WesWorld

Avia offerings.

Last fall I said I would work up some new Avia planes for the NPCs to access. That free time didn’t work out as expected, so that didn’t happen.

I expect Avia would see market demands and develop planes in 1938-41 for the following :

Interceptor :
After the success of fast raiding bombers in the South American war, a high speed, fast climbing, heavily armed interceptor may be in demand.

Fast Bomber :
While engines are expensive, fast bombers may also be desired. Borrowing a page from the Italians and fielding a trimotor bomber. I had this mental concept of a C-47 skytrain with a slimmer central fuselage with the 3rd engine mounted behind. Wound up trying to use a B-26 fuselage with the C-47 wings and booms. I put a 20% penalty on pushers, but the result was still capable of delivering 2 tonnes over long distances at high speeds positions Avia to meet this market.

General fighter :
Building on the success of the prior two fighters, there would seem to be a role for a general air superiority fighter.

General bomber :
As more traditional purchasers may still want a twin-engine higher capacity slow bomber, that would be designed as well. This may be a conversion from a civilian airliner as they have done in the past.

Dive bomber :
Obviously a hole in the Avia line up. The ability to absorb ground fire would be necessary in such a machine.

Transport :
The Fokker Arend was designed for muddy fields on the KLM route to Asia, and a licensed version would make sense for many potential markets.

So I’ve got the first 3 mostly done, and thought I’d pause for conceptual comments on what folks thought Avia should be offering in 1941-42. Desired ranges are a particular sticking point- what do folks want? I’ve given the fast bomber a 1,242mi/2,000km range at 316mph/510kph, the interceptor a 557mi/897km range at 345mph/556kph, and the fighter a 621mi / 1,000km range at 247mph/400kph.

I figure the next step is to post plane summaries, my modeling parameters, and the planesharps. Figured I'd pause for comments.

Just checking - there were some Fokker-Avia craft mentioned here; I am presuming they're the aircraft meant by the General Fighter and General Bomber requirements?

I was figuring the general fighter would be a 1941 follow on to the B-139.

I had presumed the B-158 was earlier, 1938 was the OTL year, while we are +3 here, so I would have expected it to be a 1935 bird in Wesworld. So the 'general bomber' was to be the follow on to that, so I expect it will also be a 1940-41 bird- lots happened in 3 years of airplane development.

Ah, I see.

My excel files are at work= but as I recall, what I have now is an interceptor that makes 429mph, with 3x20mm, The fighter is a radial beast like the FW190 which I fiddled with so it just made 400mph- figuring that would be a marketing point. The fast bomber currently cruises near 300mph with 4400lbs of bombs, but I think I need to work on the fuselage cross-section and take some length off- which may balance out.

I'll see if anyone else has anything to add before I continue tomorrow.

Looks interesting Kirk.

I admit I didn't go far ahead with + years to avoid fielding super-export machines too early and to reflect a second-tier power.

I think a fast bomber makes sense, as does the interceptor while the general types are going to be good for both home and export use.

I try to avoid making "world beating" aircraft in the first place. I did figure out how to make Planebuilder give me the numbers if I wanted them, but that's just trying to understand it. The G-1s were still slower than the FW-189, I think the closest I've done was the D.XXIII, and I derated that

Generally with Avia, I was using +1 or +2 as the date. The goal is to allow folks who have smaller nations/NPCs access to competitive, but not dominant, equipment.

We'll go ahead and leave the B.158 in as a light bomber.
Probably means I should generate another in 1942 or so.

So this is the series I'm looking at - tell me if a date doesn't line up :

Please note that I simply don't understand Avia's naming system. BH seems to be wooden, while B was metal, but what S was for..unless German, I dunno. So I decided fighters were B.130-149, Bombers B.150-170, Transports B.90-100.

Avia Planes

1935
B.135 Fighter

1936

1937
B.137 Fighter
B. 90 Transport

1938
B.158 Light Bomber
B.159 Dive Bomber

1939
B.139 Fighter
B.161 Fast Bomber will have to do from work


1940
B.142 Interceptor will have to do from work


1941
B.144 Fighter

Planebuilder Simulation

At home, I use Openoffice, which chokes and corrupts on Planebuilder. So I used to make the 4-6 min commute to work and use Excel 97. But we've upgraded to Office 10, which keeps complaining about the circular references in the climb and maneuver tabs and refusing to update sheets as a result. So there won't be any climb/maneuver information.

So the Dive bomber and transport are “draft” as the speed sheet corrupts when I try to find max speed. So I need to port them down to work and see if I can get final speeds there.

