After Finland, Denmark was the second foreign purchaser of the D.XXI and on the 8th of July 1937 a contract was signed for 2 Dutch built D.XXIs and the licence rights for another 10 aircraft to be built by Hoerens Flyvertroppernes Vaerksteder at Klovermarken (near Kopenhagen). The two aircraft built by Fokker (J-41 enJ-42) arrived in Denmark on the 29th of April 1938 and were equipped with Mercury VIS engines, which probably were replaced later by Mercury VIII engines of 840 hp, the same that were fitted in the Danish built machines. Only J-42 was experimentally equipped with 2 Madsen 20mm cannon, mounted in underwing gondolas. But the Danish were not very convinced by the results of the trials made in this configuration and in 1940 all Danish D.XXIs carried only their two engine mounted machine guns and provisions for some 100 kg bomb load as armament. The wooden wings was not strong enough to carry 52kg. of canon, plus ammo etc., so steel flanges and such were build into the wing to support the installation. A large test plan was carried out with J-42, with shooting the canon at air targets, ground targets, moving targets and such. In the end, the total installation of the two canons, with 500 shells per canon, flanges etc., gave the plane a weight that, with full fuel tanks, exceeded the specified maximum take off weight.
Fate of the Danish D.XXIs during the beginning of World War II:
J-41 5480 Stored away in Ringsted 28-06-1940.
J-42 5481 Stored away in Ringsted 28-06-1940.
J-43 103 Heavily damaged under the German attack on Vaerloese, April 9th. 1940. Rebuild as production number 113.
J-43 113 Ex 103, stored away in Ringsted 13-11-1941.
J-44 104 Stored away in Ringsted 20/8-40.
J-45 105 Damaged under the German attack on Vaerloese, April 9th. 1940. Repaired and stored away in Ringsted 04-09-1940.
J-46 106 Stored away in Ringsted 11-09-1940.
J-47 107 Heavily damaged under the German attack on Vaerloese, April 9th. 1940. Rebuild as production number 114.
J-47 114 Ex 107. Stored away at Kloevermarken 06-08-1942.
J-48 108 Stored away in Ringsted 23-09-1940.
J-49 109 Damaged beyond repair under the German attack on Vaerloese, April 9th. 1940. The fuselage of J-49 has been borrowed by a Dutch Museum for measurement to build a D.XXI replica in 1986 to 1988. Today in a Danish museum storage.
J-50 110 Stored away at Kloevermarken 15-11-1942.
J-51 111 Damaged under the German attack on Vaerloese, April 9th. 1940. Stored away in Ringsted 06-08-1940.
J-52 112 Never delivered do to the break out of the war. Delivered without test flight and stored away in Ringsted 15-07-1940.
On the 29th of August 1943 all these aircraft were seized by the Luftwaffe and used by German units as "Luftdienst StaffeIn and Zielschleppstaffeln etc." All planes were apparently out of service in August 1944.
Source:
AERONET GCE / IBERONET: Fokker D.XXI part 1 (Spain and Denmark)