Could you have designed a better Warbird?

Burmese Bandit said:

No.

I am going to, however...but there is just so much to do IRL.

Still, it's coming along!

Click to expand...

Good; it'll be great to see when you're done!

Venganza

A point on engineering, DelCyros...

If I understand your ideas and your schematic correctly, the power output from your engines will have to make a 90 degree turn in the fuselage when exiting the engine, and another 90 degree turn in the wings when moving to power the propellers. That means two, not one gearboxes per engine. Or am I wrong?

Furthermore you said that in the case of failure of one engine, the other engine will drive both propellers. In my mind that implies another gearbox...to coordinate the two engines...

Isn't that just a teensy-weensy bit too complicated? HE 177 engines begin to spring to mind...and even if if would work, shouldn't you add a loss of 5% more at least to each engine, for the extra gearboxes?

Remember, although I do know something about engineering, | am not one by profession. Do point out my errors if I have made a mistake!

Hi,

I'd prefer to locate the planes from BBandit delycros as a genuine German WWII: pieces of an over-engineering. Many good attack planes did a fine job being of a plain-vanilla 2 engine machines. Soren just beat me about the issue of cooling of an burried air-cooleed engine, and the 5-engine Hs-129 is an exagerration, to put it mildly. Plus, the hull-mounted engines from the proposals will either hamper the cannons ammo installation, fuel tankage, not to mention engine gearboxes' maintenance.

My proposal is based at Do-17 airframe, crew reduced to 2, armor for the crew, standard and non-strategic Bramo engines, the cannon armament* ammo in the bomb bay, hard points for bombs rockets. Defensive armament would've ranged from MG-81Z, across the MG-131 barbette from Me-410 to the 20mm barbette from a Ju-187 proposal.

*From MG-C30L, captured HS-404, through MK-101/103 and BK-3,7, up to 7,5cm.

Only one gearbox is needed. The shematic known from Blume´s work on remote powered props show four aspects:

Drucklager-
Kupplung-
Getriebe-
Antriebe-

The Drucklager transfers power from engine shaft into the gearbox via Kupplung. The gearbox controlls reduction ratio power. The Kupplung switches power to the gearbox from one engine, the other or both simultaneously. The Antriebe transfer shaft power to props. In a simplier form (without reduction gear) this schematic was used back in ww1 to power some Siemens Schuckert giant planes in a similar manner: The engines were buried into the fuselage and drove two remote wing props.
It could be argued whether 3, 5 or 8% power will be lost in the way but 5% seems to me the most reasonable guess.

The Argus AS411 engines -altough buried into the fuselage- are actually exposed to the air via airscoops. The same airscoops (altough smaller) are visible in As-411 engine nacelles. They have to cool the cylinder heads. The As-411 was not fully exposed to the air (unlike the As-410) but the engeneerer develeoped a tight engine cowling with three airscoops (called "Luftleitbleche"), which are visible on As-411 engine installations. I do not see a reason why this shouldn´t work with airscoops portruding from the fuselage.

Maintenance may be quite good. The gearbox assembly is readily accessable in the configuration shown below. The engines may be lowered through the armoured service doors for changeover or special maintenance. Cannon / ammo installation is placed in another section, shown below, too.

This section shows that the space defined by the engine installation may be used here to a great effect for either a bomb bay (2 x SC-500 or 3x SC-250 internally) or a gun section (in this case with 3x 30mm high velocity guns and their relative ammo boxes). A very big gun could be installed here, too:
Either 2x 37mm or 1x 50mm, slightly off center. A 75mm autocannon can be installed with a droppable podlike system. Since this section is closest to the cog, different weights are less important. The upper part is reserved for protected fuel tanks.

I still have not decided on the landing gear configuration. Two reasonable options are under investigation. The main landing gear will be retractable into the wings under protection of the two enforced main spars. Since we have neither engines nor fuel tanks in the wing (but a powered shaft), we have a lot of space left over to deal with.

Thanks for the explanation DelCyros!

Looking good so far...am reading...

The pics are very professional. To bad I can't do anything similar...

...at least for my next 'design', the Ju-87 with two radials mounted 'above' the wing , with retractable (or not!) undercarriage, fixed 30mm and/or 37mm cannon(s), decent armor and rear armament, dive brakes (of course)...

Part IV: The wing

Airfoil:
I choosed the 22% thick Eppler E 858 airfoil. Altough having a very low crit Mach (M= 0,58 ), this airfoil does allow very high angles of attack without stalling and thus, it gives naturally high maximum lift coefficients, esspecially at the very high Reynolds numbers typical for this wing (8 to 10 mio.). Basically, I may even gonna go with a normal high lift device system. Simple 25% long flaps should be enough to ensure the required high lift coefficients. The outer wingtips are geometrically tapered and tilted down by 1.5 deg in order to improve stalling behavior. The stall should be very gentle for a wide range of cog-conditions. Flaps are only at the center wing. automatic LE-slats are only at the outer wing, respectively.

