Re: [Flightgear-devel] f16 speedbrakes
This would be good to see in a plot. Can you do that? Jon -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Alex Romosan Sent: Saturday, September 06, 2008 5:06 PM To: FlightGear developers discussions Subject: Re: [Flightgear-devel] f16 speedbrakes Jon S. Berndt writes: I don't know if this matters, but remember that not too long ago we added the ability to enter aero coefficients in several coordinate systems - including BODY and WIND, etc. so if i were to represent the wind tunnel data in x,y,z axis then the drag due to horizontal tail deflection (the data on pages 45-49 of the nasa technical paper 1538) would then look like this: axis name=X function name=aero/coefficient/CDDh descriptionDrag_due_to_horizontal_tail_deflection/description product propertyaero/qbar-psf/property propertymetrics/Sw-sqft/property table name=CDdHT - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Jon S. Berndt writes: This would be good to see in a plot. Can you do that? i guess jsbsim can do it but i never tried it. any pointers? --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | | automatism and other passive states) to systematize confusion | | and thus to help to discredit completely the world of reality. | - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
On Fri, Sep 5, 2008 at 11:54 PM, Erik Hofman [EMAIL PROTECTED] wrote: I also see that (I'm only looking at the speedbrakes effects). Two things are unclear for me: 1. The values of alpha in f16.xml are exactly half those in NASA's TP1538 report. 2. The values of the coefficients are close to each other, but not exactly the same. For CmDsb I'm looking on TP1538 page 58 (PDF page 64) For CLDsb I'm looking on TP1538 page 65 (PDF page 71) Off course you need to transform the data from body axes to wind axes first.. Erik Sorry I've mixed the page numbers on TP1538 paper in my former message. Erik, 1. Transformation from body to wind axes would modify the coefficient values much more than the differences I see; moreover, I see difefrences even at alpha=0 (for CmDsb, -0.0036 in f16.xml instead of -0.0038 in TP1538). 2. The alpha values are still HALF those on TP1538. No matters what our conclusion will be on these issues, I really value the great job you've done in this model, making it a great source for learning JSBSim. Thanks. Fabian - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Jon S. Berndt writes: I don't know if this matters, but remember that not too long ago we added the ability to enter aero coefficients in several coordinate systems - including BODY and WIND, etc. so if i were to represent the wind tunnel data in x,y,z axis then the drag due to horizontal tail deflection (the data on pages 45-49 of the nasa technical paper 1538) would then look like this: axis name=X function name=aero/coefficient/CDDh descriptionDrag_due_to_horizontal_tail_deflection/description product propertyaero/qbar-psf/property propertymetrics/Sw-sqft/property table name=CDdHT independentVar lookup=rowaero/beta-deg/independentVar independentVar lookup=columnaero/alpha-deg/independentVar independentVar lookup=tablefcs/elevator-pos-deg/independentVar tableData breakPoint=-25 -30 -25 -20 -15 -10 -8 -6 -4 -2 0 2 4 6 8 10 15 20 25 30 -20 -0.1837 -0.1853 -0.1904 -0.1899 -0.1949 -0.1914 -0.1872 -0.186 -0.186 -0.1868 -0.1899 -0.1902 -0.19 -0.1896 -0.1883 -0.1833 -0.1838 -0.1787 -0.1771 -15 -0.1714 -0.1765 -0.1792 -0.1827 -0.1816 -0.1834 -0.1852 -0.1853 -0.1877 -0.1875 -0.1898 -0.1876 -0.1868 -0.1848 -0.1841 -0.1852 -0.1817 -0.179 -0.1739 -10 -0.1531 -0.1627 -0.1692 -0.1718 -0.1695 -0.1693 -0.1707 -0.1735 -0.1772 -0.1787 -0.1769 -0.1729 -0.1711 -0.1706 -0.1698 -0.1721 -0.1695 -0.163 -0.1534 -5 -0.1151 -0.1232 -0.1276 -0.1317 -0.139 -0.1415 -0.142 -0.1425 -0.1437 -0.1432 -0.1425 -0.1422 -0.141 -0.1397 -0.1372 -0.1299 -0.1258 -0.1214 -0.1133 0 -0.0907 -0.0985 -0.1043 -0.1093 -0.112 -0.1115 -0.1122 -0.1124 -0.113 -0.1132 -0.1129 -0.1119 -0.111 -0.1102 -0.1092 -0.1065 -0.1015 -0.0957 -0.0879 5 -0.0514 -0.0567 -0.0603 -0.064 -0.0653 -0.0661 -0.0668 -0.0675 -0.069 -0.0693 -0.0686 -0.068 -0.0664 -0.065 -0.0649 -0.0631 -0.0594 -0.0558 -0.0505 10 -0.0079 -0.0108 -0.0099 -0.0101 -0.0074 -0.007 -0.0078 -0.009 -0.0116 -0.012 -0.0123 -0.0106 -0.0088 -0.0083 -0.008 -0.0107 -0.0105 -0.0114 -0.0085 15 0.0354 0.0358 0.0388 0.0402 0.0477 0.0503 0.0535 0.0553 0.0538 0.0537 0.0533 0.0536 0.0527 0.0509 0.0485 0.041 0.0396 0.0366 0.0362 20 0.074 0.0756 0.0746 0.0745 0.0867 0.0888 0.0924 0.0941 0.0948 0.0951 0.0975 0.0939 0.0913 0.0867 0.0824 0.0702 0.0703 0.0713 0.0697 25 0.1092 0.1124 0.1102 0.1067 0.1101 0.1121 0.1126 0.1129 0.1123 0. 