Author Topic: Avia B-35  (Read 5630 times)

Offline darkfold

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Avia B-35
« on: July 10, 2015, 03:25:40 AM »
Some recent project...

Avia B-35 was developed as new standard fighter for Czechoslovak Air Force, replacement for biplane fighters Avia B-534 and counterweight for German fighter Messerschmitt Bf-109. Development started in 1936 and after a series of delays was accelerated during Czechoslovak crisis in 1938. Then it was build in large series by most of Czechoslovak aviation factories but thanks by immature design and shortened tests was accepted for service as in essence a emergency fighter for experienced crews with a number of non-combat losses. After fall of Czechoslovakia in march 1939, B-35/135/235/335 fighters was used by Slovak air force (and particulary by Bulgary air force for training and air defence purposes) in Polish and France campaign and autumn and spring part of Battle of Britain when they was replaced by more successful and reliable fighters Bf-109 and used for training purposes. Last combat appearance of this type series was during Slovak national uprising when a few fighters was used against partisan and soviet fighters and bombers over Slovakia. In Hermann Göring Werke was type serie B-35 further developed to B-435 which wasn’t accepted by Luftwaffe and Slovak air force and was build only in small serie for Bulgaria air force where they were used against allied and soviet bomber groups but without significant success.

List of versions:

B-35 (I.serie) – basic variant of B-35 and child of accelerated development in 1938. Unlike the original intent of designers it was build with weaker engine Avia HS 12Ydrs (licence build of Hispanio-Suiza 12Ydrs) with two bladed fixed wooden propeller, fixed landing gear and armed only by two synchronized vz.30 machine guns (calibre 7,92 mm, 450 rounds for each gun) over engine. 25 serial fighters were produced by Avia Letňany and used manily for training purposes.
B-35 (II.serie) – upgraded version of I.serie and basic fighter variant. Powered by Avia HS 12Ycrs (licence build of Hispanio-Suiza 12Ycrs) with steel two bladed propeller M-100 with adjustable pitch and armed by two machine guns vz.30 and cannon HS.404 (calibre 20 mm, 60 rounds). Construction of plane was upgraded by using of reconstructed, streamlined canopy and cheaper fabric overlay of rear fuselage part. 63 serial fighters were produced by Avia Letňany (36 fighters) and Avia Kunovice (27 fighters) .

B-135 (I.serie) – complete original design intent of B-35. Fuselage, with simplified canopy, based on B-35 (II.serie) was powered by Avia HS 12Y-1000 (license build of Hispanio-Suiza 12Y-38) with three bladed propeller M-103 (licensed Hamilton Standard propeller with constant speed) with adjustable pitch (prototype was powered by Avia HS-12Ycrs with two bladed wooden propeller). Wings have simplified construction with straight leading edge, retractable gear (Messier system) and increased ammo for vz.30 machine guns to 500 rounds for each gun. Pilot safety was increased by using of entrance doors on left side of fuselage and armour plate behind seat. 10 serial fighters were produced in Avia Letňany and used by Czechoslovak Gendarme Air Corps for air defence purposes.
B-135 (II.serie) – improved variant of B-135 I.serie with second entrance door in the right side of cockpit and three demountable Pantoff hardpoints under fuselage and central part of wing. Central hardpoint had maximum payload 200kg, two under wing hardpoints maximum 100kg, total payload that could be used was 300kg. 64 serial fighters were produced in Avia Letňany (27 fighters) and Avia Kunovice (37 fighters).
B-135 (III.serie) – next improvement of B-135 based on II.serie. Because mass production of needs construction which can be produced by smaller producers, fuselage of B-135 which was separated to two parts was added by wing divided to four parts and their construction was adopted by a few machinery and furniture works. Canopy was simplified now with only three windows in removable part, former vulnerable copper surface cooler in left wing and compressor air intake in right wing were replaced by integrated steel cooler and air intake in two pocket coolers in wing roots. 92 serial fighters were produced in Avia Letňany (33 fighters) and Letov (59 fighters)
B-135 (IV.serie) – simplified variant of III.serie with alternative (and independent on special alloys, metals and expensive armoured plywood) wooden wingtips and tail covered by fabric. 110 serial fighters were produced in Avia Kunovice (71 fighters) and Aero (39 fighters), parallel with III.serie in Avia Letňany and Letov.
B-135 (V.serie) – B-135 III.serie with improved wing equipped by two additional vz.30 machine guns with 250 rounds for each gun. Former reflex sight Optitechnika LMP-12A was replaced by new telescopic collimator Srb a Štys. 40 serial fighters were produced in Avia Letňany (36 fighters) and Letov (4 fighters), next 11 unfinished fighters was destroyed together with factories during retreat of Czechoslovak Army from Prague.
B-135 (VI.serie) – B-135 V.serie with same spare improvements as in VI serie (eg. wooden, fabric covered wingtips and tail).61 serial fighters were produced in Avia Letňany (2 fighters), Avia Kunovice (26 fighters) and Aero (33 fighters), after that were factories destroyed during retreat of Czechoslovak Army from Prague and after closing of front to Kunovice.

