# Fokker D.XXI in Dutch service



## Marcel (Sep 22, 2008)

This thread is meant to cover the story of the D.XXI, while focussed on the service in The Netherlands. (I will probably bore the hell out of you  I'm mainly using Dutch sources as they are usually not accessible for non-dutch speaking people, like most of you. Sources are (amongst others): "Illusies en incidenten, Dutch Profile: Fokker D.XXI, , Stories of various Dutch pilots, Luchtoorlog Mei 1940, and many others.
If there is any bias (after all I'm Dutch) or inaccuracies, you're of course free to chime in. Info from other users (Denmark and Finland) is welcome if it adds to this story. As I will by quite busy in the coming months, it can sometimes take a while for me to pick up the thread again.


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## Marcel (Sep 22, 2008)

In May 1934, the KNIL (Royal Dutch East Indies Army) issued a specification for a new fighter in order to replace the Curtiss Hawk bi-plane, in use since 1930. The fighter had to operate under primitive conditions and thus had to be rugged and simple, with a fixed landing gear (many say the D.XXI had a fixed gear for financial reasons, but this is incorrect). The requested armament was remarkable, a fixed 12.7 mm MG and 2 adjustable 7.9mm MG’s (10° upwards and to the side). A small bomb load was also requested.

Fokker reacted with 2 designs, the D.XIX (an improved D.XVII) and desigin 112, a low wing monoplane powered by a RR Kestral engine. The latter was renamed the D.XXI and was favored above the D.XIX. In April 1935, Fokker was asked to redesign for the 645 hp Bristol Mercury VI engine. The adjustable MG’s proved to be troublesome and expensive, so they were dropped in favor of fixed MG’s in the wings.

The prototype with East-Indies registration FD-322 was finished in February 1936. The KNIL tested the a/c extensively. On May the 1st, during a spin test, the prototype fell into a nasty spin, from which it didn’t seem to recover. The pilot decided to bail out, but got control again while trying to jump. He landed and shouted to the spectators to use a match and burn it. The KNIL decided not to use the a/c. A german test pilot then completed the test and showed that the D.XXI could perform spins without trouble but the KNIL had changed strategy. It planned one a strong bomber force and the Fokker fighter wasn’t needed anymore. 

The only D.XXI to reach the Dutch East Indies was the prototype FD-322. What happened to the a/c is unclear. Some sources claim it was scrapped in 1941, while others claim it was destroyed by a Japanese bomb in 1942.


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## Marcel (Sep 22, 2008)

After the KNIL declined the fighter, the dutch minister of colonies Colijn offered the D.XXI to the minister of defence Colijn (Colijn held both posts at the same time  )
The Dutch LVA (Luchtvaart Afdeling, Aviation Departement) was in terrible shape. The best fighter at the time was the Fokker D.XVII biplane, the LVA had 9 of them. After testing the D.XXI, the LVA accepted it, as it was a leap forward. Some requests by the Finnish air force would also be implemented in the Dutch version, the smoother skin, the engine (Mercury VII instead of VI), the instrument panel and the air reservoir for the MG’s. The chair would be taken from the Danish version. Armament would consist of 4 FN 7.9 mm MG’s, in each wing 2 of them. Each MG would have 300 rounds. The LVA ordered 36 of the type.

The LVA knew very well that their new fighter was inherently obsolete and the speed would not be sufficient to catch a modern bomber in level flight. The intention was to use the D.XXI with the tactical 2nd regiment, linked to the field army. Another type should take the role as a fast interceptor, for this role were considered a.o. the Hurricane, He112 and the Spitfire. In the end, the Curtiss CW21B Interceptor and the Koolhoven FK-58 were ordered. In the mean time, the D.XXI would fulfil the role of interceptor. As the delivery of the other two were not in time, the D.XXI was still the main interceptor on may 10th, 1944.


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## Marcel (Sep 22, 2008)

A nice story about the pilot's seat:
Nowadays, a lot of calculations would be used to calculate the best way of adjusting the seat. The '30ies were different times. The LVA simply sent their shortest and longest fighter pilot to Fokker, being lt. Boogaard and lt. Doppenberg. When sitting exactly in the line of sight for the gunsight, lt. Boogaard (shortest) found out that he hit the canopy and the seat was not even at it's highest position. Lt. Doppenberg already hit the canpoy in the lowest setting and was even too high for looking trough the gunsight. The rapport dryly comments that the seat adjustment obviously had to be altered.


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## Marcel (Sep 23, 2008)

Many claim that the D.XXI could not be fitted with an in-line engine as the airframe was not designed for it. As we already saw, this is wrong as the a/c was initially designed for the RR Kestrel engine, which is an in-line. Further more, Fokker made a design with a DB601 engine, designated D.XXIV. Unfortunately it didn't get any further than designing stage.


Many sources claim that the D.XXI carried 2 MG's in the nose and 2 in the wing. This is wrong. Please look at the picture below. You can clearly see 2 MG's protruding from the leading edge of each wings. In fact all MG's were installed in the wings, with a convergence at 200 meter. The MG's were Belgian FN M.38 7.9 mm with 300 rounds each.


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## Marcel (Sep 23, 2008)

After the order was placed on December 29th 1937, Fokker started to build the first production a/c. This plane, the 212 was ready on May 26th 1938. The performance showed to be satisfactory. On July 22th, 1938, the a/c was pre-tested. It was standard procedure to redo the tests by 2 LVA (now called ML) pilots. 
The delivery dates of the a/c were:
212, 07/22/1938
213, 08/12/1938
214, 08/12/1938
215, 08/26/1938
216: 08/26/1938
217: 09/9/1938
218: 09/9/1938
219: 09/16/1938
220: 09/28/1938
221: 09/30/1938
222: 10/03/1938
223: 10/12/1938
224: 10/12/1938
225: 10/11/1938
226: 10/11/1938
227: 11/23/1938
228: 11/12/1938
229: 11/12/1938
230: 01/12/1939
231: 01/17/1939
232: 01/12/1939
233: 01/26/1939
234: 01/17/1939
235: 02/18/1939
236: 02/18/1939
237: 02/18/1939
238: 02/18/1939
239: 03/14/1939
240: 03/14/1939
241: 03/14/1939
242: 03/23/1939
243: 03/23/1939
244: 04/05/1939
245: 04/05/1939
246: 04/11/1939
247: 03/01/1939


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## Marcel (Sep 23, 2008)

On August 26 Fokker announced that cracks occurred in the bottom of the fuel tanks. These tanks had to be strengthened. This modification was introduced as a standard in later deliveries
Wheels of the landing gear were rotating during flight because of which, the landinggear strongly vibrated. Fokker tried to solve this by putting rubber pieces in the wheel-cover. A solution was found by making it a standard procedure to put the break on during flight 

Pneumatic loading (Dewandre mechanism) of the the MG’s failed during flight. After installing 2 extra valves, the problem was solved in November 1938. 

Antenna’s were faulty. 226 was the first to be delivered with a new copper antenna.

The attachment of the wheels to the legs were prone to corrosion. They had to be replaced often.

The MG covers were often lost by D.XXI. It was solved by: 1. strengthen the closing-mechanism 2. Holes in the cover 3. two extra bold in the attachment of the covers

Fuel tanks still cracked in 1939, so all D.XXI’s were grounded. All fuel tanks had to be replaced by aluminium tanks, which was ready on July 4th 1939.


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## Marcel (Sep 23, 2008)

1. D.XXI from 1st JaVA, see the white mice logo
2. Logo from 1st JaVA, white mice and "shoes with pointy tips"
3. D.XXI's on Ypenburg (The Hague), note the Fokker G.I in the back
4. D.XXI with 1st camouflage pattern (212-229)
5. D.XXI with 2nd camouflage pattern (230-247)


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## Marcel (Sep 25, 2008)

1e luchtvaart regiment

1-II-1 LvR (1e JaVA)
At first, the LVA didn't have any operational units. There was only 1 fighter squadron, called JaVA (Jacht Vliegtuig Afdeling= Fighter department), based on Schiphol airport. This group was renamed 1-II-1 Lvr (1st JaVA) after the reorganisation in 1939. It was the first unit to be equiped with the D.XXI and flew with a mixture of D.XXI, D.XVII and D.XVI until April 1939, after which it flew exclusively with D.XXI's. The strength varied from 6 to 9 D.XXI's, 7 being operational in May 1940.
This unit was most active during the mobilisation (9/1/1939 - 5/10/1940). It operated from several airbases across the country during that time. The time spend at Groningen Airport Eelde is most noteworthy as the unit had contact with invading German a/c several times.
09/13/1939: Capture of Do18 M2+LK (2./106) at the island of Ameland.
10/17/1939: Being shot at by German Flak while flying over Dutch waters, not far from Emden
11/19/1939: Interception of intruding He111 H-2 7A+CH (1./121) over Schiermonnikoog. One D.XXI damaged. The damaged He111 had to land on Borkum, with one injured crewmember.
12/06/1939: Interception intruding Do17.
05/04/1939: Interception and damaging an unknown Ju88.
Was retreated to De Kooij airfield as the airfields in the east were to vulnerable to German attacks.

2-II-1 LvR (2e JaVA)
Created in 1939, first equipped with D.XVI and D.XVII's, later only with D.XXI. Strength varied from 8 to 11 D.XXI's. Had many interception missions, but never exchanged fire.

3-II-1 LvR (3e JaVA)
Created in 1939. First equipped with 6 D.XXI's. In September 1939 re-equipped with G.1's. D.XXI's were divided among other JaVA's. While flying G.1's, this unit was responsible for shooting down RAF Whitley N-1357 (no77 Squadron) on 03/28/1940.

Jachtgroep Veldleger
1-V-2 LvR 
Created November 1939. The "Jachtgroep Veldleger" was a tactical group, for supporting the field army. Apart from this, the group was also involved in interceptions, mainly Allied ones as the group was based on Ypenburg near the Hague.

Several single D.XXI's have over time been assigned to different units like training units. For instance 4-II-1 LvR, equiped with G.1 had 1 D.XXI on strength, possibly as an example for mock-up planes.


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## Juha (Sep 25, 2008)

Marcel
Thanks alot. Very interesting. Even if I have a basic knowledge of development of D.XXI, I wonder why , and its use by Dutch AF in 39-40 those messages on deliveries and technical problems were very interesting and the info was new to me.

Juha


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## Marcel (Sep 25, 2008)

1 1e JaVA on De Kooij
2 and 3. The next best thing, wreckage of D.XXI no 229 flown by sgt De Roos. This is a legendary fighter because of it's story (http://www.ww2aircraft.net/forum/stories/remarkable-kill-11738.html)
I made these photo's last week when I visited the Crash '39-'40 foudation. It's the only remains of the Dutch D.XXI's. It was found in 1994. The museum excavates a lot of crash sites and has stuff on display. Maybe I'll make a new thread about this visit when I've collected all the photo's.


