View source for Potez 39

{|{{Infobox aircraft begin
 |name = Potez 39
 |image = Potez 39.jpg
 |caption =
}}{{Infobox aircraft type
 |type = Observation
 |manufacturer = [[Potez]]
 |designer =
 |first flight = January 1930
 |introduced = 1934
 |retired = 1940
 |status =
 |primary user = [[French Air Force]]
 |more users = [[Peruvian Air Force]]
 |produced =
 |number built = 112 plus prototypes
 |unit cost =
 |variants with their own articles =
}}
|}

The '''Potez 39''' was a twin-seat single-engined [[parasol wing]] monoplane [[aerial reconnaissance]] and observation aircraft designed and produced by the French aircraft manufacturer [[Potez]]. It was the company's first all-metal aircraft.

It was developed in response to a specification released in 1928 for a new reconnaissance aircraft to succeed the [[Potez 25]] and [[Breguet 19]]. The design team performed a detailed study of both mixed-construction and metal-centric aircraft prior to designing the all-metal Potez 39; numerous prototype and derivative aircraft were conceived of by Potez, including that of a [[floatplane]], however, besides the [[French Air Force]], only [[Peru]] would opt to order the type.

The new aircraft, which performed its [[maiden flight]] in January 1930, came as the runner up to the [[Breguet 27]], but was still selected for production. While the Potez 39 was still in service with seven observation squadrons at the outbreak of the [[Second World War]], the French Air Force elected to rapidly withdraw the type from frontline service and instead use it as a trainer aircraft up until the [[Armistice with France (Second Compiègne)|armistice of June 1940]], after which point the remaining aircraft were scrapped.

==Development==
The Potez 39 was designed to a fulfil a requirement issued during 1928 for an aircraft to replace both the [[Potez 25]] and [[Breguet 19]] aircraft then in service with the [[French Air Force]] in the A2 (''Artillerie Biplace'' - two seat observation aircraft) role. One key feature that was stipulated by the specification was the use of the [[Hispano-Suiza 12H]] engine, which was capable of producing up to {{convert|580|bhp|kW|abbr=on}}.<ref name="Passingham p42-3"/><ref name="Breffort en p62"/>

In response, the company's design team produced a new aircraft along the same basic lines as the earlier [[Potez 25]]; however, unlike its predecessor, it featured all-metal construction instead the traditional mixed-construction practices that had been long used by the company.<ref name = "naca 1"/> Development of what would become the Potez 39 was heavily shaped by a period of methodical study conducted at [[Méaulte]] under the direction of the [[aeronautical engineer]] Louis Coroller; this was initially carried out on conventional monoplanes before progressing to metal aircraft that were adapted for quantity production.<ref name = "naca 7">NACA 1930, p. 7.</ref>

During January 1930, the prototype conducted its [[maiden flight]]. Although the [[Breguet 27]] was selected as the winner of the competition, both it and the Potez, which was the runner-up, were chosen for production.<ref name="Passingham p42-3"/> Compared to the Potez 25, of which over 2,000 were ordered, production of the Potez 39 series was on a smaller scale. A total of 100 Potez 390 aircraft were built for France while 12 Potez 391 aircraft, powered by a [[Lorraine-Dietrich 12H]] engine capable of generating up to 700&nbsp;bhp, were produced to the [[Peruvian Air Force]]. A number of prototype and development aircraft, including a [[floatplane]], underwent flight testing, however, no further orders were received.

