The Northrop Flying Wing
and the B2 bomber
A design as aeronautically clean as the Flying Wing
has a big advantage over conventional aircraft design. This
advantage is that drag has been reduced to a minimum. And as a
result of this minimum drag, the performance of the Flying Wing is
unequalled in speed, range and operating economy.
For many years airplane designers have realized that by reducing
drag -- the drag caused by the shape or form of an aircraft -- its
performance could be greatly increased. Early steps in this
direction were changes from biplane to monoplane design; the
elimination of external wing struts and flying wires; and the
incorporation of retractable landing gears. However, in spite of
all these advancements, the average conventional airplane of today
still has two to four times the drag of a flying wing. So in order
to reduce drag to its absolute minimum, aircraft designers took
the drastic step of eliminating the fuselage and tail and putting
the pilot, the power plant and payload in the wing envelope.
The chief exponent of Flying Wing design in the United States was
John K. Northrop. John Northrop was born in Newark, New Jersey in
1895. When he was nine years old his family moved to Santa
Barbara, California. His great interest in mechanics curtailed his
formal education, and, after brief periods as garage mechanic,
carpenter and draftsman, he went to work in 1916 for the Loughead
Brothers, who were then engaged in building twin-engine flying
boats in Santa Barbara. Except for a stint with the Army Signal
Corps during World War I, Northrop stayed with the Lougheads until
1923. In that year, he joined the Douglas Aircraft Company, which
was then preparing the famous Around-the-World Cruisers. He stayed
for four years working as draftsman, designer and project engineer
on many early Douglas planes.
In January, 1927, John Northrop and three other men
formed the Lockheed Aircraft Company. It was at this time that he
designed the famous Lockheed Vega — a high wing, cantilever
monocoque airplane which was far ahead of its time in design. It
was widely used by many of the top flyers such as Amelia Earheart,
G. Hubert Wilkins, Frank Hawks, and the noted Wiley Post. Many
speed records were set by the Lockheed Vega aircraft.
In the summer of 1928, John Northrop began his research of flying
wing aircraft. He formed a small engineering group known as the
Avion Company. He built and test flew one of the first 2mi-flying
wing aircraft in the country. Although it did carry the pilot and
engine power plant in the wing, it was not a true flying wing
because of its small tail carried on twin booms. This plane made
numerous flights in 1929 and 1930 and recorded much valuable
research data. Unfortunately, the depression of the early 1930’s
caused further research to be abandoned.
As years passed and further advancements were made,
John Northrop became recognized as the genius behind the Flying
Wing design and the leading exponent of flying wing design in the
United States. In Germany the flying-wing-design concept
advantages were also shared by Alexander Lippisch and the Horton
Brothers and in England by Hill. All were designers, who built and
flew successful Flying Wing aircraft. Because it had no fuselage,
even the Wright Bi-plane can be considered in this category in
spite of its multiplicity of wing struts and wires. The Wrights’s
plane carried the power plant and pilot directly on the wing
system and was controlled longitudinally by a front elevator which
was, in fact, a lifting wing surface.
In 1923 John Northrop became interested in the flying wing design
after a discussion with Tony Stadlman, who had worked with
Northrop in 1917 at the Lockheed factory, then located in Santa
Barbara. Stadlman was plant manager of the Douglas Company in Los
Angeles at this time and young Northrop was an engineer. Stadlman
believed the ideal aircraft of the future was in the true “flying
wing” design. From that day on John Northrop’s goal was to design
and perfect the Flying Wing.
During the early stages of design development, Northrop held
discussions with the late Dr. Theodore von Karman of the
California Institute of Technology. Northrop later hired Karman’s
assistant, Dr. William Sears, to become his Chief Aerodynamicist.
Walt Cerny, who came to work for Northrop in 1929, was made
assistant Chief of Design. These men had direct supervision of the
Flying Wing from its inception. The encouragement and assistance
of these men, plus the enthusiastic collaboration of the many
Northrop employees, enabled this amazing design to become a
The pressure of designing and building conventional aircraft
prevented complete concentration on the solution of the Flying
Wing design, and it was not until later that they were able to
focus their efforts on Northrop’s dream of a true flying wing.
Northrop’s first semi-flying wing plane was flown in 1928. It did
make use of external control surfaces and carried outrigger twin
booms -- quite a radical aircraft for its time. The fuselage was
completely eliminated, and the pilot was housed in the wing along
with the power plant.
