Piaggio P.108

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Piaggio P.108
Piaggio P.108 side view
Type	Bomber
Manufacturer	Piaggio
Designed by	Giovanni Casiraghi
Maiden flight	1939
Introduced	1942
Retired	1945
Primary users	Regia Aeronautica Luftwaffe
Number built	30-35 (24 were bombers)

The Piaggio P.108 Bombardiere was an Italian four-engined heavy bomber used by the Regia Aeronautica during World War II. It first flew in 1939 and entered service in 1942.

Four versions of the P.108 were designed, but only one, the P.108B, was produced in any quantity before the armistice. The other variants included the P.108A anti-shipping bomber with a 102 mm gun, the P.108C, an airliner with an extended wingspan and re-modelled fuselage capable of carrying 32 passengers, and the P.108T transport version designed specifically for military use. Only one of the P.108As was built, and 24 P.108Bs. The combined total number of P108Cs and Ts built was approximately 16, but it is unclear precisely how many of either version, however, most of the P.108Cs were subsequently modified for use as military transport aircraft and could accommodate up to 60 passengers.^[1]

Contents 1 P.108B 1.1 Design and development 1.2 Technical details 1.3 Engines and performance 1.4 Armament 2 P.108A 3 P.108C/T 4 P.133 5 Operational history 5.1 Gibraltar 5.2 Algeria and Africa 5.3 Sicily 6 Variants 7 Specifications (Piaggio P.108B) 8 Operators 9 References 10 Links 11 See also

[edit] P.108B

[edit] Design and development

The P.108 was the only four-engined heavy bomber used by the Regia Aeronautica during World War II, and was a development of the earlier underpowered and wooden-structured P.50-II which was unable to take-off at its designed maximum weight. Giovanni Casiraghi, an experienced engineer who had previously worked in the USA for several years, re-engineered this bomber giving it a metallic structure. Still not entirely satisfied, he started another, almost new aircraft project, the P.108, and initial developments resulted in the P.108B. Despite some competition (the winner was initially seen as the Cant Z.1014), Piaggio won the Regia Aeronautica's contract for a new bomber, as it became obvious that the other competitors could not deliver useful numbers of aircraft to the Regia Aeronautica before the mid 1940s.^[2]

The first prototype P.108B flew on 24 November 1939. ^[2] The "teething problems" of the P.108 involved a very long period of debugging, and the process of improving its reliability was never totally successful. The first machines were sent to 274 Squadriglia in 1941. Bruno Mussolini, son of Benito, commanded this unit and was flying in one of the prototypes when on 7 August 1941 the aircraft got too low and crashed into a house, drawing attention to the "secret" bomber.^[3] The cockpit section was separated from the rest of the aircraft, and Mussolini died of his injuries. The machine did not catch fire, but was nevertheless totally destroyed in the impact. By the end of 1941 it had flown just 391 flying hours, compared to the 9,293 flown by the first 12 B-17s.

Even so, the new bomber showed much promise. Apart from the modern (but costly) structure, and having practically double the range with the same load, it was not too expensive compared to standard bombers. The average Italian bomber cost around 2.1 million lire, the SM.79 cost 1.7 million lire, while the P.108 cost 5.2 million lire.^[4] With a single squadron of nine P.108s capable of flying 1,100 km with 3,500 kg, the estimated efficiency was comparable to a group of 26 SM.79s covering 1,000 km with 1,000 kg. The total cost of the aircraft was 46.8 and 45.6 million lire respectively, but only 54 crew were required as opposed to 130.

The P.108B's engines were designed to be more powerful than those propelling the B-17, and most of its defensive gun turrets were remote-controlled, but its reliability fell short of the typical Allied heavy bombers, and this type remained relatively unknown until the 1970s.

The second series, designated P.108B II, were revised series Is having had the nose turret removed. While this reduced defence against head-on attacks, this protection was less important as the aircraft was operated mainly at night. The speed gain was 10 km/h (6 mph), due to the weight reduction and the more aerodynamic nose.^[1]

[edit] Technical details

The P.108 was an all-metal, four-engined bomber, with a crew of eight. It had a very robust modern structure (with a 6 g tolerance) designed by Giovanni Casiraghi, and made almost entirely in duraluminium.