==Design==
The Potez 39 was a dedicated aerial reconnaissance aircraft that featured all-metal construction, which included the coverings of both the fuselage and wings.<ref name = "naca 1">NACA 1930, p. 1.</ref> The aircraft had an oval-section fuselage that was formed out of two areas, the fuselage proper and the engine support.<ref name = "naca 4"/> The latter, which was composed of [[duralumin]] sheeting, was attached to the fuselage proper via four spherical fittings that were bolted to the forward ends of the [[longeron]]s. The former was supported via a trellis girder arrangement, comprising varying thicknesses of duralumin, the uprights and diagonals of which were joined via simple riveted gussets to the longerons.<ref name = "naca 4"/> Key attachment gussets were composed of high-resistance [[steel]] that greatly hindered the development of [[corrosion]]. The duralumin fuselage covering was directly secured to all primary structural members, providing great rigidity to the overall assembly; the fuselage was considered to be relatively strong for the era.<ref name = "naca 4"/>

The exterior of the aircraft was covered by sheets of duralumin were used of a typical thickness of .35 mm (0.014 in.); this covering was stiffened using corrugated sections at intervals of 85 mm (3.35 in.), which had a height of about 10 mm (0.4 in.). Extensive testing was performed by Potez to determine that these proportions provided sufficient rigidity without overly increasing friction.<ref name = "naca 3"/> The covering of the wing had numerous removable sections, both to permit inspection as well as to assist in repairs and maintenance, while the central section of the wing was attached via a [[rivet]]s to the flanges of the [[Spar (aeronautics)|spar]]s, [[rib]]s, and cross pieces to constitute a rigid [[box girder]] that transmitted and shared stresses.<ref name = "naca 3">NACA 1930, p. 3.</ref> These spars comprised a duralumin web and four steel corrugated angles for stiffening, the latter being relatively easy to uniformly construct, as well as being relatively resistant to [[rust]]ing and vibrations alike. Both weight and construction time were minimised via the minimisation of both joints and riveting.<ref name = "naca 2">NACA 1930, p. 2.</ref>

The Potez 39 had a [[parasol wing]], the basic form of which was of an elongated rectangle with well-rounded tips, a feature which reportedly obtained the maximum achievable efficiency without resorting to a more complex wing design that incorporated multiple decreasing profiles.<ref name = "naca 1"/> The flying performance of such a profile was thoroughly explored during comparative flight tests with both the [[Potez 31]] and [[Potez 36]]. Lacking both [[Dihedral (aeronautics)|dihedral]] or [[swept wing|sweepback]], the wing has an aspect ratio of 7.3.<ref name = "naca 1"/> It was attached to the fuselage via an inverted V-shaped [[Bracing_(aeronautics)#Cabane_struts|cabane strut]] along with a pair of struts of which the threaded ends permitted adjustment; cross-bracing via means of struts made the aircraft incapable of becoming out of adjustment. The internal structure of the wing comprised two spars with diagonal bracing (using duralumin half-tubes) and widely spaced ribs.<ref name = "naca 12">NACA 1930, pp. 1-2.</ref> The wing was equipped with sizable [[aileron]]s.<ref name = "naca 4">NACA 1930, p. 4.</ref>

It was operated by a crew of two, a pilot and observer, that sat in tandem in open cockpits.<ref name = "naca 4"/> The observer was armed with two [[Lewis gun]]s on a ring mounting while the pilot was armed with a single [[synchronization gear|synchronised]] [[Darne machine gun]]. Additional armaments comprised light [[bomb]]s, which could be carried internally in a compact [[bomb bay]] as well as on external racks. Reconnaissance apparatus included a fixed camera that operated through a hatch in the fuselage floor.<ref name="Passingham p42-3">{{harvnb|Passingham|1996|pp=42–43}}</ref><ref name="Breffort en p62">{{harvnb|Breffort|Jouineau|2005a|p=62}}</ref>

The aircraft was powered by a single [[Hispano 12H]], which produced 579 hp at 2,000 [[rpm]].<ref name = "naca 5"/> Cooling was provided by both an water radiator and an oil radiator. Two pumps were used to deliver fuel to the engine from a suspended conical-shaped fuel tank, which permitted fuel dumping even in the event of deformation due to battle damage.<ref name = "naca 56">NACA 1930, pp. 5-6.</ref> The fuel dumping mechanical was relatively simple, being stylised on that of a [[firearm]].<ref name = "naca 6">NACA 1930, p. 6.</ref> The aircraft was equipped with a [[conventional landing gear|conventional undercarriage]].<ref name = "naca 5"/> The main undercarriage, which had a track gauge of 3 m (9.84 ft.) and was furnished with wheel brakes, was of an axleless design that incorporated Potez's own elastic struts. The tail skid could be was easily inspected via a removable plate near the tail.<ref name = "naca 45">NACA 1930, pp. 4-5.</ref>