Summary
First flight : Year before production.

Powerplant :
In Wesworld, in the early 1930s Avia took to license building Bristol Engines of the Mercury, Pegasus and Hercules lines, while Hispano-Suiza engines were imported. During the mid 1930s, a partnership was formed with Minerva of Belgium for aviation engine development, and a Minerva factory was tasked with production of inline engines, Minerva being well know for their high quality sleeve-valve Knight Engines.

The result is the early 1930s engines will be Bristol/Hispano-Suiza, or rebranded clones. While later engines will be new designs to fit weight classes using appropriate pwr/weight ratios.

Superchargers for Avia are still at 4-5000m

Pusher engines are treated as 0.8 engines, as the airflow reaching them is already disrupted by the aircraft, rendering them somewhat less efficient in most cases. Or so I've read.

Airframe [u]
Max Design Airspeed : Generally higher than Max airspeed, but not always, as at altitude Indicated Air Speed is substantially less. Keeping this as low as possible is one way to design a plane with remarkable “stats”.

Wingloading : This figure is at max weight.
Wing root thickness: Needs to be 0.9-1.2 + for wing mounted guns.
Service limit G : around 6 G is about the max for pilots & gear in this era. Excess “G” allows future growth, as spar box weight can be held the same, and G can be reduced as plane max weight to be increased

Fuselage length : I generally want at least 3x+ wing chord, and I add length for inlines / gunners.
Fuselage diameter : Should equal or exceed engine diameters. Minimum seems to be about 3.4feet to accommodate pilot, 3.7 for comfort and elbow room.

Fullness : I usually use 0.3 for fighters and more for others. Occasionally less. The Sample PBY-5 had a “0” which I just don't get. For Nacelles, I tend to use 0.

Cleanness : First Flight year +3 = Cleanness year. This reflects Avia's access through Fokker to first class wind tunnels.

Unstreamlined cross section : Back when I did a lot of these, the wisdom was this represented radials, and you could reduce it for in-lines. I wound up using a 0.38 multiplier. However, as P:W improves, speeds for inline planes creep out of reasonable bounds. So I have discontinued use of this.

Also, past discussions with Hrolf led to the conclusion that Planebuilder seems to model historic radials very well, probably including oil cooling in the miscellaneous weight, but the in-line engine coolant weight is nowhere accounted for. So to give them a double advantage seems off, and the lack of the multiplier is used to offset the missing coolant.

So.. I use the cross section that accords to the engine power when the engine is introduced.

User Weight :
I use 84lbs for 20mm, sometimes reducing weight for motorcannons as they used the engine to absorb some recoil, 37lbs for 13.2mm, and 24 (?) for 7.92mm guns. For fighters, ammo weight is often doubled (to 250rpg for 20mm, and 600rpg for 13.2mm) and I used to include it Userweight. Self-sealing tanks are assigned a weight of 1.184lbs/gallon.

Edit : I derive gallons from Airframe L78 "Max Fuel Capacity" multiplied by Range G19 "Required Fuel Faction". Then multiply that by the 1.184.

I have a figure for ejection seat weight (150kg?)somewhere, but they only get used on the D.XXIII series.

Edit : I've modified the base planebuilder Airframe sheet to simply display and sum some of the above weights for me, and then I put that number in the userweight.

Payload : Self explanatory, but should be realized Ammo is payload, so bombload is less.

Range : Figures at full weight
Climb : Figures at light weight *
Speed : Figures at light weight *
Maneuvers: Figures at light weight *
Landing Speed : Figures at light weight *

* I should note that on my Fokkers I used to do all these at “max” weight, and then was piqued as they got compared to other's planes which were obviously stripped down to a couple gallons for the test.

PLANEBUILDER - Aircraft Specification Sim: Beta v. 1.4

Aircraft Type or Name:

Avia B.90

General Type:
Airplane = 1
Airship = 2
Orbiter = 3
1

Year of First Flight: 1936

Description

Carrier or Rough Field
Monoplane
Conventional Fuselage

An adaption of the plan for the Fokker F.36A airliner/transport. Manufactured with heavier framing. Converting from a 4-nacelle to a trimotor and installing Bristol Hercules I engines. with a ¾ cargo deck.


