View source for PZL.46 Sum

{{Short description|Polish war plane}}
{{more footnotes needed|date=May 2012}}
{{Infobox aircraft
| name = PZL.46 Sum
| image = PZL.46 Sum I prototype.jpg
| caption = First prototype of the PZL.46
| type = [[Light bomber]] and [[reconnaissance]] aircraft
| manufacturer = [[Państwowe Zakłady Lotnicze]]
| designer = 
| first_flight = August [[1938 in aviation|1938]]
| introduction = 
| retired = 
| primary_user = [[Polish Air Force|Polish Military Aviation]]
| produced = [[1939 in aviation|1939]]
| number_built = 2 prototypes
| unit cost = 
| variants = 
}}
'''PZL.46 Sum''' (''[[Wels catfish|sheatfish]]'') was a [[light bomber]] developed by [[Państwowe Zakłady Lotnicze]] shortly before [[World War II]], which,
was directed to serial production in the spring of 1939. These planes were in production, but the Polish industry did not manage to produce them before the outbreak of the war.<ref>{{Cite web|url=http://www.samolotypolskie.pl/samoloty/2314/84/PZL-46|title = Samolotypolskie.pl - PZL-46 "Sum"}}</ref>

==Design and development==
The PZL.46 Sum was designed by [[Stanisław Prauss]] in the [[Państwowe Zakłady Lotnicze|PZL]] works as a successor to the standard Polish light bomber and reconnaissance plane, the [[PZL.23 Karaś]], also of Prauss' design.  First sketches were made in 1936.  In order to test new features, like double tail fins and a retractable underbelly [[Bombardier (air force)|bombardier]] gondola, a single modified PZL.23, designated PZL.42 was built and tested in 1936.

The first prototype of PZL.46 Sum flew in August [[1938 in aviation|1938]].  It shared only a general composition with PZL.23, its fuselage was much more aerodynamically refined and its wings had thinner profile.  Initially it was intended to use retractable landing gear, but since the Polish industry did not produce retractable landing gear, a fixed one was used.  In November–December 1938 the prototype was shown at the [[Paris Air Show]].  In May 1939 the second similar prototype was flown (PZL.46/II).

Tests proved, that the Sum was a successful design, with much better performance, than PZL.23.  The only major faults were with a mechanism of retracting of the underbelly gondola (the gondola for a bombardier, with a machine gun at the rear, was a feature copied from PZL.23, where it was a fixed one.  It was a rare feature in light bombers' construction and its usefulness was questionable, as it reduced performance).

In March 1939 the PZL.46 was ordered for a serial production.  The Polish Air Force planned to buy 160 aircraft of the '''PZL.46A''' variant. The first aircraft were to be completed in autumn 1939 and delivered in early 1940.  Only some parts were produced by the German [[Invasion of Poland (1939)|invasion of Poland]] in September 1939.<ref>{{Cite web|url=http://www.samolotypolskie.pl/samoloty/2314/84/PZL-46|title = Samolotypolskie.pl - PZL-46 "Sum"}}</ref>

The third prototype was in construction in the summer of 1939, it was to be an export variant PZL.46B, powered with [[Gnome-Rhône 14N]]21 engine.  Bulgaria, using [[PZL.43]] bombers, showed an interest in the new design and made a preliminary order for 12 aircraft, uncompleted due to war.

Stanisław Prauss made also a preliminary design of smaller development variant PZL Łosoś, which was to be a two-seater dive  bomber with {{cvt|1600|hp|kW}} [[Hispano-Suiza 12Z]] inline engine and retractable landing gear, without underbelly gondola.

=== Technical description ===
The aircraft was conventional in layout, mid-wing all-metal cantilever [[monoplane]], metal-covered.  The fuselage was semi-[[monocoque]], oval in cross-section. Double tail fins.  The crew consisted of three: pilot, observer/bombardier and rear gunner.  The bombardier's combat station was in a gondola underneath the fuselage, where he also operated an underbelly [[machine gun]].  The gondola could be retracted into the fuselage to decrease drag. 
The fixed undercarriage had aerodynamic teardrop covers. Radial engine, PZL-built 840&nbsp;hp Bristol Pegasus (PZL Pegaz) XXB (maximum power 940&nbsp;hp), in a NACA-style cowling.  Three-blade metal propeller Hamilton Standard. Fuel tanks: 750 L in a central wing section.

==Operational history==
During [[World War II]], the first prototype was left in Warsaw, because of a landing gear damage.  On 5 September 1939 the second prototype was evacuated from Warsaw to [[Lwów]], then on 17 September to [[Bucharest]] in Romania, where it was interned.  On 26 September 1939, under pretext of delivering the plane to IAR factory in Brasov, it was flown by Riess with other three crewmen (including [[Witold Urbanowicz]]) from Romania to besieged Warsaw.  The crew delivered orders from the Polish commander in chief marshal [[Edward Rydz-Śmigły]] for the commander of Warsaw defence [[Juliusz Rómmel]].  On 27 September 1939, with most of the Polish territory occupied by Germans and Soviets, it flew to [[Kaunas]] in [[Lithuania]].  The plane was interned and left there and later captured there and tested by the Soviets.

==Variants==
;PZL.46/I
:First prototype.
;PZL.46/II
:Second prototype.
;PZL.46A
:Main production version, 160 ordered for Polish Military Aviation, none delivered.
;PZL.46B
:Export version powered [[Gnome-Rhône 14N|Gnome-Rhône 14N21]] engine.