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## Marcel (Sep 25, 2008)

Juha said:


> Marcel
> Thanks alot. Very interesting. Even if I have a basic knowledge of development of D.XXI, I wonder why , and its use by Dutch AF in 39-40 those messages on deliveries and technical problems were very interesting and the info was new to me.
> 
> Juha



Thanks Juha. I'm actually putting it together for my own overview. There are many small sources of info and I'm trying to put them together in one picture. 
Oh and I found the climb speed as we discussed in another thread. The only number I could find was measured during acceptance trials, being 6m 12 s to 5000 metres. Quite good but not exceptional as you said.


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## Marcel (Sep 26, 2008)

The construction of the D.XXI was typical of all Fokker planes at the time. Fokker had made name and fame with monoplane airliners in the ‘20’ies. They were build of steel tubes and fabric with wooden wings. Allmost all pre-war Fokkers were of that construction. The D.XXI was no different. The rear fuselage was build of steel tubes, with a fabric cover. The wings were made of wood and the front part of the fuselage with the engine-mounting was made of metal, mainly aluminum. The moving parts like the ailerons and ruders were fabric covered as well. The whole construction was not entirely unlike the British Hurricane.
Although the whole construction seems to be obsolete compared to the contemporary monocoque build Bf109 and Spitfire, this way of constructing an airplane had it’s advantage. It was relatively easy to repair, which proved to be important while fighting the overpowering numbers of the German airforce. Almost each sortie resulted in heavy damage to the planes, but quite often they were operational again after a short time. 

See below the construction of the D.XXI and T.V’s in the Fokker Factory
Seccond, wing spar of a Fokker T.V as I photographed it at the Crash museum.


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## Marcel (Sep 26, 2008)

One moving picture of 1e JaVA Fokker D.XXI's taking off from De Kooij. Don't mind the text in the movie. The take off was probably before May 1940.


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## Glider (Sep 26, 2008)

As has been mentioned the inability of the DXXI to be fitted with an in line engine is of course wrong. 
At the May 1936 Internationella Luftfartsutstallningen held in Stockholm the Fokker Sales team offered the DXXI with either fixed or retractable undercarridge, and with the 1,100HP Hispano Suiza 14Ha radial, 830HP Mercury or the 925HP Hispano Suiza liquid cooled engine.

One question I have is the Dutch had at least one fitted with 2 x 20mm Madsen guns and 2 x LMG. What I don't know is what impact that had on its performance, does anyone have the information?

Re the layout of the 4 x LMG these were in the wings but originally the Finish AF specified that there aircraft, should be fitted with 2 in the wings and 2 in the fuselage. They were not built that way but it might be the cause of the confusion.


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## kool kitty89 (Sep 27, 2008)

Fokker D.XXIs to Finland

The Finns also tried them with 20 mm cannon, but Oerlikon cannon. 







> FR-76 had two 20 mm Oerlikon cannons, but experiences in the Winter War were negative and the aircraft was re-equipped with machine guns.



In the picture it apears to be an Oerlikon FF-L.


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## Juha (Sep 27, 2008)

Hello Marcel

FAF D.XXI climb was 6min 23 sec to 5,000m but the empty weight of Finnish built D.XXIs was a bit higher because use of Finnish pine instead of American spruce in construction.

Quote:” Many sources claim that the D.XXI carried 2 MG's in the nose and 2 in the wing. This is wrong. Please look at the picture below. You can clearly see 2 MG's protruding from the leading edge of each wings. In fact all MG's were installed in the wings”

Maybe reason is that Mercury engine D.XXIs of FAF had 2 MG's in the nose and 2 in the wing. Finnish sources mentioned that Dutch D.XXIs had all 4 mgs in wings.

According to Finnish tests in Holland 27.8 – 2.9.37 with cannon installation without cannon but with 103 kg weight installed the only difference to 4 mg a/c was that control was a bit heavier. 

Tests in Finland in Dec. 37, cannon armament weighted 116,2 kg altogether incl. ammo, 2 wing mgs armament 60,4 kg.

It had effect in climbing turn etc.

But surprisingly no effect on climb to 6,000m, 7.93 min for both mg and cannon D.XXI. Cannon D.XXI was 1-1½ kmh slower in different altitudes. But Finns concluded that Oerlikon FF was unsuitable in fighter combat so only the test plane ever had cannon armament.

the only cannon armament D.XXI, FR-76, got 3 2/3 victories before cannon were removed after 20 Jan 40. 

Juha


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## Marcel (Sep 27, 2008)

Glider said:


> One question I have is the Dutch had at least one fitted with 2 x 20mm Madsen guns and 2 x LMG. What I don't know is what impact that had on its performance, does anyone have the information?



According to my sources, no Dutch D.XXI was ever fitted with canons. All a/c had 4 LMG's. As Juha mentions, Finnland tried 20mm canons on the D.XXI and I believe the Danish AF did, too.


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## Marcel (Sep 27, 2008)

Juha said:


> Quote:” Many sources claim that the D.XXI carried 2 MG's in the nose and 2 in the wing. This is wrong. Please look at the picture below. You can clearly see 2 MG's protruding from the leading edge of each wings. In fact all MG's were installed in the wings”
> 
> Maybe reason is that Mercury engine D.XXIs of FAF had 2 MG's in the nose and 2 in the wing. Finnish sources mentioned that Dutch D.XXIs had all 4 mgs in wings.


Thanks Juha, there's much confusion about the installation of MG's on the D.XXI. Some sources claim that all FAF D.XXI's had MG's in the wings, which is clearly wrong as you show. Others claim that Danish AF D.XXI's had 2 Madson canons beneath each wing, which I believe is also incorrect as it was used on only 1 example AFAIK. 













Why did the FAF install 2 MG's in the fuselage? And do you have pictures of the forward fuselage/cowlings with the MG's? I'm curious to the installation.


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## Juha (Sep 27, 2008)

Hello Marcel
all FAF Mercury engine D.XXIs had 2 fuselage plus 2 wing mgs, also those 7 built by Fokker, others were built under licence here in Finland. But all Wasp powered FAF D.XXIs had 4 wing mgs only, because Wasp was two row radial.

It is also my understanding that only one Danish D.XXI had cannon armament.

Why 2 fuselage mgs, I don't know but my guess is that the reason was FAF's intrest for max concentration of hits.

Juha


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## Juha (Sep 27, 2008)

And the photo on Mercury powered D.XXI, You can see the 2 flash tubes of fuselage mgs, the right one was partly hidden by the NACA ring.

Juha


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## Marcel (Sep 27, 2008)

Great pic Juha, thanks. The flash tubes are the grey tubes between the cylinders?


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## Juha (Sep 27, 2008)

Hello Marcel
Yes, That's my understanding.

Juha


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## Airframes (Sep 27, 2008)

Marcel (and Juha), thank you for a very informative insight into the FokkerXXI.
It's an aircraft that I knew little about but, ever since I built an original 'Frog' model of one when I was a child, it has held my interest. There is just 'something' about it that looks right; and I wonder what it could have been like if developed (Retractable undercarriage, in-line engine etc.)?


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## Marcel (Sep 27, 2008)

Airframes said:


> Marcel (and Juha), thank you for a very informative insight into the FokkerXXI.
> It's an aircraft that I knew little about but, ever since I built an original 'Frog' model of one when I was a child, it has held my interest. There is just 'something' about it that looks right; and I wonder what it could have been like if developed (Retractable undercarriage, in-line engine etc.)?



My pleasure Airframes and I'm not finished jet. About your question,I believe it would have been comparable to the British Hawker Hurricane, if the armament would have been upgraded as well. But maybe it would have brought some disadvantages as well. I believe the strength of this aircraft was it's simple construction, easy to repair and it's ability of flying from small airfields. This was a main advantage of the a/c in the 5 days war, as 4 of the 5 days were kinda like a guerilla airwar, with hidden airfields and quick hit-and-run attacks.


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## HoHun (Sep 27, 2008)

Hi Marcel,

>This thread is meant to cover the story of the D.XXI, while focussed on the service in The Netherlands. (I will probably bore the hell out of you 

Actually, I find it quite interesting!  I'd like to try to analyse D.XXI performance and have been looking for numbers, but so far, I haven't found the "full set" of figures I'd need.

Perhaps you have some information on:

Weight in fighter configuration
Top speed at full throttle height (with top-speed full throttle height)
Engine power at sea level and full throttle height (with full throttle height under static conditions) - I assume the powerplant is a single-speed, single stage engine?
Wing span, wing area
Exhaust system: Collector ring with no backward exhaust, collector with backward exhaust, single ejector stubs?
Propeller: Fixed pitch or variable pitch/constant speed?
Clmax of the wing, or the designation of the wing section that was used

That would allow a fairly good comparison to contemporary types, such as the Me 109D that the Fokker might have met in combat.

Regards,

Henning (HoHun)


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## Marcel (Sep 27, 2008)

Hi Hohun,

What I know:
Weight: Empty: 1450 kg, full load: 2050kg
Top speed: 460 km/h at 5100 m (at 2750 rpm engine), with full miliary load: 415 km/h.
Propellor: Ratier 2 speed propellor
Engine: Bristol Mercury VIII, Power at start, 2650 rpm: 705-735 hp, full trottle at 4270m: 850 hp, climbing at 2650 rpm at 3965m: 805-835 
Single speed etc.: no idea you should ask the real engine buffs 
Wingspan: 11.00m
Wing area: 16.2m^2
Clmax, sorry don't know.


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## Juha (Sep 27, 2008)

Hello HoHun
Exhaust system: Collector ring with backward exhaust
the designation of the wing section that was used: Clark YH, at root 20%, at tip 9% thick.

Juha


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## kool kitty89 (Sep 27, 2008)

Juha, what's your sourse for the performance figures?

