Yakcopter or Automatic flaps? + Video

[Trinkof]

You think? Well, very specifically, the top speed of the Yak-1 S69 was 535km/h at 6000m. In game it's flying 580km/h. This has been brought up like a year ago. Not remedied.

It fly 580 in cold winter.... In game summer conditions, it is around 530, so it is OK

[Reflected]

It fly 580 in cold winter.... In game summer conditions, it is around 530, so it is OK

 

depends on the time of year the real test was performed. It's not really fair or scientific to only consider the most optimistic possibility.

[JtD]

It fly 580 in cold winter.... In game summer conditions, it is around 530, so it is OK

I fly 580 in standard conditions and compare them to 535 achieved under the same conditions, so it's not OK.

[Matt]

Here are my results. Tested on the autumn map (=15°C on ground).

Oil cooler and radiator shutters closed as much as possible to stay at maximum 100°C for the coolant and oil.

Reference are on the bottom. I included the TSAGI (afaik) graph, just for comparison sake (just to have a curve, the tests might've been done very differently, even though the speed fits the BoS Yak pretty well up to crtical altitude.

 

I used two different methods to calculate TAS from IAS. Method 2 is the classic, Method 1 is 1% per 600 ft (i can't remember where i found it, but it's supposed to be more accurate and it gives closer results in most cases). Regardless of method, the curve of the BoS Yak is pretty unusual at more than 4000 meters, which is the thing that mattered and the calculation is never 100% exact.

 

Method 1 (+1% IAS  per 600 ft) 

Altitude TAS

8000m 520 km/h

7000m 543 km/h

6000m 560 km/h

5000m 576 km/h

3650m 570 km/h

2400m 553 km/h

1800m 553 km/h

300m 521 km/h

 

Method 2 (+2% IAS  per 1000 ft) 

Altitude TAS

8000m 552 km/h

7000m 574 km/h

6000m 588 km/h

5000m 600 km/h

3650m 589km/h

2400m 566km/h

1800m 562km/h

300m 523 km/h

 

[Reflected]

Thanks for the chart and testing, Matt. Looks like our Yak is quite realistic at mid altitudes, but 10-15 kph too fast at ground level ,and way too fast above 4000m? If your first method is accurate, that is. If the second is, well, it really is a rocket ship.

Edited December 2, 2015 by Reflected

[Matt]

I would disregard method 2, but i included it, because many TAS calculators you can find online use that method. If you would use method 2 for the other planes in BoS, you would also get too high performances for those planes.

 

Also the speeds themselves don't really matter that much, what does matter to me, is that the speed over critical altitude (3650-4000 meters, depending on source) is still getting higher. So there seems to be something wrong with it.

Edited December 2, 2015 by Matt

[303_Kwiatek]

It was obvious much earlier that Yak-1 ( Lagg3 too)  and 109 F-4 are huge overperformer at high alts ( e.x. http://forum.il2sturmovik.com/topic/15231-isa-speed-testing-all-fighters-game). Summer maps ( and ISA conditons settings) just confirmed previously test and findings. But devs still dont worry about it too much.

 

Now im waiting for Fw 190 A-3 climb rate test  ( ISA or summer conditions) which  will confirm BOS A-3 underperforming in climb rate ( winter climb rate test proved that A-3 climb rate is underated)

Edited December 2, 2015 by 303_Kwiatek

[Reflected]

I see your point, it's not the position of the curve, but the shape at altitudes that indicates there is something wrong.

[L3Pl4K]

Matt if your historical data and test is correct, this should be fixed.

[Kaxii]

Thank you for the graph Matt!

 

I've been watching this issue for a while now but not taking part, but I think now I have seen both sides I can partake.

 

In my opinion, there is something wrong with the Yak's flaps. I'm not qualified to say what exactly it is, but the huge difference in behaviour between its flaps and other aircrafts does make it seem suspect.