The accommodation for the crew included a two-pilot cockpit with several (5-6) crew members located in the mid-fuselage and nose, and like early B-17 Flying Fortresss, the P.108 had no tail turret. The most noticeable feature was the nose, having a separate structure for the bombardier, with the front turret above him; similar to the nose of the Armstrong Whitworth Whitley with the lower part protruding from the rest. The P.108's tail was even larger, because of the necessity to stabilise the heavy, powerful aircraft (30,000 kg (66,000  lb) and up to 6,000 hp (4,500 kW) at take-off, around 20% more than early B-17s). ^[4]

[edit] Engines and performance

Piaggio was one of the few Italian aviation industries that had the capability to develop both aircraft and engines; and their P.XII engines, although unreliable, were among the most powerful of their time. Fiat was a much larger concern that also designed and manufactured airframes and engines, but limited its production to aircraft like the BR.20 Cicogna, a conventional medium-bomber, while Piaggio experimented with advanced aircraft and engines.

The P.108 was equipped with four air-cooled 18-cylinder P.XII radial engines, which for years suffered from reliability problems, but produced 1,350 hp at 3,000 m, with 1,500 hp at takeoff, so are listed as both 1,350 and 1,500 hp (some sources state 1,200 and 1,350 hp, probably due to confusion over which version of these engines was mounted), and drove three-blade constant-speed Piaggio propellers. The P.XII was basically two Piaggio P.X engines in tandem, which were versions of the French Gnome-Rhône 9K Mistral made under license, themselves being license-built Bristol Jupiters. Alfa Romeo also lacked a powerful, modern engine, and its 1,350 hp AR.132s were two Bristol Mercurys in tandem.^[4]

Its 12 self-sealing fuel tanks could hold around 12,000 litres, and the eight oil tanks, two for each engine, held a total of 350 litres. The combination of a heavy airframe and powerful engines resulted in high fuel consumption, and the P.108's performance at high altitude was mediocre, with a practical ceiling of about 6,000 m and a theoretical 8,000 m. By comparison, the B-17C was capable of attaining a 3,000 m-higher ceiling both in theory and practice.^[4]

The P.108 could reach speeds of 420 km/h at 4,300 m, which was slower than several types of biplane aircraft, whereas the B-17C was capable of 515 km/h at over 7,000 m and so was practically immune to fighter interception until 1942, even if its range and bombload, 3,220 km with 1,800 kg, were slightly inferior to those of the P.108's 3,335 km with 2,000 kg.^[4]

The aircraft could fly 2,500 km with a bombload of 3,500 kg, and 3,600 km with 600 kg. Though much better than a typical Italian bomber (800-900 km carrying 1,000 kg), this was not impressive compared to the Avro Lancaster, able to fly 3,100 km carrying 4,000 kg, and the B-24, about 3,220 km with the same load. Even SM.82s, normally with around half of the P-108's fuel (around 5,500 litres), were able to reach long-range targets, such as Gibraltar, when adapted to carry the necessary additional fuel.

[edit] Armament

P.108 had a large bomb bay which was capable of carrying either:

• seven 250 or 500 kg bombs.
• 34 x 100 kg (true weight: 129 kg).
• 38 x 50 kg (true weight: 69 kg) bombs.

The bomb bay was located centrally in the fuselage, and divided longitudinally into three sections which prevented it from carrying heavier bombs like the 800 kg types. This was a considerable limitation, and similar to the Short Stirling, the P.108 was hampered by having a bomb bay divided into insufficiently large sections, whereas the SM.82 was capable of accommodating larger loads (being able to be used both in transport and bomber role). In the torpedo-bomber configuration, three torpedoes could be carried under the belly and the wings.

