Re: Me 262 Mythology
- From: Archaeopteryx <archaeopt@xxxxxxxxx>
- Date: Thu, 19 Feb 2009 08:09:05 -0800 (PST)
On Feb 19, 7:34 am, Eunometic <eunome...@xxxxxxxxxxxx> wrote:
On Feb 19, 10:59 am, "Scott M. Kozel" <koze...@xxxxxxxxxxx> wrote:
The idea of the Me 262 as the potentially decisive wonder weapon is
one of the most enduring myths in airpower history. Hitler’s oft-
quoted order forbidding the employment of this aircraft as a fighter
dates from May 1944, by which time no Me 262s were in service. Because
design and technical faults still plagued the aircraft,
1 There were no significant design or technical faults with the
airframe: unless you count nose wheel collapses which can be traced to
a steel quality problems.
2 Certainly it is a myth that Adolf Hitlers demands that the A/C be
developed exclusively as a fighter bomber significantly delayed the
aircraft. In some circumstances this would have delayed the aircraft
however the engines were they real source of the delay so there was
time for airframe work required to adapt it to carry bombs. Hitlers
decision was very correct: the aircraft was supposed to be able to
help destroy the expected allied invasion fleet.
Technically the problem of aiming the bomb accuratly while stopping
the bomb from 'slipstreaming' required the TSA 2D toss bombing sight
3 There was a period, I think 1940 when the program was on a shoe
string budget as part of a general order to stop any weapons that
couldn;t be deployed within 6 months that may have been disruptive.
its employment
in any role would have to await their resolution—as would the training
of a sufficient number of pilots, many of whom found it difficult to
master the temperamental interceptor.
4 The aircraft, in terms of airframe, had good handling and wasn't
temperamental. Single engine flight was good so long as you stayed
above a certain minimum speed (200 knots I think but might be
higher). I assume a single engine approach would require a line up
followed by a final low power glide with the engine idling.
It is unlikely that the jet
could have appeared in combat much earlier than it did, even without
Hitler’s interference. The 262, although a deadly aircraft in the
hands of the right pilot, remained essentially a prototype pressed
into combat service.
I think the airframe was fine, immature engines were the problem and
that problem can be traced to shortages of nickel and chromium.
An alloy like Tinadur was 30% Nickel, 12% Chromium and 6% Titanium
with balance Iron. It's nickel content was later reduced and finally
it was replaced by another Krupp alloy which replaced the nickel with
manganese. In the meantime allied engines could use nimonic which was
80% nickel and 20% chromium. Such levels of alloy were inconceivable
to the Germans who worked to reduce the amount rather than just
focusing on performance.
The one conceptual flaw that could be attributed to the Me 262 was the
lack of speed brakes to slow the aircraft down in order to take aim
nevertheless the tactical solution worked fine: a high speed tail
approach from below followed by a pull-up to wash of speed and line up
the target. Developments in fire control, sighting (EZ42 and EZ45
lead computing gyro sight later to be linked to radar ranging and
weapons such as the R4M folding fin rocket and E 100BS missile were in
any case about the make the idea of slowing down to fire a weapon not
only unnecessary but insane as it seems.
Throughout its short service life, the aircraft
suffered from an abnormally high accident rate and scored only a
minuscule number of combat victories.
By miniscule you mean between 500-700 aircraft in a few months.
That is 30-40 squadrons of B17/B24 with 5000-7000 aircrew though a
significant number of P-51s fell to the Me 262. The Me 262 could not
turn inside a P-51 but it could turn at a faster rate, running around
the outside of the P-51. Even counting 25% over claims, which I doubt
in this case, the victories are substantial. Pick 75% of the lower
number of aircraft to account for any over claiming, which I don't
think is the case the allied losses are still significant.
The main, it can be argued the only, problem preventing significantly
earlier entry into service was the supply of reliable quality engines
with a second factor being skilled labour shortages that led to
problems getting anywhere near the quality levels the pre
preproduction Jumo 004B-0 and prototype Jumo 004A engines could
reach. Anthony Kay in "German Jet Engine Gas Turbine Developement"
notes the significantly better life of the high alloy content
prototype turbines. The turbine blades incidently were not much a
problem: the inlet guide nozzles were more problematical. It was
thoought these would be convered to ceramics sometime in 1946.
The dominant factor in preventing quality engines was the inadequate
supply of nickel and to a lesser extent chromium; design issues were
definitely there such as poor fuel control (leading to overheats and
flameouts) but its hard to blame the engines lack of refinement since
the overheats due to fuel overdosing could have been tollerated with
better alloys. A vast engineering effort went into reducing the
nickel requirements of the engine down to about 6.0kg/unit. On its
own this distracted much talent away from the basics. The pioneer in
jet engines in Germany and effectively the world was Heinkel and one
reason they failed to get orders was that they were not as far down
the path of reducing nickel consumption as the other manufacturers.