Characteristics:

Weight (maximum) 39,684 lbs
Weight (empty) 23,712 lbs

Length 77.42 ft
Wingspan 108 ft
Wing Area 1,850 sq ft
Sweep 2 degrees

Engines 3
Hercules I
Piston

1,250 hp
at 13,123 ft


Crew 3


Typical cost $0.127 million in 1942
Total number procured 120


Performance:

Top Speed 205 kts = 236 mph
at 9,000 ft
Mach N/A

Operational Ceiling 25,000 ft

Range 1,200 nm = 1,382 miles
with 7,517 lbs payload
8,374 lbs released at halfway point

Climb 1,715 fpm

Cruise 170 kts = 196 mph
at 13,123 ft

Corner Speed Err:523 KIAS =
Err:523 kts at 9,000 ft
Mach Err:523
Turning Rate Err:523 deg/sec
Radius Err:523 ft



Internal Data:

Intake / Fan Diameter 8 ft

Bypass Ratio 67.05

Engine Weight 1929 lbs
Overall Efficiency 22 percent

Structural Factor 0.95

Number of Wings 1
Number of Fuselages 1

Limiting Airspeed 230 kts
Wing Ultimate g Load 6.00 g
Wing Taper 0.3
Wing Thickness at Root 3.5 ft

Tail / Canard Factor 0.4

Number of Nacelles 2
Length 8 ft
Diameter 4.7 ft
Fullness 0.4

Fuselage Diameter 6.48 ft
Fuselage Fullness 0.6

Pressurized Volume 0 percent
Cargo Decks 0.75

Cleanness 72 percent
Unstreamlined section 11.5 sq ft

User equipment 0 lbs


disclaimer
Draft: max speed, ceiling subject to improvement.

Aircraft Type or Name:

Avia B-159

General Type:
Airplane = 1
Airship = 2
Orbiter = 3
1

Year of First Flight: 1938

Description

Carrier or Rough Field
Monoplane
Conventional Fuselage

Hypothetical Avia dive bomber. Expecting rapid short range sorties, a radius of 185nm leaves a 25% reserve. 4x13.2mm fore, 1x13.2mm aft. 1.75x10mm armor disk (forward arc, windshield, aft), Pilot/rear Gunner, provision for up 5 bombs (modeled as nacelles) up to 500kg payload. A slightly oversized tail is provided in hopes of fine-tuning the dive.



Characteristics:

Weight (maximum) 10,100 lbs
Weight (empty) 7,411 lbs

Length 29 ft
Wingspan 41 ft
Wing Area 289 sq ft
Sweep 3 degrees

Engines 1
Hercules II
Piston

1,375 hp
at 13,123 ft


Crew 2


Typical cost $0.043 million in 1942
Total number procured 120


Performance: Edited 3/4/12

Top Speed 284 kts = 327 mph
at 13,123 ft
Mach N/A

Operational Ceiling 34,000 ft

Range 463 nm = 533 miles
with 1,371 lbs payload
1,430 lbs released at halfway point

Climb 2,019 fpm

Cruise 190 kts = 219 mph
at 13,123 ft


Corner Speed Err:523 KIAS =
Err:523 kts at 3,281 ft
Mach Err:523
Turning Rate Err:523 deg/sec
Radius Err:523 ft



Internal Data:

Intake / Fan Diameter 8 ft

Bypass Ratio 62.93

Engine Weight 1929 lbs
Overall Efficiency 22 percent

Structural Factor 1.00

Number of Wings 1
Number of Fuselages 1

Limiting Airspeed 350 kts
Wing Ultimate g Load 9.00 g
Wing Taper 0.2
Wing Thickness at Root 1.4 ft

Tail / Canard Factor 0.44

Number of Nacelles 5
Length 5 ft
Diameter 2 ft
Fullness 0

Fuselage Diameter 4.7 ft
Fuselage Fullness 0.4

Pressurized Volume 0 percent
Cargo Decks 0

Cleanness 86 percent
Unstreamlined section 2.9 sq ft

User equipment 1,478 lbs

Aircraft Type or Name:

Avia B-144

General Type:
Airplane = 1
Airship = 2
Orbiter = 3
1

Year of First Flight: 1940

Description

Carrier or Rough Field
Monoplane
Conventional Fuselage

Hypothetical Avia general purpose fighter for 1941. 1 x 20mm cowling, 4x 13.2mm MG, 10mm disk armor x 1.5, self-sealing tanks. Double Ammo - 250rpg 20mm, 600rpg 13.2mm, 2x50kg Bombs



Characteristics:

Weight (maximum) 8,350 lbs
Weight (empty) 6,835 lbs

Length 26 ft
Wingspan 34 ft
Wing Area 239 sq ft
Sweep 3 degrees

Engines 1
Avia-Minerva Hercules VI
Piston

1,630 hp
at 16,404 ft


Crew 1


Typical cost $0.045 million in 1941
Total number procured 120


Performance:

Top Speed 353 kts = 406 mph
at 16,404 ft
Mach N/A

Operational Ceiling 39,000 ft

Range 540 nm = 622 miles
with 515 lbs payload
539 lbs released at halfway point

Climb 3,030 fpm

Cruise 215 kts = 247 mph
at 16,404 ft

Corner Speed #N/A KIAS =
#N/A kts at 3,281 ft
Mach #N/A
Turning Rate #N/A deg/sec
Radius #N/A ft



Internal Data:

Intake / Fan Diameter 8.5 ft

Bypass Ratio 62.75

Engine Weight 1929 lbs
Overall Efficiency 23 percent

Structural Factor 1.00

Number of Wings 1
Number of Fuselages 1

Limiting Airspeed 425 kts
Wing Ultimate g Load 9.50 g
Wing Taper 0.2
Wing Thickness at Root 0.9 ft

Tail / Canard Factor 0.4

Number of Nacelles 0
Length 1 ft
Diameter 1 ft
Fullness 0.8

Fuselage Diameter 4.7 ft
Fuselage Fullness 0.3

Pressurized Volume 0 percent
Cargo Decks 0

Cleanness 90 percent
Unstreamlined section 2.9 sq ft

User equipment 1,450 lbs

Looks good so far. Those planebuilder tips are ace. Maybe we should out those somewhere stickied so everyone can find them?

How many passengers will the B.90 carry?
The B.159 looks very good.
The B.144 looks good but I don't think the Hercules allows the use of a motorcannon. I might be wrong but most radials seem not to have hollow-shafts to allow cannon barrels.

Planebuilder - I'm pretty solid about what I posted, but there are others with more aviation knowledge that should have final say - RA/DF for two.

B.90's :
fitted as a cargo transport right now. Given the spare payload, it should hold the same 32 people + luggage as the Original F36A Arend, though the trimotor set up should make it much noisier in the fuselage. Still, if it's troops or equipment you're moving it should be good.

Compared to the F36 it's slightly lheavier, but still has very low wingloading for very bad fields- hence the low landing speed.

B.144
You're correct, originally it was to be in-line, but I decided Avia would want to have separate engine supplies from the B.139 Fighter / B.142 / B.161 - all inline recent models.
Anyhow, there wasn't a weight deduction in this case, so it just becomes a cowling 20mm.

B.159 - It's a bit heavy/pricey is my only concern. I was thinking perhaps Avia would try for minimalist DB - 3MGs, 500lb payload, no armor. However this is well rounded, Yugoslavia can hit Rome, Persia can hit the Saudi Coast, i.e. range is good.

However that concern - price/ market demand - is why I wanted to have a conversation thread rather than a "heres the new Avia thread"

Aircraft Type or Name:

Avia B.161

General Type:
Airplane = 1
Airship = 2
Orbiter = 3
1

Year of First Flight: 1938

Description

Carrier or Rough Field
Monoplane
Twin Fuselage

Fokker-Avia Interceptor for 1940. Engine : Minvera-Avia 3x HS-12Z 92 octane analog 1600lb/1500hp, 2 puller, 1 pusher producing 2.8hp, Pusher mounted flush with the upper fuselage. Fuselage blends upwards, with bottom turret at knuckle, clearing prop aft, 4 cheek 13.2mm, 2 turrets with 2x 13.2mm, 10mm armor before/aft of pilots + windscreen (20mm disk), double ammo,



Characteristics:

Weight (maximum) 29,212 lbs
Weight (empty) 17,345 lbs

Length 35 ft
Wingspan 50 ft
Wing Area 649 sq ft
Sweep 2 degrees

Engines 2.8
Minerva-Avia III (HS 12Z)
Piston

1,498 hp
at 16,404 ft


Crew 6



Typical cost $0.125 million in 1942
Total number procured 120




Performance:

Top Speed 312 kts = 359 mph
at 16,404 ft
Mach N/A

Operational Ceiling 36,000 ft

Range 1,080 nm = 1,244 miles
with 4,984 lbs payload
5,518 lbs released at halfway point

Climb 2,737 fpm

Cruise 275 kts = 316 mph
at 16,404 ft

Corner Speed 241 KIAS =
252 kts at 3,281 ft
Mach N/A
Turning Rate 24.9 deg/sec
Radius 1,956 ft