The defensive armament of the first P.108 series consisted of eight Breda-SAFAT machine guns. One Breda "O" 12.7 mm machine gun and 450 cartridges was fitted in the nose, and a Breda "G" 12.7 mm in a retractable ventral turret, with 400-450 rounds per gun. In addition to these two fully hydraulically-powered turrets, there were two 7.7 mm guns in the flanks, with 500 rounds each. The wing armament, which constituted the main defence of the aircraft, consisted of two radio controlled, hydraulically-powered Breda "Z" turrets with 600 rounds per gun in the inner-engine wing gondolas, linked to one of the two cupolas in the fuselage "hump", with an operator in each. The wing turrets represented the most innovative aspect of the P.108's technology.^[4]

Although considered a very advanced design, the operational suitability of the wing gondola turret installations was questionable.^[5]

• The wing turrets were vulnerable to battle damage, icing, jamming, and were notoriously unreliable due to the complexity of the sophisticated gun control and computing device (the hydraulic systems had circuits stretching for several metres to the external engine turrets).
• The firepower endurance was adequate for limited combat such as that likely to be encountered during night missions, but insufficient for the needs of extended combat. A total of 300 rounds, fired at full ROF by the Bredas (no synchronizer present, different to fighter installations) was enough for only 25 seconds of use (around 12 two-second bursts). American bombers generally had 500 cartridges for each 12.7 mm gun and often carried extra ammunition.
• In contrast with the fuselage turrets, there was no possibility of maintaining, reloading or repair while on a mission.
• The mainly rear-directed field of fire was poor, partially blocked by the tail surfaces, with fire in a frontal arc possible only with high degrees of elevation (avoiding the propellers), and no capability against targets below.
• If these turrets were disabled, the P.108 was left with only 2 x 12.7 mm and 2 x 7.7 mm machine guns, leaving many blind spots all around the bomber, because none of the flank, nose, or ventral guns' fields of fire covered attacks from the rear or above.^{[citation needed]}

[edit] P.108A

In response to a request in November 1942, the P.108A Artigliere "gunship" was developed for anti-shipping duties as an alternative to torpedo-bombers. It was armed with a modified high muzzle velocity Ansaldo 1941 model (90/53 mm) gun mounted in a redesigned nose. This was considered to provide the best combination of precision and range of all Italian artillery, and in several versions was used as an anti-aircraft and anti-tank gun by the Army and the Navy. To be more effective in its new role, the calibre of the gun was increased from 90 mm to 102 mm, a non-standard Italian artillery bore, and fired shells weighing 13 kg as opposed to the standard gun's 10 kg shells, with a muzzle velocity of over 600 m/s. This weapon has only been superseded in calibre, on aircraft, by the low velocity 105 mm modified M102 howitzer (23 calibres in length) carried on a mobile mounting in the flanks of the AC-130's 3.2 m width fuselage. The gun together with its recoil system weighed 1,500  kg.^[6] Due to it being a re-bored smaller gun, its weight was relatively low for its calibre.

The P.108A wasn't particularly unusual at the time, as medium bombers and even smaller attack-aircraft like the Henschel Hs 129 were fitted with high-velocity 75 mm guns despite being one or two categories lighter.

The gun was mounted longitudinally in the fuselage centreline, at a depressed angle, and had a very strong recoil action which the 30 ton airframe was nevertheless able to absorb. The amount of ammunition that could be carried was around 50-60 rounds for the main gun, as well as up to three standard torpedoes or two radio-guided torpedoes (a secret weapon which was never used in combat), and finally the standard defensive weapons in the fuselage and wings. The 102 mm gun was intended to be fitted with a ballistic sight with an analogue computer, and a six or 12 rounds mechanical loader.^[1]

Initial modifications were made to MM.24318 which on 16 December 1942 flew to Savona, Villanova d'Albenga airfield. The modifications were completed in February 1943, and testing commenced 3 March.

