SAB AB-20

{{Short description|1930s French bomber aircraft}}  {{Infobox aircraft | name = AB-21 | logo = | logo_size = | image = A.B.21.png | alt = | caption = SAB AB-21 | long_caption = | other_names = | aircraft_type = Heavy night bomber | aim = | outcome = | related = | national_origin = France | manufacturer = Société Aérienne Bordelaise (SAB) | design_group = | designer = | builder = | issuer = | status = | owners = | primary_user = | more_users = | service = | major_applications = | proposals = | prototypes = | number_built = 1 AB-20 + 1 AB-21 | construction_number = | civil_registration = | military_serial = | radio_code = | requirement = | aircraft_carried = | flights = | total_hours = | total_distance = | construction_date = | introduction = | retired = | first_flight = 15 January 1932 | initiated = | in_service = | last_flight = | expected = | developed_from = Dyle et Bacalan DB-70 | variants = | developed_into = | preservation = | fate = | predecessors = | successors = | concluded = }}

The '''SAB AB-20''' was a large four engine twin boom French bomber built in the early 1930s as a development of the Dyle et Bacalan DB-70 airliner. It featured a lifting body of thick airfoil section between the inner engines. It was later modified for the attack role; a second aircraft, the '''AB-21''', had different engines and cleaner aerodynamics but no more were built.

==Design== The SAB AB-20 was a four-engine night bomber development of the three-engine Dyle et Bacalan DB-70 airliner. The change of manufacturer's name was the result of the financial failure of Dyle et Bacalan in 1929, followed by its immediate reappearance as SAB, who took over DB-70 development. The latter was built around a thick, wide chord airfoil centre section which provided generous internal space for passengers. The engines were mounted on this structure as were twin fuselages to carry the tail. The outer wings were of normal thickness and chord, and the cockpit and undercarriage were also attached to the centre section. The generous intra-wing volume equally offered crew, fuel and bomb-room for military purposes. Initially the AB-20 was intended to have three engines like its predecessor, but during the design phase there was a military request for a bombardier's position and a gunner's cockpit in the nose, which required the removal of the centre engine and its replacement by two extra engines wing-mounted outboard of the centre section.<ref name="Flight1932"/>

Apart from the extra engines and the very different crew compartment, together with the removal of passenger accommodation, the AB-20 and DB-70 had much in common: the thick centre section and high-mounted outer wings, twin fuselages carrying a long horizontal stabilizer, and twin fins and rudders. Both aircraft had conventional undercarriages with pairs of mainwheels widely separated on V-struts attached to the lower longerons of the centre section.<ref name="Flight1932"/>

The new central crew pod was flat-sided and tapered forwards to a complicated cylindrical nose, formed by a simple lower part with an overhanging, windowed cabin for the navigator/bombardier and an open gunner's cockpit, fitted with a machine gun ring, directly above. The nose also carried a long, conical probe with fine extensions, possibly pressure sensors. Further aft there was an enclosed pilot's cabin. A second gunner was stationed rearwards, on top of the centre section and a third fired from a ventral turret.<ref name="Flight1932"/>

==Development== The first flight of the AB-20 was on 15 January 1932. The following year it was reported that it had been structurally modified for the attack role<ref name="Flight1933"/> and was returning to Villacoublay for tests. thumb|AB-20 in 1932 By early 1934 a much developed version, the '''AB-21''' had appeared. It had the newer V-12 Lorraine Petrel water-cooled engines and a tapered, filleted cantilever wing without the struts used on the AB-20 and DB-70. The undercarriage had also been cleaned up with streamlined legs and wheels in long cowlings. The nose was further complicated, retaining the upper, open gunner's position but now with double underhanging windowed positions, though the conical probe had gone.<ref name="Flight1934"/>

Trials of an airborne sideways-firing 75 mm gun were carried out with the AB-20 prototype modified as the '''AB-22'''. Firing trials were halted after damage was caused to the lower wing skin by blast from the gun muzzle.

