Muche's Warbirds
Articles, Interviews &
Stories
THE N9MB FLYING WING
by
JIM MUCHE
PHOTOGRAPHS BY LANI MUCHE
(These photos may be seen in a larger size at Muche's Warbirds: N9MB)
Fifty-five years after it last military flight the Northrup N9MB Flying Wing can once again be
seen in the skies over Southern California. The aircraft, which is the sole survivor of the
original XB-35/YB-49 long-range bomber program, was restored by an all-volunteer group at
The Air Museum Planes of Fame in Chino, CA in a project that took over 13 years to
complete. Each of the four N9M Flying Wings were developmental aircraft and differed in
several ways. In addition, numerous changes were made directly to the aircraft during testing
so that little in the way of formal documentation on design and construction exists. Because of
this, restoration volunteers had to, literally reverse engineer the entire project. Don Lykins,
Chairman of the Board for the Museum and one of the current N9MB pilots, summed up the
enormity of the task when he stated: "The men and women who worked on this project
deserve enormous credit. This was the most complicated aircraft restoration project ever
undertaken by a museum volunteer crew."
The N9MB, and all of the Northrop flying wing
designs, came about because Jack Northrop
became convinced as early as 1923 that the limit
had been reached in conventional airplane design
development. He felt that the next logical step
was an all-wing aircraft which would do away
with the drag-producing fuselage and tail. The
entire airframe would create lift and significantly
increase overall performance. By 1929 he had
produced the X-216H which, while it still
employed a small twin-boom tail, refined the
concept of the wing and led to the first successful all-wing design, the N1M "Flying Jeep".
First flown in 1940, the N1M made over 200 flights before being retired in 1941.
In November 1941 Northrop was awarded a contract for the development and construction of
the XB-35 long-range bomber. This aircraft, a true flying wing design, was to have a
wingspan of 172 ft and be capable of carrying a bomb-load of over 52,000 lbs with a range of
7500 miles. In conjunction with this program, a contract was also awarded for the
construction of four operational design models. These 1/3 scale models, designated N9M,
were to act as flying test beds and also serve to familiarize Air Force pilots with all-wing
operations.
Constructed primarily of wood around a metal tube center section, these 60 ft wingspan
aircraft flew hundreds of hours at Muroc Dry Lake Bed (now Edwards AFB, CA) over a 3year period. Once design testing was completed, they were turned over to the Air Force as
trainers and were flown until the late 1940s. Among those who flew the aircraft were Chuck
Yeager and Bob Hoover.
The first three aircraft, the N9M-1 (which was lost in a flight test accident), -2 and -A were all
powered by two 260 hp Menasco C6S-4 engines which were considered underpowered. The
Museum aircraft, the N9MB, is powered by two 300 hp 8 cylinder Franklin 0-540-7 engines
which drive extension shafts to the 2-bladed Hamilton Standard pusher propellers via a fluid
drive coupler. The coupler helps to reduce engine/propeller vibration problems and also
allows the disengagement of the propellers from the engines to stop rotation in the event of an
emergency.
The flight control system consists of a
conventional control wheel connected to elevons
and rudder pedals operating split trailing-edge
rudders independently. Elevon surfaces
(combined elevators and ailerons) are deflected
together for pitch control and differentially in
opposite directions for roll control.
The N9MB was also further modified by the
removal of the 50 gal fuel tank located behind the pilot, which allowed the installation of an
observer's seat. This seat was occasionally occupied by Jack Northrop, himself, to observe
first-hand the program's progress.
Restoration of the Wing , which had last flown in May 1945, was a long and painstaking
process. Acquired by the Museum in 1950, nothing was done with the aircraft until 1982. The
original wood, which had decayed over the years, was used as patterns for the fabrication of
new parts. Pragwood, a special laminate available only in Germany, was imported for the
load-bearing sections and laboriously hand shaped and fitted. All other components were
inspected and refurbished or replicated as the need arose. Lack of documentation complicated
the project (Northrop had been approached early on but had declined to assist because of the
liability involved in a flying restoration) and each part or section had to be disassembled,
identified as to construction, material and function, and then either refurbished or
remanufactured.
The Franklin engines presented their own unique problems. Only 13 of these powerplants had
been built and today only three are known to exist. Those three were leaking oil from the
cylinder heads. An engine overhauler who had worked on Franklins for years was able to
determine that the crush gaskets between the steel cylinders and the aluminum heads had for
some reason been omitted on these engines, thus causing the problem.
This was only one of the thousands of details
that had to be worked out by the restoration
crew. They have literally rewritten the book on
the N9MB which made its first official flight on
November 11, 1994. Following that flight a
genuine flight test program was undertaken and
completed. The tests, which returned the aircraft
to full operational status, were meant to
revalidate Jack Northrop's original concept. The
Museum, which has dedicated the plane to the
memory of Northrop, feels that this test program
was a truer evaluation of the Flying Wing concept than is the B-2 Stealth Bomber currently in
service. The aircraft is now a much sought after air show attraction and often shares the sky
with the B-2 as a featured attraction. "The N9MB is not a product of the computer age but
sprang directly from Northrop's mind. It flies because of the soundness of that design and the
craftsmanship of the people who built it by hand." Project leader and primary N9MB pilot
Ron Hackworth expressed the feeling of all those who worked on the project: "This is our gift
to the Museum and aviation history." A history made much richer by the genius of Jack
Northrop and the efforts of Planes of Fame.
