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We will get soviet modification of A-20B:
Bomb bay 16x100kg
Underwing fittings 4x100kg
Confirmed by Viks on russian forum
Bit of history of soviet modifications I put together from sources available to me.For those interested.
Original US DB-7 had only 4 fittings inside bomb bay greatly reducing bombload when smaller bombs or mix were to be fitted. Usage of domestic bombs was also problematic.
Soviet Zavod 43 came with a technical solution approved by Chief Engineer of VVS 20.7.1942. This was for DB-7b/c and A-20C variants delivered as first to USSR.
List of changes:
1. Installation of bomb boxes KD-2-439 into bomb bay = 2x front and 2x rear part of it. Each bomb box for 4x100kg bombs.
2. Electrical bomb release trigger ESBR-3p
3. Bombsight OPB-1 (daylight) and NKPB-4 (night) which replaced rather primitive original Vimperis D-8 type.
In autumn 1942 a larger volume of A-20Bs has been released by US for land-lease purposes. The reason was simple. Same as earlier models,also these were found not fit for combat duties due to lack of armor protection and selfsealing fuel tanks. 2/3rds (665) were shipped to USSR,the rest was kept in US for training purposes .
A-20B soviet modification:
1. Installation of domestic bomb boxes with Der-21 bomb fittings into bomb bay for 16xFAB100kg bombs
2. Installation of outer wing bomb fittings Der-19p for bombs up to 250kg
3. Electrical bomb release trigger ESBR-6
4. Bombsights OPB-1r and NKPB-7
Thanks to Der-21 bomb boxes A-20B could carry large spectrum of other specialised bombs like Containers KMB-Pe-2 with small explosive bombs AO-2,5 ,AO-10,AO-25, incendiary ZAB-2,5
For outer wing fittings Der-19p it was possible to install VAP-250 chemical dispensers (white phosphorus)
Max load of bombs was set to 2000kg while taking off from concrete runways. For operations from field conditions,the bombload was usually smaller (depending on airfield conditions)
Concerning UTK-1 gunner turret,it could be installed on few machines in time of Kuban battle (with original Browning 12.7,not UBT) but there is only one source available to me. It was request of VVS deputy commander G.A.Vorozheykin to NKAP to modify urgently 54 A-20Bs dated 30.10.1942. No proof it has been also carried out. Bostons were usually put into action immediately after arrival and there was little time to send them for extensive modifications. That was possible only in late 1943,when US started to deliver A-20Gs,which fulfilled USSR requests much better then previous models.
And not to forget,soviet A-20Bs had additional 4th crew member - rear low gunner.Planes were fitted with additional seat,oxygen connection and intercom for him allready in Tulsa,USA . Tulsa served as "mod shop" for Bostons heading to USSR were all changes requested by soviet side were installed. Under supervision of soviet officials,who also made final inspection.
Its more about soviets considering US bombload limits rather "too conservative".
And first DB-7s (Boston III) had limitations of only 4 bomb fittings inside bombay which at the end limited your bombload to max 4x227/250kg. If soviet commander needed 100kg FAB bombs for the mission,well,only 4 could be fitted inside bringing your max load down by half.
Thats why soviets installed their domestic systems increasing the bombload .And more importantly,it gave more flexibility to the bomb mix the plane could carry.
1. Bomb bay only FAB100 bombs (16x)
Outer wing mounts (4x) max FAB250 bombs
2. It had some armor protection from factory but it was considered subpar acc. US standarts in 1942 for attack cathegory. For soviets it was light tactical bomber. They did some improvements on armor in Zavod nr.81. I dont have more details on that. They also modified the plane for winter usage by adding removable engine covers with adjustable jalousies(simmilar like on ishaks) manufactured by Zavod nr.2