Savoia-Marchetti S.73

The aircraft was developed in only four months, thanks to the use of the S.55 wing, combined with a much more conventional fuselage. Developed in parallel with a bomber version (the SM.81 Pipistrello) the prototype S.73 first flew on 4 June 1934 from Cameri, with Adriano Bacula as test pilot.Emilani & Cony 2000, pp. 25–26

The prototype had a four-blade wooden propeller on the central engine, and two-blade wooden propellers on each wing engine. Later all aircraft were fitted with three-blade metal propellers.

The S.73 was a mixed-construction (a skeleton of steel covered by wood and fabric for the fuselage, wood for the three-spar wing) monoplane with a braced tailplane and fixed undercarriage. There were two generators, one in each side of the fuselage; the batteries were 24 V and were rated at 90 A.

The pilot and co-pilot were seated side-by-side in an enclosed cockpit, with a compartment for a radio operator and a mechanic. A passenger compartment could house 18 passengers in two rows.

It had eight metallic fuel tanks, all in the wings, with a total capacity of {{convert|3950|L|USgal impgal|abbr=on}}. The prototype had French Gnome-Rhône 9Kfr Mistral engines, but further aircraft had {{convert|522|kW|abbr=on}} Piaggio Stella P.X, {{convert|574|kW|abbr=on}} Wright R-1820, {{convert|544|kW|abbr=on}} Walter Pegasus III MR2V, Alfa Romeo 125 or Alfa Romeo 126, driving ground adjustable, three-bladed, aluminium-steel propellers.

It could be used from small airports, had reliable handling and was not too costly. With the {{convert|574|kW|abbr=on}}Wright R-1820 engine the S.73 had cruise/max speeds of {{convert|270|/|340|kph|kn mph|abbr=on}}, {{convert|1000|km|abbr=on}} range, and {{convert|6300|m|abbr=on}} ceiling. With the {{convert|544|kW|abbr=on}} AR.126 the S.73 had a maximum speed of {{convert|345|kph|kn mph|abbr=on}}, {{convert|1000|km|abbr=on}} range, and {{convert|7000|m|abbr=on}} ceiling. The SABCA license-produced aircraft had {{convert|671|kW|abbr=on}} Gnome-Rhône 14K Mistral Major engines for a total of {{convert|2013|kW|abbr=on}}, comparable to the last models of S.79s or the CANT Z.1018.

The S.73 had an unremarkable flight test programme with few modifications recommended by the Regia Aeronautica. It was easy to fly, rugged, and easy to operate on the ground, including the ability to fly from short airfields in treacherous terrain, in spite of being under-powered and the lack of leading edge slats. Its mixed construction and fixed landing gear were its main shortcomings, when contemporary aircraft in the US and Germany were of all-metal construction with retractable undercarriages. Some of these had better performance, but the S.73 remained competitive for some years.

File:Sm 73.jpg airport]]

The first operator of the S.73 was the Belgian airline SABENA, which purchased five Gnome-Rhône 9Kfr Mistral Major-powered S.73s from Savoia-Marchetti in 1935, introducing them on European routes in the summer of 1935.Stroud 1966, pp. 444–445. Two of these aircraft were lost in accidents in 1935. Seven more S.73s, powered by Gnome-Rhône 14K Mistral Major engines, were built for SABENA under license by SABCA in 1936–1937, which allowed the S.73 to replace the Fokker F.VII on the service from Belgium to the Congo. This service took four days (with no overnight flying) with a flight time of 44 hours.Stroud 1966, p. 446.Wulf 1980, pp. 72–73.

The second operator of the S.73 was the Italian airline Ala Littoria, which received at least 21 examples, powered by a variety of engines, including the Piaggio Stella X, the Wright R-1820 and the Alfa Romeo 126 RC.10. They were used on services within Europe and to Italy's African empire. In December 1935, an S.73 was used for a journey from Italy to Asmara, delivering over 200,000 letters, with 6,600 km (4,100 mi) traveled in four days, followed by the return trip to Rome on 6 January 1936. A commercial line was established covering a 6,100 km (3,790 mi) journey.{{citation needed|date=February 2021}} Other users included Avio Linee Italiane (powered by Alfa Romeo 126) and Československé Státní Aerolinie (powered by Walter Pegasus).Stroud 1966, pp. 445–446.

At the outbreak of World War II the S.73 was already obsolete, but some of the aircraft were pressed into service with the Regia Aeronautica for operations in Abyssinia and Spain.

