Top Five fighters of WWII and why

[caldrail]

Weight means very little regarding dive performance since the aeroplane is accelerating faster than gravitional pull.

I doubt they go faster than gravitational pull. The below suggests to me that weight is always helping push you into a faster dive. But GRANTED the effect will be small and sometimes washed out by factors of a low drag design or powerful engine.

We're talking WW2 fighters here. They're quick aeroplanes to begin with, and believe me, aeroplanes accelerate even quicker when they're pointed downhill. A crash at Thruxton in the 90's saw a Beech Baron stall and nose in from 400 feet, hitting the ground at more than four times its original flying speed.

 

Net thrust means the vent thrust exceeds the vent drag (sort of like a net profit), which I was denying. The Spitfire article on wiki says what I was affirming by reversing the phraseology "this used the cooling air to generate thrust, greatly reducing the NET DRAG produced by the radiators". That should clarify the meaning, regardless of factual disagreements (I don't like their word "greatly").

You cannot achieve thrust by creating drag. Radiators create drag. They are designed to cool engines. They are not engines in themselves. You do not obtain thrust from radiators. All you casn achieve is to minimise drag. You cannot create thrust by forward motion alone - that breaks the laws of physics no matter what that article claims - in order to change interia, you need to add force by using additional energy, and since a radiator is designed to dissipate that energy, I don't see any evidence for your statements.

 

Incidentially your estimations of aeroplane factors aremn't that accurate. The P47 is, according to you, a draggy aeroplane. That was a criticism applied to radial engined fighters before WW2, and it was proved wrong. The teardrop shape is better aerodynamically than that despite the blunt face (which allows some air passage through it via cooling gills) and if proof were needed, I would like to point out that the P47 accelerated well and had a high top speed, so clearly drag was not that great an issue.

[Melvadius]

Not claiming any specialist knowledge but a couple of observation; isn't there also an issue here of which version of a particular air frame is under discussion?

 

The Spitfire is a primary example, but not unique, of a plane which went through innumerable different versions throughout it's operational life. Similarly, I believe that at least one of the US planes under discussion had different operational characteristics depending on which engine it had been fitted with.

 

These variations are rarely considered when people start talking up one plane against another as ususally 'kill' ratios, which seem on the face of it very important, tend to be collated by plane 'frame' rather than by individual models of each plane type.

 

Another confusing factor has been touched on already is theconsideration what combat role particular plane's and in which proportion of their different models played it; whether they spent most of their time operating at the extreme end of their range, against other fighters as the relatively fewer Spitfire's did during the Battle of Britain while the Hurricane's usual target were bombers or if they usually met inferior planes/ pilots.

[caldrail]

You are correct. Some aircraft weren't amenable to development as like the Hurricane or P40, revisions and redesigns never caught on, whereas aeroplanes like the Spitfire changed considerable\y over the course of the war and in fact the later versions were virtually new aircraft designs with different engines.

 

One of the most significant variations was of course the engine itself. The early mustangs for instance had poor altitude performance from their allison v12's, but when fitted with supercharged merlins, became one of the better fighters of the war - and arguably, one of the most significant in the european theatre of war because the long range of later versions meant bombers could reach Berlin with escort, thus forcing the Germans to hold back valuable fighter strength in defence.

 

However, with the general migration toward more powerful engines we have to accept that aircraft also needed to carry more weight, such as fuel, bombs, ammunition, as adaptions to changing war conditions and filling roles that would otherwise need expensive and long winded design work to produce new designs.

 

Although in terms of performance aircraft were obviously improving, that's not neceessarily true of important qualities like handling. Most fighters suffered in terms of 'flyability' as their weight escalated, though in fairness this was obvious to aircraft manufacturers who went to considerable length to eradicate any dangerous tendencies in flight behaviour.

