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British flying
wings
by E.T. Wooldridge
 In the
best tradition of Dunne and Hill, British interest in the tailless
aircraft concept also persisted throughout the Second World War, and was
evident in the designs of Handley Page, Armstrong Whitworth, General
Aircraft Ltd., and de Havilland. A rather undistinguished model of the
period, with a decidedly chequered service life, was the Handley Page
Manx. Dr. Gustav V. Lachman designed a craft which, like its feline
namesake, bore only the vestige of a tail, a single vertical fin on the
rear of the centrally mounted fuselage. Wing-tip vertical fins and
rudders, two pusher in-line engines, slats, elevons, and split flaps,
completed the configuration. The airplane was delivered for testing in
1939, but it was found to be 3300 pounds overweight. Its weight was
reduced and the joints of the main spar were partially reworked because of
deterioration of the glue. Taxi tests in 1942 resulted in damage to the
nose gear. Repairs and further modifications to the basic design ensued.
There were several unsuccessful attempts to fly; on one occasion, the
aircraft hit a bump on the runway and rose to a height of 12 feet.
The Manx was typical of many ill-fated tailless aircraft projects
undertaken by most of-the participants of World War 2. Built in
Great Britain by Handley Page Ltd., the Manx featured two pusher in-line
engines, wing tip vertical fins and rudders, and a vertical fin on the aft
fuselage for stability. Taxi tests began in February 1940, and the test
program stretched on with frequent interruptions until termination in 1946
after about 17 hours of flight.
Finally, the Manx flew what could be called its maiden
flight on June 11, 1943. It was an inauspicious beginning; the pilot
aborted the flight after ten minutes due to a lost canopy. The flight was
symptomatic of a test program that was plagued by fits and starts,
accumulating about 17 hours flight time in some 30 flights. The airplane
was eventually scrapped in 1952, due to fading interest in the concept
following the extended development program.
A slightly more orthodox approach to tailless aircraft
was taken by General Aircraft Ltd., which had been interested in the
development of tailless aircraft since 1934. During the war, the company,
which merged with Blackburn Aircraft, Ltd. in 1949, planned to build four
tailless gliders having differing planforms with various degrees of
backward sweep; all wings had common attachment points for anchorage on a
standard nacelle. Designed from 1943 to 1947, three were built under the
designation of G.A.L. 56. The fourth of the series, designated G.A.L. 61,
more closely approached the all-wing concept in that it was equipped with
retractable landing gear and, in the absence of fins and rudders,
directional control was achieved by drag rudders. The only appendage was a
small pilot's canopy.
Representative of the G.A.L. 56 gliders was this G.A.L. 56/03 Maximum V,
with 36.4 degrees wing sweepback and nose flaps. The wing/fuselage
attachment of the G.A.L. 56 incorporated a device whereby wing dihedral
could be adjusted on the ground. Two sets of split flaps were fitted, one
set hinged at the 50 percent chord line and the rear set at 70 percent
chord. Only one set could be used at a time, the changeover being effected
on the ground.
Captain Eric M. Brown, R.N. (retired), former Chief
Naval Test Pilot at the Royal Aircraft Establishment, Farnborough,
England, flew over 480 different types of aircraft during a brilliant
career. The G.A.L. 56 did not rank at the top of his list of aircraft that
were pleasurable to fly:-
"It was one plane in which I found I could not relax
for a second, beginning right away with takeoff. You could not lift it off
the ground through the slipstream of the towing aircraft before the latter
was airborne, which was the normal method, because as soon as it was clear
of the ground effect-tile cushion of air between wing tip and ground, the
centre of pressure suddenly shifted and the machine dived straight back
into the ground, to bounce on it's very springy undercarriage wildly
across the airstrip. And it had the most incredible stalling
characteristics. When you eased the nose up to slow the speed down, the
plane suddenly took charge and continued to rear nose up until it was in a
tail slide. Even pushing the stick right on to the dash made no
difference. Then suddenly the stick movement would take effect and you
would be pitched forward to fall almost vertically. General Aircraft
decided to investigate this awful phenomenon after we had finished our
tests. Their chief test pilot, glider expert Robert Kronfeld, went into a
spin and was killed. The stalling characteristics also made landing very
tricky."