Nine S.73s were present in Eastern Africa and used as military transports.Shores 1994, p. 11. Owing to the poor military situation, with British Commonwealth forces on the brink of capturing Addis Ababa, the Duke of Aosta, the Viceroy of Italian East Africa, ordered the remaining three S.73s to be evacuated. After several days of preparation, they took off from Addis Ababa on 3 April 1941 with 36 men on board, planning to fly to Kufra in Libya, {{convert|2500|km|abbr=on}} away, requiring additional fuel tanks in the fuselage. All three aircraft force-landed in the desert, but refuelled at Jeddah, before resuming their journey.

After several days of difficulties, including sand storms that clogged up the air filters, they took off again. Initially, it was planned to make another landing in Beirut but in the meantime Erwin Rommel had conquered Benghazi, so this was the final destination of the three aircraft. Two aircraft, after 10 hours of flying and the men inside almost killed by fumes of the fuel auxiliary tanks, landed at Benghazi, after {{convert|4500|km|abbr=on}} and over a month of travel.

Seven Belgian S.73s were flown to the United Kingdom in May 1940 and were pressed into service by the Royal Air Force, and, operated by the SABENA flight crews, were used to fly ammunition to the British Expeditionary Force in Northern France. After two were destroyed by the Luftwaffe at Merville on 23 May, SABENA ordered its surviving aircraft, including the five S.73s, to move to France in preparation for transfer to the Belgian Congo. After the surrender of Belgium on 28 May the SABENA fleet was placed at the disposal of the French government and used to ferry pilots between the French mainland and French North Africa. Following France's surrender on 22 June 1940, the SABENA fleet, including the S.73s, was seized by Italy and operated by the Regia Aeronautica.Wulf 1980, pp. 73–75. The S.73s still in Italy were used to equip 605 and 606 Squadriglie. Four S.73s survived until the 1943 armistice, three being used by the Allies and one by the pro-Axis government; all had been taken out of service by the end of the war.

;7 November 1935:S.73P OO-AGM of SABENA was damaged beyond repair whilst taxiing at London-Croydon Airport.{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19351107-0|access-date=31 January 2017}}

;10 December 1935:

{{main|1935 SABENA Savoia-Marchetti S.73 crash}}

S.73 OO-AGN of SABENA crashed at Tatsfield, Surrey, United Kingdom with the loss of all eleven on board.{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19351210-0|access-date=31 January 2017}}

;26 January 1937:S.73P OO-AGR of SABENA crashed on approach to Oran Es Sénia Airport (ORN/DAOO), Algeria, with the loss of all 12 occupants (8 passengers and 4 crew).{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19370126-0|access-date=31 January 2017}}

;2 August 1937:S.73 I-SUSA of Ala Littoria crashed on approach to Wadi Halfa Airport (WHF/HSSW), Sudan, with the loss of all 9 occupants (6 passengers and 3 crew).{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19370802-0|access-date=31 January 2017}}

;30 April 1938:S.73 I-MEDA of Ala Littoria crashed on a flight from Tirana to Rome. The aircraft struck the mountains near {{ill|Maranola|it}} and all nineteen occupants were killed (14 passengers and 5 crew).{{Citation | title = The Italian Disaster | newspaper = Flight |page=442 | date = 5 May 1938 | url = http://www.flightglobal.com/pdfarchive/1935.html | access-date = 3 May 2011}}{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19380430-0|access-date=31 January 2017}}

;13 August 1938:S.73 OK-BAG of CSA (Ceskoslovenské Aerolinie) crashed on approach to Strasbourg with the loss of all 17 on board (13 passengers and 4 crew).{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19380813-0|access-date=31 January 2017}}

;10 October 1938:S.73P OO-AGT of SABENA broke-up in flight over Soest, Germany whilst en route to Berlin. All twenty on board were killed (16 passengers and 4 crew).{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19381010-0|access-date=31 January 2017}}

;17 October 1939:S.73 I-IESI?{{clarify|date=January 2017}} of Ala Littoria crashed en route to Melilla Airport (MLN/GEML) with the loss of 15 of the 17 persons on board (10 passengers and 5 crew).{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19391017-0|access-date=31 January 2017}}

;16 March 1940:S.73 I-SUTO of Avio Linee Italiane (ALI) crashed on Stromboli in bad weather killing all 14 aboard (9 passengers and 5 crew).{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19400316-0|access-date=31 January 2017}}

;14 May 1940:S.73P OO-AGP of Sabena was destroyed on the ground at Brussels-Haren Airport to prevent capture by invading German forces.{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19400514-0|access-date=31 January 2017}}

;23 May 1940:S.73P OO-AGS of Sabena was shot down by German ground fire near Arques,Most likely Arques, Pas-de-Calais. The RAF were operating from the nearby Merville aerodrome in May 1940. whilst being operated on behalf of No.271 Squadron RAF, with the loss of one crew member.{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19400523-0|access-date=31 January 2017}}

