LaGG-3 Series 35

[LLv34_Flanker]

S!

 

 Values are in CINA and values were recorded with Mata Hari system, quoted like this:"The first modern flight recorder, called "Mata Hari", was created in 1942 by Finnish aviation engineer Veijo Hietala. This black high-tech mechanical box was able to record all important aviation details during test flights of World War II fighters that the Finnish army repaired or built in their main aviation factory in Tampere, Finland. The "Mata Hari" black box is displayed in the Vapriikki museum in Tampere, Finland."

 

Here a link how it looked like: http://www.vlmyrsky.fi/historia/19

Edited March 20, 2014 by LLv34_Flanker

[Crump]

Good Stuff Flanker.  Similar devices used to record atmospheric conditions were used by most developed countries at the time.  I have several of the raw data from German testing recorded on a similar device.

 

Based on the turn performance results over altitude, they did not use true airspeed in the calculations but rather IAS, CAS, or EAS which is not surprising. 

[LLv34_Flanker]

S!

 

 The "Mata Hari" could record up to 8 different values, including control forces etc. So it was a rather sophisticated piece of equipment for it's time. It was used on both own and captured planes during test flights. Also Vaisala did supply various equipment used for testing. And Vaisala is still in business today.

Edited March 20, 2014 by LLv34_Flanker

[JG1_Pragr]

Any Soviet trials / nominal specs knows for series 35 LaGG-3..? (not to diss Finnish results, but it is very hard to find material on Soviet fighter aircraft)

 

The only Soviet data I've seen about Lagg-3 so far is the pilots manual from 1943. It's interesting to compare some data there with the data get by Flanker. According to the Soviet manual the maximum allowable speed in dive for Lagg-3 with M105P and PF engine was 600 km/h and 2 800 rpm. But I consider this number as the "absolutely" safe. In real situation the limit was probably exceeded according to the situation. 

[bivalov]

dive limit for planes with modernized control (if i not mistaken, it's exactly s29 and after), ~690 kph TAS... and i know reports'41, where written about similar speeds and even planned test at other speeds, mention'42 about behavior of aircraft in dive etc... so, i mean, garanteed ~690 kph TAS for modernized series, it's correctly and planes can show a bit more, apparently...

[Crump]

 

But I consider this number as the "absolutely" safe. In real situation the limit was probably exceeded according to the situation. 

 

 

Maybe it was exceeded but I would tend to disagree.  Here is why...

 

 

The limits may not be actually flight tested is very true as the result of the engineers being right is catastrophic for the poor pilot. 

 

However, the limits are set by very real parameters. 

 

Dynamic pressure limits were well known and not hard to calculate in the 1940's.  Dynamic pressure limits (called q-limits) usually manifest themselves in the form of flutter which can destroy an aircraft in the blink of an eye.

 

Where designers ran into trouble during the World War II era was in the transonic realm.  Several designs ran into compressibility issues (mach limits) long before their calculated Dynamic pressure limits were encountered resulting in fatalities.  They ran into these issues at a lower velocity than what the Dynamic pressure limits allowed.

 

That is because compressibility is a function of true airspeed resulting from the aircraft interaction with normal shock formation and not the aerodynamic forces used to determine the q-limits.  Subsequently at high density altitudes one could stay well within the q-limits and exceed the mach limits.

 

Because of the lack of transonic realm knowledge, a World War II design is more likely to run into trouble below the established dive limits rather than being able to exceed them.

 

Looking at the Lagg 3 Series 35, 600 kph comes out to about mach .76 which is one the lower side but still in normal range for a World War II fighter so I see were your opinion comes from.  Exceptions are rare but they do happen. 

 

Many designs in World War II started out with blanket limits such as the 750kph IAS dive limit of the Bf-109E.  This 750kph IAS was a calculated q-limit dive speed.  The Germans lost some aircraft in dives and upon actual flight testing found out the aircraft had directional stability issues.  One of the effects of normal shock formation is to move CG back changing the stability margin.  They restricted the initial blanket 750kph to lower the limit at higher altitudes to avoid this compressibility effect and made design changes to increase directional stability. 

 

The airplane ran into compressibility effects resulting in a lowering of the established q-limit dive speed.

 

We just need more data on the VVS designs, LOL. 

dive limit for planes with modernized control (if i not mistaken, it's exactly s29 and after), ~690 kph TAS... and i know reports'41, where written about similar speeds and even planned test at other speeds, mention'42 about behavior of aircraft in dive etc... so, i mean, garanteed ~690 kph TAS for modernized series, it's correctly and planes can show a bit more, apparently...

 

What are the changes for modernized controls?  Do you know as they can tell us if the World War II variant was just being safe and the limit could be exceeded?

Edited May 5, 2014 by Crump

[Venturi]

Good stuff

[bivalov]

What are the changes for modernized controls?  Do you know as they can tell us if the World War II variant was just being safe and the limit could be exceeded?