They do seem to match those here: Fokker D.XXIs to Finland
(which makes sense as these should be from Finnish records)

The speed does seem a bit lower than the Dutch figures (with Mercury VIII) but maybe the Mercury VII was less powerful. 
Or the comparisons are in different loading conditions or at different engine power -the 460 km/h figure being at take-off/emergency power. 
(as the top speed with the Mercury in the Finnish figures seems to match the Dutch figures at "full combat weight" at 414 km/h)


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## kool kitty89 (Sep 27, 2008)

Also, has anyone else heard of this:


From http://www.ww2aircraft.net/forum/ai...r-d-xxi-retractable-under-carriage-13219.html


Mangrove said:


> On the other hand all Finnish Fokkers were modified to have wing slots as in 109. The speed loss was like 0-5 km/h
> but the new wing was more agile and had better landing characteristics.
> 
> Martti


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## Juha (Sep 28, 2008)

Hello KK
sources: Kalevi Keskinen, Kari Stenman and Klaus Niska: Suomen Ilmavoimien Historia 3 Fokker D.XXI
Timo Heinonen:Thulinista Hornetiin (1992)
and for cannon-Fokker Pentti Manninen: FR-76 "Tykki-Fokkeri" in Suomen Ilmailuhistoriallinen Lehti 3/1995
and for general info and for details Jukka Raunio: Lentäjän näkökulma II (1993)


Now from Aug 1941 onwards slots were built in wings of D.XXIs, both to the new ones and to old ones when they went to factory for repairs. So slots like in SBD (IIRC) and not slats as in Bf 109 and in Yaks, LaGGs and Las.

Juha


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## kool kitty89 (Sep 28, 2008)

Thanks for the info. The addition of the slots should have cured thoes tip-stalling problems you mentioned a while back. 

Slats is the correct term for the automatic devices, but in this timeframe they were often referred to as "automatic slots." (in fact I believe this was the terminology used by Handley Page when they developed, patented, and maketed them)


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## HoHun (Sep 28, 2008)

Hi Marcel,

>What I know:

Thanks for the data!

>Top speed: 460 km/h at 5100 m (at 2750 rpm engine), with full miliary load: 415 km/h.

Hm, a bit too much of a difference between these two ... could it be "full military equipment" instead of "... load"? Then 460 km/h would be the "prototype speed". 5.1 km full throttle height is very much, too - it indicates 100% exploitation of the ram effect, which is not normally achieved in practice.

>Propellor: Ratier 2 speed propellor

I'll assume it's a constant speed propeller because this is all I can handle 

>Engine: Bristol Mercury VIII, Power at start, 2650 rpm: 705-735 hp, full trottle at 4270m: 850 hp, climbing at 2650 rpm at 3965m: 805-835

A bit confusing ... I take it the data for 4270 m is for 2750 rpm, so I'll use the lower full throttle height for 2650 rpm.

>Clmax, sorry don't know.

Based on Juha's suggestion of the profile, I'll arbitrarily assign a 1.35 clmax because it's in the ballpark.

I've got to re-run the figures later because of the difficulties with the data I pointed out above, but it sure looks like the Fokker D.XXI could both out-climb and out-turn the Me 109D easily, but it had a big speed disadvantage.

Regards,

Henning (HoHun)


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## Marcel (Sep 28, 2008)

HoHun said:


> Hi Marcel,
> 
> >What I know:
> 
> ...


Correct, I translated it wrongly, sorry for that



HoHun said:


> Then 460 km/h would be the "prototype speed". 5.1 km full throttle height is very much, too - it indicates 100% exploitation of the ram effect, which is not normally achieved in practice.
> 
> 
> >Propellor: Ratier 2 speed propellor
> ...


I got these figures from the Pilot's manual for the Mercury, see below.



HoHun said:


> >Clmax, sorry don't know.
> 
> Based on Juha's suggestion of the profile, I'll arbitrarily assign a 1.35 clmax because it's in the ballpark.
> 
> ...


That would fit with the comments of the pilots.


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## HoHun (Sep 28, 2008)

Hi Marcel,

>I got these figures from the Pilot's manual for the Mercury, see below.

Ah, thanks - that clears it up a bit. Interesting that 4270 m (14000 ft) is considered full throttle height at top speed, while the Wikipedia article quotes it as if it were static full throttle height, but I'll go with the manual on this.

Bristol Mercury - Wikipedia, the free encyclopedia

Is my propeller diameter of 2.84 m correct? I'm also using a reduction gear ratio of 0.572:1.

I have assigned a ram efficiency factor of 0.5 and selected a static full throttle height to achieve that at my calculated best climb speed at the altitude indicated in the manual.

Below the first results ...

Regards,

Henning (HoHun)


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## Marcel (Sep 28, 2008)

An example of an incident during the neutrality period, the incident with the Fokker T.VIIIw (R-5).
On Wednesday, 09/13/1939, Fokker VIIIw (R-5) of the Royal Dutch Navy was on patrol a few miles north of Ameland, when the crew spotted a plane. After following it for a while, the R-5 came closer in order to identify the nationality and the type of the unknown plane. It was the He115 M2+LH (1./106) on a reconnaissance flight over the North sea. As soon as the crew of R-5 identified it, they turned away to fly back to Ameland. The German crew however mistook the Dutch roundel for English markings and opened fire. The R-5, damaged badly, made a crash landing on the heavy sea. The He115 landed beside the crashed aircraft to rescue the crew. Then they found out their mistake. The He115 however was damaged by the heavy sea and was unable to take off. Do18 M2+LK (2./106) came for the rescue. But again, the landing went wrong and the Do18 fuselage started leaking, after which, it started floating towards the coast. In the meantime, the He115 was able to take off again and head for Germany.

3 D.XXI's from 1e JaVA (1-II-1 LvR) at Eelde airport arrived at the scene and saw the Do18 trying to get to international waters again. The leading D.XXI gave a warning shot in front of the bow and the DO18 turned back to the coast. When the D.XXI left, the Do18 turned back to the north, after which the D.XXI's attacked again, wounding 1 german crewmember. The Do18 gave up and floated to the beach of Ameland. In the following hours the D.XXI fighters had to deter several German planes trying to violate the Dutch airspace to rescue the Do18.

The incident caused the Dutch to change from the roundel markings on their aircraft to the orange triangles.
Parts of the Do18 were still found on the beach in 1984.

Pics:
1. Do18 on the beach
2. T.VIIIw (R-5) with Dutch roundel
3. Fokker D.XXI with orange triangle


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## Marcel (Sep 28, 2008)

HoHun said:


> Is my propeller diameter of 2.84 m correct? I'm also using a reduction gear ratio of 0.572:1.
> 
> I have assigned a ram efficiency factor of 0.5 and selected a static full throttle height to achieve that at my calculated best climb speed at the altitude indicated in the manual.
> 
> ...



Hi Henning,

Thanks , interesting data . The reduction gear ratio is correct. For the propellor I have a diameter of 3.28 m, but I don't know if that's correct.
Am I right that the second graph is climbspeed?
And a request, could you include the Bf109E and/or Bf110C as well? The D.XXI had a number of encounters with the types.


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## marshall (Sep 28, 2008)

Thanks guys, great thread.


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## HoHun (Sep 28, 2008)

Hi Marcel,

>And a request, could you include the Bf109E and/or Bf110C as well? The D.XXI had a number of encounters with the types.

Here is the data for the Me 109E. (Note that I'm experimenting with different high-altitude power estimating methods for better comparability with the sketchy data on the Mercury - absolute figures at high altitude might not be exact as a result). 

I have recalculated the D.XXI in the new set for the larger propeller diameter you quoted.

Regards,

Henning (HoHun)


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## Marcel (Sep 29, 2008)

HoHun said:


> Hi Marcel,
> 
> Here is the data for the Me 109E. (Note that I'm experimenting with different high-altitude power estimating methods for better comparability with the sketchy data on the Mercury - absolute figures at high altitude might not be exact as a result).
> 
> ...



No problem, most of the fighting was at the lower altitudes anyway.

Great info, thanks, seems to confirm the reports of Dutch pilots that they usually could outturn the Bf109. The speed disadvantage is of course obvious.


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## Juha (Sep 29, 2008)

Hello
I dig a bit deeper into FAF D.XXI speed and climb.
A couple figures based on test flights, both took off weighting 1970 kg. Both datasets are took from graphs published in secondary sources, espesially that of FR-96 was a bit difficult, background being purely white and graphs being rather small.

First FR-107, which was one of maybe only 4 which got Mercury VIII during the war and test was flown when it was powered by Mercury VIII.

Climb to 5000 m 6'08", to 6000 m 7'53"
Max speed 352kmh at SL and 413kmh at 5000m.

FR-96, engine Mercury VII, max power 810-840 hp at 4420 m 2750rpm. Take off power at SL 728 hp at 2750rpm. On ground adjustable Ratier airscrew 3.0m diameter, reduction gear 0.666

Climb to 5000 m 7'12", to 6000 m 9'36"
Max speed 353kmh at SL and 416kmh at 4750m

Sources: Lentäjän näkökulma II
Ilmailu Joulukuu 1989
Suomen Ilmailuhistoriallinen Lehti 4/2000

First 2 for FR-96 and the latter for FR-107.

Juha


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## Marcel (Sep 29, 2008)

1. Reduction Gear on the 229 wreckage
2. Part of wooden wing on the wreck
3. 227 with in-between markings.
4. 1-V-2 LvR on Ypenburg shortly before the war (note the G.1 in the back)


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## Marcel (Sep 29, 2008)

During the first days of May 1940, several alarms were given. It became more clear that German was planning to attack The Netherlands. Therefore order 22B was issued on May 8th, which meant that every day between 03.15h and 8.00h, all a/c of the JaVA’s and BomVA’s should be ready to take off immediately. The other a/c should be spread outside the airfields in order to minimize damage during an eventual attack.
In the early morning of May 10th 1940, at around 01.20h, the time to be ready was changed to 03.00h. The JaVA were thus all ready when the German attack started.
The locations of the D.XXI fighters were:
1-II-1 LvR (1e JaVA) on De Kooij airfield (11 D.XXI’s on readiness):
214
218
219
221
223
233
234
240
241
242
244

1-II-2 LvR (2e JaVA) (9 D.XXI on readiness):
213
224
225
229
235
236
238
239
245 

1-V-2 LvR (8 D.XXI on readiness):
212
215
216
217
222
228
246
247

Not on readiness: 
1-II-2 LvR (2e JaVA): 230, 232, 243 (all maintenance)
1-V-2 LvR: 227 (able to fly, but not “battle ready”)
Flightschool, Texel: 226, 231
Fokker factory: 220 on repair, 90% completed
237 crashed on 11/22/1939 in thick mist near Hillegersberg, killing the pilot, and was scrapped


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## HoHun (Sep 29, 2008)

Hi Juha,

Thanks for the additonal data!

>First FR-107, which was one of maybe only 4 which got Mercury VIII during the war and test was flown when it was powered by Mercury VIII.

>Climb to 5000 m 6'08", to 6000 m 7'53"
>Max speed 352kmh at SL and 413kmh at 5000m.