[caesar novus]

You cannot achieve thrust by creating drag. Radiators create drag. They are designed to cool engines. They are not engines in themselves. You do not obtain thrust from radiators. All you casn achieve is to minimise drag. You cannot create thrust by forward motion alone - that breaks the laws of physics no matter what that article claims - in order to change interia, you need to add force by using additional energy, and since a radiator is designed to dissipate that energy, I don't see any evidence for your statements.

 

Incidentially your estimations of aeroplane factors aremn't that accurate. The P47 is, according to you, a draggy aeroplane. That was a criticism applied to radial engined fighters before WW2, and it was proved wrong. The teardrop shape is better aerodynamically than that despite the blunt face (which allows some air passage through it via cooling gills) and if proof were needed, I would like to point out that the P47 accelerated well and had a high top speed, so clearly drag was not that great an issue.

Where are peoples proposals for top 5 fighters? Boring to quibble like lawyers back and forth about my initial words - let's see constructive cases made for a p-38 or la-7 or something. I have explained my proposals clearly enough and linked to supporting references for points in controversy. If words fail to get my points across, I give up and can only offer pictures...

 

Below I will depict

1) NASA (naca in 1941) model proving radiator thrust, using electric heating element to simulate radiator

2) successful Tory-IIC nuclear powered ramjet (eg. propulsive duct, thermal jet, stovepipe jet)

3) flat nosed standard p47 (draggy fuel hog replaced ASAP by sleek merlin p-51 for long escort missions)

4) sleek 500+mph xp-47j when they got ducted fan religion (still big turbo scoop)

5) supersleek xp-72 with scoop moved out of nose (xp-47 follow on... these had longer, slimmer radials)

6) slim Corsair with big p47 type engine more tightly cowled, and scoop relocated to wing leading edges

7) stubby late war Bearcat with flat nose

8) sleek post war racing Bearcat (probably internal fan to assist slim duct area)

9) sleek ducted radial Hawker Tempest2... a (US) pilot scored 11.5 kills in one (p47 in background)

 

 

[Melvadius]

I suppose that if I had to choose my top 5 planes would fly totally in the face of the 'facts' of which were the most powerful/ adaptable/ manouverable etc of which I've never taken detailed interest.

 

I'm not sure which I would include in the last two slots but 'Faith', 'Hope' and 'Charity' would probably come out on top since 'by repute' they formed the initial aerial defense of Malta against waves of vastly superior enemy aircraft.

 

Now OK in reality there probably at least four Gloucester Gladiators involved in the defence and there were I believe also some Hurricanes but they provided a strong boost to morale both on Malta and in Britain and conversely amongst the attacking Italian pilots which vastly outweighed their fighting abilities during the ciritcal early defence of 'Fortress Malta' during WWII.

[Northern Neil]

1) NASA (naca in 1941) model proving radiator thrust, using electric heating element to simulate radiator

It seems to me that radiator thrust is a given - it matters not wether a heat source is burning fuel, or heat from an element - the heated air has to escape somehow, and with an exit smaller than intake, this effect will be enhanced.

[caldrail]

No, it isn't. How difficult is this to understand? Radiators do not create thrust. They can't. Otherwise we could approach the speed of light even easier than setting off from a standing start.

 

)(1) NASA (naca in 1941) model proving radiator thrust, using electric heating element to simulate radiator

It doesn't 'prove' anything other than the creation of a duct, and quite franklly, that looks more like a ramjet to me, which I happen to know the P51 was tested with.

 

2) successful Tory-IIC nuclear powered ramjet (eg. propulsive duct, thermal jet, stovepipe jet)

And this means what exactly? Nothing, other than they built a ramjet. Elephants and mice are both mammals but they do different things. Human recogntive skills sometimes join up dots in all kinds of daft ways.

 

3) flat nosed standard p47 (draggy fuel hog replaced ASAP by sleek merlin p-51 for long escort missions)

The P47 had less rangem, thus because escort missions were becoming longer as allied air power found it easier to penetrate weakening german defenses, it made more sense to give those missions to the 'sleek P51'. The P47 is not as draggy as you think. As I said, the teardrop shape is efficient aerodynamically and since it was faster than the corsair with less power in level flight, I would have to say that darg was not a great issue (again).

