Savoia - Marchetti SM . 84 The Savoia - Marchetti SM . 84 was an Italian bomber aircraft of World War II . It was designed by Savoia - Marchetti as a replacement for its successful SM . 79 , and shared its three - engine layout . However , although it entered service with the " Regia Aeronautica " in 1941 , it never replaced the SM . 79 , being retired from service before it . Development . Development of an aircraft to replace the SM . 79 started in 1939 , with Savoia - Marchetti choosing to produce an improved development of the SM . 79 , using the same wing as its predecessor , but with a new fuselage and more powerful engines . The first prototype flew on 5 June 1940 , just 5 days before Italy ' s entry into World War II . It was hoped to replace the SM . 79s in service , which were fast , but obsolescent , and yet to be adapted as torpedo bomber s . The main improvement was the adoption of new and more powerful engines , giving a total output of 2 , 237 kW ( 3 , 000 hp ) . The machine was put into series production at the end of 1940 . Design . Basically it was an enhanced SM . 79 , with more modern solutions and systems It shared the basic design of a three - engine mixed construction monoplane as the SM . 79 . Wood was used for the wings , supported by three spars . Steel tubing was used as a skeleton for the fuselage , covered by metal ( forward ) , fabric and wood . The new fuselage housed a crew of five to six , with the pilots sitting side - by - side . Behind them there were a radio - operator and flight engineer . They enjoyed a large windscreen and eight windows in the fuselage . The armour was much improved compared to the almost nonexistent protection fitted to the SM . 79 ; it was said there was a total of 700 kg ( 1 , 540 lb ) fitted , however it is unclear if this also included the self - sealing fuel tank s , bullet - proofed up to 12 . 7 mm ( . 50 in ) rounds . One noticeable difference was the twin tail , which gave a better field of fire to the dorsal gun , and helped to cope with the greater power and weight compared to the SM . 79 . Armament was similar to the Cant Z . 1007 , rather than the SM . 79 . There was a dorsal Caproni - Lanciani Delta turret , with a 12 . 7 mm ( . 50 in ) Scotti machine gun , and 350 rounds . Another Scotti was in the ventral gondola . Other two Scotti were in the flanks with six 120 - round belts . It was a theoretical improvement , though Scotti machine guns , even with a slightly higher rate of fire , were much less reliable than the Breda . Another disadvantage was the inability of the turret to fire directly forward , through the propeller ' s blades , so the aircraft had no defence from frontal attacks . The bomb bay was in the middle of fuselage . Horizontally mounted , the aircraft could carry two 500 kg ( 1 , 100 lb ) , three 250 kg ( 550 lb ) , 10 100 kg ( 220 lb ) , or 10 50 kg ( 110 lb ) bombs . Outside the fuselage it was possible to mount two 500 kg ( 1 , 102 lb ) or 800 kg ( 1 , 760 lb ) bombs , or two torpedoes , or even smaller bombs like eight 100 kg ( 220 lb ) or 50 kg ( 110 lb ) ( but really weighing of 130 kg / 290 lb and 70 kg / 150 lb ) . Generally , the aircraft carried only one torpedo or around 1 , 000 kg ( 2 , 200 lb ) of bombs . The aiming apparatus was a " Jozza " U3 , fitted in the bombardier ' s nacelle , just below the cockpit . It was retractable when not in use , to reduce drag . An OMI camera was fitted in the fuselage , while in the tail section it was possible to mount one of three different cameras , like the AGR . 90 or 91 . Three Piaggio P . XI RC . 40 engines , giving 746 kW ( 1 , 000 hp ) at 4 , 000 m ( 13 , 120 ft ) were fitted . There were 16 self - sealing fuel tanks inside the wing and the fuselage , six for the central engine ( 1 , 070 L / 283 US gal ) and five for each wing engine ( 1 , 095 L / 289 US gal ) . Total fuel load was 3 , 260 L ( 860 US gal ) , which was less , despite the more powerful engines , than previous Italian bombers . It was possible , however , to mount another three fuel tanks : two of 415 L ( 110 US gal ) in the fuselage , and one of 2 , 500 L ( 661 US gal ) in the bomb - bay . With these engines , at full load the SM . 84 was capable of : Climb rates to : The maximum practical ceiling was 8 , 200 m ( 26 , 900 ft ) . At 5 , 500 m ( 18 , 050 ft ) and 397 km / h ( 247 mph ) , it had 5 hour 17 minutes endurance , and a range of 2 , 040 km ( 1 , 270 mi ) . As was expected , the performance of the SM . 84 was superior to the SM . 79 . Operational history . The first unit to operate the aircraft was 12° Stormo ( Wing ) , 41° Gruppo ( Group ) , on 2 February 1941 . Based at Rodi , the first actions of this Group were not successful , and two aircraft landed in Turkey being lost ( their crews later returned to Rodi ) . 36° Wing ( 108 and 109 Gr ) received its SM . 