The tradeoff comes in form of increased induced drag. Altough I would still prefer this one for
A) structurally stronger wing design
B) more space inside the wing
C) better lift creator
D) gentle stall behavior
E) lighter wing structures (simplified high lift devices)

wing area: 15.5m^2 -note: substantially less wing area than other ground attack A/C and even less than a bf-109 -call it small target size!
wingload: 306 kg/m^2 @ 4.750 kg
aspect ratio: 6.0
average wing depth: 1.6278m
wing sweep: 0 deg.
wing drag coefficiant at 1 deg aoa: 0.0215
lift coefficiant at 10 deg aoa and flaps down 40 deg: 2.79

Overall I really like you design Delcyros, I just think the engine choice could be better and I'm still worried about the landing gear.

I understand the reasoning behind an aircooled engine: Better resistance to damage. But considering the much higher amount of power available with an engine like the Jumo 213 or DB-605, I was wondering wether it wouldn't prove more beneficial to mount one of these instead and take advantage of the lighter weight and armour the engine bay to the point where it will withstand 20mm AP rounds. The benefits would be more than one as-well, as drag would be considerably descreased because of the much smaller space needed fo a single Jumo 213 or DB-605 engine, meaning you could narrow down the fuselage. You'd also reduce the weight pr. power ratio by more than 80%.

Just a thought anyhow.

I have no problem with Db-605, Jumo-213 or Jumo-211 for that matter. But they are high performance engines, not allowed in the competition. The AS 411 is non strategic, air cooled, fuel efficient, inline and readily aviable in time. Altough less efficient -powerwise- as shown by Your numbers, the As-411 allows for a very light and compact design and the flattened out fuselage cross section makes for a roomy bomb bay / weapons bay. I will nevertheless consider the Jumo-option for a later replacement of this ground attack A/C.

A point on power, Delcyros. With less than 1200 effective hp in your machine you will be duplicating the historical Hs 129 with 1400 total hp on the two Bramos and the 1400 hp JU 87 D.

Which means that when it comes to armour and weapons you will be limited to the 30/37 mm option max effective weaponry. Sure, you could overload the aircraft and put in a Mk 214 50mm or even the 75 mm but then you would have the same control and performance problems as the historical HS 129 - well at least as far as I know.

How do you plan to arm your aircraft? And armour it?

It was for precisely these reasons that I went for a total of 1,900 - 2.000 total hp in my design.

BB,

Remember that while Delcyros's design features the same engine power as the Hs-129 it will however utilize this power a lot more efficiently because of the propeller design. Delcyros's propeller design, with the engine mounted in the fuselage, means more thrust less drag all at the same time. So performance wise it should be a pretty improvement on the Hs-129.

The armour scheme and weapon options will be discussed below seperately.
In comparison with the historical Hs-129 the plane has the same power / weight figure (speak: acceleration) but a much higher powerload (aviable power / wing area). True, wingload is higher too but this is by a large margin compensated for by the higher lift coefficients produced by the wing in the first place. Controll responsiveness in the limits defined by the mission profile should be expected to be better than for the Hs-129 (all around except high speed, particularely superior in roll rates and flight conditions approaching the stall).
I am convinced that twin 37mm, centerline mounted guns would be perfect for tank hunting purposes. Even the 30mm MK 101 / 103 with APCR is adeaquate for all but the heaviest main battle tanks. The BK 7,5cm autocannon is a monstergun, which cuts down performance drastically, agreed.
I am not wanting to design a supergroundattack plane, I just want to demonstrate what could have been possible within the design limits of the historical competition in a plausible timeframe.
After reconsideration upon the wing, I decide against automatic leading edge slats and prefer fixed slots for the outer wings (compare identic Me-163 outer wing slots). They do add drag but have all other advantages of slats and are simpler in design and construction (no movable parts). A tradeoff between technical sophistication and service reliability.

Delcyros said:

I am not wanting to design a supergroundattack plane, I just want to demonstrate what could have been possible within the design limits of the historical competition in a plausible timeframe

Click to expand...

Ah ok! Didn't know that. Now I better understand your engine choice. But remember that your engine propeller design will prove quite a strain on German industry as it will be a very complicated build. The slots are a good choice, simple efficient.

Part V -weights.

Now, after defining layout and general configuration we come back to the weights of the airframe.
We have already accounted 1.994kg for:

750kg: normal internal ordenance (droppable or fixed fwd. firing guns, interchangable)
80kg: one crew
216kg : fuel
18kg : oil
180kg: gearbox and related equipment
750kg: engines

-airframe:
material: all metal

wings:
limit g-factor: 5.33 (service limit. failure limit would be 8.0)
limit airspeed at sea level: 400 kts / 460mph / 740 kmh
This requires either a main spar or a single torsion box, preferably a counterstressed design.
Spar box weight: 74 lbs
wing surface weight: 1400lbs
Total weight: 1474lbs / 669 kg.

tail:
relation to wing size: 0,4
weight: 552 lbs / 250kg


fuselage:
length: 9,8m
wetted surface: 381 ft^2
weight: 857 lbs / 389kg

armour:
wing leading edge: The fwd. main spar is protected by an armoured airfoil shaped profile (nose of airfoil, only). It is 4m long each and armoured with 4mm sheets of steel, weighting in 187kg total.