 

cant said absolutely correctly, not so much information and personally i was not really interested in question, but i know that in 1941 lagg was tested at (quote from report) - 

 

 

"1. На самолете Лагг-3 М-105П штопор до двух битков с недобранной ручкой и пикирование до скорости 700 км/час по прибору безопасны.

2. Главному конструктору т. ЛАВОЧКИНУ необходимо:

...

3. Считать необходимым ЛИИ ИКАЛ провести испытание самолета на пикирование до скорости 860 км/час по прибору, согласно заключении ЦАГИ, а также провести полное исследование штопора самолета..."

 

 

- 700 kph IAS (safely), and was planned test at 860 kph IAS (ie, i just mean that plane not fall apart exactly at 691 kph TAS)...

 

further, at least in 1941, were found several problems (with strength of glass of canopy, with flutter of tail and partly controls, if i remember correctly), so, manual'43 for laggs-3 gives 600 kph IAS if aircraft with balancers on rudder or just with modernized controls, apparently (these balancers were already on first serie, and 1 balancer later, but some early planes not equipped with them at all, and looks like that late series has just another rudder), and 550 IAS if without -

 

 

"Не допускать при пикировании скорости более 600 км/час по прибору и раскрутки винта свыше 2800 об/мин. На самолетах, не имеющих балансиров на руле направления, скорость пикирования не должна превышать 550 км/час во избежание появления флаттера."

 

 

plus mention of one of developes -

 

 

"Имеется отчёт о специальных испытаниях ЛаГГ-3 на флаттер - производились пикирования до 680 км/ч, признаков флаттера не было."

 

[Crump]

bivalov,

 

Good information and yes there are some good clues in there!!

 

 

- 700 kph IAS (safely), and was planned test at 860 kph IAS (ie, i just mean that plane not fall apart exactly at 691 kph TAS)...

 

You are correct, there is variation in everything.  The safety margins are just much smaller in aviation than any other field.  When the engineers set the limits, there just is not much to work with at all in terms of safety, especially in a high performance warfighting machine.

 

Ok, 700 kph is only 9 kph or 5 knots......

That is within instrument tolerances.  Maybe not the ones TSAGI used to measure speed but the normal airspeed indicator found on the production models is not as accurate. 

 

Let me make sure I have the facts right.  The service model Lagg 3 series 35 was limited too 600 kph but a test aircraft was dove to 700kph?  Correct?

 

 

Имеется отчёт о специальных испытаниях ЛаГГ-3 на флаттер - производились пикирования до 680 км/ч, признаков флаттера не было." = There is a report on the special tests LaGG-3 flutter - made ​​a dive to 680 km / h, there was no sign of a flutter. "

 

 

If that is true, the test aircraft would have been rigged for safety purposes for the high speed flight investigation with things they would not do to a service aircraft because it could not do its job.  It does not do much good if the pilot cannot come back and confirm he reached the service aircraft boundary safely.  The job of the test aircraft is to confirm the boundaries of the service aircraft.  For safety purposes, they would do things like limit control surface travel to avoid flutter and overstress conditions, restrict trim control, etc....these are things that can be done solely for the purpose of added safety when confirming the service aircraft limit.

 

It does not mean a service model which has to perform other missions can equal the performance of the test aircraft.  The engineers determine that based on the high speed flight investigation data and those recommendations are published in Pilots Operating Instructions.

 

That does not mean the test results are invalid and new limits cannot match the test aircraft performance.  You just have to look in the POH!!

 

 

 

further, at least in 1941, were found several problems (with strength of glass of canopy, with flutter of tail and partly controls, if i remember correctly), so, manual'43 for laggs-3 gives 600 kph IAS if aircraft with balancers on rudder or just with modernized controls, apparently (these balancers were already on first serie, and 1 balancer later, but some early planes not equipped with them at all, and looks like that late series has just another rudder), and 550 IAS if without -

 

Great info.  They definitely had a flutter problem.  The fix for flutter is the balancing of the controls which would have allowed an increase in the q-limits!!  That is a huge part of the equation.  It is the major reason they went from 550kph IAS to 600kph IAS. So there is our q-limit raise resulting from balancing the controls.

 

"and partly controls" is open to interpretation somewhat.  I am not familiar with the state of TSAGI's compressible aerodynamics research as I am with the United States, United Kingdom, and Germany's progress in aerodynamics.  As an educated guess it looks like they did run into compressibility issues.  As I said, one of the effects of compressibility is to lower the stability margin.  That means it creates control issues.

 

It is the onset of unsafe bad things that define the performance envelope.

Edited May 7, 2014 by Crump

[Crump]

One thing too that "muddies the water" with compressible aerodynamics.  There is a wide variety of results when expressing the effects. 

 

It is not my intention to lecture anyone so please don't be offended.  We have never met face to face.  I am know you are an intelligent person. 

