Re: [Flightgear-devel] Questions about flight model
Hermann Schiffer wrote: > > The Merlin is a rotary engine, isn't it? > > A rotary engine ? As in http://travel.howstuffworks.com/rotary-engine.htm ? He meant "radial", of course, which was true of most WWII era aircraft engines other than the Merlin. And if you really want to nit, what you describe is best called a Wankel engine. A "rotary" engine in aviation context is an ancient design where the pistons were arranged radially, but were fixed to the propeller and spun with the engine. The early propellers weren't large enough and the early engines not smooth enough to idle successfully without a flywheel. This was a trick to turn the whole engine into a flywheel. :) http://en.wikipedia.org/wiki/Rotary_engine Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Questions about flight model
> The Merlin is a rotary engine, isn't it? A rotary engine ? As in http://travel.howstuffworks.com/rotary-engine.htm ? Most people probably will agree that it's a V-12 piston engine ;-) Details about the engine oil pressure might be documented in some sort of engine manual: http://www.yellowairplane.com/Book_Reviews/Mustang_Manual/Mustang_Manual_Cover.html Regards, Hermann > In any case, a pump attached to > the engine accessory drive (along with the vacuum pump, etc.) is standard > on a horizontally-opposed engine. The O-320 in my Warrior does have a > relief valve, as well as a breather in the accessory housing to avoid > excess pressure buildup in the crankcase. > > Oil pressure is usually pretty constant at anything other than idle RPM > once the engine's warmed up, suggesting that the relief valve kicks in > pretty early, as with the vacuum pump -- I'll try to pay more attention > next time I'm up (rather than just checking that it's in the green). > > > All the best, > > > David > > ___ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Questions about flight model
Vivian Meazza wrote: The Merlin has a gear-driven oil pump and, I assume, a pressure relief valve. I was going to assume that oil pressure was a function of rpm with max and min values. The Merlin is a rotary engine, isn't it? In any case, a pump attached to the engine accessory drive (along with the vacuum pump, etc.) is standard on a horizontally-opposed engine. The O-320 in my Warrior does have a relief valve, as well as a breather in the accessory housing to avoid excess pressure buildup in the crankcase. Oil pressure is usually pretty constant at anything other than idle RPM once the engine's warmed up, suggesting that the relief valve kicks in pretty early, as with the vacuum pump -- I'll try to pay more attention next time I'm up (rather than just checking that it's in the green). All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Questions about flight model
David Megginson wrote > Andy Ross wrote: > > > But the idea behind YASim is to produce plausible results for all > > possible engines; oil pressure is one of those values that > is (AFAIK) > > just too engine-specific. > > Further to the point, here is some information from the > Lycoming O-320 > Operator's manual; it would make a good starting point for > horizontally-opposed piston engines. > > Oil Temperature: > >180 degF desired, 245 degF maximum >[down to 160 degF and 210 degF below 10 degF OAT] > > Oil Pressure: > >Normal: 90 psi maximum, 60 psi minimum, 25 psi idling >Start and warm up: 100 psi maximum > > > All the best, > The Merlin has a gear-driven oil pump and, I assume, a pressure relief valve. I was going to assume that oil pressure was a function of rpm with max and min values. Of course, it is also a function of oil temperature, which is a function of engine temperature. We already know egt. Are most of the building blocks in place already? If we don't want or need a sophisticated answer, then a function of rpm would be enough for an instrument, and that can easily be done in XML. Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Questions about flight model
David Megginson wrote: > How about allowing the config to contain a couple of sample values > and then interpolating (taking into account outside temperature, > engine temperature, and power setting)? Sure. That was the idea with the Nasal script, actually. Set it to poll every second or so and compute a target for the next second's interpolation. It would be really easy to make this general, so every aircraft/engine could specify a property tree for configuring it, along the lines of the existing flaps detents settings, etc... And if an aircraft wants its own handling, it just writes its own script. But I'm open to suggestions. I'm mildly resistant to putting this in YASim only because table lookup isn't really its thing, and I'm doubtful that such a (fixed, in-FDM-configuration) scheme would really be generic enough for most aircraft anyway. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Questions about flight model