I calculate to 5000 m in 6:17 min at 1970 kg, and to 6000 in 8:16. Good start 

Is it clear from the graph if 5 km is the full throttle height? That figure does not match our previous assumptions ... maybe we're going to have to revise something.

Regards,

Henning (HoHun)


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## kool kitty89 (Sep 29, 2008)

What seems odd to me is that the top spped of the D.XXI is about the same as that of the Gloster Gladiator, with an equevelent engine, ~250 kg greater take-off weight and being a biplane with almost 2x the wing area and a similar armament.

Inless the official operational performance figures for the Gladiator are significantly less than the commonly refrenced 414 km/h. (the Finnish wikipedia page gives 400 km/h at 4,200 m for the Gladiator Mk.II)


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## HoHun (Sep 29, 2008)

Hi Koolkitty,

>What seems odd to me is that the top spped of the D.XXI is about the same as that of the Closter Gladiator, with an equevelent engine, ~250 kg greater take-off weight and being a biplane with almost 2x the wing area and a similar armament.

Good point! For comparison, I believe the Ar 68E was about 100 km/h slower than the Me 109 with a roughly equivalent engine ...

Regards,

Henning (HoHun)


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## kool kitty89 (Sep 30, 2008)

Juha, wat are your figures for the Gladiator's performance?


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## delcyros (Sep 30, 2008)

Very impressive collection of informations to an barely well discussed topic. Wonderful as always, Marcel!


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## Juha (Sep 30, 2008)

Hello HoHun
the speed graph is very ”flat” along x ie speed axis and it is difficult to say for sure the exact altitude of max speed but it is appr 5 500 m.
From Gladiator info the max power, for 5 min, for Mercury VIIIA 810-840 hp at 4270 m (14 000ft), so the altitude is same as that Marcel gave.

KK
Finns were not very interested to test Gladiator Mk. II thoroughly, but for a new plane
330 kmh at SL and 400 kmh at circa 4500m.

Source for Gladiator Lentäjän näkökulma

Juha


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## kool kitty89 (Oct 2, 2008)

I just realized you listed the Mk.II specifically. Was the Mk.I Gladiator tested more thoroughly?


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## Juha (Oct 2, 2008)

Hello KK
FAF had only Mk. IIs, which arrived in Jan-Feb 40, in the middle of the Winter War. They were given to LLv 26 as soon as possible because the designed a/c of the LLv 26, Fiat G.50s, were delayed badly because Germany's refusal of transit. Gladiator was not interesting a/c for FAF as an example of a/c design, so it wasn't thoroughly tested after the Winter War.

The air unit of Swedish volunteers during the Winter War, F 19, had some 6 - 9 Gladiator Mk Is but they were even less interesting a/c to FAF in testing sense.

Juha


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## Marcel (Oct 2, 2008)

Meanwhile, continuing the thread, we’ve arrived at the night of 9 to 10 May 1940.

To give you an insight in the situation at the start of the hostilities: 

On May 9th 1940, the German Luftwaffe was fully prepared for the assault on the west, which could not be recalled after 19.10h. The total force of a/c unleashed against the Dutch consisted of:
430 transport a/c
389 fighters
261 bombers
52 mine laying a/c
94 reconnaissance a/c
6 light a/c

A total of about 1200 planes. (I have a list of units, but found it too long to type for this thread)

Against this, the Dutch could put the already mentioned 29 active D.XXI’s, 23 G.1’s, 9 T.V bombers, 11 Douglas 8A 3N attack planes, 7 D.XVII’s (fighter), 61 C.V’s (rec), 15 C.X (rec/bomb) and 16 FK51’s, a total of 171 a/c of which 99 were obsolete bi-planes.

At 20.30h May 9th 1940, Dutch AA gunners spotted a reconnaissance a/c over Dordrecht. This is confirmed by British radar logs. At 23.30h, Ruigenhoek airfield reported many a/c flying west. After this many reports of a massive neutrality violation of a/c flying west came from all over the country. At 02.00h, Schiphol airport went into the highest alert phase. At 03.00h all Dutch fighters were on readiness. 
At 03.30h German Mine laying a/c started to drop the first mines in Dutch waters. A Dutch warship, the Johan Maurits shot one down, the first of German a/c to be shot down over The Netherlands. 
Meanwhile the German main bomberforce turned over the Northsea, to fly east again, to the Dutch coast. At 3.30h, German a/c attacked the airfield Waalhaven in Rotterdam. The real attack started at 03.45h.


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## Marcel (Oct 2, 2008)

Unit was ready at 03.00h. After hearing many a/c flying over, the commander, capt. Schmidt-Crans, asked his superiors for permission to send out a patrole. He didn’t get it. 
While talking to the command post on the phone, he heard another voice in the background talking about bombing. This was enough for him to give the order on his own and at 03.59h, the whole JaVA was airborn, in time to avoid being wiped out on the ground.
The JaVA was divided into 4 patrols of 2 to 3 D.XXI’s, patrolling the North part of Holland. 
No 244 (Wmr Hatebroek) attacked J88 5J+?T from 9./KG4, forcing it to land on the beach. (this Ju 88 was recaptured and repaired by the Germans after the capitulation). 234 landed on Schiphol and flew back to De Kooij, landing there at 07.00h.

Between 4.30h and 4.45h, no. 214, 221, 223, 233, 234, 240 and 242 landed and refuelled. The remaining 3 (218, 219 and 241) were just landing, when they were attacked by 9 Bf109E’s from 4./JG186. 241 (Lt. Bosch) was destroyed while landing. The pilot could get out safely. 219 (Lt. Overvest) could just pull up, while 218 (Lt. Focquin de Grave) could take off again. All flying D.XXI’s were called back to base and there was a dogfight between 8 D.XXI’s and 9 Bf109’s, lasting about 10 minutes. 3 Bf109E’s were shot down (by 234, Lt. Van der Stock; 221, Lt. Doppenberg; 219, Lt. Overvest) against none of the D.XXI’s, although all D.XXI’s were more-or-less damaged. One of the Bf109E’s (Hptm Robitzsch), shot down by 219 crash-landed on De Kooij, the pilot was taken prisoner and later shipped to the UK. Uffz. Rudolf (shot down by 221) died of his wounds after crashing near Anna Powlona and the 3rd Bf109 crashed in the sea, fate of the pilot unknown.

223 (Wmr Zuijlen) did not take part in the dogfight, not being warned because lack of radio. He attacked 2 Heinkels near Katwijk, and was probably killed in that fight. His D.XXI didn’t crash, but flew on for some time, right through some German formation, finally crashing near Wassenaar.

At 05.30h, 4 D.XXI were ready again.

06.15-07.10, Patrol 234 and 240
08.00, all D.XXI were damaged in an airraid 214 and 233 beyond repair
12.00h 4 D.XXI trying to start, 234 (Lt. van der Stock was shot on fire by raiding Bf109’s (Van Der Stock survived and got his fame when he was 1 of 3 pilots escaping from Stalag luft III in the great escape) 
Only 6 D.XXI’s were still in tact and at 19315h, 218 and 244 l;eft for the secret airfield Buiksloot.
221, 240 and 242 would do the same the next day, while 219 would leave on May 12th.

Photo's:
1. Bf109E-4 'Schwarze 1' (Hptm Robitszch) after crash-landing on De Kooij
2. Wreck of 223 (Wmr. van Zuijlen) near Wassenaar
3. Grave of Wmr Van Zuijlen 
4. Burning 234 (Lt. Van der Stock), picture taken by pilot imediately after the attack.
4. Wreck of 241 with Lt. Bosch in front of it


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## Marcel (Oct 3, 2008)

Lt. van der Stock describes the dogfight of 1e JaVA quite different. He claimes 12 D.XXI's fought 16 Bf109's. He also claims that his plane 234 was burned while landing, not while making ready to start. I thought his story was quite inaccurate (for instance, 1e JaVA never had more than 11 a/c), so I left it out.


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## Marcel (Oct 3, 2008)

2e JaVA took off from Schiphol airport between 03.45h and 04.00h, in the midst of a German attack. As the radiopost was damaged during the attack, no communication was possible and every pilot had to take care of himself.
229: Lt. Sluijter shot down Ju88 5J+GT (Oblt Rinck, 9./KG4) over Schiphol and later landed on the secret airfield Ruigenhoek at 04.15h. At Ruigenhoek, people were very surprised as they were not aware that the war had started.
236: Sgt De Geus, damaged an unknown Ju88. Landed at Ruigenhoek at 04.30h with empty MG’s.
225: Sgt Looijen landed on Ruigenhoek.
245 Sgt Bulten, landed at Schiphol while being wounded.
213(Sgt Burger), 224 (Lt Sitterd), 238 (Lt. Bodaan), 239 (Sgt Roos) and 235 (Lt Plesman) landed at Schiphol between 04.18h and 04.45h.
213 and 239 were sent to Ruigenhoek where they joined the 3 D.XXI’s which were already present. They formed a patrol, flying to Gouda where a Ju52 was shot down. Lt Sluijter was wounded in that action. Two other Ju52’s were forced to land. Sgt. Looijen (225) was shot down and killed by Bf109E (7./JG 3) (Uffz. Massman) near Oudekerk a/d IJssel. While going back, some German a/c on the beach were raided.
A KLM pilot, Res. Sgt Steensma, reported for duty and was assigned to fly the 239. (Story). At 12.00h, 238, 213, 235, 224, 236 and 239 escorted 3 T.V’s to attack Waalhaven (in German hands). Lt. Bodaan (238 ) was shot down and killed by Bf109E (Uffz. Springer, 7./JG 3). 236 shot down a Bf109E (III/Jg 3). 239 probably shot down another Bf109, but 239 was so heavily damaged at had to be abandoned after landing on Schiphol. Later in the afternoon, the remaining D.XXI’s were ordered to Buiksloot in order to reform a new JaVA together with the remainders of 1-II-1 LvR (1e JaVA).


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## Juha (Oct 3, 2008)

Thanks Marcel!
Very interesting!

KK
One point to D.XXI vs Gladiator, FR-167, the Wasp powered D.XXI with retractile undercarriage, was 15-37 kmh faster than normal Wasp powered D.XXI depending altitude.

