Yak-1 flaps down arcadish behaviour?

[novicebutdeadly]

I would expect dumping your flaps down to achieve a better turn ratio for 1 turn if done purely in the horizontal or several turns with the nose pointing down to keep the energy loss to a minimum.

I would also expect to see the plane to bleed energy faster due to the added induced drag that the flaps are causing.

To have a sustained tighter turn would require the plane to have a significant power to weight ratio which few ww2 planes had (to be able to sustain a full flaps down tight turn purely in the horizontal).

Depending on peoples results (I don't fly Russian aircraft/ rarely fly the 190) I would expect to see a plane that can dump the flaps down (not the 109 that has the flap wheel) to be able to momentarily tighten their turn if they dumped the flaps at the right moment (too early should damage the flaps, too late and you reduce the benefit), and if they want to keep that sustained tight turn they would need to have the nose pointed down, or they would bleed alot of energy resulting in their turns becoming very wide to prevent stalling.


From my own in game experience in QMB (hard to find a server with people on it, let alone one with people and a low ping), I have managed to out turn every Russian fighter even in a slow merry-go-round turn fight.

And only needing a small amount of flaps (if any) to be able to do it. The simple reason is that if you turn with flaps you need to keep the nose either horizontal or pointed towards the ground. Whereas the AI tries to do full flap climbing turns   

All I need to do is keep my nose at a lower angle and it's only a matter of time.

With Flaps they bleed more energy than me (not as much as they should) making their turns wider and wider, reducing my need to even use flaps.   


 

Edited April 28, 2015 by novicebutdeadly

[6./ZG26_5tuka]

Your point about flaps is not valid. Combat flaps are designed for the purpose you describe but landing flaps are a totally different story.

 

While combat flaps are somewhat between 1 and 10 degree of deployment landing flaps usually are around 40 - 45 degrees.

 

That does not mean they produce more lift than combat flaps at all, on some aircraft its even the contary due to air disturbtion.

 

Before moving on lets point out some characteristics of landing flaps:

- lower to same lift as combat flaps

- very high drag

- highly reduces the planes crit AoA.

 

Especiay the latter is important. Many planes in WW2 were reported to havevicious stall characteristic with flaps fully deployed compared to basic flight configuration.

 

If you flaps are fully deployed turning is barely more than a wet dream. Thats why real pilots spend so much attention before landing since once your throttle is cut and flaps extended you're a sittimg duck.

 

In addition to the aerodynamical limitation structural stress also plays a role. Turning the aircraft tightly at cruise speed with fuy deployed flaps would cause serious damage to the mechanism and / or wing.

 

I for one wouldnt expect structural damage to the wing to be modeled primarily in BoS but the aerodynamical effects of deployed flpas configuration (drag, lift, reduced crit AoA).

 

Cant test it atm in BoS just contributing to the aerodynamical explaination of the actual issue.

Edited April 28, 2015 by Stab/JG26_5tuka

[MK_RED13]

Easy test... take Yak 1 with 40% fuel.. start the engine.. throttle to full power.. start.. climb to 1k, (2k, 3k, 4k... doesn't matter).. meet with friend in 109F4 (40% fuel too) and start to fight.. first without flaps.. and after that use flaps.... you will see the difference..

 

S!

 

BoM I bought because I still hope ..  

[303_Kwiatek]

Hope for next redmatrix

[Bearcat]

There are some obvious performacne of planes errors in BOS which i think are rather easy to fix   (  Yak-1/Lagg-3 and F-4 high alts overperformacne, Yak-1 flaps arcadish behaviour)  but there is no will to do it.  People just want that these sim will be simulator based on realistic flight model phycics and historical performacne of planes casue these game have potential to do it. For some reasons there is not too much will to do it.

 

Thats why i decided to not buy BOM. I dont like balanced game. But these is my chooice.

 

Not in topic but you are free to write in ATAG forum about flight model or performance issues and i think nobody will ban you for that.  There are some general limitations in CLOD regarding take off and landings characteristic but these is general problem for all planes in game. At least performacne of planes are based on historical accuracy.  There is no any side bias there.

