An aerofoil is chosen from what is known at the time for the use the plane is intended for. The Bf109 was designed for a short range fighter with a 650BHP engine at the start. Research into laminar flow showed that a wing could be thicker and have less drag in a certain speed range. The P-51D was also obsolete in terms of airfoil technology when introduced, Jets were in service with the USA , Germany and UK the speed of military combat had just jumped by 100MPH and transonic /supersonic performance was the new-new thing.
Why was the BF109 so slow compared with the P51?
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For the Fw 190/Ta 152 - this table, although it needs come math to come to the Cd0 (Cw0 in German).
Namely, take the equivalent flat plate for max speed (that is 0.485 m^2 for the Fw 190A-8 and A-9), and divide it with wing area (18.3 m^2 for the two) = 0.0265. For the Fw 190D-9: 0.444/18.3= 0.02426.
I do not know much about the differences but the it seems not that much of it between the Anton and the Dora. I would have expected more drag advantage for the Dora.
Having 10% more drag (A-8 vs D-9) is big - that big difference in drag will net you far greater speed difference than, for example, a 10% less power or thrust.
Other 'ingredients' that made D-9 faster than A-8 were power at altitude (100+ HP at 5.7 km without ram; more with ram), a bit more exhaust thrust (150 kg vs. 120kg, all max figures for 'Notleistung'), and a better ram air intake.
Other 'ingredients' that made D-9 faster than A-8 were power at altitude (100+ HP at 5.7 km without ram; more with ram), a bit more exhaust thrust (150 kg vs. 120kg, all max figures for 'Notleistung'), and a better ram air intake.
Deleted member 68059
Staff Sergeant
- 1,058
- Dec 28, 2015
I would like to point out to nobody in particular, just as an interesting aside - that I think its not wise to expend too much effort
on looking at top speeds of late model German fighters. They were so badly assembled, that it was reckoned that
a typical fighter made in the "Jäegerstab" era (basically early 1944 onwards) was up to 40km/h under its "design speed"
due to appauling build standards of both airframes and engines. In interrogations of leading German aviation personalities in 1945, they stated that
this was the main reason for the very late acceptance of +1.98 ata (and even above) on the DB engine, even though the
engines were not really cut out for it, because the terrible build standard meant that the planes were basically worthless
with the factory spec engine power, and were not even as fast as the previous versions.
You can of course compare orginal factory tests with resonable confidence, as the first prototypes probably did just about perform
as expected, but looking any any data from captured test-flights, or pilots stories and combat reports is likely to bear virtually
no resembance to the actual potential of the airframes under "normal" circumstances.
In addition huge numbers were running de-rated engines for B4 even if they were specified as C3 only engines (i.e. lowered boost).
The above is all in the British Air Intelligence A.I.2(g) files in Kew, London.
on looking at top speeds of late model German fighters. They were so badly assembled, that it was reckoned that
a typical fighter made in the "Jäegerstab" era (basically early 1944 onwards) was up to 40km/h under its "design speed"
due to appauling build standards of both airframes and engines. In interrogations of leading German aviation personalities in 1945, they stated that
this was the main reason for the very late acceptance of +1.98 ata (and even above) on the DB engine, even though the
engines were not really cut out for it, because the terrible build standard meant that the planes were basically worthless
with the factory spec engine power, and were not even as fast as the previous versions.
You can of course compare orginal factory tests with resonable confidence, as the first prototypes probably did just about perform
as expected, but looking any any data from captured test-flights, or pilots stories and combat reports is likely to bear virtually
no resembance to the actual potential of the airframes under "normal" circumstances.
In addition huge numbers were running de-rated engines for B4 even if they were specified as C3 only engines (i.e. lowered boost).
The above is all in the British Air Intelligence A.I.2(g) files in Kew, London.