 

But. It should be fixed because its not realistic, as far as I'm concerned I have more of a trouble with the Yak flap issue as a Yak pilot than when I face Yaks when flying as Germany. The flaps don't actually help that much in combat in my experience, they still bleed too much speed, and you don't need them to out turn a 109, they only make it easier if a 109 (foolishly) commits to a horizontal sustained turn fight down to low speeds, but most of the time I just find that when I do get a chance to use them they don't help that much and most good 109 pilots notice as soon as I drop flaps and simply level out and run, knowing I can't keep up due to the massive drop in speed by deploying those flaps. I want them fixed, so I know that when I fly the Yak, its flying realistically, I want it to feel real, but "balance" wise, flaps aren't an issue and should't make much of a difference in a dogfight (I've only been shot down once by a Yak with flaps out so far).

 

But this issue with over-speeding is a larger issue, and I think we should concentrate on this more, as it does affect dogfights a lot more (because a 109 should be able to out run a Yak at high altitude) and a 109 should be able to use speed to overcome the Yaks superior horizontal maneuverability, but ATM it often can't due to this over performance in speed, especially in the G2's case (who cant easily out run and can't out turn a Yak due to under+over performance of the respective aircraft).

 

So thank you for all this research, hopefully we can get enough to put forward to the devs so we can have first of all a realistic and and enjoyable Yak (and other aircraft) to fly.

[JtD]

Thanks for your test, Matt. A very good illustration of the issue.

 

One question - why did you decide for 100°C maximum temperatures for water and oil? 100 is the recommended range, but 110 is the permissible maximum.

 

Fwiw, method 1 is more accurate down low, method 2 up high. At 6000m, it's about exactly the middle of the two.

[Matt]

At 3650 meters, I got the "engine overheated" message above 100°C. Might be an issue by itself, but at higher altitudes, the radiators were at 20-25%, so the speed loss is minimal.

[6./ZG26_5tuka]

I wouldn't really give much on the technochat. It shows water overheating when reaching 90°C in the La-5 which is definetly not supposed to damage the engine.

[Brano]

No water in La-5 engine

[6./ZG26_5tuka]

Might be oil than. Can't blame my cyrillic reading because it is not existent.

Edited December 3, 2015 by Stab/JG26_5tuka

[Matt]

Then the engine itself is overheating (gauge on the right).

 

In all my tests, an overheating message caused the engine to become damaged sooner or later, so I will not make tests with that message popping up.

 

And in any case, the speed difference between running with 5-10% more closed radiator to get 110°C is offset by the inaccuracy of the IAS to TAS calculation and my test was only meant to show, that the speed above critical altitude is off. For everything else, the test is too inaccurate and the exact test procedures of the sources are not known to me anyway, so I can't compare that.

[Brano]

Might be oil than. Can't blame my cyrillic reading because it is not existent.

It is only oil as it is air cooled engine in La-5.Knowledge of azbuka is not required to know that 

+ temperature of cylinder head,which is another standard gauge with air cooled engines.

+ if someone has urge to discuss till the bitter end about anything that comes from former USSR,knowledge of russian/reading azbuka is kind of essential.

[II./JG77_Manu*]

Then the engine itself is overheating (gauge on the right).

 

In all my tests, an overheating message caused the engine to become damaged sooner or later, so I will not make tests with that message popping up.

 

And in any case, the speed difference between running with 5-10% more closed radiator to get 110°C is offset by the inaccuracy of the IAS to TAS calculation and my test was only meant to show, that the speed above critical altitude is off. For everything else, the test is too inaccurate and the exact test procedures of the sources are not known to me anyway, so I can't compare that.

 

the most exact procedure is like i did it already with all the BoS fighters at different altitudes-->taking the grids as reference, flying 40km

[Matt]

 Yes that would be much more accurate (i also used it for some tests), but it's a little bit more tedious to check for the devs i believe and for this special case, i think the IAS/TAS calculation is still good enough.

[CaK_Rumcajs]

 Yes that would be much more accurate (i also used it for some tests), but it's a little bit more tedious to check for the devs i believe and for this special case, i think the IAS/TAS calculation is still good enough.

I'm afraid the simplification that comes with the IAS/TAS conversion is too significant for the numbers to be taken seriously. The error increases with altitude and because altitude performace was in question I can only suggest you to measure on map grid.

[bivalov]

One question - why did you decide for 100°C maximum temperatures for water and oil? 100 is the recommended range, but 110 is the permissible maximum.

