Fokker D.XXI

[Vaeltaja]

And Jane's publications are - probably according to your commentary - renown for their errors and lies.. That is probably the reason why they are still in use...

EDIT: As for reliability of Finnish tests... http://forum.axishistory.com/viewtopic. ... 5#p1500546 While Finnish insist that SB-2 could not make even 400 kph...

[Juha Tompuri]

So let me get this straight.. You refuse to acknowledge any result other than Finnish result and then claim that you are just using your common sense?

Finnish tests are the only ones so far from we have accurate information regarding power settings, altitude, weight, time, place etc. It's not science if you've a hundred results without test settings or explanations who they were obtained.

Yep.

If you want to prove the generally (apart from you apparently) accepted results to be false then you should really need to show some proof that the listed values - in several published works - are wrong instead of just claiming that as it seems that for you any results deviating from the Finnish values are false.

Who has accepted these results of yours? I have not, Juha has not and I think most of the readers in this thread have not. Nowadays anyone can publish a book, it is not a guarantor of quality. All we know those speeds could have been copies from a common source!

The Vaeltaja sources, the specially selected three:

the one which is the most representative of the lot

seem to originate from two sources: Green and Kamphuis from early-mid 60's
Both incorrect about the Wasp Fokker technical data.

Seems also include sourceless "results".
Anyway, to have sources mentioned, means nothing, if the initial sources are not reliable.

As said the source is there, feel free to check it before you begin to complain.

Are these claims you posted, sourced?
http://www.pilotfriend.com/photo_albums ... 20DXXI.htm


Regards, Juha

[Vaeltaja]

The Vaeltaja sources, the specially selected three:

the one which is the most representative of the lot

seem to originate from two sources: Green and Kamphuis from early-mid 60's
Both incorrect about the Wasp Fokker technical data.

The ones i posted were just the few i quickly located. All which had data which was consistent with other sites and books. Until you can prove - instead of postulate - that the errors creep from certain sources there are the Finnish results (which as we have seen from SB-2 data can be faulty) and then there are the values listed everywhere else.

Are these claims you posted, sourced?
http://www.pilotfriend.com/photo_albums ... 20DXXI.htm

Precisely what i expected you to post. Instead of checking the sourced sites - and their sources - you selected the one which lacked the sources and seemingly use it like evidence that rest of the sites wouldn't have had sources listed.

[Mangrove]

The 1937 editions of Jane's All the World's Aircrafts has a maximum speed of 446 km/h at 4,420 meters with 1950 kg ("loaded weight") for Fokker D.21 with Mercury VII. The weight is close to Finnish 1970 kg, but the speed is not. I suspect this is because the only source Jane's could get the information in 1936/1937 was directly from the factory and thus the speed is archived with factory settings.

[Juha Tompuri]

The 1937 editions of Jane's All the World's Aircrafts has a maximum speed of 446 km/h at 4,420 meters with 1950 kg ("loaded weight") for Fokker D.21 with Mercury VII. The weight is close to Finnish 1970 kg, but the speed is not. I suspect this is because the only source Jane's could get the information in 1936/1937 was directly from the factory and thus the speed is archived with factory settings.

Thanks.
That explains much.

The Vaeltaja sources, the specially selected three:

the one which is the most representative of the lot

seem to originate from two sources: Green and Kamphuis from early-mid 60's
Both incorrect about the Wasp Fokker technical data.

The ones i posted were just the few i quickly located.

I try to choose the one which is the most representative of the lot

All which had data which was consistent with other sites and books. Until you can prove - instead of postulate - that the errors creep from certain sources there are the Finnish results (which as we have seen from SB-2 data can be faulty) and then there are the values listed everywhere else.

As mentioned several times earlier by me and Martti, the only (real and accurate) test reports and measurements of the (Wasp) Fokkers come only from Finnish sources. From the only operator and the only origin of the tests.
The ones you have brought to us are seemingly not based on Finnish origin data and history, but perhaps some misunderstandings or estimates.
Or even Fiction.

Are these claims you posted, sourced?
http://www.pilotfriend.com/photo_albums ... 20DXXI.htm

Precisely what i expected you to post. Instead of checking the sourced sites - and their sources

Wrong guess.
Perhaps because of your lack of understanding or just bad memory?

And as said those seemed to have source references mentioned. Feel free to check it from there.