--- Andy Ross <[EMAIL PROTECTED]> wrote: > Luca Masera wrote: > > about YASim: in which units is measured the oil pressure? > > In JSBSim the value is holded by "oil-pressure-psi" and it's > > measured in psi; in YASim is holded by "epr" but the units > > are missing. > > Er, that's an Engine Pressure Ratio , which is a thrust metric used > in > early jets in lieu of N1 RPM. FWIW, P&W still prefers EPR over N1. > YASim doesn't model oil pressure right > now, because I'm not aware of a good basis on which to do so. If you > have numbers you want to match for this particular aircraft, I could > write you up some Nasal in just a few minutes which would do the job. > But the idea behind YASim is to produce plausible results for all > possible engines; oil pressure is one of those values that is (AFAIK) > just too engine-specific. > > The units are missing, btw, because there aren't any. It's a ratio. > > Andy > > ___ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel > > __ Do you Yahoo!? Yahoo! Photos: High-quality 4x6 digital prints for 25ยข http://photos.yahoo.com/ph/print_splash ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Questions about flight model
Andy Ross wrote: But the idea behind YASim is to produce plausible results for all possible engines; oil pressure is one of those values that is (AFAIK) just too engine-specific. Further to the point, here is some information from the Lycoming O-320 Operator's manual; it would make a good starting point for horizontally-opposed piston engines. Oil Temperature: 180 degF desired, 245 degF maximum [down to 160 degF and 210 degF below 10 degF OAT] Oil Pressure: Normal: 90 psi maximum, 60 psi minimum, 25 psi idling Start and warm up: 100 psi maximum All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Questions about flight model
Andy Ross wrote: Er, that's an Engine Pressure Ratio , which is a thrust metric used in early jets in lieu of N1 RPM. YASim doesn't model oil pressure right now, because I'm not aware of a good basis on which to do so. If you have numbers you want to match for this particular aircraft, I could write you up some Nasal in just a few minutes which would do the job. But the idea behind YASim is to produce plausible results for all possible engines; oil pressure is one of those values that is (AFAIK) just too engine-specific. How about allowing the config to contain a couple of sample values and then interpolating (taking into account outside temperature, engine temperature, and power setting)? All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Questions about flight model
Luca Masera wrote: > about YASim: in which units is measured the oil pressure? > In JSBSim the value is holded by "oil-pressure-psi" and it's > measured in psi; in YASim is holded by "epr" but the units > are missing. Er, that's an Engine Pressure Ratio , which is a thrust metric used in early jets in lieu of N1 RPM. YASim doesn't model oil pressure right now, because I'm not aware of a good basis on which to do so. If you have numbers you want to match for this particular aircraft, I could write you up some Nasal in just a few minutes which would do the job. But the idea behind YASim is to produce plausible results for all possible engines; oil pressure is one of those values that is (AFAIK) just too engine-specific. The units are missing, btw, because there aren't any. It's a ratio. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Questions about flight model
Luca Masera wrote > Hi everyone, > > I'm creating the 3d instruments for the mb339 using JSBSim > and YASim as flight dynamics models. > > The questions are: > > about YASim: in which units is measured the oil pressure? > In JSBSim the value is holded by "oil-pressure-psi" and it's > measured in psi; in YASim is holded by "epr" but the units > are missing. > Epr is exhaust pressure ratio. AFAIK, oil pressure is not modelled. Regards Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Questions about flight model
On Fri, 23 Apr 2004 17:43:59 +0200 "Luca Masera" <[EMAIL PROTECTED]> wrote: Hi everyone, about JSBBim: the airplane has three tanks, but the flight model uses only the first. In other words, if I start FlightGear with the first tank empty, the engine is off and doesn't starts. This happens even if the first tank is plenty or with few fuel (I've tried with 1gal and when it's all consumed, the engine shuts off, even if the other two tanks are full). How I can solve this problems? There's someone that could helps me? We'll look at that. Tanks, Tanks, Jon ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
[Flightgear-devel] Questions about flight model
Hi everyone, I'm creating the 3d instruments for the mb339 using JSBSim and YASimas as flight dynamics models. The questions are: about YASim: in which units is measured the oil pressure? In JSBSim the value is holded by "oil-pressure-psi" and it's measured in psi; in YASim is holded by "epr" but the units are missing. about JSBBim: the airplane has three tanks, but the flight model uses only the first. In other words, if I start FlightGear with the first tank empty, the engine is off and doesn't starts. This happens even if the first tank is plenty or with few fuel (I've tried with 1gal and when it's all consumed, the engine shuts off, even if the other two tanks are full). How I can solve this problems? There's someone that could helps me? Tanks, Luca ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
