Is Spitfire really the BEST British fighter???

[Soren]

On paper maybe

No, by the laws of physics !

(and this is quite debatable), but in fact the Spitfires, after the 109E, were always rated as having better rates of turn. Time and time again, both British and the bulk of German sources credit the Sptifire as having been the superior turning plane.

Well first of all you wont find any account about that with an 109F, cause none were tested by the allies IIRC. Galland said the F series turned tighter than the E series, and for many reasons, it had lower liff-loading, better power-loading etc etc..

Galland about the Bf-109F:
"It climbed and turned like hell"

And how did the G-10 and K-4 eliminate elevator and aileron problems? I've never seen anything to indicate this.

Ever heard about "flettner tabs" ? The only slight problem was diving to a speed above 750-800 km/h, at that speed it would take two hands to pull up, but still it could with relative ease pull out of the dive.

The G series could pull out of a 750-800 km/h dive easier than a P-51 Mustang ! This is also confirmed by many Allied P-51 fighter pilots.

For one Thomas L. Hayes, Jr. recalled diving after a fleeing Me-109G until both aircraft neared the sound barrier and their controls locked:
Both pilots took measures to slow down, but to Hayes' astonishment, the Me-109 was the first to pull out of its dive. As he belatedly regained control of his Mustang, Hayes was grateful that the German pilot chose to quit while he was ahead and fly home instead of taking advantage of Hayes' momentary helplessness. Hayes also stated that while he saw several Fw-190s stall and even crash during dogfights, he never saw an Me-109 go out of control."

And a little quote:

Robert C.Curtis, American P-51 pilot.

My flight chased 12 109s south of Vienna. They climbed and we followed, unable to close on them. At 38,000 feet I fired a long burst at one of them from at least a 1000 yards, and saw some strikes. It rolled over and dived and I followed but soon reached compressibility with severe buffeting of the tail and loss of elevator control. I slowed my plane and regained control, but the 109 got away.
On two other occasions ME 109s got away from me because the P 51D could not stay with them in a high-speed dive. At 525-550 mph the plane would start to porpoise uncontrollably and had to be slowed to regain control. The P 51 was redlined at 505 mph, meaning that this speed should not be exceeded. But when chasing 109s or 190s in a dive from 25-26,000 feet it often was exceeded, if you wanted to keep up with those enemy planes. The P 51B, and C, could stay with those planes in a dive. The P 51D had a thicker wing and a bubble canopy which changed the airflow and brought on compressibility at lower speeds."

The 109K was a bad rolling plane at even moderately high speed.

That is untrue ! It had better roll rate than any other 109 infact, and its wingspan was reduced from 10.6m to 9.94m. Each newer 109 version handled better in high speeds, the best being the 109 K series.

[Soren]

Looks like the Bf-109F was tested, but only shortly, and not against other aircraft.

AFDU 28 October 1941: TACTICAL TRIALS - Me.109F AIRCRAFT- 7:
No manoeuvrability trials were carried out against other aircraft but the Me.109F was dived up to 420 mph, IAS, with controls trimmed for level flight and it was found that although the elevators had become heavy and the ailerons had stiffened up appreciably, fairly tight turns were still possible

At 420 mph, the E series wouldnt be capable of that.

[Soren]

109 test pilots, Russians included, have said that the 109 had pretty good roll at higher speeds - again not as good as the 190s, P-51 or P-47 - but it maintained a good lateral control ability. Recovering from extremerely fast 750-900 km/h vertical dives was the problem - not level flight or even normal combat flying.
Spitfire and a 109 had equal roll rates at up to 400 mph speeds. Not even the favourite warhorse of the Americans, P-51, exactly shined with its roll rate at high speeds. As I've told before P-51 pilots have actually said that flying P-51 at high speeds was like driving a truck.

An often quoted British report made of an Bf-109 E talks about the "short stick travel", "due to the cramped cockpit a pilot could only apply about 40 pounds side force on the stick" and "at 400 mph with 40 pounds side force and only one fifth aileron displaced, it required 4 seconds to get into a 45 degree roll or bank. That immediately classifies the airplane as being unmaneuverable and unacceptable as a fighter."
The report claims that The 109-E needed 37lb stick force for a 1/5 aileron deflection at 400mph. Coincidentally, the Spitfire 1 required 57 lb stick force from the pilot for similar deflection at similar speed. This is a 54% higher stickforce for the Spitfire pilot.
The British test is taken as gospel by many, while it is just one test, made by the enemy, using a worn out and battle damaged airframe. German flight tests report pilots using aileron forces of over 45 lbs and 109's stick was designed for elevator stick forces of up to or over 85kg, over 180 lbs. So it was more matter of the pilot and the test procedures, than maneuverability of the Bf 109. Several details of that test are suspicious and German chief test pilot Heinrich Beauvais disagreed with it and with Eric Brown. Beauvais tried to get into contact after the war with Eric Brown to discuss the matters, but Brown refused to discuss the 109 with him. This being the case, it seems that Brown wasn't willing to listen a pilot who'd flown more on the 109 than he ever had, and was more interested on believing his negative findings of the 109 than being proven wrong by an expert.