==Variants== ;SAB AB-20 :A four-engined bomber derived from the three-engined Dyle et Bacalan DB-70, powered by four {{convert|493|hp|kW|abbr=on|0}} Lorraine 12Fb Courlis engines.<ref name="BP1"/> ;SAB AB-21<ref name="BP2"/> :Similar to the AB-20 and DB-70 but with cantilevered wings and powered by four {{convert|493|hp|kW|abbr=on|0}} Lorraine 12Ha Pétrel engines. ;SAB AB-22 :The sole prototype AB-20, with a crew of five, modified with a 75 mm gun firing sideways. Test firing took place at Cazaux in September 1934, but was terminated after five rounds had been fired due to structural damage to the lower wing skin.<ref name="BP3"/>

==Specifications (AB-21)== {{Aircraft specs |ref=<ref name="Flight1932"/><ref name=SGA>{{cite journal |journal=Revue de la Société Générale Aéronautique |title=Avions A.B 20 et A.B.21 |date=December 1932 |pages=114–115 |url=http://dev.museesafran.com/wp-content/uploads/2012/10/1350046441-autres-revues-(sga)-saf2012_0047441.pdf |accessdate=8 April 2015 |publisher=SGA |location=Argenteuil |language=fr |url-status=dead|archive-url=https://web.archive.org/web/20150927213728/http://dev.museesafran.com/wp-content/uploads/2012/10/1350046441-autres-revues-%28sga%29-saf2012_0047441.pdf |archive-date=27 September 2015 }}</ref> |prime units?=met  |genhide=

|height m=6.84 |height ft= |height in= |height note= |wing area sqm=201 |wing area sqft= |wing area note=including the central body area of {{convert|88|m2|abbr=on}} |aspect ratio= |airfoil= |empty weight kg=8450 |empty weight lb= |empty weight note= |gross weight kg=13250 |gross weight lb= |gross weight note= |max takeoff weight kg= |max takeoff weight lb= |max takeoff weight note= |fuel capacity={{convert|1295|kg|abbr=on}} in four tanks |lift kg= |lift lb= |lift note= |more general=  |eng1 number=4 |eng1 name=Lorraine 12Ha Pétrel |eng1 type=V-12 water-cooled piston engines |eng1 kw= |eng1 hp=500 |eng1 kn= |eng1 lbf= |eng1 note= |power original= |thrust original= |eng1 kn-ab= |eng1 lbf-ab=

|more power=

|max speed kmh=198 |max speed mph= |max speed kts= |max speed note=at sea level * {{convert|205|kph|kn+mph|abbr=on}} at {{convert|2000|m|abbr=on}} * {{convert|210|kph|kn+mph|abbr=on}} at {{convert|3500|m|abbr=on}} |max speed mach= |cruise speed kmh=175 |cruise speed mph= |cruise speed kts= |cruise speed note=to {{convert|185|kph|kn+mph|abbr=on}} |stall speed kmh= |stall speed mph= |stall speed kts= |stall speed note= |never exceed speed kmh= |never exceed speed mph= |never exceed speed kts= |never exceed speed note= |minimum control speed kmh= |minimum control speed mph= |minimum control speed kts= |minimum control speed note= |range km=1000 |range miles= |range nmi= |range note= |combat range km= |combat range miles= |combat range nmi= |combat range note= |ferry range km= |ferry range miles= |ferry range nmi= |ferry range note= |endurance= |ceiling m=5500 |ceiling ft= |ceiling note= |g limits= |roll rate= |climb rate ms= |climb rate ftmin= |climb rate note= |time to altitude= * {{convert|1000|m|abbr=on}} in 5 minutes * {{convert|2000|m|abbr=on}} in 11 minutes * {{convert|3000|m|abbr=on}} in 17 minutes * {{convert|4000|m|abbr=on}} in 25 minutes * {{convert|5000|m|abbr=on}} in 40 minutes |lift to drag= |wing loading kg/m2=67 |wing loading lb/sqft= |wing loading note=

|power/mass=0.11 kW/kg (0.0672 hp/lb)

|more performance= [all figures estimated]  |guns= 3x {{convert|7.7|mm|in|abbr=on|3}} Lewis machine guns |bombs= maximum load {{convert|2500|kg|abbr=on}} of bombs |rockets= |missiles=

|other armament=

|avionics= }}

==See also== {{aircontent |see also= |related= |sequence= |similar aircraft= |lists= *List of bomber aircraft *List of Interwar military aircraft }}

