Re: Papers: Meredith Effect and RR Merlin carburator T.O.


Geoffrey Sinclair wrote:
"Eunometic" <eunometic@xxxxxxxxxxxx> wrote in message
news:1150901219.862901.169140@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Geoffrey Sinclair wrote:
"Eunometic" <eunometic@xxxxxxxxxxxx> wrote in message
news:1150626295.263002.109440@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
(Incidently in research for this post I cam across the point that the
Me 109F may have been an extra-ordinarily efficient aircraft that
degenerated only as too much bulk in the form of armament, equipemnt,
armour and engines size was added, the Me 109F achieving 416mph on less
power than either Spifire or P-51

The big killers for airspeed were the large bulges added in order to
fit 13mm machine guns on the G series. Another source of extra
drag was the increased size of the landing gear tyres. This meant
small bulges in the upper wing surface but probably more drag was
produced by the fat the tail wheel was no longer retractable, it would
not fit into the cavity.

By the way the claim the Bf109F was a more efficient airframe than the P-51
is really wrong. The RFA figures for the P-51 show this, see below.

The airframe pulled about the same speed out of the same power as the
earlier allison engine machines albeit with a smaller airframe that had
less capacity for fuel, armour and future growth.

The G series (except for the G-0/G-1) had a longer stroke longer bored
DB605 engine instead of DB601. This engine was deeper but not longer
and drove the evolution of the bulges as much as the ammunition
requirements of the bigger guns in the 109-G6. It was the equivalent
of the Grifon. Neither the Me 109G1 with the DB601 nor the Me 109G-2
with the new DB605 had the bulges as it did not have the 13.2mm MG 131
machine guns. The other factor was the 'oversized' supercharger
impellor in the Me 109G-6 AS and Me 109G-6 ASM and DB605D of the K
series.

The main "bulges" were to allow the fitting of the 13mm machine guns.
Then came the bulges in the upper wing to allow for larger undercarriage
tyres. At least this is the ranking in terms of size.

The original bulges were a pair of intake scoops to provide cooling air
for the exhausts and spark plugs for the new engine of the G series.

So the new engines drove the ‘original’ bulges as much as the guns;
just as I said.
It’s simple really: the DB605 was a deeper engine than the DB601


The larger undercarriage was fitted officially from the G-4 onwards,
but often retrofitted to earlier G models.

It was enlarged yet again for K series, though the K lost the amunition
dump bin in the chin


The DB605 is the equivalent of what Griffon?

Yes Geoffrey, like in the IQ test: Merlin is to Griffon as DB601 is
the DB605: Both the bigger engines obtained much of their volume
increase through a substantially longer bore though the Merlin was much
smaller than the DB601 and the ancestor of the Griffon was not the
Merlin but the “R”engine.



Griffon 6, 1,850 HP at 2,000 feet, on 1,800 pounds weight?
Griffon 61, 2,035 HP at 6,000 feet, on 2,000pounds weight?
Griffon 72, 2,245 HP at 9,000 feet?
Griffon 83, 2,340 HP at 750 feet?

 The griffon was a 36.7 litre engine, the DB605 was 35.7 litres.

So the difference in swept volume was 2.8%.


The DB605A, B, C emergency rating 1,475 HP at sea level on 1,650
pounds weight.
The AM (Methanol injected A engine) emergency rating of 1,800 HP
at sea level.
The AS (A engine with bigger supercharger) emergency rating
1,435 HP at sea level.
The D, fitted with the bigger supercharger as standard.

If the engine designation has a C in it then the engine is using 96
octane, in effect the same as the allied 100 octane.

Nope. C3 fuel is nothing like allied 100 octane either early American
or British. It is either 92/110 and increased to 96/125 around mid
1944 coincident with a large increase in permisable boost pressures and
powers for the DB605 and BMW801.

http://www.fischer-tropsch.org/Tom%2...0Item%206A.pdf
http://www.fischer-tropsch.org/prima...ecificat ions


Around late 1944 British analysis of residual fuel in captured or
downed Luftwaffe aircraft started to show that C3 or “Green dyed”
fuel performance numbers increased to around 95/125. This is a well
short of 100/130. Prior to that the fuel had been analysed at 92/110
and 95/118 (approx). Some of the samples of fuel had RON octane
ratings of 95.5 or even 96 which is most certainly a case of the German
fuel plant trying to exceed the official standard of 95. Presumably
this is the origin of the 96 octane figure often quoted. So we have a
fuel officially rated 95 by the Luftwaffe being tested at 95.5 in a
British lab then being rounded up to 96. The 96 then is called 100
because someone though that is close to 100 used by allied fuel.
Likewise the rich stoichiometric rating of 125 is rounded up to 130.
Between the increase from 92/110 to 95.5/125 British analysis appears
to may have noted an intermediate rating increase of 95/118 or so. It
is not certain whether this is deliberate or just substandard C3.
This corresponds with the stories of the Germans tinkering with C3 at
least three times. Any German engine tuned to run on 100/130 would be
in trouble when running C3. Meanwhile the allies are using more
115/145 and 100/150 than the Germans 95/125 C3.