 

some sources says  that 110 degrees for oil/water is unlimited maximum, yes, and 115 degrees for oil/water have 5 min. limit. but many sources (manuals) also says that 110 degrees for water have 10 min. limit.

 

and 100+ degrees for oil also could have 10 min. limit, but personally i know only one mention from book of Stepanets (third paragraph) - "Для мотора же ВК-105ПФ максимально допустимые температуры имеют, как известно, следующие значения: воды 110°С, масла 115°С в течение 5 минут и 110°С в течение 10 минут" - i.e. 110 degrees for water without concrete limits, and 110 degrees for oil with 10 min. limit.

Edited December 9, 2015 by bivalov

[Reflected]

Today I was caught by 2 Yaks in a near vertical climb. They prophung with their flaps down, and eventually clobbered me. I could see them wobble left and right, but their nose just wouldn't drop.

 

Still ,I believe it's not only a Yak thing. I think in game the propwash flowing around the flaps creates enough airflow and lift to prevent or delay stalls. It must be a little overdone. I think 109s would have the same advantage if it was a matter of pushing a button to release flaps.

[JtD]

Yes, often these higher limits come with a time limit, but we're looking at maximum speeds and not indefinitely sustainable speeds here. 10 minutes or so is plenty of time for acceleration to determine "top" speeds. We have 3 minutes or 5 minutes of acceleration in other air forces.

[II./JG77_Manu*]

Still ,I believe it's not only a Yak thing. I think in game the propwash flowing around the flaps creates enough airflow and lift to prevent or delay stalls. It must be a little overdone. I think 109s would have the same advantage if it was a matter of pushing a button to release flaps.

 

No, i tried with every other plane - with different extending angles for the one's having manual adjustment -, that's working with no other plane, like it does with the Yak. For a few it makes stall fights even worse (P40 and 190 for example)

[Holtzauge]

Today I was caught by 2 Yaks in a near vertical climb. They prophung with their flaps down, and eventually clobbered me. I could see them wobble left and right, but their nose just wouldn't drop.

 

Still ,I believe it's not only a Yak thing. I think in game the propwash flowing around the flaps creates enough airflow and lift to prevent or delay stalls. It must be a little overdone. I think 109s would have the same advantage if it was a matter of pushing a button to release flaps.

 

Well if the slow speed prop efficiency is optimistic in BoS it would not be the first time in a sim: The early Maddox IL-2 was also plagued with this and you could fly much slower than speed for best climb and still get the same climb rate: Basically the rate of climb flattened out at best climb speed and you could slow down way slower and still get the same climb rate. This was tuned out eventually though.

 

In fact also DCS has had this problem recently and before this was tuned the P-51 there climbed much better than it should at a speeds lower than IAS for best climb speed. Seems a lot of sims initially fail to take the reduced prop efficiency that comes with a high blade loading and prop operating at a poor L/D into account.

 

So maybe the problem is not the flap modelling but the prop efficiency? For sure a too optimistic Yak-1 prop model at slow speeds would also show up as too good turn rates at slow speeds with flaps out and also a prop hanging ability.

 

A good indicator if slow speed prop efficiency was too optimistic would be if you could climb the BoS Yak-1 at IAS speeds lower than optimal and still get basically the same climb times. Anyone tried this?

Edited December 5, 2015 by Holtzauge

[Fern]

P-40 Flaps were split flaps also, like the Yak's. Watch 6:00 - 7:14.

 

 

"The flaps should never be lowered when your airspeed is above 140 mph (225 kmh). At higher speeds you might damage them by trying to put them down. The plane also becomes too nose heavy........The flaps go up pretty fast, once started up they continue to move closed. So dont try to raise them at slow airspeeds, when your altitude is below 500 feet. At airspeeds less than 110 mph, the plane will mush down if you raise the flaps. So if you overshoot field, gun the engine and climb back up to 500 feet before you put the flaps up."

 

 

Devs just need to render the flaps useless if deployed over certain airspeeds and be done with this shit. Even Mark Jefferies (a yak pilot) said not to exceed certain airspeeds with flaps down. Yak-1 isnt the only plane that can do magical things with flaps down either.

[Brano]

P-40 has hydraulic operated flaps.They will get physical damage if pressure applied is over critical value.Smtg will just break down mechanically.