A case in point is the combustion chamber cans. There were six of
these arranged as a ring around the shaft, they were initially made of
a heat and corrosion resistant high nickel and chromium content
austenitic alloys (basically a fancy stainless steel). In order to
reduce demand for these metals the cans were made out of ordinary
carbon steel with an aluminium oxide coating (effectively ceramics).
Thus these can needed to be replaced at least every 25 hours. In fact
the cans often burned through. Even eliminating the nickel but
retaining the chromium would have improved this enormously. Another
case in point is the translating exhaust cone which was also of
ordinary steel and distorted under heat and stress to block the
engine.
Circumstance that would have gotten the Me 262 into service earlier
include.
1 Insulating the engine development program from reduction in the 1940
period.
2 Allowing the two excellent engines that Heinkel had to be developed.
3 Allowing one manufacturer, perhaps Heinkel, to pursue a path of
using high alloy content engines as a stop gap.
Erhardt Milch claimed that it would be necessary to get the Me 262 in
service by 1943 or the war would be lost. I think he was right. In
fact getting the aircraft into service in early 1944 might have been
decisive in that it would have stopped dead the attacks on the German
oil industry, the harassment of the German army by allied air power
and it would have allowed a showing of German airpower over Normandy,
witness the impunity with which the Ar 234A prototypes, still with
their pre productione engines, reconoitered the allied bridgehead for
months without loss to allied aircraft or engine loss. (they were
eventually shot down by edgy German FLAK crews)
As it was German metallurgist made significant improvements that were
expected to produce turbine life of 500 hours in the lab and 150 hours
in the field for the Jumo 004 while BMW had developed new blades that
were expected to double service life to 50 hours for the BMW 003. It
was hoped ceramics would take over turbine nozzles in 1946.
The aircraft had the capacity to keep up with allied developments such
as advanced forms of the Meteor, P-80 and Vampire due to expected
engine improvements. The P-80 would turn out to develop into an
excellent aircraft but the decision to make it a single engined
aircraft would limit its performance.
....
1 There were no significant design or technical faults with the
airframe: unless you count nose wheel collapses which can be traced to
a steel quality problems.
As usual, the tin foil Picklehaubs come out of the veritable woodwork
when it comes to glorifying the spiffier toys of das Reich.
Rather than being the product of perfection that some claim it to be,
the Me-262 was cobbled together over a number of major design
revisions forced by technical issues dating back to its inception. A
detailed discussion of these myths regarding the development of the
262 design and how it stacked up against the P-80A and Meteor from the
March, 2005 issue of Airpower is available at:
http://goliath.ecnext.com/coms2/gi_0199-3842317/Me-262-Wunderplane-or-compromise.html
Me-262: Wunderplane or compromise? An inside look at the world's first
operational jet fighter and its rightful place in history.
[selected quotes:]
Swept wing myth:
Interestingly, although the Me 262 is usually portrayed as being the
forebear of many advanced concepts, it was actually very much a
compromise aircraft and its designers were not particularly happy with
several aspects of it. The "advanced" swept-wing was an inelegant
solution to a center-of-gravity problem, while the underslung nacelles
compensated for oversized and overweight powerplants. Its designers
were not supermen changing the world, but competent engineers
responding to events largely out of their control.
Me-262 vs. P-80A performance:
After the war, "Watson's Whizzers," led by Colonel Harold E. Watson
from USAAF Air Technical Intelligence, shipped several intact Me 262s
to the United States for further evaluation. The tests, conducted by
Albert Boyd (the head of flight test for the USAAF) and a soon-to-be-
legendary Chuck Yeager, determined that the performance of the Me 262
was essentially equal to the P-80A. The Me 262 had a slightly higher
critical Mach number-0.83 Mach versus the handbook limit of 0.80 Mach
for the P-80A--but the difference was of little value in the real
world since the Me 262 could only reach that velocity in a dive,
whereas the P-80A could do it in level flight. However, despite the
fact that the Me 262 was almost 2,000 pounds heavier than the P-80A,
the German aircraft accelerated quicker and had approximately the same
climb performance.
During the tests it was found that the slightly swept wing of the Me
262 provided no useful reduction in drag, mainly because the
triangular cross-section of the fuselage created so much base drag
that nothing could really help much. The swept wing did not change the
critical Mach number by a measurable amount, and certainly did not
help performance in the low transonic region where the Me 262 was
particularly unstable. The P-80A had much better handling
characteristics than the Me 262, largely because it was more refined
aerodynamically and had its thrust vector on the centerline of the
aircraft instead of at the quarter-span of each wing.
[end quotes]
And so on and so forth. The problem here isn't technical - the 262 was
an outstanding design for its time that was both innovative and
impressive - but when all the myths of its inherent superiority are
stripped away, its reputation actually suffers at the hands of those
that resort to wild speculations to claim the 262 was something it
actually wasn't.
.
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