0.1122 0.1125 0.1136 0.1115 0.1075 0.1041 0.1076 0.1098 0.1066 30 0.0915 0.101 0.0975 0.1079 0.1188 0.1333 0.1399 0.1422 0.1443 0.1435 0.1431 0.1407 0.1379 0.1359 0.1323 0.1214 0.111 0.1145 0.105 35 0.1079 0.1137 0.1198 0.1278 0.1402 0.1425 0.1478 0.157 0.1623 0.1663 0.1667 0.1664 0.1637 0.156 0.146 0.1336 0.1256 0.1195 0.1137 40 0.1306 0.1437 0.135 0.1441 0.1574 0.1585 0.1601 0.1682 0.1726 0.1739 0.1711 0.1699 0.1655 0.1611 0.1567 0.1434 0.1343 0.143 0.1299 45 0.1535 0.1603 0.1605 0.1604 0.1637 0.1671 0.1664 0.1639 0.1674 0.1659 0.1649 0.165 0.1625 0.1597 0.1573 0.154 0.1541 0.1539 0.1471 50 0.1471 0.1584 0.1646 0.1671 0.1712 0.1712 0.1676 0.1644 0.1656 0.1693 0.1714 0.1728 0.1749 0.1725 0.173 0.1537 0.1457 0.1435 0.1362 55 0.1554 0.1615 0.1568 0.1661 0.1778 0.1769 0.1765 0.1749 0.1762 0.1804 0.1743 0.1666 0.1677 0.1724 0.1761 0.1722 0.1347 0.1448 0.1442 60 0.1501 0.1599 0.1647 0.1525 0.1664 0.1662 0.1704 0.171 0.1719 0.1718 0.1728 0.173 0.1734 0.1721 0.1688 0.1471 0.1462 0.1486 0.146 70 0.1501 0.1536 0.1569 0.142 0.1573 0.1595 0.1788 0.1715 0.1738 0.1695 0.171 0.1712 0.173 0.172 0.1686 0.1474 0.1567 0.1557 0.1545 80 0.1685 0.1615 0.1559 0.152 0.1521 0.1521 0.1535 0.1585 0.1566 0.1598 0.1573 0.1563 0.1586 0.1558 0.1572 0.141 0.141 0.1467 0.1538 90 0.1712 0.1651 0.1608 0.1648 0.1676 0.166 0.1686 0.1667 0.1669 0.166 0.1672 0.1662 0.1664 0.1711 0.1677 0.1531 0.1493 0.1549 0.1624 /tableData tableData breakPoint=-10 -30 -25 -20 -15 -10 -8 -6 -4 -2 0 2 4 6 8 10 15 20 25 30 -20 -0.1362 -0.1351 -0.1419 -0.1386 -0.1374 -0.133 -0.1268 -0.1249 -0.1222 -0.1223 -0.1246 -0.1247 -0.1252 -0.1257 -0.1282 -0.1294 -0.1327 -0.1259 -0.127 -15 -0.1216 -0.1245 -0.1235 -0.1208 -0.1176 -0.1176 -0.117 -0.1177 -0.1184 -0.1188 -0.1185 -0.1187 -0.1182 -0.1178 -0.1184 -0.1216 -0.1243 -0.1253 -0.1224 -10 -0.1018 -0.1066 -0.1068 -0.1071 -0.1061 -0.1068 -0.1072 -0.1083 -0.1094 -0.1147 -0.1095 -0.1084 -0.1077 -0.1063 -0.1069 -0.1079 -0.1076 -0.1074 -0.1026 -5 -0.0655 -0.0706 -0.0746 -0.0771 -0.0836 -0.0864 -0.0876 -0.0887 -0.0889 -0.0893 -0.0885 -0.0875 -0.0859 -0.0842 -0.0812 -0.0747 -0.0722 -0.0682 -0.0631 0 -0.0483 -0.0509 -0.0532 -0.0544 -0.0578 -0.0589 -0.0597 -0.0606 -0.0613 -0.0617 -0.0611 -0.0603 -0.0595 -0.0577 -0.0561 -0.0527 -0.0515 -0.0492 -0.0466 5 -0.0118 -0.0106 -0.0096 -0.0102 -0.0142 -0.0148 -0.0155 -0.0161
Re: [Flightgear-devel] f16 speedbrakes
On 9/4/08, Alex Romosan [EMAIL PROTECTED] wrote: Erik Hofman writes: Alex Romosan wrote: can you give me a pointer as to where i could get this data? thanks. Search for NASA Technical Paper 1538 i've been looking at it but i can't figure out the relationship between the number in the report and the numbers in the flightgear model. if somebody could explain the magic involved i would really appreciate it. thanks. --alex-- I also see that (I'm only looking at the speedbrakes effects). Two things are unclear for me: 1. The values of alpha in f16.xml are exactly half those in NASA's TP1538 report. 2. The values of the coefficients are close to each other, but not exactly the same. For CmDsb I'm looking on TP1538 page 58 (PDF page 64) For CLDsb I'm looking on TP1538 page 65 (PDF page 71) Ron? Fabian - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Fabian Grodek wrote: On 9/4/08, *Alex Romosan* [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] wrote: Erik Hofman writes: Alex Romosan wrote: can you give me a pointer as to where i could get this data? thanks. Search for NASA Technical Paper 1538 i've been looking at it but i can't figure out the relationship between the number in the report and the numbers in the flightgear model. if somebody could explain the magic involved i would really appreciate it. thanks. --alex-- I also see that (I'm only looking at the speedbrakes effects). Two things are unclear for me: 1. The values of alpha in f16.xml are exactly half those in NASA's TP1538 report. 