Bucic Posted February 16, 2011 Posted February 16, 2011 Well done effte! :thumbup: Rep inbound! I bet AccuSim guys will start to stalk you in groups of 3 to 12 in no time :D F-5E simpit cockpit dimensions and flight controls Kill the Bloom - shader glow mod Poor audio Doppler effect in DCS [bug] Trees - huge performance hit especially up close
MTFDarkEagle Posted February 16, 2011 Posted February 16, 2011 The rule of thumb is just a rule of thumb. While it worked for some old Dinocomings etc, there are no guarantees. Well, yes that's why it's a rule of thumb :P Brit gauges show MAP relative to atmospheric while US gauges show absolute pressure. In other words, you need to add 1 atm. Yes and thanks for adding. I was about to say I forgot that part ;) Lukas - "TIN TIN" - 9th Shrek Air Strike Squadron TIN TIN's Cockpit thread
Avilator Posted February 16, 2011 Posted February 16, 2011 Brit gauges show MAP relative to atmospheric while US gauges show absolute pressure. In other words, you need to add 1 atm. Good to know, thanks. I only respond to that little mechanical voice that says "Terrain! Terrain! Pull Up! Pull Up!" Who can say what is impossible, for the dream of yesterday is the hope of today and the reality of tomorrow. -Robert Goddard "A hybrid. A car for enthusiasts of armpit hair and brown rice." -Jeremy Clarkson "I swear by my pretty floral bonet, I will end you." -Mal from Firefly
Stretch Posted February 16, 2011 Posted February 16, 2011 How come the Brits and the Americans can never agree on anything?! Tim "Stretch" Morgan 72nd VFW, 617th VFS Other handles: Strikeout (72nd VFW, 15th MEU Realism Unit), RISCfuture (BMS forums) PC and Peripherals: https://pcpartpicker.com/user/RISCfuture/saved/#view=DMp6XL Win10 x64 — BMS — DCS — P3D
andysim Posted February 16, 2011 Posted February 16, 2011 I killed my engine last flight. Forgot to set mixture back to rich after cruise and my engine died soon after roll out on the runway hehe. Sure is alot to remeber with this bird especialy the engine and airframe limits. Thats what makes it so special. Cant wait for the P-51 its gonna be fantastic.
Succellus Posted February 16, 2011 Posted February 16, 2011 They agree on bashing the french... well nowadays. Because usally French and American agreed on bashing the brits. HaF 922, Asus rampage extreme 3 gene, I7 950 with Noctua D14, MSI gtx 460 hawk, G skill 1600 8gb, 1.5 giga samsung HD. Track IR 5, Hall sensed Cougar, Hall sensed TM RCS TM Warthog(2283), TM MFD, Saitek pro combat rudder, Cougar MFD.
effte Posted February 16, 2011 Posted February 16, 2011 The official, non-Accusim, MkII manual from Zeno's do not contain the limitation on windmilling, FWIW. I find that more plausible, but I wonder where Accusim got their information. I don't see them as the kind of people who'd make things up. I'm in a hotel room, so I'll have to check more manuals when back home if noone else beats me to it (yes, that was a challenge! ;)). Cheers, Fred ----- Introduction to UTM/MGRS - Trying to get your head around what trim is, how it works and how to use it? - DCS helos vs the real world.
msalama Posted February 17, 2011 Posted February 17, 2011 (edited) The official, non-Accusim, MkII manual from Zeno's do not contain the limitation on windmilling, FWIW. And that's all well and correct I think? There're no reasons why an inline engine should have any windmilling limitations AFAIK, since that (or, in other words, letting the prop drive the engine) is only harmful to radial engines because of the way their conrod-crankshaft bearing lubrication is designed IIRC. Can't for the life of me remember the details just now, but it has something to do with how the main bearing lube oil feeder just works in them... :helpsmilie: Edited February 17, 2011 by msalama The DCS Mi-8MTV2. The best aviational BBW experience you could ever dream of.