[Matt]

A good indicator if slow speed prop efficiency was too optimistic would be if you could climb the BoS Yak-1 at IAS speeds lower than optimal and still get basically the same climb times. Anyone tried this?

 

I tested at 230, 260 and 300 km/h IAS and got the worst climbrate with 230 km/h and the best with 260 km/h. Pretty much how it should be imho.

[Holtzauge]

I tested at 230, 260 and 300 km/h IAS and got the worst climbrate with 230 km/h and the best with 260 km/h. Pretty much how it should be imho.

Screenshot.png

Yep, that chart looks like you would expect so looks like prop efficiency is not the issue then. Thanks for doing the test.

 

I have been flying the Fw-190 most of the time since I got BoS so up til now I only read about the Yak-1 flap issue but after flying it a bit now I have to agree it does seem fishy: Was going round and round against a G2 and not making much progress but then I decided to pop the flaps and lo and behold I got into a firing position real quick. I can't quantify it of course but really, if it was this easy IRL then Fw's and Me's would have been Yak fodder for sure and surely we would have loads of Soviet pilots account of how the Me could be handily out turned as soon as the flaps were dropped.

 

OTOH flaps seem to help the Me and Fw too: If I need to gain those extra degrees of deflection in the Fw, dropping the flaps works there as well so it seems to be an issue with all BoS aircraft. I also agree about the Yak prop hanging: Real easy to nail a Me going over the top in a zoom since the Yak responds very well to control input on all axes even at extremely low speeds.

[6./ZG26_5tuka]

Flaps are meant to help turning. The Fw 190 had a Kampflappen (combat flaps) seetting for a reason. As for the 109 it's roughtly 5-10° of flaps. However the effects when deploying landing flaps seem way more flight effecting on the 109 and 190 than the Yak.

 

Also, turning tighter does not ultimately mean turning better.

 

Prop effeciency does not include prop wash I assume, which is another thing worth looking at I think.

[Fern]

Yep, that chart loo I also agree about the Yak prop hanging: Real easy to nail a Me going over the top in a zoom since the Yak responds very well to control input on all axes even at extremely low speeds.

 

The prop hang on the Yak is ridiculous. Saw someone doing it today and they were just sitting there hovering. Made for an easier target though. I thought the Yak-1 engine was suppose to be a POS. Also being heavier than a 109, how the hell does it float like that?

 

It's broken.

[JtD]

...I thought the Yak-1 engine was suppose to be a POS...

It wasn't.

 

...Also being heavier than a 109...

It's not.

[YSoMadTovarisch]

It wasn't.

 

It was even by 1940 standard. Did you know that the Soviet only got that engine power by overboosting the hell out of the engine and thus their engine life span was pathetic, usually 1/4 than that of other nation, if the M105PF and the M82 were made by say, Allisons, they would have rated them at 2/3 of the power boost used by the Soviets.

[JtD]

I disagree, if the engine had been Allison manufacture, it would have been rated at the same power, with maybe some use restrictions, but would have been 10 times as expensive because of the efforts put into increasing engine life span. No one put 800hp engines into 3t fighters in 1940. The fact the Soviets preferred low production cost over a long service life doesn't turn an engine into a pos.

 

I would like to know/see the source for the 1/4 figure you were posting, if you have it.

 

Fact is the basis for the engine, the Hispano Suiza 12Y, was a state of the art engine of the mid 1930'ies, absolutely comparable to and competitive with DB600, RR Merlin or Allison V1710. Post war, the Swiss in their peace time air force got 1300hp at 1050mm boost out of their development, just as much as the Soviets did 3 years earlier under wartime pressure.

[Holtzauge]

Flaps are meant to help turning. The Fw 190 had a Kampflappen (combat flaps) seetting for a reason. As for the 109 it's roughtly 5-10° of flaps. However the effects when deploying landing flaps seem way more flight effecting on the 109 and 190 than the Yak.

 

Also, turning tighter does not ultimately mean turning better.

 

Prop effeciency does not include prop wash I assume, which is another thing worth looking at I think.

 

Yes, AFAIK there was an intermediate flap setting on the Fw-190 and sure, this would be good to get a smaller turn radius and slightly better turnrate also IRL albeit at a lower speed. However, in BoS I have found that deploying the full flap deflection also for the Fw-190 helps you in a turnfight  so that's why I think it seems to be an general issue.