2. The values of the coefficients are close to each other, but not exactly the same. For CmDsb I'm looking on TP1538 page 58 (PDF page 64) For CLDsb I'm looking on TP1538 page 65 (PDF page 71) Off course you need to transform the data from body axes to wind axes first.. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Of course you need to transform the data from body axes to wind axes first.. Erik I don't know if this matters, but remember that not too long ago we added the ability to enter aero coefficients in several coordinate systems - including BODY and WIND, etc. Jon - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Erik Hofman writes: Alex Romosan wrote: can you give me a pointer as to where i could get this data? thanks. Search for NASA Technical Paper 1538 i've been looking at it but i can't figure out the relationship between the number in the report and the numbers in the flightgear model. if somebody could explain the magic involved i would really appreciate it. thanks. --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | | automatism and other passive states) to systematize confusion | | and thus to help to discredit completely the world of reality. | - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
On 8/30/08, Erik Hofman [EMAIL PROTECTED] wrote: ... But I don't see any pitching moment effect; from what I see in NASA TP 1538 http://hdl.handle.net/2002/11034 I understand there is a pitch-down effect from the speedbrakes. It looks like you don't have the latest version of the configuration file, it's defined under CmDsb I see. The current f16.xml version in JSBSim repository is 1.82, which indeed has the CmDsb effect. Nevertheless, the current f16.xml version in FlighGear is 1.44, which does not contain the CmDsb component. Since this is a FlightGear mailing list, I was looking only at the file on FG repository. Fabian - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
On Sun, 2008-08-31 at 12:31 +0200, Fabian Grodek wrote: On 8/30/08, Erik Hofman [EMAIL PROTECTED] wrote: ... But I don't see any pitching moment effect; from what I see in NASA TP 1538 http://hdl.handle.net/2002/11034 I understand there is a pitch-down effect from the speedbrakes. It looks like you don't have the latest version of the configuration file, it's defined under CmDsb I see. The current f16.xml version in JSBSim repository is 1.82, which indeed has the CmDsb effect. Nevertheless, the current f16.xml version in FlighGear is 1.44, which does not contain the CmDsb component. Since this is a FlightGear mailing list, I was looking only at the file on FG repository. Fabian Fabian, Version 1.44 is the release version. It has had many updates since then and is currently at version 1.62 http://cvs.flightgear.org/viewvc/data/Aircraft/f16/f16.xml?view=logpathrev=HEAD Ron - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Alex Romosan wrote: can you give me a pointer as to where i could get this data? thanks. Search for NASA Technical Paper 1538 Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Fabian Grodek wrote: Erik, In the F16 aero config file I see there's indeed an increase in lift for certain speedbrakes deflection, accompanied by the expected huge increase in drag. But I don't see any pitching moment effect; from what I see in NASA TP 1538 http://hdl.handle.net/2002/11034 I understand there is a pitch-down effect from the speedbrakes. It looks like you don't have the latest version of the configuration file, it's defined under CmDsb Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Erik Hofman writes: Alex Romosan wrote: can you give me a pointer as to where i could get this data? thanks. Search for NASA Technical Paper 1538 thanks. --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | | automatism and other passive states) to systematize confusion | | and thus to help to discredit completely the world of reality. | - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Alex Romosan wrote: i hate to bring this up again but i still think the speedbrakes don't work as they should, instead generating quite a lot of lift. i've tested this on final approach at about 160-170 knots, speedbrakes on; i can keep the plane level. retract the speedbrakes, the plane starts descending really fast (the nose position doesn't change). open the speed brakes, the plane goes climbing. again this is with the engine at idle and at very slow speeds. Believe me, this is correct behavior, and this is why: The fuselage sections on either side, between the the engine compartment (the round tube) and the wing root are good for 15% to 25% of the generated lift. Get them wrong on RC controlled model airplanes and it won't even fly properly (I know this from second hand experience). Now, if you deploy the speedbrakes the lower clamp shell acts exactly like a flap at the rear end of the wing. If it weren't for the presence of the upper clamp shell, it wouldn't even produce much drag. I can assure you; it is modeled correctly now. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Erik Hofman writes: Believe me, this is correct behavior, and this is why: i found a nice article about flying in an f16: http://www.avweb.com/news/skywrite/181916-1.html this is the part about the speed brakes: Here's where the speed brakes come in handy, I'll open em up. And you'll see what happens. I felt what happens! It seemed my face was being pulled from my skull. I couldn't believe how effective those speed brakes were. An F-16's speed brakes are located at the back of the fuselage either side of the engine nacelle, and really look diminutive. However, introducing even that much surface area to hang out in the 600-mph breeze has a pronounced effect on one's forward motion. We slowed to about 400 then he retracted the brakes and let the airspeed start increasing again. --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | | automatism and other passive states) to systematize confusion | | and thus to help to discredit completely the world of reality. | - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Alex Romosan wrote: Erik Hofman writes: Believe me, this is correct behavior, and this is why: i found a nice article about flying in an f16: http://www.avweb.com/news/skywrite/181916-1.html this is the part about the speed brakes: Here's where the speed brakes come in handy, I'll open em up. And you'll see what happens. I felt what happens! It seemed my face was being pulled from my skull. I couldn't believe how effective those speed brakes were. An F-16's speed brakes are located at the back of the fuselage either side of the engine nacelle, and really look diminutive. However, introducing even that much surface area to hang out in the 600-mph breeze has a pronounced effect on one's forward motion. We slowed to about 400 then he retracted the brakes and let the airspeed start increasing again. This says nothing about generating lift or not.. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Erik Hofman writes: Alex Romosan wrote: I felt what happens! It seemed my face was being pulled from my skull. I couldn't believe how effective those speed brakes were. An F-16's speed brakes are located at the back of the fuselage either side of the engine nacelle, and really look diminutive. However, introducing even that much surface area to hang out in the 600-mph breeze has a pronounced effect on one's forward motion. We slowed to about 400 then he retracted the brakes and let the airspeed start increasing again. This says nothing about generating lift or not.. no, but it would seem to indicate that the speed brakes are quite effective at slowing down the aircraft which is not at all the case with the current model in flightgear. and nothing to do with the speed brakes, but this is a really cool video of an f16 dead stick landing: http://www.patricksaviation.com/videos/SUPERGT/3384 --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | | automatism and other passive states) to systematize confusion | | and thus to help to discredit completely the world of reality. | - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