Juha


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## Marcel (Oct 4, 2008)

The unit was ready at 03.00h. When the observation post at Delft reports approaching bombers at 04.00h, the D.XXI’s take off. They are aided by the fact that there’s no wind, so they could take off from standing position in any direction.
1-V-2 LvR is divided into 3 sections:
1. Lt. P.J.B. Ruijs de Peres (222), Sgt. G.K.P.Kiel (216), Sgt. J.Eden (247)
2. Lt. G.Steen (246), Lt. A.M.van de Vaart (212), Sgt. J.Linzel (215)
3. Lt. F.G.B.Droste (228 ), Sgt. P.J.Aarts (217)

The D.XXI’s immediately got themselves into a fight with Bf110’s.
222 (Ruijs de Peres) MG’s were jammed, thus could not participate. Ruijs de Peres however stayed in the air until being wounded and having to make an emergency landing near monster. 
216 together with 247 attacked a formation of Ju52 (with Falschirm jaeger) and shot one down. Later landed on Ruigenhoek. There, he re-armed and refuelled. After taking off, the D.XXI was attacked by 5 Bf110, after which it crashed, uside down near Den Deijl, in the midst of German paratroopers. After playing dead for a considerable time, sgt. Kiel could reach Dutch units and was brought to a hospital, wounded.
247 Shot down a Bf110 and landed at Ypenburg again at 05.00h. While landing, 247 was shot to fire. Sgt. Eden jumped out and tried the 227 which was not battle ready. 227 was shot to pieces as well before it could take off and Eden joined the ground fight against German paratroopers at the airfield.
246 had jammed MG’s as well, landed together with 215 (Sgt. Linzel) and changed pilots. (story) Groundcrew only had to put the airpressure on for the MG’s to function. Linzel with 246 shot down a Bf110 (Schroder? 6.ZG1) (maybe only damaged), but was wounded a little later and had to bail out. Pilot wouded and brought to the hospital.
215 After changing places with Sgt. Linzel, Lt Steen fought with several German a/c after which he crash-landed on the beach. 215 was set on fire by German planes by a Dutch torpedo boat.
212 Shot down a Do17 near Amsterdam. Then made an emergency landing at Schiphol, without engine power.
228 Shot down an unknown Ju88, landed at Ockenburg around 05.00h.
217 Shot down an unknown Bf110, landed at Ockenburg around 05.00h.

212 was re-assigned to the combined JaVA at Buiksloot.

1-V-2 was virtually non-existent after 05.00h. Lt Steen, Lt Droste and Sgt Ottes (227) were re-assigned to Schiphol, to fly G.1’s.
Ypenburg was captured by German Fallschirm Jaeger. Later it was re-captured by Dutch troops, but was not usable. The same happened to Ockenburg. 217 and 228 could not fly from there again and were captured in tack by German troops after the capitulation, May 14th.

1. 288 at Ockenburg
2. 215 on the beach.


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## Marcel (Oct 4, 2008)

Many sources claim:


> These aircraft's most important victory took place at dawn on May 10, 1940. . . . . . they succeeded in shooting down 38 . . . . Ju 52's out of a group of 55 that was crossing the Dutch border.


This has been quoted on this forum on a number of occasions as well. As we saw, there's no record of this battle, thus is untrue. Where this rumour comes from is unclear to me.


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## Marcel (Oct 5, 2008)

For a better picture, here a map with the locations of all mentioned airfields:


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## Marcel (Oct 5, 2008)

In the evening of May 10th, the Dutch structure of 3 D.XXI units was abandoned and a new combined JaVA was formed on the secret airfield Buiksloot, a former glider field. 
At first it had only 8 D.XXI’s on strength: 212, 213, 218, 224, 225, 235, 236 en 244. In the morning om May 11th, 3 more a/c arrived from De Kooij: 221, 240 an 242. In the morning of May 11th, personel from 1-II-1 LvR arrived and the commander of that unit now commanded the combined JaVA. In the evening, the unit was strengthened with 4 D.XVII’s from the flightschool at Texel. Why the there present D.XXI’s, 226 and 231, were not used is unknown to me.
Missions:
06.45h , 218 and 224 escorted C.V 592 to the Arnhem region. 592 had to turn back at Rhenen because of engine trouble. The aircraft returned at 07.44h

10.10h 212, 235 and 240 escorted the C.V’s 619 and 645 to Arnhem and back, landing at 10.45

13.09h, 213, 229 and 242 escorted 2 T.V’s (850 and 856) in an attack on the bridges in Rotterdam. 850 was shot down after the bombing. The formation was attacked by 12 Bf110’s. 213 (Foquin de Grave) was attacked by 6 Bf110’s, shot down 1 of them and probably damaged another after which he was wounded and made an emergency landing. The a/c was later set on fire by Dutch soldiers.
229 was attacked by 3 Bf110’s. Sgt. Roos eliminated one by jettisoning his canopy, which struck the Bf110 in the propeller. He then shot down another one, after which he was thrown out of his fighter. 229’s wreck is on display at the Crash ’39-’40 museum. (Story)
242 and 856 made it safely back to base.

15.55h Patrol by 235 (Van der Stock) and 240 (Bosch).


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## Marcel (Oct 8, 2008)

05.12h: 240, 218 and 244 escorted 2 C.V’s to Arnhem. They encountered heavy Flak. 244 damaged a German reconnaissance a/c. The patrol landed at 06.05h. 218 was lost during landing, the pilot, sgt Steensma was transported to the hospital. 

05.29: 221, 212 and 236 flew to Ruigenhoek. They arrived there without meeting resistance. They escorted 4 C.V’s to Delft, where they bombed German paratroopers.

219 which had remained on De Kooij flew to Buiksloot, landing there at 07.40h.

10.05h: 221, 219, 235, 240 and 244 flew to Ruigenhoek. 240 got engine problems there and could only return to Buiksloot, late in the afternoon.

16.16h 212, 224, 219, 235, 221 and 244 escorted 4 C.X to Waalhaven (Rotterdam), to bomb it. The D.XXI’s also attacked ground targets.

17.00h 240 escorted T.V 856 to the Afsluitdijk, the dam in the IJjselmeer (former Zuiderzee). They were forced to return by many German a/c.

After this, only 7 D.XXI’s were still able to fight, 219, 224, 235, 236, 240, 242 and 244. 212 and 221 had to be repaired. 231 was still on Texel and was not used.


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## Marcel (Oct 9, 2008)

As we get further, the posts get shorter.


Still from Buiksloot:
03.58h 219, 235, 240, 242 and 244 took part in a ground support mission (with 4 C.X's) to the Grebbe line. All D.XXI's got damaged by Flak. 219 suffered a failure in one of the MG's, which emptied itself.
11.34h: 212, 224, 240, 236, 240 and 242 repeated the previous mission. 224 was severely damaged.

There were no clashes with German fighters as the fighters flew on the deck all the time. The Dutch camouflage showed itself to be effective. The fighters had been using this tactic since May 11th. However the repeatedly damaged and repaired aircraft were wearing out and desperately needed replacement. There were none.


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## Marcel (Oct 9, 2008)

In the night 13-14th of May, the Dutch army retreated from the First line, the Grebbe-line (Near Wageningen) to the Water-line near Utrecht. The Dutch army also feared a German landing north of Amsterdam, over the IJselmeer. Buiksloot was considered to be too close to the lines, so the JaVA was transferred to Schiphol airport. In the mean time they had to cover the Dutch field army. 
As the groundcrew had worked very hard during the night, 10 D.XXI's were ready again. Because of fog, the first patrol could only be made at 07.05 h. This patrol was done byt 221, 236, 240, 242 and 244. 236 crashlanded and was set on fire by the pilot, sgt. Sitter. 205, 219, 221, 224 and 235 flew the short flight to Schiphol.
10.45: 8 D.XXI's were battleready. 212, 219, 221, 224 and 235 patrolled the area.
Condition of the pilots was so bad that flights were suspended. Preparations were made to fly the a/c to the UK, but when the army surrendered at 19.00h, this was forbidden by the high command. All D.XXI's were then set on fire against the order of the high command.


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## Vincenzo (Oct 9, 2008)

Beautiful work Marcel


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## Marcel (Oct 9, 2008)

After the surender, the following D.XXI's were captured by the Germans:
217 and 228 at Ockenburg
231 on Texel
245
230 and 232 at Schiphol
220 at the Fokker factory.

231 crashed on october 16th, badly injuring the German pilot.

1. 230 at Schiphol, the Fokker symbol in the tail was taken as a souvenier.
2. 231 in LW markings at Jever.
3. The burned D.XXI's at Schiphol after the fight. In the back, a disabled KLM DC2


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## Marcel (Oct 9, 2008)

D.XXI pilots and groundcrew who fell in the 5 days:

Kapt.Tel L.J. van Beerschoten
Wmr. Vl. J. van Zuijlen
Elt.Vl. A.H. Bodaan
Sgt.Vl. F.C.H. van Looijen
Dpl. Sld. W.G. Kern
Sgt.1 Vlm J. Barendregt
Dpl.Sld. W. Muilenburg


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## Marcel (Oct 9, 2008)

Thanks Vincenzo, I try.


Claims by D.XXI pilots:

Aarts, P.J.(217), 1x Messerschmitt Bf-110 
Doppenberg, H.(221), 1x Messerschmitt Bf-109E-3 
Droste, F.(228 ), 1x Junkers Ju88 
Eden, J.(247), 1x Messerschmitt Bf-110C-1 
Geus de, G(236), 1x Dornier Do-17 
Grave de, F.L.M. (213), 1(2)x Messerschmitt Bf-110 
Hateboer, W.(244), 1x Junkers Ju88 
Kiel, G.(216), 1x Junkers Ju52 
Linzel, J.(246), 1x Messerschmitt Bf-110 
Overvest van, H(219), 1x Messerschmitt Bf-109 
Plesman, J.C.(212), 1x Junkers Ju52 
Roos, J.(229), 2x Messerschmitt Bf-110 
Sitter, H.(236), 1x Messerschmitt Bf-109 
Sluyter, N.(225) , 1x Junkers Ju88 
Smits, P.(242), 1x Messerschmitt Bf-109
Stok van der, B.(234), 1x Messerschmitt Bf-109 
Vaart van der, A.M.(212), 1x Dornier Do-215B-4


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## Juha (Oct 11, 2008)

Marcel
Thanks a lot for the excellent info!

Juha


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## Marcel (Oct 12, 2008)

Thanks Juha.

I think this concludes the story about the Dutch Fokkers, sadly not a very long one. Maybe I'll post some snippets of info later, but I think the main story is already told.

So what do you think, was the Fokker D.XXI the right a/c at the right place or should the Dutch have bought other planes?