 

4) sleek 500+mph xp-47j when they got ducted fan religion (still big turbo scoop)

For a while the fastest aeroplane if I remember right. Certainly quicker than a P51.

 

5) supersleek xp-72 with scoop moved out of nose (xp-47 follow on... these had longer, slimmer radials)

A prototype un fortunately which does not necessarily depict aircraft as finalised for service. I don't know if 'supersleek' is anything more than your own impressions, and I do realise you're trying to make a point by exaggeration, but realise the P72 contract was cancelled because faster sleeker jets were becoming available.

 

6) slim Corsair with big p47 type engine more tightly cowled, and scoop relocated to wing leading edges

And still slower than a P47.

 

7) stubby late war Bearcat with flat nose

radial engined fighters have blunt noses by necessity. Nonetheless, this aeroplane wasn't exactly slow either. You have to realise that looks aren't everything. Just because you think something loooks like this or that doesn't make it so. What you're trying to impress upon us is largely your own imagination.

 

8) sleek post war racing Bearcat (probably internal fan to assist slim duct area)

And useless for military service.

 

9) sleek ducted radial Hawker Tempest2... a (US) pilot scored 11.5 kills in one (p47 in background)

Quite. Nonetheless the sample of your statistics is small and thus biased. Much depends on the relative skills and experience of pilots, operational circumstance, the effectiveness of the enemy adversaries, and the numbers involved. There are other examples throughout WW2 of individual pilots scoring highly in single missions.

Edited August 28, 2011 by caldrail

[Northern Neil]

No, it isn't. How difficult is this to understand? Radiators do not create thrust. They can't.

Its actually relatively simple. The radiator heats up and expands the air inside the engine, which escapes through the narrower rear. The heated element (if one prefers that to radiator) serves the same function as the fuel burner. The radiator/element does not in itself cause thrust, the escaping heated air does. It is really irrelevent what the nature of the heat source is, as long as air is heated and has a means of escape.

[caldrail]

No, it isn't. How difficult is this to understand? Radiators do not create thrust. They can't.

Its actually relatively simple. The radiator heats up and expands the air inside the engine, which escapes through the narrower rear. The heated element (if one prefers that to radiator) serves the same function as the fuel burner. The radiator/element does not in itself cause thrust, the escaping heated air does. It is really irrelevent what the nature of the heat source is, as long as air is heated and has a means of escape.

 

Erm... No. Sorry. If you could use a radiator in such a way it won't cool the engine (the entire point of installing it) because as you seem to have forgotten it requires a force applied to the airframe to push the vehicle forwards. Since the air inside the radiator is not sufficently heated to create this force (in order to carry warmed air away, not retain it) it cannot push the aeroplane. There is not enough energy transfer per molecule to achieve any measurable level of thrust. That's thermodynamics, which in simple terms says you don't get something for nothing.

 

I find it both remarkable that theories like 'radiator thrust' only emerged in the last couple of decadss along with the rise of the internet and the self-appointed expert. I've read literature on aviation technology dating back to 1918. Even one written in 1938 does not mention anything about radiators providing thrust, and although R J Mitchell clearly had in miond to make his famous fighter as aerodynamically clean as possible, his idea was to use a dirty great V12 combustion engine and propellor to create thrust, while the rest of the aeroplane was designed for minimal drag in order to let ironwork do it's job to great effect. Neither for that matter is there any claim during WW2 to have designed radiators for extra thrust, either from allied or axis manufacturers, despite a strong tendency for those manufacturers to make exaggerated claims for their products. neither for that matter do the people operating race converted WW2 fighters ever mention radiators in the context of anything other than cooling and drag.