If you checked allied 100/130 or 115/145 or 100/150 fuel you no doubt
would find them generally of higher perfomance numbers then their
designation and I suggests though you would find them of more
consistent quality: allied refineries weren’t disrupted by bombing.

B4 or “Blue” Fuel tested at between 87 and 91 lean but only about
81 rich. In other words it wasn’t very fruitfull overboosting the
engine and controlling the resulting detonations by running the mixture
rich. This explains the early German perfection of MW50 (Methanol
Water 50%) injection. P-47 pilots were frightened of activating their
ethanol/water systems: the less effective ethanol mixture froze and
blew up their supercharger over enemy territory.

B4 was a fairly straightforward derivative of the German Hydrogenation
plants where a coal/oil slurry was pressurised with hydrogen at the
incredible pressure of 700 atmospheres. The aromatic and other
components to achieve the C3 rich mixture response had to be derived
from further refining and synthesis at considerable expense.

British 100 octane fuel was in fact quite different from american 100
fuel. The American fuel achieved its 100 lean rating by alkylation
(boradly increasing iso-actane or similar components). The British
fuels included aromatic compounds obtained from Venzuela, the Bahamas
and Brunei that gave a strong rich mixture response. It was these
components that the Germans had to learn to synthesise; not easy given
the amount of resources and trained personel dedicated simply to
develop coal to fuel synthesis. The specification is called BAM-100
“British Air Ministry”-100




So DB605ASCM, means the A engine, with the bigger supercharger,
96 octane and methanol injection.

 The DB605DC emergency rating was 2,000 HP at sea level.

This is on the higher rated C3 fuel of 96/125 as the engine was only in
service in 1944.


The Bf109s fitted with the bigger superchargers were also fitted
with redesigned cowlings, with larger but more aerodynamic
bulges. And the bulge on the left side was larger than that on
the right side, given the supercharger arrangement.

So the bigger superchargers resulted in what looks like a more
streamlined arrangement.

The bulges disappeared in the Me 109G-10, which was produced by WNF and
were significantly reduced on some or all series of the K.

The bulges certainly did not disappear with the G-10.

The fuselage bulges were greatly reduced.


The undercarriage bulges remained, indeed in some cases they
were increased as even larger tyres were fitted.

The cowling bulges were redesigned. The G-10 was meant to
take the larger supercharger.

If you look at the F models in flight you can see the tail wheel is
retracted but the G models it is usually fixed down. It took until
the K series in the final quarter of 1944 for the tail wheel to be
made retractable again.

I've never understood the reason for removal of retraction of the tail
wheel on the G while it was found on the preceding F series and the
succeding K series . Again some G series had a retractable tail wheel.

Me 109G-6 or even Me 109G-10 and Me 109G-14 are definitely not
homogenous even amongst themselves; initial runs of the models often
reusing parts from preceding models and progressively incorporating
upgrades sometimes from succesor models often depending on the
manufacture: Messerschmitt, WNF or Erla.

In the 1943/44 period the following improvements were introduced,

1) The change to the tailfin, a larger wooden structure that can best
be detected by the way the older style rudder made up the rear and
top of the fin but the newer style made up the rear only. Note the
new arrangement came with two rudders, with 1 or 2 flettner tabs.

2) A new canopy, the Vollsichthaube or Galland Hood, which can
easily be seen by the increase in glass area and reduction in
cockpit framing.

3) A new longer tailwheel strut best seen in pictures of aircraft on
the ground. The new strut was initially made semi retractable with
the ability to fully retract the entire tail wheel coming later, in the K
models.

4) The elimination of the bulges near the end of the engine cowling
that enabled the mounting of the 13mm machine guns, replacing the
bulges with a larger, smoother, oval shaped bulge that started around
where the machine gun muzzles appeared on top of the cowling and
finishing around the start of the cockpit canopy on the left hand side
and a smaller bulge on the right hand side. This is hard to see and
best detected by the absence of the previous, prominent bulges.
This was the result of fitting the DB605AS or the DB605 engine, the
DB605 was the main engine of the G-10 and K models, the DB601AS
was mainly a limited production run fitted to G-14 and late G-6 models.

The G-14 was meant to standardise the G series again, rather like the
G-6 was supposed to but the mutations had continued. As a result
it was the type most likely to have all the older features as built.

The K series was the new standard, and was supposed to have all the
new features as built.

The G-10 series was the G series fitted with as many of the new features
as possible, with the DB605D as the standard engine, in effect an
intermediate between the G-6/14 and K. The G-10 entered production
after the K series.