MTFDarkEagle Posted February 17, 2011 Posted February 17, 2011 (edited) There're no reasons why an inline engine should have any windmilling limitations AFAIK Are you kidding me!? Any propellor driven engines have windmilling limitations. I know a spitfire expert, and I've asked him to shed some light on this. What I know is going on is that the forces work in the wrong direction. I.e. the pistons drive the crank, as it should, but in a windmill state the crank would be forcing the pistons up and down, which you can image isn't very good for the engine. When the guy I e-mailed get's back (hopefully) with some more info, I'll get back to this. Edited February 17, 2011 by MTFDarkEagle typo Lukas - "TIN TIN" - 9th Shrek Air Strike Squadron TIN TIN's Cockpit thread
Bucic Posted February 17, 2011 Posted February 17, 2011 What I know is going on is that the forces work in the wrong direction. I.e. the pistons drive the crank, as it should, but in a windmill state the crank would be forcing the pistons up and down, which you can image isn't very good for the engine. When the guy I e-mailed get's back (hopefully) with some more info, I'll get back to this. Engines are not my major but... There's nothing directional (in radial plane) in any ball/roller bearing I know of even assuming all the forces get reversed during windmilling. On top of that all bearings and supports do take multi-directional loads during normal and steady machine operation due to elements inertia and vibrations. The more you will prove me wrong, the more interesting your info will be to me :) so please post the pilot's feedback on that matter. Someone has asked from where A2A gets their info on engines and ACs operation details. Well, those realism wackos are in direct contact with few warbirds pilots and mechanics. That maniac standing there with that silly furry microphone... http://www.youtube.com/user/ShockwaveProd ... is Scott - the founder and owner of Air to Air Inc. and the narrator in most of their promotional vids :D 1 F-5E simpit cockpit dimensions and flight controls Kill the Bloom - shader glow mod Poor audio Doppler effect in DCS [bug] Trees - huge performance hit especially up close
Succellus Posted February 17, 2011 Posted February 17, 2011 Waiting for info too HaF 922, Asus rampage extreme 3 gene, I7 950 with Noctua D14, MSI gtx 460 hawk, G skill 1600 8gb, 1.5 giga samsung HD. Track IR 5, Hall sensed Cougar, Hall sensed TM RCS TM Warthog(2283), TM MFD, Saitek pro combat rudder, Cougar MFD.
msalama Posted February 17, 2011 Posted February 17, 2011 (edited) Are you kidding me!? Any propellor driven engines have windmilling limitations. Oh yeah, sorry, shouldn't have said NO limitations because of course anything breaks down if the counterforce is strong enough ;) What I meant was that there're NO SUCH limitations as exist with radial engines. Is that OK? Edited February 17, 2011 by msalama The DCS Mi-8MTV2. The best aviational BBW experience you could ever dream of.
MTFDarkEagle Posted February 18, 2011 Posted February 18, 2011 Allright, the guy has responded and I have a better understanding. It's like this: The main problem is that leaving high rpm with throttle right back turns the engine into a gigantic vacuum pump. This means that all parts which are normally seated by suction (for instance piston rings) are sucked OUT of their recesses and flap around. This can cause significant wear of those parts and any part they "support". The other thing is that in a high performance engine, everything is optimised to deliver power ONE WAY. So, if you start transfering forces back the other way it puts stresses on them that they are simply not designed for. Think of extending a compression spring. It will not deliver the same sorts of forces as it does in the designed direction, and will weaken and lose performance quickly. Lukas - "TIN TIN" - 9th Shrek Air Strike Squadron TIN TIN's Cockpit thread
sobek Posted February 18, 2011 Posted February 18, 2011 (edited) Allright, the guy has responded and I have a better understanding. I don't know, not to hit on your source's credentials, but some things do sound a little strange. I have not come across one engine where the piston rings were held in place by suction. They were held in place by the cylinder wall. I could imagine that their seating position and therefore alignment with the cylinder wall becomes slightly offset by the effects you mentioned, but it still seems like a far stretch. Another thing that is striking is that every 4-stroke engine works as pump for 2 cycles by design. It just sounds illogical that it would suffer from load that it has to bear every other cycle. Heck, i mean, trucks even use this feature for braking (closing the intake and breaking with the engine trying to suck against the vacuum). So there must be some design peculiarity to explain this, or it is just a myth, IMHO. Something with the lubrication system, i guess, but that is just a shot in the dark. Edited February 18, 2011 by sobek Good, fast, cheap. Choose any two. Come let's eat grandpa! Use punctuation, save lives!
