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brucek

No carb heat on 172 or twins?

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I realize fuel injected planes don't have carb heat but shouldn't the default 172 or the RealAir 172 have it? Also, I've yet to see a twin that has it. Are they all fuel injected (even the older ones)?David

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David,I've just been thinking about the same thing. I also don't have a working carb. heat switch with the realair172. Now, I haven't tried using a keyboard shortcut to activate it, maybe it's just the panel we're using that doesn't show when carbheat is activated?!Quite frankly I have never heard of a fuel injected 172, I've flown many 172P's here at Comair and some Piper's back in Ohio, all of them were carburetor equipped, so maybe it's just something about the panel we're using? BTW which panel are you using?Cheers,Petehttp://members.aol.com/pzsoulman/myhomepage/logo.gifAthlonXP2000,AbitKX7-333(latest4in1),512MB/2700SDRAM,WinXP,DirectX8.1,Geforce3TI200(128MB)(Det.30.82),SBlive(WDM5.1.2601.0)

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I just checked the aircraft.cfg and there is an entry:(piston_engine) power_scalar = 1.01 //Piston power scalar cylinder_displacement= 90.0 //Cubic inches per cylindercompression_ratio= 8.5 //Compression rationumber_of_cylinders=4 //Number of cylindersmax_rated_rpm= 2700 //Max rated RPMmax_rated_hp= 180 //Max rated HPfuel_metering_type= 0 //0=Fuel Injected, 1=Gravity Carbureter, 2=Aerobatic CarbureterChange "fuel_metering_type" to "1". I just did and it enabled my carbheat switch along with a drop in RPM (roughly 300 RPM, so quite a bit more than in real life, but that's a FS2K2 limitation).Now, I don't know if that has an adverse effect on the great FDE by realair but it's worth a try.Cheers,Petehttp://members.aol.com/pzsoulman/myhomepage/logo.gifAthlonXP2000,AbitKX7-333(latest4in1),512MB/2700SDRAM,WinXP,DirectX8.1,Geforce3TI200(128MB)(Det.30.82),SBlive(WDM5.1.2601.0)

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Wow! Thanks Pete. I haven't messed with the cfg files other than the panel one so I appreciate the tip.David

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For what it's worth, the POH for a 1979 172N claims 160HP @ 2700 rpm; I wonder if that's changed if the reduction in RPM would be a little more realistic?The engine capacity is listed as being 320 cu. in.; this means 80 per cylinder, so I imagine that the 4X90, or 360 cu. in. may also be played with above.. hey, I may go try this out.The POH also says that a magneto check should yield about a 125 rpm drop, but doesn't specify the drop for carb heat.Also, was your carb heat turned on @ 1700 RPM or 2700?Cheers,Andrew

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Andrew,I did try the carbheat during runup @1700prm and had a 300rpm drop (haven't tried it during any other phase yet). I don't think my POH (don't have it handy right now) says anything about the carbheat drop either, but in our airplanes here it usually is around 100rpm and of course you want the enging still running after you go idle ;-)At Comair we don't takeoff if we have mag drops of more than 100 and no more than 50 between both mags.I read some time ago that the numbers in the aircraft.cfg and airfile don't neccesarily have to be exactly what it says in the engine specs. to make it fly to its engine specs, but I'm no FDE specialist ;-) I might go and try your suggestion about the cylinders, maybe changing it will give it a somewhat reduced climb performance (just my preference for the old airplanes we usually fly here).Let me know about your findings,Pete http://members.aol.com/pzsoulman/myhomepage/logo.gifAthlonXP2000,AbitKX7-333(latest4in1),512MB/2700SDRAM,WinXP,DirectX8.1,Geforce3TI200(128MB)(Det.30.82),SBlive(WDM5.1.2601.0)

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And so is the RealAir 172, which is based on the default. These are SP models which use a 180HP Lycoming and are fuel injected, unlike older Cessna models such as the 172N. ------- No Carb Heat ------------L.Adamson

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Hi David,I fly the 172SP in real life (as is modelled in FS2k2). It has a fuel injected engine (182HP), and as such does not have a carberator(sp?), and therefore no carb heat.I can't answer on the twins.Bruce.

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Any fuel injected aircraft, such as the C172R/S/SP, C182, Baron, Mooney, will not have carb heat because as Bruce stated, there is no carburetor. Fuel injection is a much more effiecient way of getting fuel to the engine than a carburetor is, because it more evenly distrubutes fuel to each cylinder. Both have advantages and disadvantages though. Carburetors are susceptible to carb icing in ambient temperatures as high as 70* F. Fuel injection on the other hand is subject to vapor lock if proper start-up and shut-down procedures are not adhered to.