Now to state the obvious, the chaos in Germany in the final months of
the war meant the idea the various Bf109 types would be standardised
is clearly wrong. In effect there was a change over to the new features
mentioned above, along with the engine changes, but it is clear if the
only parts available were the older types, those were used, generally
for the G-14 models, keeping the new features for the G-10 and
especially the K models. It is also probable early machines received
late model features if they were being repaired and effectively in the
right place at the right time. So external features are no guarantee
of what model is really being shown. The best visual indicator is the
new fuselage bulges as it reflects the engine installation. The only
real way to tell is the werke number.

In effect the Bf109 models in production in 1944, the G-5, G-6, G-8,
G-10, G-14 and K all received some to all of the 4 changes I listed
above, the plan appears to have been fit the new canopy, tail and
tail wheel to all Bf109s, with the changes introduced gradually but
that ran into the chaos of late war Germany, leaving a mixture of
fittings. An example is the G-6 that landed in England in July 1944
which has the new tail but old tail wheel and canopy.

http://forum.axishistory.com/viewtopic.php?t=88361&postdays=0&postorder=asc&start=45

"Amazing that the 1942 Bf 109F-4 managed a top speed of 416 mph on a
1350 (1390?) hp DB601E engine, while the 1943 Spitfire IX (HF version),
weighing about 380 kg more than the 109F, needed a Merlin 70 of 1710 hp
to reach 415 mph.")

Now for some reality checks.

Please spare me from 'reality' checks in Sinclairs wonderland in future
please.

In other words the fiction is preferred.

It’s you fiction.


For start 380 kg is around 840 pounds or
pushing around a 20% increase on the empty weight of a Bf109F-4 and
10 to 15% of the maximum Bf109F-4 loaded weight.

The HF Mark IX used the Merlin 70 rated at 1,475 HP, top speed 416 mph
at 27,000 feet.

The F mark IX used a 1,565 HP Merlin 61 or 1,650 HP Merlin 63 for a top
speed of 408 mph at 25,000 feet.

The LF mark IX used a 1,580 HP Merlin 66 for a top speed of 404 mph
 >> at 21,000 feeet.

Note that two stage Merlins develop significantly more power than the
single stage Merlins at altitude.
We have the LF Mk IX running at 404mph at 21,000 feet.

This corresponds with an altitude of 6300m at which point the Me 109F-4
was doing the following speeds:
630-635kph 390-393mph @ 6000m/20000ft worst case (data probably
from F2 for climb/combat power.
660-670kph 409-415mph @ 6300m/21000ft best case (data form Me
109F-4 overboosted and using takeoff/emergency power)

Have a look at the HF Mk.IX with the Merlin 70. At 23,000/7000m feet
its engine is producing 1470hp which is slightly more than the DB601E
at its peak which is at 2200m (7300feet) its even more than the 1300hp
or so the 601E is producing at 4800m /16000ft or the 1070hp at
6300m/21000. At 7000m/23000ft, which is Merlin 70s peak output of
1470hp the DB601E is only producing 1000hp.

http://www.spitfireperformance.com/spit9v109g.html check both the
speed and peak power of the Mk IX at these altitudes. I suspect that
Spitifres higher boost means more exhaust gas thrust. Dynamic ram air
pressure would alter the power a little; generally improving it but
sometimes retarding it for both engines.

It’s much the same story with the two stage Merlin 66 and even the
single stage Merlin 45 which is also producing more power at these
altitudes.


The F mark IX empty weight was around 5,800 pounds, maximum
weight 7,500 pounds, maximum overload 9,500 pounds.

As can be seen from the above supercharging settings were more
important than HP ratings when it came to top speeds.

As you vaguely isuggest none of these numbers matter much as they are
seal level figures out of context since you do not reference the power
v height curves or even the full pressure altitude to put them in
context. This is a graphical or baysian argument not a binary one.
Two stage Merlins were powerfull relaive to the German opposition but
'only' at higher altitude; say 15000 feet.

The claim was not about engines, but about airframes,

"I came across the point that the
Me 109F may have been an extra-ordinarily efficient aircraft "

To do this, the HP rating of the Spitfire IX was used and the one
chosen was wrong. This was compared to the HP rating of the
Bf109, which again was apparently wrong. Not surprisingly the
Spitfire was given a more powerful engine and it appears the
Bf109 a lower rated engine than those actually used.

Indeed the wrong hp rating of the Me 109F was used as well as the wrong
hp rating of the spifire as was pointed out in the thread I gave
reference to. All things being equal?. The Mk IX two stage engine is
simply superior at all altitudes with the gap windening as the altitude
incrases. The rated powers were given at rated altitudes which is
higher for the Mk IX (whaever variant), however this benefits the
Spitfire in terms of a speed vs power figure of merit as both the two
stage and single stage Merlin 66 or 70 is superior in the altitudes
under consideration.

Incidenly mass efficiency of an aircraft is itself is meritorious: one
advantage of the Me 109’s thicker wings was that they could provide
higher coefficients of lift, thicker more efficient spars etc., lower
weight. The disadvantages were higher compressabillity effects. The
higher weight was compensated to a large degree by superior fuels and
the Merlin.




