Could you have designed a better Warbird?

Burmese Bandit said:

Regarding the thick wing of the Hurricane - that would be a problem ONLY as speeds went over the 350 mark and crept up towards 400. At the much lower speeds at which the Battle of Britain was fought, the thick wing was of fairly negligible importance.

Remember, I am talking about the Battle of Britain scenario, where there most pressing need was not for small numbers of high speed aircraft, but large numbers of passable aircraft built as quickly as possible and being repaired rapidly...and capable of being flown by the thousands of new pilots being hurriedly commissioned.

And let's not forget that many of the German aircraft, both bombers and fighters, attacked by Spits in 1940 lived to limp home to Occupied France to fight another day...because of the inadequate armament of eight rifle calibre machine guns. While the best solution was the 20 mm cannon, there just weren't enough of them in 1940 and they had reliability and ammunition supply problems as well.

So the 12 browning solution was the best available at the time. And the Spit couldn't carry 12 brownings.

The radial Hurricane would have been the perfect solution in 1940, and as the war went on and it was slowly replaced by (say) Tempests, it could have had a great secondary career as an advanced trainer and a ground attack aircraft!

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As far as the Battle of Britain, I think you're right about the Hurricane. As it was, the Hurricane shot down more aircraft than the Spitfire anyway, and with your modifications it would have done even better. I guess I was looking more long-term. I definitely agree about it making for a good advanced trainer.

Venganza

tomo pauk said:

Now the Hurricane is un-maneuvreable!? Yeah, right

The Hurricane could've used 2 British radials too, Taurus Hercules. Turning the plane to a better ground attack and/or CV machine. The speed gain would've been negligible though.

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Wasn't the Hurricane tested with a Taurus? Anyone know anything about that? As far as the maneuverability, I didn't say is was unmanueverable, I said it wasn't as manueverable as the Spitfire, the Bf-109, and the Fw-190, and I stand by that statement.

Venganza

Burmese Bandit said:

And one final statistic...


Which Non-Russian aircraft type killed the most Axis aircraft 1939-45? Three guesses.

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I assume you mean the Hurricane. More than the P-39 or even the P-40? All I can say is that the PVO units must have shot down a lot of bombers and reconnaissance aircraft. Admittedly the Hurricane was a good bomber destroyer, especially if armed with 4 20mm's or the Soviet modification of 2 .50's and 2 20mm's. Still I would like to see your data regarding this. I'm not disputing it, I would just like to see the figures, as I don't have a comprehensive list of kills by Lend-Lease aircraft.

Venganza

I think the Mustang has the highest number of kills.

The Hurricane was pretty manoeuvrable, the combination of thick wing and limited engine power for the time period reduced its sustained manoeuvrability however. It could get in a turning fight with a Messerschmitt, but not for long as the bleed of airspeed was too great and the Messer could keep his energy up with good pilot management.

The main good thing about the Hurricane was construction techniques (used existing industrial infrastructure from the interwar period so larger numbers were available more readily than the Spit early on), and also excellent stability for the sacrifice of only a little outright high speed performance. Spits and Messers were real thoroughbreds, but this also meant they could be a little tricky to get the most out of. An average pilot could fly a Hurricane well from what I understand.

Also the Merlin 20-series could handle up to +18lbs on WEP with good fuel for a short period (about a minute) so later Hurricanes had a fair bit of grunt even among contemporaries.
That being said I think the P-40E/K was better again, I've got some documentation for +18 and even +20lbs being used in the field at WEP on the Allison (up to 1780hp at the deck). Sure this was impossible at any altitude without ram effect or engine overspeeding, but down low the Warhawk could be one mean little nasty if you were happy to chance blowing the engine.

Now that I re-read his original post, I think Burmese Bandit was not just referring to Soviet Lend-Lease aircraft when he implied the Hurricane shot down more aircraft during the war than any non-Soviet type, as I had assumed. Am I correct about this, Burmese Bandit? That's interesting, Vanir, about the P-40E/K. That may explain why the Soviets had reasonable success with it as a fighter as they often ran it with the engines going flatout. It also explains why at first they only got about 30%-40% of the advertised MTBF for their Allisons. The problem of burned-out Allisons got so bad at one point that they re-engined about 40 P-40E's with Klimov M-105's (I'm actually doing a model of one right now).

