there's no > electronic configuration parameters to adjust, what do you do? Are > there Pitot line "attenuators" like for RF in coax? ;-) > > Matt > > - > Matt "Red Dawg" Dralle > > RV-8 #82880 N998RV "Ruby Vixen" > http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log > http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log > http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel > Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap... > > RV-6 #20916 N360EM "The Flyer" > http://www.mattsrv6.com - Matt's RV-6 Revitalization Log > Status: 42+ Hours Since Purchase - Upgrades Complete; Now In Full > Flyer Mode > > > > -======================== - -= -- Please Support Your Lists This Month -- -= (And Get Some AWESOME FREE Gifts!) - -= November is the Annual List Fund Raiser. Click on -= the Contribution link below to find out more about -= this year's Terrific Free Incentive Gifts provided -= by: -= -= * AeroElectric www.aeroelectric.com -= * The Builder's Bookstore www.buildersbooks.com -= * HomebuiltHELP www.homebuilthelp.com - -= List Contribution Web Site: - -= --> http://www.matronics.com/contribution - -= Thank you for your generous support! - -= -Matt Dralle, List Admin. - -======================== -= - The RV-List Email Forum - -= Use the Matronics List Features Navigator to browse -= the many List utilities such as List Un/Subscription, -= Archive Search & Download, 7-Day Browse, Chat, FAQ, -= Photoshare, and much much more: - -= --> http://www.matronics.com/Navigator?RV-List - -======================== -= - MATRONICS WEB FORUMS - -= Same great content also available via the Web Forums! - -= --> http://forums.matronics.com - -======================== -= - List Contribution Web Site - -= Thank you for your generous support! -= -Matt Dralle, List Admin. -= --> http://www.matronics.com/contribution -======================== ________________________________ Message 4 _____________________________________ Time: 09:25:40 AM PST US Subject: Re: RV-List: Re: Dynon Skyview Airspeed Calibration... From: Kevin Horton On 2012-01-02, at 09:07 , Bubblehead wrote: > > One big question: > > Does changing the geometry of the static port change indicated altitude when flying? > > It seems like if we change the static pressure by applying washers or lips we would change indicated altitude along with IAS. > > -------- > John =================== If the original IAS error was due to a poorly located or shaped static port (i.e. static system position error), then the original errors would have affected both IAS and altitude indications. In this case the correct fix is whatever it takes to get the static port to sense a pressure that is as close as possible to true ambient pressure. This will correct both the IAS and altitude indications. If the source of the error is static source position error, then any "fix" that only addressed the IAS (such as the adjustments that some EFIS provide) will only correct the IAS. The indicated altitude will still be wrong, and this error could easily be much more than 100 ft. -- Kevin Horton RV-8 Ottawa, Canada http://www.kilohotel.com/rv8 ________________________________ Message 5 _____________________________________ Time: 09:41:13 AM PST US Subject: Re: RV-List: Dynon Skyview Airspeed Calibration... From: Kevin Horton The classical test method that directly compares actual vs indicated altitude is the "tower fly-by". Typically a camera is placed on top of a tower about 100 ft high, with the tower abeam the middle of a long runway. The camera is very accurately aimed, and the geometry of the tower, camera lens, etc is very well known so that the height of the aircraft above the runway can be determined from the images, assuming the aircraft accurately tracks down the runway centreline. The aircraft instrumentation system records the altitude, with a very accurate time stamp. Ground instrumentation records the altitude and OAT at ground level, and the camera images have an accurate time stamp. Post flight analysis is used to determine the actual vs indicated altitude as the aircraft passes by the tower at a range of airspeeds. This is used by some major test centres, but it is not practical for us as it requires too much specialized equipment to achieve reasonable accuracy. The method that is most practical for us is the speed course method (sometimes called ground course method). It assumes that the pitot pressure is accurate, which is a reasonable assumption, and there are no static or pitot leaks, which can be confirmed by ground test. The ASI instrument error must be measured. The TAS is measured using one of several possible methods (GPS data from a four course box pattern is the current best method), and the CAS is back calculated from the TAS, indicated altitude and OAT. The difference between CAS and IAS (corrected for instrument error) must be due to static source position error. More info: http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%2023-8B/$FILE/Final-Part8.pdf http://www.kilohotel.com/rv8/rvlinks/ssec.html Kevin Horton On 2012-01-02, at 10:35 , Jim Ayers wrote: > Do you have a test method that we can all use to calibrate the alimeter at cruise speed? > > The altimeter only has the static system for its input. > > Calibrating the static vents in cruise conditions for the altimeter