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Another disadvantage of fuel injection is about $5000.00 difference for the engine.. :( L.Adamson

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Hey Travis,Could you explain the concept of "vapor lock" on a fuel-injected engine? You mentioned that one could cause damage if the proper start-up/shut-down procedures are not followed...would my Buick have the same issue, or does the computer take care of it?Thanks!

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Vapor lock is of no danger to the engine, as far as I know. What happens is that there is fuel in the line after shut-down, and it vaporizes as the plane sits, leaving air pockets in the fuel line. If the proper start sequence is not followed (in the C172: aux. fuel pump on for 3-5 seconds with throttle and mixture full forward) the pockets in the line will reach the engine and not allow it to start. Turning on the fuel pump forces fuel through the lines to 'pop' all the air pockets. You could look at it as the exact opposite of flooding a carbureted engine.

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Sorry, a little off topic... Does FS actually model carb ice? I have some hazy recollection of getting carb ice passing through clouds... or like, known icing conditions. I'm wondering about more hazardous carb ice while flying regular VFR. BTW, I had a flight lesson (PA28-140) on the weekend and experienced some real-life carb ice. We were still on the apron...just before run-up. My instructor noted a drop in RPM; he asked, what should I do? I reached for the throttle, and he said no not that. Then I reach for the mixture, and he said no not that either. Hmmm, What then? Carb ice just wasn't on my mind. The conditions were prime though....very humid and I'd say 9-10 degrees C or so. I can imagine now, if I had compensated with throttle I might not have notice the condition until it was critical. Believe me, the landing checks in the circuit included a very thorough carb ice test. :-)DannyCYVRL.Adamson, aren

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Oh, it's a beauty!! This aircraft is the business...Mine would be a Lycoming to (only dreaming). Don't you get a little queasy when you see auto conversions with reduction drives? Very nice panel...must be saving your nickels to put something in that hole under the com radio. It looks like you're quite close to completion, but I guess that can be kind of deceiving. For paint I see all red like a Falco or maybe a military theme.Keep pounding those rivets :-)DannyCYVR

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It would be great to know if the (well known) incorrect drop in FS2k2 of 300rpm for carb heat could be altered, I practice using the carb heat modelled on the Dreamfleet Archer 11 and have to over correct on the throttle to make it realistic.

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Now THAT is a home cockpit!!! ;-) Looking at it gives me that same feeling I had when I first met my wife (what are the odds she's checking this forum?). Seriously a beautiful piece of work. Are you going to share any of the details with us? My hesitation with building something like this (besides the money!) is with every project I've ever built I am always keenly aware of my mistakes and its weak points. I can imagine flying along thinking "man, I wonder if that bolt that I cross-threaded is going to hold".David

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1998 and later 172's are all fuel-injected, as are all of the other piston Cessnas that have been built since they re-started their Little Airplane production. The designators are 172R, 172S, and 172SP.The '98s and maybe the '99s are quite prone to vapor lock on hot days - in other words, they start reasonably easy when cold but if you do a flight, get out and shut down, and then try to restart a few minutes later it can be "interesting". Later models (2001 and on?) seem to be less persnickety in this regard - I think Cessna tweaked the injection system on those. On all of these though, the key is not to prime the engine with the fuel pump when it's warm on a re-start - just crank and go.But I'd much rather put up with injection than a carburetor. IMO a carbureted engine in a modern airplane is like a rotary dial phone - it works but why put up with it? Carb heat is just another thing that you have to keep in mind when flying, and the cockpit workload is high enough as it is. This is exacerbated in helicopters such as the Schweizer 300CB, where you need to apply carb heat on descents - trust me your hands are already full and it's a drag having to let go of something, reach up to the instrument panel, and turn on the heat. *And* then you need to turn it off in the flare as you get ready to land, so that max engine power is available, and that's probably the highest workload point of normal helicopter flight.If you don't stay on top of potential carb icing, it can ruin a previously great day. It's killed more than one person, and is especially dangerous in helicopters. Unlike an airplane, whose engine will continue windmilling if the carb ices up, the rotor system will just slow down and stop if the pilot doesn't lower the collective control *immediately* (within a second or so, in the R22) upon engine failure. (And even then, you'll be landing *soon* and *nearby*.) It's killed people in fixed wing aircraft as well.Sorry, I got on my pilot workload soapbox there... But I much prefer fuel injection!BTW, IMO FS2002 doesn't model the start sequence in the 172SP very well. It's way too easy 8^) .Dave Blevins

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Hi Larry,The next time my wife and I fly out to SLC to visit our daughter there, I must get in touch with you- I'd love to see that machine!Bruce.

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