The tail unit of Potez 39 was directly attached to the sternpost, which was in turn carried by the aftermost frame of the fuselage frame; the rear of this sternpost supported the hinges of the unbalanced [[rudder]] while the front received the [[fin]].<ref name = "naca 5">NACA 1930, p. 5.</ref> The rear of the [[Stabilizer (aeronautics)|stabiliser]] was attached to a movable support that permitted mid-flight adjustments with relatively little force via an arrangement of flexible joints and [[ball bearing]]s. The [[Elevator (aeronautics)|elevator]], which was positioned in front of the rudder, was unbalanced, slightly tapered, and had well-rounded tips; its structure was akin to that of the wing as well as covered by duralumin.<ref name = "naca 5"/>

==Operational history==
Deliveries to the French Air Force began in August 1933 and continued until April 1935.{{sfn|Ledet|Coroller|2005|p=27}} The Potez 39 joined the French Air Force's ''Groupes d'Observation'' (GO), but from 1936, it was replaced in the GOs by more modern types, including the [[ANF Les Mureaux 117]], [[Amiot 143]] and [[Potez 540]] aircraft, with the Potez 39s transferred to second-line ''Groupes Aériens Régionaux'' (GAR), which had the principal role of training reservists.{{sfn|Ledet|Coroller|2005|p=27}}<ref name="Breffort en p62"/> In 1938, the GARs were redesignated ''Groupes Aériens d'Observation'' (GAO).{{sfn|Ledet|Coroller|2005|p=28}} In August 1938, during the [[Munich Crisis]],General [[Joseph Vuillemin]], Chief of Staff of the French Air Force, gave orders that, in the event of war breaking out, obsolescent observation aircraft such as the Potez 39 should never cross the front line.{{sfn|Passingham|1996|p=45}} At the outbreak of the [[Second World War]], the Potez 39 was in service with seven GAOs, which despite their age and Vuillemin's 1938 instructions, were deployed on operational missions.{{sfn|Ledet|Coroller|2005|p=33}}{{sfn|Passingham|1996|p=45}} The Potez 39 proved to be vulnerable to German fighters, however,{{sfn|Ledet|Coroller|2005|p=33}} and in October 1939, the units equipped with the Potez 39 and the equally outdated Breguet 27, were withdrawn from use at the front.<ref name="Breffort en p62"/>{{sfn|Breffort|Jouineau|2004|p=56}} The Potez 39 continued to be used for liaison and casualty evacuation duties until the [[Battle of France]] concluded with the [[Armistice with France (Second Compiègne)|armistice of June 1940]], at which point 41 aircraft reportedly remained in [[Metropolitan France]].{{sfn|Ledet|Coroller|2005|pp=35, 38}} These aircraft were deemed to be obsolete and thus were scrapped shortly thereafter.

Twelve [[Lorraine Pétrel]]-powered Potez 391s were purchased by Peru in 1933, during the [[Colombia–Peru War|Leticia War]] with [[Colombia]], with the purchase being funded by popular subscription, but they only entered service early in 1935, after the war had ended.{{sfn|Coroller|Ledet|2005|pp=48–49}} The outbreak of the Second World War stopped deliveries of spare parts and technical assistance from France, and the type was phased out from active service.{{sfn|Coroller|Ledet|2005|p= 50}}

==Variants==
[[File:Potez_391_photo_L'Aerophile_November_1934.jpg|thumb|Potez 391 photo from L'Aerophile November 1934]]