 

 

To understand the charts information, one must understand what a coefficient of pressure means.  It is simply a non-dimensional ratio of dynamic pressure to whatever pressure we want.  For example, a co-efficient of Drag is the ratio of dynamic pressure to drag pressure; co-efficient of lift is the ratio of dynamic pressure to lifting pressure, etc....

 

http://en.wikipedia.org/wiki/Pressure_coefficient

 

Here is a good visual of the wide range of compressible aerodynamics theory and the effect upon results found during World War II:

 

 

 

In otherwords, TSAGI mach .76 may very well be just as fast in the air as the RAE's Mach .9 as measured on the instruments of the day and compressible flow theory used!!

 

I am sure the developers are very much aware of this fact.

 

What does that mean for us as player? 

 

It opens options to the developers!!!!  That is a good thing for us as players.

 

 

 

 

[LLv34_Flanker]

S!

 

 Would be great to see what data devs use, just for comparison. In game you can safely dive well over 800km/h IAS before parts stat flying off and even before that there is no shaking or whatever. And yes, FM is not done yet I know.

[bivalov]

Let me make sure I have the facts right.  The service model Lagg 3 series 35 was limited too 600 kph but a test aircraft was dove to 700kph?  Correct?

 

as written in pilot manual'43, and said developer who got original report, yes, 600 IAS ... 

 

meanwhile 700 IAS, really, is speed during tests of first serial planes (before war, if i not mistaken)... 

 

Great info. They definitely had a flutter problem. The fix for flutter is the balancing of the controls which would have allowed an increase in the q-limits!! That is a huge part of the equation. It is the major reason they went from 550kph IAS to 600kph IAS. So there is our q-limit raise resulting from balancing the controls.

if i understood you correctly, you are absolutely correct...

 

in total, personally my opinion about modernisation - all early lagg-3 are without balancers > after tests (at 600 > 700 > ??? IAS), lagg-3 got 2 balancers on rudder (~1-4 series and, maybe, later), or only 1 upper balancer a bit later (~7 series) > somewhere in early'42 rudder was modernized (i checked several drawings and some info, yep, starting from lagg-3 ~23 series instead upper balancer, a bit another rudder with "aerodynamical compensation")...

 

"and partly controls" is open to interpretation somewhat.

 

I am not familiar with the state of TSAGI's compressible aerodynamics research as I am with the United States, United Kingdom, and Germany's progress in aerodynamics. As an educated guess it looks like they did run into compressibility issues. As I said, one of the effects of compressibility is to lower the stability margin. That means it creates control issues.

 

It is the onset of unsafe bad things that define the performance envelope.

this is just because i wrote from my memory, and was not sure... but there really were re-balancing of elevators (no effect) and re-balancing of ailerons (gives effect, as and balancing of rudder)...

 

and looks like you can be are correct, about compressibility...

 

i re-read your example about emil, and i re-read another interesting document, which i found long time ago, there have good short description of flutter on lagg and there, apparently, mentioned exactly "compressibility", plus could be little about soviet compressible aerodynamics research (in text is "трение", i think)...

 

it's will be very interesting for you or any people who interested in, but full translation could be very hard, so, i can only a bit help...

 

 

1 июля 1942 Тараканов ознакомил Пышнова и Доброхотова с Техническим отчетом ЦАГИ N 10 по опыту борьбы с флаттером на серийных самолетах (СБ (АНТ-40), ЛаГГ-3 и ТБ-3 (АНТ-6)), подготовленный Е.П.Гроссманом и М.В.Келдышем

Исполнители Е.П.Гроссманом и М.В.Келдышем

Общее заключение: цель настоящего отчета дать описание явления флаттера, наблюдающегося нап некоторых серийных с-тах и мер, применением которых достигается его устранение. На с-тах СБ, ЛаГГ-3 и ТБ-3 наблюдались случаи флаттера, связанные с органами управления: на с-те СБ - изгибно-элеронный флаттер, а на с-тах ЛаГГ-3 и ТБ-3 - флаттер руля направления.

...

Флаттер с-та ЛаГГ-3

С-т ЛаГГ-3 имел уровновешенные элероны и РВ, сбалансированные согласно расчету, по которому требовалась его перебалансировка. Руль направления сбалансирован не был При заводских испытаниях серийных с-тов на ряде из них наблюдалась сильная тряска при скорости по прибору порядка 590-630 км/час. При снижении скорости тряска прекращалась и, как правило, ни к каким поломкам не приводила. У части же с-тов тряска вообще не наблюдалась Специальные исследования вибрации с-тов ЛаГГ-3 были предприняты в связи с происшедшей аварией одного из с-тов. При пикировании на этом с-те при скорости по приборам около 620 км/час возникли сильные вибрации с-та. Л-к снизил скорость и вибрации пракратились. После этого л-к, в соответствии с заданием на полет, совершил два захода на стрельбу и затем, обнаружив необычное ощущение управления, пошел на посадку. Посадка была совершена с небольшим плюхом, т.к. неожиданно не хватило рулей. После посадки было обраружено разрушение фюзеляжа возле люка, находящегося на боковой стенке вблизи оперения. В обшивке фюзеляжа были трещины, идущие от углов люка, почти поперек фюзеляжа вверх и вниз, заходящие на плоскость симметрии с-та. По всей длине трещин были разрушены стрингеры и лонжероны фюзеляжа Характер поломок показывал разрушение от кручения ф-жа.