MTFDarkEagle Posted February 18, 2011 Posted February 18, 2011 The guy is a aerobatics pilot and has 20-odd years of spitfire research. So he know's his stuff ;) And yes, the (mis)allignment would be the problem like you mentioned. Regarding your reference to a truck: that's a) a diesel and b) not a high performance engine. Lukas - "TIN TIN" - 9th Shrek Air Strike Squadron TIN TIN's Cockpit thread
sobek Posted February 18, 2011 Posted February 18, 2011 Regarding your reference to a truck: that's a) a diesel and b) not a high performance engine. So you're saying that the engine takes a lot of damage everytime it is driven by the starter motor? I just don't see it. Those bearings are designed to take horrendous loads, most likely with crest factors that are in the ludicrous department, why would they falter under a much lesser load? One thing that comes to mind is that if the gearbox uses cogs with diagonal cut teeth and the associated axial load bearings are not laid out to take force resulting from the momentum being reversed, that could pose a problem, but entirely not to the engine. But IMHO it doesn't make sense to build a gearbox that way. Would be interesting to look at the details more closely. Good, fast, cheap. Choose any two. Come let's eat grandpa! Use punctuation, save lives!
Bucic Posted February 18, 2011 Posted February 18, 2011 I'm not convinced either to be honest. Especially regarding those piston rings. Maybe you misunderstood when he meant sealing rings and gaskets? Plus next time it would be great if he didn't use any simplifications from the proper technical terminology just for the sake of simplification. Anyway, I would nag Dudley Henriques (a real warbird pilot) who offered a proper assistance to anyone having problems or questions regarding the Spitfire AccuSim module http://a2asimulations.com/forum/viewtopic.php?f=77&t=23604 Go ahead and exploit it :sly: F-5E simpit cockpit dimensions and flight controls Kill the Bloom - shader glow mod Poor audio Doppler effect in DCS [bug] Trees - huge performance hit especially up close
msalama Posted February 18, 2011 Posted February 18, 2011 Well the jury's still out as it comes to inlines I suppose, but radials OTOH definitely don't like reverse loading. This guy seems to know his stuff and he thinks it's a big (and potentially expensive) no-no with round engines at least... 2 The DCS Mi-8MTV2. The best aviational BBW experience you could ever dream of.
sobek Posted February 18, 2011 Posted February 18, 2011 (edited) That was an interesting read, thanks for sharing. Edited February 18, 2011 by sobek Good, fast, cheap. Choose any two. Come let's eat grandpa! Use punctuation, save lives!
msalama Posted February 18, 2011 Posted February 18, 2011 (edited) That was an interesting read, thanks for sharing. You're welcome m8, Randy Sohn is always an education :) But thruth be telt this guy has probably forgotten more about vintage aero engines than we all put together will ever learn. Still, would be nice to know what the practical limitations really are for, say, the Merlin and/or the DB601 too... Edited February 18, 2011 by msalama The DCS Mi-8MTV2. The best aviational BBW experience you could ever dream of.
636_Castle Posted February 18, 2011 Author Posted February 18, 2011 I think I'll do an overhaul, log my actions and readings through a flight or two until something starts breaking, and then post it here. :) [sIGPIC][/sIGPIC] How To Fix Your X-52's Rudder!
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