PDA

View Full Version : stall speed



tools4foolsA
12-19-2006, 08:02 PM
IS there anywhere a list with the stall speed of all the planes in PF?

Couldn't find one, but thought I had seen it somewhere once.

Thanks
####

tools4foolsA
12-19-2006, 08:02 PM
IS there anywhere a list with the stall speed of all the planes in PF?

Couldn't find one, but thought I had seen it somewhere once.

Thanks
####

XyZspineZyX
12-19-2006, 09:03 PM
Oddly enough I was thinking of doing one up. I'm amazed at the number of data compiled for the models in this game but not alot if not none mention stall speeds.

I suppose all you want is stall speed flaps up gear up as well as the Vso or stall speed flaps down gear down?<div class="ev_tpc_signature">

http://i48.photobucket.com/albums/f239/Skunk24/sig2.jpg
Escadron virtuel RCAF 438 (http://438cityofmontreal.googlepages.com)
<span class="ev_code_red"> Are you from Montreal? French is good? JOIN US! RCAF 438 "The City of Montreal"</span>

"You know, I've personally flown over 194 missions and I was shot down on every one. Come to think of it, I've never landed a plane in my life."

tools4foolsA
12-19-2006, 10:47 PM
Flaps up, gear up is what I was looking for.

Nobody made a list yet?

Surprising...
****

NonWonderDog
12-19-2006, 10:56 PM
There isn't one, mostly because it's pretty hard to do. A bunch of planes in the sim (pretty much anything with slats) will quite happily limp along well below Vs if you can maintain a high angle of attack and full power. This isn't unrealistic--most of these planes had rather a lot of thrust and pointing the prop upwards *does* give lift--but it makes it hard to get numbers everyone can agree on. As you can imagine, there have been some pretty huge arguments about stall speeds because of this.

Phil_C
12-20-2006, 12:22 PM
now maybe the "flight test pilots" can come up with a set of standards off of which to base all speed information? like an AOA of a specific number, just to keep things similar?<div class="ev_tpc_signature">

_______________________
My "ride"--&gt; Alienware Area 51-7500--&gt;
Intel Dual Core Extreme 3.2Ghz,Windows XP_SP2,Dual 512 Gf7900 GTX, 4Gb Ram,160Gb HD,52x32x52xCDR/W, 16xDVDR/W, Sound Blaster Audigy 2Zs, logitech 5.1 surround sound speakers

XyZspineZyX
12-20-2006, 12:35 PM
Well stall speed is usually determined by flying at low power or idle, and is the speed at which the wings no longer sustain lift. So while AOA does have its importance, it shouldnt be taken into account as the wings will stall at different AOA's at different speeds and power settings.<div class="ev_tpc_signature">

http://i48.photobucket.com/albums/f239/Skunk24/sig2.jpg
Escadron virtuel RCAF 438 (http://438cityofmontreal.googlepages.com)
<span class="ev_code_red"> Are you from Montreal? French is good? JOIN US! RCAF 438 "The City of Montreal"</span>

"You know, I've personally flown over 194 missions and I was shot down on every one. Come to think of it, I've never landed a plane in my life."

NonWonderDog
12-20-2006, 04:26 PM
Assuming you can stall the plane repeatably with the engine idle (not that easy), the most difficult part is to make sure you keep the plane at 1.00G and flying level during the test. If you're flying at .85G, you'll get a stall speed rather less than what you want. It's not as noticeable as it probably should be in planes with slats, as you can keep near complete roll control in what's almost a falling-leaf maneuver. This also caused huge hissy-fits when we tried to test the Me-109 stall speeds.

What you want to measure is the minimum speed at which the plane's wings can generate enough lift to maintain 1.00G in straight and level flight. This is stall speed... although it may not be the speed at which the plane stalls if you're at an odd attitude. (What speed will a plane stall at if pointed straight down?)

Tully__
12-21-2006, 01:04 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by NonWonderDog:
Assuming you can stall the plane repeatably with the engine idle (not that easy), the most difficult part is to make sure you keep the plane at 1.00G and flying level during the test. If you're flying at .85G, you'll get a stall speed rather less than what you want. It's not as noticeable as it probably should be in planes with slats, as you can keep near complete roll control in what's almost a falling-leaf maneuver. This also caused huge hissy-fits when we tried to test the Me-109 stall speeds.

What you want to measure is the minimum speed at which the plane's wings can generate enough lift to maintain 1.00G in straight and level flight. This is stall speed... although it may not be the speed at which the plane stalls if you're at an odd attitude. (What speed will a plane stall at if pointed straight down?) </div></BLOCKQUOTE>

http://forums.ubi.com/images/smilies/351.gif
Though load conditions should also be specified. Stall speed at max takeoff weight is a great deal higher than stall speed minus munitions and all but emergency fuel reserve.

Skunk, AoA at stall varies very little with speed and only at low speeds does power make a difference. Power doesn't actually change the stall angle of attack, it changes the direction of the airflow over the wing roots and consequently reduces the local AoA over that part of the wing thus delaying the time at which more than just the wing tips are stalled.