[KraziKanuK]

The British test is taken as gospel by many, while it is just one test, made by the enemy, using a worn out and battle damaged airframe.

Always like this 'worn out and damaged' line. :P As if the Germans did not fly older a/c or put a/c that had been damaged back into combat.

'Sorry Herr 109 but that belly landing you just did has put you on the retired list.'

A German a/c that had 60% or more damaged was considered a write-off. Less than 60% meant the a/c wwas repaired and put back into service.

[Soren]

Originally Posted by KraziKanuK

Always like this 'worn out and damaged' line. :P As if the Germans did not fly older a/c or put a/c that had been damaged back into combat.

A German a/c that had 60% or more damaged was considered a write-off. Less than 60% meant the a/c wwas repaired and put back into service.

Yes, but other British tests against 'used' enemy a/c's have been carried out with factory-fresh Spitfires. So It had to be mentioned.

[Soren]

IIRC the 109 E tested first Belly-landed on British soil, and was restored by the British for testing. So some stresses were caused to the body of the 109 E in question prior testing.

Soren the reason I say "on paper" is because you look at one aspect of a thing without looking at the whole of it. Take the slats for instance. Yes they will apparently come out at higher speeds with higher angles of attack. You then conclude that this makes for a turn advantage. The fact is, a high speed turn does not involve just elevator, it involves rudder and a bank angle. Tests clearly showed that in such a turn, the tendancy of one slat to deploy well before the other created a turn disadvantage, not an advantage. Pilots had to make their high speed turns such as to avoid a slat popping out, and if it did, they had to release the stick for several seconds to allow it to go back in and then recover control.

Furthermore, slats were advantageous if the fueslage weight far exceeded the weight distrubuted to the wing. When the wing weight was relatively high, they tend to cause near or totally unrecoverable flat spins.

Finally, the 109F may or may not have turned as well as the Spit V, that is a debatable point. What is not debatable is the fact that the Spit V had twice the firepower of the 109F, was much more rugged, had much better range, and the pilot's visability was considerably better.

When it comes to rate of roll, the 109's were inferior at high speeds to almost all contemporary allied fighters.

As for the "flettner tab", more commonly called a trim tab, yes of course I've heard of them. But this was by no means unique to the 109, and in fact German trim-tab technology was no where near as advanced as Allied trim tab technology - visit the NACA library for proof of this.

And if you read about the 109 and its ability to pull out of a dive, the trim tab had to be set all the way toward climb to do so. More importantly, in a high speed dive the 109 was totally unstable as a gun platform starting, if I recall correctly, below 400 IAS (I think it was 375 IAS).

=S=

Lunatic

[KraziKanuK]

The Flettner was a not trimable. It moved in the opposite direction to what the rudder moved. It was used to decrease the 'work load' for the pilot at high speeds.

Originally Posted by KraziKanuK

The Flettner was a not trimable. It moved in the opposite direction to what the rudder moved. It was used to decrease the 'work load' for the pilot at high speeds.

That's what a trim tab is. It is a small fin on a bigger fin that helps the pilot to hold the bigger fin in the desired position. To trim the rudder to the left for instance, the trim tab is deflected to the right. Several types of trim tabs existed, some simply added force against the fin itself, others were balanced against the levers that operated the fin, and others involved springs to dampen the effect (sometimes these caused an increase in flutter).

Trim tabs were nothing new, they'd been around since WWI. The NACA has a number of WWII documents concerning trim tabs of various kinds, including balanced trim tabs and spring balanced trim tabs.

What the German's never found was the "seal balanced" aileron. Without high pressure wind tunnels there was no reasonable way to research aileron behavior at high speeds.

=S=

Lunatic

[Soren]

Yes they will apparently come out at higher speeds with higher angles of attack. You then conclude that this makes for a turn advantage.

That is because it 'is' an advantage in a T&B fight.

The fact is, a high speed turn does not involve just elevator, it involves rudder and a bank angle.

No'one ever said this. Offcourse a rolling maneuver must be achieved for a turn, and the 109F had an equal roll rate to the Spit V up to 400 mph, so it wasnt a problem.