Seems also include sourceless "results".
Anyway, to have sources mentioned, means nothing, if the initial sources are not reliable

- you selected the one which lacked the sources and seemingly use it like evidence that rest of the sites wouldn't have had sources listed.

As above.

Regards, Juha

[Vaeltaja]

As mentioned several times earlier by me and Martti, the only (real and accurate) test reports and measurements of the (Wasp) Fokkers come only from Finnish sources. From the only operator and the only origin of the tests.
The ones you have brought to us are seemingly not based on Finnish origin data and history, but perhaps some misunderstandings or estimates.
Or even Fiction.

I was in understanding this was still about both Fokker D XXI types. And not solely about the Finnish Waspi-Fokkers. If you had read the posts you would have noticed (and understood) that i criticized on the top speed value Martti provided for Mercury Fokkers (415 kph) as it contradict the other sources. I only used the references to Waspi Fokkers to demonstrate the apparent problem with the top speed he listed. So far Mercury Fokkers have - at least - 3 different top speeds, 415 kph by Finns, 446 kph 1937 ed. Janes, and 460 kph found from several books and sites (both with and without sources) in web.

Wrong guess.
Perhaps because of your lack of understanding or just bad memory?

You apparently totally ignored the two sites with sources listed and instead concentrated only on the one which lacked the source reference. Exactly like i expected.

As for the one of the sites lacking source references... My bad. Must have mixed it up with some other site. Two other sites are still sourced regardless of your dismissal of the third.

[Juha Tompuri]

As mentioned several times earlier by me and Martti, the only (real and accurate) test reports and measurements of the (Wasp) Fokkers come only from Finnish sources. From the only operator and the only origin of the tests.
The ones you have brought to us are seemingly not based on Finnish origin data and history, but perhaps some misunderstandings or estimates.
Or even Fiction.

I was in understanding this was still about both Fokker D XXI types. And not solely about the Finnish Waspi-Fokkers.

Both types?
Both out of three?
As all your three sites mention there would have been a third (of course fictionary in reality) engine production type.

If you had read the posts you would have noticed (and understood) that i criticized on the top speed value Martti provided for Mercury Fokkers (415 kph) as it contradict the other sources.

I have read the posts and even managed to understood what you are after.

I only used the references to Waspi Fokkers to demonstrate the apparent problem with the top speed he listed.

I see there no problem.

And about the Wasp powered Fokkers case that you brought here in:

The 415km/h (or 418km/h as mentioned at Keskinen, Stenman, Niska SIH 3 book) was the officially measured Fokker D.XXI top level speed in Finland, take off weight being 1970kg and most probably done with full power.
Both books mention the normal cruising speed as 330km/h at 2000m
I'm quite reserved towards to Green figures - even the engine mentioned is different than in Finnish Fokkers.

That seems rather interesting as well. The Waspi-Fokkers were generally understood to have lower performance - including speed - than Mercury Fokkers and even they seem to be rated to have over 400 kph top speeds - some even at 438 kph.

wwiivehicles, pilotfriend.com, airwar.ru

Those mistakes might also originate from Green.
Btw... interesting engine info they seem to have at the airwar.ru Fokker site.

So far Mercury Fokkers have - at least - 3 different top speeds, 415 kph by Finns, 446 kph 1937 ed. Janes, and 460 kph found from several books and sites (both with and without sources) in web.

Yes, several speeds mentioned, but only the Finnish one able to be traced back to the exact plane, flying weight, flying height etc important additional info. The rest are without such detailed info - just claims, by so far.

Wrong guess.
Perhaps because of your lack of understanding or just bad memory?

You apparently totally ignored the two sites with sources listed and instead concentrated only on the one which lacked the source reference. Exactly like i expected.

So...
...seems this time lack of understanding.
Here we go, once again.
This time try to pay attention to the english fine word of also:

And as said those seemed to have source references mentioned. Feel free to check it from there.

Seems also include sourceless "results".
Anyway, to have sources mentioned, means nothing, if the initial sources are not reliable

As for the one of the sites lacking source references... My bad. Must have mixed it up with some other site. Two other sites are still sourced regardless of your dismissal of the third.

Now you seem to understand what you have posted.

Anyway, it seems that the three sites you brought in for some kind of of proofs of Wasp Fokker performance, seem to mainly originate from two sources.
As mentioned before:

the one which is the most representative of the lot

seem to originate from two sources: Green and Kamphuis from early-mid 60's
Both incorrect about the Wasp Fokker technical data.