Venganza

I would have an idea for a dedicated ground attack plane. Interested?

delcyros said:

I would have an idea for a dedicated ground attack plane. Interested?

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Go for it, delcryos!

Venganza

Vengenza: Yes, you're right. I meant the Hurricane. Shot down more enemy aircraft than the Spit, Mustang, the P 40, the Jug, or the Lightning.

Delcyros: GO FOR IT!!! I Shall be Cheering you on!!!!

Always good to hear from Del. BB, are you sure that Hurricane shot down more enemy AC in the whole war than Spitfire or P51? I find that hard to believe.

I have read 4 books on Aircraft of WW II and everyone of them said that the Hurricane did so.

Some preliminary thoughts:

At first I want to stress that I use german design / engine and equipments not because I like them more than -say- french material but simply because I am more familar with the technology. Basically I very much like dutch and french along with US and british designs. I have my utmost respect for soviet aeroengineering as well but I suffer from a somehow limited knowledge with regard to these.

Ok, the timeframe in question is the well known ground attack A/C competition hold in Germany out of which the Hs-129 finally evolved in 1940/41. Some of the requirements were quite interesting for a dedicated ground attack A/C:

A) only low priority engines (2nd class) with low grade fuels are to be used, 1 crew only.
B) The aircraft´s performance should put emphasize on close range low altitude mission profiles
C) It should have a measure of redundancy and very tough structural strength. Additionally, crew, ammo boxes, fuel and engines should be armoured to resist light AAA and machine gunfire.
D) The target size should be as small as possible
E) interchangable loads are essentially important. Particularely because the A/C has to deal with enemy tanks so it should be able to take a big gun.
F) speed and altitude performances are irrelevant. The A/C should have a good low speed handling.

I will base my entry on an artificial ARADO / HENSCHEL joint ground attack fighter.

let me just prepare some graphs...

Go for it Delcyros! Earlier in this thread I made a proposal for a five Argus-Engined Aircraft. with four engines in a push-pull a la Dornier and one engine behind the gunner for driving the common supercharger and rear protection.

The Airplane also had a 'Tanden Triplane' configuration and an offset nosewheel so that the belly pack gun could fire on the centerline.

What's your solution??? I am very interested!

Delcryos, it'll be interesting to see how you handle the problem of low-power engines. I've always thought the fatal flaw in that aircraft specification was the insistence on the use of non-strategic (read - low-power) engines. Because of that, the Hs-129 was always underpowered, especially when carrying that huge 75mm cannon. By the way, Burmese Bandit, did you ever complete any drawings of your plane (remember I did a feeble attempt to present my interpretation)?

Venganza

No.

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

Still, it's coming along!

Part I

General layout:


My basic design root to move away from is the Arado Ar-240. I very much like the high lift devices installed into the small wing. But indeed, the Ar-240 is way to large and heavy for the low powered engines in question, so I will have to make it smaller and ultimately much lighter, too.
Sincehigh speed is not a primary concern, I will adopt a very thick airfoil (22% root thickness and 20% wingtip thickness) with poor high speed handling and low crit Mach factors (who cares about a crit Mach of M=0.65 when the profile asks for low altitude missions? I could live with M=0.5, too) but great lift properties and very good structural strength. I do not want to improve lift by adding wing area, I want to improve lift by increasing the lift coefficients of the wing with thick airfoils and sophisticated high lift devices (compare attached picture below for a detail of the slotted fowler flaps from the Ar-240 wing section)!
This will in turn greatly add wingload but that´s not negatively for the profile of the A/C: A high wingload implies an aerodynamically mor eefficient design and more importantly, a highly loaded plane does not bounce around that heavily in low altitude (thermics). I will take this to be one factor to the steady gun platform necessary for a dedicated ground attack A/C.

The Arado company worked on quite some novel but untested features back in 1937/38. The Ar E.561 project f.e. had both engines mounted into the fuselage moving a shaft via gearbox drive to propel both leading wing edge propellers.