;Potez 37
:Two seat reconnaissance aircraft developed in parallel with Potez 39, with narrow tail boom replacing conventional rear fuselage. Unsuccessful, with only three built, the [[ANF Les Mureaux 113|ANF-Les Mureaux 110]] being preferred.<ref name="Breffort en p62"/><ref name="Passingham p47">{{harvnb|Passingham|1996|p=47}}</ref>
;Potez 390 A2
: Two-seat observation aircraft for French Air Force. Powered by a [[Hispano-Suiza 12Hb]] engine.
;Potez 39 Hy
:Experimental floatplane version.<ref name="Passingham p47"/>
;Potez 391
:Variant of Potez 39 powered by {{convert|520|hp|kW|abbr=on|order=flip}} [[Lorraine-Dietrich 12H]]. 12 production versions built for Peru.<ref name="Passingham p47"/>
;Potez 3910 R2
:Experimental aircraft with {{convert|860|hp|kW|abbr=on|order=flip}} [[Hispano-Suiza 12Ybrs]] engine. One built.<ref name="Passingham p47"/>
;Potez 3912
:Experimental aircraft with {{convert|540|hp|kW|abbr=on|order=flip}} [[Renault 12 Jc]] engine. One built.<ref name="Passingham p47"/>
;Potez 392:A single prototype initially built with a {{convert|510|hp|kW|abbr=on|order=flip}} [[Hispano-Suiza 12Kb]], later re-engined with a {{convert|680|hp|kW|abbr=on|order=flip}} [[Hispano-Suiza 12Xbr]]
;Potez 393:A single prototype powered by a {{convert|700|hp|kW|abbr=on|order=flip}} [[Hispano-Suiza 12Ybr]][[File:Potez_49_L'Aerophile_December_1932.jpg|thumb|Potez 49 photo from L'Aerophile December 1932]]
;Potez 49
:[[Sesquiplane]] conversion of Potez 39. The lower wing was designed to be easily removable, so the aircraft could be configured either as a [[monoplane]] or a [[biplane]], according to mission. One built.<ref name="Passingham p47"/><ref name=Flight241132>{{cite magazine |date = 24 November 1932  |title = Paris Aero Show |magazine = [[Flight International|Flight]] |volume = XXIV |issue = 48 |page = 1111 |url = http://www.flightglobal.com/pdfarchive/view/1932/1932%20-%201189.html }}</ref>

==Operators==
;{{FRA}}
* [[French Air Force]]
;{{PER}}
* [[Peruvian Air Force]]
;{{USSR}}
* [[Soviet Air Force]] - One aircraft, used for tests and trials.

==Specifications==
[[File:Potez_39_3-view_NACA_Aircraft_Circular_No.114.jpg|thumb|Potez 39 3-view drawing from NACA Aircraft Circular No.114]]

{{Aircraft specs
|ref= ''L'Aviation française de 1939 à 1942, Tome 2''<ref name="Breffortfr">{{harvnb|Breffort|Jouineau|2005b|p=62}}</ref>
|prime units?= met
<!--
        General characteristics
-->
|crew= 2
|length m= 10
|length note=
|span m= 16
|span note=
|height m= 3.4
|height note=
|wing area sqft= 377
|wing area note=
|aspect ratio=<!-- sailplanes -->
|airfoil=
|empty weight kg= 1,492
|empty weight note=
|gross weight kg= 2,250
|gross weight note=
|max takeoff weight kg=
|max takeoff weight note=
|fuel capacity=
|more general=
<!--
        Powerplant
-->
|eng1 number= 1
|eng1 name= [[Hispano-Suiza 12H]]
|eng1 type= V-12 water-cooled piston engine
|eng1 kw= 433
|eng1 note=

