Re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
On Thu, 2002-09-19 at 06:52, Alex Perry wrote: > > Does the R have a 40 deg flap detent? > > My understanding is that the 40 deg flap setting (over the whole family) > is actually related to max gross weight. If you want the 40 deg then you > will be limited to 2300 lb; if you make do with 30 deg ... you can have more. > > However, as the interior gets nicer, the avionics become more complete, > you add long range tanks, a larger engine, retractable gear, etc etc ... > you're adding empty weight, so that after a while 2300 lb is not enough. > You're then _forced_ to eliminate the 40 deg setting to be able to fly. > > The last ten degrees _are_ mostly drag, but that's what you need > (a) to get a steep final in rugged terrain > (b) for fast descents in emergency management > (c) for a relatively quick flare for short fields (d) to keep %N1 up (for faster spool up) in a jet. > > ___ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
On Thu, 2002-09-19 at 06:34, Tony Peden wrote: > On Thu, 2002-09-19 at 06:19, David Megginson wrote: > > Tony Peden writes: > > > > > Does the R have a 40 deg flap detent? > > > > No. The 172R and 172P allow up to 30deg flaps, but the 172M (mid > > 1970s) goes to 40deg -- it feels like dragging a parachute. > > That's typical. You get to a point with flap deflection where more > deflection tends to only give more drag and no more lift. Of course, > sometimes that's what you want ... BTW, I'm caught up in other things at the moment and probably won't be able to get to any of this for a while. So feel free make the needed adjustments yourself, if you care to. > > > > > > > > All the best, > > > > > > David > > > > -- > > David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ > > > > ___ > > Flightgear-devel mailing list > > [EMAIL PROTECTED] > > http://mail.flightgear.org/mailman/listinfo/flightgear-devel > > > -- > Tony Peden > [EMAIL PROTECTED] > We all know Linux is great ... it does infinite loops in 5 seconds. > -- attributed to Linus Torvalds > > > ___ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
On Thu, 2002-09-19 at 06:19, David Megginson wrote: > Tony Peden writes: > > > Does the R have a 40 deg flap detent? > > No. The 172R and 172P allow up to 30deg flaps, but the 172M (mid > 1970s) goes to 40deg -- it feels like dragging a parachute. That's typical. You get to a point with flap deflection where more deflection tends to only give more drag and no more lift. Of course, sometimes that's what you want ... > > > All the best, > > > David > > -- > David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ > > ___ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel > -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
Tony Peden writes: > Does the R have a 40 deg flap detent? No. The 172R and 172P allow up to 30deg flaps, but the 172M (mid 1970s) goes to 40deg -- it feels like dragging a parachute. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
On Thu, 2002-09-19 at 05:27, David Megginson wrote: > Tony Peden writes: > > > > My suggestion is that c172.xml (and --aircraft=c172) would disappear > > > altogether, and we'd have c172p.xml and c172r.xml instead. > > > > I don't really object to that -- except that I wonder how many folks > > will be able to really tell the difference. Surely, even in the real > > thing, the differences are fairly subtle. I'm also not so sure that we > > have the fidelity that making that distinction implies. > > It's worth thinking beyond the basic aerodynamics, though. For > example, the stock 172P has an O320 engine instead of the 172R's > IO360, so the engine startup sequence and inflight engine management > (once we model them correctly) are significantly different. Good point. > The 172R > climbs more aggressively and flares longer than the 172P, but it also > has a smaller useful load. That's fairly subtle. > Most noticeably, however, the 172R's IO360 > is derated to 2400RPM, while the 172P's engine develops the more > typical 2700RPM, so all of the power settings are different. > > I agree that a first-time user will have trouble telling the two apart > by their handling, but then, a non-pilot first-time user would have > trouble distinguishing the flying characteristics of the 172 from > those of a PA-28 or Musketeer anyway. > > The nice thing about modelling the two 172s is that we are > representing the 172 just before and just after the long hiatus in > U.S. small-aircraft production. The 1980 172P and the 1997 (?) 172R > are quite different birds in many ways: the 172P represents the end of > a long, continuous cycle of 172 development dating back to the 1950s, > while the 172R represents a new plane that Cessna built to resemble > the old 172s. I've noticed that many flying clubs and schools require > a separate check-out for the 172R. I hadn't considered differences in procedures ... that's a valid point of distinction and something that pilots would (or, at least, should) notice. Does the R have a 40 deg flap detent? > > > All the best, > > > David > > -- > David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ > > ___ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel > -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