could provide a correction for airspeed readout errors. > > Correcting airspeed readouts errors by changing the static vent geometery leaves your altitude readings at cruise speeds as a total unknown. > > Jim Ayers > -----Original Message----- > From: Kevin Horton > To: rv-list > Sent: Tue, Dec 27, 2011 11:50 am > Subject: Re: RV-List: Dynon Skyview Airspeed Calibration... > > > > > Checking altimeter accuracy against tops of ridge lines only works if the > temperature is close to standard temperature. > > If the temperature differs from standard, the error is about 4 ft per 1000 ft > per degree C of difference from standard temperature. E.g., if the top of the > ridge line is 2000 ft above the airport where the altimeter setting came from, > and the temperature is 15 deg C warmer than standard temperature, the altimeter > will read about 4/1000 * 2000 * 15 = 120 ft lower than the actual altitude. > > See: > > > http://bathursted.ccnb.nb.ca/vatcan/fir/moncton/WeeklyTopics/Archives/20040104/CurrentTopic.html > http://44rf.com/misc/USAF_AIS_Cold_WX_Altimeter.ppt > > > Kevin Horton > > On 2011-12-27, at 12:44 , Jim Ayers wrote: > > > An easy way to check the static side of the airspeed indicator is to use your > altimeter. > > > > I flew along a ridge line at cruise speed that has a 2200 feet peak as shown > on my sectional. > > > > I may not have been exactly at the same level. Could have been 10 or 20 feet > off in hieght. My altimeter read 2,210 feet. > > So, at that time, my static system was pretty close. > > > > Jim Ayers > > Less Drag Special sn 1 (Modified HR2) > > > > -----Original Message----- > > From: David Maib < > dmaib@mac.com > > > > To: rv-list < > rv-list@matronics.com > > > > Sent: Mon, Dec 26, 2011 8:03 pm > > Subject: Re: RV-List: Dynon Skyview Airspeed Calibration... > > > dmaib@mac.com > > > > > > > > Maybe a static port error? Check out some of Kevin Horton's articles > > in Kitplanes. Static port errors can, and do, cause "fast" errors. > > IIRC, Kevin says that pitot alignment does not have to be very > > precise to be pretty accurate. > > > > David Maib > > Rv-10 40559 > > Flying. > > On Dec 26, 2011, at 10:39 PM, Matt Dralle wrote: > > > > > dralle@matronics.com > > > > > > > > > > Dear Listers, > > > > > > I've been flying the new 10" Dynon Skyview in the RV-6 for a few > > > weeks now and it seems like the airspeed is reading maybe 10mph > > > fast. The GS always reads 10mph or more slower than the True > > > airspeed, no matter which way I fly with respect to the current > > > wind. Looking through the configuration options on the Skyview, > > > I'm not seeing parameters to calibrate the airspeed. If the > > > airspeed were *slow* compared to the GS, I could envision making > > > adjustments to the Pitot tube to get it in better alignment with > > > slipstream. But *fast* is a head scratcher. If there's no > > > electronic configuration parameters to adjust, what do you do? Are > > > there Pitot line "attenuators" like for RF in coax? ;-) > > > > > > Matt > > > > > > - > > > Matt "Red Dawg" Dralle > > > > > > RV-8 #82880 N998RV "Ruby Vixen" > > > > > > http://www.mattsrv8.com > > > - Matt's Complete RV-8 Construction Log > > > > > > http://www.mattsrv8.com/Mishap > > > - Landing Mishap Rebuild Log > > > > > > http://www.youtube.com/MattsRV8 > > > - Matt's RV-8 HDTV YouTube Channel > > > Status: 170+ Hours TTSN - Rebuilding Fuselage After Landing Mishap... > > > > > > RV-6 #20916 N360EM "The Flyer" > > > > > > http://www.mattsrv6.com > > > - Matt's RV-6 Revitalization Log > > > Status: 42+ Hours Since Purchase - Upgrades Complete; Now In Full > > > Flyer Mode > > > > > > > > > > > > > > > _blank>www.aeroelectric.com > /" target=_blank>www.buildersbooks.com > =_blank>www.homebuilthelp.com > blank>http://www.matronics.com/contribution > t=_blank>http://www.matronics.com/Navigator?RV-List > p://forums.matronics.com > blank>http://www.matronics.com/contribution > > > > > > > > http://www.matronics.com/Navigator?RV-List > > http://forums.matronics.com > > http://www.matronics.com/contribution > > > ________________________________ Message 6 _____________________________________ Time: 12:42:20 PM PST US Subject: RV-List: Re: Dynon Skyview Airspeed Calibration... From: "Bubblehead" Kevin, I've been on your site a lot today reading about this. Next weekend if weather permits I will collect a lot of Numbers to plug into your speadsheet to see about IAS and TAS. I suspect the TAS on my Skyview is significantly off because I am getting wind vectors that disagree significantly with forecast winds aloft and what I observe for a correction angle (crab angle) while flying. In your experience if I correct my IAS and TAS by modifying the static port will I cause large changes and induce possible error on "indicated" altitude? As info i have the SafeAir1 system on my 8 including static ports and the static leak test was passed with flying colors just a month ago. I appreciate all the info you've share on this and other topics. John -------- John Keller, TX RV-8 N247TD Read this topic online here: http://forums.matronics.com/viewtopic.php?p=362269#362269 ________________________________ Message 7 _____________________________________ Time: 03:14:32 PM PST US From: "Bob Mills" Subject: RE: RV-List: Re: Dynon Skyview Airspeed