 

There is no side bias here either..  People here get banned for the same types of stuff.. insulting other forum members or developers.. Intentionally antagonizing folks either with thier posts or their sigs.. that they have always gotten banned for. Having issues with features in BoS.. or the lack thereof is not one of them.

[busdriver]

Your point about flaps is not valid. Combat flaps are designed for the purpose you describe but landing flaps are a totally different story.

 

While combat flaps are somewhat between 1 and 10 degree of deployment landing flaps usually are around 40 - 45 degrees.

 

That does not mean they produce more lift than combat flaps at all, on some aircraft its even the contrary due to air disturbtion.

 

Before moving on lets point out some characteristics of landing flaps:

- lower to same lift as combat flaps

- very high drag

- highly reduces the planes crit AoA.

 

Especiay the latter is important. Many planes in WW2 were reported to have vicious stall characteristic with flaps fully deployed compared to basic flight configuration.

 

If you flaps are fully deployed turning is barely more than a wet dream. Thats why real pilots spend so much attention before landing since once your throttle is cut and flaps extended you're a sittimg duck.

 

Suffice to say, I think you dismissed "novicebutdeadly" too easily or did not read it carefully. This very old RL fighter pilot found his/her post to be spot on.

 

Your assert that: Before moving on lets point out some characteristics of landing flaps: - lower to same lift as combat flaps

 

I am unable to find anything that supports that assertion in my copy of Aerodynamics for Naval Aviators. I cannot find anything that would lead me to think the Power Required curve and the Lift curve simply remain the same whilst changing the shape (camber) of the wing. If that is what you teach in university or were taught in your aerodynamics degree, I'm in trouble.

 

Should I interpret your remarks to say therefore, the stall speed with combat flaps and landing flaps will be the same?

 

Am I wrong to think if the stall speed with Landing flaps is slower than with Combat flaps, therefore the Lift curve shifted and in fact lift increased?

 

Help me understand your remark below, specifically in term of the fighters in BoS?  I'm not concerned about examples like the Corsair's problems around the boat, but just the fighters in BoS.

 

Many planes in WW2 were reported to have vicious stall characteristic with flaps fully deployed compared to basic flight configuration.

 

I'm always willing to be educated.

Edited April 29, 2015 by busdriver

[6./ZG26_5tuka]

Most flaps show only slight increase of lift if they are full deployed but a radical increase of drag. If you have ever flown with a single engined aircraft deploying flaps during approach you certanly remember the sinkrate increasing rapidly once flaps are out.

 

Second, I sayed on some planes it could lower lift due to creating tubulences. That does certainly not account to all aircraft but some (very general statement as I can't recall any specific plane having this).

 

And yes full flaps stalls are the most nasty ones. It's the easiest way to kill yourself. Usually planes will enter a vicious flat spin that way.

 

I'm not a master of aerodynamics either though as a pilot myself I do have some practical and theoretical knowledge of aerodynamics. I'm equally open to learn new things everyday.

Edited April 29, 2015 by Stab/JG26_5tuka

[busdriver]

I have a couple hundred hours in SEL airplanes (including 500 in the F-16A) out of my 16,000 hours. I was not aware of any airplane that loses lift by extending flaps. I was taught turbulence generated by Lift is increased Drag and not decreased Lift. That's what military pilot training teaches.

 

Well if you hold the opinion that full/landing flaps only show a slight increase in lift, what was the flap setting when you performed your Slow Flight maneuver for your flight test? I had to use Full Flaps. 

 

It has been my experience that going full flaps and adding power has always allowed me to fly slower and maintain altitude (as long as you remain out of the Region of Reverse Command). It seems to me, this demonstrates that Lift has increased.  The corollary to this demonstration is at some Gross Weight, or Altitude, or Bank Angle or Temperature (or combination of these) I could find myself with full flaps and full power but unable to maintain altitude.

[JtD]

Depends on the angle of flap. Within parameters usually used on WW2 aircraft, maximum flaps are often close to maximum lift coefficient obtainable, and have sharper stalling characteristics than in clean configuration. See for instance the attached 1935 research report, pages 617 and 618. Fairly typical. It should be remembered that both, increased lift and stall with the sharper characteristics, would occur only in the wing section equipped with flaps, so aircraft behaviour can be quite different from what a look at the flaps-airfoil characteristics might suggest..

