Well, that is interesting info. BTW, somehow the Yak-3 inferiority in turning doesn´t surprise me. One Finnish site (virtualpilots) has a translation of Yak-3 Pilot´s Notes. These Notes give the impression of quite bad accelerated stalling characteristics.

Yak-9´s inferiority in turns is a bit surprising for it has much lower wing loading and better power loading than the P-38. But, I don´t mind, I am a P-38 fan!

Jukka
Judging by shape of the wing, I expect Yaks to be very prone for aileron stall, this may be very dangerous during take offs, landings and dog-fights. There was a similar problem with Fw 190.
Please note that all the comparisons were with slightly outdated Western aircraft!

VVS fighter properties
 

Hi guys.

I am sorry Franek, but some of your statments are not true! I have looked into this a little bit and sought expert help.

A few points:

Your statement "For example Robert Bock in his Yak-7/9 monograph by Aj Press (p.30-31 in Polish edition) notes that when Yak-9P s/n 01-04 was tested (23.03-23.07.1947), it did include comparative trials with P-63C-1. It turned out that Kingcobra was better in horizontaldog-fight, getting on tail in 5 turns. Yak-9P had better performance only to 3000m but interestingly was a better diver, outclassing American fighter"

is not true. You should know that Bock is a self-appointed anti-Soviet historian, which should be evident from his writings. You cannot take such important claims as above to be true without looking into it if you suspect the author to be unfairly biased! I have asked Mr. Pilawskii about NII VVS reports about the comparative trials to which you refer and there are none! As a matter of fact prototype 01-04 was never used for comparative purposes, only for testing of various equipment and fuel cells arrangements. Besides, it had a wooden fuselage and was not, therefore, fully representative the Yak-9P.

According to Mr. Pilawskii there was another comparative test done (reference: TsAMO fond NII VVS opis 645266, list 385-390) using the first all-metal Yak-9P against P-63C-1 s/n 311626 and this is the test Bock is referring to. At normal weight (3220 kg) that Yak-9P was superior to the P-63 in all respects. However, when tested in overload condition (3588 kg) the Yak-9P was still superior up to 2000 meters, above which the P-63 was a better turner, getting on the tail of the Yak in about 5 turns. But the important point is that the Yak-9P was overloaded, in normal condition the Yak would get on the P-63's tail in 3-4 turns, depending on altitude.

So the claim that the Yak-9P was outclassed by the P-63C stands unsubstantiated. At best, Bock's claim is a misrepresentation of facts.

Furthermore, your statement:

"Also, very interesting are comments from a Soviet report prepared after the incident over Nis. It was noted that P-38 was better in horizontal turns rather than Yak-9, the latter being superior in vertical manouvers."

is also dubious at best!

There are simply no such tests in existence! A P-38L s/n 44-2421 was
extensively tested at NII VVS and the LII and two reports on this testing can be found in TsAMO fond NII VVS opis 639331, list 90, and TsAMO fond 29 opis 1165, del 8232, list 5-6, according to Mr. Pilawskii. I suggest we find them and read them before we take the above quote to be true! Simply put, there is nothing in them to suggest that the P-38 in any way could compete with the Yak.

Also, the comment:

"Judging by shape of the wing, I expect Yaks to be very prone for aileron stall, this may be very dangerous during take offs, landings and dog-fights. There was a similar problem with Fw 190."

is, well, interesting. While it may be true that you expect Yaks to be prone to aileron stalls, the fact is that they were not! If there is one aspect of the Yaks that were tested and tested again is was the wing configuration! In fact, the Yaks had no aileron stall problem and were superior to their western counterparts (including Luftwaffe fighetrs in this respect.

Finally, your coment:

"The question is were Soviet aircraft designed to fit into their doctrine or was their doctrine created on what they were able to build?"

suggests to me that you are biased against Soviet fighters! There can in my view be no doubt that the Russians were able to build some of the best
fighters of WWII, that's what they "where able to build"!

I find a disucssion such as this interesting, but I do suggest that we don't try to perpetuate old truths, that is old myths or western propaganda "truths". Test results are available for most fighter types and we should look closely at them but also at how the fighter performed against each other and during their service and under what conditions.