The big problem overcome in designing the flying
wing revolved around the buried engine concept. The entire engine
propeller shaft had to be buried within the wing foil. This
increased the problems of cooling the engine and of turning the
long drive shaft to the propellers.
The dimensions of the first Northrop semi-flying wing were: It had
a wing span of 30 feet, 6 inches, its length was 20 feet, and its
overall height was five feet. Wing area was 184 square feet and
aspect ratio was 5.12 to 1. Landing gear was of the tricycle type
with the main wheels forward and a tread of 9 feet between the
main wheels. Power was supplied by a single four-cylinder 90
horsepower Menasco engine for the tractor powered version. This
aircraft later was powered by a Cirrus Engine when it was rebuilt
as a pusher-design aircraft.
In July, 1939, John Northrop began engineering tests for a new
flying wing design. This design was known as the N1M “Jeep”. The
first flight tests were conducted at Muroc Dry Lake in July 1940.
Test pilot for the first flight was Vance Breese. Early tests
showed the plane to be satisfactory in stability and control.
Shortly thereafter, the flight test program was turned over to Mr.
Moye W. Stephens, Northrop Test Pilot and Secretary to the
Northrop Corporation. During 1940 and 1941, over 200 flights were
made in this aircraft to gather further data. Control of the
aircraft was achieved through the use of a system of elevons and
wing tip rudders. The elevons served in tailless type aircraft
both as elevators and ailerons. Rudder action was provided by
control surfaces incorporated in the drooping wing tips.
This wing had a wing span of 38 feet and a length of 17 feet, an
overall height of 5 feet, a wing area of 300 square feet, and an
aspect ratio was 4.75 to 1. It, too, had a tricycle landing gear.
It originally carried two four-cylinder Lycoming engines of 65
horsepower each, which were later replaced by two six-cylinder
Franklin air-cooled engines of 120 horsepower each. The drooping
wing tips of the N1M were later eliminated.
The Ni M “Jeep” was truly the first American flying
wing aircraft. Today it resides in the National Air and Space
Museum Storage facility at Silver Hill, Maryland, a short distance
outside of Washington, D. C. It is hoped that this aircraft is one
that will be displayed in the new Air and Space Building when it
is completed on the Mall in Washington, D.C.
XB-35 Flying Wing
The XB-35 was the first in a series of large Flying
Wing Bombers. It was a bombardment type aircraft of exceptionally
long range and heavy load capacity. Two XB-35 and 13 YB-35’s were
initially scheduled to be built under Army contracts. But only six
of the big wing bombers were completed and test flown. The XB-35
had a wing span of 172 feet and a wing area of 4,000 square feet.
It was capable of operating under overloading conditions at a
gross weight of 209,000 pounds or 104.5 tons.
Prior to the XB-35 design, Northrop had flown twelve tailless
aircraft designs since the company was founded. Northrop engineers
learned much about these experimental models and had made hundreds
of additional models for wing tunnel tests. For the first time in
the history of military aeronautics, the flying wing contributed
many advancements to military design in the bombardment category.
Five of the leading advantages were:
1. The low drag, high lift feature of the Flying Wing meant that
in practice the XB-35 could transport any weight faster, farther
and cheaper than an aircraft of conventional design.
2. The simplicity of construction of the XB-35 Flying Wing
presented few structural complications. It cost less to build
since it was built as a single unit in which the structure
extended through from tip to tip with no added tail or fuselage to
3. It had better weight distribution. Compartments along the span
could distribute the bomb load and weight more evenly over the
wing surface which supported it. This also would have applied to
cargo if a cargo version had been built. It eliminates the need
for excessive structural weight such as is necessary in
conventional bombers where the weight is concentrated in the
fuselage and must be distributed over the wing from this point
through the use of heavy structural members.
4. For ease in loading and unloading, cargo could be placed in
span wise compartments where any part of the plane’s load was
easily accessible through its own cargo or bomb bay doors. This
provided direct access to all portions of the cargo.
5. The XB-35 for military purposes presented a smaller target
while engaged in either offensive or defensive operations.
