From: megazone@realsoon.WPI.EDU (MegaZone23)
Newsgroups: sci.aeronautics,rec.aviation.military,rec.aviation.misc
Subject: Research- paper [long]
Date: 15 Oct 92 16:20:20 GMT
Organization: Worcester Polytechnic Institute
NNTP-Posting-Host: realsoon.wpi.edu

This is another of the lovely papers I've written for this terrific school.
(The terms over, so I'm happy ok?) It is a short history on government research
and its use. Snagged me an 'A'....

          Benefits of Government Research in Aerospace 
                   for the Civilian Market

                      by Brian D. Bikowicz
                     (megazone@wpi.wpi.edu)

                             SS2302
                          Prof. Heaton

                         April 21, 1992

     The United States has long enjoyed a lead in the aerospace
industry over the rest of the industrialized world. Boeing and
McDonnell-Douglas, our two main commercial manufacturers, are sold
out over five years in advance. It is said that imitation is the
sincerest form of flattery, and, if that is so, the American
manufacturers should feel very flattered. For many years designs
originating in the United States have been built overseas, either
under license or as unauthorized copies. We have come to take our
lead for granted, unless specific programs, such as Japan's FSX,
seem to threaten it. But we should ask ourselves where much of the
technology which helps us maintain our lead came from. Exactly who
does the risky research and development work? In the United States,
as in most countries, the government is responsible for most
research into aerospace. Many of the technologies we either take
for granted, or are not even normally aware of, were developed by
the government. There are far too many examples to list them all,
but there are a few major examples which should convey the
important role that government has played in the development of new
technologies. There are thousands, if not millions, of small
innovations which have found their way into public use. As well as
new synthetic materials which were originally developed for
aerospace use and are now public domain. Even the technology to
work with titanium, which is now used extensively for artificial
joints. There are so many small spinoffs that NASA publishes a book
to list them. So this paper is limited to a few large, far reaching
examples.
     In the early years of aviation the sheer adventure of creating
a flying machine fueled most of the development which took place.
Aeronautical development was very much a trial and error system.
Inventors tinkered with their own systems and made small
improvements to the basic designs of the day. When the Wright
brothers made their successful flight at Kitty Hawk on December 17,
1903 they could hardly foresee the giants which would someday roam
the skies. The B747, DC10, MD11, A300, and L1011 commercial
airliners and the C-5, C-141, C-17, and An-124 military transports,
or the largest of all, the Soviet An-225 Dream. Their first flight
could have taken place inside many of these aircraft. Yet that is
where it all started. Their frail craft lifted off into a 27 mile
per hour wind that day. Today we have aircraft which can accelerate
to supersonic speeds using normal thrust, and then cruise there for
extended periods, known as supercruise. The data which goes into
the design of nearly all aircraft comes from many sources, but much
of it derives from Government research.
     The National Aeronautics and Space Administration, NASA, is
well known for the variety of research projects it has run, or is
currently running. Before NASA there was NACA, the National
Advisory Committee on Aeronautics. NACA became NASA with the
establishment of the space program. One of the programs run by NACA
was airfoil research. NACA did the preliminary work on developing
new airfoil cross-sections, and they developed a numbering system
still in use today. Many airfoils are referred to by their NACA
numbers. The tables which the numbers fit supply all the data for
the airfoil, such as lift and drag for varying airspeeds. NACA
created an extremely useful database used by designers the world
over. At the time this was a long, tedious, and expensive process
which no individual firm wanted to fund. Instead most manufacturers
used variations of simple airfoils they already had experience
with. The creation of the database allowed them to take more risks
and make larger leaps when designing new aircraft. Most of the work
NACA did went unnoticed by the public, simply because it wasn't
very glamorous. The public has no real interest in the development
of a reference table for engineers, even though the research on
drag which was part of the program also helped the design of
everyday items, such as the automobile.
     No, the public wasn't interested in the everyday research
which was done by not only NACA but the United States Air Force and
Navy. The average person doesn't know, or really need to know, what
chord is, what an L/D ratio really means, or what exactly why the
triple slotted Fowler flap makes such a difference for the B727. It
is very difficult to tell one airfoil apart from the next and the
public is usually only interested in something it can see,
something that makes a visible change. And one such technology was