Regards, Juha

[Mangrove]

Little more about the Jane's as a source; they also provide intelligence for Fokker D.21 with Hispano-Suiza 12crs:

Weight empty: 1,465 kg
Armament and equipment 245 kg.
Pilot: 80 kg.
Petrol and oil: 240 kg.
Weight loaded: 2,030 kg.
Wing loading: 126 kg.sq. m.
Power loading: 2.2 kg./h.p.

Maximum speed at 4,000 m. = 460 km/h
Cruising speed at 4,000 m. = 385 km/h
Climb to 1,000 m. = 1.45 mins.
Climb to 3,000 m. = 4 mins.
Climb to 5,000 m. = 6.8 mins.
Climb to 7,000 m. = 11.2 mins.

I have never heard of such engine option for Fokker. It seems this and maybe even the Mercury performance is based partly on mere calculations.

[Vaeltaja]

Both types?

As in Fokker D XXI with Mercury or Wasp engine, yes. If you considered some other engine variant to be important (within context of Winter and Continuation War) then feel free to append the list.

Yes, several speeds mentioned, but only the Finnish one able to be traced back to the exact plane, flying weight, flying height etc important additional info. The rest are without such detailed info - just claims, by so far.

That is as likely to show how inept Finnish ground crew was in maintaining and tuning the aircraft and its engines as it is to show that other data is wrong.

Here we go, once again.
....

Which does not really explain why you summarily dismissed the other two sites out of hand.

Anyway, it seems that the three sites you brought in for some kind of of proofs of Wasp Fokker performance, seem to mainly originate from two sources.

They were about Fokker performance in general not as specific Wasp Fokker resources.

[Juha Tompuri]

Little more about the Jane's as a source; they also provide intelligence for Fokker D.21 with Hispano-Suiza 12crs

Thanks, that version could have been quite interesting also to have at Finnish AF service.

I have never heard of such engine option for Fokker. It seems this and maybe even the Mercury performance is based partly on mere calculations.

That version was only at paper, as also the RR Kestrel, RR Merlin, Bristol Hercules and DB 600.

Both types?

As in Fokker D XXI with Mercury or Wasp engine, yes. If you considered some other engine variant to be important (within context of Winter and Continuation War) then feel free to append the list.

All the three sites you have brought up here claim that the three last Fokkker D.XXI's were built to have Bristol Pegasus engines.
Which is fiction of course.

So far Mercury Fokkers have - at least - 3 different top speeds, 415 kph by Finns, 446 kph 1937 ed. Janes, and 460 kph found from several books and sites (both with and without sources) in web.

Yes, several speeds mentioned, but only the Finnish one able to be traced back to the exact plane, flying weight, flying height etc important additional info. The rest are without such detailed info - just claims, by so far.

That is as likely to show how inept Finnish ground crew was in maintaining and tuning the aircraft and its engines as it is to show that other data is wrong.

You are now again barking up the wrong tree:
Finnish mechanics worked wery well during the war years, and for instance they were quite good with the Mercury engines, as can be remembered from the Finnish data about Bristol Blenheim performance.
Or the Finnish mechanics improvements to the Brewster F2A Cyclone engines.

Here we go, once again.
....

Which does not really explain why you summarily dismissed the other two sites out of hand.

As for the one of the sites lacking source references... My bad. Must have mixed it up with some other site. Two other sites are still sourced regardless of your dismissal of the third.

Again:
You posted three links, and claimed that they seemed to be sourced.
As mentioned above, you mixed up things, and actually one of the links contained unsourced incorrect info, the two others having sourced incorrect info.

Anyway, it seems that the three sites you brought in for some kind of of proofs of Wasp Fokker performance, seem to mainly originate from two sources.

They were about Fokker performance in general not as specific Wasp Fokker resources.

That seems rather interesting as well. The Waspi-Fokkers were generally understood to have lower performance - including speed - than Mercury Fokkers and even they seem to be rated to have over 400 kph top speeds - some even at 438 kph.

wwiivehicles, pilotfriend.com, airwar.ru

Regards, Juha

[Juha Tompuri]

Some notes about the http://www.wwiivehicles.com/netherlands ... -d-xxi.asp info:

Production

* VL (Finnish State Factory): 90

Correct.

Finland

In 1937 Finland ordered seven production models and an agreement was made to allow the Finns to license built the D.XXI.

Correct again.