 

If you by propwash effect mean that you get a lower stall speed with power on than power off then yes I agree that this could be an issue in BoS. In my C++ simulation of the Yak-1 I get stall speed power off at 134 km/h and power on 124 km/h but in BoS I managed to keep controlability and hang on the prop down to around 100 Km/h which seems strange. Can't say I kept altitude in that test but it still seems strange to be able to retain control in roll, pitch and yaw at such a low speed......

[Dakpilot]

Anyone who thinks the Klimov engine is a PoS should do a little research into Hispano-Suiza aero engines and Cars to see the quality of their products and designs

 

Although what was produced in the early days from hastily built factories transferred far beyond the war zones by poorly/quickly trained workers had many quality issues, 

 

But Russian aircraft design in the 30's and 40's was hardly primitive as perceived by many, in some instances they were limited by not having access to the latest metallurgy and latest tech, but the designers were certainly not backwards

 

In a wartime critical situation how important is having a very long engine lifespan? surely less than being able to mass produce in huge numbers a competitive powerful yet (comparatively) reliable engine that can be swapped by basically trained aircraft fitters

 

Cheers Dakpilot

[Holtzauge]

I ran a simulation to compare Yak-1 with and without flap at 1 Km altitude. Results attached.

 

Some observations:

 

The best turn rate without flaps is 19.6 deg/s, R=227 m  at 262 Km/h TAS.

 

The best turn rate with 60 deg flaps is 18.7 deg/s, R=168 m at 203 Km/h TAS.

 

Now if I read off (in my text file not the attached figure) what speed I can maintain with 60 deg flap going at the same 227 m radius as without flap I get 261 Km/h so basically I can match the turn rate here. Not sure how to interpret this and if the simulation is correct but it may have to do with a reduction in induced drag compensating for the increased parasitic drag. I would have expected the flap deployed plane to loose ground more rapidly but anyway the important conclusion is that the flap deployed plane does not gain.

 

So what about turning a little tighter to gain some lead with flaps deployed? Reading off what speed and turn rate a radius of 219 m would give this essentially gives the same turn rate 19.5 deg/s and a speed of 253 Km/h TAS.

 

So the simulation indicates that both maintaining the same turn radius or turning a little tighter with flaps should not give an advantage since the speeds you can maintain will not allow you to close the gap and yet to me it seems that in BoS you are rewarded for popping flaps and you can rapidly gain firing position if you do.......

 

 

 

 

[JtD]

Don't forget that if you're turning at the flaps up stall limit, you can bleed speed once you pop out the flaps down to flaps down stall limit. This will help instantly and significantly, even if only for a short time.

 

Your simulation isn't that different from BoS. Check the last chart in the first post for comparison, if you like. http://forum.il2sturmovik.com/topic/18834-sustained-level-turning-flaps-down/

[Holtzauge]

Don't forget that if you're turning at the flaps up stall limit, you can bleed speed once you pop out the flaps down to flaps down stall limit. This will help instantly and significantly, even if only for a short time.

 

Your simulation isn't that different from BoS. Check the last chart in the first post for comparison, if you like. http://forum.il2sturmovik.com/topic/18834-sustained-level-turning-flaps-down/

 

Yes, for sure you can turn tighter and bleed some speed with flaps out but what I find strange is that I don't seem to slow down as much as the simulation suggests when I do. OTOH when looking at the last figure in the post you linked which seems to be from BoS measured data I agree that this tabs pretty well with yours and mine calculated figures. Still hard to reconcile the in-game experience with this since in my experience if you have trouble pulling enough lead you can pop the flaps and you not only get your lead angle but you actually close the distance as well which seems hard to reconcile with the figures I think.

 

Also, I'm still quite sceptical about the low speed handling of the Yak which facilitates the prop hanging feature: With 60 deg flaps and full power the Yak stalls at 124 Km/h in my simulation and yet in BoS I am able to hang at 100 Km/h IAS with control authority on all axes ........

[L3Pl4K]

Holtzauge do you fly online? It is a pleasure to see a yak hang on prop and flaps, and hit your plane in a climbspiral.