1941 Ilyushin DB-3 – Valery Rudenko
DB-3
The DB-3 went into production at Plant No. 39 in Moscow and Plant No. 18 in Voronezh. To perfect the bomber during series production, Plant No. 39’s experimental workshop was transformed into a design bureau, with Sergei Ilyushin as chief designer. This was simply a formality, because by that time the Ilyushin OKB had already been formed as a united team of designers capable of solving different problems concerning the development and updating of advanced combat aircraft.
From May to October 1937 pre-production DB-3 No. 3039002 underwent state tests at the Nauchno Issledovatelyskii Institut (NIl – scientific and research institute of the WS). Its performance proved to be slightly inferior to that of the prototype. At a weight of 14,550lb (6,600kg) it had a sea level speed of 201mph (325km/h), attained 242mph (390km/h) at 16,400ft (5,000m) and reached its service ceiling in 46 minutes. With such a performance the DB-3 considerably outperformed Germany’s Junkers Ju86D and even the new Heinkel He 111B then under test at Rechlin. The He 111B was 6.2 to 12.4mph (10 to 20km/h) slower at all altitudes and its service ceiling was 4,600ft (1,400m) lower, while its armament was the same and controllability and stability were better.
Not only were the DB-3’s aerodynamics excellent, but its fuel and oil capacity were equal to one-third of its maximum take-off weight. As a result it had ranges of 2,485 miles (4,000km) with a 1,102lb (500kg) bomb load and 1,926 miles (3,100km) with a bomb load of 2,204lb (1,000kg), while the He 111B managed 1,031 miles (1,660km) with 1,653lb (750kg) and 565 miles (910km) with 3,306lb (1,500kg). Early in its successful life the DB-3 gained the high appreciation of its pilots. Particularly notable were its ease to take-off, rapid climb, good stability without any suggestion of yaw, steady level flight (which made it a good bombing platform), tight turns with 40* to 60* of bank, and easy landing approach. It had no dangerous tendencies such as rapid loss of speed, wing stall and arbitrary ballooning during landing. The DB-3 also had good single-engine capabilities, and at a normal flying weight of 15,432lb (7,000kg) could climb and turn in both directions on one engine. However, pilots noted a lack of longitudinal stability owing to the generally accepted aft cg position.
In 1937, with the help of a number of Ilyushin Design Bureau designers including A Belov, V Biryulin, M Yefimenko and A Levin, the two plants manufactured 45 DB-3s, and that year the bomber was introduced into the inventory of the Soviet WS. It considerably outperformed similar bombers built in Germany, England, France and the USA.
Its high performance, especially with regard to range, was proved during two long range flights made by the modified TsKB-30, now named Moskva, during 1938-1939. On one of these, flown on 28/29th April 1939, pilot V Kokkinaki and navigator M Gordienko covered 4,971 miles 8,000km (4,048 miles/ 6,515km in a straight line) non-stop at an average speed of 216mph (348km/h). This was a significant achievement for Soviet aviation at that time. The Moskva’s long-distance flights greatly influenced the development of the DB-3’s airframe, engines and equipment. Moreover, flights by Kokkinaki and many other Soviet pilots enabled piloting techniques for long range flights to be developed and revealed the crew fatigue limits. These aspects also promoted efficient weather survey and communication services.
All of this elevated the combat capabilities of Soviet long-range aviation, based at that time on different variants of the DB-3, which was constantly being improved. In 1938 the M-85 engine was replaced by the M-86 with an augmented rating of 950hp (708kW). This allowed the DB-3’s good take-off performance to be retained in spite of increased weight. The maximum speeds at various altitudes remained the same. From 1938 the bomber’s speed was increased by the installation of M-87As and the use of VISh-3 variable-pitch propellers instead of fixed-pitch units, which meant that engine power was used to best advantage during different phases of flight. The M-87A, which had the same take-off power as the M-86, provided 800hp (596kW) at an altitude of 15,500ft (4,700m).
During tests at the NII WS early in 1939, two bombers produced at Plants Nos. 18 and 39 demonstrated improved performance. At a flying weight of 15,873 to 17,195lb (7,200 to 7,800kg) their sea level speeds were equal to 265 to 270mph (428 to 436km/h) at a critical altitude of 16,300ft (4,960m). The service ceiling had increased to 30,200 to 30,500ft (9,200 to 9,300m), and the time to climb to 16,400ft (5,000m) was 10.7 minutes. The take-off run was 1,148 to 1,312ft (350 to 400m) and the maximum overloaded weight had risen to 21,375lb (9,696kg). In the final test report it was noted that the aeroplanes produced by Plant No. 39 were of higher quality. In 1938 another factory, No. 126 in Komsomolsk, was also converted to DB-3 production, increasing output by 400 aircraft.
