Best Messerschmitt Bf109 subtype

[Soren]

Claidemore,

It's the thickness ratio which matters, thickness of the wing in comparison to the wing chord, as the higher the TR is the higher the Clmax is. A higher thickness ratio means a higher critical AoA and Clmax.

[Soren]

I'm not trying to confuse you Claidemore, what I'm trying to tell you however is that the stall speed is lowered by the thrust of the propeller accelerating air over the wings faster than freestream - in effect increasing the Clmax. You do understand that lift is a byproduct of speed right ?

But lets see:

Weight: 3,855 kg
Wing area: 22.48 m^2
Stall speed: 136.7 km/h

1 * 22.48 * .5 * 37.9984^2 = 16,229.1932 N (1,654.91 kgf)

3,855 / 1,654.91 = 2.32

Thus the Clmax is 2.32 in that condition... But again this isn't freestream, it's with the engine & prop producing a lot of thrust and pushing air faster over the wings, affecting the calculated Cl value.

Thus the Clmax of the wings can't be calculated by using such stalling speeds, you need freestream windtunnel tests to establish the Clmax.

[Soren]

By comparison the Bf-109E has a stalling speed of 74 mph with flaps and gear up, and 61 mph with gear and flaps down.

Stalling speed of the Bf-109 K-4 was around 83 mph with flaps and gear up.

[claidemore]

Hawker Typhoon had a very high TR, but it did not turn as well as the Spitfire. The Tempest employed a thinner wing, with similar turn performance compared to the Typhoon.

IF the 109E stalled in level flight, engine off, at 74mph, the Cl would be 2.32, which is ridiculously high. At 84mph for the 109K4 the CL would be 2.4, an even higher number! Sorry, but those numbers just don't fly. (pardon the pun)

Plug in the cl of 1.7 into the equation, and you get 86 mph stall speed. In the RAE Spit1/109E comparison charts they indicate a stall speed for the Spit 1 around 75mph and the 109E at around 90mph TAS. Those charts also show the 109 stalling at higher speeds at equivalent G factors, at a contstant rate. We can argue about the accuracy or bias of those charts, but since there are no other charts offering different results, if we discount them we are left with only speculation and opinion.

The only thing that changed from the time of the RAE test and 1944/45 was the power loading and a clean up of the airframe on the 109. K4 had a very high power loading for the 1.98 ata engines, but very few of them made or used, so we have to look at 1.8 ata or less. Even with a small advantage in power loading for the K4 over Mk IX or XIV, keep in mind that the Emil had a power loading advantage over the Spit I, and all trials indicate better turn performance for the Spit I.

Spitfires are given a turn superiority throughout its developmental history against 109s by, 1)tests and trials by RAF and Luftwaffe, 2)anecdotal evidence from majority of RAF/USAAF and Luftwaffe pilots, 3)mathmatics. The changes in the K4 would give it a better turn performance than G6 models, but are certainly not improvements in a scale that can enable it to outperform the Spitfire.

To state that the 109K4 had better turn performance than the latest Spitfire Marks is simply wishful thinking, relying on the faulty logic that if it's better than it used to be, it must have made a quantum leap and be able to turn better than the Spitfire. That is just too big a stretch.

No one has offered any conclusive evidence to back the statement up while there is considerable evidence to the contrary.
Claidemore

[Soren]

Claidemore you're completely wrong.

As for he calculation in my post, that was for the Spitfire Mk.XIV, not the 109E, and if the stalling speed was 137 km/h then the Clmax is calculated as 2.32in that condition. (With engine running ofcourse)

The stalling speeds of the 109E are as stated 74 mph flaps and gear up, and 61 mph gear & flaps down, and this is from the Dash 1 (POH).

As for the Typhoon vs the Tempest, well the Typhoon does turn better, and this is despite having less wing area and weighing more, and you can thank the higher thickness ratio wing for that.

[Soren]

IF the 109E stalled in level flight, engine off, at 74mph, the Cl would be 2.32, which is ridiculously high. At 84mph for the 109K4 the CL would be 2.4, an even higher number! Sorry, but those numbers just don't fly. (pardon the pun)

Ha! They certainly fly better than the 2.32 Clmax for the Spitfire !!

PS: As already explained a Clmax of 2+ isn't unormal at landing speeds as the prop accelerated air much faster over the wing than freestream leading the Cl estimation to be higher.