==References== <references>

<ref name="Flight1932">{{cite magazine |title=A new French Night Bomber|magazine= Flight|date=26 February 1932 |volume=XXIV |issue=1209 |page=170 |url= https://archive.org/details/Flight_International_Magazine_1932-02-26-pdf/page/n5/mode/2up |access-date=11 December 2022 }}</ref>

<ref name="Flight1933">{{cite magazine |title=Airisms from the Four Winds: French "attack" machines|magazine= Flight|date=30 November 1933 |volume=XXV |issue=1301|page=1202 |url=https://archive.org/details/Flight_International_Magazine_1933-11-30-pdf/page/n37/mode/2up |access-date=11 December 2022 }}</ref>

<ref name="Flight1934">{{cite magazine |title=New Aircraft: Where is the moat? |magazine= Flight|date=15 March 1934 |volume=XXVI |issue=1316 |page=253 |url= https://archive.org/details/Flight_International_Magazine_1934-03-15-pdf/page/n17/mode/2up |access-date=11 December 2022}}</ref>

<ref name="BP1">{{cite web|author=Bruno Parmentier |url=http://www.aviafrance.com/aviafrance1.php?ID=4968&ID_CONSTRUCTEUR=1127&ANNEE=0&ID_MISSION=0&MOTCLEF= |title=S.A.B. AB-20 - Bombardier lourd - Un siècle d'aviation française |publisher=Aviafrance.com |date=1998-08-30 |accessdate=2011-01-01}}</ref>

<ref name="BP2">{{cite web|author=Bruno Parmentier |url=http://www.aviafrance.com/aviafrance1.php?ID=4969&ID_CONSTRUCTEUR=1127&ANNEE=0&ID_MISSION=0&MOTCLEF= |title=S.A.B. AB-21 - Bombardier lourd - Un siècle d'aviation française |publisher=Aviafrance.com |date=1998-08-30 |accessdate=2011-01-01}}</ref>

<ref name="BP3">{{cite web|author=Bruno Parmentier |url=http://www.aviafrance.com/aviafrance1.php?ID=4970&ID_CONSTRUCTEUR=1127&ANNEE=0&ID_MISSION=0&MOTCLEF= |title=S.A.B. AB-22 - Expérimental - Un siècle d'aviation française |publisher=Aviafrance.com |date=1998-08-30 |accessdate=2011-01-01}}</ref>

</references>

==Bibliography== *{{cite journal |last1=Borget|first1=Michel|title=Les "Burnelli" français: le DB 70 et sa progeniture (2)|journal=Le Album de Fanatique de l'Aviation |date=March 1970|issue=9|pages=24–26|issn=0757-4169|language=fr|trans-title=The French "Burnelli"s: The DB 70 and Its Offspring, Part 2}} *{{cite journal |last1=Borget|first1=Michel|title=Les "Burnelli" français: progéniture du DB 70; l'AB 20 (3)|journal=Le Album de Fanatique de l'Aviation |date=April 1970|issue=10|pages=24–26|issn=0757-4169|language=fr|trans-title=The French "Burnelli"s: The Offspring of the DB 70, the AB 20, Part 3}} *{{cite journal |last1=Borget|first1=Michel|title=Les "Burnelli" français: le AB 20, AB 21 et AB 22... (4)|journal=Le Album de Fanatique de l'Aviation |date=May 1970|issue=11|pages=24–27|issn=0757-4169|language=fr|trans-title=The French "Burnelli"s: The AB 20, AB 21 and AB 22..., Part 4}}

==External links== {{Commons category}} *[https://books.google.com/books?id=QdsDAAAAMBAJ&dq=Popular+Science+1935+plane+%22Popular+Mechanics%22&pg=PA67 "The Next War In The Air" ''Popular Mechanics'', January 1936] photo bottom of pg 67 *{{YouTube|GbZmKMyGvnE SAB AB-20}} from ''Giornale Luce''

Category:1930s French military aircraft Category:Société Aérienne Bordelaise Category:Twin-boom aircraft Category:Four-engined tractor aircraft Category:Aircraft first flown in 1932 Category:Four-engined piston aircraft