I used the rated power of the engines, not the sea level ones.

Apparently we now have the wonderful claim this is now a Bayesian
 argument, not binary.

Indeed it is baysian; we need the power and speed charts for various
boost limits, dymanic pressures etc.


Note by the way we are now avoiding the Bf109 airframe and heading
towards the engine fitted. Nor is the difference in weights being
mentioned.

Power curves for supercharges show a decline with increasing altitude
and discontinuities as gear changes momentarily provide a slight boost
followed by a generaly more agressive decline. Another decline starts
occuring at full pressure altitude, which is the altitude at which the
supercharger can no longer maintain the maximum pressure the engine can
opperate at. In the case of the Daimer Benz engine a two speed gear
driven supercharger is also used as in the Melins but a continiously
variable hydraulic final drive is used to regulate precise pressure to
the manfold. Most other engines throttled and blew of the excess
pressure which is generally less efficient.

So now we have the what different superchargers did paragraph.

I’m establishing how supercharger performance effects engine power
with altitude.



If the Me 109F4 demonstrated 420mph at 16000ft (where GM-1 is not used)
it is remarkable because it did so in thick dense atmosphere. It is
also completely sensible and a correction to history.

Except this figure contradicts things like the reported Bf109F
performance figures. It also means the Bf109G, with more power,
before the big bulges, lost performance, that is the G-1 and G-2
were slower than the F, despite an official 10% increase in power.

Early 109G2 were restricted to 1.3 atm vs 1.43 atm for the late 109F-4
so had only 3% more power albeit in a heavier airframe.


It means by mid 1943 the standard Bf109 was around 15% slower
than the F-4 of 1941.

The so called 386 mph as speed for and early Me 109G-6 has been in
dispute for a long time it represents the lowest end of the aircrafts
performance by far. 400mph is a closer figure and it is being
maintained at higher altitudes, with heavier armour and armament.

1943 the boost is released from 1.3 to 1.42atm.


Oh yes, the evidence supporting the above claim gives the best
speed altitude at around 21,000 feet.

No deployed
Merlin Spitfire could do this whether single stage or two stage. No
Spifire V at all and the Spitfire IX only by using its two stage
supercharger to allow it to opperate in to less dense higher
atmosphere.

Note by the way the basic problem with the above text, we have the
praise of the engine. Then all of a sudden it is the Bf109 airframe,
not the engine. Not what a Spitfire could do if fitted with the same
engine, which would be a better comparison of airframe efficiency.

You are hopelessly dishonestly rhetorical.


No, in order to tell us how wonderful the Bf109F airframe was we are
told all about the engine fitted.

So presumably the claim will mutate to the type had a more efficient
engine, at least low down.

Not at all. The 30L DB601E was fine engine but running 92/110 C3 fuel
it could not compete with the 27L Merlin 45 running 100/130 at any
altitude

It’s easy to understand incidently the PN number of 100/130 means
that 30% more power can be produced in the variable compression test
engine used to establish octane ratings and Performance numbers.

MW50 could add about 12%.


The usual ratings for the Bf109F-3 and F-4 engines is 1,300 or
1,350 HP delivering a top speed of around 390 to 400 mph at around
21,000 feet. The F-4/Z had GM-1. The F-4 empty and maximum weights
really vary between references, 4,330 to 6,220 pounds (Nowarra), 5,270
to 6,900 pounds (Green), 4,300 to 6,050 (Smith and Kay, quoting the F-3),
2,225 kg (4,900 pounds) to 2,980 kg (6,550 pounds) (Nowarra in a
different
book), 4,320 to 6,060 pounds (Smith, quoting the F-3) 2,086 kg (4,600
pounds) to 2,870 kg (6,300 pounds) (Radinger and Otto), the upper weight
being called class H5, and there was a load class H4, at 3,123 kg or
6,900
pounds for an extended range.

The rating of the DB601E at 2700rpm and 1.42 atmosheres boost is 1470hp
presumably on C3 fuel. The engine seems to have entered service at
around 1350 ps and 1.3 atm. Note a German DIN ps is slightly different
to an Imperial horsepower. The engine seems to have entered service at
1.3 atm but was uprated to 1.42 atm apparently due to improved spark
plugs and possibly a reformulation of C3 fuel.

The USN rates the German C-3 grade as roughly comparable
to the US 100/130 Performance Number grade, the standard
allied fuel for most of the war.

The late war 1944 grade is about 95/125 not 100/130 as you so
incorrectly insist upon. Early war grade was 92/110.

As Daimler Benz was playing with 2.2/2.3 atm boost. Levels of 2.4
atmosheres boost demands increases or at least conistency in fuel
standards to truly match 96/130 is conceivable. That suggest a DB605
producing 2400hp.