Comparisons between the Flying Wing and conventional aircraft is
also illustrated by performance figures obtained from Northrop and
backed by many years of research tests in which planes identical
in scale to the XB-35 were used. The XB-35 was built to be 20
percent faster than conventional bomber aircraft with identical
loads and horsepower. Normal crew for the XB-35 was nine men --a
pilot, co-pilot, bombardier, navigator, engineer, radio operator,
and three gunners.
Cabin space was available for six more crew
members, who could substitute on long-range missions. Folding
bunks were built in the XB-35 to accommodate the off-duty crewmen.
These fifteen men were housed entirely within the wing foil
itself. The XB-35 was built of a new aluminium developed by
the Alcoa Company. Tests showed this material to be considerably
stronger than previous metals used. Gasoline was carried in bullet
proof, leak proof fuel cells within the wing of the XB-35 and
additional range was built in by the addition of additional fuel
tanks in the bomb bay and other wing compartment areas. The wing
section of the XB-35 was 37-1/2 feet long at the centre,
tapering to slightly more than nine feet at the wing tips. It
swept back from centre to tips making the overall length of the
ship slightly more than 53 feet. The XB-35 stood over 20 feet tall
when at rest on its tricycle landing gear. It was equipped with
5’6” dual wheels on the main gear and a 4’8” wheel on the nose
The XB-35 received its initial start from the Army Air Corps in
September, 1941, following a visit by Assistant Secretary of War
Robert Leavitt, General H. H. Arnold, and Major General Oliver P.
Echols. At this time, Northrop submitted a preliminary design for
the XB-35 to Wright Field. Army officials were more than satisfied
because they awarded a contract for the altitude performance with
a pressurized cabin for the crew and a more than adequate bomb
load. There would not have been an XB-35 Flying Wing Bomber had it
not been for the enthusiasm and foresightedness of men like John
Northrop, General Arnold, General Echols, and Mr. Leavitt.
In November, 1941, two XB-35 prototypes were ordered by the Army
Air Force. Preliminary design work began on the XB-35 early in
1942, and on July 5th of that year the mock-up Board from Wright
Field inspected a full size wood mock-up of the centre section and
a portion of the left wing. Official approval was given. Northrop
built a new bomber plant at the end of the company’s grounds in
Hawthorne, California. This plant was completed in January, 1943
and fabrication of the parts for the first XB35 were begun. The
complexities of design in building the B-35 represented an
operation of major size. The Martin Company played a very
important role by providing wind tunnel and other research data
for the XB-35 design. To provide flight test data, Northrop built
four, sixty foot wing span N9M Flying Wings. While the XB-35 was
taking shape in the Hawthorne factory, thousands of test flights
were run on the N9Ms to gather data which could be worked into the
XB-35 design. This time-saving device enabled Northrop engineers
to cut development time from the XB-35. Over the next three years
flight tests were conducted at Muroc Army Air Base to gather data
while the XB- 35 was taking shape.
A X8-35 is shown in flight over Muroc Dry
Eight four-bladed counter rotation propellers drove the Flying
Wing through the air.
This view clearly shows the turret blisters on the upper portion
of the wing envelope.
The XB-35 used elevons which were
installed on the trailing edges with landing flaps, trim flaps and
rudders. The elevon was a Northrop invention in which the function
of both elevators and ailerons were combined. Further control was
achieved by wing slots. The XB-35 was first flight tested during
the summer of 1946 by Northrop’s Chief Pilot, Max Stanley. One
YB-35 was slated to be turned over the the Navy and was to be
designated XB2T-1; however, this did not take place. The Navy was
to have flown and tested the aircraft for research purposes, but
this project was cancelled.
After the prototype XB-35 models were built at the Hawthorne
plant, a war time plan was begun to build 200 B-35 Flying Wing
bombers by Martin Aircraft Corporation at Omaha, Nebraska. Martin
had previously built B-29 bombers, and it was expected that these
would be phased out - in favour of the B-35 Flying Wing
Bombers. This program was dropped, however, with the conclusion of
World War II. The first XB-35 flew on June 25, 1946. The power
plants of the XB-35 were Pratt-Whitney “Wasp Major” engines. It
had two B-4360-17 and two R-4360-21 engines of 3,000 horsepower
each with double turbo super chargers and eight coaxial counter
rotating - four bladed Hamilton Standard pusher propellers. Tests
were also run on three-bladed propellers, but the four- bladed
models proved to be the most efficient. The aircraft was designed
so that other types of engines could be adapted as they were made
The XB-35 was to have carried twenty 50
calibre machine guns, but these were not installed on the number
one prototype XB-35. Seven remote-control gun turrets were aimed
from central firing sighting stations behind the pilot and on top
of the cone protruding from the trailing edge. Four gun turrets
were fitted above and below the centre section. Two gun turrets
were visible outboard of the engines -- one on top and one below.
