How on earth do you fight a Yak-1

[216th_Jordan]

The decrease is simply coming from the increased lift vector which will influence you flight vector. Lets say in level flight at 200kph you have an AoA of 10°, now you lower your flaps, your critical AoA decreases but as your wing produces more lift you will need a lower AoA to maintain level flight. 

 

I'm not an aeronautical engineer neither but my technical mechanics lectures made me appreciate angles and forces

Btw as we have Tacview now this can easily be verified or proven wrong, I'd be interested.

[9./JG27DefaultFace]

Ahh I see what you're saying now. Yes to hold level flight you would need to lower your AoA. That isn't an effect of the flaps though. That's you lowering flaps, observing that you are now climbing and then pushing the stick forward to lower the AoA. If you left the stick where it was the AoA would not decrease and you would continue to climb.

[6./ZG26_5tuka]

Now what I'm not sure about (which someone who has more knowledge of Cl v Alpha curves than I do can gladly correct) is if the angle in the Cl v Alpha diagram with flaps down is still in reference to the non flaps chord line and the relative airflow or if it is then adjusted for the changed chord line when dropping flaps. To me doing the latter would seem to be comparing apples to oranges.

The critical AoA is usually referring to the wing's root profile chord line (like you said, anything else wouldn't make much sense for a comparison).

Edited June 30, 2017 by 6./ZG26_5tuka

[216th_Jordan]

Ahh I see what you're saying now. Yes to hold level flight you would need to lower your AoA. That isn't an effect of the flaps though. That's you lowering flaps, observing that you are now climbing and then pushing the stick forward to lower the AoA. If you left the stick where it was the AoA would not decrease and you would continue to climb.

 

Hehe, it's twisted Well if I would NOT lower to nose to keep the flight level the AoA would still decrease as my plane would climb now while still having the same angle (pitch) against the horizon (= lower AoA).

Edited June 30, 2017 by 216th_Jordan

[9./JG27DefaultFace]

@5tuka Thanks for the clarification!

 

 

Hehe, it's twisted Well if I would NOT lower to nose to keep the flight level the AoA would still decrease as my plane would climb now while still having the same angle (pitch) against the horizon (= lower AoA).

 

AoA =/= Pitch. It is the angle between relative airflow and the Chord line (Leading edge to Trailing edge of a wing) not the horizon. I guess I see what you're saying. The vertical component of airflow in the climb... My gut would tell me that that is a very small amount compared to the airflow from the front. I also don't think that it would have as much of an effect in a hard turn as it would in level flight as you are describing.

[216th_Jordan]

@5tuka Thanks for the clarification!

 

 

 

AoA =/= Pitch. It is the angle between relative airflow and the Chord line (Leading edge to Trailing edge of a wing) not the horizon. I guess I see what you're saying. The vertical component of airflow in the climb... My gut would tell me that that is a very small amount compared to the airflow from the front. I also don't think that it would have as much of an effect in a hard turn as it would in level flight as you are describing.

 

The effect should be the same in a turn or level flight. I chose the level flight example because the pitch equals AoA in this case. Now if you keep the pitch but are climbing the new AoA would be 'pitch - arctan(climb(m/s)/speedabove ground(m/s))'. Just as an example: If you fly 200kph thats ~55.5 m/s, now lets assume that full flaps would give you 5 m/s climb (we don't factor drag/more power used into that here). So the equation would turn out 'Pitch - arctan(5/55.5) = AoA = 4.85°' The use of flaps has lowered your AoA by 5.15°. 

 

Now this is just general theory. In order to prove anything we would need charts of those AoA/lift profiles for the Yak-1 especially and also how much lift they would add - that is something I don't know.

[Ribbon]

@5tuka Thanks for the clarification!

 

 

 

AoA =/= Pitch. It is the angle between relative airflow and the Chord line (Leading edge to Trailing edge of a wing) not the horizon. I guess I see what you're saying. The vertical component of airflow in the climb... My gut would tell me that that is a very small amount compared to the airflow from the front. I also don't think that it would have as much of an effect in a hard turn as it would in level flight as you are describing.

Same as with flaps retracted, airflow remains but weight/lift ratio changes. Weight center on plane moves. Edited June 30, 2017 by redribbon

[9./JG27DefaultFace]

Yes but he is referring to the change in velocity vector as a result of increased lift. Ie the relative airflow changes.

 

I agree in theory its correct but I don't think this effect is as big as you think it is. As you say we would need numbers to be sure. I get that it's an example but 5 degrees seems extreme to me. I don't think it would be enough to counter the effect of reduced Critical AoA which in 5tuka's example is 6°.

 

I would also say that once you decrease AoA, you decrease lift, which would then arrest any sort of upward movement you have and increase AoA again. I would guess this turns into an oscillation which stabilizes somwhere in the middle. Still I think the effect is minimal, and also very different when applied to a max rate turn near critical  AoA than it is in level flight or a less aggressive turn.

 

Are there Cl v Alpha curves for a Yak somewhere? Or anything in the Flight manual regarding G limits for flaps as Kwiatek said? 