Testing of the P.108A was satisfactory, achieving a maximum speed of around 440 km/h due to the more aerodynamic redesigned nose. It flew to Furbara on 19 March, and later to Pisa on 16 April, where it carried out a series of firing trials at altitudes between 1,500 and 4,500 m to collect the ballistic data for negative angles of elevation that was required to allow the computing gunsight to be produced.^[7] After totalling 24 h 40 min of flight and weapons trials, it returned to Albenga. Enthusiasm was high when it was presented as the new official attack machine at Furbara on 22 May, and it was planned to make five further P.108As, as well as convert another five or possibly all P.108s available. But on 29 June it was decided to produce no more than five aircraft, and in July, the order was limited to only two, and eventually cancelled. On 6 and 8 September the lone P.108A made other weapons tests over the sea, finally equipped with the S.Giorgio calibration/aiming system.^[1] German forces took control of the P.108A and painted it with their insignia, but soon after it was damaged by Allied bombing. Repaired 7 April 1944, it finally flew to Rechlin where it was probably destroyed in one of the many Allied bombing raids.

Although the P.108A proved to be capable, and fired over 280 shells in testing, the Armistice and the never-ending change of priorities halted its development. The use of such large aircraft in a dangerous anti-ship role was however questionable (at sea level 360 km/h was the best safely achievable), the cost was even greater than standard bombers, and the improved naval anti-aircraft defences (Bofors 40 mm guns, P-F shells, and fire-control radar) led Germany to rely on (relatively) long-range missiles like the Henschel Hs 293 and Fritz X. These were much more effective, as demonstrated 9 September 1943, when the Italian Navy was struck by these missiles, launched by their prior allies. The Germans launched a number of missiles against the Italian battleships, sinking the Roma and damaging the Italia, causing over 1,300 deaths. The three armoured decks of RM Roma could withstand hits from battleship-calibre guns, with over 200 mm thickness overall, so such results were well outside the capabilities of a medium calibre gun, even when air-transported.

[edit] P.108C/T

While the P.108B's troubled development continued, Piaggio's workload was further stressed by the request for new transport aircraft, capable of long-range flights to South America for Linee Aeree Transcontinentali Italiane (LATI). The intention in 1939 to license-build the Boeing 307 wasn't realised, so in 1940 it was proposed to use the P.108C, as an "interim" transport awaiting the P.126C and even the P.127C six-engined variant. They were planned to have a pressurised cabin to accommodate 32 passengers in a wider fuselage, but no armament at all. The prototype first flew on 16 July 1942, when there were no longer any transatlantic lines to serve. Despite this, and the inability of Piaggio to deliver P.108B bombers on time, an order for a further five P.108Cs was placed ^[8].

On 26 March 1941, the P.108T military cargo version was ordered. This unpressurised variant was fitted with one Caproni dorsal turret, one Breda in the ventral turret, and two flank machine guns, all of 12.7 mm calibre, and was capable of 440 km/h. Through a ventral door of 4.8 m length and 1.9 m width it was possible fit two Macchi C.200s. The internal volume was over 77 cubic metres, and could carry up to 60 soldiers^[8], eight torpedoes or 12 tonnes of cargo.^[1] After many changes in design, the first P.108T flew on 7 September 1942. Although the 148 ima Squadriglia was intended to use both P.108Cs and P.108Ts, only a few were built before the Germans took control of production, subsequently at least 11 other examples were completed.

Four P.108Cs and five P.108Ts ^[8] were handed over to the Luftwaffe and used on the Eastern Front, notably during the 1944 evacuation of Axis troops from Crimea following the fall of Sevastopol. The P.108C (civil airliner, with 32 seats) and T (military transport) were more reliable than the bomber variants, and their capability of carrying heavy loads (such as two dismantled fighters) was important, as the Luftwaffe did not have many heavy transport aircraft, relying mainly on the smaller Ju 52s. These aircraft also had four MG 131 machine guns as defensive armament, with one in a dorsal turret, one in a ventral position, and two waist positions. ^[9]

One example, known as "Die General", was destroyed on Salonicco airfield. Transportfliegerstaffel 5 operated most of these aircraft and used them until the end of war, with one assigned to the links between Italy and Germany and the other on the Eastern front. On 10 August 1944 an air raid destroyed six of them and another four were destroyed or captured in 1945. The P.108T-2, a postwar version was proposed but without success, and thus ended the P.108-series history.