In 1940, the Dutch command preferred the G.1, which is obvious as the G.1 was clearly the more advanced a/c. The G.1 was deadly in the air, which is shown by the fact that the 3e JaVA (G.1) shot down 14 German a/c against the loss of 1 in the early minutes of the war. This while they were surprised on the ground and still had to take off. But the main disadvantage was shown when they had to land again. As Waalhaven airport was not available, they could land nowhere, needing concrete strips, and crashlanded in the neighbourhood. Most of them could not be used in the following days. The D.XXI however, could take off and land almost everywhere, and was quite easy to repair and maintain. It also proved itself quite capable of fighting the Bf109/Bf110, see for instance the dogfight over the Waddenzee by between 1e JaVA and 4./JG186.
I would argue that more emphasis on the production of the D.XXI, in higher numbers would have had more impact on the war. If say a 100 or even maybe 50 of these fighters would have been available, flying from almost any piece of grass available, far more would have survived the first day and perhaps they would have had the chance to attack the German bombers, bombing Rotterdam on May 14th. Maybe the Dutch then would have lasted many days longer for the benefit of the allied forces.

As it was now, the number of fighters (total of 52 G.1's and D.XXI's) was far too few to make any impression on the massive German Luftwaffe.


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## HoHun (Oct 12, 2008)

Hi Marcel,

>In 1940, the Dutch command preferred the G.1, which is obvious as the G.1 was clearly the more advanced a/c. 

I've added a quick analysis of the G.1 to the D.XXI comparison, simply using the engine data from the D.XXI with the parameters of the G.1 (relying on 475 km/h top speed at 4500 kg for calibration).

Regards,

Henning (HoHun)


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## Marcel (Oct 12, 2008)

so the G.1 could turn even faster than the D.XXI? Great stuff Henning!


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## HoHun (Oct 12, 2008)

Hi Marcel,

> so the G.1 could turn even faster than the D.XXI? Great stuff Henning!

It's not so surprising if you consider that at twice the weight and twice the power, it has more than twice the wing area 

I have added another graph for the Me 110C-1 at 6040 kg (later versions tended to be heavier).

Regards,

Henning (HoHun)


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## Marcel (Oct 12, 2008)

Thanks Henning, I was wondering what the Bf110 would do in the equation, so here I have the answer. Good job.


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## Juha (Oct 12, 2008)

Hello Marcel
even if I have past couple decades defended the decision to buy Fokker D.XXIs to Finland even if many with more knowledge had been critical to that decision, among them the Grand Old Man of FAF fighter aviation, colonel Lorentz. XXI was rather cheap, licence production went smoothly and it's climb rate was reasonable. But IMHO both FAF and Dutch would have made a wise move if they had purchaced Curtiss Hawk 75As as their main fighter and bought a reasonable number of XXIs as interceptors because 75A wasn't a great climber. IMHO only realistic European alternative for Hawk 75A was Fiats, producers needed better fighters themselves and even if G.50 was a reasonable fighter it was a difficult plane to maintain.

XXI vs G.1 I agree with You. Dutch planning should have been based a longer resistance than happened and it would not be reasonable to assume that their permanent bases would stay operational very long. So their fighters should have been able to operate from improvised strips and be easily repairable. Acting a bit like guerilla AF.

Juha


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## Marcel (Oct 13, 2008)

Hi Juha, I believe the Hawk was not even considered by the Dutch. They were focused on either a more advance a/c like the He112 with Db601 engine or the Spitfire. I think you're right that the Hawk could have been a good alternative, especially because of it's greater speed of about 500 km/h. But climbspeed was very important as there was hardly any defence depth (The Netherlands is only about 150 km deep from east to west) and the warning system was very old fashioned and slow. 

About the Fiat G.50, I'm not so sure. I believe they would not have fared better than the D.XXI. 

I still think the D.XXI was not such a bad choice after all, if they would have been ordered in greater numbers. Especially for the Guerilla airwar the Dutch had to fight.

I think the choice for the G.1 was because of it's nature. The Dutch expected to be neutral and thought they mainly would have to patrol the borders. Being a Luchtkruiser, the G.1 would have been ideal for the job. A big miscalculation from their part.


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## Juha (Oct 13, 2008)

Hello Marcel
I doubt that He 112 was even as good plane as Hawk 75A. IIRC Romanian He 112s suffered rather bad losses in summer 41. On the other hand Hawk 75A was the most successful fighter of French AF in 1939-40. Finns used it as first line fighter up to Sept 44, even if it was outclassed in 44. And RAF used Mohawk IVs (75A-4) in 43-44 in Burma.

Spitfire on the other hand was a dream, RAF needed them themselves.

IIRC May 40 over Netherland was mostly low level affair, so the climb ability wasn’t after all so important. Hawk 75A was also very rugged plane and reliable, save problems with Cyclones. And it could operate from primitive airfields.

I understand the neutrality aspect but really, defence planning should take into account also the worst case scenarios. D.XXI as a good climber could have handled high flyers, at least show the flag even if it could not always catch intruders.
And the flight time of Hawk 75A was 3-5 hours, so it really could fly long patrols.
Juha


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## Marcel (Oct 13, 2008)

Juha said:


> Hello Marcel
> I doubt that He 112 was even as good plane as Hawk 75A. IIRC Romanian He 112s suffered rather bad losses in summer 41. On the other hand Hawk 75A was the most successful fighter of French AF in 1939-40. Finns used it as first line fighter up to Sept 44, even if it was outclassed in 44. And RAF used Mohawk IVs (75A-4) in 43-44 in Burma.
> 
> Spitfire on the other hand was a dream, RAF needed them themselves.
> ...



The He112 would have been the one with the Db601a engine, so more in league with the Bf109E. I believe the Romanian ones were powered by the older Junkers Jumo. Spitfires and Hurricanes were actually offered to the Dutch and they did test them thoroughly. None were bought in time however, as the war started earlier then the government had anticipated.

Low level was only because the Dutch, being fastly outnumbered, didn't fly higher then on-the-deck. They would have been slaughtered by the 109's if they got slightly higher.
I agree with you on the government being too short sighted and also that the Hawker should have been considered.


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## HoHun (Oct 13, 2008)

Hi Juha,

>I doubt that He 112 was even as good plane as Hawk 75A. 

That's probably a fair assessment - the Hawk 75 in French service did very well against the Me 109D with a Jumo 210 engine, so the like-engined He 112 probably would have fared no better.

If Marcel talks about the DB601-engined He 112, the Hawk would probably not be superior to that one though.

I have actually prepared a comparison Me 109 vs. Hawk comparison for a discussion on another board ... no Hawk 75A but just a Hawk 75C in there, but here it is anyway. (The "Super Hawk" with a two-speed, two-stage supercharged engine from a Wildcat was the focus of that discussion. I don't believe it was ever built, but it appears to have been considered historically).

Regards,

Henning (HoHun)


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## Juha (Oct 13, 2008)

Hello HoHun
I have never heard on Hawk 75C, but both P-36A and C used R-1830-17 engine. Max speed for P-36A was 313 mph at 10,000 ft and 311 mph at 10,000ft for P-36C (it had 2 wing mgs added to 2 mgs in nose which was A's armament)

Juha


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## Juha (Oct 13, 2008)

Hello HoHun
Test flight report of CU-503 after engine change from Cyclone to Twin Wasp R-1830-SC3-G. Speed 372 kmh IAS at 2350m. Air pressure and temperature is given on the uppermost part and temperature at air intake is on the lowest line, max speed column at right.

Juha


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## kool kitty89 (Oct 13, 2008)

The Performance for the Hawk with the 1830-17 engine would be with 100 octane fuel. (due to the low critical altitude, and high low-level speed)

And the He 112 was suposeddly somewhat superior in performance to the Bf 109 with the same engine. (~20-30 km/h faster, 510 km/h for the B-2 with Jumo 210G) And also had significantly better range.
The main disadvantage to the Bf 109 being much greater parts count and elliptical wing making it more difficult to construct. (and possibly more difficult to repair)

The Hawk would still have significantly better range though.


Interesting "Super Hawk" concept, somthing I've thought about before, but in combination with a tight fitting cowling with latge spinner and cooling fan. (of the final version used on the XP-42)


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## HoHun (Oct 13, 2008)

Hi Juha,

>I have never heard on Hawk 75C, but both P-36A and C used R-1830-17 engine. 

Problem is, I didn't do the research myself and the board on which the discussion was is inaccessible now so that I can't go back and look. At the time I thought the information looked quite well-researched, but I don't recall what exactly the Hawk 75C was. I guess it was one of the Hawk batches acquired by the French.

>Max speed for P-36A was 313 mph at 10,000 ft and 311 mph at 10,000ft for P-36C (it had 2 wing mgs added to 2 mgs in nose which was A's armament)

This seems to match my data, but if I recall correctly there were some internal contradictions in the source data (as so often - sigh!).

Regards,

Henning (HoHun)


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## HoHun (Oct 13, 2008)

Hi Juha,

>Test flight report of CU-503 after engine change from Cyclone to Twin Wasp R-1830-SC3-G. Speed 372 kmh IAS at 2350m. 

Thanks for the data sheet!  The speed looks rather disappointing compared to the factory figures, or am I missing something?

Regards,

Henning (HoHun)


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## Juha (Oct 13, 2008)

Hello HoHun
French versions were A-1 - A-4. But french used text 
Curtiss
H75-C1
No. XX

in the rudders of their Hawk 75A-1 - A3, A4 was for French H751.
The C1 in Frech Hawks only means 1 seat fighter. C came from Chasse fighter. But French Hawks didn't have 1830-17 engines but civil versions like 1830-SC-G or 1830-SC3-G or 1830-S1C3-G or 1820-G205A.

Juha


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## Juha (Oct 13, 2008)

On CU-503
Yes Finns noticed that and even if they only used 87 octane in tests FAF concluded that only way the factory figures were possible was that in addition of the use of 100 octane fuel a/c had to be waxed, mgs, antenna and other projecting equipment removed. IIRC RAF also got worse performance than those in Curtiss' procures but on the other hand French got more or less same performance as Curtiss.

Juha


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## Juha (Oct 13, 2008)

BTW
Curtiss figure for 100 octane engines were for 1830 423kmh at SL and 520 kmh at 4650m and for
1820 413 kmh at SL, 467 kmh at 2500m (max for low blower gear) and 488 kmh at 5790m. Which after all is nearly same as what British got for Mohawk IV that is 486 kmh at 4300m. Brewster B-239 with lower powered Cyclone 1820-G5 was fastest at appr 4900m. So a bit variation for max speed altitude of Cyclones.

But now we had hijacked Marcel's excellent Fokker D. XXI thread, sorry Marcel.

Juha

Juha


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## Marcel (Oct 14, 2008)

No problem, we were discussing alternatives to the D.XXI.


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## Juha (Oct 14, 2008)

Hello HoHun
these test flights were normal tests after major repairs not special tests to clarify the performance of certain a/c type.
I checked a couple more similar tests

CU-502 25.6.41 992mb +22C 385 kmh IAS at 2810m, engineWright Cyclone GR-1820-G-205A
my rough estimation appr 452 kmh TAS, and I'm a historian not an aerodynamist.