Tests clearly showed that in such a turn, the tendancy of one slat to deploy well before the other created a turn disadvantage, not an advantage.

Oh no !! That is 'not' true ! This 'Myth' was started by Eric Brown, because the E series had a high tendency for the slats Jamming, but this was not their normal function. Also the F series had this jamming problem virtually eliminated.

Pilots had to make their high speed turns such as to avoid a slat popping out, and if it did, they had to release the stick for several seconds to allow it to go back in and then recover control.

Sadly only one man will agree with you on that... (Eric Brown) And Every modern day 109 pilot will disagree with him on that. And this downright inexperienced comment made by Brown was denied by virtually every 109 pilot still alive at the time, including Galland ! Not to mension Germany's chief test pilot, Heinrich Beauvais who even tried to contact Brown and correct his statement, but Brown refused to meet him ! He refused to be proven wrong by an expert !

The slats were there to increase maneuverability, not to hamper it. The slats were found beneficial in ALL situations. Why else do you think there were put on a 'Fighter' ?!

Walter Wolfrum, German fighter ace. 137 victories:

Unexperienced pilots hesitated to turn tight, because the plane shook violently at the moment when the slats deployed. I realised, though, that because of the slats the plane's stalling characteristics were much better than in comparable Allied planes that I got to fly. Even though you may doubt it, I knew the Bf109 could manouver better in turnfight than LaGG, Yak or even Spitfire."


Erwin Leykauf, German fighter pilot, 33 victories:

The Bf 109s also had leading edge slats. When the 109 was flown, advertently or inadvertently, too slow, the slats shot forward out of the wing, sometimes with a loud bang which could be heard above the noise of the engine. Many times the slats coming out frightenened young pilots when they flew the Bf 109 for the first time in combat. One often flew near the stalling speed in combat, not only when flying straight and level but especially when turning and climbing. Sometimes the slats would suddenly fly out with a bang as if one had been hit, especially when one had throttled back to bank steeply. Indeed many fresh young pilots thought they were pulling very tight turns even when the slats were still closed against the wing. For us, the more experienced pilots, real manoeuvring only started when the slats were out. For this reason it is possible to find pilots from that period (1940) who will tell you that the Spitfire turned better than the Bf 109. That is not true. I myself had many dogfights with Spitfires and I could always out-turn them.
One had to enter the turn correctly, then open up the engine. It was a matter of feel. When one noticed the speed becoming critical - the aircraft vibrated - one had to ease up a bit, then pull back again, so that in plan the best turn would have looked like an egg or a horizontal ellipse rather than a circle. In this way one could out-turn the Spitfire - and I shot down six of them doing it."


Galland about the 109's leading edge slats:

"Novice pilots tended to be thinking they should back off their turn when they deployed, but really it was just a booster to turn-performance"

Furthermore, slats were advantageous if the fueslage weight far exceeded the weight distrubuted to the wing. When the wing weight was relatively high, they tend to cause near or totally unrecoverable flat spins.

Eric Brown

And if you read about the 109 and its ability to pull out of a dive, the trim tab had to be set all the way toward climb to do so. More importantly, in a high speed dive the 109 was totally unstable as a gun platform starting, if I recall correctly, below 400 IAS (I think it was 375 IAS).

I guess you havent read the AFDU's tests with the 109F i presented, so i will quote it again.

AFDU 28 October 1941: TACTICAL TRIALS Me.109F AIRCRAFT- 7:

No manoeuvrability trials were carried out against other aircraft but the Me.109F was dived up to 420 mph, IAS, with controls trimmed for level flight and it was found that although the elevators had become heavy and the ailerons had stiffened up appreciably, fairly tight turns were still possible.

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In many aspects the Messerschmitt 109 is a much better fighter than people usually make of it. It has some of the legendary "how did they think of that", high-tech-like, aspects as North American P-51 and Supermarine Spitfire had. While Spitfire had the much vaunted elliptical wing (effect of which is only theorectical), the P-51 had its (again , much debated) laminar flow wing (trapeze in this case) and a very interesting cooler arrangement with a device for splitting and separation of the "dirty" turbulent boundary layer, and the capacity to generate thrust by heating the air flowing through it to negate the otherwise very high cooler drag (again, much debated); 109 had some very nice aspects too.
109 had a hydraulically driven (fluid coupled) clutch driving its supercharger, which made it capable of avoiding wasting power at lower altitudes. At those altitudes normal gear+clutch driven supercharger equipped planes were wasting a significant amount of their HP compressing air which could not be used by the engine. Later 109s even had a two gear, fluid coupled supercharger which gave very good power up to 11km.Even a normal 109G could produce full power up to 7 km (around 21.000 ft) with a normal single-gear supercharger. This supercharger was a low tech (sic), single stage single gear (sic) device, while the Allied designers used up to two stage, intercooled (in some cases) two gear superchargers to achieve similar power as the simple fluid clutch.