The State Aircraft Factory constructed 93 fighters during 1938 to 1944.

Wrong.
Here the site is contradicting to itself and to the correct info just earlier mentiond.

The first 38 had Bristol engines. The next 50 had American Pratt & Whitney Twin Wasp Junior radial engines (836 HP). The last five had Bristol Pegasus engines.

None of the production numbers matches with the reality, and the info about five of the last D.XXI's been powered with Pegasus engines is pure fiction.

Usage

Finland

The Finnish air force had over 100 D.XXIs.

Wrong.
Here the site manages to disagree with the right and also with the wrong info just earlier claimed.

The Wasp Fokker technical table at the end the site (based on Green) seems to be wrong exept the plane name, engine type, cylinder arrangement and number, power output and wing span.


Some notes about the http://www.pilotfriend.com/photo_albums ... 20DXXI.htm site:

Variants



D.XXI-3 - Finland received 7 D.XXI-2's, and was licensed to build their own aircraft, resulting in the D.XXI-3. 38 were built, and delivered in 1939, and played an important role in the Winter War against the invading USSR-forces. The D.XXI-3 was equal to the D.XXI-2 in all respects. The powerplants were one PZL or Tampella (Bristol) Mercury VII radial engine made in Poland or Finland respectively. Number built: 38.

The number of Fokker built planes is correct, but the number of Finnish built Mercury engined planes is wrong.
Also all the Finnish Mercury engined planes were built powered by Finnish Mercuries.
Not Polish.

D.XXI-4 - The D.XXI-4 was powered with a different engine as supplies of the Finnish-built Mercury radial were earmarked for the VL license-built version of the Bristol Blenheim. Finland had bought 80 Twin Wasp R-1535-SB4C-G Junior engines, rated at 825 hp (615 kW), from the USA in 1940, and production of the D.XXI-4 with this engine totalled 50 aircraft. This variant had a slight degradation of performance and agility. Other major changes from the D.XXI-3 standard were the armament of four 7.7 mm (0.303 in) machine-guns in the wing leading edges, a larger vertical tail surface for continued directional stability despite the larger engine, and the rearward extension of the cockpit glazing to provide the pilot with larger fields of vision.

Mostly correct, but the " slight degradation of performance and agility" in nonsense.
The Fokkers with Twin Wasp Junior engines planes fell from fighter status to trainer status.

The details of the D.XXI-4 included a span of 36 ft 1 in (11.00 m), an aspect ratio of 7.47 and an area of 174.375 sq ft (16.20 sq m). Length was 27 ft 9 in (8.46 m), and height was 9 ft 8 in (2.95 m). It had an empty weight of 3,384 lbs (1535 kg), with a maximum take-off weight of 4,817 lbs (2185 kg). Maximum level speed of 270 mph (435 km/h) at 9,020 ft (2750 m), cruising speed of 220.5 mph (355 km/h) at 9,020 ft (2750 m), climb to 9,845 ft (3000 m) in 4 minutes 30 seconds, and a service ceiling of 31,990 ft (9.750 m). Number built: 50.

As earlier mentiond, the Green information about Wasp Fokkers earlier, and also later this site, is not correct (strangely the wing span happens to be correct), as is not the number of the Wasp powered Fokkers mentioned at this site.

D.XXI-5 - Similar to the Fokker D.XXI-4, but with a Bristol Pegasus radial, rated at 920 hp (686 kW). Number built: 5.

Same fiction as at the earlier site.
Seems to come from Kamphuis.

Performance: (Mercury VIII) Maximum speed 286 mph (480 km/h)

Quite controversial info.

Armament:
(Finnish) Four 7.7 mm (0.303 in) Vickers machine guns in outer wings.

Did any Finnish Fokker have such an armament?


Some notes about the http://airwar.ru/enc/fww2/fokd21.html site:
(A bit difficult as I don't yet read Russian very well)

Пятого января капитан Йорма Сараванто с ведомым капитаном Совелиусом перехватили над Куопио семерку ДБ-3. Одного за другом Сараванто расстрелял 6 самолетов, даже не пытавшихся защищаться, а когда у него кончились патроны, последнего сбил ведомый. Позднее финны объявили, что среди останков сбитых машин они не нашли ни одного пулемета.

babelfish translation:

Fifth January captain [Yorm] [Saravanto] with consent by captain [Sovelius] they intercepted above [Kuopio] seven dB -3. One after the friend [Saravanto] it shot 6 aircraft, even not attempted to protect, but when in it ended cartridges, the latter brought down slave. Late Finns declared, that among the remains of the biased machines they found not one machine gun

No machineguns at the DB-3's ?