1698.pdf

Edited April 30, 2015 by JtD

[busdriver]

Uhhh JtD...whose post are you addressing? I'm not following your opening line, "Depends on the angle of flap." My apologies if you're posting on a different point of discussion, I'm specifically challenging 5tuka's notion that a given landing flap setting provides the same or less lift than a combat flap setting.  

[JtD]

I'm addressing the point "combat flaps lift vs. landing flaps lift" as much as the point "I'm not aware of any aircraft that loses lift when extending flaps". First point, as a general statement, is wrong, second point, as a general statement, is right. However, the finer details of both statements depend on the finer details of the aircraft configuration, in particular the angle of flaps used. Sorry for having started typing somewhere in the middle of my thoughts - basically I just wanted to add the pdf to the discussion, so whoever is interested in more than a general statement, can take a look.

[busdriver]

JtD that is a very interesting PDF. I indeed agree that the finer details of aircraft configuration (as you say) frame the conclusion regarding the veracity of a statement. I stand by the statement concerning combat flaps lift curve versus landing flap lift curve. Because one would be making a terrible error IMO to imply or infer any flap setting less than the maximum somehow qualifies as "combat flaps." Very few aircraft had a combat flap setting. And as far as I can tell (subject to you pointing out the error of my ways) in those few airplanes that used combat flaps, that setting was fairly modest (read that to mean the first notch or increment). The pedant in me must point out I'm talking about trailing edge devices when I say combat flaps.

 

The one that jumps out at me is the P-38J, and the addition of dive (AKA combat) flaps came as production neared 5000 airframes, and these were primarily to counter compressibility. I think I have a fairly decent library of 400+ air combat titles (principally WWII) but can't recall major technical discussions or anecdotes about the use of combat flaps.

 

The Lift Curves for the Handley Page Slotted Flap do indeed show a lower CL at the highest flap setting. I wouldn't use that as evidence that my statement about combat flaps versus landing flaps is wrong. I don't know of any WWII fighters were fitted with this flap system. Fairey Barracuda (Torpedo Bomber) had slotted flaps/dive brakes, but I don't think it had a combat flap setting. I'm operating under the impression there were ZERO fighters with combat flaps at the time of this study.

 

Hope that helps.

Edited April 30, 2015 by busdriver

[150GCT_Veltro]

Bump!

 

Kwiatek is right, this feature must be checked at least. I don't thik however it's an arcadish feature but a bug or other.

 

An official answer would be welcome.

Edited May 1, 2015 by 150GCT_Veltro

[II/JG17_HerrMurf]

I am in complete agreement about the flaps issue but when has attempting to corner the Devs with, "an official answer would be nice," ever paid dividends?

 

Make your concerns known here and with data in the appropriate thread but enough of the baiting tactics already.

Edited May 4, 2015 by HerrMurf

[6./ZG26_5tuka]

And how you think it can be shown with data? Because I for one have no spare Yak wing profile in both flap configurations and a high rated aerodynamical simulation tool to determine the variables.

 

Even if I could, how shall this help us to disprove the ingame's behaviour? To do that we'd need access to the FM files, be perfectly able to read and interpret each parameter and compare the faulted ones with ours. Not to mention a serious source comparison.

 

What I'm trying to say is that "All FM bugs need data backup" is not always true and a great way to just let people take it as it is, because theyve absolutely not enought inside view to disprove it (even with professional numerical data).

 

Checking, testing and eventually correcting found faults and misscalculations based on anecdotal feedback is also an essential part of FM development. Sure it's a lot of work and most claims don't meet the level of expertise to prove sth efficiently, Thats why it's easier to lean back and tell everybody to do his own job instead of trying to ressearch a certain behaviour more deeply (this by no means is meant as accusion to BoS devs).

 

If this continues flight sims will slowly degrade from what makes them great: Plausebility and (fact based) realism.

 

Don't take this personal Muff, not aimed at you, I'm just tired of people shutting down every FM thread with the same statement. Yes there are many FM issues. No, not all of them can be proven by the comunity. And no, saying "Prove it with data or leave it" does not help but expresses unwillingness to take notice in such a case.