Later on (P-38, P- 47, bombers) Allied designers used bulky and hard-to-manufacture turbo-superchargers to keep up with the latest German advances. The engine used by 109s (DB601, DB603, DB605) had a direct to chamber fuel injection. Daimler Benz engines could compete with British and US engines using high octane fuels and very hard alloys, while itself using only 87 octane fuel !.

As for some interesting details on the 109, it had a very interesting cooler arrangement that actually resembles very much that of the P-51. It happens that the coolers, which look like very small, are in fact embedded into the wings and have a very low wetted surface. Also they look like normal coolers which just dip into the airflow , but they are a bit more complex. The cooler is embedded in the wing so that a plate over the cooler would skin off the dirty boundary layer like in the P-51 cooler and let it pass , while using the "clean" air for cooling. This makes it possible to use less surface for cooling which means more speed. The similarities don't end here, just as in P-51 the cooler rear end has a plate designed to adjust the amount of air flowing through the cooler (it is opened and closed automatically or with manual override). The design of this flap seems quite the same as the one on P-51, which was designed to generate the "Meredith Effect". The Meredith Effect is actually a cooler acting like a jet engine. Jet engines are actually very simple, you have a compressor compressing air, fuel heating it and a nozzle turning the heat into momentum. In this case you have a cooler heating the air, the mouth of the cooler (and airspeed) compressing the air and the flap on the back working as a nozzle to convert heat to momentum. This effect could generate up to 300hp on the P-51 and it would in most cases (high speeds) almost zero out the drag of the cooler scoop.

On landing modern combat aircraft drop flaps and as they drop flaps, also their ailerons "droop" down to act as flaps for the rest of the wing. This same feature was also in the 109. The boost control on 109 was automatic up to the critical altitude of the supercharger (as was the mixture control). The oil cooler and cooler flaps were automatic (with manual override). The 109 tail was almost like the ones on modern fighters, the whole tailplane could be moved with trim.

As for ammunition, the Germans were ahead of their time. They used similar centrifugal fusing in the 20mm and 30mm shells that was common before the modern proximity fusing became available. They used thin-shelled cannon shells which could contain up to 4 times more explosive than normal shells. They used very high order explosives (compared to the ones Allied were using, HA41 and PETN against torpex).

Germans also realized that the most efficient way to kill an aircraft, in addition to penetrating it with armor piercing rounds (which do little damage unless they hit one of the important parts), is to make large holes with large explosive shells or to use incendiary ammunition to light the plane up. The incendiary devices used by the Germans were excellent and were made of materials like magnesium, elektron thermite and phosphor. Phosphor has the effect of lighting up in room temperature and in general burning everything if it is in contact with oxygen. Elektron thermite on the other hand (a mixture of magnesium and aluminium) burns at a VERY high temperature (so high that it will light up airplane aluminium).

Most German aircraft had electrically operated (fired) armament, which made selection of different weapons configurations and counting of ammunition easy. Some of the planes also had a mechanism to pneumatically reload guns when the trigger was released if the last shell was not fired. This made it possible to unjam the guns just by pressing the trigger repeatedly.

It was possible to change the whole engine and/or wings of a 109 standing on its wheels in a matter of a few hours with no special lifts (only a mechanical hoist was required).


All these things are very often forgotten !

[KraziKanuK]

Soren,

never hear of the injection 'carbs' used on American and British a/c engines?

There was well over 100,000 GE tc manufactured. Not that hard to manufacture. You should compare the size of a tc and and a sc.

The Spit used the Meredith Effect for its rads.

Late in the war the Germans were developing multi speed, multi stage intercooled engines. The Germans also had to use the bulky and heavy 'boost juice' (MW50, GM1) systems to achieve high power outputs.

I do like the fluid coupling for the sc.


RG,

the Flettner does nothing in 'balancing' the a/c for 'hands free' flight. The trim tabs do that.

Originally Posted by Soren

That is because it 'is' an advantage in a T&B fight.

Mis-quoting or intentionally putting a partial quote out of context as you have done hre is unacceptable Soren.

Originally Posted by Soren

No'one ever said this. Offcourse a rolling maneuver must be achieved for a turn, and the 109F had an equal roll rate to the Spit V up to 400 mph, so it wasnt a problem.