DB-3T and DB-3TP
The Ilyushin Design Bureau constantly extended the applications of the DB-3, and the DB-3T variant of 1937 was used as a naval torpedo bomber. By virtue of special external attachment points it could carry a 45-36 type torpedo (the first number denoted the torpedo’s calibre in centimetres, the second its year of introduction into the inventory) with a 440lb (200kg) warhead and a total weight of 2,072lb (940kg). The DB-3T (T – torpedonosyets, torpedo) was equipped to enable the missile to be dropped using either low or high torpedo bombing methods. In the first case the 45-36 AN low altitude aerial torpedo was dropped from 100ft (30m) at a speed of 198mph (320km/h). It was forbidden to drop the torpedo lower or higher because its casing could be cracked when it hit the water or it could sink too deep. Although low altitude torpedo bombing offered the highest probability of destroying the target, it demanded a high degree of piloting skill and good aircraft handling and manoeuvrability. In high altitude torpedo bombing the DB-3T dropped the torpedo from 1,000ft (300m). The missile was parachuted down, and when it touched the water it began to travel in a circle on the target’s course. In addition to its torpedo, the DB-3T could carry the usual bomb load, and could be used as a bomber or for dropping mines. It could also serve as a long-range naval reconnaissance aircraft.
Introduced into the USSR Naval Aviation inventory, the D8-3T became the first mass produced Soviet torpedo-bomber, fully meeting the operational requirements. On its technical basis a new aspect of Naval Aviation, Torpedo Aviation, was born in 1939-1940 for the destruction of enemy vessels by torpedoes and bombs, and also for mining enemy seaways and exits from naval bases.
However, the DB-3T could take off only from land bases, and sometimes these were not readily available, especially in the areas covered by the Northern Fleet. In 1938, therefore, a new version, the DB-3TP (Torpedonosyets Poplavkovyi – torpedo floatplane) was designed. The floats, taken from the Tupolev TB-1 P, naturally reduced the torpedo-bomber’s performance. During tests in the summer of 1938 at a normal flying weight of 16,644lb (7,550kg) and carrying a torpedo, the DB-3TP reached a speed of 213mph (343 km/h) at 13,100ft (4,000m), and its climb rate and service ceiling were also reduced. Even this performance met estimated requirements and was better than the Beriev MDR-5 and Chyetverikov MDR-6 flying-boats. The DB-3TP retained the type’s good handling.
Test pilot Sukhomlin assessed the seaplane thus: ‘The aircraft is well-produced as a torpedo-bomber and naval high-speed bomber. It is fully suited to these roles’. Nevertheless, the DB-3TP was not put into series production owing to operational complications. It was very difficult to load bombs, attach torpedoes and service the engines while the aircraft was on the water.
DB-3s in action
DB-3 regiments were used in combat missions against Nazi troops during the offence against Moscow, performing mostly tactical tasks. Crews of the 751 st BAR (from the complement of the 1st Heavy Bomber Air Division) distinguished themselves considerably, and the regiment was soon promoted to the 8th Guard Bomber Air Regiment. Their DB- 3Fs bombed the enemy in the regions of Maloyaroslavets, Rzhev, Vyazma and Yartsevo.
By 22nd October 1941 there were 439 bombers in Soviet Long Range Aviation units, of which 310 were DB-3s. By 15th December 1941 the figures had fallen to 273 and 182 respectively. The regiments continued to score successes, attacking enemy troop concentrations on roads and at railway junctions. As a result of a government resolution issued on 5th March 1942 the DB-3 regiments were reorganised. The units and regiments of long-range bombers were re-formed into the Aviatsiya Dal’nevo Deisviya (ADD – Long Range Air Arm), headed by General Headquarters under the command of General A Golovanov.
Work on the DB-3F continued in two basic directions: improving combat capability and increasing the quantity. In the 3rd BAR some versions of the Il-4 had their defensive weaponry bolstered by the installation of movable large calibre machine guns, which were successfully tested. In May-June 1942 an updated UTK-l turret with a UBT machine gun designed by I Shebanov had been fitted to production aircraft. The lower turret used on Petlyakov Pe-2 bombers could not be fitted because it upset the aircraft’s cg. The gunners compartments were equipped with armoured shields. To retain the range, the normal flying weight of the four-seat version of the Il-4 was increased to 20,877lb (9,470kg), and the fuel capacity was increased by 1,157lb (525kg) by the use of two external tanks suspended on the bomb rack mountings. The maximum speed decreased at all altitudes by 3.1 to 6.2mph (5 to 10km/h), the rate of climb dropped by 40% and the service ceiling by 3,600ft (1,100m) – all of these figures were compared with the prototype, built in 1940. This performance was regarded as satisfactory for night flights, and, moreover, the aircraft’s range according to the tests proved to be 2,361 miles (3,800km). However, this figure corresponds not to the cruising speed of the DB-3F, but to economical speed.