Internal Data:

Intake / Fan Diameter 8 ft

Bypass Ratio 61.23

Engine Weight 1714 lbs
Overall Efficiency 23 percent

Structural Factor 1.00

Number of Wings 1
Number of Fuselages 2

Limiting Airspeed 400 kts
Wing Ultimate g Load 6.00 g
Wing Taper 0.2
Wing Thickness at Root 1.6 ft

Tail / Canard Factor 0.42

Number of Nacelles 1
Length 28 ft
Diameter 5.4 ft
Fullness 0.3

Fuselage Diameter 3.7 ft
Fuselage Fullness 0.1

Pressurized Volume 0 percent
Cargo Decks 0

Cleanness 86 percent
Unstreamlined section 5.9 sq ft

User equipment 2,500 lbs

Aircraft Type or Name:

Avia B.142

General Type:
Airplane = 1
Airship = 2
Orbiter = 3
1

Year of First Flight: 1939

Description

Conventional Aircraft
Monoplane
Conventional Fuselage

Fokker-Avia Interceptor for 1940. Engine : HS-12Z clone , 1x motorcannon 20mm, 2x20mm, 2x 13.2mm, 10mm armor + windscreen (15mm x disk), double ammo, high cruise for 800km range, prepared airfield.



Characteristics:

Weight (maximum) 7,055 lbs
Weight (empty) 5,705 lbs

Length 29 ft
Wingspan 31 ft
Wing Area 157 sq ft
Sweep 2 degrees

Engines 1
Minerva-Avia III (HS 12Z)
Piston

1,498 hp
at 16,404 ft


Crew 1


Typical cost $0.030 million in 1935
Total number procured 240


Performance:

Top Speed 371 kts = 427 mph
at 16,404 ft
Mach N/A

Operational Ceiling 40,000 ft

Range 484 nm = 557 miles
with 446 lbs payload
468 lbs released at halfway point

Climb 3,439 fpm

Cruise 300 kts = 345 mph
at 16,404 ft

Corner Speed 312 KIAS =
325 kts at 3,281 ft
Mach N/A
Turning Rate 30.0 deg/sec
Radius 2,100 ft



Internal Data:

Intake / Fan Diameter 8 ft

Bypass Ratio 61.23

Engine Weight 1600 lbs
Overall Efficiency 23 percent

Structural Factor 1.00

Number of Wings 1
Number of Fuselages 1

Limiting Airspeed 450 kts
Wing Ultimate g Load 12.00 g
Wing Taper 0.2
Wing Thickness at Root 0.9 ft

Tail / Canard Factor 0.42

Number of Nacelles 0
Length 1 ft
Diameter 1 ft
Fullness 0.8

Fuselage Diameter 3.7 ft
Fuselage Fullness 0.3

Pressurized Volume 0 percent
Cargo Decks 0

Cleanness 89.5 percent
Unstreamlined section 2.9 sq ft

User equipment 1,514 lbs

Apparently restarting the work computer cleared the cache of it's memory that PB had a problem, as it's much more cooperative today.

So fixed the max DB and fighter speeds.

Wingloading can be deduced from the summaries as wing area, max and light weight are all given.


B. 90 Transport
Wingloading empty : 16.9
Wingloading loaded : 21.5


B.159 Dive Bomber
Wingloading empty : 31
Wingloading loaded : 35



B.161 Fast Bomber
Wingloading empty : 37
Wingloading loaded : 45



B.142 Interceptor
Wingloading empty : 44
Wingloading loaded : 45


B.144 Fighter
Wingloading empty : 34
Wingloading loaded : 35

When the discussions done, I'll craft the traditional short summaries of the various AC.

I suppose I should note since most of these engines can be boosted in HP as later marks/higher octane, so if the designs are too slow, that can be partially addressed.

The B.161 certainly seems radical. What's the 2.8 engines for in the report, wouldn't a straightfoward 3 be better? My visuals of the B.161 is something like the XB-42 but with wing nacelles.
It seems a rather technical bomber, its fast but seems a bit complicated. A twin-engined type might be better suited to the Czechs and allow better defensive arcs. Perhaps fewer crew too, say four with two turrets.

Reasonable points Hood,

to answer :

Quoted

Originally posted by Kaiser Kirk

Fast Bomber :
While engines are expensive, fast bombers may also be desired. Borrowing a page from the Italians and fielding a trimotor bomber. I had this mental concept of a C-47 skytrain with a slimmer central fuselage with the 3rd engine mounted behind. Wound up trying to use a B-26 fuselage with the C-47 wings and booms. I put a 20% penalty on pushers, but the result was still capable of delivering 2 tonnes over long distances at high speeds positions Avia to meet this market.