For an Me 109GG the following speed improvments were possible compared to an standard aircraft operating a 1.3 ata boost at 0 meters altitude at around 483km/h
Streamlined cowling to smooth over MG131 bulges 483km/h-> 489km/h +6 km/h 1.24% (Test Carried out on a G6 with MG131 gun bulges)
Fully Retractable Tail wheel..........................................…...…...494km/h-> 506km/h +12km/h 2.37% (Test Carried out on a G1 without bulges)
Fully covered wheels..........................................………..506km/h-> 516km/h +10km/h 1.97% (Test Carried out on a G1 without bulges)
Percentage......................................................................................................…...........Total 5.58%
The effect on a 397mph Me 109G6 at 1.42 ata is 397 mph x 1.0558 = 419.15 mph.
Kurfürst - Influence of the shape the engine cowling on the level speed of the Me 109 G and
Kurfürst - Leistungzusammenstellung Me 109 G. (no English version so)
It should be noted that the P-51D had all these features : retractable tail wheel, fully covered wheels and of course no gun bulges. With fairly minor modifications that Me 109G6 could have been 22mph 35km/faster but production priorates were put ahead of quality and Luftwaffe pilots had to suffer.
The lack of a high altitude supercharger explains the rest of the speed gap. When the Me 109K4 came into service it had all of these features plus and enlarged supercharger and the speed was the same at around 20,000ft-25000ft. The P-51 was superior at sea level.
The P-51 Laminar flow wing was superior to the Me 109's but this manifested itself only in the thick air of low altitude where the lower parasitic drag of the P-51 was unbeatable. The laminar flow wing was only slightly more laminar and this was not a big advantage but it had 2 big advantages: 1 It had a much higher mach limit which meant that the rise of compressibility or shock wave drag was less at the speed the Mustang operated which was Mach 0.55 (at sea level) to Mach 0.66 (at 30,000ft), it was this rather than laminar flow that made the mustang more efficient. it also helped stop the ailerons from locking up from compressibility and helped the P-51 have a high roll rate. 2 The other factor was that the wing was much thicker which allowed space for the fuel which gave the range the P-51 was famous for. This also allowed a stiffer wing.
The Germans understood laminar flow technology and 3 aircraft were planed with laminar flow wings: the Me 309 (all their own work), the Blohm and Voss BV.155 and a planed improved version of the Dornier Do 335. The work on the Me 309 was all their own. The Japanese also introduced several laminar flow wing aircraft.
The Hawker Tempest had laminar flow wings, the thickest point was a little further forward than the P-51 and the wing cross section of the Tempest seems the same as the Me 262 to me.
The follow on of the Me 109K4 was the Me 109K6 which incorporated two MK108 30mm integrated wholly inside the wings. I suspect this would allow an elimination of the cowling guns or at least a return to rifle calibre machine guns. The Me 109K14 had a two stage supercharger (without intercooling but with water injection) and was expected to reach 457mph.
So apart from range the Me 109 remained theoretically competitive. It was clear it was on its way out. Yes the Mustang (and Tempest) was superior but remember the same cant be said of other allied fighters such as P-47, P-38 (superior high altitude performance due to turbo-superchargers) nor the Typhoon or Spitfire or Hurricane or P-40 or P-39.
Streamlined cowling to smooth over MG131 bulges 483km/h-> 489km/h +6 km/h 1.24% (Test Carried out on a G6 with MG131 gun bulges)
Fully Retractable Tail wheel..........................................…...…...494km/h-> 506km/h +12km/h 2.37% (Test Carried out on a G1 without bulges)
Fully covered wheels..........................................………..506km/h-> 516km/h +10km/h 1.97% (Test Carried out on a G1 without bulges)
Percentage......................................................................................................…...........Total 5.58%
The effect on a 397mph Me 109G6 at 1.42 ata is 397 mph x 1.0558 = 419.15 mph.
Kurfürst - Influence of the shape the engine cowling on the level speed of the Me 109 G and
Kurfürst - Leistungzusammenstellung Me 109 G. (no English version so)
It should be noted that the P-51D had all these features : retractable tail wheel, fully covered wheels and of course no gun bulges. With fairly minor modifications that Me 109G6 could have been 22mph 35km/faster but production priorates were put ahead of quality and Luftwaffe pilots had to suffer.