The engines were to be mounted in the wing root junction with the fuselage, and the four-bladed, variable-pitch propellers were driven by a shaft. The reason behind this design was that if one engine failed, then the other engine could drive both propellers at half speed. Another advantage was that the aircraft could have a sleeker design with the engines buried in the fusleage-wing junction.

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Arado Ar E.561 Luft '46 entry

I personnally may add other advantages of this configuration:

A) the target area is reduced caused by the loss of engine nacelles
B) The engine and drive section close to the center of the fuselage is nice for cg issues
C) Moving the weight of the engines to the fuselage allows for better (faster) roll charackteristics
D) The compact placement of the engines into the center of the fuselage allows for effective engine protection by armour plates
E) the propeller in a clean pull-configuration mounted on the leading edge of the wing does add prop washout effects to the wing, greatly improving the lift coefficients of the wing section affected by propstream

This is a comparison of the frontal appearence of an early version of my design based on the same engines with normal nacelles and center engines with driveshaft (scales in metres):

Such a layout was indeed investigated by the Arado-company on the base of the Ar-240.

Arado Ar E.654 Luft '46 entry

Actually with twin Db-627 engines for a multi purpose fighter bomber. But we need something different, which brings us to the question of the dimensions and weights but before we do so, I will prepare something to the powerplant used for my ground attack A/C.
Compared with the Ar-240 the dedicated ground attack A/C in the suggested configuration will have less wetted and frontal area but more induced drag (thick airfoils!). We will discuss performances later.

So far, excelllent DelCyros.

Some quick questions.

Is the Technology you describe plausible to effect in 1942-42? Or evcen earlier, such as the 1937-38 time frame you mentioned? Or is it only plausible in 1943 with mass production in 1944, at which point the war was almost certainly lost? Regarding the shaft extensions to remote propellers, I believe that only one company has done that in nearly 90 years of plane design - Bell with their V-22 Osprey. And I believe that Lockheed was thinking of doing that when Kelly Johnson was tinkering with the preliminary design of the P-38 but abandoned it as being too difficult at the time. Am I correct? Please correct me if I am wrong.

What about combining high-lift devices, such as the leading edge slats (I believe they are called Handley Page slots after the name of the first company to use them) with spoilers on the opposite wing acting differentially, as was done with the P-61 Black Widow?

I suspect your cockpit will be in front of those two engines. That would definitely provide for a measure of rear attack safety. Good.

I also suspect that you will need an armoured firewall between the two engines, so that one cannon shell could not destroy two engines at once.

Keep posting! I am very interested!

The technology as I see it very much existed. I really like the fact that the engines are kept in the fuselage while the props are located at the wing leading edge, most likely on an elongated propeller hub to keep the prop blades roughly 65 cm away from the leading edge. That would make sure that full span slats could be added and go right up behind the prop.

The fact that the wing is kept virtually completely clean except for the small spot with the propeller hub, means that more lift AND thrust is added. The idea is infact so good that it could be used for twin engined fighter design.

The long connection between the engines and the propellers is the most complicated thing to work, but the Germans already had that figured out in their Fa-223 Drache, so this wouldn't have posed a problem.

I see only one problem at this point, and that is the landing gear, it will have to be very long as the propeller arc stretches a long way below the fuselage.

Junkers (G-planes) and Dornier had plenty of experience with shaft extensions, particularely well demonstrated in the Do-18 floatplane with a long shaft extension to drive the pusher prop.
What was unknown is the question whether or not right angle drive shafts could work. The idea was already put into use by large naval crafts (Vulcan gear drive couplings on pocket battleships) but not on small airplanes. Hydraulic gears would be simple, mechanically reliable with high efficiancy and not difficult to master but they are to heavy for our plane. Electric drive gears do have not such a high efficiency and they are quite vulnarable. Mechanical drive gears are the solution. I suspect something like 5% loss of power and a system requiring approximately 180 kg of weight, including shafting (conservative guess based on Blume´s specifications for such a system and a safety factor of 1.50).


Part II: Engine.