As speed reduces the AoA required to maintain 1G lift and keep the aircraft flying level increases. Stall speed is defined as the speed at which the angle of attack required to maintain lift equals the stall AoA with power off or at idle. Flying at lower speeds results in the wing not being able to maintain enough lift for level flight, flying at higher speed results in a lowerr angle of attack and moving away from a stalled condition.<div class="ev_tpc_signature">

<center>
http://jennirivers.actewagl.net.au/sig.jpg
SST X-45 profile (http://jennirivers.actewagl.net.au/fb.zip) | SST X-52 Profile (http://jennirivers.actewagl.net.au/fbx52.zip) | Joysticks & IL2/FB/PF (http://www.airwarfare.com/tech/sticks.htm) | IL2Sticks Utility (http://www.airwarfare.com/Sims/FB/fb_essential_files.htm#087)
Maddox Forums Moderator</center>

tools4foolsA
12-21-2006, 05:18 AM
Sounds difficult and time consuming to test.

How about real life stall speeds, anywhere a list what the stall speed of various aircraft is supposed to be?
****

XyZspineZyX
12-21-2006, 07:15 AM
You would most likely find that kind of info in the pilots manuals for each particular plane.<div class="ev_tpc_signature">

http://i48.photobucket.com/albums/f239/Skunk24/sig2.jpg
Escadron virtuel RCAF 438 (http://438cityofmontreal.googlepages.com)
<span class="ev_code_red"> Are you from Montreal? French is good? JOIN US! RCAF 438 "The City of Montreal"</span>

"You know, I've personally flown over 194 missions and I was shot down on every one. Come to think of it, I've never landed a plane in my life."

tools4foolsA
12-21-2006, 08:59 AM
Great!

Now where do I find the pilot manuals?
*****

IL2-chuter
12-21-2006, 09:23 AM
Stall is where the upper wing boundary layer breaks away from the wing effectively killing all lift for the stalled section of wing. Best stall performance is achieved by not having the whole wing stall at once. Slats (or slots) are usually only installed on flat wings (i.e. 109) for this reason. Stall speeds are often measured in specified power-on and power-off conditions at gross weight. Pretty simple, really. As a flight student stalls and their recognition are the first things learned. They, and their cousins spin and snap, are usually very easy and sometimes quite fun.

Game stalls are a little goofy . . . http://forums.ubi.com/images/smilies/16x16_smiley-indifferent.gif


http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif<div class="ev_tpc_signature">

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^

"I fly only Full Real in Il2 Forgotten Battles." -Mark Donohue

FritzGryphon
12-21-2006, 06:44 PM
I found this detailed chart on a NASA site. It was found in Chuck Yeagers pocket after his fatal crash, sat in the back room of a museum for 74 years, and has now been digitally remastered into this picture.

http://members.shaw.ca/evilgryphon2/stall2.bmp

Treetop64
12-21-2006, 09:50 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by tools4foolsA:
Great!

Now where do I find the pilot manuals?
***** </div></BLOCKQUOTE>

At the store. http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif

Seriously, try googling it, using the aircraft type in question and typing in "performance charts" and "stall speeds".<div class="ev_tpc_signature">

------------------------------
"It breaks my heart, but I am almost certain that raaaid will get the Nobel Prize in physics before we get the Avenger in PF."
-- Zeus-cat
------------------------------

NonWonderDog
12-21-2006, 09:52 PM
Just because I'm an anal-retentive bastidge, this is what a lift curve more typically looks like.

http://img.photobucket.com/albums/v226/KnowNothingBozo/liftcurve.jpg

You don't usually see the stuff past 25 degrees or so because it's utterly useless and probably wrong. And no, I don't know why there's a second peak either.

IL2-chuter
12-27-2006, 09:59 AM
OOO OOO OOO http://forums.ubi.com/images/smilies/16x16_smiley-happy.gif


The first peek is basically from Bernoulli lift (from the cambered shape) and the second is from Newton (or reactive) lift (from the Angle of Attack).


class dismissed http://forums.ubi.com/images/smilies/16x16_smiley-very-happy.gif


Good question, NonWonderDog.<div class="ev_tpc_signature">

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^

"I fly only Full Real in Il2 Forgotten Battles." -Mark Donohue

NonWonderDog
12-27-2006, 10:44 AM
http://forums.ubi.com/images/smilies/clap.gif That's it!


Really, though, it's something to do with just being a big dumb obstruction to the flow. At high enough angle of attack, the wing is a big barn door that gets blown around just by the dynamic pressure. As to why this creates enough lift for a second peak so close to the first, I've never been able to figure that out. Sure, the surface normal is inclined to the flow, but that can't be all the effect.

I did do that one up in paint, but only because it takes far too much time to make that kind of picture in xfoil or something similar. The solution tends to be numerically unstable at very high angles of attack unless you give it a very good approximation to start with...which means stepping through angle of attack by 0.1 degrees or so, and even then it likes to diverge wildly. It does usually look like that, but it changes a hell of a lot depending on airfoil shape. I should probably try the 3d wing modeller at very high angle of attack to see what happens, but I don't have easy access to it here on vacation.