Tail: The tail section is lightly build from dural and steel. No armour at all.

center fuselage:
The armour is a closed section, 4,5m long, covering engines, gearbox fuel tank sections and in part is used as structural component with different thicknesses:
aft bulkhead: 6mm (64kg)
top: 3mm (30kg)
top sides: 4mm (210kg)
sides: 3mm (75kg)
bottom sides: 8mm (290kg)
bottom: 6mm (174kg)
center fuselage weight: 843kg

Cockpit section:
Fully closed cockpit armour.
nose bulkhead: 20mm (52kg)
seating bulkhead, including headrest: 8mm (65kg)
bottom plates: 10mm (104kg)
side plating: 8mm (82kg)
frontal armoured window (75mm): 42kg
side armoured windows (30mm): 48kg
upper armoured window (30mm): 22kg
cockpit armour weight: 415kg

total armour weight: 1445kg.
Note: about 570kg of this weight does count as structural weight because it does replace structural load taking frames, bulkheads or surface weights of the fuselage.

Delcyros,

Isn't 216 kg or roughly 270 Liters of fuel (Gas has 0.70 factor compared to water IIRC) abit on the low side? I've expect atleast 550 to 650 Liter capacity, so that's a 500 to 570 kg of weight for fuel.

Range and endurance are factors of secondary importance. Close range air support was the typical purpose of the Hs-129 / Hs-123.
The As-411 was one of the most fuel efficient aeroengines of it´s time.

216 kg fuel are normal internal fuel for one hour endurance at max. continous power:
power: 540 ps
specific fuel consumption: 0,2 kg/ps/h
required fuel for one hour endurance: 216kg.

More economical cruise speed would yield in 1.8 hour endurance. The endurance is so far not very different from those figures of Bf-109 fighters (without drop tanks). The 500 ltr. fuel load of the Hs-129 were to big for te mission profile of this plane. But with a fuel consumption of 0.242 kg/ ps / h, the Gnome Rhone 14m required more fuel indeed (305 kg for one hour endurance at max. continous power =630ps) and in top of this, the airframe was aerodynamically less efficient.
I therefore see only little differences in range but drastic differences in fuel efficiency (less quantity and quality fuels are required to operate the plane). The enduranc eof the Hs-129 is higher but who enjois staying in the cramped Hs-129 cockpit for longer than -say- three hours?
That beeing said, I think You certainly have pointed me to extend the bunkerage to allow for fuel used up normally for warming up the engines, taxiing, acceleration take off. New fuel buncerage will be 250kg

Good points Delcyros, you're absolutely right about the better fuel efficiency and much reduced drag of your design vs the Hs-129, again improving the fuel vs range covered ratio if I may call it that So maybe you're right that once in the air no more than ~250 Liters of fuel will be needed. I would however make provisions for the ability to carry up to 400 Liters of fuel internally, this might prove useful if the tide of war was to change. (One has to think positive some times )

Anyway keep up the good work

Delcryos, I've been thinking about the problem of the landing gear on this bird. Given the mid-wing configuration I think the best solution might be to have the main gear retracting into pods on the fuselage sides, with the main wheels protruding, and with a fixed tail wheel. Having the main wheels protruding will protect the fuselage from damage in the event of a crash-landing, and the fixed tail wheel will protect the aft fuselage also (although a partially retractable tail wheel might also do the trick, depending on where it's located). I've seen many pictures of crash-landed IL-2's that were saved from further damage by having the main wheels protruding (the same reasoning went into the A-10). Below is your drawing with my additions. Tell me what you think. I'm also curious about the cockpit – is it going to be faired into the fuselage, like the Hs-129, or raised, like the single-seat IL-2? Both have their advantages and disadvantages. The advantage to the Hs-129 arrangement is more protection; the disadvantage is less visibility. It's just the opposite with the IL-2 arrangement, although with the armor plating around the canopy and the armored glass, it may not have been that much less protected than the Hs-129. If you do adopt the Hs-129 arrangement, one way around the rear visibility problem would be to have a periscope, or more simply, just a good rear-view mirror, like on the Spitfire, etc. I also think it might be a good idea to keep the twin tails as on the Arado Ar-240, for the redundancy they offer in the event of damage. At any rate, just some ideas I had rattling around my head.

Venganza

Keep it up, Delcyros, I am waiting for the armament package.

Before I post drawings of my previous efforts, I have two ideas I am going to throw into this thread. They share the same theme - the 'minimal change theme'.

The idea is for something that is such a fairly minimal change to the existing design that it can be rapidly produced, and yet creates a definite advantage.

My first idea with be a new Ju 87 optimized for tank killing. This requires a new front fuselage, but will recycle the engine, the tail and all the fuselage from the second cockpit backwardsl, and the wing of the original 87, as well as the original control system

My next idea is a new 109, ditto.

Will post after Delcyros finishes.

By the way, Vengenza, that track looks too narrow to be useful in the muddy forward airfield conditions of the eastern front 1941-44.