So now by the way we have the new rating of the Bf109F-4
engine, it has gone from 1,350 to 1,470 HP, that is effectively
the same as the Merlin 70 fitted to the Spitfire HF mark IX.

The DB601E had a 30L displacement. It was cleared for an increase of
boost from 1.3 to 1.42 atmospheres while RPM increased from 2500RPM to
2700RPM on 92/110 C3 fuel. The DB605 managed the same power initialy
at lower boost pressures of 1.3atm but it did so on ordinary B4 fuel,
it maintained power to higher altitudes. At this time German C3 fuel
seems to have had a mean rating of only 92/110.

The ratings of the engine as were probably obtained by an altitude test
chamber are as follows:
At sea level 1350ps; power then increases till
at 2200m the output climbed to around 1450ps, at this point a near
linear decline in output occurs untill at 4800m the power dropped to
around 1330ps.

At the 109F-4’s maximum speed of 670km/h which corresponds to 415mph
the engine would be producing 1120ps. Now look at the figures on
http://www.beim-zeugmeister.de/zeugmeister/index.php?id=30&L=1

The above are the ratings that would be obtained in an altitude
chamber: however due to the speed of the aircraft the intake scoop has
a dynamic pressure (staudruck) that alters the effective altitude and
that adds considerably to power except at small range of certain speeds
at certain altitudes where it reduces it,presumably by adding so much
pressure that the supercharger transitions are altered to inefficient
points.


So the wonder efficient Bf109 airframe, at 20% less weight than
the Spitfire, now has an engine with the same basic HP rating
but a different supercharger set up, and around the same top
speed, but at a significantly lower altitude.

1 It’s easier to make an aircraft go fast at high altitude given the
same power.
2 Comparison with spitfire should be at the same altitude with known
power curves.
3 Dynamic pressure effects on shaft output should be either included or
ignored equaly.
4 The fastest Spitfire V clearly was a much slower aircraft than the
slowest tested Me 109F by 15mph.

5 The Spitfire V has a significantly more powerfull engine at its rated
altitude than the early DB601E engines running at 1.3atm and a still
greater power than when the DB601 runs at 1.42.
6 The Spitfire IX has a significantly more powerfull engine at higher
altitudes due to its two stage intercooled supercharger.
7 Merlin 45 - 1,470 hp (1,100 kW) at 3,000 rpm at 9,250 ft (2,820 m);
used in Spitfire Mk.V
8 Other sources credit the Merlin 45 engine 1,515 hp (1130 kW) at
11,000 feet (3353 metres).
9 DB601E 1,450 ps (1430hp) at 2700 rpm at 2200m used in Me 109F-4
on C3 fuel at 1.42atm.
The above fuel would have been 92/110 C3 not the later 95/125 C3 fuel.
According to charts it is producing 1310ps/1290hp at 4800m.
10 Merlin 61 - fitted with a new two-speed two-stage supercharger
providing 1,565 hp (1,170 kW) at 3,000 rpm at 12,250 ft (3,740 m), and
1,390 hp (1,035 kW) at 3,000 rpm 23,500 ft (7,170 m); high-altitude
version used in Spitfire Mk.VII, Mk.VIII, Mk.IX, and PR.Mk.XI. The

It’s impossible to escape that the Me 109F airframe delivers
considerably more speed with less power. Than either the Spitfire Mk V.
The same can be said of the Me 109F-4 and the Mk IX though in this
case the speeds are more or less matched at 20,000ft.

The directly comparable Mk V with similar power ratings delivers at
most 374mph while the Me 109F delivers a best speed of 416 of at
1.42atm and a worst case of 390 at 1.3atm.


Yes folks, the BF109 is a very efficient airframe, just alter the
power outputs of its engine, its "rival's" engine, and then
spend lots of time telling us how good the engine is.

So ‘folks’ the tactic is to take the weight and performance of the
Heavy and later Spifire Mk IX and mention that it is 20% heavier than
the 109F, then that it has the same ‘rated’ power as the Me 109F
while ignoring the fact that the Mk IX has a two stage intercooled 60
series supercharger that maintains this engines power at altitude far
better then either the single stage of the Merlin 45 or 46 of Mk V
Spitfire or the Me 109’s . DB601E. Yes folks and then its faster
while picking and conflating suitable data this from the the Mk V and
Mk IX.


It also begs the question why did the G series go to the DB605
when it would be putting out less power than the engine it is
supposed to be replacing.

Unfortunatly all of the sources both the German and Other ones (Kay
must be fluent in German and takes his sources from the German ones)
are the old typical sources that suggest Me 109F performance lies
between 390 and 400mph.

Note by the way the same performance reports came from the allies
testing captured aircraft.

No they don’t.

The Reichlin test reports indicate at least 670km/h. Reichlin was the
Luftwaffes test center: they had no interest in exaggerating
performance of aircraft.

