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Alexander Klemin
Professor of Aeronautical Engineering
c/o Daniel Guggenheim School of Aeronautics
University Heights
New York City
C O P Y
June 19, 1940
Mr. Leon Henderson
Securities Exchange Commission
Washington, D. C.
Dear Mr. Henderson:
With reference to our conversation of the 12th, I am setting
down my well considered opinion regarding Mr. Burnelli's principles
of aircraft design - the result of many years of study and wind
tunnel experimentation.
1. The basic idea is that the conventional fuselage shall be
eliminated and housing
space shall be provided within a lifting airfoil, while tail surfaces
are supported at the end of appropriate booms.
2. From the elimination of the fuselage which is an element
of purely parasitical
drag, there follows reduction of aerodynamic resistance. This
logical conclusion has been checked again and again in wind tunnel
tests made under my direction here, and in other tunnels.
3. From the reduction in aerodynamic drag, there follows improvement
in
performance, that is in high speed, climb and fuel consumption
for a given weight of the airplane and horse-power. This conclusion
has been checked by several performance calculations carried out
in classical fashion from the impersonal findings of wind tunnel
tests.
4. An approach is made to the aerodynamic ideal of a "flying
wing" airplane.
5. All other aerodynamic characteristics of an airplane such
as longitudinal,
stability and control, lateral stability and control, remain those
of the best modern practice.
6. The special employment of the airfoil in lieu of the conventional
fuselage permits
the volume of housing capacity to be largely increased without
any sacrifice of aerodynamic efficiency.
7. Increased housing capacity is particularly useful for modern
bomber design. The
bomber carries bombs, racks, instruments, accessories, supercharger
intercoolers, etc., an enormous and complex installation, which
it is very difficult to install efficiently in the conventional
fuselage. From this point of view the Burnelli bomber designs
which I have had occasion to study offer great advantage in military
aircraft design as distinct from the aerodynamic advantages to
which I have referred previously. All other military requirements
such as vision and range of gun fire are fully retained.
8. The Burnelli bombers definitely add to our air defense possibilities.
9. The ability to increase space for passenger accommodation
in the air transport
plane without sacrifice in aerodynamic efficiency is equally important,
and makes the Burnelli principle valuable in the design of large
passenger transports.
10. For the same reason Burnelli designs are well adapted to
serve as troop carriers.
11. From the main principle of design there derive logically
and inevitably certain
other important advantages which will be enumerated as briefly
as possible:
a. The central portion of the wing or lifting airfoil fuselage
carries an appreciable proportion of the total weight of the aircraft, thereby,
the stresses at the root of the outer wings are reduced and structural
weight is saved - as have both demonstrated by careful analyses
submitted to the Civil Aeronautics Authority.
b. The elimination of the structural unit of the fuselage results
in further saving of structural weight and with appreciable advantage in manufacturing
economy.
c. The streamlined fuselage has difficult compound curves.
Its elimination results in
simpler and less expensive construction.
d. The substitution of the airfoil for the fuselage --- for
the engines of a twin-engined
machine in direct access to the crew which is a distinct advantage.
e. Placing of engines ahead of all occupants is a safety measure.
f. Since the useful load, (passengers, installation, etc.)
does not have to be spread out
along the longitudinal axis of the aircraft; the longitudinal
maneuverability is increased.
g. The large undersurface of the central portion of the wing
provides excellent housing
for the landing gear.
h. The general structural design is such that there is concentration
of stress and support
points which is as it should be.
12. The general conclusion is inescapable: The Burnelli principles
offer an advance
in the art, in efficiency and economy.
Sincerely yours,
AK/d s/ Alexander Klemin
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