CU-502 28.7.43 1003,7mb +25,8C 385 kmh IAS at 2350m, engine P&W R-1830 SC3-G
my rough estimation appr 431-444 kmh TAS.

CU-575 31.7.43 1006,4mb +19,8C 388 kmh IAS at 2350m. my rough estimation appr 435-448 kmh TAS.

Juha


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## Marcel (Oct 16, 2008)

Here a few pictures of the D.XXI replica at Soesterberg. Gives you an idea of the colours. The camo is not entirely correct though:


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## Marcel (Oct 17, 2008)

7./JG 3 Uffz. Massman Rotterdam (Sgt. Looijen 225)
7./JG 3 Uffz. Springer Rotterdam Waalhaven (Lt. Bodaan 238 )

5./JG 26 Stafferabschuss Amsterdam ?

3./JG 51 Oblt. Leppla Zevenbergen (Maybe actually Fokker G.1 330?)

5./JG186 Lt Hevler De Kooy
5./JG186 Ofw. Ubben De Kooy
5./JG186 Ofw. Thaut De Kooy
5./JG186 Uffz. Kaiser De Kooy
These 4 probably all claim the same a/c, 241 Lt. Bosch, destroyed while landing

3./JG 26 Oblt. Seifert Rotterdam 
6./JG 27 Fw. Kreuz Rotterdam (? no D.XXI in the area at the time (14.20h))
1./JG 51 Lt Strehl Rotterdam (? no D.XXI in the area at the time (14.20h))
1./JG51 Ofw. Sicking Rotterdam ?


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## Juha (Oct 20, 2008)

Hello Marcel
Thanks for the German claims and for the analyze of their victims.
This thread has been really amazingly informative.

Juha


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## Marcel (Oct 21, 2008)

Juha said:


> Hello Marcel
> Thanks for the German claims and for the analyze of their victims.
> This thread has been really amazingly informative.
> 
> Juha



Thanks for your kind words and also a big thank you to you and Henning for your contributions so far. 

If anyone knows more about those German claims, please contribute.


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## Marshall_Stack (Oct 22, 2008)

Very interesting thread! It is hard to find accounts such as these in the States (AFAIK). I love accounts of underdogs and how they fought with what they had. Also, I have been to the Netherlands twice and fell in love with the country. I didn't have time to visit any WWII sites. I wish I had the time to at least visit the Arnhem area.


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## Marcel (Oct 22, 2008)

Thanks Marshall! You won't believe it, but it's somewhat hard here as well. Luckily the sources are there, but it takes some energy.. Although I realise most people are more interested in Spitfires and Messerschmitts, I thought this could be interesting. It's good to know that it's appreciated. 

I would like to see more of these minorities here on the forum, maybe IAR 80 planes by a Romanian, or the efforts of the Norway AF in 1940 etc. Maybe some-one will start one or two of these threads in future. I myself would like to start a similar thread on the G.1 as well. Maybe I'll do that in a few months.

Whenever you're in the neighbourhood again, please notify me. Maybe I could point you to some good WWII sites.


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## Marcel (Oct 25, 2008)

1. D.XXI at Soesterberg, combined JaVA
2. Prototype at Welschap airfield note that it's fitted with a 2 blade airscrew, contrary to productioen D.XXI's


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## Watanbe (Oct 26, 2008)

Thanks a lot for this thread Marcel. I found it very interesting. I also love hearing about the lesser know aircraft of WW2. 

I think the D.XXI was the correct aircraft to be chosen. It appears according to the statistics posted capable enough without being exceptional and the Dutch could have done a lot worse. 

It's simple construction and ease of repair would of been crucial, when you consider how swamped the Dutch were. More sophisticated and therefore complex planes would have not been able to see the air as much as the D.XXI


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## Kocur (Dec 15, 2008)

Marcel said:


> Hi Hohun,
> 
> Top speed: 460 km/h at 5100 m (at 2750 rpm engine), with full miliary load: 415 km/h.



I happen to have a book in French: Profils Avions 009 - Le Fokker D.21, by Peter de Jong, full 223 pages on D.XXI 

Fokker advertised D.XXI in early 1936 to be able to attain top speed 460 km/h with fixed gear and 475 km/h with retractable. 
The promise obviously was not fulfilled in case of FR-76, which was capable of merely 414 - 418 km/h. But FR-76 was different to prototypes in:
- having Ratier prop, instead of Hamilton Standard (top speed with HS prop was 430 km/h, according to NLL!)
- having larger wheel covers, which could have wheels replaced with skis,
- bulges for Oerlikon cannons (without the guns),
- bulge for landing light,
- a little different cowling.

As we know the Finnish contract was the first one. After a while Dutch government was interested in D.XXI again, demanding it would reach 440 km/h. So Fokker made a number of slight, yet meaningful aerodynamical changes after which they calculated D.XXI top speed would be 447,5 km/h.
The first Dutch-ordered D.XXI, numbered 212 was first flown in 26 May 1938 and then was transferred to NLL or Nederlands Luchtvaart Laboratorium, that is - in my understanding - a STATE organisation. I'd like to stress that, because it means that following numbers are not Fokker advertising, but real performace. The 212 attained following speeds:
- 460 km/h without radio and armament and
- 446 km/h 'in full combat gear'.
I find those results perfectly reasonable, I mean the masts and wiring of radio antennas and gun ports/barrels should IMHO cause that kind of speed loss due to extra drag.

So I think HoHun can safely change his charts for performace of Dutch D.XXIs 

Regarding climb the book says the following: "Avec l'helice au petit pas, l'appareil grimpe a 4000 m en 4 min et a 7000 m en 8 min 3 s. Le D.21 satisfait ainsi aux exigences: 5 min et 9 min 7 s.". Now, my French is almost non-existent so correct me if I'm wrong in thinking that it was surprisingly good 4 minutes to 4 km (btw.: the HS prop was not CSP but two-pitch), while the requirement was 5 minutes. I wonder if that very nice result, corresponding with relatively very low powerloading (lower than Bf 109E), was attained with or without radio and guns? Guns and ammo (300 rds per gun) would add like 80 kg and radio would mean some dozens kilograms more. Btw. D.XXI no 212 weighted empty 1426 kg, i.e. 26 kg less, than contract provided.


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## Marcel (Dec 17, 2008)

Hi Kocur,

Thanks for the info. Yes, the Luchtvaart Laboratorium is a state institution. I've also read these figures, but couldn't confirm them.
I'm planning a trip to the Dutch Military archives early next year. They're supposed to have additional test reports of the 212. Will be interesting to see the original findings.

Marcel


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## Juha (Dec 19, 2008)

Hello Kocur
interesting info, even if I'm a bit doubtful.
Finns tested several D.XXIs and in average the max speed was around 415kmh. 
On wheel covers, how much smaller were the Dutch ones? I have never noticed the difference.
According to Finnish tests the cannon bulges lowered the max speed only 1-1½kmh, so IMHO the effect of the bulge for landing light couldn't have been much bigger.
The effect of a different prop could have been more significant, maybe even the 15kmh mentioned.
IIRC Dutch D.XXIs were a bit lighter than FAF's, so a little better climb rate is entirely possible.

Juha


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## Marcel (Dec 19, 2008)

Juha,

The figures posted by Kocur sometimes pop up in books and internet when researching. Tha majority of the numbers however are lower, not much different of the Finn's numbers. Which one is correct, I don't know.


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## Juha (Dec 20, 2008)

Hello Marcel
a/c were individuals, some were a bit faster than others even from the same production batch. And by careful filling and polishing it is possible to gain some extra speed. So with a different prop, smoother skin, w/o the bulge for the landing light and possible small differences in landing gear IMHO 430kmh is possible for a good example. And with small aerodynamic improvements here and there some extra gains are perfectly possible. So 436, 440 or even 446kmh, maybe, but I don't know. And anyway, during intensive combat period at least the smoothes of skin would deteriorate with some loss of speed.

Juha


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## Marcel (Feb 1, 2009)

Some pictures I took of the replica at Soesterberg. The lights are very bad in the museum, sorry for that.


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## Marcel (Feb 1, 2009)

Juha said:


> Hello Marcel
> a/c were individuals, some were a bit faster than others even from the same production batch. And by careful filling and polishing it is possible to gain some extra speed. So with a different prop, smoother skin, w/o the bulge for the landing light and possible small differences in landing gear IMHO 430kmh is possible for a good example. And with small aerodynamic improvements here and there some extra gains are perfectly possible. So 436, 440 or even 446kmh, maybe, but I don't know. And anyway, during intensive combat period at least the smoothes of skin would deteriorate with some loss of speed.
> 
> Juha



I found out that the Dutch a/c actually had a smoother cowling. Also the propeller was different. After the Dutch bought it, Fokker did everything to reach the 460 km/h speed as required in clean configuration. And the succeeded. The speed of an operation D.XXI was not 415 km/h as I stated earlier, but around 435 km/h at the acceptance trials (source Fokker).


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## Juha (Feb 2, 2009)

Thanks Marcel!
And nice pictures, I also took some photos of the replica when I visited Soesterberg in 2005.

Juha


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## Fokker D21 (Feb 3, 2009)

Thanks from me as well. 

Then to think that our Dutch government at first didn't want it. I sure hope we are not going to make the same mistake again by not buying the F-35 Lightning 2.


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## Marcel (Feb 4, 2009)

Hi Fokker, good nick  
I see you're from the same town as I am.


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## Viikate (Feb 5, 2009)

Hello all! I had to register just for this thread 

So what it the final verdict on the speed issue? I would like to know TAS of Dutch variant at sea level and 5000m. 

Would these be close? 340km/h TAS at sea level 440km/h TAS at 5000m 

Thanks!


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## Marcel (Feb 5, 2009)

Hi Viikate,


Viikate said:


> Hello all! I had to register just for this thread
> 
> So what it the final verdict on the speed issue? I would like to know TAS of Dutch variant at sea level and 5000m.
> 
> ...



I hope it was worth it 

I'm still not 100% sure. I found info from Fokker, claiming at the acceptance trials a speed of 435 km/h at 5000m. This was supposingly with full gear, although this was the 212, which lacked for instance the radio at the time, AFAIK. Clean, the D.XXI clocked 460 km/h at 5000, that's for sure. I could not read the whole report. I'm still planing for a trip to Lelystad, where the Fokker archieves are stored. There should be a wealth of info there.


