Modelling > 1920s/1930s GB or Between the Wars GB

Progress at Poland's PZL

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apophenia:
In the mid-1930s, the Polish Air Force (Siły Powietrzne) contracted state aircraft firm PZL to produce a replacement for its in-service PZL P.11 gull-winged fighters. The task was assigned to engineer Wsiewołod Jakimiuk whose team sketched out a low-winged monoplane with enclosed-cockpit. This design emerged as the PZL.50 Jastrząb (Hawk). However, by the Summer of 1937, it was decided that progress on the PZL.50 was too slow. 'Jaki' was ordered focus his team's attention on a quicker-to-produce, low-winged derivative of the production-model P.11c fighter. This concept would originally be known as the Dolnopłat Myśliwski Jakimiuka (DMJ).

With speed the priority, Jakimiuk chose to adopt the wing structure designed for the twin-engined PZL.38 Wilk. [1] Stripped of its nacelles, this wing was simplified and modified to fit the base P.11 fuselage structure. To further speed development, a fixed undercarriage was adopted. The main wheels were to be clad in streamlined spats akin to those on the P.23 Karaś attack aircraft. Much of the engineering work was performed using a slightly damaged P.11c airframe to create what was effectively a 'flying mock-up' of the new fighter. Although the fuselage had to be slightly lengthened, other than an inserted extension frame it remained unchanged. That allowed what became the P.11d ( 'd' for dolnopłat or low-wing) to be completed very quickly.  By October 1937, the prototype P.11d was undergoing service trials with Siły Powietrzne personnel at Warsaw-Okecie airfield.

Top Prototype conversion PZL P.11d on service trials, Warsaw-Okęcie, Autumn 1937. Note windscreen retained from the P.11c and full main undercarriage leg spats. Just visible are the leading-edge slats - unique to this prototype.

While service trials were underway, a pre-production batch was approved under the new designation PZL.31a. [3] These aircraft were all to be based upon selected P.11c airframes returned from service use. Fortunately, only minor detail differences had to be incorporated into the design based on the Warsaw-Okęcie trials. By the late Summer of 1938, the first PZL.31a fighters were entering service with the 123 Eskadra Mysliwska (123 Fighter Squadron) at Poniatów near Warsaw. The PZL.31 was dubbed Krogulec (Sparrowhawk) in service.

Bottom One of the first PZL PZL.31a Krogulecs delivered to the 123 Eskadra Mysliwska, displacing older, gull-winged P.7a fighters. In late December 1938, 123.EM Commanding Officer Capt. Mieczyslaw Olszewski ground-looped 'White 3' at Poniatów. The airframe was repaired but did not return to the 123 Eskadra Mysliwska.

An obvious change for these pre-production fighters was their larger, broaden windscreen (taken from the export P.24). [4] Note too that the spats have been removed (to avoid the buildup of mud and other debris which could jam the wheels).

(To be continued ...)

__________________________________

[1] Work on this wing design had begun back in 1934 for the multi-purpose aircraft which predated the Wilk.

[2] Low-wing Monoplane = Dolnopłat as opposed to Górnopłat (or high-wing monoplane) also known as the płatem polskim or Polish wing.

[3] There is no explanation for this 'retrograde' designation. The PZL-31 designation had previously been assigned to a since-abandoned bomber concept.

[4] Although the P.24s hinged canopy and raised rear decking was not adopted for the PZL.31a conversions.

Old Wombat:

--- Quote from: apophenia on July 23, 2021, 11:40:52 AM ---An obvious change for these pre-production fighters was their larger, broaden windscreen (taken from the export P.24). [4] Note too that the spats have been removed (to avoid the buildup of mud and other debris which could jam the wheels).

(To be continued ...)

--- End quote ---

Brian would be appalled! :o

Robomog:
Absolutly !   ;)

  Mog
>^-.-^<

GTX_Admin:
 :smiley:

apophenia:

--- Quote from: Old Wombat on July 23, 2021, 03:26:47 PM ---Brian would be appalled! :o

--- End quote ---

He would  :-[

Additional votive offerings have already been laid at the alter of St. Brian of Bash ... 'cuz the PZL spat situation is about to become even more dire   :o

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