[caesar novus]

I find it both remarkable that theories like 'radiator thrust' only emerged in the last couple of decadss along with the rise of the internet and the self-appointed expert.

Edgar Schmued (chief design engineer on the P-51) and Edward Horkey calculated that an aerodynamic duct formed at the entry and exit of the radiator could provide up to 300 lbs of thrust by utilizing ram air to eject the warmed airflow and thus overcome the drag offered to the fuselage by the duct itself.

the British did not use this innovation and left it to his company to exploit in the design of the P51's radiator duct (the so called 'Meredith Effect'). He told an amusing anecdote <...> regarding this. Apparently, he met Willi Messerschmitt after the war who told him that the Germans couldn't figure out why the Mustang was so fast (in relation to its installed power) - they had stripped it down to the last nut and bolt but hadn't thought the shape of the radiator duct significant.

So if it wasn't the laminar flow wing that gave it it's high speed and

extensive range, what was it?

 

The most prominent speed secret was the dramatic reduction of cooling

drag. Placing the airscoop on the belly just in front of the rear edge

of the wing removed it as far as was practicable from the turbulence of

the prop and placed it in a high pressure zone which augmented air

inflow. Tests in the wind tunnel with the initial flush mounted scoop

were disappointing. There was so much turbulence that cooling was

inadequate and some doubted that the belly scoop would work. The

breakthrough was to space the scoop away from the surface of the belly

out of the turbulent boundary layer of the fuselage. Further testing

showed that spacing it further out would increase cooling but at a cost

to overall drag. Various wind tunnel tests established the spacing at

the current distance which represents the best compromise between

spacing out from the turbulent flow of the fuselage, drag and airflow.

 

With the flow into the scoop now smooth and relatively nonturbulent,

the duct leading to the radiator/oil cooler/intercooler was carefully

shaped to slow the air down (the duct shape moves from narrow to wide,

in other words a plenum chamber) enough from the high external speeds

to speeds through the heat exchangers that allowed the flow to extract

maximum heat from the coolant. As the air passed through the radiators

and became heated, it expanded. The duct shape aft of the radiator

forced this heated and expanded air into a narrow passage which gave it

considerable thrust as it exited the exhaust port. The exhaust port

incorporated a movable hinged door that opened automatically depending

on engine temperature to augment the airflow. The thrust realised from

this "jet" of heated air was first postulated by a British

aerodynamicist in 1935. The realization of thrust from suitably

shaped air coolant passages is named after him and called the "Meredith

Effect".

"The thermodynamic effect of the engine cooling was well-known in the 1920s and 1930s and in fact had been first pointed out by Hugo Junkers in 1915 when he acquired a patent for the "D

[caldrail]

Nice try CN. Actually I'm pleased you made you made the effort, but the problem with trying to prove a point is that people get very choosy about which evidence they put forward. As it happens that cartoon is fairly accurate of the cavernous radiator duct of a P51 - I had a good look at one at Hendon museum once.

 

Here's the problem. The primary funcrion of a radiator is to get rid of heat. That's why they designed it. At medium power cruise let's say our P51 is flying at 250kts. That big V12 generates a lot of friction and combustion heat. Most of the combustion heat is thrown straight out the exhaust stack, which is deliberately angled back and benefits to a small degree from the reaction thrust, the reason being that the combustion cycle produces a lot of pressure. That's what pushes the piston, turns the crankshaft, turns the propellor, and forces the air back to provide the impetus to reach our hypothetical cruising speed.

 

Circulating in the engine is coolant. It has a very high boiling point, but the heat it picks up can boil it suprisingly quickly, so the liquid is merely a medium to carry that heat elsewhere. We still need to get rid of it. Luckily our P51 designer has thought of adding a radiator. The liquid is exposed to air rushing past it at 250kts, or possibly more due to propellor backdradft, or possibly a little less due to shockwaves developing around a constricted entry duct, a problem that won't be serious unless we reach much faster speeds.