First off, the high-speed roll of the 109F was inferior even to that of the full wing Spit V's, but for clipped wing Spits it was not even close. If you study the Spit tests, there was a high degree of variance between roll rates of different planes, so some Spit V's may have rolled as poorly at speed as the 109F, but most rolled better.

In a high speed banked turn the inner wing will approach stall before the outer wing - therefore its slat will deploy first. To avoid this, the 109 pilot must execute steeper banks during the turn, which is often less optimal for turn rate.

Originally Posted by Soren

Oh no !! That is 'not' true ! This 'Myth' was started by Eric Brown, because the E series had a high tendency for the slats Jamming, but this was not their normal function. Also the F series had this jamming problem virtually eliminated.

Sadly only one man will agree with you on that... (Eric Brown) And Every modern day 109 pilot will disagree with him on that. And this downright inexperienced comment made by Brown was denied by virtually every 109 pilot still alive at the time, including Galland ! Not to mension Germany's chief test pilot, Heinrich Beauvais who even tried to contact Brown and correct his statement, but Brown refused to meet him ! He refused to be proven wrong by an expert !

You forgot Gunther Rall. He also comments on the issue of single slat deployment in turns. Must be a conspiracy to defame the 109!

Originally Posted by Soren

The slats were there to increase maneuverability, not to hamper it. The slats were found beneficial in ALL situations. Why else do you think there were put on a 'Fighter' ?!

Primarily to decrease stall speeds in level flight to allow lower takeoff and landing speeds. They were advantagous is low speed turns (below 200 IAS) but they also had drawbacks if the turn was not very precisely executed - something hard to do in a swirling dogfight.

Originally Posted by Soren

Eric Brown

Wrong - from "Advanced Restricted Report 3D29 - EFFECTS OF WING LEADING-EDGE SLOTS ON THE SPIN AND RECOVERY CHARACTERISTICS OF AIRPLANES", By Anshal I. Neihouse and Marvin Pitkin, NACA, April 1943.

The USA and Britain were well aware of leading edge wing-slats even before WWII. However, when adding up the advantages and disadvantages they choose not to employ them. It is interesting that the NACA had at least 3 studies on wing slats (prior to the end of WWII). The basic conclusion is that unless they are needed for takeoff/landing they are undesireable.

Originally Posted by Soren

I guess you havent read the AFDU's tests with the 109F i presented, so i will quote it again.

AFDU 28 October 1941: TACTICAL TRIALS Me.109F AIRCRAFT- 7:

No manoeuvrability trials were carried out against other aircraft but the Me.109F was dived up to 420 mph, IAS, with controls trimmed for level flight and it was found that although the elevators had become heavy and the ailerons had stiffened up appreciably, fairly tight turns were still possible.

I've read the accounts of numerous German pilots saying that to pull the 109G out of a hard dive it was necessary to trim it fully for the climb. Furthermore, in such a high speed dive the 109 had to travel rather strait. The P-51 and P-47 were known to easily escape a 109 or 190 by excuting a corkscrew dive - if the German plane tried to follow, the P-51 or P-47 would easily end up on his six.

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Originally Posted by Soren

In many aspects the Messerschmitt 109 is a much better fighter than people usually make of it. It has some of the legendary "how did they think of that", high-tech-like, aspects as North American P-51 and Supermarine Spitfire had. While Spitfire had the much vaunted elliptical wing (effect of which is only theorectical), the P-51 had its (again , much debated) laminar flow wing (trapeze in this case) and a very interesting cooler arrangement with a device for splitting and separation of the "dirty" turbulent boundary layer, and the capacity to generate thrust by heating the air flowing through it to negate the otherwise very high cooler drag (again, much debated); 109 had some very nice aspects too.
109 had a hydraulically driven (fluid coupled) clutch driving its supercharger, which made it capable of avoiding wasting power at lower altitudes. At those altitudes normal gear+clutch driven supercharger equipped planes were wasting a significant amount of their HP compressing air which could not be used by the engine. Later 109s even had a two gear, fluid coupled supercharger which gave very good power up to 11km.Even a normal 109G could produce full power up to 7 km (around 21.000 ft) with a normal single-gear supercharger. This supercharger was a low tech (sic), single stage single gear (sic) device, while the Allied designers used up to two stage, intercooled (in some cases) two gear superchargers to achieve similar power as the simple fluid clutch.

The fluid clutch is not all plusses either. At high altitudes, or after protracted use, the fluid heats up and starts to eat into peak power levels. And if the fluid heats up too much, the system fails and you have no supercharger at all. Probably not much of a problem on a plane that could maintain peak speeds for only 1-2 minutes.