[edit] P.133

The final development of the P.108, the P.133 prototype, was almost complete by the Armistice (8 September 1943), but afterwards the program was dropped and the aircraft was never finished. It was designed to have a lighter structure and several improvements in performance, partially influenced by a captured B-24, with a potential speed of 490 km/h, 6 x 20 and 4 x 12.7 mm guns and a bombload of up to 4.8 tonnes.

[edit] Operational history

P.108Bs were deployed across the Mediterranean and North African theatres, and first saw action in an unsuccessful day mission against a destroyer, on 6 June, releasing 10 x 160 kg bombs. The aircraft were effectively used a few weeks later, with a night bombing raid over Gibraltar, 28th June 1942.

[edit] Gibraltar

The first action over Gibraltar was almost a disaster: out of five aircraft which set out from Decimomannu in Sardinia, one (MM.22004) was forced to abandon this mission due to engine trouble while the other four bombed with 66 x 100 kg and 6 x 250 kg bombs. Three of them, short of fuel, were forced to land in Spain, two of which (MM.22001 and 22005) crashed or suffered heavy damage. The third (MM.22007), was quickly refuelled and took off from Palma de Majorca for Italy, but the others remained in Spain. ^[10] Several other missions were launched until October which resulted in some damage but resulted in further losses, in an attempt to transition to the SM.82s that were only a temporary expedient (as was the P.108, expecting more from the future P.133).

For a precise chronology, there were actions performed over Gibraltar (without the endurance problems that dogged the first mission) during the night of 3 July (MM.22601, which failed to return), 24 September (MM22004 and 22603), 20 October(MM.22002 (written off during emergency landing after engine failure on take-off), MM.22004, 22006 and 22007) and 21 October (MM.22602 (destroyed during emergency landing at Bona in Algeria) and two other P.108s), when the "peak" was reached. ^[11] Each of these missions, involving one to four aircraft (15 sorties in total), was unsuccessful and resulted in around 33% losses. The results were poor, with one Hudson and some artillery positions destroyed on the ground in the first, "big" mission, and further unspecified damaged in the others, despite intensive long-range mission crew training between 3 July and September. On 28 October, MM22007 force-landed in Algeria on its third mission, making in total at least 16 sorties with one aircraft missing, two lost in Spain, two lost in Algeria and one lost in Italy.

[edit] Algeria and Africa

Following the Allied invasion, "Operation Torch", there were more losses sustained when these aircraft flew missions over Algeria and other African targets. The Allies had over 160 warships and 250 merchant ships there, while the Luftwaffe had 1,068 aircraft in the II and X Fliegerkorps, and the Regia had 285 machines in Sardinia, of which 115 were torpedo-bombers. At least three were downed over Africa in this series of raids, the most part claimed by Beaufighters. Nevertheless, in Algeria they struck targets in Bona (now called Annaba), Algiers, Blinda, Philippeville (now called Skikda), Maison Blanche, and Oran.

Some ships were damaged by P.108s in the latter and Algerian raids, and over other targets they destroyed some aircraft. These bombers were the only ones capable of flying the 2,000 km to Orano. The 274 Squadriglia had only eight P.108s and with them performed only 28 sorties in eight night missions, during a whole month. Three were shot down by night fighters, which on only one occasion were repelled by the wing turrets. Two P.108s were shot down by 153 Sqn Beaufighters in the attack over Algeria's port, and the last of these missions was flown on 20 January. The capability dropped to one or two serviceable aircraft and so, with the need for refurbishment, the P.108s returned to the mainland.

[edit] Sicily

The final action took place over Sicily, when the 274 ima was reinforced up to the basic force of eight machines. They flew against the immense invasion force with 12 sorties between 11 and 22 July. The losses suffered in this whole campaign included two aircraft destroyed and two others heavily damaged, mainly by Beaufighter and Mosquito night-fighters. Only one ship was damaged, and this closed the career of 274 ima and the P.108B.