Tony Peden writes: > > My suggestion is that c172.xml (and --aircraft=c172) would disappear > > altogether, and we'd have c172p.xml and c172r.xml instead. > > I don't really object to that -- except that I wonder how many folks > will be able to really tell the difference. Surely, even in the real > thing, the differences are fairly subtle. I'm also not so sure that we > have the fidelity that making that distinction implies. It's worth thinking beyond the basic aerodynamics, though. For example, the stock 172P has an O320 engine instead of the 172R's IO360, so the engine startup sequence and inflight engine management (once we model them correctly) are significantly different. The 172R climbs more aggressively and flares longer than the 172P, but it also has a smaller useful load. Most noticeably, however, the 172R's IO360 is derated to 2400RPM, while the 172P's engine develops the more typical 2700RPM, so all of the power settings are different. I agree that a first-time user will have trouble telling the two apart by their handling, but then, a non-pilot first-time user would have trouble distinguishing the flying characteristics of the 172 from those of a PA-28 or Musketeer anyway. The nice thing about modelling the two 172s is that we are representing the 172 just before and just after the long hiatus in U.S. small-aircraft production. The 1980 172P and the 1997 (?) 172R are quite different birds in many ways: the 172P represents the end of a long, continuous cycle of 172 development dating back to the 1950s, while the 172R represents a new plane that Cessna built to resemble the old 172s. I've noticed that many flying clubs and schools require a separate check-out for the 172R. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
On Thu, 2002-09-19 at 04:26, David Megginson wrote: > Tony Peden writes: > > > The 48 in number checks with my copy of the POH (from which many > > other numbers have been derived, so we should probably stick with > > that) > > You've talked before about forking, and that might not be a bad idea. > Right now, we're more-or-less targetting a 172R, but the 48 number > (and perhaps many others) come from a POH for earlier models. I have > the performance tables and W&B both for the 172R and the 172P -- let > me know what numbers you'd like. > > My suggestion is that c172.xml (and --aircraft=c172) would disappear > altogether, and we'd have c172p.xml and c172r.xml instead. I don't really object to that -- except that I wonder how many folks will be able to really tell the difference. Surely, even in the real thing, the differences are fairly subtle. I'm also not so sure that we have the fidelity that making that distinction implies. > > > All the best, > > > David > > -- > David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ > > ___ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
Tony Peden writes: > The 48 in number checks with my copy of the POH (from which many > other numbers have been derived, so we should probably stick with > that) You've talked before about forking, and that might not be a bad idea. Right now, we're more-or-less targetting a 172R, but the 48 number (and perhaps many others) come from a POH for earlier models. I have the performance tables and W&B both for the 172R and the 172P -- let me know what numbers you'd like. My suggestion is that c172.xml (and --aircraft=c172) would disappear altogether, and we'd have c172p.xml and c172r.xml instead. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
> Is there some reasoning behind setting the steering gains according to > the brake selection? This makes no sense to me. It looks to me like > their needs to be a separate steering selection (or just specify the > gain in the config file). Agreed. I beg your indulgence - let me have a look at this this evening. I'll try and get it resolved. I'll have to wait til the season opener for "Enterprise" is over though. :-) Jon smime.p7s Description: application/pkcs7-signature
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