B-235 (I.serie) – modification of B-35 respectively B-135 which was developed by Zlínská letecká a.s. and adapted basic design of B-35 for powerful radial engine Pratt & Whitney R-1830-S1C3G Twin Wasp respectively Pratt & Whitney R-1830-90 which license was optained by Zlínská letecká a.s. for planned licence build of Douglas DC-3 planes. For this engine was redesigned by forward part of fuselage and modified armament, which consists of two fully covered synchronized vz.30 machine-guns over engine and two synchronized cannons HS.404 in wing roots with 160 rounds for each cannon in ammo belts mounted by same way as in B-135 V. and VI. serie (prototype has cannons replaced by two vz.30 machine guns with 450 rounds ammo belts). Cannons, which license was obtained only with drum magazine fed were for this purposes modified in Zbrojovka Brno where were produced. Other armament and construction modifications were same as in B-135 of II.serie. 31 serial fighters were produced by Zlínská letecká a.s.
B-235 (II.serie) – modification of B-235 I.serie for reconnaissance purposes as replacement of biplane Letov Š-28 type serie reconnaissance and light bomber planes which was outclassed by enemy fighters. Vz.30 machine guns were removed same as Pantoff hardpoints and replaced by cage for installation of one panoramatic camera A-III-30 or two A-II-35 cameras for oblique photorecon. Cage was installed over three glazed visors covered by sliding covers. For night sorties was plane equipped by six Pantoff hardpoints installed in two group of three hardpoints under central parts of wing. It can be used with 20kg flash bombs of parachute flares. 36 serial fighters were produced by Ringhoffer-Tatra.
B-235 (III.serie) – modification of B-235 I.serie by same way as B-135 of III.serie. 44 serial fighters were produced by Zlínská letecká a.s.
B-235 (IV.serie) – modification of B-235 I.serie by same way as B-135 of IV.serie. 24 serial fighters were produced by Ringhoffer-Tatra.
B-235 (V.serie) – modification of B-235 of III.serie by same way as B-135 of V.serie. Besause in each wing was two separate ammo belts, cannon ammo belts were pulled under vz.30 machine gun beds, covered by streamlined covers and led by parallel belt line and fed by three position flap in wingtip. Modification of wing prefabricates were made by Riinghoffer-Tatra engine plant in Kopřivnice. 40 serial fighters were produced by Zlínská letecká a.s.
B-235 (VI.serie) – modification of B-235 of IV.serie by same way as B-135 of VI.serie with wing prefabricate modifications same as B-235 of V.serie. 47 serial fighters were produced by Ringhoffer-Tatra

B-335 (I.serie) - modification of B-135 od V.serie powered by weakest Avia HS 12Ycrs engine thanks by slow production of Avia HS 12Y-1000 engine. 26 fighters were produced in Avia Letňany (19 fighters) and Letov (7 fighters)
B-335 (II.serie) - modification of B-135 od VI.serie powered by weakest Avia HS 12Ycrs engine thanks by slow production of Avia HS 12Y-1000 engine. 18 fighters were produced in Avia Kunovice

B-435/Av-435 – major upgrade of B-135 based on V.serie. Developed in 1940 under supervision of Hermann Göring Werke Konzern which adopted Avia Letňany plant after fall of Czechoslovakia. Now, fully metal construction of fuselage with electron covers were streamlined and its massive tunnel cooler under engine was replaced by new conformal tunnel cooler which was lined under cockpit where it was ended by ejector flap for continuous air stream in tunnel. Complete redesigned all metal wing with slats was equipped by new retracted landing gear which was hinged to the fuselage.  Slack space after former coolers in wing roots was used for ammunition of wing weapons. Fighter was armed by MG-FF cannon (calibre 20 mm, 90 rounds) in propeller axis, two synchronized heavy machine guns MG-131 (calibre 13 mm, 300 rounds for each gun) over engine and four MG-17 machine guns (calibre 7,92mm, 500 rounds for each gun) in wings. Former Pantoff hardpoints were replaced by one ETC 500 hardpoint in centreline which can be used for one 250kg bomb or 300 l drop tank. 60 serial fighters were produced by Avia Letňany for Bulgaria air force.