Edited May 4, 2015 by Stab/JG26_5tuka

[II/JG17_HerrMurf]

It doesn't have to be Yak specific data. As I said I agree the Yak flaps issue is a problem. Bus and JtD are on the right track. My point is mostly about attempting to directly bait the Dev's into an argument in the forums which is rude and,historically, not gonna happen.

It doesn't have to be Yak specific data. As I said I agree the Yak flaps issue is a problem. Bus and JtD are on the right track with their generalized flap info. My point is mostly about attempting to directly bait the Dev's into an argument in the forums which is rude and, historically, not gonna happen.

[JtD]

In fact, the Yak has a ClarkYH wing profile and the details of the flaps configuration can be found in the technical description, which I am too lazy to check right now. It's not rocket science and I'm certain that any FM programmer worth his money will have no trouble getting the "should be" right. The "as is" is also quite obvious in game. So the only statement required from the devs would be "we're (not) looking into it". Not a public discussion of the issue as such. I don't think anyone was asking for more.

[II/JG17_HerrMurf]

I have argued for the inclusion of anecdotal FM evidence myself. Aircraft should perform to expectations of the community as a whole. We are generally well read on the subject. So, we are in agreement there. Data should be the basis for the FM's with the gray areas filled in by well founded expert opinion. On the other hand, I respect the Dev's disinclination to operate that way. Just listening to the loudest or most caustic voices would have them endlessly chasing their tails.

[6./ZG26_5tuka]

I wouldn't say one can draw clear conclusions about the exact FM error ingame without clear inside. Most forget about the virtual parameters and the overall nature of FMs (each parameter influrences a bunch of others).

 

I've seen issues like that due to wrong CoG or Cd modeling of the aircraft even in non flaps configuration, where it is less noticeably but becomes pregnant once you add the flap effect to it. In a worst case scenario multiple factors with slight variation each add up to a noticeable error.

I have argued for the inclusion of anecdotal FM evidence myself. Aircraft should perform to expectations of the community as a whole. We are generally well read on the subject. So, we are in agreement there. Data should be the basis for the FM's with the gray areas filled in by well founded expert opinion. On the other hand, I respect the Dev's disinclination to operate that way. Just listening to the loudest or most caustic voices would have them endlessly chasing their tails.

Agree not all claims are viable, indeed it's probably the minority. In this case nobody can investigate in the issue properly. The way I see it is the way you wrote above. We have many ambitious people being (semi-) educated about aerodynamics and history of those aircrafts not to mention some real pilots with exams. There probably is no such well informed and educated comunity in any other game category than in simulators, which is why critique is more sharp and technical by nature.

 

When I reported the Fw 190 taxi (bug)behaviour for example I couldn't prove it with calculations. Lack of data, lack of time. I still expressed my concern and underlined it with expirience in both game and real live n a serious matter. In such a case I would like sby to take notice and say "ok, we may look at this" or "your observations seem to be viable so we'll pass your report to our testers". if the answer is "No, you have no data to offer so your report doesn't bother me" you knwo sth is wrong on the other end.

 

A good example for comunication would probably be Yo-Yo from DCS forums. He's not only reading player's concerns but also takign crittique, data offers and sometimes explains people when and why they're wrong in their statements, That's more like FM comunication should work.

[II/JG17_HerrMurf]

I find Han incredibly abrasive but he does take notice and investigate. It just takes a fairly long thread to get them to move on most things. I suspect it has a bit to do with how much new content they are buried under and when they can spare some resources. They have to be pretty selective on which community concerns to focus on at the moment. The flaps are clearly, at least to many, not right. The kind of discussion we are having now has borne the best fruit with the Dev's. It is possible a parameter or two got missed which leads to the AC retaining too much energy with the flaps out but all of my time is in 152/172's so I don't have any experience with a surplus of E outside of sims.

[Dakpilot]

Some tracks showing the anomalies and a polite PM to Han would be a start.

 

However most FM debates/complaints seem to be based around the perception of historical bias or inference that the Dev's are stupid or lazy or create errors on purpose

 

It really is not surprising that they don't bother reading the posts in depth...add in the always present language barrier and occasional 'armchair pilot' misconceptions and you get the current result

 

Regardless of that they are probably working on it anyway...