On Wed, 2002-09-18 at 06:29, David Megginson wrote: > Tony Peden writes: > > > I didn't look at everything, but the nose wheel was in NONE and the > > mains CASTERED as far back as I looked (which went back to the beginning > > of time for the configurable gear). I can't explain the CASTERED mains, > > but I understood what you call steer groups to be brake groups. It > > never occurred to me that that would affect the steering control. > > Here's an excerpt from FGLGear.cpp: > > case bgNose: > SteerGain = -0.50; > BrakeFCoeff = rollingFCoeff; > break; > case bgTail: > SteerGain = -0.10; > BrakeFCoeff = rollingFCoeff; > break; > case bgNone: > SteerGain = 0.0; > BrakeFCoeff = rollingFCoeff; > break; Is there some reasoning behind setting the steering gains according to the brake selection? This makes no sense to me. It looks to me like their needs to be a separate steering selection (or just specify the gain in the config file). > > and, a little further down: > > switch (eSteerType) { > case stSteer: > SteerAngle = SteerGain*FCS->GetDrPos(); > break; > > In other words, if gear belongs to bgNone, it gets SteerGain=0.0, so > SteerAngle is always 0. Perhaps it's a recent C++ change that caused > this problem. > > Note a second problem with this code: it uses getDrPos (the actual > rudder position) and ignores maxSteerAngle from the config file. A > better option would probably be > > SteerAngle = SteerGain*FCS->GetDrCmd()*maxSteerAngle*RADTODEG; Agreed. Steering angle should not be a function of rudder position, but of pedal (or tiller) position. I tend to think this really ought to be done as an FCS component. > > It would also be nice to be able to specify SteerGain in the XML > config file rather than hard-coding it in FGLGear.cpp. Indeed. > > > (and maybe it didn't, changing the mains from CASTERED to fixed could > > have a significant effect). I need to experiment with it some more. > > The castoring doesn't make a difference (yet), because FGLGear.cpp > still treats castoring gear as fixed anyway: > > case stFixed: > SteerAngle = 0.0; > break; > case stCaster: > // Note to Jon: This is not correct for castering gear. I'll fix it later. > SteerAngle = 0.0; > break; > > > > * Usable fuel: > > > 38in (c172.xml has 56in) > > > > Hmm, I got my numbers from a POH as well. I'll have to double check. > > That's from the C172R POH. The C172P POH puts usable fuel at 48in, > probably because of the different wing shape, but it's still not as > far as c172.xml. The 48 in number checks with my copy of the POH (from which many other numbers have been derived, so we should probably stick with that) > > > All the best, > > > David > > -- > David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ > > ___ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
Jon S Berndt writes: > I may be guilty, here. Note that this file needs to be > gone through again with a fine tooth comb and validated. > Just when I think I can't become more overwhelmed than I > already am ... Wife pregnant with triplets again? (Don't laugh, my wife has a friend who had two sets of twins less than two years apart ... 4 kids less than 2 and in diapers. Yikes! Talk about bad luck.) :-) Curt. -- Curtis Olson IVLab / HumanFIRST Program FlightGear Project Twin Cities[EMAIL PROTECTED] [EMAIL PROTECTED] Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
On Wed, 18 Sep 2002 10:15:54 -0400 David Megginson <[EMAIL PROTECTED]> wrote: > >For RADTODEG, read DEGTORAD. Use degtorad and radtodeg These are consts from the FGJSBBase class. This is where commonly used constants are being migrated to, instead of #defines, which we are moving away from. Jon ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
On Wed, 18 Sep 2002 09:29:40 -0400 David Megginson <[EMAIL PROTECTED]> wrote: >Here's an excerpt from FGLGear.cpp: > > case bgNose: > SteerGain = -0.50; > BrakeFCoeff = rollingFCoeff; > break; > >In other words, if gear belongs to bgNone, it gets >SteerGain=0.0, so >SteerAngle is always 0. Perhaps it's a recent C++ change >that caused >this problem. I may be guilty, here. Note that this file needs to be gone through again with a fine tooth comb and validated. Just when I think I can't become more overwhelmed than I already am ... :-) Jon ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
David Megginson writes: > Note a second problem with this code: it uses getDrPos (the actual > rudder position) and ignores maxSteerAngle from the config file. A > better option would probably be > > SteerAngle = SteerGain*FCS->GetDrCmd()*maxSteerAngle*RADTODEG; For RADTODEG, read DEGTORAD. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
Tony Peden writes: > I didn't look at everything, but the nose wheel was in NONE and the > mains CASTERED as far back as I looked (which went back to the beginning > of time for the configurable gear). I can't explain the CASTERED mains, > but I understood what you call steer groups to be brake groups. It > never occurred to me that that would affect the steering control. Here's an excerpt from FGLGear.cpp: case bgNose: SteerGain = -0.50; BrakeFCoeff = rollingFCoeff; break; case bgTail: SteerGain = -0.10; BrakeFCoeff = rollingFCoeff; break; case bgNone: SteerGain = 0.0; BrakeFCoeff = rollingFCoeff; break; and, a little further down: switch (eSteerType) { case stSteer: SteerAngle = SteerGain*FCS->GetDrPos(); break; In other words, if gear belongs to bgNone, it gets SteerGain=0.0, so SteerAngle is always 0. Perhaps