Four guns were to have been placed in the tail cone. The first two
XB-35 and sole YB-35 Flying Wings had “Wasp Major” engines. But on
June 1, 1945, orders were issued to have the next two finished
with Allison J-35-A-5 jet engines. These models were known as
YB-49 jet Flying Wing Bombers. On June 25, 1945, American Aviation
took a bold step into the future. On this date the world’s first
all Flying Wing Bomber took to the air from Northrop Field at
Hawthorne, California. The crew for this first flight were pilot,
Max Stanley and Dale Schroeder, flight engineer.
Following the flight of the first XB-35, (SIN
42-13603), a second prototype XB-35 first flew in November of
1946. The second prototype XB-35, (S/N 42-38323) soon joined her
sister ship on the ramp at Muroc Army Air Base. When the XB-35 was
completed and had made its maiden flight, further tests were
conducted to prove the feasibility of the design. The two
Pratt-Whitney R-4360-21 Wasp Major engines drove the inboard
contra-rotating propellers and the two R-4360-17’s turned the
outer pair of propellers. Each engine developed 3,000 horsepower.
The metal housing over the propeller shafts offered enough area to
counter-act any yawing tendency of the Flying Wing design, and
counter rotating propellers gave additional stability by
eliminating torque problems. Cooling air for the radial engines
were ducted from openings in the leading edge of the wing. The
XB-35 had a maximum speed of 395 miles per hour and a cruising
speed of 183 miles per hour.
this is a rare photo of nine
Northrop Flying Wing Bombers.
Many people do not realize that more than one or two prototypes
were built of this design.
Here, for the first time, is actual proof of their existence.
Two of the big wing bombers are undergoing modifications from
XB-35’s to Flying Wing B-49 1t Bombers.
The entire project was later cancelled by the Air Force.
YB-49 and YRB-49A
With the introduction of the YB-49 to flight status in the fall of
1947, it was anticipated that this model would prove to be the
most successful flying wing aircraft. A contract ordering the
conversion of two YB-35 Flying Wings was issued on June 1, 1945.
This specification called for the installation of eight Allison
J-35-A-5 turbo jet engines of 4,000 pounds thrust each. The
YB-49 Flying Wing weighted 88,100 pounds when it was rolled out of
the factory. The normal loaded weight was 205,000 pounds. This
could be boosted to 213,000 pounds if necessary. The first flight
was made on the number one prototype YB-49 on October 1, 1947.
This aircraft, S/N 42-102367, was successfully flown from
Hawthorne, California to Muroc Air Force Base by Northrop’s Chief
Test Pilot, Max Stanley. Subsequent test flights pushed the plane
to a top speed of 520 miles per hour and placed the ceiling
surface at 42,000 feet. It held fuel capacity of 17,545 gallons
and had a range of 4,450 miles. The YB-49 Flying Wing jet bomber
was capable of carrying over 36,760 pounds of bombs for a distance
of 1,150 miles. A normal 10,000 pound load could be carried for an
estimated 4,000 miles on 6,700 gallons of fuel. This was less than
half the range of the B-35. This was due to the great quantity of
fuel required by the turbo jet engines; however, a 100 mile
increase in speed was gained in the YB-49.
Over twenty months of research and flight testing was conducted on
the two YB-49 prototypes at Muroc Air Field. During this time,
payload tests and endurance records were broken. Contracts were
placed for thirty RB-49’s and for converting the remaining ten
B-35 airframes to YRB-49A strategic reconnaissance type aircraft.