Originally Posted by Soren

Later on (P-38, P- 47, bombers) Allied designers used bulky and hard-to-manufacture turbo-superchargers to keep up with the latest German advances. The engine used by 109s (DB601, DB603, DB605) had a direct to chamber fuel injection. Daimler Benz engines could compete with British and US engines using high octane fuels and very hard alloys, while itself using only 87 octane fuel !.

Actually, to be competitive they had to use the better grade fuel. Almost all data we see involves the better grade fuel, I think called C3 but I'd have to look it up to be sure. Also if you study German fuels a little bit, you will see that when run rich, they were not really that bad, the low octane rating really relates more to when they were run lean. They were not as good as US/British fuels, but that was as much due to fuel technology as anything else. The Germans never produced their own tetra-ethyl lead, they relied on a huge supply they'd purchased from the USA in the pre-war years (from none other but Prescott Bush!). When they ran out of this, after a year to a year and a half of war, they lacked a suitable replacement.

Ummm... "bulky and hard-to-manufacture turbo-supercharger"??? Impossible for the Germans to build, not so hard for the USA, which built more turbo-superchargers in just 3.5 years than Germany built combat aircraft in the 6 years of WWII plus those built prior to the war! And as for bulk, the turbo-supercharger was no more bulky than a supercharger unit of the same boost capacity, it was just a littlemore spread out because of the inter-cooler requirements. Look at the supercharger on the F4U-4, it is every bit as big as the turbo-supercharger on the P-47.

Originally Posted by Soren

As for some interesting details on the 109, it had a very interesting cooler arrangement that actually resembles very much that of the P-51. It happens that the coolers, which look like very small, are in fact embedded into the wings and have a very low wetted surface. Also they look like normal coolers which just dip into the airflow , but they are a bit more complex. The cooler is embedded in the wing so that a plate over the cooler would skin off the dirty boundary layer like in the P-51 cooler and let it pass , while using the "clean" air for cooling. This makes it possible to use less surface for cooling which means more speed.

The similarities don't end here, just as in P-51 the cooler rear end has a plate designed to adjust the amount of air flowing through the cooler (it is opened and closed automatically or with manual override). The design of this flap seems quite the same as the one on P-51, which was designed to generate the "Meredith Effect". The Meredith Effect is actually a cooler acting like a jet engine. Jet engines are actually very simple, you have a compressor compressing air, fuel heating it and a nozzle turning the heat into momentum. In this case you have a cooler heating the air, the mouth of the cooler (and airspeed) compressing the air and the flap on the back working as a nozzle to convert heat to momentum. This effect could generate up to 300hp on the P-51 and it would in most cases (high speeds) almost zero out the drag of the cooler scoop.

Not hardly....

First off lets look at the Bf109 scoop/cooling design:



As you can see the radiators are indeed quite small. The "boundary layer diverter" mechanism was a fix for a problem discovered on the E models. The radiator is mounted to the bottom of the scoops and the boundary layer is allowed to flow through a space between the top side of the radiator and the wing. This helps to avoid injestion of the turbulent boundary layer which makes the radiators more efficient than they would be if there were larger but no space was provided for the boundary layer. Because the boundary layer has to make a significant turn upward to follow the diverter, this is only partially effective and at high speeds as the boundary layer gets thicker and has more mass and as pressure builds in the scoop, the boundary layer still lifts off the bottom of the wing and around the scoop entirely resulting in the "gulping" effect. The boundary layer diverter design helps to get a little more efficiency out of the small scoops of the 109 but it hardly "solves" the issue. There is no significant thrust generated for a number of reasons which I'll cover further down.

Now lets look at the P-51 radiator-thrust design:



First off, as is quite apparent, the P-51 radiator is HUGE compared to the two scoop radiators of the Bf109. Furthmore, the radiator has three to four times frontal area of both Bf109 radiators combine, which makes it inherantly more efficient for transfering heat.

Next, lets consider the boundary layer diversion method. On the P-51 the scoop is spaced more than an inch and a half away from the bottom surface of the wing (this varied a bit through different models). This means the boundary layer misses the scoop inlet entirely and encounters no obstruction that could rip it away from the scoop inlet until it is well past the inlet. The problem is completely solved.

Now lets look at how the thrust system works. First high speed cold air enters the scoop and proceeds down a widening passage which acts as an expansion chamber. The expansion chamber futher cools the air, slows its velocity, and increases the pressure (I know this is counter-intuative but its true). Then the (relatively) slow moving air passes through the radiator grilling, which is designed in the form of little ">" shapped fins stretched over the tubeing to form a sort of one-way valve. The heated air then passes into a narrowing passage which acts as a compression chamber.