I try my best not to be biased one way or the other. I'll freely admit that I am an admirer of German fighters, but I do realize that they were outclasssed by allied fighters (Soviet and Western) in many respects, while bettering them in others, depending on time frame and conditions.

To be clear, what we want here is the truth, right? Not to "win" a discussion!?

Best regards,

Kjetil Aakra

Kjetil

I assume you have never read any of his writings. I may complain about his lack of engineering knowledge but not that he is biased.
I cannot say the same about Mr Pilawskii.

With all due respect, the fact Mr Pilawskii has not seen something does not automatically mean that it doeas not exist.

Re-reading the text it may be indeed it was not 01-04, nonetheless it must be stated here that:
- 01-04 was a testbed aircraft and was modified several times,
- the fuselage was of standard tubular steel frame and not wood,
- the diference was with aerodynamical fairing made either of metal or plywood,
- from engineering point of view such a difference does not affect performances,
- there were 29 Yak-9P with a plywood fuselage fairing.

Seeing no original report I cannot comment this but that according to Bock take off weight was 3550 kg and that some aircraft tested had reduced equipment and armament. If so, we cannot say about overweight but rather underweight.

Sorry, this was not a test performed in NIIVVS but a report filled after an actual combat between Yaks and Lightnings. On 7 November 1944 Lightnings of 82 FG clashed with Yaks of 866 IAP. Two Lightnings were downed for at least two Yaks, another being claimed downed by Soviet AA. IIRC there is still plenty of controversy as to who started the dog-fight. A report found at TsAMO was quoted by Mihail Bykov, who sometimes visits this board.

This conclusion comes from basic aerodynamic's knowledge. I have not found any description for Yak, but memories of Vladislav Valousek, Czech La-5FN pilot, indicate there was a problem with the latter type and both Yaks and Las had similar wing. I have not found anything that support claim of Soviet aircraft superiority in this regard.

I suggest you to check speed vs altitude or power vs altitude curves first and then to make any statements about performances of Soviet aircraft!

I am extremally interested what is Western propaganda truths? As yet I have found plenty of Soviet propaganda lies that are ad nauseam repeated by some not educated people in the West. Of course I see some 'German bias' but it is mostly due to lack of credible Soviet data.

If done by competent people, a comparison of technical items cannot be biased because of laws of physics that are the same in every country of the world. If you claim that something was outclassed you must just only support this with facts and our only problem is that we do not have Soviet facts.

Sort of on topic
 

Dear Franek,

I have stayed out of this discussion, but after reading through the thread, IMHO you have totally missed the point that Jukka made in throwing down the gauntlet. That point, if I interpreted it correctly, was for you, Franek, to participate in a thread with real data and sources, not just a lot of words and personal opinions. After reading several of your posts I see no identification of any primary documentation (Jane’s is most definitely not! And as an engineer, it was certainly not recommended to me “as the very valuable publication recommended for use by aviation engineers”. If I had used Jane’s as a reference in one of the reports I was paid to prepare for the USAF, I am certain my credibility would have been questioned.)
So, Franek, do you have appropriate technical data to support the opinions that you express so freely in putting down others opinions on this board? If you do, please identify it, no excuses like;” I have to digitise (sic) my collection of various data and graphs”.
Do you have the expertise to evaluate what data you might have? Are you an engineer, a physicist, or a pilot? I would not question these things, except that you almost without fail, devaluate others contributions as if you are the expert on every subject.


Best regards

Artie Bob

Just when I was starting to enjoy the thread, something turned a little more nasty from the lower third onwards.

Lets all try and stick to the subject at hand.

These discussions actually need some rules.

1. state your sources
- primary material rules
- secondary sources (specialist work, stating sources)
- general sources (including Jane's)
- annecdotal information

2. proof your point based on 1

3. keep it objective

4. no personal attack

Points one, two and three will determine the value of this debate, point four will determine if the debate will be allowed to continue. I'm not innocent of personal attack, which makes it a lesson for all of us.