On ven 29 août 2008, Erik Hofman wrote: Alex Romosan wrote: Erik Hofman writes: Believe me, this is correct behavior, and this is why: i found a nice article about flying in an f16: http://www.avweb.com/news/skywrite/181916-1.html this is the part about the speed brakes: Here's where the speed brakes come in handy, I'll open em up. And you'll see what happens. I felt what happens! It seemed my face was being pulled from my skull. I couldn't believe how effective those speed brakes were. An F-16's speed brakes are located at the back of the fuselage either side of the engine nacelle, and really look diminutive. However, introducing even that much surface area to hang out in the 600-mph breeze has a pronounced effect on one's forward motion. We slowed to about 400 then he retracted the brakes and let the airspeed start increasing again. This says nothing about generating lift or not.. Erik Only my 2 cents, if the question is not stupid :) How does the fly-by-wire, regarding the speedbrake lift effect ? Regards BTW: An other AC the F15 should have a negative lift with speedbrake -- Gérard http://pagesperso-orange.fr/GRTux/ J'ai décidé d'être heureux parce que c'est bon pour la santé. Voltaire - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
gerard robin wrote: A Only my 2 cents, if the question is not stupid :) How does the fly-by-wire, regarding the speedbrake lift effect ? What happens (with regard to the fly-by-wire system) is this: Speedbrake deflection causes a pitching moment which the FCS automatically compensates because there is no pitching moment requested by the pilot. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Alex Romosan wrote: Erik Hofman writes: Alex Romosan wrote: I felt what happens! It seemed my face was being pulled from my skull. I couldn't believe how effective those speed brakes were. An F-16's speed brakes are located at the back of the fuselage either side of the engine nacelle, and really look diminutive. However, introducing even that much surface area to hang out in the 600-mph breeze has a pronounced effect on one's forward motion. We slowed to about 400 then he retracted the brakes and let the airspeed start increasing again. This says nothing about generating lift or not.. no, but it would seem to indicate that the speed brakes are quite effective at slowing down the aircraft which is not at all the case with the current model in flightgear. Sorry, I got the data from windtunnel test data performed by NASA. I tend to believe that over a first time experience from some one claiming he has had the time of his life. So until somebody can show me what exactly is wrong I won't change it and won't let anybody else make changes to it. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Erik Hofman writes: Sorry, I got the data from windtunnel test data performed by NASA. can you give me a pointer as to where i could get this data? thanks. --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | | automatism and other passive states) to systematize confusion | | and thus to help to discredit completely the world of reality. | - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Ok, I think I have most of it figured out. I might even consider upgrading the status to 'production' the way it is now. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Erik Hofman writes: Ok, I think I have most of it figured out. I might even consider upgrading the status to 'production' the way it is now. hmm, i don't know how the real f-16 behaves but i still find the current behaviour a bit strange. level flight, ~350 knots extend the brakes the aircraft pitches up slightly and really starts to climb (no effect on the speed at all). push the nose down (quite a lot) to bring it back to level flight speed actually increases. not very useful if you are actually trying to slow down. --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | | automatism