20mm in Fokker D XXI

[martin66]

Hello

Somebody knows why the finns replaced the 20 mm cannons of theirs Fokker D XXI by machine guns during the Winter war?

Thank you in advance.

Martin

[Juha]

Hello there was only one FAF D.XXI with 20mm armament, FR-76. There reason given was that with its limited ammo supply (60 rounds per gun) and lower Rof it was not very suitable to fighter vs fighter combat and that anyway 7,7 mm Browning was still reasonable effective against Soviet bombers. Was it really so, it is debatable.

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 on climbing turn etc. So cannon D.XXI was a bit less manoeuvrable.

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 during a major overhaul.

Juha

[martin66]

Hi Juha

Your aswer was very clear and complete. Thank you.

Martin

[Snautzer]

one other reason was that the wing warped when the cannon was fired so it wasnt a stable firing platform anymore

[martin66]

Do you know if the 3 2/3 victories were all bombers? And what type of them?

Martin

[Pilot]

Excellent article with drawings made by Pentti Maninnen have been published in one old issue of SIHL magazine.

[F19Gladiator]

Originally Posted by Pilot

Excellent article with drawings made by Pentti Maninnen have been published in one old issue of SIHL magazine.

"SIHL" magazine ????

Suomen Ilmavoimat.....H......L......

Kindly use full name of the magazine

Br
Goran

[Kari Lumppio]

Originally Posted by F19Gladiator

"SIHL" magazine ????

Suomen Ilmavoimat.....H......L......

Kindly use full name of the magazine

Br
Goran

Hej!

Suomen ilmailuhistoriallinen lehti

Homepage (In Finnish):
http://www.kolumbus.fi/sil/

Index of magazines (In Finnish):
http://www.kolumbus.fi/sil/contents.html

Fokker XXi with 20mm Oerlikon SIL 3/1995, see "Tykki-Fokkeri FR-76":
http://www.kolumbus.fi/sil/1995/1995.html


Short English Summary should be available for all issues. All numbers are still available as back issues, though some are in very low numbers (I have heard). For back issues etc. contact via e-mail the magazine (address given at the homepage).

MvH
Kari

[F19Gladiator]

Tack Kari!

Cheers
Goran

[Juha]

Hello Martin, victims were 2 1/6 SBs, 1 DB-3M from 45. BAP and ½ R-5.

Snautzer, what is your source to the info that the wing warped when the cannon was fired. To my knowledge only structural problem during the tests was that the wing covering at the left wing root got creased but the reason was earlier partial failure of fastening of covering material.

Juha