Artie
I have some aeronautical engineering background but never worked as such. I may assure you that Jane's was recommended in my school as a review of trends during a preparation of a preliminary design of an aircraft.
Concerning the thread, as yet I have received no comments concerning my proposal of aircraft to compare. Also, as yet my only personal opinion was in regard of aileron stall in Soviet aircraft but it is really a knowledge of the first half-year of aerodynamics. Mentioned memoirs of Valousek, a pilot of Czech Squadrons in RAF and a pilot of Czechoslovak regiment contain a description of landing procedure in La-5FN. It was forbidden in the aircraft to add power during landing as it usually led to flipping over and to crash. In case of wrong approach or bounce it was suggested to crash the aircraft in a hard landing! Valousek once attempted to save his aircraft after a hard bounce and managed to add some power in order to make another approach (a standard in a Spitfire as he noted) but he considered it tricky and he was generally criticised for taking he risk (Valousek clearly noted that ailerons did not work).
Memoirs were published in late 1980s by a Letectvi + Kosmonautika magazine. This was described on page 10.
Comment concerning aileron stall characteristics of Fw 190 is backed up (IIRC) by AFDU report #55 as well as several combat reports of Allied airmen mentioning sudden flipping over of Focke Wulfs during dog-fights.
Regarding graphs, they do not really make much sense if not compared one with another, hence the need of making a graph combining them. I cannot do a one, however, if there is no consensus as to aircraft to compare.

Calm down, Artie and Ruy! I began the thread in the hope of encouraging Franek (or anyone else) to post data based on primary sources. Kjetil mentioned some docs, but how many of us has regular access to TsAMO? I.e. Kjetil should have posted (and translated) the docs he referred to.

Franek is right about the aileron stuff. If one reads the Yak-3 (see virtualpilots´s site) Pilot´s Notes, it is clear that it has poor stalling characteristics.

It seems that Pilawskii isn´t the most reliable of sources. I checked both Gordon&Khazanov´s and Gunston´s Encyclopedia of Russian Aircraft and both have the same gross weight info and that figure is what Pilawskii calls overweight. I have a hunch that Pilawskii´s "normal" figure requires severe reduction in fuel capacity, in aircraft already possessing not too great fuel capacity. Highly dubious to me.

Hello!

I insert below a text file I had on my computer hard disk. I wrote it as reply for Russian Battlefield Forum three years ago. Maybe it is of use for someone. Comments, corrections etc. welcomed.

Of note is the marked difference in performance of series-built examples and test examples in Soviet aeroplane production (at least GPW period). I think I have seen the chart from the "As" article on Internet as a picture, but was not able to find it now - I tried to. I have not bookmarked the Russian site where I saw it (or similar one).


One question and also the reason of my message. How does one stall an aileron (only)? I know I barely passed my aerodynamics exam (it was only my minor) but still I should know. Do you mean the situation when during turn a tight pull makes flow separate from lower wing tip and the plane flips (rolls) to other direction? Adverse yaw plays a big role here, keeping the ball centered with rudder pedals helps (as in all flying). Frise type ailerons can help too (with the price of added drag).

Why is this aileron stall so important (performancewise) ? NACA 23xxx series profiles are low-drag - good performace - but they have "ugly" and sharp stall characteristics. If I design wing which has smoother and predictable stall but has, say, 5% more drag is that a good design?

BTW What profile did the Yaks and Lavochkins have? I could now only find data for Yak-1 (Clark UP, thickness 14% at root and 10% at tip). Soviets seem to use a lot of the near flat-bottomed Clark profiles - ease of manufacture played into that?

One comment more and then I will stop. I have read everything I have been able to put my hands on about airwarfare over an around Finland. I do not remember a single Finnish book where performance of Soviet planes would have said to be poor. Nor has their performace been underrated hereabout. Vice versa, actually. Poor performance put on by the Soviet Hurricane pilots might be sort of exeption. In that sense Pilawskii's book didn't change anything. The preaching tone of his book went on the irritating side at times because of that. Perhaps we Finns aren't "Westerners" in that sense?

Regards,
Kari



The file:

"Yak-3 vs. La-7

In a older Soviet-era aviation magazine ”As”, issue 2/1991 pages 23-35 there is a article about evolution of aircrafts during the WW2. It concentrates on Soviet types and includes several performance curves (max speed vs. altitude). Similar curves were used also during the war (at least by FinnAF) for comparison purposes and to find at which altitudes own aircraft types do have edge (or if they have) and also where enemy types are weakest. Majority of the mentioned sources in the article are primary documents: type manuals and test flight data (by NII VVS and LII).