Therefore, I repeat, we can't use stalling speeds as a reference here as it depends on two factors, 1) the Clmax freestream 2) the thrust provided by the prop. Thus you need the freestream figures for comparisons, and as explained the Clmax for the different a/c are as follows:

Bf-109F/G & K: 1.70
Ta-152H: 1.62
FW-190: 1.58
P-51: 1.35 (According to NACA)
Spitfire: 1.36

[Udet]

Whatever the turn rate of any Spitfire version might have been, German fighter pilots feasted with the almighty Spit.

Ask RAF for Spitfire losses for 1941, 1942 and the first of months of 1943 [pre-8th Air Force assembly era], when a gross slaughter of British pilots took place.

[claidemore]

I can 'prove' your CL figure for the 190 as being correct, but the same formula does not 'prove' the 1.36 for the Spitfire. Sorry, but that number is incorrect.

Even the clipped wing Spitfire IX/XVI had a CL of 1.5.

I've seen that 1.36 number on a gaming forum, tested the formula that was supposedly used to get it and it didn't work.

As for stall speed, it is arguably the most important factor in max turn rate, particularly in combat situations. We have to use it as a reference. It is also one of the numbers we must have to calculate CL, and one of the numbers we can calculate if we already have CL. Thus, knowing the CL of the 109 as being 1.7, we can calculate stall speeds that are in all cases higher than those you have indicated for 109s, in the case of the 3400 kg 109K4 the stall speed is 100 mph.

[Soren]

I can 'prove' your CL figure for the 190 as being correct

You can ? please do then cause I know the true stall of the Fw190 and it aint the one in the RAE report, that bird as already noted suffered from ill adjusted ailerons.

[Soren]

Originally Posted by claidemore

I can 'prove' your CL figure for the 190 as being correct, but the same formula does not 'prove' the 1.36 for the Spitfire. Sorry, but that number is incorrect.

Even the clipped wing Spitfire IX/XVI had a CL of 1.5.

I've seen that 1.36 number on a gaming forum, tested the formula that was supposedly used to get it and it didn't work.

As for stall speed, it is arguably the most important factor in max turn rate, particularly in combat situations. We have to use it as a reference. It is also one of the numbers we must have to calculate CL, and one of the numbers we can calculate if we already have CL. Thus, knowing the CL of the 109 as being 1.7, we can calculate stall speeds that are in all cases higher than those you have indicated for 109s, in the case of the 3400 kg 109K4 the stall speed is 100 mph.

Wrong wrong wrong and wrong.

The Bf-109 K-4 has a landing speed (Which is always a good deal higher than stall speed for obvious reasons) of 150 km/h for crying out loud!! 10 km/h below the speed you're wanting it to be stalling at !!

Do you want NACA's own papers on the Spitfire to show the Clmax of the Spitfire's wing ?? Ok, attached below it is.. The Clmax was establised as 1.18 to 1.15. There you go. So shall we use these figures or the British results of 1.36 ??

In short the only one suffering from wishful thinking is you Claidemore.

[kool kitty89]

If you use the true CL directly to determine stall speed, you'll get the stall speed in engine off condition (dead stick/ gliding) but as Soren said the prop wash adds considerable lift due to the higher speed of airflow. Engine at idle should give similar figures, though still very slightly skewed. (some added airflow will still be present, but not very significant; basicly negligable)

This is also why twin engine a/c ("twin slipstream) tend to turn better than single engine craft of similar configuration. Also why jets (and pusher props) stall a bit differently and why the taildragger configuration didn't work on the Me 262.

[Hunter368]

Good information KK

[claidemore]

The American test used an unreliable method of measuring stall speeds, hence the low CL figures they recorded. RAE used a trailing static head (very difficult in a single seat fighter and seldom done) to get much more accurate results on both the Spitfire and the 109. This alone gives the RAE tests of the 109 considerable value as far as stall and CL go.

RAE did record 1.36 CL in a glide, but 1.89 power on. This corresponds to the 1.95 they got for the 109 power on. Only a 4% difference. Basically, the slats on the small 109 wing only increased it's CL to slightly ahead of the Spitfires broad elliptical wing, not enough to overcome the 109s initial inferior wingloading, consequently the Spit always had a tighter turn, as recorded in tactical trials by both sides.

This did not change with the K4. It was an improved plane, not a completely redesigned one.

