WesWorld

Took a stab at a basic planebuilder for the Avia B-135 since it's been mentioned.

The stats came off a website on 'great planes', so who knows. One site did say the Bulgarians only had 12, never did get the planned 20mm put in them, and used them as advanced trainers.

I Used maximum airspeed to trim light weight up and down-final is 362kts. Construction is 90%, Streamlining is per first flight. unstreamlined Crosssection is 50% of recommended not 38% to account for the boxy front look and scoop.



B135

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

Year of First Flight: 1938

Description

Carrier or Rough Field
Monoplane
Conventional Fuselage

Avia B-135. Within 1lb light weight, same max wt. As modeled 'clean' at 5,116lbs, -3mph from max and substantially slower climb. Placing weight at light 4,556, speed is +1mph and climb is within 11fps of listed. At both weights it flies higher than it should. Used 860hp and 12,000ft. Trying the Crs 848 and 13,100 of wiki, speed up but climb down.



Characteristics:

Weight (maximum) 5,435 lbs
Weight (empty) 4,305 lbs

Length 28.36 ft
Wingspan 36 ft
Wing Area 183 sq ft
Sweep 2 degrees

Engines 1
HS 12y-CRS
Piston

860 hp
at 12,000 ft


Crew 1


Typical cost $0.028 million in 1939
Total number procured 128


Performance:

Top Speed 298 kts = 343 mph
at 12,000 ft
Mach N/A

Operational Ceiling 31,250 ft

Range 508 nm = 585 miles
with 444 lbs payload
463 lbs released at halfway point

Climb 2,671 fpm

Cruise 210 kts = 242 mph
at 26,000 ft

Corner Speed 215 KIAS =
280 kts at 17,000 ft
Mach N/A
Turning Rate 23.0 deg/sec
Radius 2,356 ft



Internal Data:

Intake / Fan Diameter 8 ft

Bypass Ratio 80.75

Engine Weight 1064 lbs
Overall Efficiency 20 percent

Structural Factor 0.90

Number of Wings 1
Number of Fuselages 1

Limiting Airspeed 362 kts
Wing Ultimate g Load 9.00 g
Wing Taper 0.2
Wing Thickness at Root 1 ft

Tail / Canard Factor 0.4

Number of Nacelles 0
Length 23 ft
Diameter 3.4 ft
Fullness 0.4

Fuselage Diameter 3.5 ft
Fuselage Fullness 0.4

Pressurized Volume 0 percent
Cargo Decks 0

Cleanness 75.5 percent
Unstreamlined section 1.2 sq ft

User equipment 600 lbs

Same plane,

12Y-51 installed with 15,000ft supercharger.
Commentary on sim deleted.

B135

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

Year of First Flight: 1938

Description

Carrier or Rough Field
Monoplane
Conventional Fuselage

Characteristics:

Weight (maximum) 5,435 lbs
Weight (empty) 4,305 lbs

Length 28.36 ft
Wingspan 36 ft
Wing Area 183 sq ft
Sweep 2 degrees

Engines 1
HS 12y-51
Piston

1,080 hp
at 15,000 ft


Crew 1


Typical cost $0.029 million in 1939
Total number procured 128


Performance:

Top Speed 336 kts = 386 mph
at 15,000 ft
Mach N/A

Operational Ceiling 31,250 ft

Range 508 nm = 585 miles
with 437 lbs payload
456 lbs released at halfway point

Climb 3,463 fpm

Cruise 210 kts = 242 mph
at 26,000 ft

Corner Speed 216 KIAS =
281 kts at 17,000 ft
Mach N/A
Turning Rate 23.0 deg/sec
Radius 2,363 ft



Internal Data:

Intake / Fan Diameter 8 ft

Bypass Ratio 69.38

Engine Weight 1064 lbs
Overall Efficiency 20 percent

Structural Factor 0.90

Number of Wings 1
Number of Fuselages 1

Limiting Airspeed 362 kts
Wing Ultimate g Load 9.00 g
Wing Taper 0.2
Wing Thickness at Root 1 ft

Tail / Canard Factor 0.4

Number of Nacelles 0
Length 23 ft
Diameter 3.4 ft
Fullness 0.4

Fuselage Diameter 3.5 ft
Fuselage Fullness 0.4

Pressurized Volume 0 percent
Cargo Decks 0

Cleanness 75.5 percent
Unstreamlined section 1.2 sq ft

User equipment 600 lbs

I've never had much success with Planebuilder; I just stopped using it altogether, and rough in my stats (on the rare occasions I make up planes) or use some historical stats.

The loss of climb would be awkward, since I think that'd be one of the prime things I look for in a fighter-interceptor...

On the 12y-51 version, you may want to increase the diameter of the prop: I can't see getting a bypass that low without using a lot of propellor blades, and that's something that isn't really in period yet.