During the Second World War the production aircraft were fitted with M-88Bs, which had the same power as the earlier M-88 used before but were more reliable for long range missions. The engines had a service life of some 150 hours. The evacuation of Engine Plant No. 29, which was producing M-88Bs, and some difficulties connected with their production at a new location, made it necessary to use engines of other types. At the aircraft factory in Komsomolsk-on-Amur test pilot Galitsky spent a long time testing a production Il-4 powered by M-82s, which were more powerful and, consequently, heavier. The aircraft’s weight increased to 19,510lb (8,850kg), 1,801lb (817kg) heavier than the prototype, built in 1940, under the same loading conditions. Its maximum sea level speed was 235mph (379km/h), and its speed at altitude was 271mph (437km/h). The rate of climb and service ceiling increased as well, but cruising range fell to 1,578 miles (2,540km). However, all the difficulties with M-88B production were eventually overcome, and series production was resumed. This engine was more reliable than the M-82, M-89 and M- 90 (though there were attempts to power the Il-4 with these engines).
Ilyushin bombers had suffered no losses on the ground because the Luftwaffe made no raids on airfields in the Soviet rear. In the morning of 22nd June 1941 WS Commander-in-Chief of the Red Army General P Zhigarev set the 3rd Bomber Air Corps the task of annihilating the enemy troops in the region of the Suvalkin salient. The first bombers to take off belonged to the 207th BAR, led by their commander, Lieutenant-Colonel G Titov. On the next day the DB-3s had to attack Konigsberg, Danzig and Warsaw.
Subsequently, ADD’s main forces were ILYUSHIN used against the enemy’s motorised infantry, which had penetrated the front line. The DB- 3s fought hard, but suffered heavy losses. For example, on 26th June 1941 43 DB-3F crews failed to return from their missions, mainly owing to bad planning and organisation of the raid. The bombers had no escort fighters at all, and were therefore obliged to fly at low altitudes, where the anti-aircraft fire was intense. The German command noted that the DB-3 was almost as fast as the SB but was harder to shoot down. The pilot was protected by an armoured backrest and the fuel tanks were similarly protected, and the aircraft had a more robust structure and was more fire-resistant. Attention was also drawn to the fact that all of the bombers had lower hatch machine guns and could carry a crew of four. The additional gunner increased the DB-3’s defences.
An important task assigned to the DB-3 was the bombing of Berlin. The newspaper Pravda reported at the time: ‘On the night of 7th/8th August a group of our bombers performed a reconnaissance flight over German territory and dropped incendiary and high explosive bombs on military objectives near Berlin. As a result of the bombing some fires were started and explosions were seen. All of our bombers returned safely’.
It subsequently transpired that the air raid was performed by DB-3Ts of the 1st Mine-Torpedo Regiment of the WS Krasnoznamyonny Baltiiski Flot (KBf- Red Banner Baltic Fleet) under the command of Colonel E Preobrazhensky. From August, 12 DB-3Fs of a long-range aviation group commanded by Major V Schelkunov began flying missions to Berlin. An attempt was made to increase the bomb load (the total bomb load during the first flights was 1,763Ib/800kg) by suspending two FAB-500 or FAB-l 000 bombs externally, but the short take-off strip of the grass airfield in Kogul and the aeroplanes’ worn-out engines resulted in disaster. All subsequent flights were made with the standard 1,763lb (800kg) load. On 12th August 1941 the enemy detected the Soviet airfields and started bombing them. In addition, instruction No. 34 issued by Hitler that same day proclaimed, in particular: ‘As far as conditions allow, our aircraft must annihilate the military air bases on Dago and Esel islands. It is very important to destroy these airfields, which enable air raids to be made on Berlin’.
That order demonstrated once again the great psychological importance attached to the DB-3 and DB-3F missions. By that time long range aviation crews had started to fly at night, at high altitudes. From 10th July until 30th September 1941 DB-3Fs flown by Baltic Fleet and Black Sea Fleet crews delivered blows against objectives in Konigsberg, Danzig, Helsinki, Warsaw and Konstanza, among other targets. As a direct result of the 4th Bomber Air Corps’ attacks, the output of Rumania’s oil industry decreased by 30%.