 

As with 'wind chill' the heat is stripped away by the movement of air and exits the aeroplane quite quickly without building up any great temoperature itself. The problem with radiators is that they don't work very well when the aeroplane is stationary and there were instances of fighters engines siezing up because they ran their engines on the ground for too long. In other words, the faster we, the cooler the radiator gets because the 'wind chill' effect works more effectively.

 

The cartoon exaggerates the difference in temperature and notice how there's no indication that the air is moving through the aeroplane. Since a 'ram-air' effect operates on the grounds that air entering forms a barrier against the expanding air behind it, that would mean the radiator becomes less effective at speed because you've reduced the airflow through it. Disaster.

 

The Napier Heston air racer of 1938 used a similar duct for their engines cooling. The designers did not mention anything to do with 'ram-air thrust' because there wasn't any. What is commonly quoted as exhaust thrust is in fact a 300lb equivalent reduction in drag by producing an effective boundary layer control under the rear fuselage that reduces vortices, the major cause of drag at that part of the airframe.

 

You see, if all this stuff is correct, then the aeroplane could move on the ground purely by this expansion in the radiator efflux. I don't know the weight of the P51 offhand but let's assume it's around 3 tons. Three hundred punds of static thrust should move the aeroplane slowly with brakes off, although our situation is clouded by the static impetus of a rotating propellor even at idle. I would think, even if the propellor was removed, that the aeroplane would not move forward, because the expansion of air in the radiator efflux is nothing like that of cylinfer combustion - since no energy is being put into the system at that point - the whole point is to transfer the energy you already have and get rid of it.

 

This is the most essential point to understand. Our airflow at the radiator efflux has to pass through or the radiator loses efficiency. If constricted (and it isn't - the exit from the radiator duct is very large on a P51, much larger than the inlet) then the rate of air exiting is reduced because as we know from blowing down a tube, the effort required to increase airflow becomes much harder. That means the air entering is forced aside by a pressure wave. Thus we get less air entering, less air exiting, less cooling, and no thrust.

 

 

In the specific case of the radiator duct of a P51, the air passing through, even allowing for expansion which is actually minmal since the warm air exists the aeroplane very quickly, enters a larger efflux space and therefore has no additional pressure to apply upon the airframe. However - the pilot can control the radiator exit door and in order to achieve less drag, he can actually almost close it completely. At this point, the air does have a restricted exit. Notice though that this prevents efficient cooling. In other words, the only way a pilot might generate anythibng approaching 'thrust' is to riskk siezibng his engine. Since the survivability of combat partially depends on ensuring the reliable operation of highly stressed aero-engines and airframe parts. In the case of the P51, the engine responds autom,atically I notice, therefore in order to maintain operationalm temperatures the airflow is less restricted.

 

The Meredith Effect, postulated in 1935, relies on this idea that rammed air is creating reactive thrust against expanding air in a radiator. However, as we have seen, the expansion of air is too slow. Each molecule is passing quickly thus does not build up high individual levels of heat, certainly not enough ebnergy top press effectively against a 250kt wind. In other words, as much as the force of airflow entering the radiator provides a certain force, the expansion of air is not rapid nor intense enough to generate thrust. The only way to do that is retain heat in the system so the efflux air is heated to a much larger degree, thus reducing considerably the cooling effect of the radiator system.

 

What we have therefore is a conflict of effect. The point of a radiator is to lose waste energy. The Meredith Effect relies on the concept that waste energy is present and retained to a level that can be exploited. Without it, there is nothing to push against the 'rammed air'. But, as we have seen, the retained energy reduces cooling, reduces the effectiveness of a warplane, and in all likeliehood, reduces the number of pilots availble the next day.

[caesar novus]

Where are peoples proposals for top 5 fighters? Boring to quibble like lawyers back and forth about my initial words - let's see constructive cases made for a p-38 or la-7 or something.