 

Cheers Dakpilot

[MK_RED13]

Anyone testing Yak with full flaps down in loop? Just for fun, try this - starting speed 250km/h!!!!! FULL FLAPS DOWN, 100m alt ..... and GO to loop..

 

 

 

------------------------------

http://www.docdroid.net/gmjm/yak-manual.pdf.html

[MK_RED13]

http://www.mediafire.com/download/nr5bdriz3nvmrln/Tracks.zip

 

...really arcadish FM of Yak..

Edited May 11, 2015 by MK_RED13

[II/JG17_HerrMurf]

I'm actually way less concerned about the 'flaps out' performance than I am with their ability to fold them in and suddenly accelerate/climb with me when I didn't give up an E advantage and am already accelerating/climbing in a clean configuration. That seems less than realistic!

[mb339pan]

F4 can compete in maneuvered with the yak1 , I see many pilots do not use the right tactics servers with icons, not to mention that that is not the most suitable test
I saw many pilot with LA5 , personally I feared them more than Yak1

[II/JG17_HerrMurf]

-5 can also do the fold em up and accelerate thing as well. I'm a BNZ guy so I rarely give up the E advantage or turn extensively with my enemy. When I am caught from above I have no complaints and blame myself. Watching an aircraft pull his flaps in and suddenly start closing the gap after the overshoot while I am over 350-400 kph is a little silly.

[Dr_Molenbeek]

I don't want to be rude, but when i see the time that our devs take to fix an FM issue (when they listen, you know that's not always the case), and we have only 10 planes at the moment... I don't even want to imagine how it will be in the future...

[Dakpilot]

I don't want to be rude, but when i see the time that our devs take to fix an FM issue (when they listen, you know that's not always the case), and we have only 10 planes at the moment... I don't even want to imagine how it will be in the future...

 

 

May seem to be a long time, but there have been many fixes, and I really don't remember any other flight sim making quicker patches, quite the opposite in fact, maybe I have a poor memory

 

Cheers Dakpilot

[reve_etrange]

If anyone is unsure of how added camber should change lift and drag, NASA has a useful tool. (I know I have learned a lot this way).

[Dakpilot]

Did anyone actually send a proper report, as they have said they do not have time to read through pages of often unproductive arguments/comments

 

as asked pointed out by Dev's in post #37

 

Cheers Dakpilot

[Bert_Foster]

A couple of charts from RAF test document AVIA 6/2422 in the UK archives. These are on a study on the affects of flap on Spitfire Turn performance. Various flap angles were tested. The stuff shown here is for a flap angle of 30degrees. Spit flap was a split flap similar to YAK 1. this might be relevant to the current debate.

 

The Fan plots shown are similar to modern Fan plots (Dog house plots in US parlance). The "Line of zero climb " is effectively Ps=0 or the sustained turn performance boundary.

 

 

What can be seen is flap 30 does provide an improved sustained turn rate (smaller turn time). 

Taking the intersection of Ps=0 line with the lift limit gives a turn time clean of around 19secs (18.84deg sec).

Looking at the same point with Flaps 30 gives a Turn time of around 17secs (21.2 deg sec).

 

What can also be seen is that Flap 30 results in a reduction in Sustained G of 0.2g. i.e. Max sustained G Clean is 3.0g whilst with Flap 30 is around 2.8G

 

 Fan plot showing Flaps at 60deg and 85deg

 

one more chart

 

[NachtJaeger110]

 

What can be seen is flap 30 does provide an improved sustained turn rate (smaller turn time). 

Taking the intersection of Ps=0 line with the lift limit gives a turn time clean of around 19secs (18.84deg sec).

Looking at the same point with Flaps 30 gives a Turn time of around 17secs (21.2 deg sec).

 

 

If I understand this correctly then this is proof that the Yak1 flaps could indeed be modeled correctly . As PeterZvan in his tests showed, the improvement in sustained turn time given by the full flaps setting in the Yak is only 1.6 seconds; even less than the approx. 2 seconds shown in Fosters spitfire data... that puts this part of the Yak flap behaviour very well within the bounds of possibility and disproves a lot of people who claimed that more than a small degree of flaps could never decrese turn time.