When air passes through the radiator it is heated unevenly. Air molecules which make contact with the radiator fin elements are super-heated. Those that pass mid-way between the elements are much less heated. These molecules exchange heat in the compression chamber. One hot molecule and one cold molecule take up less volume than two warm molecules (assuming the total heat energy level is the same). So the air in the compression chamber is being compressed by its momentum into the narrowing passage and at the same time it is expanding as the heat in the molecules is transfered from the hottest molecules to the cooler molecules.

Finally, the hot air is vented through the thrust nozzel, which is designed and regulated for pressure. This provides thrust. At medium-high to high speeds, the jet of air comming out the thrust nozzel is supersonic, which provides usable thrust beyond speeds where a prop is no longer able to provide much thrust. Not only that, but the stream of hot expanding air is directed right into the wake of the fuselage. This wake is where parasitic drag normally "sucks" the plane back, and is the biggest part of an airplane's drag. Just like a tracer bullet, the P-51's exhaust fills the vacuum wake and reduces drag.

The Bf109 cooling system lacks both an expansion chamber and a compression chamber. The cold boundary layer air is re-introduced into the radiator exhaust in the space behind the radiator, virtually eliminating the chances of producing much thrust from expanding air. The cooling flaps at the back of the scoops are not designed to sustain high pressures behind the radiator, nor to control the outflow to generate a supersonic thrust stream, they are there simply to regulate the radiators to prevent excess cooling, primarily in dives. And finally, the radiator exhaust does not flow into the fusealge wake to help cancel out the parasitic drag.

The 109 has no meaningful "Meredith effect" thrust!

Note: The "Meredith effect" explanation is incomplete, trying to attribute all of the advantage of the radiator design to the thrust generated. A good portion of the advantage was the projection of super-heated air into the vacuum wake of the fuselage, nullifying parasitic drag.

Finally, the "300 HP" equivalent claim is based upon comparison of the Spitfire IX with the P-51 in level flight at speeds of about 275 IAS. In fact, the thrust generated could be much higher. In a 400 mph IAS dive at medium altitude for instance, the thrust could equal 900 HP equivalent. Power generated declines a little with decreasing altitude (as ambient air temp rises). The thrust generated/parasitic drag cancelled has the same geometric relationship to speed as does drag. Therefore, the proper way to consider it is that it cancels out about 12-15% of the P-51's total drag (perhaps more, the only figure I've seen quoted by Schumed was that it cancelled out 90-100% of the cooling sytem drag - which could be as much as 20% of total drag).

Originally Posted by Soren

As for ammunition, the Germans were ahead of their time. They used similar centrifugal fusing in the 20mm and 30mm shells that was common before the modern proximity fusing became available. They used thin-shelled cannon shells which could contain up to 4 times more explosive than normal shells. They used very high order explosives (compared to the ones Allied were using, HA41 and PETN against torpex).

The German's used mostly PETN+TNT in their aircraft cannon shells, the British and Americans used mostly RDX+TNT. The two mixes are comparable, if anything RDX is superior but only a little.

As for "four times" as much as normal shells, well that way exagerated. The German 20mm 96g mine round carried 18 grams of HE. The much smaller Soviet ShVAK 65 gram round had 6.7 grams of HE. The 129 gram Hispano round was loaded with 11.3 grams of HE. Clearly, the thin-walled mine rounds carried about double the HE payload for the given round weight in the 20mm class. Even this is deceptive, since the projectile weight is relatively low for its actual size.

Furthermore, the "mine" rounds had several disadvantages. They had to be surface contact fused - the thin wall construction that allowed the larger HE payload also meant the round could not survive penetration. It also carried no appreciable sharpnel mass with it, relying solely on the HE content to do damage. On the 20mm rounds (and the Ausf. A 30mm rounds which were by far the large majority of 30mm's) the fuse required the nose of the round to be very flat giving poor ballistic performance. And finally, the weight of the round for its overall volume was low, giving poor sectional density for its size, again making for poor ballistic performance. And of course, about 25% of these rounds were duds and the duds were unlikely to do significant damage because they lacked both mass and espeically hardness. The extremely poor velocity retention of the rounds meant that at longer ranges they were quite likely to bounce off the target slightly before detonatiing.

In the 20mm class, the Hispano was the better overall cannon. Its rounds carried about 2/3rds the HE content and retained good velocity and ballistic characteristics. And they were able to support delay action fuses, allowing penetration into the target vitals before detonation.

No modern aircraft ammo follows the German "mine" concept of using a soft thin walled shell! So the term "ahead of their time" is really not applicable.