;23 May 1940:S.73P OO-AGZ of Sabena was destroyed on the ground at Merville whilst being transferred to No.24 Squadron RAF.{{cite web|title=Accident report|url=https://aviation-safety.net/database/record.php?id=19400523-2|access-date=31 January 2017}}

;{{BEL}}

• SABENA

;{{CZS}}

• ČSA

;{{flag|Kingdom of Italy}}

• Ala Littoria
• Avio Linee Italiane

;{{BEL}}

• Belgian Air Force

;{{flag|Kingdom of Italy}}

• Regia Aeronautica
• Italian Co-Belligerent Air ForceStroud 1984, p. 374.

;{{UK}}

• Royal Air Force
• No. 24 Squadron RAF
• No. 117 Squadron RAF

{{Aircraft specs

|ref=Italian Civil and Military aircraft 1930–1945Thompson 1963, pp. 258–259

|prime units?=met

|genhide=

|crew=4

|capacity=18 passengers + {{convert|362.9|kg|lb|abbr=on|0}} of baggage

|length m=

|length ft=57

|length in=2+3/4

|length sigfig=4

|length note=

|span m=

|span ft=78

|span in=8+2/3

|span note=

|span sigfig=4

|upper span m=

|upper span ft=

|upper span in=

|upper span note=

|mid span m=

|mid span ft=

|mid span in=

|mid span note=

|lower span m=

|lower span ft=

|lower span in=

|lower span note=

|swept m=

|swept ft=

|swept in=

|swept note=

|dia m=

|dia ft=

|dia in=

|dia note=

|width m=

|width ft=

|width in=

|width note=

|height m=

|height ft=15

|height in=1

|height note=

|wing area sqm=

|wing area sqft=1,000.7

|wing area note=

|swept area sqm=

|swept area sqft=

|swept area note=

|volume m3=

|volume ft3=

|volume note=

|aspect ratio=

|airfoil=

|empty weight kg=

|empty weight lb=12,760

|empty weight note=

|gross weight kg=

|gross weight lb=20,460

|gross weight note=

|max takeoff weight kg=

|max takeoff weight lb=

|max takeoff weight note=

|fuel capacity={{convert|3950|L|USgal impgal|abbr=on}}

|lift kg=

|lift lb=

|lift note=

|more general=

|eng1 number=3

|eng1 name=Piaggio Stella P.IX R.C.

|eng1 type=9-cyl air-cooled radial piston engines

|eng1 kw=

|eng1 hp=700

|eng1 shp=

|eng1 kn=

|eng1 lbf=

|eng1 note=

• (prototype fitted with 3 x {{convert|447.42|kW|hp|abbr=on|0}} Gnome-Rhone 9Kfs radial engines)

|power original=

|thrust original=

|eng1 kn-ab=

|eng1 lbf-ab=

|eng2 number=

|eng2 name=

|eng2 type=

|eng2 kw=

|eng2 hp=

|eng2 shp=

|eng2 kn=

|eng2 lbf=

|eng2 note=

|eng2 kn-ab=

|eng2 lbf-ab=

|eng3 number=

|eng3 name=

|eng3 type=

|eng3 kw=

|eng3 hp=

|eng3 shp=

|eng3 kn=

|eng3 lbf=

|eng3 note=

|eng3 kn-ab=

|eng3 lbf-ab=

|more power=

|prop blade number=3

|prop name=metal variable pitch

|prop dia m=

|prop dia ft=

|prop dia in=

|prop dia note=

|rot number=

|rot dia m=

|rot dia ft=

|rot dia in=

|rot area sqm=

|rot area sqft=

|rot area note=

|perfhide=

|max speed kmh=

|max speed mph=205

|max speed kts=

|max speed note=

• At {{convert|4,000|m|ft|abbr=on|0}}.
• On two engines, maximum speed was {{convert|270|km/h|mph|abbr=on|0}}

|max speed mach=

|cruise speed kmh=

|cruise speed mph=174

|cruise speed kts=

|cruise speed note=

|stall speed kmh=

|stall speed mph=56

|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=

|range miles=994

|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=

|ceiling ft=24,272

|ceiling note= On two engines {{convert|4,399|m|ft|abbr=on|0}}

|g limits=

|roll rate=

|glide ratio=

|climb rate ms=3.333

|climb rate ftmin=

|climb rate note=

|time to altitude=

• {{convert|2,000|m|ft|abbr=on|0}} in 10 minutes
• {{convert|4,000|m|ft|abbr=on|0}} in 20 minutes
• {{convert|6,000|m|ft|abbr=on|0}} in 33 minutes