As I mentioned in the planebuilder notes, I accord pusher engines 0.8, hence the 2.8 engines.
The other alternative is to put 3 engines down, then modify the horsepower to 2.8x full, which is the approach I took back with the D.XXIII.

As for why the trimoter instead of a simple twin engine- the idea is to make a very fast bomber that allows minimum intercept time.

Here, design parameters become the problem-

1) what's the desired gun loadout ?... well I decided 1 top/1 bottom turret for minimal defense and some check guns for strafing. Add in a little armor and self sealing tanks, ammo and you're at 3000 lbs. Pilot,Co-pilot, Engineer/Radio, bombadier/nav, 2 gunners = 1500lbs. So we're at 4,500 lbs.

2) What's the desired delivery ? I thought 2 tonnes sounded like an attractive payload.

3) How far can should it deliver that? I figured a good marketing angle was 2,000kg at 1,000km. True that works out less with reserve, but it looks good on a flyer.

4) Can't run the engines full out for a 2000km round trip, though I understand "cruise" can be pretty high power. So 275knt cruise..which means bigger fuel tanks, but does cut down on intercept time, and on short hops you have fuel reserve to ramp that speed up.

Those parameters would be a pretty hefty plane for a twin. As there are limits on the power of the engines Avia has available, and their superchargers aren't up to 25,000 feet, to have those parameters and field a fast bomber required more power.

2 more nacelles and 4 engines= more drag. But the conventional fuselage already has drag without adding power. So revert to a trimotor to generate more power for minimal drag and weight. But you want the bombadier up front. So let's stick the engine in the rear.

Well now you need to do something with the tail...

It's really not that fancy a design, especially with Fokker's and Praha's twin boom experience to draw on. The only mental gymnastics was trying to figure out how to shoot rearward without hitting the propeller disk. By specifying the engine is flush with the top of the fuselage, that ensures the propeller arc is clear of the bottom turret. I should have sketched it out, as with the typical oval fuselage, they may clear with it in the center. ... anyhow The twin booms have a bonus here in giving a clear arc directly astern.

So..at the end of what got to be long.. this is the point of asking what the market is looking for. In South America, we saw fast penetrating bombers have some success.

If this is too big, I could go with a smaller twin engine bomber, with whatever bombload it can carry. I can probably ditch 2 crew if needed, which saves 500, etc.

So...what should I be aiming for with this bird???

edit : I should note that the use of 4,000m & 5,000m superchargers has a pronounced effect on max speed. Higher air is thinner air, so the higher you can manage max HP, the better stat-wise. An example of the difference is the hypothetical Atlantic-Aircraft BA-10W seaplane fighter, zipping along at 311mph at 16,404feet, but managing 339mph if it can achieve full HP at 19,684. Of course most threats in the naval realm can be expected to fly under 4 miles high, so 311mph is very respectable for something with big-*** floats.

There is certainly logic in the design. You make the case for three engines very well and yet for some reason OTL tri-motors were very rare. As you say finding room for the third engine is problematic. The layout you've described fit well with the Arado E.340 with of course an engine instead of a gunners position. This raises the possbility of a Germanic layout; pilot and bomb-aimer, navigator and radio-operator behind them with two turrets (dorsal and ventral) right behind the cockpit area. That allows a streamlined nose and the rest of the fuselage for the bomb bay and fuel tanks.

Future bombers are tricky to second-guess. As GB player I've introduced the Bristol Buckingham and the Mosquito. The Buckingham is perhaps the last of the traditional medium bombers with turrets and gondolas etc. The Mosquito is a fast unarmed bomber, still a radical idea and as yet untried. Brock is going for a Ju-388 type bomber so the traditional twin-engined medium is still around. There has been no real fighter versus bomber combat since 1935, then planes like the Vanquish and the I-100 were legion. Today both look outdated in performance.

I see your minimum defence as about right, nose, dorsal, ventral. Now the unarmed bomber theorists would argue that stripping the guns out and the gunners saves you weight and size. We know from hindsight the Mossie works well but IC we cannot be sure that defensive fighter forces won't be superior and able to catch the Mossie (given 3+ tech this is probably more likely).

As to markets; what about the Czechs? What would they want to re-equip their force with? South America is a possiblity, SE Asia is another likely export market too. I'd be interested to see what other folks have in mind.