For more suggestions of candidates see "The Oxford Companion to World War II" which is just fabulous in terms of its graphic charts, maps, and concise articles: http://www.oxfordreference.com/pages/Subjects_and_titles__t139 . It has a fighter section with all kinds of comparative statistics and writeups on the relative success of various tech features or tactics such has been brought up here. Not just nerdy stuff, but eye catching charts using a drawing of each aircraft placed relative to each other, etc.

 

I didn't have time to absorb even half of it, and it didn't seem to exactly declare the "bests", but it did break down each year of the war with about 5 the most notable fighters in rank of certain performance criteria. Also broke down by country, etc. For the early part of the war it added a French Dewoitine fighter as a contender, and near the end of the war the Shiden/George from Japan. Otherwise most of the top candidates were much as were posted here, except more love for the Tempest 5 rather than 2, and griffon Spitfire 14 (if I remember correctly).

[Northern Neil]

 

Where are peoples proposals for top 5 fighters? Boring to quibble like lawyers back and forth about my initial words - let's see constructive cases made for a p-38 or la-7 or something.

 

Ok, Here goes. Based on a combination of factors - reputation, engineering/performance, and romance:

 

5) Vaught Corsair

4) P51 d

3) FW 190

2) P47

1):To Quote Jeremy Clarkson, from the UK TV motor - show Top Gear:

The fact is simple. The Spitfire looked good. It was every bit as dashing as the young men who flew it, and in flight it was as graceful as any bird. Its progress through the sky seemed effortless, as though it was simply riding the breeze and its Merlin engine was only there to provide a suitable soundtrack. Possibly, just possibly, the Spitfire is the greatest machine ever made.

[caldrail]

No, you're all completely wrong. The best ever british fighter of WW2 was the Martin Baker MB5, which sadly did not arrive quickly enough to see service and was obstructed politicially from doing so because the Ministry of Supply wanted Martin Baker to contract for other companies production.

 

http://en.wikipedia.org/wiki/Martin-Baker_MB_5

 

One test pilot recommended that the cockpit layout should be made stabndard for single engined fighters - albeit a little late in the day. In the words of Aeroplane Monthly "It remains a minor mystery why this fighter was never put into production".

 

After the relative disappointment of the MB3 project the '5' was a much better aeroplane, which attracted no major criticism from test pilots at all.

 

Please inform Mr Clarkson that he ought to learn a bit of aviation history first. Sorry. Couldn't resist that.

[caesar novus]

No, you're all completely wrong. The best ever british fighter of WW2 was the Martin Baker MB5, which sadly did not arrive quickly enough to see service and was obstructed politicially from doing so because the Ministry of Supply wanted Martin Baker to contract for other companies production.

 

http://en.wikipedia.org/wiki/Martin-Baker_MB_5

That plane looks absolutely awesome, and it's a shame it needlessly lost it's chance for war production. Maybe it was like the elegant F23 losing in favor of the clunky F22. I believe the F23 won the performance competition, but then the gov't said we don't trust the F23 builder to stay in business or something. Well, why hold the contest then (actually maybe if the F23 was cheaper or even better).

 

I love the counter rotating props, which cancel out prop torque among other things. This could be bad with high power to weight ratio; I recall a German ace telling how they would lose new pilots due to needing almost full rudder for p.torque during takeoff, when you may need even more for crosswind. The P-38 was one of the few planes to use (separated) counter rotating props, which even turned the correct ways to compensate for asymmetric drag if the other engine conked out.

 

Mb5 seems a lot like the Fiat G55/56 which I praised in another topic describing my pilgrimage to the sole Italian museum holding one. They both borrowed heavily from the successful Mustang in wing, mid-body, and rear body design. They put special attention into harmony of controls. Under a Spitfire-like nose, they gave it a capacity for the latest generation of engine which had about gained too much weight/bulk for current fighters (griffon Spitfire, late bf-109).

Edited October 5, 2011 by caesar novus