Note the two performance test from Messerschmitt.
http://www.beim-zeugmeister.de/zeugmeister/index.php?id=28&L=1

On the left photocopy/photograph, in the top box under the heading
“Allgemeign” which is the german were for “all in common” or
“general”. The left box, 3rd line down, list the maximum speed of
the Me 109F-4 as “Vmax at 635km/h at 6000m H” The line above
shows a Nominal power of 1185ps at Vmax. Which is 394mph.

Now look at the corresponding box in the right form is for the engine
producing the higher takeoff and emergency power as opposed to climb
and combat power.

The speed is now listed as “Vmax at 670km/h at 6300m” the power at
Vmax is listed as nominal


Oh yes, the allies captured a number of Bf109F-4's including come
that were intact.

And seemingly they had to remove and replace damaged engines from
earlier aricraft in what were beaten up airframes.


Unfortunatly German test center and factory test documentation is often
missing or muddled or isolated due to the german military collapse,
lack of resources for thorough performance testing and the shear
complexity of keeping track of performance changes. Only now is the
power of the internet being used to resolve some of these issues by
dissemination of often isolated and sparse information.. Modifications
that could come within weeks of one another or even cccur in the field
such as when new spark plugs become avaialble or reformulations of the
main German fuels B4 and C3 were made. The DB601E of the Me 109F4
could come with 1.3 or 1.42 atm boost, it could have modified spark
plugs and the Me 109F4/Z had the GM-1 system. Throw in furphies from
Allied tests of captured examples that are misrepresented as exemplary
but with incorrect tunning and maintenance procedures and the task
becomes even more complicated.

Except the reports are all quite consistent, 390 to 400 mph for the F-4,
something over 400 mph for the early G models then a decline with the
G-6 for obvious reasons. With speed being restored in the G-10.

You yourself note that the DB601 was rated at 1350 or 1300hp. The
difference may simply be that a German DIN ps is different to an
imperial hp, it may be due to different stages of evolution.

The different types of Horsepower,

Mechanical, boiler, electric, metric (DIN PS in German) and water.

The metric horsepower is 75 kg-metres per second. Or 0.986320 of
a mechanical horsepower which is defined as 550 foot-pounds per
second.

So 1350 HP metric would be 1,330 HP imperial.

This is before we discuss the US definition of length is different to
the English one, so an English foot is 30.48 cm, a US foot is 30.480061
cm.

This is before the fact different countries had different systems for
rating engine power output.

In fact the DB601E of the 109F could produce 1475hp on C3 fuel when its
permisable boost was raised from 1.3 to 1.42 atm when the appropriate
 > issues became resolved.
I retract the above figure of 1475hp and replace it with 1450ps (about
1430hp) incidently.


So why, when comparing the Bf109 to the Spitfire was the lower rated
HP used for the Bf109 and a much higher than actually fitted HP rating
used for the Spitfire?

It seems the sea level static rated emergency and takeoff power with
1.42atm was used this is 1350 but rises to 1450ps/1430hp at 2200m and
drops to 1330ps/1300hp at what must be full pressre altitude when the
final gear kicks in at 4800m and a rapid decline in power starts.







Things like the optional bomb racks and underwing armament seem to
be complicating the reported weights.

The 416 mph speed, if correct, would appear to be a GM-1 run.

I refer you to this gentlemens pages. He has reproduced the original
curves and reports:
http://www.beim-zeugmeister.de/zeugmeister/index.php?id=13&L=1

The author notes the Bf109G and FW190 with the BMW801D are
calculations. And the Bf109G calculation assumes a top speed of
740 km/hr or 460 mph.

So this lays out the chance the F-4 are calculations rather than
test runs, as a way of comparing the proposed changes.

In October 1941 Rechlin ran trials on a number of Bf109F-4s
and Fw190A-1s. Apart from showing the F-4 was generally
better it also noted there was an exceptional F-4, along with
an exceptional A-1.

An exceptional Mosquito managed 437 mph under test, when
the production versions were rated around 420 mph.

The claim is by the way

"If the Me 109F4 demonstrated 420mph at 16000ft"

If you look at the graph in the reference given the peak performance
claimed is 670 km/hr at around 6,400 metres or 420 mph at 21,000 feet.

Several things argue against this being an GM-1 run.

1 The power curves do not include the notion "Mit GM-1", not a thorough
argument but I've seen this notation used in Reiclin reports.

2 GM-1 can not be engaged below full pressure altitude. This appears
to be to low for that.

And at 21,000 feet?

3 The test weights indicate that the aircraft was not carrying nitrous
oxide

4 The aircraft is no described as being an Me 109F-4/Z with the Z
indicating GM-1.

5 Without GM-1 the 109F4 could maintain at about 416mph at 6250m
(21,000 feet) with GM-1 the 109F4/Z seems to have been able to do the
same at 8000m.

The above assumes the graph is correct and not an entire set of test
calculations based on different configurations.