Увеличение балансира РВ не дало положительного рез-та. Произведенная затем проверка показала, что элероны с-та уравновешены не полностью. После этого балансировка элеронов была доведена до 105% и одновременно установкой балансиров был уравновешен РН на 100% на нижнем и верхнем концах руля. Эти мероприятия привели к уничтожению флаттера.

В связи с тем, что перебалансировку РВ вредно отразилась на управляемости с-та, ЛИИ НКАП были предприняты полеты с целью выяснения возможности ее уменьшения и одновременно исследовались возможности уменьшения балансировки РН. В первом полете балансировка РВ была доведена до 100%. С-т пикировал со скоростью свыше 700 км/час и никаких признаков наступления флаттера было не обнаружено. Этот результат был подтвержден на вторичных полетах.

На с-те, из соображений безопасности, вызываемых возможностью небольших колебаний весовых характеристик, был установлен балансир, дающий незначительную перебалансировку РВ. После этого приступили к полетам с уменьшенным балансиров РН. Сначала были произведены полеты без нижнего балансира, показавшие отсутствие флаттера.Когда был снат и верхний балансир РН, то в первом же полете наступил флаттер на скорости 620-630 км/час., вызвавший разрушения, аналогичные тем, которые имели место в описанном выше случае. Это позволило ракомендовать сохранение (или оставление) на РН только верхнего балансира, доведя его вес до 2,5 кг (при плече 265 мм).

Представлет интерес сравнение частоты флаттера с собственными частотами фюзеляжа. Частота флаттера, записанная в ЛИИ при помощи самописца отклонения рулей, равнялась 780 кол./минуту. Эта частота ближе к собственным частотам фюзеляжа. Для фюзеляжа собственная частота колебаний кручения равна 880 к/м, а собственная частота колебаний изгиба фюзедляжа в горизонтальной плоскости - 800 к/м.

Критическая скорость флаттера ВО была расчитана по способу, разработанному в ЦАГИ Е.П.Гроссманом в самое последнее время (см. ТО ЦАГИ № 12, 1942). Расчет дал значение критической скорости без балансира РН, равное 554 км/час и частоту флаттера 744 к/м, а при наличии верхнего балансира - скорость 814 км/час, что удовлетворительно согласуется с результатами полетных испытаний. Следует опять отметить, что вследствие пренебрежения трением расчет дает максимальное значение критической скорости, которое на с-те в действительности значительно превосходилась вследствие наличия трения.

...

Заключение:

При флаттере органов управления большую роль играет трение. Благодаря ему критическая скорость флаттера м.б. значительно превзойдена, а в некоторых случаях флаттер может вообще не возникнуть.

Единственный полет недостаточен для установления безопасности машины в отношение флаттера. Безопасность машины от флаттера может быть обеспечена при минимально возможном трении. Значение критической скорости при отсутствии трения устанавливается расчетно.

Во всех известных случаях флаттера органов управления колебания конструкции нарастают сравнительно медленно и их можно погасить уменьшением скорости полета, для чего необходимо сбросить газ и взять ручку (штурвал) на себя (761).

 

 

(from great "Rodionov's Chronology", and you can use "RC" too, it's free, but for clear understanding absolutely need to know russian)

 

Would be great to see what data devs use, just for comparison.

i already quoted of developer, and this in good agreement with other documents, which i have, in total, planes with modernized controls have realistic dive speed = 680-690 kph TAS...

[Crump]

S!

 

 Would be great to see what data devs use, just for comparison. In game you can safely dive well over 800km/h IAS before parts stat flying off and even before that there is no shaking or whatever. And yes, FM is not done yet I know.

 

 

They are pretty much going to have to make a judgment call on how the mach limits are handled.  It is up to them and to me it is really not a big deal.  Think of it this way, with all the different "yardsticks" used to measure compressibility corrections at the time, it is impossible for anyone to claim specific aircraft mach limits are unrealistic.

 

What I would do is convert Calibrated Airspeed to EAS with a universal compressibility correction for the game.  Get the dive acceleration results and just use the POH limits as the onset of bad things.  It would not be unrealistic for specific aircraft results because we need a lot more information about all of the combatants in WWII which I don't think is practical unless we want to pay a couple of thousand bucks per model.

 

It is realistic behavior for the pilots and gameplay. 

 

A lot can come out in the wash, too.