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## Viikate (Feb 5, 2009)

Definately worth it 

460 km/h sounds bit too much. I would like to have it in some normal combat weight setup with radio and such, since I'm trying to make a flight model for sim. 435 sounds pretty good, so I'll go with this value or maybe slightly less.

Also it would be helpfull if someone could confirm the amount of cannon rounds in danish fokker. This site claims that is was 500/cannon. That's just crazy.

AERONET GCE / IBERONET: Fokker D.XXI part 1 (Spain and Denmark))

Thanks.


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## Marcel (Feb 5, 2009)

The manual claims a top-speed of 460 km/h at 5100 km/h at an engine speed of 2750 rpm. As far as I can determine, the prototype for the Dutch version had a top speed of 445 km/h at the first trial tests. Under pressure of the Dutch government, Fokker adjusted the a/c (streamlining) to get a top speed of 460 km/h at 5100m. They succeeded. This was of course a clean a/c without armament etc. The tests with 212 shows that after installing military equipment, the top speed dropped to 435 km/h.

I unfortunately now very little about the Danish D.XXI's. I was hoping to attract some Danish members to give some info on them.


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## Ruud (Mar 5, 2011)

Hoi Marcel,
Great stuff on the Fokker and on May 1940.

My Oma told me that she was out hanging up the wash on the morning that the Germans attacked the Kooij. They lived in Breezand at the time. I grew up just a few minutes from the Kooij.

later
Ruud


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## rank amateur (Mar 14, 2011)

Hi Marcel,

Great info. I remember reading a book about the subject about 30 years agoo. I thought by Hugo Hooftman but considering the time that has passed the name of the author could be wrong. Anyway,in the same series there was also a book about the G1 in may '40. These books are no longer in print so long live the internet and historians like you.

Chrzzzz


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## Marcel (Mar 17, 2011)

Hoi rank,

De stichting Fokker G.1 zal dit jaar een boek uitbrengen over de G.1. Veel nooit gepubliceerde foto's en info. Een aanrader!
The Fokker G.1 foundation will publish a book of the G.1 this year. Many photo's and info that was never published before.


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## rank amateur (Mar 17, 2011)

He, bedankt. Ik zal hun site in de gaten houden. Are you familiar with the books I've mentionned. I distinctly remember volumes about the D21, the G1, the T5 and the CV/CX but like I said, this was over 30 years agoo. Your memory tends to play tricks with you. Chrzzzz


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## Marcel (Mar 17, 2011)

I think you're talking about the Nederlandse luchtvaart encylopedie. Yellow cover, red letters? They are well know and a good read, although slightly outdated nowadays. They are quite rare these days and many want to have them. Very expensive on the market. And you're right, Hugo Hoofdman wrote them.


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## Marcel (Mar 17, 2011)

Ruud said:


> Hoi Marcel,
> Great stuff on the Fokker and on May 1940.
> 
> My Oma told me that she was out hanging up the wash on the morning that the Germans attacked the Kooij. They lived in Breezand at the time. I grew up just a few minutes from the Kooij.
> ...


 
Hoi Ruud,

Did your grandmother see the 10-may dogfight? Did she tell you anything about it? I would like to hear/read about it.


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## rank amateur (Mar 18, 2011)

Hi Marcel, I think you're absolutely right. I should check the public librairy. That was the place 30 years ago where I read those. In my opinion there stil is a market for those books. I wonder who owns the rights. Is about time for an 2011 edition.

Thanx


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## Ruud (Mar 18, 2011)

Hoi Marcel,

She never mentioned seeing any fighting, but she did clearly remember planes flying to De Kooij. She said German planes, but i do not know how familiar she was with the aircraft types in the area. Like most of her generation, she spoke very little of that time.

My great uncle was killed during the fighting at the Grebbe line. He told his squad to get out of a "bunker" (not sure if it was a pillbox, bunker, or other fortified position) while he held off the Germans. When they looked back they saw an explosion in the bunker. Artillery? Satchel charge?

Another great uncle was picked to go to a work camp (my grandmother slaughtered a pig and that was a no-no, so he confessed to it). He got off the train and went into hiding in Friesland (IIRC). My Grand parents on my mothers side had a radio in the attic. They also hid their bikes on top of a shed. They had NSBers living across from them. Again, not much told to us, and they are sadly no longer with us to ask them for more.


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## Marcel (Mar 19, 2011)

Ruud said:


> Hoi Marcel,
> 
> She never mentioned seeing any fighting, but she did clearly remember planes flying to De Kooij. She said German planes, but i do not know how familiar she was with the aircraft types in the area. Like most of her generation, she spoke very little of that time.
> 
> ...


Not surprising but a pitty. I've got the same problem. A family story is that my grandfather barely escaped execution as he was in the communist resistance, mainly involved with the De Waarheid/Noorderlicht. Unfortunately he passed away long ago when I was little, so I never could ask him. I'm now researching what really happened, as the family story sounds too fantastic to be true.


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## pauljos2001 (Feb 7, 2012)

Marcel said:


> According to my sources, no Dutch D.XXI was ever fitted with canons. All a/c had 4 LMG's. As Juha mentions, Finnland tried 20mm canons on the D.XXI and I believe the Danish AF did, too.



I am new on this forum and followed the great explanations about Fokker DXXI.
However some photobucket pictures are not visable any more.
Is it possible to renwe the link or post the pictures once more.

regards 
pauljos


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## Siegfried (Feb 8, 2012)

Marcel said:


> Hi Viikate,
> 
> 
> I hope it was worth it
> ...



If a retractable undercarriage was incorporated how much speed could be gained? I expect about 5%.


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## Juha (Feb 8, 2012)

Hello Siegfried
Finns modified 2 D.XXIs with retractable undercarriage, the results of the first mod were disappointing but the second mod was more successful. I'd have test info on those mods somewhere, if you are intrested in those, I'll try to dig the info up.

Juha


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## Siegfried (Feb 9, 2012)

Juha said:


> Hello Siegfried
> Finns modified 2 D.XXIs with retractable undercarriage, the results of the first mod were disappointing but the second mod was more successful. I'd have test info on those mods somewhere, if you are intrested in those, I'll try to dig the info up.
> 
> Juha



Please do, this would be good data on the effect of such an effort.


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## Juha (Feb 9, 2012)

It seems that the retractable undercarriage system of FR-117, a Mercury VII powered D.XXI was deemed so unsuccessful that there were proper speed tests made only with skies before it was remod back to fixed u/c. But mod of a Twin Wasp Jr engined FR-167 succeeded better, its max speed at SL was 367km/h and at 3000m 387km/h, when the figures for a normal Wasp Fokker were 342km/h at SL and 350km/h at 3000m (when figures were corrected to standard atmosphere FR-167 was at SL 20km/h faster and at 3000m 50km/h faster than the control plane FR-143). Strange thing is when the MU’s test pilot declared that FR-167 was not suitable to front-line service one of the COs of flight regiments disagreed and one of his subordinates organized new tests, according to which FR-167 max speed at SL was 408km/h and 423km/h at 2800m. I personally believe more the official tests, even if a daughter of the pilot who flew the later tests served many decades later as our Minister of Defence.

Juha


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## Marcel (Feb 18, 2012)

pauljos2001 said:


> I am new on this forum and followed the great explanations about Fokker DXXI.
> However some photobucket pictures are not visable any more.
> Is it possible to renwe the link or post the pictures once more.
> 
> ...


I guess you're referring to the pictures with the Danish D.XXI's. Unfortunately I don't posess them, so I cannot repost them. The site where I linked to apparently hosted the pictures from photobucket. The site is still online, but the pictures are gone. sorry.


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## Marcel (Feb 18, 2012)

For the people interested: Last week a new book was released about the D.XXI. I know there is a version in Dutch, but I don't know if it's also published in other languages. I haven't read it, yet. Maybe it can clear up some facts in this thread. I'll let you know when I have the book.


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## rank amateur (Feb 18, 2012)

Hi Marcel,

Can you provide me with an exact title and a publisher?

Thanx in advance.


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## Marcel (Feb 21, 2012)

Natuurlijk:
Lanasta // Violaero - Fokker - Fokker D.21 - Fokkers laatste eenmotorige jager.


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## Ruud (Mar 21, 2012)

1e JaVA Squadron BB - Powered by vBulletin

A forum just for the 1 JaVa. Might have some good stuff there.


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## Marcel (Mar 22, 2012)

Seems to be an Ill-2 forum, so only virtual flying. I rather go looking here: Nederlandse Luchtvaart - Dutch Aviation


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## Ruud (Mar 22, 2012)

oh well, looked good upon first glance.

Cool, new one to me.


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## Ruud (Mar 22, 2012)

MilSpotters.nl • Inloggen

Has some nice pictures too. Mostly jets though (but plenty of early jet stuff).


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## Marcel (Sep 17, 2012)

Okay, I got some more info on the performance from the new book I mentioned earlier. The story is like this:
The prototype with a less powerfull engine (Mercury IVS, 645 hp) and less refined clocked around 403 km/h (more or less, hard to get some figures). When Fokker made the final refinements, they claimed a topspeed of 460 km/h with a Mercury VII engine. The Finish version however didn't reach that speed, but clocked 418 km/h at 5100m on average. The Dutch NLL measured a max speed of 414 km/h on the FR-76. However, the Finns had requested a Ratier propellor. Fitted with a Havilant Hamilton propellor, the FR-76 could reach 430 km/h. One should note that the FR-76 was prepared for carying guns at Fokker and these fittings took a few kilometers from the topspeed. This explaines the difference for the FR-76.
The Dutch government asked Fokker to improve the topspeed of the D.XXI. 
1. They were fitted with a 2-speed Hamilton propellor (like said before), therefore fitted with a Mercury VIII. This engine had the same output as the VII, but was better suited for the Hamilton propellor beacuse of the transmission.
2. They got slimmer leggs. The Finns had requested 'thick' leggs for the undercariage. This costed some km in topspeed as well.
3. The cowling was made smooth, the finns had bulbs at the heads of every cylinder.
4. The landinglight was replaced by lights that fitted in the leading edge of the wing, therefore not causing more drag.
5. All MG's were fitted in the wing, therefor saving the weight of the synchronisation gear.

When the first Dutch D.XXI, the 212, was tested, it reached a speed of 460 km/h at 5100m. When fitted with weapoms and radio, the speed dropped to 446 km/h, still 30 km/h faster than the Finnish version. The weight dropped from 1594 kg (Finnish version) to 1426 kg (Dutch version). THis also had a positive influence on the climbspeed. Climbing to 3000m took the Finnish version 3m27s while 3m06s for the Dutch version. for 5000m these are 6m23s (Finnish) and 5m18s (Dutch).


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