Hrolf : Normally I don't like dropping to the 60s, but I was trying to make a rough evaluation of the potential with 12Y-51, didn't want to be changed alot of things.

For that matter, I forgot to play with the manuevering tabs and landing tab on both versions.

Brock : The climb rate listed on wiki appears to be the light weight figure. As I indicated, dropping the sim version to light got a +11fps result. Pretty good.

As for using PB, you can get pretty darn good results in some cases. You can also push it to get unreasonable results.

It's also a caution when dealing with rates of climb, you have to ask 'for what weight'. My Dutch encyclopedia tends to list 'clean' not light, which makes my planes look worse.

Fair enough on the reasoning there, KK.

On climb rates, the Planebuilder sims I've done generally use half-range weight for things like service ceiling, rate of climb, max speed, etc. Essentially I'm trying to get a useful number for a combat aircraft, not a number for a record-breaker.

According to William Green planned armament was 1x20mm and 2x7,92mm

Here are the stats given:

Max speed: 535 Km/h @ 4000 m
Max initial climb: 13,4m/s
Max range: 940 km
Empty equipped weight: 2063 Kg
Max loaded weight: 2547 kg

Light vs. Clean : I agree with Hrolf, I like to know how my planes perform with fuel and ammo loaded, not in a light configuration. Hence my encyclopedia lists the 'clean' but rarely 'light' versions.

However it seems a number of planes I try match their real world counterparts a bit better in 'light', which would also be better for marketing.

Plane research : One of the annoying things about the B-135 is- despite the basically one model- there are different stats given.

I used this page Avia B-135

for dimensions and most info. It's got the same light weight Vukovlad provided, but a different max.
Same range, higher speed.
Engine listed is odd- the 12Ycrs is usually listed in the 840 range, not the 860, but I went with the 860.

The fun part is Wiki's post lists 860 also.. but when you click through to the -crs page, that lists 848 at 4,000m. Argh.

Ceiling and Rate of climb were not listed, so I looked to wiki.
Wiki is which is .1 greater on climb than Vukovlad's source. Wiki is also closer on speed, but has severely reduced range. Considering that Vuk's and the link above both say 940km, that may be correct.

The engine according to the previously quoted source is 860 Hp @ 4000 m and 800 @ sea level it also mentions that production wasnt initiated in Bulgaria due to lack of engines (~30 delivered out of 62 ordered) and none of the cannons delivered

I think I recall somewhere that the engine on the B-135 might have been slightly powered-up over the regular 12Y, but I can't find my source for it. Otherwise, the specs I wrote in my encyclopedia match what Vukovlad indicated.

That makes sense. The 12Ycrs was fairly widely used and near the beginning of the upgrade arc.

860 works nicely for hitting the higher speed of my link, but there are plenty of ways to keep 850 and yet degrade speed to the 332 mark via fuselage size, wing thickness, fuselage taper, unstreamlined cross section, etc. Those all being good ways to boost it was well.

As it was it seems a couple different means of upgrading it were tried, you actually see rated hp drop between two later models, while the Russians went with their own versions.

Anyhow it would seem that if the Czechs/Bulgarians wanted to persue it, the B-135 airframe can produce a reasonable next iteration fighter.

After that fitting heavier guns, armor, self sealing tanks, heavier engines and what not would likely require a new airframe or major changes to this one.

on whim, I checked cuil for B-135 and wound up with the military aircraft database, which lists a payload of 10x 20kg bombs. Or 200kg.

Looking at the PB sim, the max payload for range was 444lbs, or 202kg.

Accident, but fun

Oh, and leaving the bypass completely alone and popping the prop diameter to 9ft gives 1,088hp, almost the right figure for the HS 12Y-51

I have been thinking of a second generation Swallow, so how about this?

DAR 21 Ljastuvka II

It looks nice. I'd be making the rudder a bit taller, and the fuselage just a tad bit narrower, though, on aesthetic grounds... but I don't actually know what that'd do to the design besides make it look purty.

New engine for more power, cut down rear fuselage for better all round visibility. Another upgrade could be an all metal construction

Now with a larger fin

Dunno. Something just looks odd still. Like an Avia with an infant Yak-9 inside, trying to get out...

Well its just a suggestion, the B.135 small hood over the cockpit gives it a peculiar look

Quoted

Originally posted by Vukovlad
Well its just a suggestion, the B.135 small hood over the cockpit gives it a peculiar look

That's true. Can you try a different canopy, more like the Mustang bubble?

Another possible engine for this aircraft would be the DB-601 series, which (starting with the DB-601Aa) has been modified to allow for mounting a machinegun or cannon between the cylinder banks. The Luftwaffe hasn't ordered any aircraft with that setup, but prototypes of the Bf-109C (armed with 3 15mm MG-151s) have been built and flown.