84s on 7 May 1941 , and was based at Decimomannu airbase , Sardinia , from September 1941 . On 27 September 1941 , 12 aircraft of 36° Wing took off to attack a British convoy to Malta ( Operation Halberd ) . One aircraft turned back after developing a mechanical fault , but the remainder pressed on with their attack . The first group , led by Arduino Buri , attacked the British ships and Buri managed to torpedo , putting her out of action for six months . Of the first section , one aircraft was shot down , and the second section had two aircraft shot down out of three . When Seidl went in with his five aircraft , he was shot down together with another two . While the damage to " Nelson " was a success , the only one this type that Italian torpedo bombers obtained , it was paid with the loss of six aircraft , and almost all the crews , more than 30 men . The next day a merchant ship , " Empire Pelican " , was sunk by SM . 79s with only one loss . The rest of the convoy reached Malta with their supplies . After these losses , 36° Wing continued in its task to attack enemy ships , and sank the merchant ship " Empire Defender " in November , and 9 SM . 84s badly damaged on 9 April 1942 . 282° " Squadriglia " was also involved in such missions , with some success . 7° Wing ( 4 and 5 Gruppos ) , based in Sicily , used SM . 84s to bomb Malta in July 1941 . In mid - October 1941 , 32° Wing were equipped with SM . 84s , one group of torpedo bombers and the other of bombers , to best optimize the attack against ships . This Wing took part in attacks on the Allied landings of Operation Torch , but by the end of December the unit had lost 20 aircraft and was retired from operations . In June 1942 , 14 torpedo bombers of 36° Wing and nine bombers of 4° " Gruppo " attacked the Malta convoy of Operation Harpoon , with at least two losses to Spitfire s , and one downed by Anti - aircraft fire . During Operation Pedestal in August 1942 , 10 SM . 84s used special Motobomba circling torpedoes to attack the convoy , losing two aircraft to enemy fighters . Aircraft of 32° and 36° Wing also attacked the convoy . The heavy German and Italian attacks , including those by SM . 82s resulting in only five of the fourteen ships of the convoy reaching Malta , however their supplies were fundamental to saving the garrison , after the almost total failure of the previous operation . While other groups were still receiving the aircraft , 36° and 7° Wing had stopped flying it by October 1942 , while 32° went in action against North African targets . It lost 20 aircraft and returned in Puglia to regroup in December 1942 . Soon 38° Gr had the new SM . 84 Bis ( early 1943 ) , this last version was delivered to 8° Stormo ( 27° and 28° Gruppos ) . The decline had already started . The use of the aircraft with 8° Stormo to resupply troops in North Africa was a failure : despite having a far higher speed than the SM . 82 , the useful payload of the SM . 84 was too small . The aircraft was gradually phased out , replaced by the Cant Z . 1007 , and even the SM . 79 . By 10 July 1943 43° Wing , flying from Gioia del Colle , Puglia , was the only unit still flying the SM . 84 . In September 1943 , despite the almost extinction of bombers units , there were still 150 SM . 84s in available , with over 100 serviceable . Almost all of these were captured by the Germans , though they were rarely used . Some were sent to the " Slovenské vzdušné zbrane " , and 10 remained with RSI ' s " Aeronautica Nazionale Repubblicana " , but were not used . Seven were used by the Italian Co - Belligerent Air Force as transports . Shortly after the end of WWII , the aircraft was phased out of service . Overall , SM . 84 was a failed design ( Francesco Pricolo called it a ' wrong aircraft ' , while Ettore Muti complained in 1941 about its awful handling and take off ) . It was never liked by its crews and never capable of replacing the SM . 79 . When the final version of the Sparviero , the SM . 79 bis , became available , the SM . 84 was withdrawn . In the bomber role it was inferior to the CANT . 1007 ter , especially at altitude ( the SM . 84 was almost impossible to fly above 5 , 000 m ) . Torpedo - bombers were required to be agile and fast in order to engage their targets and many designs experienced problems with higher weights and wing loading than they were designed for . The SM . 84 was far heavier than the SM . 79 and when the final version the SM . 79bis became available , it was preferred to the SM . 84 . The SM . 79bis , with improved engines was still lighter than the SM . 84 and a better aircraft ( with lower wing loading and better power - to weight ratio ) for the role . Another critical report about SM . 84 came from the 43° Stormo B . T . command , in an official document . It reports how this bomber wing performed its task , starting with bombing missions from Gioia del Colle on 13 July 1943 . The 41° Stormo commander complained the very small attack force was not enough to saturate the enemy ' s strong defences , even by night ; the small number of pilots trained for night operations and thus the small number of sorties and the very poor performance of the SM . 84 . Operators . " Regia Aeronautica " :