==Operators==
;{{BUL}}
*[[Bulgarian Air Force]] preliminarily ordered 12 aircraft, none delivered.
;{{POL}}
*[[Polish Air Force|Polish Military Aviation]]
;{{USSR}}
*[[Soviet Air Force]] operated one captured prototype for evaluation.

== Specifications (PZL.46/I)==
[[File:PZL-46 Sum.svg|300px|right]]

{{Aircraft specs
|ref=<ref name=cynk>{{cite book |last1=Cynk |first1=Jerzy B |title=Polish aircraft 1893-1939 |publisher=Putnam |date=1971 |isbn=0-370-00085-4 |pages=[https://archive.org/details/polishaircraft1800cynk/page/254 254-258] |url=https://archive.org/details/polishaircraft1800cynk/page/254 }}</ref>
|prime units?=met
<!--
        General characteristics
-->
|crew=3
|length m=10.5
|length note=
|span m=14.6
|span note=
|height m=3.3
|height note=
|wing area sqm=27
|wing area note=
|aspect ratio=<!-- sailplanes -->
|airfoil=
|empty weight kg=1995
|empty weight note=
|gross weight kg=3550
|gross weight note=
|max takeoff weight kg=
|max takeoff weight note=
|fuel capacity=
|more general=
<!--
        Powerplant
-->
|eng1 number=1
|eng1 name=[[Bristol Pegasus|PZL Pegaz XXB]]
|eng1 type=9-cylinder air-cooled radial piston engine
|eng1 hp=918
|eng1 note=maximum power (short duration) '''Sum A'''
::::{{cvt|1030|hp|0}} [[Gnome-Rhône 14N-21]] '''Sum B'''

|prop blade number=3
|prop name=Hamilton/PZL variable-pitch propeller
|prop dia m=<!-- propeller aircraft -->
|prop dia note=
<!--
        Performance
-->
|max speed kmh=425
|max speed note=at {{cvt|3600|m|0}} '''Sum A'''
::::{{cvt|350|km/h|mph kn}} at sea level '''Sum A'''
::::{{cvt|470|km/h|mph kn}} at {{cvt|4700|m|0}} '''Sum B'''
::::{{cvt|370|km/h|mph kn}} at sea level '''Sum B'''
|cruise speed kmh=
|cruise speed note=
|stall speed kmh=110
|stall speed note=
|never exceed speed kmh=
|never exceed speed note=
|range km=1300
|range note=
::::{{cvt|1100|km|mi nmi|0}} '''Sum B'''
|combat range km=
|combat range note=
|ferry range km=
|ferry range note=
|endurance=<!-- if range unknown -->
|ceiling m=7700
|ceiling note=
::::{{cvt|8600|m|0}} '''Sum B'''
|g limits=<!-- aerobatic -->
|roll rate=<!-- aerobatic -->
|climb rate ms=6
|climb rate note=
|time to altitude=
|wing loading kg/m2=131.1
|wing loading note=
|fuel consumption kg/km=
|power/mass={{cvt|0.119|hp/lb|order=flip}}
|more performance=<!--<br />
*'''Take-off run:''' {{cvt||m|0}}
*'''Take-off run to {{cvt|15|m|0}}:''' {{cvt||m|0}}
*'''Landing run:''' {{cvt||m|0}}
*'''Landing run from {{cvt|15|m|0}}:''' {{cvt||m|0}}-->
<!--
        Armament
-->
|guns= 8 x [[machine gun]]s:
:*2 x 7.92 mm [[karabin lotniczy uniwersalny wz. 36]] fixed in nose with synchronising gear;
:*2 x 7.92 mm karabin lotniczy uniwersalny wz. 36 fixed in wings;
:*2 x 7.92 mm [[karabin lotniczy obserwatora wz. 37]] in rear upper station (production planes were to have 2)
:*2 x 7.92 mm karabin lotniczy obserwatora wz. 37 in rear lower station;
|bombs= {{cvt|600|kg|0}} of bombs under wings.

|avionics=
}}

==See also==
{{aircontent
|related=
*[[PZL.23 Karaś]]

|similar aircraft=
*[[Heinkel He 70]]
*[[Fairey Battle]]
*[[A-35 Vengeance]]
*[[Mitsubishi Ki-30]]
*[[DAR-10]]

|lists=
}}

== References ==
{{reflist}}

* Andrzej Glass: "Polskie konstrukcje lotnicze 1893-1939" (''Polish aviation constructions 1893-1939''), WKiŁ, Warsaw 1977 (Polish language, no ISBN)

== External links ==
{{commons category|PZL.46 Sum}}
* [https://translate.google.com/translate?hl=en&sl=ru&u=http://www.airwar.ru/enc/bww2/pzl46.html&sa=X&oi=translate&resnum=8&ct=result&prev=/search%3Fq%3DPZL.23%2BKaras%26start%3D80%26hl%3Den%26ie%3DUTF-8%26sa%3DN  PZL-46 Sum with photos and drawings] (translated page from Ugolok Neba)

{{PZL aircraft}}

[[Category:1930s Polish bomber aircraft]]
[[Category:1930s Polish military reconnaissance aircraft]]
[[Category:PZL aircraft]]
[[Category:Single-engined tractor aircraft]]
[[Category:Mid-wing aircraft]]
[[Category:Aircraft first flown in 1938]]
[[Category:Aircraft with fixed conventional landing gear]]