 

For example, here is a Position Error Correction Curve a friend did up plotting PEC data from several POH's:

 

 

First thing that struck us was the Soviet airspeed indicator slope was reversed from everyone else! It is not unheard of but it is not common.

[bivalov]

btw, about dive limit for la- type 37 of early series (which very similar with lagg-3 of late series, if i not mistaken), from pilot manual'42 - "Пикирование... Ввод в пикирование производится с разворота или с переворота. Пикирование разрешается производить до скорости 625 км/час по прибору." - limit is 625 kph IAS...

[LLv34_Flanker]

S!

 

 Bivalov, that manual pretty much is in line with the Finnish pilots saying diving away from VVS planes was easy as they could not follow. I also recall reading that even the HSU Ivan Kozhedub saying La-7 had problems in high speed dives by shaking violently. Any info on the La-7, Bivalov? Could it be that even it was extremely fast at low to medium altitudes, the structure was pretty much too weak for any higher speeds?

[sturmkraehe]

Is there information about temperature limits for this plane? I try to watch mine but since I don't know the limits it's hard to say when I should go piano with my engine.

[LLv34_Flanker]

S!

 

 There is no direct info on those papers. Just a tidbit where pilot noted that plane did not overheat when climbing with full radiator open and not using the highest power setting. The so called boost had a very small effect if any according to this report. But I will ask around and get some extra info on the issue and LaGG-3 in FiaF. Can take a bit, but I hope to find something.

[Crump]

S!

 

 Bivalov, that manual pretty much is in line with the Finnish pilots saying diving away from VVS planes was easy as they could not follow. I also recall reading that even the HSU Ivan Kozhedub saying La-7 had problems in high speed dives by shaking violently. Any info on the La-7, Bivalov? Could it be that even it was extremely fast at low to medium altitudes, the structure was pretty much too weak for any higher speeds?

 

 

The La-5FN POH I have list's 650 kph IAS for the type in October 1944.

 

la-5manual.pdf

 

[Crump]

I can't share the original Russian version.  The forum won't let me up load zip files. 

 

 

[LLv34_Flanker]

S!

 

 Maybe too big ones? Try to chop them into smaller ones

[Crump]

 

as written in pilot manual'43, and said developer who got original report, yes, 600 IAS ... 

 

meanwhile 700 IAS, really, is speed during tests of first serial planes (before war, if i not mistaken)... 

 

if i understood you correctly, you are absolutely correct...

 

in total, personally my opinion about modernisation - all early lagg-3 are without balancers > after tests (at 600 > 700 > ??? IAS), lagg-3 got 2 balancers on rudder (~1-4 series and, maybe, later), or only 1 upper balancer a bit later (~7 series) > somewhere in early'42 rudder was modernized (i checked several drawings and some info, yep, starting from lagg-3 ~23 series instead upper balancer, a bit another rudder with "aerodynamical compensation")...

 

this is just because i wrote from my memory, and was not sure... but there really were re-balancing of elevators (no effect) and re-balancing of ailerons (gives effect, as and balancing of rudder)...

 

and looks like you can be are correct, about compressibility...

 

i re-read your example about emil, and i re-read another interesting document, which i found long time ago, there have good short description of flutter on lagg and there, apparently, mentioned exactly "compressibility", plus could be little about soviet compressible aerodynamics research (in text is "трение", i think)...

 

it's will be very interesting for you or any people who interested in, but full translation could be very hard, so, i can only a bit help...

 

 

1 июля 1942 Тараканов ознакомил Пышнова и Доброхотова с Техническим отчетом ЦАГИ N 10 по опыту борьбы с флаттером на серийных самолетах (СБ (АНТ-40), ЛаГГ-3 и ТБ-3 (АНТ-6)), подготовленный Е.П.Гроссманом и М.В.Келдышем

Исполнители Е.П.Гроссманом и М.В.Келдышем

Общее заключение: цель настоящего отчета дать описание явления флаттера, наблюдающегося нап некоторых серийных с-тах и мер, применением которых достигается его устранение. На с-тах СБ, ЛаГГ-3 и ТБ-3 наблюдались случаи флаттера, связанные с органами управления: на с-те СБ - изгибно-элеронный флаттер, а на с-тах ЛаГГ-3 и ТБ-3 - флаттер руля направления.

...