Another variation on the standard theme was a proposal
by the renowned G.T.R. Hill, who had designed the Pterodactyl. While
serving as British Scientific Liaison Officer at the National Research
Council (NRC) in Canada in the mid-1940s, Hill proposed a research glider
for the study of the control and stability of the tailless aircraft. A far
cry from the Hill tailless designs of the 1920s, the NRC experimental
glider was rather conventional with the usual
elevons, flaps, fins, and rudders at the wing
tips, and a retractable tricycle landing gear. After initial flights in
1946, the aircraft flew some 105 hours of which 18 hours were in free
flight. In September 1948, the glider was towed about 2300 miles across
Canada. Flight characteristics were good, although there was a lack of
rudder power at low speeds. Work on the project was terminated by 1950.
With the assistance of England's Professor G.T.R Hill, designer of the
Pterodactyl series, Canada's National Research Council developed this
experimental tailless glider. First flown in 1946, the glider exhibited
good flying characteristics, although it lacked rudder power at low
speeds. The wing tips, including elevon, fin, and rudder, could be rotated
to prevent tip stalling and improve lateral control at low speeds.
Of the many tailless
aircraft projects that reached the advanced development stage during the
mid-1940s, two British designs stand out: the Armstrong Whitworth A.W. 52
jet-powered flying wing, for its visionary approach to the jetliner of the
future; and the de Havilland D.H. 108 tailless research aircraft, which
became the first British aircraft to exceed the speed of sound. Although
these aircraft flew after the war, their designs reflect the advanced
thinking of British designers during the latter stages of the war.
The Armstrong Whitworth
project consisted of a logical progression of experiments, commencing with
wind tunnel model tests, followed by a glider that was a half-scale model
of a 34,000-pound powered aircraft. This in turn was to be half the size
of a projected airliner that would weigh about 180,000 to 200,000 pounds.
The object of the designs was to combine the merits of the tailless design
with the advantages of the laminar-flow wing. This arrangement could
theoretically result in an aircraft with a total parasite drag about
one-third of that of a conventional aircraft.
Following successful wind
tunnel tests, design work started on the A.W. 52G glider in May 1942, and
it was finally towed into the air for the first time three years later, in
March 1945. Built mainly of wood, the two-place craft was controlled by
wing tip elevons that were hinged to the trailing edges of "correctors"
hinged to the wing. Correctors provided trim in pitch and also corrected
the pitching moment resulting from flap operation. Spoilers fitted to the
upper surface of the wing and a vertical fin and rudder at each wing tip
completed the control arrangement. An anti-spin parachute was housed at
the base of each rudder. Boundary-layer control was provided over the
outer section of the wings by the suction of the boundary-layer air into a
slot located in front of the elevons. This prevented the breaking away of
the air flow over the wing and delayed wing tip stall at low speed.
Wind-driven pumps were mounted on each main landing gear leg to provide
power for the boundary-layer control.
Flight tests of the A.W.
52G proceeded well enough to confirm theoretical calculations. The next
step in the development plan was the production of two A.W. 52 jet-powered
research aircraft with a design weight of about 34,000 pounds.
Configuration of the powered aircraft closely resembled that of the glider
version, with the obvious addition of two 5000-pound thrust Rolls Royce
Nene turbojets buried in the wing centre section on either side of the
cockpit. Boundary-layer control suction was provided by the turbojets,
with the suction slots in the wing connected by ducts to the engine air
intakes. Designed for speeds of 400-500 mph, the aircraft also had an
ejection seat for the pilot only, retractable tricycle landing gear,
pressurized cockpit, and thermal de-icing of the wings using jet exhaust.
The test pilot for
Armstrong Whitworth, E.G. Franklin, flew the first A.W. 52 (TS 363) on
November 13, 1947. The second aircraft, TS 368, fitted with Rolls-Royce
Derwents, flew almost a year later, on September 1, 1948. Although the A.W.