19 января в воздушном бою погиб сержант Тилли, а 30-го - лейтенанты Кархунен и Вуорела.

babelfish translation:

On January 19 in the air battle perished the sergeant Of [tilli], and the 30th - Lieutenants [Karkhunen] [Vuorela]

Ltn Karhunen died at Winter War?

Модификации :
D.XXI-1 с 645-сильным ПД Bristol Mercury VI-S. Одноместный истребитель-низкоплан,прототип; два собраны для ВВС Дании.

D.XXI-2 1937 года, с 760 л.с. ПД Bristol Mercury VIII. Вариант для ВВС Голландии и Финляндии.

D.XXI (1938 г.) с советским двигателем М-25. Испанский вариант.

D.XXI (1939-40 гг.) с 760-сильным ПД Bristol Mercury VIII. Датская лицензиозная модель; построено 10.Нес 20-мм подкрыльевые пушки Madsen.

D.XXI-3 с 760-сильным ПД Bristol Mercury VIII. Вариант с вооpужением в каплеобразных обтекателях; в 1939 построено 38 шт. для Финляндии.

D.XXI-E1 с 760-сильным ПД Bristol Mercury VIII. Экспериментальный вариант с резко выраженным сужением крыла к концу.

D.XXI-4 1941 год. с 1050-сильным ПД Pratt & Whitney R-1535 Twin Wasp Junior. Поставлено 50 шт.,вооpужение из фюзеляжа перенесено в кpыло.

D.XXI-5 1944 год, с 920-сильным ПД Bristol Pegasus X. Последняя партия из пяти финских машин.

Strange output figures for the Mercury VIII and Twin Wasp Junior engines.
Also the "usual" for your sources wrong Finnish Fokker production numbers and the funny "usual" claim of the last five Fokkers being powered by Pegasus engines.

Модификация Fokker D.XXI-4
Размах крыла, м 11.00
Длина, м 8.20
Высота, м 2.92
Площадь крыла, м2 16.20
Масса, кг
пустого самолета 1490
нормальная взлетная 2050
Тип двигателя 1 ПД Pratt Whitney R-1535 Twin Wasp Junior
Мощность, л.с. 1 х 1050
Максимальная скорость , км/ч 410
Крейсерская скорость , км/ч 334
Практическая дальность, км 880
Максимальная скороподъемность, м/мин
Практический потолок, м 9300
Экипаж 1

Seems that only the crew number and wing span are correct.

Вооружение: два 7,69-мм пулемета М.36 в передней части фюзеляжа с боекомплектом по 500 патронов на ствол и два кpыльевых пулемета М.36 с боекомплектом по 300 патронов на ствол.

babelfish translation:

Armament: two 7,69- mm of the machine gun Of [m].36 in the forward fuselage section with the fire unit on 500 cartridges to the stem and two [k]p[ylevykh] machine guns Of [m].36 with the fire unit on 300 cartridges to the stem

Wrong again.
At Wasp Fokkers (except at one) all the armament was at the wings.
Seems that the airwar.ru chaps had made a mistake when copying info from Kamphuis.
The original one was quite correct, but the text content was changed when leaving few words off.
Sort of funny, but also reveals the reliability of info from that site about Fokker D.XXI.
And also tells something about people who bring up here these kind of sources as an evidence of something.

Here the info seems to be at least quite correct:
http://www.saunalahti.fi/~ambush/faf/fokkerdxxi.html

Regards, Juha

[phylo_roadking]

Regarding the 460kph D.XXXI....Juha as a contributor may remember this http://www.ww2aircraft.net/forum/aviati ... 15060.html

The most interesting pages on this aspect of the D.XXI are pages 6-8.

[Juha Tompuri]

Thanks, never seen that before, looks interesting.

Regards, Juha

[phylo_roadking]

Ah, a different Juha then. Interesting that the OP does supply a source for a lot of his material right at the top of the thread, an indepth Dutch reference on the type.

[Vaeltaja]

And in the end you also post sites which clearly state that Fokker D XXI (Mercury) was able to go faster than 415kph claimed by Martti. Which was all that i was after (not trusting blindly the Finnish results) when the whole discussion started.