EGY MÁSIK ANGOL HIVATKOZÁS
The N-9M was the next logical step from the N-1M to a design suitable for a large flying
wing bomber. The N-9M was a roughly 1/3 scale model of the planned larger bomber,
designed to test theories of stability, control, and maneuverability. To this end, four planes
were built.
The first, the N-9 M-1, was first flown on the December 27, 1942. It was supposed to have a
range of 3 .2 hours, carrying 100 gallons of fuel up to 21,500 feet and weighing 7,000 pounds.
The first N-9M was powered by two Menasco C6S-4 engines, which proved to be a source of
considerable trouble.
The N-9 M-1 made about 45 flights, most of which were terminated by failures in the engines
or other systems. On May 19, 1943, after only 22 hours of flight time, the N-9 M-1 crashed
near Muroc Army Air Base. The pilot was killed after the plane was in a spin, and was unable
to exit the plane.
The second plane, the N-9 M-2, first flew on June 24, 1943. This flight was terminated when
the canopy came off in flight! Fortunately, the pilot was able to land the plane with only
minor damage. The N-9 M-2 generated a large amount of data on drag, which led to the
conclusion that the wind tunnel data for the planned XB-35 was incorrect, and the plane
would have roughly 10% greater drag than planned.
One of the more interesting things discovered during flight tests was the severe reversal of
elevator control forces at high lift coefficients. This was caused by premature separation of
the airflow over the top of the wing, and may have been a contributing factor to the loss of the
first N-9M.
The N-9MA was first flown on June 28, 1944. This version featured the controls which would
be built on the XB-35, which included split trailing edges, pitch control flaps, and a leading
edge slot near the wing tips. These features improved the rough air handling of the design, as
the first N-9Ms were reported as being unsatisfactory in that regard.
The N-9MB featured more powerful 300 hp Franklin engines, and, like the N-9M-1, featured
a passenger seat behind the pilot.
One of the N-9Ms is currently owned (and flown!) by the Planes of Fame Museum, in Chino,
California.
A HARMADIK
The Northrop N-9M was a one-third-scale demonstrator for the development of the XB-35
flying wing bomber. It was designed to provide flight test information from which the
maneuverability, controllability, and performance of the XB-35 could be predicted. Four of
these aircraft, the N-9M-1, N-9M-2, N-9MA, and N-9MB, were built. The Secretary of War
approved construction and flight-testing of the flying mock-up on 3 October 1941.
The aircraft, constructed primarily of wood, had a wingspan of 60 feet and weighed 7,000
pounds. It was designed for an endurance of 3.2 hours with 100 gallons of fuel, and had a
design ceiling of 21,500 feet. Rather than a control stick, the N-9M-1 had a control column
and wheel. This cumbersome arrangement was consistent with its role as a bomber mock-up.
Flight controls consisted of elevons, rudders, and trim tabs, but no vertical control surfaces.
Hydraulically operated, retractable tricycle type landing gear were supplemented by a fourth
retractable wheel extending from the trailing edge just aft of the canopy to protect the
propellers in the event of an extremely tail-low landing.
The first flight of the N-9M-1 took place on 27 December 1942, with Northrop test pilot John
Myers at the controls. Over the next five months there were 45 flights. With a few exceptions,
most were terminated by mechanical failures of one sort or another. The two 260-hp Menasco
C6S-4 pusher engines were particularly troublesome. Consequently, very little data relative to
drag, stability, and control were obtained.
Jack Northrop (1895 - 1981)
Northrop XB-35
Jack (John Knudsen) Northrop
by Peter Bergenson
http://www.bergen.org/AAST/Projects/Engineering_Graphics/_EG2000/flyingwing/history/ja
ck.htm
JACK NORTHROP Born Newark NJ, Nov 10, 1895. Died 1981. John Knudsen Northrop's
family moved to Santa Barbara CA in 1914, where he developed an deep interest in
aeronautics in high school. In 1916 he had went to work for the Loughead Brothers as an
engineering draftsman, contributing to the design of their twin-engine F-1 flying boat.
Moving in 1916 to Douglas Co in Santa Monica, he went from draftsman to designer to
project engineer om several early Douglas aircraft. The next major move came in 1927, when
he went with Lockheed, there designing the original Vega. However, needing to develop his
own ideas about all-metal airplanes, he struck off on his own in 1929 to form Northrop
Aircraft Co, there producing the Alpha, an airplane that was regarded as well ahead of its
time.
Following the success of Alpha, he developed the all-metal design into Beta, Delta, and
Gamma. Northrop Corporation was formed in 1932, and became a subsidiary of Douglas, to
produce his designs of the USAC A-17 attack planes for and USN BT-1 dive bombers, as well
as export models for foreign countries. In 1938 he sold his interests in the corporation to
Douglas and formed Northrop Aircraft Inc, becoming its president and chief engineer until his
retirement in 1952.
There, in addition to many successful military aircraft, he developed his pet flying-wing
project, the visionary concept of which, stalled by bureaucracy at the time, finally proved its
value in our present stealth aircraft designs. Jack Northrop was a widely-known and wellrespected name in aviation by that time, and he was awarded the Presidential Certificate of
Merit for his "extraordinary contributions to the nation's defense in World War II."
He presided over the Institute of Aeronautical Sciences in 1946, and became an honorary
fellow in its successor organization, the American Institute of Aeronautics and Astronautics,
and a fellow of the Royal Aeronautics Society. In 1947 he received the St Louis Medal from
the American Society of Mechanical Engineers for "meretorious service in the advancement
of aeronautics." Investiture in the International Aerospace Hall of Fame came in 1972 and in
the Aviation Hall of Fame in 1974.