Флаттер с-та ЛаГГ-3

С-т ЛаГГ-3 имел уровновешенные элероны и РВ, сбалансированные согласно расчету, по которому требовалась его перебалансировка. Руль направления сбалансирован не был При заводских испытаниях серийных с-тов на ряде из них наблюдалась сильная тряска при скорости по прибору порядка 590-630 км/час. При снижении скорости тряска прекращалась и, как правило, ни к каким поломкам не приводила. У части же с-тов тряска вообще не наблюдалась Специальные исследования вибрации с-тов ЛаГГ-3 были предприняты в связи с происшедшей аварией одного из с-тов. При пикировании на этом с-те при скорости по приборам около 620 км/час возникли сильные вибрации с-та. Л-к снизил скорость и вибрации пракратились. После этого л-к, в соответствии с заданием на полет, совершил два захода на стрельбу и затем, обнаружив необычное ощущение управления, пошел на посадку. Посадка была совершена с небольшим плюхом, т.к. неожиданно не хватило рулей. После посадки было обраружено разрушение фюзеляжа возле люка, находящегося на боковой стенке вблизи оперения. В обшивке фюзеляжа были трещины, идущие от углов люка, почти поперек фюзеляжа вверх и вниз, заходящие на плоскость симметрии с-та. По всей длине трещин были разрушены стрингеры и лонжероны фюзеляжа Характер поломок показывал разрушение от кручения ф-жа.

Увеличение балансира РВ не дало положительного рез-та. Произведенная затем проверка показала, что элероны с-та уравновешены не полностью. После этого балансировка элеронов была доведена до 105% и одновременно установкой балансиров был уравновешен РН на 100% на нижнем и верхнем концах руля. Эти мероприятия привели к уничтожению флаттера.

В связи с тем, что перебалансировку РВ вредно отразилась на управляемости с-та, ЛИИ НКАП были предприняты полеты с целью выяснения возможности ее уменьшения и одновременно исследовались возможности уменьшения балансировки РН. В первом полете балансировка РВ была доведена до 100%. С-т пикировал со скоростью свыше 700 км/час и никаких признаков наступления флаттера было не обнаружено. Этот результат был подтвержден на вторичных полетах.

На с-те, из соображений безопасности, вызываемых возможностью небольших колебаний весовых характеристик, был установлен балансир, дающий незначительную перебалансировку РВ. После этого приступили к полетам с уменьшенным балансиров РН. Сначала были произведены полеты без нижнего балансира, показавшие отсутствие флаттера.Когда был снат и верхний балансир РН, то в первом же полете наступил флаттер на скорости 620-630 км/час., вызвавший разрушения, аналогичные тем, которые имели место в описанном выше случае. Это позволило ракомендовать сохранение (или оставление) на РН только верхнего балансира, доведя его вес до 2,5 кг (при плече 265 мм).

Представлет интерес сравнение частоты флаттера с собственными частотами фюзеляжа. Частота флаттера, записанная в ЛИИ при помощи самописца отклонения рулей, равнялась 780 кол./минуту. Эта частота ближе к собственным частотам фюзеляжа. Для фюзеляжа собственная частота колебаний кручения равна 880 к/м, а собственная частота колебаний изгиба фюзедляжа в горизонтальной плоскости - 800 к/м.

Критическая скорость флаттера ВО была расчитана по способу, разработанному в ЦАГИ Е.П.Гроссманом в самое последнее время (см. ТО ЦАГИ № 12, 1942). Расчет дал значение критической скорости без балансира РН, равное 554 км/час и частоту флаттера 744 к/м, а при наличии верхнего балансира - скорость 814 км/час, что удовлетворительно согласуется с результатами полетных испытаний. Следует опять отметить, что вследствие пренебрежения трением расчет дает максимальное значение критической скорости, которое на с-те в действительности значительно превосходилась вследствие наличия трения.

...

Заключение:

При флаттере органов управления большую роль играет трение. Благодаря ему критическая скорость флаттера м.б. значительно превзойдена, а в некоторых случаях флаттер может вообще не возникнуть.

Единственный полет недостаточен для установления безопасности машины в отношение флаттера. Безопасность машины от флаттера может быть обеспечена при минимально возможном трении. Значение критической скорости при отсутствии трения устанавливается расчетно.

Во всех известных случаях флаттера органов управления колебания конструкции нарастают сравнительно медленно и их можно погасить уменьшением скорости полета, для чего необходимо сбросить газ и взять ручку (штурвал) на себя (761).

 

 

(from great "Rodionov's Chronology", and you can use "RC" too, it's free, but for clear understanding absolutely need to know russian)

 

i already quoted of developer, and this in good agreement with other documents, which i have, in total, planes with modernized controls have realistic dive speed = 680-690 kph TAS...

 

I think you are right.

 

If you look at the PEC curve of the La-7, 600 kph IAS = 757kph TAS at 15,000 feet.  Assuming the earlier Lavochkin designs have a similar slope PEC curve, 680-690 kph True Airspeed is easily attainable.

 

Is there a Position Error Curve in any of the Lagg 3 series 35 reports? 

 

 

Maybe too big ones? Try to chop them into smaller ones

 

The forum won't let me upload the La-5FN original manual, it keeps giving me "Error You aren't permitted to upload this kind of file" when I zip, rar, or 7zip the file into smaller sizes to meet the 5MB upload limit.

Edited May 8, 2014 by Crump

[LLv34_Flanker]

S!

 

 There were some error curves on the gauges. I thought I attached them. Let me double check and post them if not there

[Crump]

I might have just missed them.