Edited August 19, 2015 by NachtJaeger110

[6./ZG26_5tuka]

If I understand this correctly then this is proof that the Yak1 flaps could indeed be modeled correctly . As PeterZvan in his tests showed, the improvement in sustained turn time given by the full flaps setting in the Yak is only 1.6 seconds; even less than the approx. 2 seconds shown in Fosters spitfire data... that puts this part of the Yak flap behaviour very well within the bounds of possibility and disproves a lot of people who claimed that more than a small degree of flaps could never decrese turn time.

Look at the last graph. It shows how much altitude is being lost in a turn at constant speed with flaps deployed. The high drag of the flaps force the pilot to dive while turning to keep his speed (and as result his turn rate) up.

 

Also full flap deployment on the Yak is more than just 30° + it's mentioned that flap deployement influcrences sustainable Gs of the aircraft, which is not noticeably ingame.

 

The most critical part I see with the Yak's flaps is the barely if even existing change in AoA. It can turn at speeds well below corner speed with full flaps without fearing to stall due to pulling above crit angle of attacks.

 

Another glaring issue is the stall behaviour with full flaps. At a roughly 45° climb I can keep it straight up to 45km/h with full fuel tank. That and the fact it recovers much quicker than either the 109 and the 190 encourage players to play "air flak" by climbing vertically after way higher oppoments and shooting them accurately.

 

And frankly one of their problem is that they can't talk about things they are not comfortable with. They may fix something but admitting mistake has always been a problem.

There's never much talking about FM issues from devs side in most games I've been so far. It's had work and always painfull to go back and remake it, not even to mention to admint there's a mistake. I'm a little disappointed about FM development so far and hope they can improve on that. 

[Dakpilot]

One point always made is the 'unrealistic energy retention' and tests done against other aircraft with full flaps. Doing any energy/drag comparisons with other A/C at full flaps is pointless 

 

If you sit in the cockpit and look out to the left wing (you will have to slide a bit left to see it) there is the Flap indicator 'barber  pole,' at speeds below + -200kmh it will be fully out with all rings visible, as you increase/decrease speed you can watch it actively changing and almost completely retracting with the flaps at high speed.

 

In fact at most combat/dogfighting speed it is usually more than half in and changing all the time with airspeed, this is a factor when people complain about unrealistic drag with  'full' flaps in combat

 

Now whether this was used in this way in combat by Russian pilots is up for debate, and the strength/weakness of the pneumatic pressure flap system has not been properly explained one way or another

 

Try it  regardless it is a nice little detail

 

Cheers Dakpilot

[Bearcat]

The team is clearly tired of conjecture, opinions and anecdotal evidence being used to criticize their work. I don't blame them for wanting to only handle these issues in a more formal way. Our programmers try to deal in facts. All they want is for you to show them empirical and video evidence of what is wrong backed up with your "official" sources that something is wrong. Han has already explained that they used Soviet tests for the majority of our flight data for BOS. Some of you want to kick out that data as biased because it was tested in USSR. Well, they can argue the same about German, Japanese and U.S. test data. Where users have provided clear information we got something wrong they changed it time and resources allowing.

 

We've also explained that acquiring this test data was very difficult and we consider it a trade secret due to the rarity of acquiring such data so we do not release it publicly. But through the power of deduction you can find out what the data purportedly says by testing our aircraft in game as our goal has always been to get within a few percentage points of our source data. And there may be issues where the test data doesn't explain what should happen at a certain speed or in a certain situation. This is a grey area where there is no right answer and sometimes there is going to be a divergence of opinion.

 

And there are real life pilots on this forum that say we got some things wrong and we have many pilots who have told us we have gotten things right so that is a loggerhead and goes nowhere really.

 

There will never be a truly 100% accurate flight model in a flight sim due to a million factors. The only way is to go back in time and enlist.

 

I'm sympathetic to both sides of the coin, but the team responds best to carefully researched and prepared arguments.

 

Jason

 

 

I have pruned and reopened this thread. Please keep it on the topic at hand and please follow rule 18 if you want to actually see a change. Loose the personal commentary and the references to "bias" or direct insults to the hard work of this team. State your case and back it up. This thread will eventually be reclosed as there is already a substantial amount of information in it stating what the problems are. It just needs to be reported to the team in the manner prescribed below.