the aircraft gas turbine engine, commonly known as the jet engine. 
     The jet engine is actually a fairly old concept. It utilizes
the expansion of a working fluid to propel itself, and whatever it
is attached to, via action and reaction, a rocket works in the same
way. Of course the major difference is that a jet draws its
oxidizer from the surrounding atmosphere. Although it is basically
simple in concept the jet is very complicated in execution. A jet
engine is more efficient at higher operating temperatures and at
higher altitudes. Unfortunately, when it first appeared the
temperatures needed for useful operation were on the edges of the
capabilities of the materials then normally used. Initial
development of the jet took place simultaneously in England and
Germany during World War II. At wars end both sides had made decent
progress in the development of the jet as a useful aircraft
powerplant. Both development projects were funded by the respective
governments. 
     During the war a few of the British jets, designed by Sir
Frank Whittle, were sent to the United States to be studied by
American engine manufacturers. At the time General Electric had a
great deal of experience with turbines used for power generation
and the became involved in the American engine development. The
first jet aircraft to be flown by the United States was the Bell P-
59A Airacomet powered by two GE turbojets developed from the
British engines. General Electric got off to a running start with
the development of jet powerplants and soon their engines were
powering the new fighters of the USAF. Other companies developed
their own designs; Pratt & Whitney, Allison, and Wright were the
major manufacturers. All of the initial development work was funded
by the government, either through NACA or the military. The costs
of experimenting with the new technology was too great for the
manufacturers to cover, and none of the airframe builders wanted to
consider commercial jet aircraft until the engines were proven over
time. In fact, the failure of one of the largest American engine
builders, Wright, was caused by repeated failures within their jet
engine program. They repeatedly failed to meet requirements and the
cost to the corporation through research and development funds was
enough to ruin it financially. Today the two giants of the jet
engine field are General Electric and Pratt & Whitney. There are
other, more specialized corporations, Garrett, Williams, and
Allison for example, which are also leaders in their fields.
     The government, primarily the military, funded the research on
new jet designs which eventually had a direct impact on the
commercial market. New materials were developed, new manufacturing
techniques, and new approaches to design. Originally the
requirements were for powerplants needed for high speed fighters.
These powerplants didn't have much of a public impact, since their
operational conditions were quite different from those of the
airliners of the time. But the basic research needed to develop
these powerplants was very useful later on when the military
decided it needed jet powered bombers too. They had taken to
mounting turbojets on propeller powered aircraft for extra power on
takeoff and when needed for a high speed dash. This was very
inefficient, it was time for the pure jet bomber.
     The first bomber produced for the USAF was the North American
Aviation B-45 Tornado. It was very conventional in design; straight
wing with the engines in the wing. It looked more like a prop
bomber with jets substituted. Other designs followed, the beautiful
Convair XB-46, the ugly Martin XB-48, and the radical Northrop
flying wing YB-49. But the winner was the originally designed
Boeing B-47 Stratojet. The B-47 had most of the features associated
with modern jetliners; a swept-wing, engines pod mounted on
nacelles, and a very streamlined fuselage. The only major
difference was the shoulder mounted wing, whereas most airliners
have a low mounted wing, to keep the wing box clear of the cabin.
The B-47 gave Boeing a vast array of data concerning large, high
speed jet aircraft. This data would become useful later.
     After the overwhelming success of the B-47 the Air Force
wanted a truly long range aircraft. Boeing again won with the B-52
Stratofortress. The B-52 was very much an enlarged, and advanced,
B-47. It shared the same overall design philosophy and it too was
a resounding success. The B-52 also contributed immensely to the
growing database on large jets. Let alone the research
contributions it made as a workhorse.
     The B-52 has been used extensively over the years as a
platform with which to experiment. Much of the early data on low-
level wind shear was gathered by the USAF to help develop its
doctrine of low level penetration. A B-52 was used for most of the
information gathering. In fact the B-52 involved was caught in the
very turbulence it was monitoring and had nearly 90% of the
vertical stabilizer sheared off. Due to the skill of the pilots the
aircraft landed safely and quite a bit of data was obtained from
the harrowing experience. 
     This was a government sponsored program which obtained data
which later proved very useful to commercial airlines in planning
to avoid low level shear, as well as the FAA is designing rules to
help insure safe operation. Wind shear is one of the deadliest and