[LLv34_Flanker]

S!

 

 They are there on 1st page For the RPM, manifold pressure, speed gauges. After the picture of the LG-3. Altitude seems to be in the tables.

Edited May 8, 2014 by LLv34_Flanker

[Crump]

I know, I just missed it. 

 

 

Just extend the line and the scale at the same slope and graduation.  You will have a reasonable idea of what the aircraft's TAS was in a dive converting from IAS to TAS!

[bivalov]

Any info on the La-7, Bivalov? Could it be that even it was extremely fast at low to medium altitudes, the structure was pretty much too weak for any higher speeds?

la-7 it's almost la-5fn, in total, and i dont think that dive limits could be different, or really different, looks like it's still ~700 TAS, maybe, with some new "features" in behavior...

 

most likely i has something, but absolutely not sure, because cant remember any mentions and i even not sure that detailed information have in RUnet...

 

...and not using the highest power setting. The so called boost had a very small effect if any according to this report.

ie really, during tests, full power of m-105pf is not used? this is looks a bit strange, and definitely affects on performance...

 

But I will ask around and get some extra info on the issue and LaGG-3 in FiaF. Can take a bit, but I hope to find something.

i exactly wanted to ask - you finished with s35, or will be more posts? looks like you almost finished, but you will try to get something more? that's good...

 

AND... i have next question for you (or any finns here) - i sure, that you know about these debates about 1.42 ata for bf 109 f-4, on russian forum and here, plus i mentioned debates about g-2 1.42 (as showed Kurfurst, it's almost correctly for end'42, so, i tried to ask devs, but absolutely unsuccessfully)...

 

so, my question is - maybe, finns as famous users of bf 109, and because they appreciate their history, retained full documentation for bf 109?

 

especially, besides handbuchs for plane (i seen english translation of german-finnish handbuchs for g-2/6), engine, etc, i mean "Betriebsdatentafeln" which had in each plane, and where could be found limitations for engine? that's could be very interesting, and even if it's not need for game, it's important part of history of 109...

[LLv34_Flanker]

S!

 

 LA-7 was a refined design from La-5FN. More metal used, re-located oil cooler and other smaller details making it a new plane. Interesting tidbit is that because the oil cooler was located further back and the hot oil ran below the pilot it caused some extra heat in the cockpit. But let's not derail the issue here, we are talking about LaGG-3 Series 35.

[bivalov]

I think you are right.

 

If you look at the PEC curve of the La-7, 600 kph IAS = 757kph TAS at 15,000 feet.  Assuming the earlier Lavochkin designs have a similar slope PEC curve, 680-690 kph True Airspeed is easily attainable.

 

Is there a Position Error Curve in any of the Lagg 3 series 35 reports?

btw, really, on first page mentioned 600 IAS and 700 (looks like TAS)... maybe, "RC" has more information about dive speeds, but i not sure, looks like no...

 

LA-7 was a refined design from La-5FN. More metal used, re-located oil cooler and other smaller details making it a new plane.

but structural strength and design, almost identical...

[LLv34_Flanker]

S!

 

 Some nice pics of the LG-3 here: http://mig3.sovietwarplanes.com/lagg3/lg3/lg3.html and the background of it: http://mig3.sovietwarplanes.com/lagg3/57/white57.html

Edited May 10, 2014 by LLv34_Flanker

[bivalov]

yep, very interesting mentions there (including modifications, which could affect on performance, and exactly these changes is also was not rare thing in VVS), but you said that you not finished your work, so, personally i not do final conclusions...

[Crump]

You can see the careful attention to drag reduction as part of the Lavochkin designs by the large effect configuration has on the performance.

 

 

 

 

 

 

[Crump]

btw, really, on first page mentioned 600 IAS and 700 (looks like TAS)... maybe, "RC" has more information about dive speeds, but i not sure, looks like no...

 

 

but structural strength and design, almost identical...

 

 

Turn radius when pulling out of a dive

 

        70-80deg dive, 600km/h IAS, starting altitude 4000m. Pull out started at 2800m, R=1250-1300m, 10sec. , altitude loss 700m.

 

 

I don't think they actually measure dive speed and are you sure you are not confusing altitude loss with dive speed achieved in the test?

[bivalov]

I don't think they actually measure dive speed and are you sure you are not confusing altitude loss with dive speed achieved in the test?

maybe, just this value in good agreement with other documents, and i seriously not thinking about altitude loss...

[Crump]

Ok!  BTW, I just found this too in my archive, I believe it is the Lagg-3 Operating Instructions!

 

lagg3.pdf

[79_vRAF_Friendly_flyer]

La-5FN configuration effects.jpg

 

Man, I love those old instruction cartoons.

[bivalov]

Flanker, pls, sorry for small offtop...
 

Ok! BTW, I just found this too in my archive, I believe it is the Lagg-3 Operating Instructions!

yes, this is well known pilot manual for lagg-3 (dated 10 july 1943), and it's source of 550/600 kph IAS...