Meantime

Page 9 gives Luftwaffe figures of 670 km/hr at 6,200 metres for the
F-4 and 700 km/hr at 7,000 metres for the G-1. This is interesting
given the G-10 is normally credited with being the fastest of the
G series, but it would be around 15 km/hr slower than the G-1,
which would, if the figures are correct, have a top speed in the
order of 440 mph or comparable to the K series top speed. By the
way the Fw190A-3 is credited with 700 km/hr at around 5,900 metres
"projektwerte".

Page 10 notes Messerschmitt performance figures were
around 660 km/hr at 6,200 metres as of November 1941, using
1,180 PS.

Page 11 notes Messerschmitt performance figures were
around 635 km/hr at 6,200 metres as of July 1942 using 1,185 PS

Page 12 has two figures, 635 km/hr at 6,000 metres at 1,195 PS and
the second 670 km/hr at 6,300 metres using 1,290 PS. Both are
Messerschmitt documents and both are dated February 1943.
The lower figure is "arguably calculated", which raises the
question why not the upper figure? After all aircraft
manufacturers are more likely to over claim than under claim.

The climb rates do not change despite the various top speed
 differences.

If sonder noteleistung was only available for 3/5 minutes it probably
wasn’t used.


Another figure from the Luftwaffe for the F-4, with the engine
able to develop 1,350 HP at 2,700 RPM is said to be 606 km/hr
which the book in question equates to 410 mph, which would
be around 660 km/hr., implying a typo in the metric figure.

Page 13 suggests adding "impact pressure" to the engine
performance graphs being displayed in order to obtain the
high speeds being claimed. The site wants to add 700 to 800
kg per square centimetre., where 1 atmosphere is 1.03323 kg per
square centimetre or 14.696 pounds per square inch, or 29.9213
 inches of mercury at 32 degrees F.

Staudruck translates to stagnation pressure but the concept in english
is dynamic pressure.


The performance chart gives a range of power at 6 km, between
1,050 and 1,200 PS. The interesting thing is the highest boost
 settings do not deliver the most power at 21,000 feet.


Overall the documents presented are quite consistent about
climb rates, but vary between 635 and 670 km/hr as the top
 speed, all at about the same altitude it seems.

6000 vs 6300; that’s a 1000ft and probably 3% less pressure.


Which rather leaves a problem, that could be resolved by the
boosting, or by some real build quality issues.

It also means if the F-4 and G-1 were that good the G-6 series
was a significant step backwards, with a top speed below
390 mph.

So overall the claims about 670 km/hr do not fit, at least as
 far as the standard F-4 in Luftwaffe use.

It fits if improvements in engine tuning, fuels and spark plugs allow
an latter in servive release of the higher boost pressure: the Daimler
Benz figures of 1350ps (sea level) are well noted while the speeds
changes are not generally known. The Germans are not going to
directly provide published data of Me 109F-4 performance.


So with
this it equalled the top speed of the HF Spitfire IX using around 91% of
the power, in an airframe that weighed in at less than 90% that of the
Spitfire.

Yet the airframe was still more 'efficient' in terms of speed for the
engine power.

The simple answer is no, but then again what was that about Bayesian
further up, during the great supercharger spiel?

As a comparison to GM-1 when the RAF installed a liquid oxygen
supply in a Spitfire VII it recorded a speed improvement of up to 30 mph
above 30,000 feet.

Interesting but the point is what?

Simple really, carrying additional oxygen and using it says nothing
about the efficiency of the airframe.

(snip)

By the way the various Spitfire V variants had engines rated between
1,415 and 1,585 HP, achieving top speeds between 357 mph at 6,000
feet with the 1,585 HP engines and 374 mph at 19,500 feet with a 1,415
HP engine. Supercharging options really need to be considered before
talking about efficiency, you really need to fit the airframes being
compared
with the same engine, but even that has problems given what engines the
airframes were designed to use.

The argument, as I see it, is whether the Me 109F airframe is more
efficient for a given power than that of the Spifire. It clearly is;
the spitfire, especialy two stages versions, had a better powerplant
with better fuel which compensated for the aircrafts bigger airframe
and wing area/lower wing loading.

So where are the comparisons with both machines fitted with the
same engine?

Put it this way. The early Marks of Spitfire (I,II,III) were more or
less equally matched with the 109E series in power, speed and climb.

The published figures indicate the Spitfire I had around a 10 to 15 mph
top speed advantage over the Bf109E-4. By the way 10 to 15 mph is
considered significant when the Bf109 is the faster, but similar when
the Spitfire is the faster.

The mark II spitfire had an engine around 20% more powerful pulling
a 10% heavier airframe. The result was an official top speed of around
370 mph, on a 1,240 HP engine. This was around 8 mph faster than the
official figures for the mark I.

The Bf109s would not have liked to meet the Spitfire mark III, with
its 400 mph top speed. The version was cancelled in preference to
the mark V, less production disruption.