Originally Posted by Soren

Germans also realized that the most efficient way to kill an aircraft, in addition to penetrating it with armor piercing rounds (which do little damage unless they hit one of the important parts), is to make large holes with large explosive shells or to use incendiary ammunition to light the plane up. The incendiary devices used by the Germans were excellent and were made of materials like magnesium, elektron thermite and phosphor. Phosphor has the effect of lighting up in room temperature and in general burning everything if it is in contact with oxygen. Elektron thermite on the other hand (a mixture of magnesium and aluminium) burns at a VERY high temperature (so high that it will light up airplane aluminium).

White Phosporous is not a great incendiary filler, except in anti-personel rounds. The material is hard to handle and subject to spontaneous ignition prior to firing. When it is delivered, it has no burst capacity, it fizzles. It also is highly subject to being lightly dispursed if added to an HE type round. And it tends to blow away in windy environments. WP requires ambient oxygen, something not readily available at high altitudes. And finally, it is relatively light, so it is kind of wasteful in terms of volume occupied. WP was not a good incendiary for anti-aircraft ammo.

Elektron, ~50% aluminum + ~50% magnesioum, was not "thrermite", which is powerdered or granulated aluminum and iron-oxide. Elektron was also inferior to the US incendiary metal compositions. IM11 (.50 M1 Incendiary and M8 API) was composed of ~25% aluminum + ~25% magnesium + ~50% barium-nitrate, in the form of an alloy. Like Elektron IM11 burns at about 4000-4500 degrees F, but unlike Electron it ignites easily when both heated (by fireing) and compressed (by striking the target), it requires no abmbient oxygen, and when it bursts it burns uniformly (i.e. it all goes up at once), giving a few seconds of intense heat as opposed to the slow burning Elektron. IM28 (.50 M23 Incendiary) was an alloy composed of ~25% aluminum + ~25% magnesium + ~50% potassium perchlorate, and burns even more viciously than IM11. Both Incendiary Metal alloys include a strong oxidizer (barium-nitrae or potassium perchlorate) which Elektron lacked. The Germans even tried to duplicate IM11, but failed to create an alloy of the materials in usable quantities. They also tried using the formula by mixing ~25% aluminum powder + ~25% magnesium powder + ~50% barium-nitrate powder, bound with wax, but of course this did not work very well as you cannot "crush" a goo to generate combustion, so they had to add HE, which of course over-disperses the incendiary.

The ability to use IM11 was one of the main reasons the USA felt okay about sticking with the .50 BMG. They had a superior incendiary round.

For fighter vs. fighter combat, 6 x .50's were much superior to 1 x MG151/20's + 2 x MG131 13mm guns. They had a huge volume of fire advantage and a significant ballistics/range advantage and more than enough killing power to quickly take out any enemy single engine fighter.

Originally Posted by Soren

Most German aircraft had electrically operated (fired) armament, which made selection of different weapons configurations and counting of ammunition easy. Some of the planes also had a mechanism to pneumatically reload guns when the trigger was released if the last shell was not fired. This made it possible to unjam the guns just by pressing the trigger repeatedly.

Gun rechargers rairly worked! The recharger was necessary because of the electrically primed ammo, which was prone to stoppages for a dude primer or (more often) bad primer contact. Also, the nature of the Mauser gun meant that after firing, it could fail to load the next round, so they needed the rechargers for this reason.

Even so, German jam rates (gun not able to be recharged) were never lower than British jam rates throughout the war, and usually they were higher (except the early Hispano period). Usually jamming resulted from problems with the feed mechanism or belt, which a recharger cannot fix. Percussion ammo was extremely reliable, so there was less need to "recharge" the guns to clear a dud round - this cannot be said for electrically primed ammo, which was very depenant upon a solid clean connection between the firing pin and the primer cap. A gun-bay is a dirty place.

The Hispano II also had a recharger. Some US planes also had rechargers for their .50's. But the jam rate on the .50 BMG was so low (1:4000 rounds fired) that rechargers were removed from later designs, they were deemed not worth the weight. The recharger was removed from the Hispano V, which had a 1:1500 rounds fired jam rate, again it was deemed not worth the weight. Typical jam rates for the MG151/20 were something around 1:1000, and for the MK108 something around 1:200-300, and the German pilots were even taking care not to fire under high-G to prevent jams!

Round counters were possible for percussion primed guns as well. But the Allies saw no significant advantage in having them. Simply loading more tracers when the belts got low to signal you were running low was enough. From about mid '44 on most US pilots didn't use tracers, except to note the belts were running low. And only some guns on German planes had round counters - for instance on the Ta152 the MG151/20's have round counters, the MK108 does not.

The primary reaso