least understood of the natural phenomena that pilots have to
concern themselves with. Nearly all of the data that has been
gathered to date has been gathered by the government.
     A strong claim could be made that the B-47 and B-52 were the
progenitors of the modern airliner. This is especially true if the
story of the development of the B707, the first US airliner, is
known.
     Both the B-47 and B-52 were equipped for mid-air refueling,
but at the time the USAF's tanker was the Boeing KC-97 propeller
powered cargo aircraft. The KC-97 had evolved from the B-29 of
World War II and it's top speed was barely above the stall speed
for a fully loaded B-47. Boeing saw a requirement for both a new,
jet powered, cargo/tanker aircraft and a new jet airliner. 
     The British were first with the de Havilland Comet, the first
modern jet airliner. However, the Comet had a fatal design flaw.
After several cycles of pressurization the fuselage would burst at
altitude, with tragic results. The problem was traced to weakness
at the corners of the square windows and the Comet was grounded
until a redesign could be done. This delay was long enough to allow
the US manufacturers to jump into the market.
     Boeing had no guarantees that anyone would purchase a jet
powered airliner. They were pinning there hopes on the USAF making
a purchase of tanker aircraft to recoup their costs. At the time
Boeing was the only US corporation with any experience building
large modern jets. The decided to risk the company on a $15 million
dollar gamble. In secret they designed and constructed a prototype.
To help keep the secret it was given the number 367-80, 367 being
the Boeing model number for the KC-97. Therefore it appeared, on
paper, to be another variant of the KC-97. The prototype's design
cast the mould that designers would continue to follow to
generations. Streamlined fuselage, low mounted swept wing, and
engines slung in pylon mounted pods. The Dash-80, as it was called,
used the data Boeing had accumulated over the years in designing
and building the big bombers for the USAF. In fact, the Dash-80
used the Pratt & Whitney JT3 turbojet, which was the civilian
version of the J57 turbojet used on the B-52. The Dash-80 first
flew in 1954, just after the end of the Korean War. At the time
money was tight and the USAF turned down the Boeing model 717, as
production tankers were to be known, in favor of a plan of
converting old B-47s. It looked as if Boeing's future was dim. But
then the USAF changed it's mind and ordered 29 aircraft, thus
saving Boeing from bankruptcy. 
     After the Dash-80 made its public debut, Douglas aircraft,
then the world leader in transport production, realized that Boeing
had made a quantum leap ahead of them. Thus the DC-8 crash
development program began. The resulting aircraft closely resembled
the Dash-80, the major differences being a wider body and a
different wing sweep.
     Boeing was out of the woods, but it still wasn't safe. It was
decided to redesign the Dash-80 with a wider upper fuselage to
allow more seating in order to better compete with the DC-8. In
this form the 707 emerged. Soon after the airlines began ordering
both the 707 and the DC-8. Without the support of the USAF Boeing
wouldn't have been able to enter the civilian airline market, and
there wouldn't have been the pressure on Douglas to match them. The
development of the jet airliner would have undoubtedly taken much
longer, as the only example of the time, the Comet, was seen as a
failure. Without the government funds used to build wind tunnels
and conduct tests used in designing the bombers there wouldn't have
been a database for designers to use. And the jet engines used by
both the 707 and DC-8 were originally developed for the military.
Without their funds for research the advanced engines needed for
the airliners to be successful wouldn't have existed. The B707 went
on to be one of the most successful designs of all time. It was
still in production until a few years ago as the E-3A Sentry AWACS
platform and older airframes served as the basis for US Navy E-6
aircraft and the E-8A J-STARS aircraft used in Desert Storm.
     The culmination of several government programs was the
development of the modern civilian airliner. Most people don't know
the history of the airliners development, let alone the governments
involvement, but if they new perhaps they'd realize how important
that involvement can be. Of course there are areas where
government's involvement is well known, especially research on high
speed flight.
     Nearly everyone is familiar with the X-1 research aircraft and
its breaking the sound barrier. That is the kind of sensational
news that stays in the publics mind. However, most people don't
realize that the purpose of the X-1 wasn't to just break Mach 1,
but to gather data about the phenomena known as the sound barrier.
The X-1 was a joint program involving NACA and the USAF designed to
investigate flight characteristics of aircraft flying transonicly.
There were actually seven X-1s constructed of various designs each
building on the experiences of the earlier designs. The X-1 program
gathered a great deal of data which later went towards future
research programs and the new jet fighters of the time. The later
research programs weren't as highlighted as the X-1, but they were
all important.
     At the same time as the USAF was running the X-1 program the
Navy was running the D-558 program. The D-558-I Skystreak was jet
powered and had no where near the performance of the X-1, however
it had a much greater endurance. The D-558-II Skyrocket initially
used a jet, but it was later converted to rocket power and went on
to contribute a good deal of data on high speed flight. The X-2 was
designed to push the envelope further and gather more data on high
speed flight. The Douglas X-3 Stilleto, although looking very
futuristic, was unproductive. The Westinghouse jet engines
installed never produced enough power and therefore little was
accomplished. 
     The next X-plane of note to venture into the high speed realm
is the North American X-15. The X-15 was designed to fly higher and
faster than any other research aircraft. The X-15 was sponsored by
NACA, the Air Force, and the Navy. During the program NACA became
NASA. The X-15 was an amazingly successful program. Several
technological leaps were made during the program which later
directly affected the space program and the aborted attempt to
develop an American supersonic transport. The X-15 could truly be
called a space plane, indeed, many of the pilots involved with the
program received their astronaut wings. Most of the public know of
the X-15 program because of the height and speed records it set,
and flying to 314,750 feet above sea level and Mach 6.7, or 4,520
miles per hour, are quite incredible, but these figures were
reached during just two out of 199 flights made by the X-15s during
their test program. The list of accomplishments made during the
long X-15 program is long and varied. Most of what is known about
transonic flight came from the X-15. New alloys were developed for
the X-15 which were later used for other programs. Much of the data
obtained by the X-15 is now finding new life as the basis for the
X-30 NASP, National AeroSpace Plane, and the data had a large
impact on both the cancelled Boeing X-20 Dyna-Soar program and the
Space Shuttle.
     The Martin Marietta X-23 and X-24 lifting body test programs
also contributed a great deal to the data we now have on supersonic
and hypersonic flight, as well as having a direct design influence
on the Space Shuttle. These two programs investigated the
properties of using body lift for flight to reduce the wing area
needed for a design. This is also playing a role in the X-30
program. It is interesting to note that the mother aircraft for
both the X-15 and X-24 was a NB-52 operated by NASA. This NB-52 has
also gone on to be the mother aircraft for the new commercial
Pegasus booster developed to launch small satellites into low earth
orbit, and it uses the very same carrying pylon built for the X-15.
This is but one of many subtle ways government programs play a
public role.
     To date the data on high speed flight gathered through so many
programs has had little direct public use. The designers of the
Concorde certainly used the data in their calculations, but so far
the Concorde and the Soviet Tu-144 are the only commercial
supersonic transports, and the Tu-144 was a failure. The American
SST effort was halted due to many reasons. So, what has all this
government spending achieved? Certainly it has played a role in
designing new military aircraft, but those have dubious public
value. The data is playing a large role in the development of the
X-30 NASP, but it remains to be seen if this will have any direct
commercial impact. The main receiver of benefits has been the space
program, which of course is another government program. A great
deal of time has been spent trying to analyze the space program and
its benefits to the public. So far there haven't been any solid
decisions.
     Another of the areas in which the government is supplying most
of the data is in laminar flow airfoils. Currently NASA is flying
the two ex-USAF F-16XL cranked arrow wing prototypes in an
extensive research program on laminar flow. Laminar flow is the
principle of keeping the air flowing over the airfoil directly
against the skin in a smooth stream. This reduces turbulence, and
thereby increases lift and reduces induced drag. Earlier, in 1960,
the USAF had sponsored the Northrop X-21A program. This involved
fitting a new wing and engines to two B-66s. The new wing had
roughly 120 slots on both the upper and lower surfaces through
which small amounts of air were drawn in flight. This has the
effect of removing the normal turbulent layer and increasing
laminar flow. The X-21A program confirmed that boundary layer
control was an effective way to obtain laminar flow, but it was
also uneconomical at the time. With modern manufacturing methods it
is fairly feasible. A few new prototypes have used this technology
and it appears it is only a matter of time until public aircraft
utilize it.
     The boundary layer control wing isn't the only new technology
wing researched by the government, the super-critical wing is
another. The super-critical wing is a design which at first appears
to violate a few accepted laws of wing design. Normally a wing is
cambered such that the underside is relatively flat while the tope
is curved, thereby creating a pressure differential which results
in lift. A super-critical wing has a curved underside and a
relatively flat top, however, due to its specific design is still
produces life. In fact, it also produces less drag than a normal
wing and is thicker in cross section. This allows for more space
for fuel and control actuators. Most of the super-critical wing
research was done by the US government and was first flown on a
converted F-8 Crusader. The super-critical wing allows for more
efficient airliners and therefore reduced operating costs. It is
already in use today on the B757 and B767.
     The government doesn't confine itself to fixed wing
developments either. Most of the modern innovations in rotary wing
flight have come from government sponsored research. One of the
most promising is the Sikorsky XH-59A Advancing Blade Concept, or
ABC, helicopter. A helicopter's forward speed is limited by its
rotors. On the side with the advancing blade the rotors tip
airspeed is its rotational speed plus the helicopter's forward
speed. On the opposite side it is the rotor's rotational speed
minus the helicopter's forward speed. So, at high speeds the
advancing tip can reach supersonic speeds while the retreating tip
can fall below stall speed. This of course causes a range of
problems; high vibration levels, imbalanced lift, and high wear on
the rotors amongst them. The ABC helicopter uses twin rotors
mounted co-axially, but closer than most, such as the Soviet Kamov
designs. This way there is an advancing and a retreating rotor on
both sides. At high speeds the rotational speeds can be reduced and
the retreating blades allowed to operate near stall with the
advancing blades providing all of the lift. The test program has
been successful and the technology is ready for public use. It is
just waiting to be put to use.
     The next step in advanced rotor craft is the X-wing design.
The X-wing defeats the problems of high speed flight by stopping
the rotor and locking it into an 'X' configuration. The rotor is
symmetrical and has a small slit along both edges. The symmetrical
blades are turned into airfoils by blowing high pressure air out of
the slit on the trailing edge and utilizing the Coanda effect to
deflect the airstream and thereby produce lift. The Sikorsky RSRA
(Rotor Systems Research Aircraft) was modified in 1985 to use and
X-wing rotor system and it has been testing since then. To date
there are still bugs to be worked out but eventually the X-wing
technology could be used for sleek efficient short haul passenger
aircraft. Take off vertically from a heliport, fly as fast as a
fixed wing aircraft, and land vertically. This is a capability only
available currently from one other technology, the tilt-rotor.
     The tilt-rotor concept has been investigated extensively in
the past. With the tilt-rotor the rotors are mounted outboard and
either the entire engine/rotor assembly, or just the rotors, are
rotated to provide either lift, thrust, or a mix of both. In the
closely related tilt-wing technology the engines/rotors are fixed
to the wing and the entire wing tilts. Both seem to offer the best
of both helicopters and fixed wing aircraft. Unfortunately both
also offer the worst of both worlds in the process. The technology
has been developed for many years. The Hiller X-18 was one of the
first prototypes to be completed. The X-18 was a tilt-wing design
with a set of contra-rotating props on each wing. The X-18 was only
mildly successful. The Curtiss-Wright X-19 was a tilt-rotor design
using four rotating engine/rotor combinations one on each end of
two stub wings. The X-19 was fairly successful and it demonstrated
the feasibility of a tilt-rotor system. It actually had better
hovering characteristics than most helicopters of the day. But it
was also fairly complicated mechanically and it never reached the
public. The Bell Aerospace Textron X-22A was actually very
successful and the remaining prototype was flight worthy as of
1988. Experience with this aircraft certainly gave Bell, already a
leader with helicopters, an edge with tilt-rotors. The X-22A is
similar in arrangement to the X-19, however it uses four ducted
propulsors with fuselage mounted engines. The X-22A benefitted from
Bell's earlier experience with the XV-3 tilt-rotor which was
sponsored by the military.
     After the success of the X-22 Bell created the XV-15. The XV-
15 is a fully modern tilt-rotor. Its turbines and rotors are pod
mounted at the wing tips and rotate as a unit for vertical flight.
The XV-15s built are still flying and have served both the military
and NASA extensively in test programs. The XV-15 is the direct
ancestor of the Bell-Boeing V-22 Osprey which is currently
undergoing testing for the military. The Osprey looks, in fact,
like an enlarged XV-15. It uses the same beaver tail design and the
same dual vertical stabilizer layout. The Osprey is scheduled to
enter military service in the mid-ninetys and so far it is passing
its test with flying colors.
     Bell-Boeing plan to produce a commercial version of the Osprey
for commuter use. The tilt-rotor offers many advantages, chief
amongst them being able to operate from the center of a city and
shuttling passengers to a larger airfield. If everything goes as
smoothly as it has so far there should be public Ospreys operating
within this decade. And nearly all the research and development
costs have been payed by the government. And this is for a new
design. Many, if not most, of the current group of helicopters in
use were originally developed for the military. The Huey was
designed for the Army and is now used extensively by civilian
operators, as was the Jet Ranger, the Chinook, and many others.
Nearly of the large helicopters used today to carry cargo or
passengers were originally designed for military use, in fact some
were formerly owned by the military. The helicopter has definitely
benefited the public, and most of the development work on
helicopters was payed for by the government.
     The latest development in helicopters to actually reach the
public is the NOTAR system developed by McDonnell-Douglas'
helicopter division. NOTAR stands for NO TAil Rotor. In the NOTAR
system the tail rotor is dispensed with totally. The tail rotors
job of counter-acting the torque of the main rotor is taken over by
a specially designed tailboom. The tailboom is tubular with a small
slit along one side. A fan at the base of the tailboom compresses
the air in the boom, blowing it out of the slit. The Coanda effect
then acts in cooperation with the downwash of the main rotor to
create a side ways lift force to balance out the torque. Yaw
control is achieved via louvers on the end of the boom with vent
the compress air.
     Since most helicopter accidents are related to problems with
the tail rotor, ground strikes, failure, and unaware ground
personnel, NOTAR increases the safety factor of normal operations.
And as a bonus NOTAR reduces noise levels and increases agility.
NOTAR is available on some of McD-D newer helicopters and it is
spreading. NOTAR was funded in part by the government, which is
interested in NOTAR because it increases the battlefield
survivability of a helicopter.
     As mentioned earlier, the government played a large role in
early jet engine development. However, as of late the civilian
market has been supplying the demand for new designs on its own.
And many new innovations came from the industry. But some of the
latest technologies have again been funded by the government. As it
was stated before, jets operate better at high temperatures. The
military has been interested in high performance jets for their
fighters for some time now. The ATF program called for engines
capable of supercruise, sustained supersonic slight without
afterburner, and a lower fuel consumption than current engines. The
demands were met. Pratt & Whitney's F119 beat General Electric's
F120 for the contract, but development of both engines will benefit
the civilian market. Both corporations developed new materials and
new design techniques as part of the program. Powdered metallurgy
and single crystal turbine blade technology was pushed to new
limits designing the new engines. This technological push can now
be applied to new civilian engines. GE has unveiled its new
civilian turbofan, the GE90, which produces 90,000 pounds of
thrust. By comparison the current engines on an average B747
produce 56,000 pounds of thrust each. These new engines will be
able to power the jumbo jets of tomorrow on incredibly long flight
routes. All at a lower specific fuel consumption. And much of the
R&D which went into their design was originally funded by the
government.
     As these few examples have shown, the government plays a major
part in aerospace research and development. Perhaps it isn't as
direct a role as in some other countries, where governments have
paid for development of a commercial aircraft, but it is still a
strong role. These were just a few of the plethora of examples that
exist. There are many direct spinoffs, but direct spinoffs have a
limited use, while these contributions, in research and basic data,
are much farther reaching. The databases which have been created by
government research will remain useful for generations to come.
Basic knowledge doesn't have a limited useful life. Most of these
programs were to big, or too expensive for a corporation to run
themselves. Without the government to fund these programs they most
likely would never have taken place, and therefore we wouldn't have
the information we have today. The government will continue to have
a role in research and development for the foreseeable future.   

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     Gunston, Bill & Spick, Mike, Modern Air Combat, (Cresent
Books: New York, 1983)   

     Miller, Jay, The X-Planes, (Aerofax: Arlington, Texas, 1988)
     
     Mondey, David, The International Encyclopedia of Aviation,
(Cresent Books: New York, 1988)

     Oakes, Claudia M., Aircraft of the National Air and Space
Museum, (Smithsonian Institution Press: Washington, D.C., 1981)

     Richardson, Doug, Stealth, (Orion Books: New York, 1989)

     Sweetman, Bill, High Speed Flight, (Jane's Publishing Inc.:
New York, 1983)

     Sweetman, Bill; Gething, Michael J.; Richardson, Doug; Spick,
Mike; & Gunston, Bill, The Great Book of Modern Warplanes,
(Portland House: New York, 1987)

     Taylor, Michael J.H., Jet Warplanes, (Bison Books: Greenwich,
Connecticut, 1983)

     Taylor, Michael J.H., Modern Combat and Commercial Aircraft,
(Exeter Books: New York, 1984)

     I would also like to give credit to the Internet. Especially
the newsgroups sci.aeronautics, sci.military, and the skunk-works
mailing list.  

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