 

18.

Claiming that FM is incorrect without the required proof and starting a flame thread based on such claim is prohibited.

The form for an FM claim consists of:

• short but consistent description of the claim;
• link to a reference and to a specific part of such reference that describes correct behaviour of a disputed element/situation;
• game track record and the list of conditions used to recreate disputed element/situation.

Exception to this rule: FM discussion

 

 

Edited August 19, 2015 by Bearcat

[Bearcat]

This post was the title post of another thread that was started when this one was temporarily locked.

 

That thread has been pruned and reopened.

 

Since the original post was locked a new one to put up some additional data from the RAF test. Posted without comment.

 

 

 

[Maxyman]

Thanks for sharing Bert_Foster. That is aligned with how Yak pilots described flaps in their memoirs.

[III/JG2Gustav05]

A couple of charts from RAF test document AVIA 6/2422 in the UK archives. These are on a study on the affects of flap on Spitfire Turn performance. Various flap angles were tested. The stuff shown here is for a flap angle of 30degrees. Spit flap was a split flap similar to YAK 1. this might be relevant to the current debate.

 

The Fan plots shown are similar to modern Fan plots (Dog house plots in US parlance). The "Line of zero climb " is effectively Ps=0 or the sustained turn performance boundary.

 

 

What can be seen is flap 30 does provide an improved sustained turn rate (smaller turn time). 

Taking the intersection of Ps=0 line with the lift limit gives a turn time clean of around 19secs (18.84deg sec).

Looking at the same point with Flaps 30 gives a Turn time of around 17secs (21.2 deg sec).

 

What can also be seen is that Flap 30 results in a reduction in Sustained G of 0.2g. i.e. Max sustained G Clean is 3.0g whilst with Flap 30 is around 2.8G

 

 Fan plot showing Flaps at 60deg and 85deg

 

one more chart

 

just take a glance, look at "the turn maintaining height" curves on the upper right corner of the last picture. if my understanding is correct, it reveals that to maintain same turn radius flaps-up can maintain higher speed than flap-down, that means flaps-up turns faster than flaps-down in this condition.

[Bert_Foster]

"just take a glance, look at "the turn maintaining height" curves on the upper right corner of the last picture. if my understanding is correct, it reveals that to maintain same turn radius flaps-up can maintain higher speed than flap-down, that means flaps-up turns faster than flaps-down in this condition."

 

At the higher speeds yes. The only real area where you really get any advantage with Flap is in the slow speed regime close to the lift limit in the mid to lower altitudes. This is peculiar to low sweep (i.e. straight wings .... the situation is quite different with more modern swept wing types which have a much larger usable AOA range).

 

The essence of this whole argument regarding the YAK Flap as I see it is follows:

 

1. FACT at slow speed close to the lift limit you can/should expect to get a turn rate/radius advantage with small flap extension.

2. FACT as IAS increases flap extension will start to hurt your turn performance.

3. FACT you will always get a higher sustained G with flaps retracted rather than extended (talking WWII trailing edge flaps only)

3. This only occurs in the mid to lower altitudes, above that lack of power (i.e. Ps) results in any flap extension hurting you at any speed.

 

CONJECTURE

Does the YAK 1 IRL have a flap system that automatically blows back as IAS increases ....i.e has an air Load Flap load relief as part of its design ? .....  It seems to be modelled this way in the SIM.

i.e. If you have Full flap selected and accelerate air loads will blow it back in to around the 20degree position. Or if you bang the flap out at high speed they will only come out part way. You cant damage the flaps by Air loads in the sim

 

For what its worth I have a fair bit of time in the YAK52 and Nanchang CJ6 both have pneumatic single stage (Up/Down) flaps. Neither of them have any blow back or flap load relief system. Both have Flap limit speeds. Bashing flaps out above these speeds on these types will bend something.

Edited August 20, 2015 by Bert_Foster

[Saurer]

Are the flaps of the Yak 9 different to the ones on the Yak 1? 

 

Because if not we could try asking the guys at Hanger 10 about the flaps system, they have a Yak 9 in flying condition.