Offline elmayerle

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Re: Avia B-35
« Reply #1 on: July 10, 2015, 10:58:23 AM »
I like that evolution.  Any chance an experimental B-235 might get re-engine with a BMW801 they "just happened" to have laying around?

Offline perttime

  • The man has produced a Finnish Napier Heston Fighter...need we say more?
Re: Avia B-35
« Reply #2 on: July 10, 2015, 02:20:27 PM »
I'm a fan of B-35/135. Do you have B-435 profiles coming?

I think the B-35 with skis needs streamlined skis like on Finnish Fokker D.XXI.

Maybe some were delivered to Finland too, as Hispano-Suiza engines were in use on other types already. Conversion to captured Klimov M-105 engines is a possibility too, like on Finnish Morane-Saulnier M.S.406.

Offline darkfold

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Re: Avia B-35
« Reply #3 on: July 10, 2015, 06:33:26 PM »
I like that evolution.  Any chance an experimental B-235 might get re-engine with a BMW801 they "just happened" to have laying around?

I don't think that this opinion is real. BMW-801 in all versions is more than twice as heavier than Hispanio Suiza 12 or  Pratt & Whitney R-1830-90:

Dry weights:

Hispanio-Suiza 12Y-38 - 515kg
Pratt & Whitney R-1830-90 - 567kg
BMW-801 - 1012kg

And this load would require complete new, strongest and heavier fuselage, adapted wings,...and I think that construction of new plane will be cheaper and easier than the adaptation of the original structure. Not to mention the fact that BMW-801 has been available only since 1939 (too late for purely Czechoslovak construction) and practically from the beginning used for the Ju-88 and Fw-190 for which was dismissed B-435 for Luftwaffe (rightfully so, Fw-190 was much better, more mature and perspective design). For these non-priority projects (including B-35, in this category was for Luftwaffe priority in Bf-109 and later in Fw-190 which were developed and designed directly under requirements of RLM) were used captured engines and technologies from occupied countries, not priority engines as DB601 or BMW801 (in 1940 during the tests of prototypes of real B-35 was discussed possibility of mounting the DB601 engine instead of the original HS 12Ycrs - rejected by RLM by a decision of unreleased DB601 for this purposes). So that more realistic opinion is any French radial engine but question is if this replacement will increase or decrease performancies of plane.

I'm a fan of B-35/135. Do you have B-435 profiles coming?

I think the B-35 with skis needs streamlined skis like on Finnish Fokker D.XXI.

Maybe some were delivered to Finland too, as Hispano-Suiza engines were in use on other types already. Conversion to captured Klimov M-105 engines is a possibility too, like on Finnish Morane-Saulnier M.S.406.

Sorry, I forgot them, upload next week after return to Prague.

Used skies are same system used and tested in Avia B-534. I think that using of streamlined finnish-like skis is not problem if you create new fairing of legs and new suspension.

I don’t think that reconstruction of B-35 for M-105 is reasonable. M-105 is derived from HS 12Y and its performances are fully comparable with HS 12Y-1000 which is installed in B-135 and B-435 (but can't be changed piece for piece). If we want to grant better performance for Finnland, right way is adapted B-235 fuselage for R-1830 engines license build in France (used in LeO 453 and Curtiss Hawk) and winterize it for use in Finnland (including improvements used in B-435).

Offline apophenia

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Re: Avia B-35
« Reply #4 on: July 11, 2015, 04:47:16 AM »
Great stuff! Looking forward to seeing the B-435/Av-435  :)
Froglord: "... amphibious doom descends ... approach the alter and swear your allegiance to the swamp."

Offline lauhof52

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Re: Avia B-35
« Reply #5 on: July 11, 2015, 02:09:49 PM »
Very nice work!

Offline Tophe

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Re: Avia B-35
« Reply #6 on: July 18, 2015, 06:57:37 AM »
Any chance of an Avia Zwilling like single-seat Twin-Mustang? ;)

Offline darkfold

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Re: Avia B-35
« Reply #7 on: July 20, 2015, 08:25:44 PM »
Here is promised B-435/Av-435. A lot of work last week...

Offline Logan Hartke

  • High priest in the black arts of profiling...
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Re: Avia B-35
« Reply #8 on: July 20, 2015, 08:33:01 PM »
Those look lovely, darkfold. Very nice.

Cheers,

Logan

Offline apophenia

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Re: Avia B-35
« Reply #9 on: July 23, 2015, 06:20:36 AM »
Indeed it does!
Froglord: "... amphibious doom descends ... approach the alter and swear your allegiance to the swamp."