it's a recent C++ change that caused this problem. Note a second problem with this code: it uses getDrPos (the actual rudder position) and ignores maxSteerAngle from the config file. A better option would probably be SteerAngle = SteerGain*FCS->GetDrCmd()*maxSteerAngle*RADTODEG; It would also be nice to be able to specify SteerGain in the XML config file rather than hard-coding it in FGLGear.cpp. > (and maybe it didn't, changing the mains from CASTERED to fixed could > have a significant effect). I need to experiment with it some more. The castoring doesn't make a difference (yet), because FGLGear.cpp still treats castoring gear as fixed anyway: case stFixed: SteerAngle = 0.0; break; case stCaster: // Note to Jon: This is not correct for castering gear. I'll fix it later. SteerAngle = 0.0; break; > > * Usable fuel: > > 38in (c172.xml has 56in) > > Hmm, I got my numbers from a POH as well. I'll have to double check. That's from the C172R POH. The C172P POH puts usable fuel at 48in, probably because of the different wing shape, but it's still not as far as c172.xml. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
On Wed, 2002-09-18 at 05:52, David Megginson wrote: > Tony Peden writes: > > > It looks like this may have helped crosswind handling on the ground > > considerably. The relatively small amount of testing I've done shows > > that the c172 will sit still in up to a 15 knot crosswind and turn very > > slowly in 20 knots. > > > > Let us know what you think. > > I'll test it more today, but it must have been a fairly recent change > that put the nosewheel into the NONE group. I didn't look at everything, but the nose wheel was in NONE and the mains CASTERED as far back as I looked (which went back to the beginning of time for the configurable gear). I can't explain the CASTERED mains, but I understood what you call steer groups to be brake groups. It never occurred to me that that would affect the steering control. (and maybe it didn't, changing the mains from CASTERED to fixed could have a significant effect). I need to experiment with it some more. > > I have some photocopies from a C172R POH, so I can also correct some > of the arms, but I didn't want to do that without discussing it with > you (Tony) first. Using the firewall in front of the pilot as the > reference datum (as both the POH and c172.xml do), here are the arms, > or x-positions, of various masses: > > * Usable fuel: > 38in (c172.xml has 56in) > Hmm, I got my numbers from a POH as well. I'll have to double check. > * Pilot and front passenger: > 34-46in, typically 37in (c172.xml has 36in, which is OK) > > * Rear passengers: > 73in (not in c172.xml) > > * Baggage area 1: > typically 95in (not in c172.xml) > > * Baggage area 2: > typically 123in (not in c172.xml) > > > The empty weight and arm (i.e. CG) obviously vary depending on > configuration. Here are the default values for a C172R: > > * Empty weight (including oil and unusuable fuel): > 1639lb (c172.xml has 1500lb) > > * Empty arm (CG): > 39.3in (c172.xml has 41in) > > Here are the current values for our club's C172R, which has a 180HP > upgrade: > > * Empty weight (including oil and unusable fuel): > 1681.5lb > > * Empty arm (CG): > 39.1in > > > All the best, > > > David > > -- > David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ > > ___ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
re: [Flightgear-devel] Re: [Flightgear-cvslogs] Base CVSupdate:'FlightGear/FlightGear/Aircraft/c172'
Tony Peden writes: > It looks like this may have helped crosswind handling on the ground > considerably. The relatively small amount of testing I've done shows > that the c172 will sit still in up to a 15 knot crosswind and turn very > slowly in 20 knots. > > Let us know what you think. I'll test it more today, but it must have been a fairly recent change that put the nosewheel into the NONE group. I have some photocopies from a C172R POH, so I can also correct some of the arms, but I didn't want to do that without discussing it with you (Tony) first. Using the firewall in front of the pilot as the reference datum (as both the POH and c172.xml do), here are the arms, or x-positions, of various masses: * Usable fuel: 38in (c172.xml has 56in) * Pilot and front passenger: 34-46in, typically 37in (c172.xml has 36in, which is OK) * Rear passengers: 73in (not in c172.xml) * Baggage area 1: typically 95in (not in c172.xml) * Baggage area 2: typically 123in (not in c172.xml) The empty weight and arm (i.e. CG) obviously vary depending on configuration. Here are the default values for a C172R: * Empty weight (including oil and unusuable fuel): 1639lb (c172.xml has 1500lb) * Empty arm (CG): 39.3in (c172.xml has 41in) Here are the current values for our club's C172R, which has a 180HP upgrade: * Empty weight (including oil and unusable fuel): 1681.5lb * Empty arm (CG): 39.1in All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel