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The Drake equation (also sometimes called the "Green Bank equation", the "Green Bank Formula," or often erroneously labeled the "Sagan equation") is a famous result in the speculative fields of exobiology and the search for extraterrestrial intelligence (SETI).
This equation was devised by Dr. Frank Drake (now Professor Emeritus of Astronomy and Astrophysics at the University of California, Santa Cruz) in 1960, in an attempt to estimate the number of extraterrestrial civilizations in our galaxy with which we might come in contact. The main purpose of the equation is to allow scientists to quantify the uncertainty of the factors which determine the number of such extraterrestrial civilizations.

History
Frank Drake formulated his equation in 1960 in preparation for the Green Bank meeting. This meeting, held at Green Bank, West Virginia, established SETI as a scientific discipline. The historic meeting, whose participants became known as the "Order of the Dolphin," brought together leading astronomers, physicists, biologists, social scientists, and industry leaders to discuss the possibility of detecting intelligent life among the stars.
The Green Bank meeting was also remarkable because it featured the first use of the famous formula that came to be known as the "Drake Equation". This explains why the equation is also known by its other names with the "Green Bank" designation. When Drake came up with this formula, he had no notion that it would become a staple of SETI theorists for decades to come. In fact, he thought of it as an organizational tool — a way to order the different issues to be discussed at the Green Bank conference, and bring them to bear on the central question of intelligent life in the universe. Carl Sagan, a great proponent of SETI, utilized and quoted the formula often and as a result the formula is often mislabeled as "The Sagan Equation". The Green Bank Meeting was commemorated by a plaque.
The Drake equation is closely related to the Fermi paradox in that Drake suggested that a large number of extraterrestrial civilizations would form, but that the lack of evidence of such civilizations (the Fermi paradox) suggests that technological civilizations tend to destroy themselves rather quickly. This theory often stimulates an interest in identifying and publicizing ways in which humanity could destroy itself, and then countered with hopes of avoiding such destruction and eventually becoming a space-faring species. A similar argument is The Great Filter,^[1] which notes that since there are no observed extraterrestrial civilizations, despite the vast number of stars, then some step in the process must be acting as a filter to reduce the final value. According to this view, either it is very hard for intelligent life to arise, or the lifetime of such civilizations must be depressingly short.
The grand question of the number of communicating civilizations in our galaxy could, in Drake's view, be reduced to seven smaller issues with his equation.

The equation

The Drake equation states that:

where:

N is the number of civilizations in our galaxy with which communication might be possible;

and

R^* is the average rate of star formation in our galaxy

f_p is the fraction of those stars that have planets

n_e is the average number of planets that can potentially support life per star that has planets

f_ℓ is the fraction of the above that actually go on to develop life at some point

f_i is the fraction of the above that actually go on to develop intelligent life

f_c is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L is the length of time such civilizations release detectable signals into space.

Alternative expression

The number of stars in the galaxy now, N^*, is related to the star formation rate R^* by

,

where T_g is the age of the galaxy. Assuming for simplicity that R^* is constant, then N^* = R^* T_g and the Drake equation can be rewritten into an alternate form phrased in terms of the more easily observable value, N^*.

R factor

One can question why the number of civilizations should be proportional to the star formation rate, though this makes technical sense. (The product of all the terms except L tells how many new communicating civilizations are born each year. Then you multiply by the lifetime to get the expected number. For example, if an average of 0.01 new civilizations are born each year, and they each last 500 years on the average, then on the average 5 will exist at any time.) The original Drake Equation can be extended to a more realistic model, where the equation uses not the number of stars that are forming now, but those that were forming several billion years ago. The alternate formulation, in terms of the number of stars in the galaxy, is easier to explain and understand, but implicitly assumes the star formation rate is constant over the life of the galaxy.

Expansions

Additional factors that have been described for the Drake equation include:

n_r or reappearance factor: The average number of times a new civilization reappears on the same planet where a previous civilization once has appeared and ended

f_m or METI factor: The fraction of communicative civilizations with clear and non-paranoid planetary consciousness (that is, those which actually engage in deliberate interstellar transmission)

With these factors in mind, the Drake equation states:

Reappearance factor

The equation may furthermore be multiplied by how many times an intelligent civilization may occur on planets where it has happened once. Even if an intelligent civilization reaches the end of its lifetime after, for example, 10.000 years, life may still prevail on the planet for billions of years, availing for the next civilization to evolve. Thus, several civilizations may come and go during the lifespan of one and the same planet. Thus, if n_r is the average number of times a new civilization reappears on the same planet where a previous civilization once has appeared and ended, then the total number of civilizations on such a planet would be (1+n_r), which is the actual factor added to the equation.
The factor depends on what generally is the cause of civilization extinction. If it is generally by temporary inhabitability, for example a nuclear winter, then n_r may be relatively high. On the other hand, if it is generally by permanent inhabitability, such as stellar evolution, then n_r may be almost zero.
In the case of total life extinction, a similar factor may be applicable for f_ℓ, that is, how many times life may appear on a planet where it has appeared once.

METI factor

Alexander Zaitsev said that to be in a communicative phase and emit dedicated messages are not the same. For example, we, although being in a communicative phase, are not a communicative civilization; we do not practice such activities as the purposeful and regular transmission of interstellar messages. For this reason, he suggested introducing the METI factor (Messaging to Extra-Terrestrial Intelligence) to the classical Drake Equation.

Historical estimates of the parameters

Considerable disagreement on the values of most of these parameters exists, but the values used by Drake and his colleagues in 1961 were:

• R* = 10/year (10 stars formed per year, on the average over the life of the galaxy)
• f_p = 0.5 (half of all stars formed will have planets)
• n_e = 2 (stars with planets will have 2 planets capable of supporting life)
• f_l = 1 (100% of these planets will develop life)
• f_i = 0.01 (1% of which will be intelligent life)
• f_c = 0.01 (1% of which will be able to communicate)
• L = 10,000 years (which will last 10,000 years)

Drake's values give N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10,000 = 10.
The value of R* is determined from considerable astronomical data, and is the least disputed term of the equation; f_p is less certain, but is still much firmer than the values following. Confidence in n_e was once higher, but the discovery of numerous gas giants in close orbit with their stars has introduced doubt that life-supporting planets commonly survive the creation of their stellar systems. In addition, most stars in our galaxy are red dwarfs, which flare violently, mostly in X-rays—a property not conducive to life as we know it (simulations also suggest that these bursts erode planetary atmospheres). The possibility of life on moons of gas giants (such as Jupiter's moon Europa, or Saturn's moon Titan) adds further uncertainty to this figure.
Geological evidence from the Earth suggests that f_l may be very high; life on Earth appears to have begun around the same time as favorable conditions arose, suggesting that abiogenesis may be relatively common once conditions are right. However, this evidence only looks at the Earth (a single model planet), and contains anthropic bias, as the planet of study was not chosen randomly, but by the living organisms that already inhabit it (ourselves). Whether this is actually a case of anthropic bias has been contested, however; it might rather merely be a limitation involving a critically small sample size, since it is argued that there is no bias involved in our asking these questions about life on Earth. Also countering this argument is that there is no evidence for abiogenesis occurring more than once on the Earth—that is, all terrestrial life stems from a common origin. If abiogenesis were more common it would be speculated to have occurred more than once on the Earth. In addition, from a classical hypothesis testing standpoint, there are zero degrees of freedom, permitting no valid estimates to be made.
One piece of data which would have major impact on f_l is the discovery of life on Mars or another planet or moon. If life were to be found on Mars which developed independently from life on Earth it would imply a higher value for f_l. While this would improve the degrees of freedom from zero to one, there would remain a great deal of uncertainty on any estimate due to the small sample size, and the chance they are not really independent.
Similar arguments of bias can be made regarding f_i and f_c by considering the Earth as a model: intelligence with the capacity of extraterrestrial communication occurs only in one species in the 4 billion year history of life on Earth. If generalized, this means only relatively old planets may have intelligent life capable of extraterrestrial communication. Again this model has a large anthropic bias and there are still zero degrees of freedom. Note that the capacity and willingness to participate in extraterrestrial communication has come relatively "quickly", with the Earth having only an estimated 100,000 year history of intelligent human life, and less than a century of technological ability.
f_i, f_c and L, like f_l, are guesses. Estimates of f_i have been affected by discoveries that the solar system's orbit is circular in the galaxy, at such a distance that it remains out of the spiral arms for hundreds of millions of years (evading radiation from novae). Also, Earth's large moon may aid the evolution of life by stabilizing the planet's axis of rotation. In addition, while it appears that life developed soon after the formation of Earth, the Cambrian explosion, in which a large variety of multicellular life forms came into being, occurred a considerable amount of time after the formation of Earth, which suggests the possibility that special conditions were necessary. Some scenarios such as the Snowball Earth or research into the extinction events have raised the possibility that life on Earth is relatively fragile. Again, the controversy over life on Mars is relevant since a discovery that life did form on Mars but ceased to exist would affect estimates of these terms.
The astronomer Carl Sagan speculated that all of the terms, except for the lifetime of a civilization, are relatively high and the determining factor in whether there are large or small numbers of civilizations in the universe is the civilization lifetime, or in other words, the ability of technological civilizations to avoid self-destruction. In Sagan's case, the Drake equation was a strong motivating factor for his interest in environmental issues and his efforts to warn against the dangers of nuclear warfare.
By plugging in apparently "plausible" values for each of the parameters above, the resultant expectant value of N is often (much) greater than 1. This has provided considerable motivation for the SETI movement. However, we have no evidence for extraterrestrial civilizations. This conflict is often called the Fermi paradox, after Enrico Fermi who first asked about our lack of observation of extraterrestrials, and motivates advocates of SETI to continually expand the volume of space in which another civilization could be observed.
Other assumptions give values of N that are (much) less than 1, but some observers believe this is still compatible with observations due to the anthropic principle: no matter how low the probability that any given galaxy will have intelligent life in it, the universe must have at least one intelligent species by definition otherwise the question would not arise.
Some computations of the Drake equation, given different assumptions:

R* = 10/year, f_p = 0.5, n_e = 2, f_l = 1, f_i = 0.01, f_c = 0.01, and L = 50,000 years

N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 50,000 = 50 (so 50 civilizations exist in our galaxy at any given time, on the average)

But a pessimist might equally well believe that life seldom becomes intelligent, and intelligent civilizations do not last very long:

R* = 10/year, f_p = 0.5, n_e = 2, f_l = 1, f_i = 0.001, f_c = 0.01, and L = 500 years

N = 10 × 0.5 × 2 × 1 × 0.001 × 0.01 × 500 = 0.05 (we are probably alone)

Alternatively, making some more optimistic assumptions, and assuming that 10% of civilizations become willing and able to communicate, and then spread through their local star systems for 100,000 years (a very short period in geologic time):

R* = 20/year, f_p = 0.1, n_e = 0.5, f_l = 1, f_i = 0.5, f_c = 0.1, and L = 100,000 years

N = 20 × 0.1 × 0.5 × 1 × 0.5 × 0.1 × 100,000 = 5,000

Current estimates of the parameters

This section attempts to list best current estimates for the parameters of the Drake equation.
R* = the rate of star creation in our galaxy

Estimated by Drake as 10/year. Latest calculations from NASA and the European Space Agency indicates that the current rate of star formation in our galaxy is about 7 per year.

f_p = the fraction of those stars which have planets

Estimated by Drake as 0.5. It is now known from modern planet searches that at least 30% of sunlike stars have planets, and the true proportion may be much higher, since only planets considerably larger than Earth can be detected with current technology. Infra-red surveys of dust discs around young stars imply that 20-60% of sun-like stars may form terrestrial planets.

n_e = the average number of planets (satellites may perhaps sometimes be just as good candidates) which can potentially support life per star that has planets

Estimated by Drake as 2. Marcy, et al. notes that most of the observed planets have very eccentric orbits, or orbit very close to the sun where the temperature is too high for earth-like life. However, several planetary systems that look more solar-system-like are known, such as HD 70642, HD 154345, or Gliese 849. These may well have smaller, as yet unseen, earth sized planets in their habitable zones. Also, the variety of solar systems that might have habitable zones is not just limited to solar-type stars and earth-sized planets - it is now believed that even tidally locked planets close to red dwarves might have habitable zones, and some of the large planets detected so far could potentially support life - in early 2008, two different research groups concluded that Gliese 581d may possibly be habitable.^{[7] [8]} Since about 200 planetary systems are known, this implies n_e > 0.005.

Even if planets are in the habitable zone, however, the number of planets with the right proportion of elements may be difficult to estimate. Also, the Rare Earth hypothesis, which posits that conditions for intelligent life are quite rare, has advanced a set of arguments based on the Drake equation that the number of planets or satellites that could support life is small, and quite possibly limited to Earth alone; in this case, the estimate of n_e would be infinitesimal.

f_l = the fraction of the above which actually go on to develop life

Estimated by Drake as 1.

In 2002, Charles H. Lineweaver and Tamara M. Davis (at the University of New South Wales and the Australian Centre for Astrobiology) estimated f_l as > 0.13 on planets that have existed for at least one billion years using a statistical argument based on the length of time life took to evolve on Earth. Lineweaver has also determined that about 10% of star systems in the Galaxy are hospitable to life, by having heavy elements, being far from supernovae and being stable themselves for sufficient time.

f_i = the fraction of the above which actually go on to develop intelligent life

Estimated by Drake as 0.01.

f_c = the fraction of the above which are willing and able to communicate

Estimated by Drake as 0.01.

L = the expected lifetime of such a civilization for the period that it can communicate across interstellar space

Estimated by Drake as 10,000 years.

In an article in Scientific American, Michael Shermer estimated L as 420 years, based on compiling the durations of sixty historical civilizations. Using twenty-eight civilizations more recent than the Roman Empire he calculates a figure of 304 years for "modern" civilizations. It could also be argued from Michael Shermer's results that the fall of most of these civilizations was followed by later civilizations which carried on the technologies, so it's doubtful that they are separate civilizations in the context of the Drake equation. Furthermore since none could communicate over interstellar space, the value of L here could also be argued to be zero.

The value of L can be estimated from the lifetime of our current civilization from the advent of radio astronomy in 1938 (dated from Grote Reber's parabolic dish radio telescope) to the current date. In 2008, this gives an L of 70 years. However such an assumption would be erroneous. 70 for the value of L would be an artificial minimum based on Earth's broadcasting history to date and would make unlikely the possibility of other civilizations existing. 10,000 for L is still the most popular estimate

Values based on the above estimates,

R* = 7/year, f_p = 0.5, n_e = 2, f_l = 0.33, f_i = 0.01, f_c = 0.01, and L = 10000 years

result in

N = 7 × 0.5 × 2 × 0.33 × 0.01 × 0.01 × 10000 = 2.31

Criticisms

Since there exists only one known example of a planet with life forms of any kind, several terms in the Drake equation are largely based on conjecture. However, based on Earth's experience, some scientists view intelligent life on other planets as possible and the replication of this event elsewhere is at least plausible. In a 2003 lecture at Caltech, Michael Crichton, a science fiction author, stated that, "Speaking precisely, the Drake equation is literally meaningless, and has nothing to do with science. I take the hard view that science involves the creation of testable hypotheses. The Drake equation cannot be tested and therefore SETI is not science. SETI is unquestionably a religion."
However, actual experiments by SETI scientists do not attempt to address the Drake equations for the existence of extraterrestrial civilizations anywhere in the universe, but are focused on specific, testable hypotheses (i.e., "do extraterrestrial civilizations communicating in the radio spectrum exist near sun-like stars within 50 light years of the Earth?").
Another reply to such criticism is that even though the Drake equation currently involves speculation about unmeasured parameters, it stimulates dialog on these topics. Then the focus becomes how to proceed experimentally.


Try The Drake's Equation For Yourself -

http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html


source : Wikipedia

Specifications (B-2A Block 30)

Data from Pace, Globalsecurity

General characteristics

• Crew: 2
• Length: 69 ft (21.0 m)
• Wingspan: 172 ft (52.4 m)
• Height: 17 ft (5.18 m)
• Wing area: 5,140 ft² (478 m²)
• Empty weight: 158,000 lb (71.7 t)
• Loaded weight: 336,500 lb (152.6 t)
• Max takeoff weight: 376,000 lb (170.6 t)
• Powerplant: 4× General Electric F118-GE-100 turbofans, 17,300 lbf (77 kN) each

Performance

• Maximum speed: Mach 0.95 (525 knots, 604 mph, 972 km/h)
• Range: 6,300 nmi (11,600 km, 6,450 mi)
• Service ceiling 50,000 ft (15,200 m)
• Wing loading: 67.3 lb/ft² (329 kg/m²)
• Thrust/weight: 0.205

Armament

• 2 internal bays for 50,000 lb (22,700 kg) of ordnance.
  • 80× 500 lb class bombs (Mk-82) mounted on Bomb Rack Assembly (BRA)
  • 36× 750 lb CBU class bombs on BRA
  • 16× 2000 lb class weapons (Mk-84, JDAM-84, JDAM-102) mounted on Rotary Launcher Assembly (RLA)
  • 16× B61 or B83 nuclear weapons on RLA

Later avionics and equipment improvements allow B-2A to carry JSOW and GBU-28s as well. The Spirit is also designated as a delivery aircraft for the AGM-158 JASSM when the missile enters service.

The B-2 Spirit is a multi-role bomber capable of delivering both conventional and nuclear munitions.

Along with the B-52 and B-1B, the B-2 provides the penetrating flexibility and effectiveness inherent in manned bombers. Its low-observable, or "stealth," characteristics give it the unique ability to penetrate an enemy's most sophisticated defenses and threaten its most valued, and heavily defended, targets. Its capability to penetrate air defenses and threaten effective retaliation provide an effective deterrent and combat force well into the 21st century.

The blending of low-observable technologies with high aerodynamic efficiency and large payload gives the B-2 important advantages over existing bombers. Its low-observability provides it greater freedom of action at high altitudes, thus increasing its range and a better field of view for the aircraft's sensors. Its unrefueled range is approximately 6,000 nautical miles (9,600 kilometers).

The B-2's low observability is derived from a combination of reduced infrared, acoustic, electromagnetic, visual and radar signatures. These signatures make it difficult for the sophisticated defensive systems to detect, track and engage the B-2. Many aspects of the low-observability process remain classified; however, the B-2's composite materials, special coatings and flying-wing design all contribute to its "stealthiness."

The B-2 has a crew of two pilots, an aircraft commander in the left seat and mission commander in the right, compared to the B-1B's crew of four and the B-52's crew of five.

The B-2 is intended to deliver gravity nuclear and conventional weapons, including precision-guided standoff weapons. An interim, precision-guided bomb capability called Global Positioning System (GPS) Aided Targeting System/GPS Aided Munition (GATS/GAM) is being tested and evaluated. Future configurations are planned for the B-2 to be capable of carrying and delivering the Joint Direct Attack Munition (JDAM) and Joint Air-to-Surface Standoff Missile.

B-2s, in a conventional role, staging from Whiteman AFB, MO; Diego Garcia; and Guam can cover the entire world with just one refueling. Six B-2s could execute an operation similar to the 1986 Libya raid but launch from the continental U.S. rather than Europe with a much smaller, more lethal, and more survivable force.

Background

The B-2 development program was initiated in 1981, and the Air Force was granted approval in 1987 to begin procurement of 132 operational B-2 aircraft, principally for strategic bombing missions. With the demise of the Soviet Union, the emphasis of B-2 development was changed to conventional operations and the number was reduced to 20 operational aircraft, plus 1 test aircraft that was not planned to be upgraded to an operational configuration. Production of these aircraft has been concurrent with development and testing.

The first B-2 was publicly displayed on Nov. 22, 1988, when it was rolled out of its hangar at Air Force Plant 42, Palmdale, Calif. Its first flight was July 17, 1989. The B-2 Combined Test Force, Air Force Flight Test Center, Edwards Air Force Base, Calif., is responsible for flight testing the engineering, manufacturing and development aircraft as they are produced. Three of the six developmental aircraft delivered at Edwards are continuing flight testing.

Whiteman AFB, Mo., is the B-2's only operational base. The first aircraft, Spirit of Missouri, was delivered Dec. 17, 1993. Depot maintenance responsibility for the B-2 is performed by Air Force contractor support and is managed at the Oklahoma City Air Logistics Center at Tinker AFB, Okla.

The prime contractor, responsible for overall system design and integration, is Northrop Grumman's Military Aircraft Systems Division. Boeing Military Airplanes Co., Hughes Radar Systems Group and General Electric Aircraft Engine Group are key members of the aircraft contractor team. Another major contractor, responsible for aircrew training devices (weapon system trainer and mission trainer) is Hughes Training Inc. (HTI) - Link Division, formerly known as C.A.E. - Link Flight Simulation Corp. Northrop Grumman and its major subcontractor HTI, are responsible for developing and integrating all aircrew and maintenance training programs.

The Air Force is accepting delivery of production B-2s in three configuration blocks--blocks 10, 20, and 30. Initial delivery will be 6 test aircraft, 10 aircraft in the block 10 configuration, 3 in the block 20 configuration, and 2 in the block 30 configuration.

Block 10 configured aircraft provide limited combat capability with no capability to launch conventional guided weapons. The Block 10 model carries only Mk-84 2,000-pound conventional bombs or gravity nuclear weapons. B-2s in this configuration are located at Whiteman Air Force Base and are used primarily for training. Block 20 configured aircraft have an interim capability to launch nuclear and conventional munitions, including the GAM guided munition. The Block 20 has been tested with the Mk-84, 2,000-pound, general-purpose bombs and the CBU-87/B Combined Effects Munition cluster bombs (low-altitude, full-bay release).

Block 30 configured aircraft are fully capable and meet the essential employment capabilities defined by the Air Force. The first fully configured Block 30 aircraft, AV-20 Spirit of PENNSYLVANIA, was delivered to the Air Force on 07 August 1997. Compared to the Block 20, the Block 30s have almost double the radar modes along with enhanced terrain-following capability and the ability to deliver additional weapons, including the Joint Direct Attack Munition and the Joint Stand Off Weapon. Other features include incorporation of configuration changes needed to make B-2s conform to the approved radar signature; replacement of the aft decks; installation of remaining defensive avionics functions; and installation of a contrail management system.

All block 10, 20, and test aircraft are to eventually be modified to the objective block 30 configuration. This modification process began in July 1995 and is scheduled to be completed in June 2000.

The B-2 fleet will have 16 combat-coded aircraft by the second quarter of FY00,

Upgrades

Link-16 – Providing Line-of-Sight (LOS) data for aircraft-to-aircraft, aircraft-to-C2, and aircraft-to-sensor connectivity, Link-16 is a combat force multiplier that provides U.S. and other allied military services with fully interoperable capabilities and greatly enhances tactical Command, Control, Communication, and Intelligence mission effectiveness. Link-16 provides increased survivability, develops a real-time picture of the theater battlespace, and enables the aircraft to quickly share information on short notice (target changes). Connectivity – DoD requires survivable communications media for command and control of nuclear forces. To satisfy the requirement, the Air Force plans to deploy an advanced Extremely High Frequency (EHF) satellite communications constellation. This constellation will provide a survivable, high capability communication system. Based on favorable results from a funded risk reduction study, the B-2 will integrate an EHF communication capability satisfying connectivity requirements. Digital Engine Controller - The current analog engine controllers are high failure items, and without funding, ACC will be forced to ground aircraft beginning approximately FY08. Replacement of the engine controllers will improve the B-2’s performance and increase supportability, reliability, and maintainability. Computers/Processors - With advances in computer technology and increased demands on the system, the B-2’s computers will need to be replaced with state-of-the-art processors. Although reliable, maintaining the present processors will become increasingly difficult and costly.

Signature Improvements - The B-2’s signature meets operational requirements against today’s threats. As advanced threats proliferate, it will be prudent to investigate advanced signature reduction concepts and determine if it is necessary to improve the B-2’s low observable signature. CANDIDATE LONG TERM UPGRADES BEYOND FY 15 TOTAL The basis for the useful life of the B-2 includes data from initial Developmental Test and Evaluation analysis. Data indicates the aircraft should be structurally sound to approximately 40,000 flight hours using current mission profiles. Analysis further suggests that the rudder attachment points are the first structural failure item. The B-2 has not implemented an ASIP similar to the other bombers, and this makes it difficult to predict the economic service life and attrition rate. However, a notional projection, based on the B-52, predicts one aircraft will be lost each 10 years. This attrition rate, plus attrition due to service life, will erode the B-2 force below its requirement of 19 aircraft by 2027.

Tactical delivery tactics use patterns and techniques that minimize final flight path predictability, yet allows sufficient time for accurate weapons delivery. For conventional munitions. Bomb Rack Assembly (BRA) weapons delivery accuracies depend on delivery altitude. For a weapons pass made at 5,000 ft above ground level [AGL] or below, the hit criteria is less than or equal to 300 feet. For a weapons pass made above 5,000 feetAGL, the hit criteria is less than or equal to 500 feet. Similarly, Rotary Launcher Assembly (RLA) delivery of conventional or nuclear weapons (i.e. Mk-84, B-83, B-61) is altitude dependent. For a weapons pass made at 5,000 feet AGL or below, the hit criteria is less than or equal to 300 feet. For a weapons pass made above 5,000 ft AGL, the hit criteria is less than or equal to 500 feet. The hit criteria for a weapons pass made with GAM/ JDAM munitions is less than or equal to 50 feet.

Design

As with the B-52 Stratofortress and B-1 Lancer, the B-2 provides the versatility inherent in manned bombers. Like other bombers, its assigned targets can be canceled or changed while in flight, the particular weapon assigned to a target can be changed, and the timing of attack, or the route to the target can be changed while in flight. In addition, its low-observable, or "stealth", characteristics give it the ability to penetrate an enemy's most sophisticated anti-aircraft defenses to attack its most heavily defended targets.

The blending of low-observable technologies with high aerodynamic efficiency and large payload gives the B-2 significant advantages over previous bombers. Its range is approximately 6,000 nautical miles (11,100 km) without refueling. Also, its low-observation ability provides the B-2 greater freedom of action at high altitudes, thus increasing its range and providing a better field of view for the aircraft's sensors. It combines GPS Aided Targeting System (GATS) with GPS-aided bombs such as Joint Direct Attack Munition (JDAM). This uses its passive electronically scanned array APQ-181 radar to correct GPS errors of targets and gain much better than laser-guided weapon accuracy when "dumb" gravity bombs are equipped with a GPS-aided "smart" guidance tail kit. It can bomb 16 targets in a single pass when equipped with 1,000 or 2,000-pound bombs, or as many as 80 when carrying 500-lb bombs.

The B-2's stealth comes from a combination of reduced acoustic, infrared, visual and radar signatures, making it difficult for opposition defenses to detect, track and engage the aircraft. Many specific aspects of the low-observability process remain classified.

The B-2 represents a further advancement of technology exploited for the F-117. Pyotr Ufimtsev, whose theoretical work made the F-117 and B-2 possible, was hired by Northrop at one time. Additionally, the B-2's composite materials, special coatings and flying wing design (which reduces the number of leading edges) contribute to its stealth abilities. The B-2 uses radar absorbent material and coatings that require climate-controlled hangars for maintenance. The engines are buried within the wing to conceal the induction fans and hide their exhaust.

The B-2 has a crew of two: a pilot in the left seat, and mission commander in the right. The B-2 has a provision for a third crew member if required in the future. For comparison, the B-1B has a crew of four and the B-52 has a crew of five. B-2 crews have been used to pioneer sleep cycle research to improve crew performance on long flights. The B-2 is highly automated, and unlike two-seat fighters, one crew member can sleep, use a flush toilet or prepare a hot meal while the other monitors the aircraft.

The USAF has funded a project to upgrade the B-2s weapon control systems so new weapons can be used, including weapons intended to hit moving targets.

The V-22 Osprey is a tiltrotor vertical/short takeoff and landing (VSTOL), multi-mission air-craft developed to fill multi-Service combat operational requirements. The MV-22 will replace the current Marine Corps assault helicopters in the medium lift category (CH-46E and CH-53D), contributing to the dominant maneuver of the Marine landing force, as well as supporting focused logistics in the days following commencement of an amphibious operation. The Air Force variant, the CV-22, will replace the MH-53J and MH-60G and augment the MC-130 fleet in the USSOCOM Special Operations mission. The Air Force requires the CV-22 to provide a long-range VTOL insertion and extraction capability. The tiltrotor design combines the vertical flight capabilities of a helicopter with the speed and range of a turboprop airplane and permits aerial refueling and world-wide self deployment.

Two 6150 shaft horsepower turboshaft engines each drive a 38 ft diameter, 3-bladed proprotor. The proprotors are connected to each other by interconnect shafting which maintains proprotor synchronization and provides single engine power to both proprotors in the event of an engine failure. The engines and flight controls are controlled by a triply redundant digital fly-by-wire system.

The airframe is constructed primarily of graphite-reinforced epoxy composite material. The composite structure will provide improved strength to weight ratio, corrosion resistance, and damage tolerance compared to typical metal construction. Battle damage tolerance is built into the aircraft by means of composite construction and redundant and separated flight control, electrical, and hydraulic systems. An integrated electronic warfare defensive suite including a radar warning receiver, a missile warning set, and a countermeasures dispensing system, will be installed.

BACKGROUND INFORMATION

The V-22 is being developed to meet the provisions of the April 1995 Joint Multi-Mission Vertical Lift Aircraft (JMVX) Operational Requirements Document (ORD) for an advanced vertical lift aircraft. The JMVX ORD calls for an aircraft that would provide the Marine Corps and Air Force the ability to conduct assault support and long-range, high-speed missions requiring vertical takeoff and landing capabilities.

Since entry into FSD in 1986, the V-22 T&E program has concentrated principally on engineering and integration testing by the contractors. Three periods of formal development test by Naval Air Warfare Center-Aircraft Division (NAWCAD) Patuxent River, plus OTA participation in integrated test team (ITT) activities at Patuxent River, have provided some insight into the success of the development effort. After transition to EMD in 1992, an integrated contractor/government test team conducted all tests until OT-IIA in 1994. Since then, two additional periods of OT&E have been conducted.

The first operational test period (OT-IIA) was performed by COMOPTEVFOR, with assistance from AFOTEC, from May 16 to July 8, 1994, and accomplished 15 hours of actual flight test operations, within an extremely restricted flight envelope. The Navy, with Air Force support, published a joint evaluation report addressing most mission areas the V-22 is to perform.

OT-IIB was conducted from September 9, to October 18, 1995, and comprised 10 flight hours in 18 OT&E flights, plus ground evaluations. A joint Air Force/Navy OT-IIB report was published. Partly in response to DOT&E concern expressed over the severity of V-22 downwash in a hover observed during OT-IIA, the Navy conducted a limited downwash assessment concurrently with OT-IIB, from July to October 1995.

TEST & EVALUATION ACTIVITY

In accordance with the approved TEMP, OT-IIC was conducted in six phases at NAS Patuxent River and Bell-Boeing facilities in Pennsylvania and Texas, from October 1996, through May 1997.

Significant flight limitations were placed on the FSD V-22 in OT&E to date, including:

• not cleared to hover over unprepared landing zones until OT-IIC

• no operational internal or external loads or passengers

• moderate gross weights only

• not cleared to hover over water.

In addition, FSD aircraft equipment was not representative of any mission configuration. Together, these aircraft clearance and configuration limits produced an extremely artificial test environment for OT-IIC.

The OT-IIB report expressed serious concerns regarding the potential downwash effects, and recommended further investigation. While a limited assessment of downwash and workaround procedures was included in OT-IIC, complete resolution of the downwash issue will not be possible until the completion of OPEVAL, just prior to milestone III in 1999.

The Navy is conducting an aggressive LFT&E program on representative V-22 components and assemblies, in compliance with a DOT&E-approved alternative LFT&E plan. The V-22 program was granted a waiver from full-up, system-level LFT&E in April, 1997. The vulnerability testing that the program is performing is appropriate and will result in the improvement of aircraft survivability.

The V-22 program TEMP was last approved by DOT&E on September 28, 1995, and will be updated prior to each OT&E period scheduled.

TEST & EVALUATION ASSESSMENT

With DOT&E encouragement, the Navy greatly expanded the scope of OT-IIC to get better insight into the effectiveness and suitability of the EMD design. The results, while not yet conclusive regarding the potential operational effectiveness and suitability of operational aircraft, were encouraging. The six phases of the OT-IIC Assessment included: (1) shipboard assessment, (2) maintenance demonstrations, (3) tactical aircraft employment via FSD aircraft and manned flight simulator, (4) operational training plans, (5) program documentation review, and (6) software analysis.

In assessing the operational effectiveness and suitability COIs, COMOPTEVFOR and AFOTEC found that in most cases, only moderate risk exists that the COIs will not be satisfactorily resolved when development is complete. Enhancing features observed during OT-IIC included aircraft payload, range and speed characteristics better than the stated operational requirements. In addition, reliability, availability and maintainability of the EMD aircraft appeared to be significantly improved over those of the FSD aircraft.

Several areas of concern first discovered in OT-IIA or OT-IIB remain unresolved because of limitations to the EMD flight test operations. These concerns include severe proprotor downwash effects during personnel insertion and extraction via hoist or rope. In addition, concerns exist in the areas of communications, navigation , and crew field of view. New concerns arising from OT-IIC regarding the EMD schedule are being addressed by the program manager. Also, the reliability and maintainability of a few subsystems will require management attention. Despite these concerns, the V-22 design remains potentially operationally effective and suitable.

The aircraft's prime contractors include Boeing Company's helicopter division in Ridley Park, PA, and Bell Helicopter Textron of Fort Worth TX. In 1986 the cost of a single V-22 was estimated at $24 million, with 923 aircraft to be built. In 1989 the Bush administration cancelled the project, at which time the unit cost was estimated at $35 million, with 602 aircraft. The V-22 question caused friction between Secretary of Defense Richard B. Cheney and Congress throughout his tenure. DoD spent some of the money Congress appropriated to develop the aircraft, but congressional sources accused Cheney, who continued to oppose the Osprey, of violating the law by not moving ahead as Congress had directed. Cheney argued that building and testing the prototype Osprey would cost more than the amount appropriated. In the spring of 1992 several congressional supporters of the V-22 threatened to take Cheney to court over the issue. A little later, in the face of suggestions from congressional Republicans that Cheney's opposition to the Osprey was hurting President Bush's reelection campaign, especially in Texas and Pennsylvania where the aircraft would be built, Cheney relented and suggested spending $1.5 billion in fiscal years 1992 and 1993 to develop it. He made clear that he personally still opposed the Osprey and favored a less costly alternative.

The program was revived by the incoming Clinton administration, and current plans call for building 458 Ospreys for $37.3 billion, or more than $80 million apiece, with the Marines receiving 360 Ospreys, the Navy 48 and the Air Force 50. The first prototype flew in 1989. As of early 2000 three test aircraft had crashed: no one was killed in the 1991 crash, an accident in 1992 killed seven men, and the third in April 2000 killed 19 Marines.

Specifications

Data from Boeing Integrated Defense Systems,Naval Air Systems Command, and the CV-22 Air Force Fact Sheet.

General characteristics

• Crew: two pilots
• Capacity: 24 troops (seated), 32 troops (floor loaded) or up to 15,000 pounds of cargo
• Length: 57 ft 4 in (17.5 m)
• Rotor diameter: 38 ft 0 in (11.6 m)
• Wingspan: 46 ft (14 m); 84 ft 7 in (including rotors))
• Height: 22 ft 1 in (overall - nacelles vertical) (17 ft 11 in 5.5 m (at top of tailfins))
• Disc area: 2,268 ft² (212 m²)
• Wing area: 301.4 ft² (28 m²)
• Empty weight: 33,140 lb (15,032 kg)
• Loaded weight: 47,500 lb (21,500 kg)
• Max takeoff weight: 60,500 lb (27,400 kg)
• Powerplant: 2× Rolls-Royce Allison Rolls-Royce T406 (AE 1107C-Liberty) turboshafts, 6,150 hp (4,590 kW) each

Performance

• Maximum speed: 275 knots (316 mph, 509 km/h)
• Cruise speed: 214 knots (246 mph, 396 km/h) at sea level
• Range: 879 nmi (1,011 mi, 1,627 km) (unrefueled)
• Combat radius: 370 nmi (430 mi, 690 km)
• Ferry range: 2,417 nm (2,781 mi, 4,476 km)
• Service ceiling 26,000 ft (7,925 m)
• Rate of climb: 2,320 ft/min (11.8 m/s)
• Disc loading: 20.9 lb/ft² @ 47,500 lb GW (102.23 kg/m²)
• Power/mass: 0.259 hp/lb (427 W/kg)

MV-22s will be deployed to all Marine Corps medium lift active duty and reserve tactical squadrons, the medium lift training squadron (FRS), and the executive support squadron (HMX)

The Messerschmitt Me 262 Schwalbe (German for Swallow) was the world's first operational turbojet fighter aircraft. It was produced in World War II and saw action starting in 1944 as a multi-role fighter/bomber/reconnaissance/interceptor warplane for the Luftwaffe. German pilots nicknamed it the Sturmvogel (Stormbird), while the Allies called it the Turbo. The Me 262 had a negligible impact on the course of the war due to its late introduction, with 509 claimed Allied kills (although higher claims are sometimes made) against the loss of more than 100 Me 262s.

Specifications (Messerschmitt Me 262 A-1a)

Data from Quest for Performance Original Messerschmitt documents

General characteristics

• Crew: One
• Length: 10.60 m (34 ft 9 in)
• Wingspan: 12.60 m (41 ft 6 in)
• Height: 3.50 m (11 ft 6 in)
• Wing area: 21.7 m² (234 ft²)
• Empty weight: 4,404 kg (9,709 lb)
• Loaded weight: 7,130 kg (15,720 lb)
• Max takeoff weight: 6977 kg (15,381 lb)
• Powerplant: 2× Junkers Jumo 004B-1 turbojets, 8.8 kN (1,980 lbf) each
• Aspect ratio: 7.23

Performance

• Maximum speed: 900 km/h (559 mph)
• Range: 1,050 km (652 mi)
• Service ceiling 11,450 m (37,565 ft)
• Rate of climb: 1,200 m/min (3,900 ft/min)
• Thrust/weight: 0.28

Armament

• Guns: 4x 30 mm MK 108 cannons (A-2a: two cannons)
• Rockets: 24x 55 mm (2.2 in) R4M rockets
• Bombs: 2x 250 kg (550 lb) bombs (A-2a only)

Design and development

The Me 262 was already being developed as Projekt P.1065 before the start of World War II. Plans were first drawn up in April 1939, and the original design was very similar to the plane that eventually entered service. The progression of the original design into service was delayed greatly by technical issues involving the new jet engines. Funding for the jet program was also initially lacking, as many high-ranking officials thought the war could easily be won with conventional aircraft. Adolf Hitler had envisioned the Me 262 not as a defensive interceptor, but as an offensive ground attack/bomber, almost as a very high speed, light payload Schnellbomber. His edict resulted in the development of the Sturmvogel (Stormbird) variant. It is debatable to what extent Hitler's interference extended the delay in bringing the Swallow into operation.

The aircraft was originally designed with a tail wheel undercarriage and the first four prototypes (Me 262 V1-V4) were built with this configuration, but it was discovered on an early test run that the engines and wings "blanked" the stabilizers, giving almost no control on the ground, as well as serious runway surface damage from the hot jet exhaust. Changing to a tricycle undercarriage arrangement, initially a fixed undercarriage on the "V5" fifth prototype, then fully retractable on the sixth (V6, with code VI+AA) and succeeding aircraft, corrected this problem.

Although it is often stated the Me 262 is a "swept wing" design, the production Me 262 had a leading edge sweep of only 18.5°. This was done primarily to properly position the center of lift relative to the centre of mass and not for the aerodynamic benefit of increasing the critical Mach number of the wing. The sweep was too slight to achieve any significant advantage. This happened after the initial design of the aircraft, when the engines proved to be heavier than originally expected. On 1 March 1940, instead of moving the wing forward on its mount, the outer wing was positioned slightly backwards to the same end. The middle section of the wing remained unswept.. Based on data from the AVA Göttingen and windtunnel results, the middle section was later swept.

The first test flights began on 18 April 1941, with the Me 262 V1 example, bearing its Stammkennzeichen radio code letters of PC+UA, but since its intended BMW 003 turbojets were not ready for fitting, a conventional Junkers Jumo 210 engine was mounted in the V1 prototype's nose, driving a propeller, to test the Me 262 V1 airframe. When the BMW 003 engines were finally installed, the Jumo was retained for safety, which proved wise as both 003s failed during the first flight and the pilot had to land using the nose mounted engine alone.

The V3 third prototype airframe, with the code PC+UC, became a true "jet" when it flew on 18 July 1942 in Leipheim near Günzburg, Germany, piloted by Fritz Wendel. This was almost nine months ahead of the British Gloster Meteor's first flight on 5 March 1943. The 003 engines, which were proving unreliable, were replaced by the newly available Junkers Jumo 004. Test flights continued over the next year, but the engines continued to be unreliable. Airframe modifications were complete by 1942, but hampered by the lack of engines, serial production did not begin until 1944. This delay in engine availability was in part due to the shortage of strategic materials, especially metals and alloys able to handle the extreme temperatures produced by the jet engine. Even when the engines were completed, they had an expected operational lifetime of approximately 50 hours; in fact, most 004s lasted just 12 hours. A pilot familiar with the Me 262 and its engines could expect approximately 20 to 25 hours of life from the 004s. Changing a 004 engine was intended to require three hours, but typically took eight to nine due to poorly made parts and inadequate training of ground crews.

Turbojet engines have less thrust at low speed than propellers and as a result, low-speed acceleration is relatively poor. It was more noticeable for the Me 262 as early jet engines (before the invention of afterburners) responded slowly to throttle changes. The introduction of a primitive autothrottle late in the war only helped slightly. Conversely, the higher power of jet engines at higher speeds meant the Me 262 enjoyed a much higher climb speed. Used tactically, this gave the jet fighter an even greater speed advantage in climb rate than level flight at top speed.

With one engine out, the Me 262 still flew well, with speeds of 450 to 500 km/h (280 to 310 mph), but pilots were warned never to fly slower than 300 km/h (186 mph) on one engine, as the asymmetrical thrust would cause serious problems.

Operationally, the Me 262 had an endurance of 60 to 90 minutes.

Operational history

In April 1944, Erprobungskommando 262 was formed at Lechfeld in Bavaria as a test unit (Jaeger Erprobungskommando Thierfelder) to introduce the 262 into service and train a core of pilots to fly it. On 26 July 1944, Lt. Alfred Schreiber with the 262 A-1a W.Nr. 130 017 downed a Mosquito reconnaissance aircraft. It was the first victory for a turbojet fighter aircraft in aviation history. Major Walter Nowotny was assigned as commander after the death of Werner Thierfelder in July 1944, and the unit redesignated Kommando Nowotny. Essentially a trials and development unit, it holds the distinction of having mounted the world's first jet fighter operations. Trials continued slowly, with initial operational missions against the Allies in August 1944 allegedly downing 19 Allied aircraft for six Me 262s lost, although these claims have never been verified by cross-checking with USAAF records. The RAF Museum holds no intelligence reports of RAF aircraft engaging in combat with Me 262s in August, although there is a report of an unarmed encounter between an Me 262 and a Mosquito. Despite orders to stay grounded, Nowotny chose to fly a mission against an enemy formation. After an engine failure, he was shot down and killed on 8 November 1944 by 1st Lt Edward “Buddy” Haydon of the 357th Fighter Group, USAAF and Capt Ernest “Feeb” Fiebelkorn of the 20th Fighter Group, USAAF. The "Kommando" was then withdrawn for further training and a revision of combat tactics to optimise the 262's strengths.

By January 1945, Jagdgeschwader 7 (JG 7) had been formed as a pure jet fighter unit, although it would be several weeks before it was operational. In the meantime, a bomber unit—I Gruppe, Kampfgeschwader 54 (KG 54)—had re-equipped with the Me 262 A-2a fighter-bomber for use in a ground attack role. However, the unit lost 12 jets in action in two weeks for minimal returns.

Jagdverband 44 (JV 44) was another Me 262 fighter unit formed in February, by Lieutenant General Adolf Galland, who had recently been dismissed as Inspector of Fighters. Galland was able to draw into the unit many of the most experienced and decorated Luftwaffe fighter pilots from other units grounded by lack of fuel.

During March, Me 262 fighter units were able, for the first time, to mount large scale attacks on Allied bomber formations. On 18 March 1945, 37 Me 262s of JG 7 intercepted a force of 1,221 bombers and 632 escorting fighters. They shot down 12 bombers and one fighter for the loss of three Me 262s. Although a four-to-one ratio was exactly what the Luftwaffe would have needed to make an impact on the war, the absolute scale of their success was minor, as it represented only one per cent of the attacking force. In 1943 and early 1944, the USAAF had been able to keep up offensive operations despite loss ratios of 5% and more, and the few available Me 262s could not inflict sufficient losses to hamper their operations.

Several two-seat trainer variants of the Me 262, the Me 262 B-1a, had been adapted as night fighters, complete with on-board FuG 218 Neptun radar and "stag's antlers" (Hirschgeweih) antenna, as the B-1a/U1 version. Serving with 10 Staffel, Nachtjagdgeschwader 11, Night Fighter wing, near Berlin, these few aircraft (alongside several single seat examples) accounted for most of the 13 Mosquitoes lost over Berlin in the first three months of 1945. However, actual intercepts were generally or entirely made using Wilde Sau methods, rather than AI radar-controlled interception. As the two-seat trainer was largely unavailable, many pilots had to make their first flight in a jet in a single seater without an instructor.

Despite its deficiencies, the Me 262 clearly signaled the beginning of the end of piston-engined aircraft as effective fighting machines. Once airborne, it could accelerate to speeds well over 800 km/h (500 mph), over 150 km/h (93 mph) faster than any Allied fighter operational in the European Theater of Operations.

The Me 262's top ace was probably Hauptmann Franz Schall with 17 kills which included six four-engine bombers and ten P-51 Mustang fighters, although night fighter ace Oberleutnant Kurt Welter claimed 25 Mosquitos and two four-engined bombers shot down by night and two further Mosquitos by day flying the Me 262. Most of Welter's claimed night kills were achieved in standard radar-less aircraft, even though Welter had tested a prototype Me 262 fitted with Neptun radar. Another candidate for top ace on the aircraft was Heinrich Bär, who claimed 16 enemy aircraft while flying the Me 262.

Anti-bomber tactics

The standard approach against bomber formations, which were travelling at cruise speed, called for the Me 262 to approach the bombers from the rear at a higher altitude, diving in below the bomber's flight level to get additional speed before gaining altitude again and, on reaching the bomber's level, opening fire with its four 30 mm cannon at 600 m (656 yard) range.

Allied bomber gunners found that their electric gun turrets had problems tracking the jets. Target acquisition was difficult because the jets closed into firing range quickly and had to remain in firing position only briefly using their standard attack profile.

Eventually, new combat tactics were developed to counter the Allied bombers' defences. Me 262s equipped with R4M rockets would approach from the side of a bomber formation, where their silhouettes were widest, and while still out of range of the .50 caliber guns, fire a salvo of these explosive rockets. The explosive power of only one or two of these rockets was capable of downing even the famously rugged B-17- a strike on an enemy aircraft meant its total annihilation. Although this tactic was effective, it came too late to have a real effect on the war. This method of attacking bombers became the standard until the invention and mass deployment of guided missiles. Some nicknamed this tactic the "Luftwaffe's Wolf Pack", as the fighters would often make runs in groups of two or three, fire their rockets, then return to base.

On 1 September 1944, USAAF General Carl Spaatz expressed the fear that if greater numbers of German jets appeared, they could inflict losses heavy enough to force cancellation of the Allied daylight bombing offensive.

Counter-jet tactics

Tactics against the Me 262 developed quickly despite its great speed advantage. Allied bomber escort fighters would fly high above the bombers — diving from this height gave them extra speed, thus reducing the speed difference. The Me 262 was less maneuverable than the P-51 and trained Allied pilots could catch up to a turning Me 262, though the only reliable way of dealing with the jets, as with the even faster Komet rocket fighters, was to attack them on the ground and during take off and landing. Luftwaffe airfields that were identified as jet bases were frequently bombed by medium bombers, and Allied fighters patrolled over the fields to attack jets trying to land. The Luftwaffe countered by installing flak alleys along the approach lines in order to protect the Me 262s from the ground and providing top cover with conventional fighters during takeoff and landing. Nevertheless, in March and April 1945, Allied fighter patrol patterns over Me 262 airfields resulted in numerous losses of jets and serious attrition of the force.

Another experimental tactic was installing nitrous oxide injection, much like the Germans' own GM-1 system, into Mustangs. When chasing an Me 262, the pilot could press a button injecting nitrous oxide into the engine, producing a quick burst of speed.

Other Allied fighters that encountered the Me 262 included the British Supermarine Spitfire, Hawker Tempest and the Soviet Lavochkin La-7. The first recorded Allied destruction of a Me 262, belonging to the unit known as Kommando Schenk, was on 28 August 1944, claimed as destroyed by 78th FG pilots Major Joseph Myers and 2nd Lt. Manford O. Croy flying P-47s. Oberfeldwebel Hieronymus "Ronny" Lauer of I KG(J) 51, on a landing pattern crash landed his 262 to get away from the Allied fighters, which then destroyed the Me 262 in strafing attacks. The first Me 262 shot down in combat, belonging to 3. Staffel/Kampfgeschwader 51, with unit code letters "9K+BL", was on 5 October 1944, by Spitfire IXs of 401 RCAF. The 262 pilot was H.C. Butmann in WNr 170093 of 3./KG51. The Lavochkin was the only Soviet fighter to shoot down a German jet, with La-7 ace Ivan Nikitovich Kozhedub, downing an Me 262 on 15 February 1945 over eastern Germany.

High speed research

Willy Messerschmitt regarded the Me 262 as only an interim type when it went into production.

Swept wings had been proposed as early as 1935 by Adolf Busemann, and Messerschmitt had researched the topic from 1940. In April 1941, he proposed fitting a 35° swept wing (Pfeilflügel II, literally arrow wing II) to the Me 262, the same wing sweep angle that would later be used on both the American F-86 Sabre and Soviet MiG-15 fighter jets. Though this was not implemented, he continued with the projected HG II and HG III (Hochgeschwindigkeit, high speed) derivatives in 1944, which were designed with a 35° and 45° wing sweep, respectively.

Interest in high-speed flight, which led him to initiate work on swept wings starting in 1940, is evident from the advanced developments Messerschmitt had on his drawing board in 1944. While the Me 262 HG I actually flight tested in 1944 had only small changes compared to combat aircraft, most notably a low-profile canopy (tried as the Rennkabine (literally racing cabin) on the Me 262 V9 prototype for a short time) to reduce drag, the HG II and HG III designs were far more radical. The projected HG II combined the low-drag canopy with a 35° wing sweep and a butterfly tail. The HG III had a conventional tail, but a 45° wing sweep and turbines embedded in the wingroot.

Messerschmitt also conducted a series of flight tests with the series production Me 262. In dive tests, it was determined that the Me 262 went out of control in a dive at Mach 0.86, and that higher Mach numbers would lead to a nose-down trim that could not be countered by the pilot. The resulting steepening of the dive would lead to even higher speeds and disintegration of the airframe due to excessive negative g loads.

The HG series of Me 262 derivatives was estimated to be capable of reaching transonic Mach numbers in level flight, with the top speed of the HG III being projected as Mach 0.96 at 6 km altitude. Despite the necessity to gain experience in high-speed flight for the HG II and III designs, Messerschmitt undertook no attempts to exceed the Mach 0.86 limit for the Me 262.

After the war, the Royal Aircraft Establishment, at that time one of the leading institutions in high-speed research, re-tested the Me 262 to help with British attempts at exceeding Mach 1. The RAE achieved speeds of up to Mach 0.84 and confirmed the results from the Messerschmitt dive tests. Similar tests were run by the Soviets. No attempts were made to exceed the Mach limit established by Messerschmitt.

After Willy Messerschmitt's death, the former Me 262 pilot Hans Guido Mutke claimed to be the first person to exceed Mach 1, on 9 April 1945 in a Me 262 in a "straight-down" 90° dive. This claim is disputed because it is only based on Mutke's memory of the incident, which recalls effects other Me 262 pilots observed below the speed of sound at high indicated airspeed, but with no altitude reading required to determine the actual speed. Furthermore, the pitot tube used to measure airspeed in aircraft can give falsely elevated readings as the pressure builds up inside the tube at high speeds. Finally, the Me 262 wing had only a slight sweep incorporated for trim (center of gravity) reasons and likely would have suffered structural failure due to divergence at high transonic speeds. One airframe (Me 262 HG1 V9 WNr130 004 VI+AD ) was prepared with the low-profile Rennkabine racing canopy and may have achieved an unofficial record speed of 606 mph, altitude unspecified.

Postwar history and flyable reproductions

After the end of the war, the Me 262 and other advanced German technologies were quickly swept up by the Americans (as part of the USAAF's Operation Lusty), British, and Soviets. Many Me 262s were found in readily-repairable condition and were confiscated.

The Me 262 was found during testing to have advantages over the early models of the Gloster Meteor. It was faster, had better cockpit visibility to the sides and rear (mostly due to the canopy frame and the discoloration caused by the plastics used in the Meteor's construction), and was a superior gun platform, as the early Meteors had a tendency to snake at high speed and exhibited "weak" aileron response. The Me 262 did have a shorter combat range than the Meteor.

The USAAF compared the P-80 Shooting Star and Me 262 concluding, "Despite a difference in gross weight of nearly 2,000 lb (907 kg), the Me 262 was superior to the P-80 in acceleration, speed and approximately the same in climb performance. The Me 262 apparently has a higher critical Mach number, from a drag standpoint, than any current Army Air Force fighter." The Army Air Force also tested an example of the Me 262A-1a/U3 (US flight evaluation serial FE-4012), an unarmed photoreconnaissance version, which was fitted with a fighter nose and given an overall smooth finish. It was used for performance comparisons against the P-80. During testing between May and August 1946, the aircraft completed eight flights, lasting four hours and 40 minutes. Testing was discontinued after four engine changes were required during the course of the tests, culminating in two single-engine landings.

These aircraft were extensively studied, aiding development of early U.S. and Soviet jet fighters. The F-86 Sabre, designed by the engineer Edgar Schmued, used the Me 262 airfoil (Messerschmitt Wing A) and a slat design similar to that of the Me 262.

The Czechoslovak aircraft industry continued to produce single-seater (designated Avia S-92) and two-seater (designated Avia CS-92) variants of the Me 262 after World War II. From August 1946, a total of nine single-seater S-92 and three two-seater CS-92 planes were completed and test flown. They were introduced in 1947 and in 1950 they were supplied to the 5th Fighter Squadron. These were kept flying as late as 1957. They were the first jet fighters to serve in the Czechoslovak Air Force. Both versions are on display at the Prague Aero museum in Kbely.

In January 2003, the American Me 262 Project completed flight testing to allow for delivery of near-exact reproductions of several versions of the Me 262 including at least two B-1c two-seater variants, one A-1c single seater and two "convertibles" that could be switched between the A-1c and B-1c configurations. All are powered by General Electric J85 engines and feature additional safety features, such as upgraded brakes and strengthened landing gear. The "c" suffix refers to the new J-85 powerplant and has been informally assigned with the approval of the Messerschmitt Foundation in Germany. Flight testing of the first newly manufactured Me 262 A-1c (single seat) variant was completed in August 2005. The first of these machines went to a private owner in the southwestern United States, while the second was delivered to the Messerschmitt Foundation at Manching, Germany. This aircraft conducted a private test flight in late April 2006, and made its public debut in May at the Berlin Air Show (ILA 2006). The new Me 262 flew during the public flight demonstrations. Me 262 Werk Number 501241 was delivered to the Collings Foundation as White 1 of JG 7. This aircraft will be offering ride-along flights starting in 2008

source : Wikipedia