We want a simple and light engine. Preferably air cooled. Actually we do have a reasonable candidate: The Argus As 411A engine, a more developed As-410 version, driving Si-204 transports, Fw-189 recon and several Arado trainers:

layout: inverted 12 cylinder V-engine
cooling: unforced air cooling, ejector nozzles
fuel rating: 80 octane
compression ratio: 6.4
output: 600 ps / 594 hp / 441kw @ 3300rpm
rated altitude: 3000m with single stage supercharger ("Höhenlader").
dry weight: 375 kg with "Höhenlader"
length: 1.585m
width: 0.66m
height: 0.97m
specific fuel consumption: 200 g/ps @ 3250 rpm (540 ps and 3250 rpm)

The engine was provided with single lever controll (automatically adjusted fuel mixture) and reduction gear. The latter may be removed completely as this task will be performed already by the gearbox necessary to drive the remote propellers. The supercharger, too, may be spared, freeing 60kg of weight per engine. The following picture shows a transverse cut in order to explain the engine installation into the fuselage:

As we have two such engines and 5% gearbox losses we will have the aequivalent of 1140 ps aviable to drive the plane. This is very important as it allows us to define the max. weight of the plane.
For comparison reasons I will give power / max. weight figures for several planes (the higher that ratio, the better the acceleration):

transports:
Si-204 (with As-411): 0.222
recon:
Fw-189 (with As-410): 0.235
ground attack:
Ju-87D-5 (with Jumo-211J): 0.198
Hs-129B (with G&R 14M): 0.270
Hs-123 (with BMW-132Dc): 0.386
fighter trainer:
Ar-96 (with As-410): 0.274
multi-purpose:
Bf-110C4 (with Db-601A/B): 0.293
Fw-190A (with BMW-801D-2): 0.442
fighter:
Bf-109e (with Db-601A): 0.459

Judging from these numbers, I could live with a power / weight ratio of 0.275 for the dedicated ground attack A/C, while under very heavy loads this could drop down to 0.200 in the worst case. The max.permissable take off weight should then be in between 4.145 kg normal and 5.700 kg under overloaded conditions.
For reasons of simplicity, I will continue with a max. take off weight of 4.750kg.

The weights defined so far are:
750 kg -engines
180 kg -gearbox and shafts
80kg - pilot

we now add the desired weight for fuel. As endurance is a second order importance, I am statisfied with no less than one hour endurance at max. continuos power. This requires a total of only 216 kg of 80 oct. fuel. Quite enough for close range requirements. Careful fuel management will significantly improve range and endurance. The following part will deal with the dimensions corresponding with our weight figures.

Part III: Dimensions

The Ar-240 had quite a high wingload (330 kg/m^2) and our dedicated ground attack A/C should preferably fall in the same or nearby range. I suggest a wingload of 306.6 kg/m^2 @ 4.750 kg. This implies a wing area of only 15.5 m^2, approximately half of the Hs-129´s wing area and together with 9.64m span a corresponding aspect ratio of 6.0.

The lift coefficient with propwash and extended high lift devices should be 2.8 with an average of the whole wing (netto) beeing very close to 2.5, suggesting a take off speed of 160 km/h at MTOW(=4.750 kg). This is lower than for Fw-190 / bf-109 derivates, altough the take off run is estimated to be higher due to the weaker acceleration (compare the power / weight ratios given above).

Delcyros,

The overall max lift coefficient of the wing with all the high lift devices extended would be around 3.2, atleast that is assuming that you are using fowler flaps. Highest Clmax occuring in some areas will be in the range of 3.4.

Regarding the chosen engines, well considering they are aircooled are you sure they'd be the right choice ? Aircooled engines are normally only used on designs with externally mounted engines with direct exposure to the airflow. When the engines on your design are to be hidden away I believe maybe a single Ju-213 might be a better choice, would also mean you could narrow down the fuselage, and with a power of 2,100 PS for a weight of just 910 kg you'd have a decreased weight as-well

And there's the landing gear, I was wondering what your solution for that would be. Is it to b wing mounted or fuselage mounted. A three point landing gear like that of the Ar-234 might work?