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Author
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Topic: Engine power and altitudes
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Nat
Pilot
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posted 01-21- 03:24 PM
   
Hey guys, OK, for my side project I've found very good info, but I'm not exactly sure if we can do this right... I have the engine power listed thus:Some data on the ASh-82V engine: Cylinder diameter 155.5mm
Cylinder motion 155...156mm
Engine volume 41.2l
Compression ratio 6.9 (+0.15 -0.1) HP RPM SFC
Ground normal 1150 2400 285...315
Ground maximal 1430 2400 315...340
Takeoff 1700 2600 325...360
Cruise at 1550m 1530 2400 ?
Cruise at 4550m 1330 2400 ? OK, the Q really is, can this drop in HP actually be modeled, or is it modeled in code? or am I just up the shitter? lol ~Nat~
oh.. as a further note, the aircraft this engine is from has the following power data: Take off Power - 1850hp
1550m - 1630hp
4500m - 1500hp This may be easier to model if there's a way to link a qryAlt to maxHP.. damn I wish we could use proper code.. like "If..Then..Else"
IP: Logged |
Falck
Pilot
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posted 01-21- 04:24 PM
I dont think it is modelled at this point.This would be a good addition for SOS.
The ratio of shaft power to ground level shaft power for a non-supercharged engine is given by the formula: (1.176*p/p0)-0.176 where p is the atmospheric density and p0 is atmospheric density at sea level.
Source: Theory of Flight, Richard von Mises p/p0 can be found in the 1976 Standard Atmosphere. IP: Logged |
wakeup tailgunner
Pilot
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posted 01-22- 06:07 AM
I know the Qry commands can't be used to trigger a function. It's a real pain!IP: Logged |
Nat
Pilot
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posted 01-22- 11:14 AM
TG your a genius! er... sorry, well, what you just said isn't entirely true.....  thanks for the idea bro lolIP: Logged |
Maury Markowitz
Pilot
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posted 01-22- 02:58 PM
quote:
Originally posted by Falck:
The ratio of shaft power to ground level shaft power for a non-supercharged engine is given by the formula: (1.176*p/p0)-0.176 where p is the atmospheric density and p0 is atmospheric density at sea level.
Of course the super/turbo/injection issues make things a lot tougher. The only real solution here is to provide several complete power vs. altitude curves and interpolate between them. Actually for most planes there would be only one, and one more for those planes that have some sort of "triggered" injection. Maury IP: Logged |
Tailslide
Pilot
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posted 01-25- 03:36 AM
I have power vs alt curves for many of the planes in SDOE if anyone can ever figure out how to change the HP with altitude that would be wonderful it was the one thing I wish could have been patched in all this time  TS
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Nat
Pilot
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posted 01-25- 04:41 AM
Agreed Tail, this is the reason I'm having massive FM problems with the La5, at 20,000ft I've got 1850hp pushing that prop round, when realy I should only have 1300hp, it's proving very hard to get the ratios right, I get the speeds right at 20,000ft and 1,000ft, but then the thing struggles like hell at takeoff speeds to generate enough lift. Add more lift, and you're speeds are screwed up again and so on and so on...IP: Logged |
Spanky the Mad Dog
Pilot
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posted 01-25- 05:40 AM
Spanky here...
No offence to MH and company but its really hard to belive that they left this out. Really screws the FMs. no matter what kind of data you have and how good you are at plugging it in. Guess we better hope this is an area that crosswindsims takes a good look at. Soon as that database is up please chime in with your wishes guys. IP: Logged |
Gecko
Pilot
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posted 01-26- 10:59 AM
Here is a far fetched idea, but it just might work.Suppose you have a set of engines, each having a corresponding power, and each is a child of a member of a set of (invisible) CDial objects that are all directly attached to the plane. Each CDial object should have a DOF that doesn't really do anything (the travel should be close to 0), but should have the following property: (this is for the, say, 6th dial/engine combination) ... oscBeginDisabled 'Engine6 oscEndDisabled 'Engine6 ... in the DOF properties, while the CDial itself should have the following enabled ... dataQuery (qryAltASLF) Min 10000 Max 12000 ... Hopefully this will mean that the Engine6 object would be enabled within 10000 to 12000 feet. Similar should be then done for the Engine5 to be enabled from 8000 to 10000 feet and Engine 7 from 12000 to 14000 feet and so on. -Gecko IP: Logged |
Gecko
Pilot
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posted 01-26- 11:03 AM
I would hate to think what would happen at the altitude transition points.-Gecko IP: Logged |
Nat
Pilot
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posted 01-26- 11:43 AM
It's a good and interesting idea Geko but from the little I know I don't think it will work, the DOF will beginning moving at mission start because the qryAlt alwys does that, and not only at certain altitudes, the min max I believe are only for ratio with regards to DOF/Alt.Maybe someone can say I'm wrong, I mean about it not working, not my basic explination lol IP: Logged |
jedi
Pilot
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posted 01-26- 11:44 AM
Hmmm. You might be able to create a CDial object, mounted on the fuselage or wing, that was linked to the altitude, and pivoted up. Attach a drag airfoil to that object, and it would be given a higher angle of attack as you climb, and thus generate more drag (but also more lift). If you tweaked that drag foil for max drag and min lift, you could probably "bog down" the plane's speed at altitude.
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--jedi-- IP: Logged |
Tailslide
Pilot
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posted 01-26- 12:52 PM
Thats a cool idea.. it may be hard to do without the plane handling funny though. To minimize the effect on the FM you could have symmetrical drag airfoils that deflect up and down equal amounts on the fuselage at the mid point of the wing. However spins will be very different since while the drag airfoils do nothing when the plane is travelling straight it will have a tendancy to dampen the spin. TS IP: Logged |
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