|sink rate ms=

|sink rate ftmin=

|sink rate note=

|lift to drag=

|wing loading kg/m2=

|wing loading lb/sqft=

|wing loading note=

|disk loading kg/m2=

|disk loading lb/sqft=

|disk loading note=

|fuel consumption kg/km=

|fuel consumption lb/mi=

|power/mass=

|thrust/weight=

|more performance=

|armament=

|guns=

|bombs=

|rockets=

|missiles=

|hardpoints=

|hardpoint capacity=

|hardpoint rockets=

|hardpoint missiles=

|hardpoint bombs=

|hardpoint other=

|avionics=

}}

{{aircontent

|related=

• Savoia-Marchetti SM.81 Pipistrello

|similar aircraft=

• Junkers Ju 52

|see also=

|lists=

• List of aircraft of World War II

}}

{{commons category|Savoia-Marchetti S.73}}

{{Reflist}}

• {{cite magazine |last1=Cortet|first1=Pierre|title=Rétros du Mois |journal=Avions: Toute l'aéronautique et son histoire |date=May 1998 |issue=74 |page=57 |trans-title=Retros of the Month |language=French |issn=1243-8650}}
• {{cite magazine |last1=Emiliani |first1=Angelo|last2=Cony|first2=Christophe|name-list-style=amp |title=Un grand trimoteur civil: le SIAI Marchetti S.73|magazine=Avions: Toute l'Aéronautique et Son Histoire |date=December 2000 |issue=93 |pages=25–35 |trans-title=A Big Commercial Trimotor: The SIAI Marchetti S.73|language=French |issn=1243-8650}}
• {{cite journal |last1=Kudlicka|first1=Bohmuir|title=Post Scriptum: "Theo" Osterkamp et les Savoia-Marchetti S.73 tchécoslovaques |journal=Avions: Toute l'aéronautique et son histoire |date=December 2004 |issue=141 |pages=42–45 |trans-title=Postscript: "Theo" Osterkamp and the Czech Savoia-Marchetti S.73s |language=fr |issn=1243-8650}}
• {{cite magazine |last1=Kudlicka|first1=Bohumir|title=Un complément sur les Savoia-Marchetti S.73 tchéchoslovaques |journal=Avions: Toute l'Aéronautique et son histoire |date=June 2001 |issue=99 |pages=52–55|trans-title=A Complement of Czech Savoia-Marchetti S.73s|language=fr |issn=1243-8650}}
• Lembo, Daniele, SIAI 81 Pipistrello, Aerei nella Storia, n.33.
• {{cite magazine |last1=Rouchon|first1=Dominique|title=Courrier des Lecteurs|journal=Avions: Toute l'Aéronautique et son histoire |date=August 2001 |issue=101 |page=5 |trans-title= Readers' Letters |language=fr |issn=1243-8650}}
• {{cite book |last=Shores |first=Christopher |title=Dust Clouds in the Middle East: The Air War for East Africa, Iraq, Syria, Iran and Madagascar, 1940–42 |year=1996 |location=London |publisher=Grub Street |isbn=1-898697-37-X}}
• {{cite magazine |last1=Sordet|first1=Michel|title=Courrier des Lecteurs|journal=Avions: Toute l'Aéronautique et son histoire |date=February 2002 |issue=107 |page=2 |trans-title= Readers' Letters |language=fr |issn=1243-8650}}
• {{cite book |last=Stroud |first=John |title=European Transport Aircraft since 1910 |year=1966 |location=London |publisher=Putnam}}
• {{cite magazine|last=Stroud|first=John|title=Wings of Peace: No. 10: Savoia-Marchetti S.73|magazine=Aeroplane Monthly|date=July 1984|volume= 12|issue= 7|pages=370–374|issn=0143-7240}}
• {{cite book|last=Thompson|first=Jonathan W.|title=Italian Civil and Military aircraft 1930–1945|publisher=Aero Publishers Inc.|location=New York|year=1963|edition=1st|isbn=0-8168-6500-0}}
• {{cite magazine |last1=Wulf|first1=Herman de|title=An Airline at War|journal=Air Enthusiast |date=August–November 1980|issue=13|pages=72–77 |issn=0143-5450}}
• {{cite book |title= The Illustrated Encyclopedia of Aircraft (Part Work 1982–1985)|publisher= Orbis Publishing}}

{{Savoia-Marchetti aircraft}}

{{Portal bar|Italy|Companies|Aviation}}

S.73

Category:1930s Italian airliners

Category:Trimotors

Category:Low-wing aircraft

Category:Aircraft first flown in 1934