Performance Comparison: Yakovlev Fighter Family - Page 2 - Aircraft of World War II

HoHun · 03-27-2009, 07:05 PM

Hi again,

Here a new comparison including the Yak-9U, based on the power graphs from Stepanets with the high-altitude modification according to the "atmospheric pressure" rule mentioned above.

The Yak-9U is supposed to have a VK-107A running at 3200 rpm. In the absence of data I had to guess the reduction gear ratio and decided on a nice round 0.5, which is not untypical for engines of the era and matches the physical parameters of the Yak-9U fairly well. I'm using the drag data from the Yak-9D for the Yak-9U, and except for an apparently somewhat too high full-throttle height which is inherent in the power graph from Stepanets' book, it more or less matches the data from the Tsagi comparison graph posted by Timppa, so I think it's a good first try :-)

Comments and suggestions are welcome!

Regards,

Henning (HoHun)

HoHun · 03-27-2009, 07:06 PM

Oh - not to forget the attachments:

kozz · 11-07-2009, 08:08 AM

Do any of you know of any numbers on yak-3's corner speed?

(not turn rate, but the speed at which that rate is achieved)

Just for low altitude is all (IL-2...) Not knowing the corner speed has got me pwned in a few flat scissors from having to guess.

or what the Russians call "corner speed," maybe... I speak Russian well enough to ask them but I don't know the exact term, unless it's just лучший скорость угла or something.

VG-33 · 11-07-2009, 03:33 PM

Quote:

Originally Posted by kozz

Do any of you know of any numbers on yak-3's corner speed?

(not turn rate, but the speed at which that rate is achieved)

Just for low altitude is all (IL-2...) Not knowing the corner speed has got me pwned in a few flat scissors from having to guess.

or what the Russians call "corner speed," maybe... I speak Russian well enough to ask them but I don't know the exact term, unless it's just лучший скорость угла or something.

350-360 km/h at 1000 m height from Yak-3 manual, probably erroneous from the mainstream (19-20s)

320-340 km/h from russian forums, recalculated by modern confirmed engineers (~18s) with Yak-3 polars and other aerodynamical parameters i don't have.

kozz · 11-09-2009, 02:33 AM

Quote:

Originally Posted by VG-33

350-360 km/h at 1000 m height from Yak-3 manual, probably erroneous from the mainstream (19-20s)

320-340 km/h from russian forums, recalculated by modern confirmed engineers (~18s) with Yak-3 polars and other aerodynamical parameters i don't have.

thanks... I tested it in il-2 to get a ballpark figure and came up with approx 350kph... I'm glad that's accurate enough cause the turn rate in IL-2 isn't, I could go full circle in about 11 or 12 seconds

do you have a link to the manual... I would like to RTFM

<> never mind that, I see the manual was on this site, спасибо очень

Civettone · 11-09-2009, 03:31 PM

I am surprised the Yak-3 turn rate wasn't better than that of the other Yaks ...
It seems it was nothing more than a lightened and cleaned up Yak resulting in higher speed and better climb rate. A bit like the La-7.

Kris

Altea · 11-10-2009, 06:10 AM

Quote:

Originally Posted by Civettone

I am surprised the Yak-3 turn rate wasn't better than that of the other Yaks ...
It seems it was nothing more than a lightened and cleaned up Yak resulting in higher speed and better climb rate. A bit like the La-7.

Kris

Hello Kris

I don't undersant why do you say that. The Yak-3 (17-19s) was a better turner than a Yak 7 or 9. Those being the heavy line of Yak family fighters.

But serial 1943's Yak-1 was weghtning from 2795 to 2885 kg that means 163 to 168 kg/m² WL. Some lightening ones had even less than 157 kg/m² wing load.

Serial Yak-3 had a WL of about 182 kg/m. (178 at best).

So the best "modern" soviet turners were the small batches of specially lightened Yak-1 (16-17s).

Regards

Civettone · 11-10-2009, 07:00 AM

I am simply looking at the graph. I would think the advantage here would be clear but it seems the sustained turn rate is very close to that of the yak-1b of 1942 and that of the Yak-9. The Yak-3 is always portrayed as the ultimate Russian dogfighter.

But perhaps it's the combination of instant turn rate, acceleration, roll rate and most of all speed which made it superior in dogfights. So thatmay be what you are referring to when mentioning the wing load?

But looking again, I see that the Yak-3 was the best below 1000 m which is also very important.
Kris

11-07-2009, 08:08 AM	#18
kozz Junior Member Join Date: Nov 2009 Posts: 2	Do any of you know of any numbers on yak-3's corner speed? (not turn rate, but the speed at which that rate is achieved) Just for low altitude is all (IL-2...) Not knowing the corner speed has got me pwned in a few flat scissors from having to guess. or what the Russians call "corner speed," maybe... I speak Russian well enough to ask them but I don't know the exact term, unless it's just лучший скорость угла or something. Last edited by kozz; 11-07-2009 at 08:12 AM.

11-09-2009, 03:31 PM	#21
Civettone Senior Member Join Date: Oct 2005 Location: Limburg Posts: 1,225	I am surprised the Yak-3 turn rate wasn't better than that of the other Yaks ... It seems it was nothing more than a lightened and cleaned up Yak resulting in higher speed and better climb rate. A bit like the La-7. Kris __________________

11-10-2009, 07:00 AM	#23
Civettone Senior Member Join Date: Oct 2005 Location: Limburg Posts: 1,225	I am simply looking at the graph. I would think the advantage here would be clear but it seems the sustained turn rate is very close to that of the yak-1b of 1942 and that of the Yak-9. The Yak-3 is always portrayed as the ultimate Russian dogfighter. But perhaps it's the combination of instant turn rate, acceleration, roll rate and most of all speed which made it superior in dogfights. So thatmay be what you are referring to when mentioning the wing load? But looking again, I see that the Yak-3 was the best below 1000 m which is also very important. Kris __________________

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03-27-2009, 07:05 PM	#16
HoHun Senior Member Join Date: Oct 2006 Posts: 1,765	Hi again, Here a new comparison including the Yak-9U, based on the power graphs from Stepanets with the high-altitude modification according to the "atmospheric pressure" rule mentioned above. The Yak-9U is supposed to have a VK-107A running at 3200 rpm. In the absence of data I had to guess the reduction gear ratio and decided on a nice round 0.5, which is not untypical for engines of the era and matches the physical parameters of the Yak-9U fairly well. I'm using the drag data from the Yak-9D for the Yak-9U, and except for an apparently somewhat too high full-throttle height which is inherent in the power graph from Stepanets' book, it more or less matches the data from the Tsagi comparison graph posted by Timppa, so I think it's a good first try :-) Comments and suggestions are welcome! Regards, Henning (HoHun)