During two years of flight testing, stability problems encountered
in the YB-49 design had not been overcome and further tests were
planned. A new autopilot was to be designed and built into the
aircraft. Before this could be done, the first prototype crashed:
On the morning of June 5, 1947, Captain Glenn
Edwards, a test pilot at Muroc Air Force Base, was command pilot
on the number one prototype YB-49. The aircraft had several
stability tests which had to be completed before this aircraft was
placed in quantity production. Scheduled stability tests were
conducted this day at 40,000 feet at a location just north of
Muroc Dry Lake. Captain Edwards radioed to base after his tests
were completed; they were dropping down to 15,000 feet. The pilot
was not heard from again. Witnesses said they saw it tumbling down
out of control just north of Highway 58 and crash. Captain Edwards
and the entire crew were killed. What exactly happened is not
known. The clean all wing design of the YB-49 enabled the aircraft
to reach very high speeds. In descending from high altitudes, the
YB-49 could easily surpass “red line” (not to exceed) air speed.
It is assumed that Captain Edwards was attempting to investigate
the stall characteristics of the aircraft, and the “not to exceed”
limits of the aircraft were exceeded while descending from 40,000
feet. In exceeding these limits, the outer wing panels were shed
and the aircraft tumbled in three pieces to the ground.
The second prototype YB-49, (S/N 42-1 02368),
was burned and destroyed during a ground taxiing
accident at Edwards Air Force Base. The YB-49 crash site can still
be seen today. Located ten miles north
of the city of Mojave and just east of Highway 14, the scorched
earth and a few bits of plastic and metal
are all that remain as a monument to this amazing design. This
crash rang the death knell for the
YB-49 Flying Wing program. Muroc Air Base was later named in honour
of Captain Glenn Edwards.
Today it is known as Edwards Air Force Base, Flight Test Centre of
the United States Air Force.
Only two YB-49’s were completed and test flown. It had a load
factor of two and a top speed of
520 miles per hour and a service ceiling of 42,000 feet. The YB-49
had eight Allison J-35-A-5
turbo jet engines. These were located in banks of four at either
side of the wing, and the only
protuberances were the exhaust along the trailing edge. Air
intakes were mounted in the leading
edge of the wing. All gun turrets, except for the tail cone guns,
were eliminated. Four vertical
stabilizing fins were fitted. The regular crew of seven were
housed entirely within the seven foot
thick wing centre section. The pilot was located in a plastic
bubble canopy near the leading edge
for excellent visibility. For long flights provision was made for
an off-duty crew of six members
who had quarters in the tail cone just aft of the flight section.
One YB-49 averaged 511 miles
per hour during a 2,258 mile flight from Muroc, California to
Washington, D. C. Flights of over
nine hours duration had been recorded.
These performances give
support to the flying wing
design. At its time it was one of the world’s longest ranging jet
Flying scenes of the YB-49 aircraft were featured in a Hollywood
film based upon H. G. Wells’
“War of the Worlds”. If one is privileged in viewing this on a
late show on television, you will see
an extraordinary art form of flying, banking, rolling and turning
as graceful as any plane that flew.
Watching the Flying Wing fly and perform in colour is an experience
not easily forgotten. This
author had the privilege of viewing the YB-49 flying at March
Field near Riverside, California in
May, 1947. Its grace and beauty in the air will always be a sight
to be remembered, but what
impressed most was its ability to turn inside the top Air Force
Fighter of the day -- the
P-80 “Shooting Star”.
The second prototype YB-49, S/N 42-102368, was burned and
destroyed during a ground taxiing accident at Edwards Air Force
Base. This left the YRB-49A, a strategic reconnaissance aircraft
as the sole remaining Flying Wing. This photo reconnaissance
aircraft had four 5,000 pound thrust Allison J-35-A-19 engines in
the wing and two more suspended in pods below the wing.
Photographic equipment was installed in the tail cone bay just
below the centre section. It had an empty weight of 88,500 pounds
and a gross weight of 117,500 pounds and a maximum gross weight of
206,000 pounds. It had a top speed of better than 550 miles per
hour and it was the same dimensions as the YB-49.
The clean lines of this flying wing was broken by two engine pods
suspended below the wing leading edge to carry two Allison J-35
turbo jet engines. The YRB-49-A first took to the air on May 4,
1950. Tests were conducted at Edwards Air Force Base for a period
of time, but stability tests in the program hampered further
production. Plans were made to install a stabilizing device made
by Minneapolis Honeywell to overcome stability problems. This was
the same type of device installed in the B-47 Stratojet Bomber for
stability guidance. The YRB-49A was designed as a fully
operational photo reconnaissance plane. It had useful loads and
better performance in speed and range than the YB-49. In early
1952, the huge flying wing was flown to Ontario International
Airport to the Northrop facility where the installation of this
stability device was to be installed. Funding for this project was
dropped, however, by the Air Force, and the aircraft remained in
dead storage for a period of time.