The article does have the performance diagrams Yak-3 vs. La-7.For both types is shown curves for series production examples and ”etalonnij” (model example)/ ”opytnij”(test example) ones. It is noteworthy that for series La-7 the speed drops around as much as 25-40 km/h and for Yak-3 some 5-15 km/h from the test examples. This might have something to do with La-7 being wooden construction and Yak-3 all-metal (or near). It is possible that the La-7 model examples had been finished with some extra work which was not done at factory line.

But the comparison. I am not able to put a picture here, but the summary is that La-7 beats Yak-3 in all altitudes, period. La-7 does have two performance peaks: at 3 km and 6 km altitude (as does La-5&La-5FN). Two peaks suggest a two-stage compressor (didn’t care to check and don’t remember offhand). Yak-3 does have clear peak at about 4,2 km altitude and smaller one around 2,2 km.

The speed marginal at 4,2 km altitude is only about 10 km/h for La-7 advantage. At 3 & 6 km altitudes La-7 is 45+ km/h faster than Yak-3. This for the factory examples.

For the production examples La-7 is better between 2-3,5 km altitude by some 25 km/h. At 4 km altitude Yak-3 is slightly better (~5 km/h). Above 5,5 km altitude La-7 is clearly better.

Actually the altitude/perfomance difference of Yak and La-series (EXCLUDING LaGG-3) fighters was seen also their use. I do have a (semi-secret) book which describes numerous missions by VVS Naval air forces (KBF, TsF, SF etc) during the GPW. Title of the book escapes me now. The book does have diagrams about the formations used. Lavochins were used for top cover formations (both forward and rear defence) and Yaks for close escort. This was also the FinnAF experience of VVS. In Eastern Front conditions Lavochkins were high altitude fighters and Yaks medium altitude fighters.

La-5/7 did have very limited endurance, some 45-60 minutes. BF109G did have the same but a single 300 liter drop tank doubled the time. BTW short time on station seems to have been a major drawback for 13 VA / II GvAK during the Vyborg operation later phases (=Kotka operation). I don’t think VVS front units usually used (wing) drop tanks with La-5/7. Correct me if I am wrong. Couldn’t find endurance time for Yak-3 but it seems to have had 400 litres internal fuel (same as BF109G) and couldn’t have been much better than La-5/7.

La-7 had roughly twice the punch (or more) in weapons that Yak-3 and air cooled engine less prone to be stopped by combat damage. All in all it seems Lavochkins were the real winners.

The As-magazine article does have performance curves for FW190 A-4 (Soviet and British flight test data) and A-5 (German manual). Comparison between them and Yak-3 and La-7 is bit of apples and oranges. FW-190 A-6/8 (or the JaBO F subtypes) were in use when the later Soviet planes were taken in use. Then there is FW190A-9 and D-9 plus the fact that there was myriad of equipment variations for the FW-190. Fair comparison is difficult and there is no single general and correct answer. Remembering this it is interesting to note that below, say 1,5 k m FW190A-5 was equal to series Yak-3 and La-7 and above 5 km better than series production Yak-3 and equal to La-7. Between 1,5 – 5 km La-7 is the clear winner.

If someone is really interested about Soviet a/c performance the mentioned As-magazine article belongs to the essentials.


Hope this helps some (my fingers are tired)

Kari "

Addition to my message above.

I (re)found this site:
"The Incomplete Guide to Airfoil Usage" by David Lednicer
http://www.aae.uiuc.edu/m-selig/ads/aircraft.html

According this all Yaks had Clark YH (14%root, 10% tip) profile. My recollection is that later Yaks used other profile or at least wing thickness was changed (stronger metal wing spars allowed reduction of spar height?). I may remember wrong, though. I wrote above that Yak-1 had "Clark UP" profile. I took this from Modelist-Konstruktor 1/1975 (also on net, see: http://mkmagazin.almanacwhf.ru/avia/yak_1.htm ) and there the profile is indeed given as "Y"Pi"-2" (where "Pi" is cyrillic "P"). Anyone knows for sure what Yak wing profiles were?

The above profile site has all Lavochkins (= -3, -5 -7) with NACA 23016 at root and NACA 23010 at tip. Thick root and very tapered wing plus NACA 23xxx stall characteristics -> vicious stall (my expectation at least). No matter how clever aileron design. And no wonder that Lavochkin wings got slats.


Cheers,
Kari