Calibration... John, As you prepare to make your airspeed calibration runs, I'd also recommend you ensure your compass is well calibrated also. I have a legacy Dynon panel, but have also found that I saw very odd wind readouts before I ran a compass cal (or re-ran the cal after maintenance). Heading and speed errors will both wreak havoc with the GPS wind readouts, so eliminating both is important. Recommend running the compass cal with engine running, avionics on, and canopy closed...as close as you can get to normal in-flight conditions. I've used the NTPS spreadsheet from Kevin's site a lot (thanks Kevin), and it's a great tool! My TAS readout is consistently 2-4 knots faster than GPS readouts...lower when the standard deviation block on the spreadsheet is lower (meaning the data is better). My static ports are the standard rivet, so I think the shape is good. I actually think I have a bit of an issue with OAT (actually a touch of Ram Rise), since I always test at top speed (for speed mods), and I can see a change in OAT just by slowing or accelerating. Before I add thickness to the static port, I'm going to run some tests at slower speeds to see if the TAS-GPS speed delta decreases, then try moving the OAT probe from under the H-stab to inside the fuselage back there. We'll see. Just mentioned all this, as there are a few inputs to consider, and nulling out the others before making static port changes may be a good idea. I'd also like to hear Kevin's (and others') thoughts on the speed error versus altitude error question, but I would think that with all inputs calibrated, making a physical change to the static ports to reduce IAS/TAS errors would also reduce other static system output errors (like altitude). Good discussion! Cheers, Bob RV-6 N600SS Reno, NV -----Original Message----- From: owner-rv-list-server@matronics.com [mailto:owner-rv-list-server@matronics.com] On Behalf Of Bubblehead Sent: Monday, January 02, 2012 12:37 PM Subject: RV-List: Re: Dynon Skyview Airspeed Calibration... Kevin, I've been on your site a lot today reading about this. Next weekend if weather permits I will collect a lot of Numbers to plug into your speadsheet to see about IAS and TAS. I suspect the TAS on my Skyview is significantly off because I am getting wind vectors that disagree significantly with forecast winds aloft and what I observe for a correction angle (crab angle) while flying. In your experience if I correct my IAS and TAS by modifying the static port will I cause large changes and induce possible error on "indicated" altitude? As info i have the SafeAir1 system on my 8 including static ports and the static leak test was passed with flying colors just a month ago. I appreciate all the info you've share on this and other topics. John -------- John Keller, TX RV-8 N247TD Read this topic online here: http://forums.matronics.com/viewtopic.php?p=362269#362269 ________________________________ Message 8 _____________________________________ Time: 03:31:45 PM PST US Subject: Re: RV-List: Re: Dynon Skyview Airspeed Calibration... From: Kevin Horton John, Modifying the static ports to reduce the error in IAS will also reduce the error in the indicated altitude, IF the static port is the source of your problem. If the static port is not the source of your problem you could be introducing new errors in your altitude by modifying the static ports. Be very sure that you have ruled out other possible errors before attacking the static ports. 1. Be very sure that you don't have leaks in the static or pitot systems - do your own checks, rather than assuming the result from a month ago is still valid - you could easily have a new leak. 2. Measure the ASI instrument error in your EFIS - don't simply assume it is zero - my Dynon EFIS has some ASI instrument error. 3. And be sure your OAT is reasonably accurate. If after doing the three items above without finding a problem, then you must have issues with the static ports, which will affect both airspeed and altitude. Static port changes that reduce the ASI error will also reduce the altimeter error. Kevin On 2012-01-02, at 15:36 , Bubblehead wrote: > > Kevin, > > I've been on your site a lot today reading about this. Next weekend if weather permits I will collect a lot of Numbers to plug into your speadsheet to see about IAS and TAS. I suspect the TAS on my Skyview is significantly off because I am getting wind vectors that disagree significantly with forecast winds aloft and what I observe for a correction angle (crab angle) while flying. > > In your experience if I correct my IAS and TAS by modifying the static port will I cause large changes and induce possible error on "indicated" altitude? > > As info i have the SafeAir1 system on my 8 including static ports and the static leak test was passed with flying colors just a month ago. > > I appreciate all the info you've share on this and other topics. > > John > > -------- > John > Keller, TX > RV-8 N247TD > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=362269#362269 > > > > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message rv-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/RV-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/rv-list Browse Digests http://www.matronics.com/digest/rv-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.