One cause of alarm was the fact that the Soviet aircraft industry produced only 757 DB-3s and DB-3Fs during the whole of 1941. The production capacity of Plant No. 126 was totally inadequate, because as a result of its evacuation to Siberia there was nowhere to build the aircraft. Therefore, in March 1942, following a government decision, Il-4 production was organised at a factory in Fili (the plant was returned from Siberia and designated Aircraft Plant No. 23). The next responsible decision was to stop Pe-2 production in Irkutsk in favour of the Il-4. As a result, 858 aircraft had been built by the end of this year of great changes.
From the beginning of the autumn of 1941 a wooden navigator’s cabin, cockpit floor and tail fairing were installed on production aircraft owing to a shortage of Duralumin. The fourth crew member and the armoured protection for the gunner considerably displaced the aeroplane’s cg, upsetting longitudinal static stability and controllability. This was rectified in the machines built from the summer of 1942, which had a newly-developed detachable wing section with an ‘arrow’ along the leading edge which moved the cg. forward relative to the mean aerodynamic chord. The detachable part of the wing with the ‘arrow’ had a new aerodynamic profile which increased the relative thickness by 10%, and a composite structure of metal spars with wooden ribs and skin. The thicker detachable wing profile and the displacement of the lower ribs outside the skin (this structure formed a so-called ‘rib-skin’) permitted the installation inside the cantilevers of three protected fuel tanks instead of one, increasing the total weight of fuel by 2,502lb (1,135kg) compared with the production DB-3F. The aircraft’s flying weight also increased, being 26,741lb (12,130kg) in overloaded configuration, but the performance was sufficiently high. At a normal flying weight of 22,167lb (10,055kg) its maximum speed was 251mph (404km/h) at 22,000ft (6,650m). Because of the high fuel capacity, range increased considerably. With a normal internal bomb load of2,204lb (1,000kg) the aircraft had a range of 2,227 miles (3,585km) at 211mph (340km/h), and this could be increased to 2,650 miles (4,265km) if the speed was reduced to 155 mph (250km/h). A 21.5ft2 (2m2) increase in flap area meant that the aircraft was still able to operate from front line airfields despite the considerable increase in weight. Newly-developed AV-5F-158 propellers of greater diameter also contributed to this ability.
Thanks to the new wing aerodynamics, controllability and manoeuvrability were greatly improved. According to pilot assessments, handling with the ‘arrow’ seemed to be easier. The DB-3F had one very good feature; it could perform a long flight on one engine at a flying weight of up to 20,767lb (9,420kg). DB-3Fs of the structure described above were in action until the war’s end. To 1,528 DB-3s were added 5,256 DB-3Fs and Il-4s, the last 160 of which were produced after the war. Until the day of victory Il-4s formed the basis of the Soviet ADD, reorganised in 1945 into the 18th Air Army.
The most distinguished ADD pilots who flew DB-3s and Il-4s were rewarded during the war with the highest military decorations, and S Kretov, A Molodchy, E Fedokov, V Osipov and P Taran were made Heroes of the Soviet Union. Navigators and radio operator/ gunners were seldom given awards in the Soviet WS, but an Il-4 navigator, V Senko, was twice made Hero of the Soviet Union.
Variants
TsKB-26
Proof-of-concept prototype
TsKB-30
First real prototype. Later modified, including removal of armament, for long-range record attempts as the “Moskva”. It flew from Moscow to Spassk-Dalny (7,580 km (4,710 mi)) in 24 h 36 min (an average speed of 307 km/h (191 mph)) mostly at 7,000 m (23,000 ft) under control of Vladimir Kokkinaki and A. M. Berdyanskij, then from Moscow to Miscou Island (New Brunswick, Canada) in 22 h 56 min. covering 8,000 km (5,000 mi) at 348 km/h (216 mph) average airspeed (Kokkinaki and Mikhail Gordienko).
DB-3 2M-85
Initial production model
DB-3 2M-86 (DB-3A)
Engines upgraded to M-86, other minor changes
DB-3 2M-87A (DB-3B)
Engines upgraded to the Tumansky M-87A
DB-3T
Torpedo bomber built in 1938, with either the M-86 or M-87 engine, armed with 45-36-AN or 45-36-AV torpedoes.
DB-3TP
Seaplane torpedo bomber built in 1938. No production.
DB-3M
First major upgrade powered by two M-87B or M-88 engines.