In October, 1953, the Air Force ordered the YRB-49A
to be scrapped. Crews were sent from nearby Norton Air Force Base
to complete the salvage project. The aircraft was towed from the
Northrop facility at the southeast end of the field to a site
adjacent to the Air National Guard area where it was dismantled
and cut up for scrap. The huge ship had been sitting in the grape
vineyards weathering the onslaught of dust, wind, rain and sun for
some time. One major Los Angeles newspaper stated: “It is hard to
believe we have scrapped a design which is as modern as the planes
today. Perhaps we will have to wait twenty years or longer before
we find out the true significance of our mistake.” True, the wing
did have its share of problems; however, with adequate funding,
these problems could have been worked out to prove that the wing
did hold a place with the Air Force.
The Flying Wing was years ahead of its time, but it
was caught in a budget squeeze between the faster B-47 Stratojets
and the long-range B-36 intercontinental bombers. Politics also
played an important part in the defeat of the B-49 Flying Wing.
The YRB-49A had a top speed of 512 miles per hour at 40,000 feet.
It had a range of 3,500 miles
non stop without aerial refuelling.
A comment must be made on the B-49 design competition: During this
period, 1948 - 1952, a former Northrop competitor employee became
Secretary of Defence under President Truman’s administration.
Being a former officer of a competing firm to Northrop, some
significance in the Air Force’s selection of the B-36 over the
B-49 should be noted. One day a high government official was sent
from Washington to visit John Northrop. A meeting took place
whereby John Northrop was told that his B-49 Flying Wing Bomber
would be produced for the Air Force; however, it had to be built
by Convair in Fort Worth, Texas or the Air Force would not buy his
Flying Wing design. John Northrop replied that he and his
employees had built the Northrop Company and organization over the
years and he owed a debt of loyalty to his employees. He stated
that if the aircraft was to be built at all it would be built by
his people at the Northrop factory in Hawthorne, California. The
rest is history. The Air Force ordered the B-36. The significance
of this fact should be made clear to future generations
investigating the story of the Northrop Flying Wing.
Northrop-Grumman B-2 Spirit "stealth bomber."
B-2 is a multi-role advanced technology bomber with stealth
characteristics. The B-2's low observable, or stealth,
characteristics give it the ability to penetrate an enemy's most
sophisticated defences. This low observability allows it to fly
more flexible routes at higher altitudes, thus increasing its
range and providing a better field of view for the crew and the
aircraft's sensors. The low observability traits of the B-2
include greatly reduced infrared, acoustic, electromagnetic,
visual and radar signatures. These signatures make it extremely
difficult for even the most sophisticated defensive systems to
detect, track and engage the bomber. Many aspects of the stealth
feature remain classified. However, the B-2's composite materials,
special coatings and flying wing design all contribute to its
stealth. The first B-2 rolled out of its hangar at Air Force Plant
42, Palmdale, Calif., in November 1988. Its first flight was July
The most famous flying wing was the only successful one, the
Northrop-Grumman B-2 Spirit "stealth bomber." It was first started
by the Northrop Corporation in the late 1970s (the contract was
awarded in 1981; its first flight took place in 1989) but did not
become fully operational until a decade and a half later due to
its complexity and numerous initial problems.
The B-2 was an example of modern
technology finally catching up with an earlier idea. By the 1970s,
aircraft designers were deliberately developing airplanes like the
F-16 that were unstable in flight, and therefore inherently
manoeuvrable, controlling them in flight by sophisticated modern
computer control systems. Computer control systems now also made
it possible to control the unstable flying wing design.
The flying wing still offered
excellent performance and fuel efficiency advantages. But
Northrop's designers also chose a flying wing configuration
because it offered advantages for stealth; a vertical tail such as
found in a conventional aircraft reflects radar energy.
Eliminating it increased the aircraft's stealthiness, particularly
from the side. The B-2 is capable of carrying as many bombs inside
it as the larger B-52 and flying just as far. Although only 21 of
these planes are in service, they played a major role in the 1999
bombing of Yugoslavia, which had a sophisticated air defence
system, and are generally regarded as an amazing technological
achievement, albeit a very expensive one.