mvsgas Posted July 2, 2008 Posted July 2, 2008 And more off topic: The turbine engines can't be over-revved right? Maybe I dive into the manual for a bit I do not know if this is model on LOFC, I have never try it. Base on jet engines I have work on (F-100-PW-220/220E and F-110-GE-100) Jet engine can only be "over-revved" (A.K.A. over speed) if there is a malfunction. Keep in minds this are military fighter jet engines, are suppose to have quick responds to Throttle inputs, I have never work civilian jet engines so not sure how they compare. Jet engine are normally control by several computers. Some digital , some analog and even hydro mechanical controls in some occasions (like a carburetor basically) that should...should control engine RPM at all times. OF course malfunctions happen and that is why jet engines (like any other type of engine) has a specific operating range for a specific throttle setting and should help the user identify a malfunction. For example a F-110 may idle anyware from 60% to 80% at idle. Pretty big range if you ask me but, if the RPM are below or above this, you know that something is wrong. When you do quick throttle or PLA changes, you can actually feel the engine trying to slow down. It will vibrate a little among other things. Sorry for the OT, I just wanted to type my two cents as always :D. To whom it may concern, I am an idiot, unfortunately for the world, I have a internet connection and a fondness for beer....apologies for that. Thank you for you patience. Many people don't want the truth, they want constant reassurance that whatever misconception/fallacies they believe in are true..
GGTharos Posted July 2, 2008 Posted July 2, 2008 The range is so large because RPM is adjusted for pressure altitude difference; at high altitude your engine might be idling at min burner! [sIGPIC][/sIGPIC] Reminder: SAM = Speed Bump :D I used to play flight sims like you, but then I took a slammer to the knee - Yoda
mvsgas Posted July 2, 2008 Posted July 2, 2008 (edited) I know bud, very unlikely to idle at min burner do, burner has nothing to do with RPMs. Ok maybe one thing, not enough RPM, augmentation or afterburner become just a exhaust fire. :D Edited Also temperature and other factor like engine operating time etc. affect rpm or idle. Engine with high times normally have higher RPMs Edited July 2, 2008 by mvsgas To whom it may concern, I am an idiot, unfortunately for the world, I have a internet connection and a fondness for beer....apologies for that. Thank you for you patience. Many people don't want the truth, they want constant reassurance that whatever misconception/fallacies they believe in are true..
Boberro Posted July 2, 2008 Posted July 2, 2008 In Su-25T it is also modelled, I spotted various RPM on various altitudes. Reminder: Fighter pilots make movies. Bomber pilots make... HISTORY! :D | Also to be remembered: FRENCH TANKS HAVE ONE GEAR FORWARD AND FIVE BACKWARD :D ಠ_ಠ ツ
sobek Posted July 2, 2008 Posted July 2, 2008 Jet engine can only be "over-revved" (A.K.A. over speed) if there is a malfunction. Modern Jet-Engines with FADEC that is, older ones without computerised engine control can easily be destroyed or at least worn out by just pushing the throttle up real fast from idle. May result in a runaway :D or just high egt. cheers Good, fast, cheap. Choose any two. Come let's eat grandpa! Use punctuation, save lives!
mvsgas Posted July 2, 2008 Posted July 2, 2008 (edited) Modern Jet-Engines with FADEC that is, older ones without computerised engine control can easily be destroyed or at least worn out by just pushing the throttle up real fast from idle. May result in a runaway :D or just high egt. cheers Your right,they did have this problem in -100 PW engines and older jet engines, but for example, F-110 in SEC mode, it is not control by a FADEC, it is control by the MEC (main engine control) When the MEC takes control, the augmenter is shut down, the compressor guide vanes are put to optimum position it still operates very good and, at least in my experience, it response just as quickly without stalls or over temps. Edited The MEC is a hydro mechanical control with no computers AFAIK. It is called MFC in the F-100-PW Edited July 2, 2008 by mvsgas sorry I can spell to save my life To whom it may concern, I am an idiot, unfortunately for the world, I have a internet connection and a fondness for beer....apologies for that. Thank you for you patience. Many people don't want the truth, they want constant reassurance that whatever misconception/fallacies they believe in are true..
sobek Posted July 2, 2008 Posted July 2, 2008 The MEC is a hydro mechanical control with no computers AFAIK. Damn u got me :cry:. Im quasi an electro-egineer, so i keep forgetting about the mechanical ancestors of the computer:doh:. Good, fast, cheap. Choose any two. Come let's eat grandpa! Use punctuation, save lives!
mvsgas Posted July 3, 2008 Posted July 3, 2008 Damn u got me :cry:. Im quasi an electro-egineer, so i keep forgetting about the mechanical ancestors of the computer:doh:. :D keep in mind man, I only know the two engines, there are thousands of different designs out there and I have no idea how those work. You where right, jet engine can still over speed, AFAIK. I just have never seen that in engines I have work on, unless a malfunction occurs. Sorry for the OT guys, I always do that, it was not intentional :doh: To whom it may concern, I am an idiot, unfortunately for the world, I have a internet connection and a fondness for beer....apologies for that. Thank you for you patience. Many people don't want the truth, they want constant reassurance that whatever misconception/fallacies they believe in are true..
BeachAV8R Posted July 7, 2008 Posted July 7, 2008 In the jets I fly for a living (Citation Ultra and V) we can overspeed the engines (JT15D-5A) since they aren't FADEC controlled. Interestingly though, you don't overspeed them in descents..but rather, more often in a climb. For instance, if I have maximum allowable power on in cruise flight at FL370, depends on temperature but the maximum ever allowable is 104% N1. The throttle is set for that..but if I get a step climb to a higher altitude, if I pitch up into a 4-500 FPM climb, obviously overall speed drops (from about Mach .73 to Mach .68) and the fan RPM will climb a few percentage points. If you don't pull back the throttles slightly, you will be (according to the charts) overspeeding the engine. The opposite is true when speeding up. Say I just leveled off at FL370 after a climb and I'm showing Mach .65 or something with 104% power (max cruise)..as the plane accelerates, I assume that is putting more force on the fan and the fan speed will actually drop a couple % points. So as it drops, you keep bumping it back up to max allowable until you get to where the plane isn't speeding up anymore (between .72 and .75). I don't know if any of this has anything to do with this discussion..lol..just thought I'd mention how it works in that particular type of aircraft. Now you can see why having a FADEC is so nice..you just sort of set it and forget it as opposed to having to constantly tweak it (at least it gives us something to do though I guess..) :D BeachAV8R Oh..and back on topic..yeah, Black Shark really is that good. Really. :D
mikoyan Posted July 8, 2008 Posted July 8, 2008 keep those comments guys, it makes this forum more interesting
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