|prop blade number= 2
|prop name= fixed-pitch propeller
|prop dia m=<!-- propeller aircraft -->
|prop dia note=
<!--
        Performance
-->
|max speed kmh= 249
|max speed note= at {{cvt|3500|m|0}}
|cruise speed kmh=
|cruise speed note=
|stall speed kmh=
|stall speed note=
|never exceed speed kmh=
|never exceed speed note=
|range km= 800
|range note=
|combat range km=
|combat range note=
|ferry range km=
|ferry range note=
|endurance=<!-- if range unknown -->
|ceiling m= 7,000
|ceiling note=
|g limits=<!-- aerobatic -->
|roll rate=<!-- aerobatic -->
|climb rate ms=
|climb rate note=
|time to altitude= {{cvt|3500|m|0}} in nine minutes
|wing loading kg/m2=
|wing loading note=
|disk loading kg/m2=
|disk loading note=
|fuel consumption kg/km=
|power/mass=
|thrust/weight=
|more performance=
<!--
        Armament
-->
|guns=<br/>
**1 x 7.7 mm machine-gun firing forward, fixed
**2 x 7.7 mm machine-guns in observer's position, flexible
|bombs=up to {{convert|120|kg|lb|abbr=on}}
}}

==See also==
{{aircontent
|see also=
|related=<!-- related developments -->
|sequence=
|similar aircraft=<!-- similar or comparable aircraft -->
|lists=<!-- related lists -->
* [[List of Interwar military aircraft]]
}}

==References==
===Citations===
{{Reflist}}

===Bibliography===
{{Commons category|Potez 39}}
* [https://ntrs.nasa.gov/citations/19930090254 "The "Potez 39" observation airplane (French) : an all-metal high-wing two-seat monoplane."] ''[[National Advisory Committee for Aeronautics]]'', 1 April 1930. NACA-AC-114, 93R19544.
* {{cite book |last1 = Breffort |first1 = Dominique |last2 = Jouineau |first2 = André |title = French aircraft 1939-1942: Volume One: From Amiot to Curtiss |date = 2004 |publisher = Histoire & Collections |location = Paris, France |isbn = 2-915239-23-1 |language = en}}
* {{cite book |last1 = Breffort |first1 = Dominique |last2 = Jouineau |first2 = André |title = French aircraft 1939-1942: Volume Two: From Dewoitine to Potez |date = 2005a |publisher = Histoire & Collections |location = Paris, France |isbn = 2-915239-49-5 |language = en}}
* {{cite book |last1 = Breffort |first1 = Dominique |last2 = Jouineau |first2 = André |title = L'aviation française de 1939 à 1942: chasse, bombardement, reconnaissance et observation. Tome 2, De Dewoitine à Potez |date = 2005b |publisher = Histoire & collections |location = Paris |isbn = 2-915239-48-7 |language = fr }}
* {{cite magazine |last1=Coroller |first1=Jean-Louis |last2=Cortet |first2=Pierre |title=Un "Classique" Français": Le Potez 39 |magazine=Avions |date=March–April 2005 |issue=144 |pages=20–37 |language=fr}}
* {{cite magazine |last1=Coroller |first1=Jean-Louis |last2=Ledet |first2=Michel|title=Un "Classique" Français": Le Potez 39 (3) |magazine=Avions |date=July–August 2005 |issue=146 |pages=48–52 |language=fr}}
* {{cite magazine |last1=Ledet |first2=Michel |last2=Coroller |first1=Jean-Louis |title=Un "Classique" Français": Le Potez 39 (2)|magazine=Avions |date=May–June 2005 |issue=145 |pages=26–38 |language=fr}}
* {{cite magazine |last1 = Passingham |first1 = Malcolm |title = Overtaken by Events: The Potez 39 Family |magazine = Air Enthusiast  |location = Stamford, UK |publisher = Key Publishing |issue = 64 |date = July–August 1996 |pages = 42–47 |issn = 0143-5450}}


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[[Category:1930s French military reconnaissance aircraft|Potez 039]]
[[Category:Potez aircraft|039]]
[[Category:Parasol-wing aircraft]]
[[Category:Single-engined tractor aircraft]]
[[Category:Aircraft first flown in 1930]]
[[Category:Aircraft with fixed conventional landing gear]]