AND...

today i remembered that recently was found new pilot manual for lagg-3 (dated 13 september/23 october 1942) - btw, many thanks to Wad, for this great document - i checked this, and was surprised that dive limit it's 650 kph IAS... i think, it's also in good agreement with other documents for lagg-3 or la-5...

 

plus i cheсked very detailed "методические указания по технике пилотирования самолета ла-5 с мотором м-82" (dated 12 july 1943, again, found Wad), there 625 kph IAS too...

[Crump]

Flanker, pls, sorry for small offtop...

 

yes, this is well known pilot manual for lagg-3 (dated 10 july 1943), and it's source of 550/600 kph IAS...

 

AND...

 

today i remembered that recently was found new pilot manual for lagg-3 (dated 13 september/23 october 1942) - btw, many thanks to Wad, for this great document - i checked this, and was surprised that dive limit it's 650 kph IAS... i think, it's also in good agreement with other documents for lagg-3 or la-5...

 

plus i cheсked very detailed "методические указания по технике пилотирования самолета ла-5 с мотором м-82" (dated 12 july 1943, again, found Wad), there 625 kph IAS too...

 

 

Only thing that worries me is the timeline does not add up for the Lagg-3 for an increase in dive limitation, it looks more like they restricted it. 

 

10 July 1943 limits the Lagg 3 to 600 kph IAS which is some 9 months after the 650kph IAS dive limit.

 

So, we should have faster dive limits with tail flutter?  I am not sure of the timeline for the technical changes on the Lagg 3. 

[LLv34_Flanker]

S!

 

 The altitude loss means how much altitude it took for the plane to get from a dive to level flight. Check the numbers. Pullout started at 2800m, altitude loss aka how much altitude plane still lost before leveling was 700m. The data was measured with Mata Hari flight data recording equipment I did mention earlier. The plane was repaired to good condition, if not better, than it was when in service with VVS. The modifications, like tailwheel bolted down, was due unreliable operation of the mechanism. This can be seen in some Yak-1/9 pictures as well, planes fly with tailwheels retracted but the doors are hanging open etc. The tests were made BEFORE the modifications after the planes were overhauled and repaired after capture.

 

 Regarding spare parts. A lot of them were bought from German war loot storages. Germans did capture a lot of Soviet equipment in very good condition, like a batch of Mig-3 planes that Finland wanted to buy from Germans but got bombed in the train in their crates etc. The SB/DB/Pe bombers were also acquired from German surplus of war loot and then operated by FiAF.

[bivalov]

Only thing that worries me is the timeline does not add up for the Lagg-3 for an increase in dive limitation, it looks more like they restricted it. 

 

10 July 1943 limits the Lagg 3 to 600 kph IAS which is some 9 months after the 650kph IAS dive limit.

 

So, we should have faster dive limits with tail flutter?  I am not sure of the timeline for the technical changes on the Lagg 3.

 

here could be next thing - at mid'43 lagg used mainly in second line... ie, it's care about resource of mainly old planes...

 

(meanwhile, sept'42 it's midpoint of BOS, or midpoint of war)

 

and new, or almost new planes, starting from autumn-winter'42, it's only modernized planes of 31 aviation plant in Tbilisi (now they a bit mistakenly named as "66 series", in fact, it's ~60-7X series)... moreover, these planes much more faster (~30 kph), lighter (~185 kg) > structural strength a bit less, plus i not sure that rudder also was changed (looks like, really, still old)...

 

but this is just fast attempt to explain...

 

and what about game, i not want to do conclusions, without all facts, which possible to get, and i just dont know in-game dive limit...

 

Only thing that worries me is the timeline does not add up for the Lagg-3 for an increase in dive limitation, it looks more like they restricted it. 

 

...I am not sure of the timeline for the technical changes on the Lagg 3.

i just repeat my opinion -

 

"all early lagg-3 are without balancers > after tests (at 600 > 700 > ??? IAS), lagg-3 got 2 balancers on rudder (~1-4 series and, maybe, later), or only 1 upper balancer a bit later (~7 series) > somewhere in early'42 rudder was modernized (i checked several drawings and some info, yep, starting from lagg-3 ~23 series instead upper balancer, a bit another rudder with "aerodynamical compensation")..."

[Crump]

 

here could be next thing - at mid'43 lagg used mainly in second line... ie, it's care about resource of mainly old planes...

 

 

 

Possibly they encountered the tail flutter and Lagg 3 development was abandoned in favor of the La-5 series so they did not waste effort in an aircraft that was being replaced or the design changes were incorporated in the La-5 series without wasting effort/resources to upgrade the Lagg 3 design.

 

It looks like the in game Lagg 3 should have the higher dive limits and could encounter tail flutter.  What do you think?

 

That is what it looks like the Pilot's Operating Instructions tell us.

Edited May 11, 2014 by Crump