The last of 24 P.108Bs ordered was delivered in August. Of these aircraft, six were lost to enemy action (three over Algeria, two over Sicily, and perhaps one over Spain), four to accidents (including the one of Mussolini), and three to forced landings (one in Algeria, and two over Spain).

When the Armistice was declared on 8 September 1943, only nine aircraft remained. Eight were sabotaged so as not to fall into German hands, and the last flew to southern Italy, where it was involved in a landing accident. P.108Bs ended their activities with a total of about 15 missions over Gibraltar, 28 over North Africa, 12 over Sicily and some other reconnaissance or anti-ship sorties out at sea (only one is known). This aircraft was too complex and difficult to develop without support from the Air ministry and other larger concerns, such as Fiat. None was forthcoming, and while Piaggio was still struggling to debug and produce the P.108B, there were many other requests for the P.108C airliner, the P.108T military transport, and P.108A anti-ship versions. Finally, there was also the new strategic-bomber, the P.108bis or P.133 to be developed as the "final solution" for Italian bombers, and even more projects, as the P.126, P.127, P.130 as airliners were considered.

Following the P.108Bs' last missions, a few P.108T transports continued to be used until the end of the war, mainly on the Eastern Front when Germany needed to evacuate their encircled troops, even carrying (in emergencies) over 100 troops at a time (maximum load was 12 tonnes, the total payload was around 14 tonnes). The P-108Cs and Ts proved to be more reliable than the bombers, following successful efforts to improve and modify them.^[1] One was destroyed in a flying accident over Germany, early in 1945, while the others were used until the end of the war.

[edit] Variants

Production totals of the P108C and T are unclear, but combined there were approximately 16 built, with most of the P108Cs subsequently converted to the transport version.

• Prototype : MM 22001
• Series 1  : MM 22002—22008, MM 22601—22604
• Series 2  : MM 24315—24326
• Series 3  : MM 24667—24678

P.108 Prototype

P.108A Artiglieri

Anti-shipping version. One built.

P.108B Bombardiere

Heavy bomber version. 24 built.

P.108C Civile

Civil transport version. Uncertain number built, but probably six.

P.108M Modificato

Intended modification of P.108B with heavier armament. None built

P.108T Transporto

Transport version. More than 12 (including converted P.108Cs).

P.133

Advanced version of the P.103B with better engines and increased bombload. Not completed.

[edit] Specifications (Piaggio P.108B)

Data from^{[citation needed]}

General characteristics

• Crew: 6 or 7
• Length: 22.30 m (73 ft 2 in)
• Wingspan: 32.00 m (105 ft)
• Height: 6.00 m (20 ft)
• Wing area: 135.0 m² (1,453 ft²)
• Empty weight: 17,325 kg (38,195 lb)
• Max takeoff weight: 29,885 kg (65,885 lb)
• Powerplant: 4× Piaggio P.XII RC.35 radial engine, 1,120 kW (1,500 hp) each

Performance

• Maximum speed: 430 km/h (267 mph)
• Range: 3,520 km (2,187 miles)
• Service ceiling 8,500 m (27,187 ft)

Armament

• 5x 12.7 mm Breda-SAFAT machine guns
• 2x 7.7 mm Breda-SAFAT machine guns
• 3,500 kg of bombs

[edit] Operators

Italy 

Regia Aeronautica

 Germany 

Luftwaffe

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (September 2007)

[edit] References

Notes

Bibliography

[edit] Links

• P108B.htm Piaggio P.108SITE IS DOWN 10/15/2007
• Piaggio P.108 (russian language)
• Commando Supremo P.108
• Regia Marina site, with P.108 article
• Special Hobby 72nd Scale Plastic Model Review

[edit] See also

Related development

• Piaggio P.50
• Piaggio P.112
• Piaggio P.113
  

Comparable aircraft

• Junkers Ju 290
• Petlyakov Pe-8
• Short Stirling
  

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