52 was an impressive attempt to further the state of the art, the test
flights were disappointing. Laminar flow was not achieved, and landing and
takeoff distances exceeded those experienced with a conventional aircraft
of similar wing loading. Elevator control of the aircraft was extremely
sensitive.
These two photographs of the jet powered A.W. 52 in flight clearly show
many of the distinctive design features of the craft. The trailing edge of
the centre section of the wing had a Fowler flap that was dished to pass
under the protruding turbojet tail pipes. Vertical fins and rudders at the
wing tips provided directional control. At the base of each rudder was a
compartment for an anti-spin parachute.
The first aircraft was
lost on May 30, 1949, due to an asymmetric flutter that caused the pilot
to abandon the aircraft in flight. Although the second model subsequently
underwent a research program on airflow behaviour on sweptback wings at
the Royal Aircraft Establishment at Farnborough, until September 1953,
Armstrong Whitworth abandoned further development efforts. Investigation
established that the structure had failed under the tremendous loads
experienced at airspeeds of about Mach 0.9.
While Armstrong Whitworth
conducted their A.W. 52 tests with an eye on the jetliner of the future,
engineers and designers at the de Havilland Aircraft Company, pursued the
same goal using a completely different approach. In October 1945, under
the guidance of Chief Designer Ronald Bishop, the de Havilland design team
selected the acorn-like fuselage of a de Havilland Vampire jet fighter,
attached a rakish vertical fin and rudder on the aft end, and drew up a
pair of shapely, swallow-like wines to complete the arrangement. Power was
provided by a de Havilland Goblin 4 turbojet engine generating 3750 pounds
of thrust.
Designated the D.H. 108,
and appropriately called the Swallow, the first of three versions, TG 283,
flew on May 15, 1946, with de Havilland's son Geoffrey at the controls.
The first model, fitted with Handley Page slots fixed in the open
position, was designed to determine low-speed characteristics of the swept
wing, while the second, TG 306, was equipped with retractable slots and
was intended to assess high-speed swept wing characteristics. The Swallow
project was marked by moments of spectacular triumph and tragedy for de
Havilland and British aviation in general. Tragedy struck on the evening
of September 27, 1946. Geoffrey de Havilland died when his D.H. 108
disintegrated during high speed flight.
A third aircraft, VW 120,
was built along the same lines so that the high speed program could
continue. Fitted with a Goblin engine of higher rating, the aircraft also
incorporated power-boosted controls, a sharper nose, and a lower cockpit
with strengthened canopy. It was in this aircraft that test pilot John
Derry set a world's 100-km speed record of 605.23 mph on April 12, 1948. A
few months later the D.H. 108 became the first British aircraft to exceed
the speed of sound. On September 6, 1948, John Derry put the D.H. 108 into
a dive at 40,000 feet at full power and held the dive until the needle on
the Mach meter passed the number "1" True air speed was calculated to be
about 700 mph.
John Derry, famous de Havilland test pilot, is shown climbing into the
cockpit of a D.H. 108 moments before taking off for his record breaking
flight on April 12, 1948. Derry was killed on September 6, 1952, when the
de Havilland D.H.110 which he was flying broke up during a flight
demonstration at Farnborough.
The third de Havilland D.H.108, VW 120, was flown by John Derry to a new
world's closed course speed record of 605.23 mph on April 12, 1948. VW120
was also the first British aircraft to exceed the speed of sound.
Flight tests continued
with the two remaining D.H. 108s at Farnborough until 1950. On February
15, 1950, VW 120 crashed, killing the pilot, J.S.R. Muller-Rowland. A few
months later, the first aircraft, TG 283, crashed during stall trials,
killing the pilot G.E.C. Genders.
Despite the accidents that
plagued the program, the graceful D.H. 108 brought a most welcome measure
of prestige to British aviation with its outstanding
performance. Perhaps of more importance, the flight test program provided
invaluable data that convinced de Havilland engineers that a tailless
airliner was not a practical proposition. The result was a more orthodox
approach to the design of the world's first civil jet transport, the de
Havilland D.H. 106 Comet.
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