and other passive states) to systematize confusion | | and thus to help to discredit completely the world of reality. | - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Alex Romosan wrote: hmm, i don't know how the real f-16 behaves but i still find the current behaviour a bit strange. level flight, ~350 knots extend the brakes the aircraft pitches up slightly and really starts to climb (no effect on the speed at all). push the nose down (quite a lot) to bring it back to level flight speed actually increases. not very useful if you are actually trying to slow down. I have checked the data three times to see if I was doing something wrong, but unless someone mixed up the tables in the wind tunnel data report got this is how it should behave. I do know that it actually does reduce airspeed (albeit a little) with 7.5 degree pitch down at final approach, Which sounds about right to me. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Ok, tested it again. The only way I could reproduce your scenario is not to have the throttle near idle. As I did state earlier, the speeedbrakes of the F-16 are quite small and as it turns out the engine can easily produce enough thrust to overcome the increased drag. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Erik Hofman writes: Ok, tested it again. The only way I could reproduce your scenario is not to have the throttle near idle. As I did state earlier, the speeedbrakes of the F-16 are quite small and as it turns out the engine can easily produce enough thrust to overcome the increased drag. yes, the throttle was nowhere near idle. thanks for the great work. --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | | automatism and other passive states) to systematize confusion | | and thus to help to discredit completely the world of reality. | - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Erik Hofman writes: You were right, I had to map speedbrake-pos-norm to speedbrake-pos-rad/deg by using an aerosurface scale section. i think there is still something wrong with the speedbrakes but i am not sure how to quantify this. basically i think they provide way too much lift (which makes me suspect there is a sign problem somewhere). the effect is more pronounced at slower speeds (250 - 300 knots or so). extend the speedbrakes and see the f16 suddenly start climbing. handy if you are too low on approach but not realistic at all (i would expect the speedbrakes to cause the plane to lose altitude faster not provide lift). --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | | automatism and other passive states) to systematize confusion | | and thus to help to discredit completely the world of reality. | - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Alex Romosan wrote: i think there is still something wrong with the speedbrakes but i am not sure how to quantify this. basically i think they provide way too much lift (which makes me suspect there is a sign problem somewhere). the effect is more pronounced at slower speeds (250 - 300 knots or so). extend the speedbrakes and see the f16 suddenly start climbing. handy if you are too low on approach but not realistic at all (i would expect the speedbrakes to cause the plane to lose altitude faster not provide lift). Correct, in fact it's creating a downpitching moment that is overcompensated with the current setup. I'm still working on this. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Alex Romosan wrote: i noticed that on the f16 the speedbrakes have no effect at all and i managed to track it down to the fact that the various coefficients use fcs/mag-speedbrake-pos-rad on input which never gets set anywhere (so it is always 0). digging through the cvs logs i found that in version 1.17 of f16.xml the output of fcs/speedbrake-cmd-norm used to be fcs/speedbrake-pos-rad and it was set to 1.05 (which would translate roughly to 60 degrees). so i tried applying this patch: now the various coefficients change when i activate the speedbrake but there is still no noticeable effect on the plane. does anybody have any ideas how to fix the speedbrakes? Looking at the code it looks like setting speed-break-pos-norm should be the same as setting speed-break-pos-rad so the patch shouldn't have any effect. I think you expect too much effect from the speedbrakes, they are quite small for the F-16 and can be deployed in-flight without any problems (in fact, they tend to get used during the complete final approach cycle over here). Try diving without any power (throttle to nil) with the speedbrakes deployed for a while and then retract them. If all works well you will see the speed increase. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Erik Hofman writes: Looking at the code it looks like setting speed-break-pos-norm should be the same as setting speed-break-pos-rad so the patch shouldn't have any effect. look at aero/coefficient/CDDsb or fcs/mag-speedbrake-pos-rad in the property browser. when you deploy the speed brakes the values are still zero (they never change). and i looked at the code speed-break-pos-norm never sets speed-break-pos-rad (it couldn't really, what would be the correlation). --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | | automatism and other passive states) to systematize confusion | | and thus to help to discredit completely the world of reality. | - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Alex Romosan wrote: Erik Hofman writes: Looking at the code it looks like setting speed-break-pos-norm should be the same as setting speed-break-pos-rad so the patch shouldn't have any effect. look at aero/coefficient/CDDsb or fcs/mag-speedbrake-pos-rad in the property browser. when you deploy the speed brakes the values are still zero (they never change). and i looked at the code speed-break-pos-norm never sets speed-break-pos-rad (it couldn't really, what would be the correlation). I just tested it and it seems have less effect than I expected. hmm. Have to look at it some more. Both are affected when one or the other is changed since they are tied using the property manager to the proper function in JSBSim/models/FGFCS.cpp which sets the same internal variable. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] f16 speedbrakes
Alex Romosan wrote: Erik Hofman writes: Looking at the code it looks like setting speed-break-pos-norm should be the same as setting speed-break-pos-rad so the patch shouldn't have any effect. look at aero/coefficient/CDDsb or fcs/mag-speedbrake-pos-rad in the property browser. when you deploy the speed brakes the values are still zero (they never change). You were right, I had to map speedbrake-pos-norm to speedbrake-pos-rad/deg by using an aerosurface scale section. Thanks for the hints. Erik - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
[Flightgear-devel] f16 speedbrakes
i noticed that on the f16 the speedbrakes have no effect at all and i managed to track it down to the fact that the various coefficients use fcs/mag-speedbrake-pos-rad on input which never gets set anywhere (so it is always 0). digging through the cvs logs i found that in version 1.17 of f16.xml the output of fcs/speedbrake-cmd-norm used to be fcs/speedbrake-pos-rad and it was set to 1.05 (which would translate roughly to 60 degrees). so i tried applying this patch: --- f16.xml 18 Jul 2008 14:41:41 - 1.50 +++ f16.xml 31 Jul 2008 20:22:09 - @@ -572,6 +572,12 @@ outputfcs/speedbrake-pos-norm/output /kinematic + pure_gain name=Speedbrake Deflection + inputfcs/speedbrake-pos-norm/input + gain60./gain + outputfcs/speedbrake-pos-deg/output + /pure_gain + /channel channel name=Landing Gear now the various coefficients change when i activate the speedbrake but there is still no noticeable effect on the plane. does anybody have any ideas how to fix the speedbrakes? --alex-- -- | I believe the moment is at hand when, by a paranoiac and active | | advance of the mind, it will be possible (simultaneously with | | automatism and other passive states) to systematize confusion | | and thus to help to discredit completely the world of reality. | - This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100url=/ ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
