Junkers Jumo 004 is often remembered as a temperamental
and failure-prone powerplant. Despite its advanced design,
engine life was only between 10 and 25 hours, with the mean
being at the lower end of this range. These failures
were anticipated to some extent and the Me 262 was designed
to permit extremely rapid engine changes.
Contrary to popular belief, the 004A was a
fairly sound performer when premium steels were used, and
early versions were known to achieve a 200-250 hour service
life. However, the diversion of critical materials into
U-boat production and other projects late in the war forced
Junkers to produce the 004B model with only 1/3 of
the high grade steel that had been used in the 004A.
It was to be a disastrous concession for the Me 262.
The introduction of inferior metals compounded
an already problematic situation with the turbine blade design.
These blades were rigidly mounted, contributing to severe
root stress relief problems. The weaker metals simply
could not withstand this kind of abuse and regular compressor
failures were an inevitable consequence.
The General Electric J-85/CJ-610 series turbojet engine is
a benchmark in the advancement of pure jet technology.
The engine was originally designed in the
1960s for use in military applications. Shortly thereafter,
civil certification and production followed under the CJ-610
The CJ-610 was quickly selected to
power the popular Gates Learjet; meanwhile, its military
cousin was called into service with such noteworthy combat
aircraft as the F-5 Freedom Fighter and A-37 Dragonfly.
The resilience and forgiving qualities of
the engine also made it a natural choice for training aircraft,
and the J-85 was adopted for both the T-38 Talon
and T-2J Buckeye.
The J-85/CJ-610 engine has a reputation for
extreme reliability, allowing wide variations of inflow distortion.
It also places a minimal maintenance burden upon ground crews.
Proven in war and in peace over three decades, the engine
is ideally suited to power this classic warbird well into
the next century.
aircraft applications, engine power is characteristically
measured in terms of thrust versus weight. The Jumo
004 was typical of early jet engines in that it was rather
heavy, and not especially efficient.
Production model 004s produced 1,980 lbs.
of thrust, and weighed in at about 1,800 lbs. Because
of this, the engines were not extraordinarily effective at
low airspeeds or altitudes or at reduced power settings.
Long takeoff rolls (>3,000') were evidence
of this phenomenon and, once aloft, power management became
critical. Abrupt throttle changes or rapid maneuvering
often resulted in a flameout, or worse, a complete compressor
Each J-85 produces 2,850 lbs. of thrust, yet weighs only 395
lbs. In simpler terms, the new engines offer nearly
twice the power for less a quarter of the Jumo's
The design dynamics of the Jumo engine
castings are expected to reduce the thrust available by about
300 lbs. per engine. Our current engineering estimates
call for an actual power output in the vicinity of 2400-2500
lbs. per engine.
Integration of the J-85 will bring many noticeable
improvements. Takeoff distances will be significantly
shortened (<2,000'), and time-to-climb rates vastly improved.
Also, the J-85 responds well to varying power demands (including
low power settings) and is highly tolerant of the kind of
airflow disruptions that gave the Jumo such
The Jumo-powered Me 262
was capable of level flight speeds in excess of 540 miles
per hour at altitude; a trait that made it all but invulnerable
to Allied escort fighters.
Higher airspeeds were recorded
under certain circumstances but, in general, compressibility-related
aerodynamic factors prevented the airframe from ever pushing
into the high transonic range.
Postwar tests in the West confirmed
that at very high airspeeds airframe vibration levels and
buffeting grow increasingly worse until the jet enters into
a shallow dive and becomes all but completely uncontrollable.
Recently revealed Soviet documents demonstrate that this was
also a major finding in Red Air Force flight testing of the
In purely theoretical terms, the added power of the J-85 should
give the new production Me 262s a speed advantage of at least
75 miles per hour over any previous generation Me 262.
The fact remains that the airframe was never
designed to handle the stress loads encountered at speeds
in the 600 mile per hour range. To push the aircraft
into this environment simply because additional power "happens
to be available" is a highly dangerous and ill-advised
In the interest of safety, the Me 262 Project
will be placing a placarded airspeed limitation upon the jets
in the vicinity of 500 MPH. The official position of
the project is that there is simply no need -- or benefit
-- in flying these aircraft any faster.
Fuel Consumption (SFC) values provide a quantifiable and uniform
means of measuring a turbojet engine's efficiency. All
jets have an associated SFC, and for the Jumo 004,
the correct figure is 1.39.
In practical terms, this means that for each
pound of thrust provided, the Jumo will
burn 1.39 pounds of fuel per pound of thrust per hour.
With a typical fuel capacity of 1,800 liters, the range of
the original Me 262 was approximately 600-650 miles (at altitude).
J-85 has a Specific Fuel Consumption value of .99, meaning
that it will burn slightly less than one pound of fuel per
pound of thrust per hour. When compared to the Jumo,
the J-85 is obviously some 40% more efficient.
This improvement will have a marked impact
upon both the range and endurance of the of the new Me 262s.
A new Me 262 should be able to travel well over 1,000 miles
on a single fuel load.