The lack of a high altitude supercharger explains the rest of the speed gap. When the Me 109K4 came into service it had all of these features plus and enlarged supercharger and the speed was the same at around 20,000ft-25000ft. The P-51 was superior at sea level.
The P-51 Laminar flow wing was superior to the Me 109's but this manifested itself only in the thick air of low altitude where the lower parasitic drag of the P-51 was unbeatable. The laminar flow wing was only slightly more laminar and this was not a big advantage but it had 2 big advantages: 1 It had a much higher mach limit which meant that the rise of compressibility or shock wave drag was less at the speed the Mustang operated which was Mach 0.55 (at sea level) to Mach 0.66 (at 30,000ft), it was this rather than laminar flow that made the mustang more efficient. it also helped stop the ailerons from locking up from compressibility and helped the P-51 have a high roll rate. 2 The other factor was that the wing was much thicker which allowed space for the fuel which gave the range the P-51 was famous for. This also allowed a stiffer wing.
The Germans understood laminar flow technology and 3 aircraft were planed with laminar flow wings: the Me 309 (all their own work), the Blohm and Voss BV.155 and a planed improved version of the Dornier Do 335. The work on the Me 309 was all their own. The Japanese also introduced several laminar flow wing aircraft.
The Hawker Tempest had laminar flow wings, the thickest point was a little further forward than the P-51 and the wing cross section of the Tempest seems the same as the Me 262 to me.
The follow on of the Me 109K4 was the Me 109K6 which incorporated two MK108 30mm integrated wholly inside the wings. I suspect this would allow an elimination of the cowling guns or at least a return to rifle calibre machine guns. The Me 109K14 had a two stage supercharger (without intercooling but with water injection) and was expected to reach 457mph.
So apart from range the Me 109 remained theoretically competitive. It was clear it was on its way out. Yes the Mustang (and Tempest) was superior but remember the same cant be said of other allied fighters such as P-47, P-38 (superior high altitude performance due to turbo-superchargers) nor the Typhoon or Spitfire or Hurricane or P-40 or P-39.
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It's about a 9.2% lower drag for the Dora which equates to about 3% speed advantage using a cube root law . That's about 12mph from a 408mph base. The BMW801 and Jumo 213A were operating at about the same power levels at this time (2000-2050 for the BMW and 2100 for the Jumo ) and so the air mass flow was about the same but the Jumo was operating at both higher RPM and higher boost levels due to its lower displacement and I suspect this gave higher jet thrust.
The "laminar wing profile" didn't give it a higher mach limit, but what it did do was it provided less or no nose tuck at high speed. At high alt. (30,000+ ft) the 109's wing was bearly able to handle the thin air without stalling in maneuvers I've heard, which makes sense to me.
swampyankee
Chief Master Sergeant
- 4,036
- Jun 25, 2013
Because of the 6-series airfoils' pressure distribution, they tended to have a high critical Mach number; this was a consequence of the pressure distribution used to maximize the region of laminar flow. The 16-series airfoils were designed for regions of barely supersonic flow (see http://web.stanford.edu/~cantwell/AA200_Course_Material/The NACA airfoil series.pdf), but was little used except on propellers. The 6-series airfoils also tended to have quite limited regions of low drag, usually only ±0.1 from the design lift coefficient. Airfoils with better off-design characteristics would have to wait for a few decades.
drgondog
Major
Tomo - you have rightly commented on most of Greg's Faux pas
manta22
Banned
"...manifold pressure is also a function of compression ratio,..." To clarify, manifold pressure is a function of supercharger compression ratio (boost) but not of engine compression ratio. That is cylinder pressure (BMEP).
Most of their mistakes was due to misunderstanding Youtube experts.
drgondog
Major
If I hear the phrase Laminar Flow wing again, I will stamp my feet with hands on hips - and glare. Then I will seek a 'safe place' or transition clinic.
If you wear a coloured wrist band and light a candle, it helps.
Shortround6
Major General
only if it is the right color and/or shade to compliment the scent of the candle
Shortround6
Major General
Since they have eliminated "strongly worded letter to the TIMES" one's options are limited
