La-5 FN Stall angle of attack in flight

[Roland_HUNter]

Hello everyone!

Can somebody explain me, why the LA-5 FN has Stall angle of attack in flight configuration: 22.2 ° ? Better than Po-2 or anything else in the game.

What kind of thing give this attribute  for the LA-5 FN?

[MikhaVT]

The La-5 series of aircraft has leading-edge slats which deploy when approaching a stall. If you hop into an La-5 in QMB and set starting alt to ~6000m then reduce power holding level flight you'll end up in a stall. On the LaGG-3 (what the La-5 is based on) this would end up in a rather violent spin, but with the La-5 it'll drop a wing slightly, if you release back pressure on the stick it'll then nose down a bit and gain speed until it's below it's stall AoA and recover without ever entering a spin. My attempts to induce a spin in the La-5 have resulted in getting a very lazy spin developed, but the second i release the controls the aircraft returns to controlled flight. 

[Roland_HUNter]

Bf-109 is lighter and has leading-edge slats aswell, but it has only 19.8° MAX.

[MikhaVT]

3 minutes ago, -[HRAF]Roland_HUNter said:

Bf-109 is lighter and has leading-edge slats aswell, but it has only 19.8° MAX.

Likewise, the LaGG-3 is lighter, with similar wing design to the La-5 and only has an 18° stall AoA. The weight isnt much of a factor for this case -- the 109 G6, G14, and K4 DC all have 19.8° stall AoAs and are heavier than the La-5, while the G4 and G2, are slightly ligher with the same 19.8° AoA. 

 

Stall AoA is all in the wing designs, as we can see the 109 E7 has a stall AoA of 20° and has more boxy wings. To really get to the bottom of this we have to go a bit into aero/fluid dynamics. An aerodynamic stall occurs when the air moving over the wing separates from the wing. This severely drops the lift produced by the wing and lets the aircraft fall out of the sky. If a standard wing shape is taken and the leading edge of it is "thickened" a bit then the wing's stall AoA will generally increase while also increasing the drag. Slats work by doing this only when needed by adjusting the geometry of the wing. Effectively they work to obtain the same results as flaps do, but on the front of the wing instead. 

[AndyJWest]

9 minutes ago, -[HRAF]Roland_HUNter said:

Bf-109 is lighter and has leading-edge slats aswell, but it has only 19.8° MAX.

 

The stall angle depends on airfoil form and Reynolds number,  not weight. And the Bf 109 has a higher wing loading. As for why the difference, do we know what datum the angle is measured relative to? 

[Roland_HUNter]

So the LA-5 Fn has more than CLmax 2? Nice...

ANd the AoA topic says  " The critical or stalling angle of attack is typically around 15° - 20° for many airfoils. "
So the LA-5 FN is "hold my beer" and I ll be better than avarage?

Pretty funny...:

 

Fig. Shows the cross section of a wing of a plane.

The axis of the wing shown by dotted line is called chord.

The angle between chord and wind direction is called angle of attack.

The figure also shows the air- stream lines.

The pressure force arising according to Bernoulli's principle is denoted by P.

For a given wind speed, the lift ,P cos ( theta) increases with the angle of attack up to certain limit. Beyond this it starts decreasing .

This limiting value of angle is called stalling angle and it's value varies from about 15 to 20 degree.

Note that L= P cos ( theta) is lift and D=P sin (theta) is drag.

The ratio lift/ drag is maximum when the angle of attack is about 4 degree.

Therefore , we have maximum efficiency of flight at this angle of attack.

Normally, the angle of attack is adjusted between 3 to 6 degree.

 

So it would be awesome to see the historical sources for tha LA-5 FN.

[Blackhawk_FR]

Curious to know the answer. May be the wing profile? Really don't know. 

 

What I know is that even with this 22° stall angle, it's still quite bad at low speed dogfighting, so...

[Roland_HUNter]

1 hour ago, F/JG300_Faucon said:

Curious to know the answer. May be the wing profile? Really don't know. 

 

What I know is that even with this 22° stall angle, it's still quite bad at low speed dogfighting, so...

He can pull after you when your wing is stalling, he can pull more in turns. And it has better glider characteristics.

Edited January 17, 2020 by -[HRAF]Roland_HUNter

[-=PHX=-SuperEtendard]

Clmax varies depending on the airfoils. At the same angle of attack one type of wing can have very different Cl than a different type of wing.

The La-5FN stalls at a higher speed than the 109 while having a larger wing, this points towards a lower Clmax.

In game tests are a bit complicated, but I more or less came up with 1.72 Clmax for the Bf 109 G-2 (stalling at 150 kmh at idle) and 1.44 Clmax for the FN (stalling at 165 kmh at idle). Mind you there would be some errors as these tests aren't perfect but they show a rather big difference between the plane's wing performances.