Edited June 30, 2017 by 9./JG27DefaultFace

[Finkeren]

My faith in this thread has been restored. This is great stuff guys. So good to see, that some are better than me at keeping it civil and to the point.

Edited June 30, 2017 by Finkeren

[216th_Jordan]

An here is what makes the difference where non dynamic flight models succomb as they don't even feature such an effect:

 

In power off flight your observation is quite true and flaps out gives only a marginal advantage (it still offers greater lift = tighter turn) but with power on the flaps will have a big effect. In normal flight condition with flaps up AoA for propwash is very small, the thrust component remains very strong. Now with flaps out the new (imaginary) chord line for the propwash effect increases this AoA drastically, this means that the propwash wingarea will produce a significant higher amount of lift than it did before. Give it a try really, those 1300 HP infront really make the difference in the end.

 

 

I think now almost all has been said, we will see what will change with the new FM but the general behavior should be right from my perspective. 

I'm enjoying the discussion though!

My faith in this thread has been restored. This is great stuff guys. So good to see, that some are better than me at keeping it civil and to the point.

 

It's tough sometimes, I know

[9./JG27MAD-MM]

When you reach the critical Area of AOA the stream over the upper Surface of the Wing will disengage there only small amount of Wing area that affected by any sort of Prob wash, without any lift you go nowhere only on the Wings will drop.

In addition there plenty of reports by P-51 pilots of WW2 that small amount of Flaps will slightly increase the turn time by reasonable Drag and AOA limit, so why they don't fly with 50 Degrees of flaps down?

And Japanese developed butterfly Flaps they increase the Wing area for manoeuvring combat?

[216th_Jordan]

Well as I said those full flaps are only usefull for very short time scenarios, usually extending the flaps does not help you a lot (I speak from experience here). What matters most in a turn fight 1v1 is usually turn-radius rather than turn time. (thats why turnfights are so bad) In grouped combat such a behavior is certain death and the reason why nobody would really extend flaps and get cough in a slow speed turnfight at minimum speed where the controllability of your plane is severely hampered. 

 

But If flaps would not make slow speed handling easier they would not be used on airplanes in the first place.

 

Btw: Enough chit-chat from me now 

Edited June 30, 2017 by 216th_Jordan

[9./JG27DefaultFace]

I have to say I also don't understand your argument with the prop wash. As I understand it, the airflow over the wing needs a certain amount of 'energy' to make it over the wing without separating. As you increase the AoA it becomes more difficult for the airflow to follow the surface of the wing all the way to the trailing edge and will eventually separate, causing a stall. Like rolling a ball uphill, eventually if you make the hill steep enough the ball will roll back down the hill instead of going over the top. That isn't really a scientific explanation and if someone can explain it better please go ahead.

 

Now at low speed, High AoA, and full power the airflow behind the propeller is just barely making it over the hill so to speak. When you drop the flaps (especially split flaps, with a large deadzone behind them to the trailing edge) you are making it harder and harder for the airflow to make it over the wing. Like adding a big bump somewhere in the hill. If I'm already at the edge of a stall, and I drop flaps, with or without prop wash, I haven't somehow imparted more energy into the airflow. The air coming off the prop isn't sped up by lowering flaps. That just doesn't make sense to me.

 

I'd also have to disagree about how useful they are. Like I said I've tested it extensively with MAD and David, as well as on the Berloga server. I find them very useful. Particularly when things start to get slow or I want to really pull out an angle all at once I often pop them out for at least a few seconds.

 

I'm also not sure what you mean by 'Handling'. Flaps are used on aircraft to lower the safe landing speed. You produce more lift at the same AoA, so you can get slower than you could without them.

[216th_Jordan]

 

Now at low speed, High AoA, and full power the airflow behind the propeller is just barely making it over the hill so to speak. 

 

The angle of attack over the propwash wing area will be a lot smaller than over the rest of the wing (combined normal airflow vector + propwash airflow vector), thats why with power on the wingroots barely stall. As far as my understanding reaches a stall is the loss of airflow over the upper surface of the wing. The flaps will induce a lot of drag and turbulence below and aft of the wing.

 

I absolutely believe that your statements are true and once you are infront of a yak-1 he has not got too much trouble to make a shot at you in many cases. I just don't feel that it invalidates what I said. I think part of the feeling that what happens is totally unrealistic comes from comparing findings from other sims with this one. The problem I would think is that just no other sim except X-plane is having such flight dynamics.

 

All that being said I know the planes generally behave a bit sketchy sometimes, but in my eyes that comes less from flaps and more from too much agility/ ability to pull angles / control responsivness at low speeds. (the 109 suffers a bit here)

Edited June 30, 2017 by 216th_Jordan

[9./JG27DefaultFace]

Sure. But what you say proves only that the part of the wing affected by the prop wash will stall later. Agreed.

 

However, if that part is on the edge of a stall without flaps, it will be on the edge of a stall with flaps as well. The flaps don't change the effect of the prop wash.