When the Mk V entered service it had an considerably more powerfull
single stage Merlin. Its contemporary, the Me 109F, also had an
improved engine however while the Mk V or IX for that matter introduced
no major aerodynamic improvements the Me 109F dramatically cleaned up
the nose and greatly improved the radiators and changed the outer wing
planform and profile.

You see the point here is to compare the mark V with the Bf109F.

Becuase they are a closer match.



Now it is generally agreed the Bf109F was the best, aerodynamically,
of the Bf109 series, it cleaned up the Bf109 airframe and managed a
more powerful engine on about the same or better loaded weight
than the E series.

Meantime the mark V suffered the weight gains, nearly 20% more
than the mark I and as a result had the same top speed as the mark II
despite the more powerful engine ratings.

The Merlin 60 series Spitfires managed a better than 10% increase
in top speed over the mark Vs on something around a 5% increase
in rated engine power. The best increase is the HF mark IX, around
a 13% increase in top speed on no increase in engine rating.

Of course supercharging arrangements matter.

So if you want to make the Bf109 look good, pick its best, in terms
of HP per mph, the F-4, and compare it to the Spitfire V, which was
the worst of the Spitfire versions for such a figure. Simple really.

The simple reality is not matter how you twist and turn the slowest Me
109F-4 goes significantly faster with less power than any Mk V spitfire
and it does it on less power.



Spitfire power efficiency was in general unremarkable; it did have a
good light engine with good quality fuel.

Except as noted the mark I was faster than the Bf109E, with a
lower rated engine, the mark II could match the earlier Bf109F-1
and -2 using an similarly rated engine.

And the mark VII, VIII, IX, XVI series could also match the
Bf109F and certainly the G models, using similarly rated engines.

After all look at the weight differences.

Note David Ledicners comment:
http://yarchive.net/air/spitfire.html

Basically he thinks things, but has not done the calculations, and the
comparison is with the Mustang.

He’s an expert in computational flow dynamics and has performed a
landmark comparison of the P51C and D with the Spitfire IX, Fw 190A and
D using computational flow dynamics. Of coruse after attempting to
discredit the man without you confirm his statements in your tangent
about the P-51 below.


Meantime the RAF found as follows, the Mustang I (P-51A) drag
figure was 50 pounds per 100 feet per second, whereas the average
Spitfire figure was 65.5 pounds per 100 feet per second, as of mid
1942.

Using the V-1710 F3R, peak output 1,150 HP at 3,000 RPM at 12,000
feet, the Mustang I top speed was 370 mph at 15,000 feet.

Fitted with the V-1710 F21R, with reduced supercharger gearing the
top speed went to 377.5 mph at 4,000 feet.

The Mustang II, with the F20R engine fitted managed 409 mph at
10,000 feet.

The US rating for the Mustang engine was 1,200 HP for take off
and 1,330 HP military power. The empty weight of the early
Mustangs was around the maximum loaded weight of the Bf109F-4.

The P-51 was a very efficient airframe.

I don't deny it.



Since the P-51B, C and D were fitted with basically the same engines
as the Merlin 60 series Spitfires you can see this from the way the
P-51 had around a 30 mph increase in top speed.

A similar comparison can be made between the Spitfire I and the
Hurricane I.

Meantime the comparison of airframes between the Bf109 and
Spitfire requires both be fitted with the same engine. Assuming
there are not problems in doing so.

Many of the Me 109F's advantages in lightness were surrendered when the
changeover to the Me 109G in order to allow heavier armament and armour
to be carried while often using lower grade B4 fuel that must have been
neccesary to attack the bomber streams. Very few two stage
superchargers were used by the Germans in part because of manufacturing
issues and in part becuase they were able to improve single stage
superchargers fluid dymanics.

The G-6 gained around 10% in weight terms over the F-4.

The K-4 was around 15% heavier than the F-4.

The big problem for the G series was the bulges, to carry heavier
armament and the landing gear needed to support the weight.

Simply put it seems Messerschmitt designed the lightest undercarriage
it could when the Bf109 was first built and had to pay for it later when
the weight increases required strengthening.

They designed an undercarriage for a 1935 era aircraft that ran on 20L
700hp engines. The 109 was a predecesor not only the Spitfire but the
Hurricane as well.


So the G-6 was slower than the late F and early G series. The clean up
in the K model and a more powerful engine created the fastest of the
Bf109s, around 10 to 15 mph faster than the P-51 using around 20%
more power.

Had the Me 109F been directed only at other fighters developed two
stage non intercooled versions of the smaller DB601 engine should have
been adaquete.

Yet again something the Germans never did is given as the answer.

They developed the DB605L and engine only 15kg heavier than the DB605
it maintained 1300hp to 9700m. The reality is however that without
increased supplies not only of cs fuel but the uprated 96/125
increasing swept volume was the only way to go. Provide 96/125 or
100/130 high octane fuel to a developed DB601E its power increases by
20%.


Geoffrey Sinclair
Remove the nb for email.

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