When I say 'prove', i mean using an equation to prove a number mathmatically, ie doing a calculation in reverse to make sure you get the number you started out with, I'm not using the word in a "I'll show you' context. Stall speed for FW 190 at 1.58 CL is 110 mph (P51B is 100 I believe?). Some sources give stall speeds as high as 127 mph for the 190, so 110 is pretty generous, though being generous in these discussions seems unpopular and possibly unwise. But then I'm not trying to change history, just trying to prove what has always been held to be true.

All the landing speed minimums I've seen for 109s are 180 kmh, thats gear and flaps down. Might hit 150 just as the pilot pulls the plane into a 3 pt attitude and touches down but doing approach speed at 150? Cripes, thats the approach speed of a Hurricane! You're not going to tell me the 109K4 could turn with a Hurricane are you?

On the Mk XIV, landing speed is 100 mph, clean stall speed is 85, 15 mph less. (incidently, they recomended landing 20mph faster for safety)

Knock 20 kmh off the 180kmh for 109 approach speed, and you get 160kmh for clean stall, a similar ratio as in the Mk XIV Spit example above. So I don't see anything wrong with my calculated stall of the K4 at 100mph. If there is an historical document that says otherwise, I'd love to stand corrected.

Other factors not included in a simple CL/stall calculation might put me out by a few kmh for that stall speed, but definately not in the 134 kmh area that you maintain.

Once again, that is the stall speed of a Hurricane! The Hurri and Spit were very close in turn rate, so if the 109 was turning circles around the Spit, was it kickin the Hurris butt too? I haven't seen anybody trying to prove that one...yet.

At the end of the day, despite haggling over CL and stall speeds, we still don't have any historical test or trial that gives any 109 model a better turn performance than any Spitfire. We do have trials that show the Spitfire turning better than FW, 109, Mustang, Tempest, Typhoon etc, in fact it was used as the standard by which to measure all the others.

[kool kitty89]

The 127 mph stall figure for the 190 was of ther early prototype with much smaller wing area and different wing plan form, and with the original BMW 139 engine. (albeit it was lighter a/c as well)

The first prototype, the Fw 190 V1 powered by a 1,550 hp BMW 139 two-row 14-cylinder radial engine, with civil registration D-OPZE, was flown on 1 June 1939 and soon showed exceptional qualities for such a comparatively small aircraft, with excellent handling, good visibility and speed (initially around 610 km/h (380 mph)).[8] The roll rate was 162 degrees at 410 km/h (255 mph) but the aircraft had a high stall speed of 205 km/h (127 mph). According to the pilots who flew the first prototypes, its wide landing gear made takeoff and landing easier, resulting in a more versatile and safer aircraft on the ground than the Bf 109. The wings spanned 9.5 meters (31 ft 2 in) and had an area of 15 m² (161.46 ft²).

This became excessive on the heavier V5 with similar configuration to production 190A's (but not the pre-production A-0's) but initially retaining the original wing:

At first the V5 used the same wings as the first two prototypes although, to make room for the bigger undercarriage, the wheel arches were enlarged by moving forward part of the leading edge of the wing root (in this form this prototype was called the V5k for kleine fläche/small wing). The V5 first flew in the early spring of 1940.

However, the weight increase was substantial, 635 kg (1,400 pounds), leading to higher wing loading and a deterioration in handling. As a result, following a collision with a ground vehicle in August 1940 that sent the V5 back to the factory for major repairs, it was rebuilt with a new wing, with a larger area, 18.30 m² (197 ft²) and span of 10.506 m (34 ft 5in) and which was less tapered in plan than the original design (the aircraft was now called the V5g for grosse fläche/large wing). This new wing platform was to be used for all major production versions of the Fw 190.

[claidemore]

Footnote: the RAE tests with trailing static head to measure stall and CLmax, gave a figure of 1.36 in a glide for the Spit 1, and 1.4 in a glide for the 109E. Static head indicated a speed at the stall for the 109 of 95.5 mph, cockpit instrument IAS was 75. This was with slats open, and they noted that both slats opened up simultaneously.

So comparing a cl of 1.7 for the 109 to 1.36 of the Spit, is comparing apples to oranges, the actual comparison derived using the same equipment under the same test conditions, is 1.36 to 1.4.

Or full throttle, 1.87 to 1.95.