This item is only available as the following downloads:
N^IV- K '5
NATIONAL ADVISORY CO:.:ITTEE FOR AERONAUTICS.
TECHNICAL MEMORANDUM NO. 523.
AUTOGENOUS WELDING IIT AIRPLANE CONSTRUCTION.*
By Ludwig Kuchel.
In the original manufacture of airplanes from wood, the
warping of the structural parts through the influence of the
elements could not be entirely prevented, despite the careful
selection of the wood. An improvement was made by using plywood
for covering the fuselage and wings. Plywood was used in Ger-
many during the war on most of the military airplanes.
The increased requirements of airplanes, especially in mod-
ern air traffic, called for a homogeneous building material of
greater strength and reliability than wood, which is so easily
affected by external conditions.
The advantages of steel for highly stressed parts, as dis-
covered in engine building, led, in airplane construction, to
the use of steel tubing, which also offers less obstacles to
future structural development. Autogenous acetylene-oxygen
welding was found to be the only practical way to join the steel
Lightness is an essential characteristic of the structural
parts of an airplane. All the structural requirements which
must be satisfied by the building materials must therefore be
adequate without being excessive. While military airplanes are
*"Die autogene Schweissung im Flugzeugbau," from Schweissen,
Schneiden und Metallspritzen mittels Acetylen, 1927, pp. 27-33.
N.A.C.A. Technical Memorandum No. 523
not subject to considerations of economy, but only to those of
maximum efficiency, commercial airplanes must be governed by
both of these factors.
The structural parts of an airplane are the fuselage, wings,
tail surfaces, engine mount and landing gear.
Figure 1 is the picture of a twin-engine Albatros commer-
cial airplane. It has a full load of 3800 kg (8378 lb.) and an
engine power of 430 HP.
Fuselage.- The steel-tube framework of a twin-engine Alba-
tros commercial airplane (Fig. 2) for eight passengers and two
pilots has a framework of approximately square cross section
in the form of a lattice girder. The front part has K braces.
The rear fields are crossed by brace wires with the exception.
of the next to the last field, in which there are welded diago-
nal tubes for withstanding the stresses produced by the tail
skid in landing. The fuselage framework weighs 224 kg (494 lb.Y.
The joints are autogenously welded in all the structural parts.
The longerons consist of telescoped steel tubes of 40 mm (1.57
in.) diameter at the front end and tapering to 25 rm (0.98 in.)
at the rear end. The ends of the tubes are joined by sloping
welds. The requisite reinforcement is effected by muffs, which
are driven on and welded. The attachment joints of the wings
and landing gear, which are subject to great tensile or com-
pressive stresses, are reinforced by strips of sheet metal driven
IN.A.C.A. Technical Memorandum No. 523 3
into slots in the ends of the tubes and completely welded. The
eyelets required for attaching the brace wires are formed by
welded-in. tubular loops. No tube in the whole fuselage has a
wall thicker than 1 mm (0.04 in.), but the required safety fac-
tor of eight for the airplane is nevertheless exceeded.
Wings.- Figure 3 shows the whole wing structure, consist-
ing of a middle section and two lateral sections. Figure 4
shows a wing in process of construction. The spars are full-
walled box girders with open duralumin members. The fitted-irr
steel ribs have the form of lattice girders. The open spaces
in the front part of the wings are intended for the reception
of the fuel tanks.
The welded steel-tubing engine supports, which also serve
as wing struts, are installed between the upper and lower wings
on each side of the fuselage.
Figure 5 shows two of the ribs. The upper and lower
flanges are made of steel tubing 6 x 0.5 mm (0.24 x 0.02 in.),
while the welded-in lattices are made of steel tubing 5 x 0.5 mm
(0.2 x 0.02 in.). A span of 19 m (62.33 ft.) requires 65 such
ribs for each wing. These ribs are produced in quantity and
are welded with the aid of former.
Figure 6 shows the tail structures. The horizontal tail
structures, consisting of the stabilizer and elevator, have
welded frames with diagonal braces made from steel tubing of
N.A.C.A. Technical Memorandum No. 523
5 to 25 mm (0.2 to 1 in.). The stabilizer is adjustable, and
the elevator is hinged to it. The vertical tail structures,
consisting of the finmr and rudder, are likewise made of autoge-
nously welded steel tubing.
The ailerons are likewise made of welded steel tubing with
diagonal bracing. The hinge supports are made of steel tubing
with triangular bracing and are autogenously welded to the wing
Power plant.- Figure 8 shows the engine mount on a one-
engine commercial airplane. The autogenously welded steel-'
tubing engine mount is attached to the steel-tubing fuselage
at four points, so that the whole can be detached by removing
four bolts. The joints are reinforced by sheet metal, because
of the great stresses to which they are subjected. The weight
of the 220 HP. engine, with all its accessories, is 295 kg
(650 lb.). It is separated from.the pilot room by a fire wall.
Landing gear.- The streamlined struts are autogenously
welded (Fig. 9). The landing shock is absorbed by the telescop-
ing struts. The shock absorbers operate by compression of air,
sealed and regulated by oil. In this way the kinetic energy of
the airplane is converted into friction and heat, and the un-
avoidable springing in landing with rubber shock absorbers is
eliminated. With a stroke of about 24 cm (9.44 in.), an energy
absorption of about 45% of the total weight is attainable. The
Digitized by [lie Inernet Archive
in 2011 Wl[h funding from
University of Florida, Geoige A. Smathers Libiaries with suppOri fiom LYRASIS and [he Sloan Founrdatron
hu[p:, www.archive.org details aulogenousweldinOOunil
N.A.C.A. Technical Lamorandum No. 523 5
absorbed energy corresponds to a free fall of about 0.5 m (1.64
ft.) of the fully loaded airpl-'.ne. The unabsorbed forces are
transmitted to the fuselage.
Aside from the main structural parts, whose joints -.re al-
most exclusively welded, the gas-welding process is used to ad-
vantage in all kinds of fittings, connections, levers, etc.
Properly welded parts satisfactorily replace parts cut out or
forged in one piece. The welding process is simpler, quicker,
and cheaper cnd saves much weight, which is a very important
consideration in airplane construction.
For the different materials available for welding in air-
craft construction, adaptations of the welding wire have been
discovered, which render the welds, as improved by after-treat-
ment, very nearly as strong as the unwelded tubes. The excel-
lence of the weld depends largely on the skill of the welder,
who should have some understanding of the physical process in-
volved. In training welders, their individual qualifications
must be considered first of all. The inspectors must be able
to tell the difference between a good weld and one that simply
adheres or is burned.
For testing the welds, portions are taken from the completed
structures, from which samples are prepared for tensile and
bending tests. A bending test is made of the finished part, in
order to determine its buckling strength. This is a very good
test of the excellence of the welds and exposes any defects in
N.A.C.A. Technical Memorandum No. 523 6
It is generally assumed that the excellence of a welded
structure depends on the strength of the weld seam, since this
is ordinarily the weakest point. I cannot accept this assump-
tion unconditionally, however, since the weld seam may 'e the
strongest part of the structure under certain conditions. I
will omit the discussion of the welding wire to be used, as be-
ing too far reaching. I will only mention that it is important
to test the welding wire thoroughly for the different uses.
Autogenous welding has now become very important in airplane con-
struction. It facilitates the construction and shortens the
The new industries of aircraft construction and autogenous
welding constitute a timely coincidence. In 1903 the first
flights were made with engine-propelled airplanes, and in the
same year the first burners for acetylene-oxygen welding were
put on the market.
Although the laws of statics are fundamental for construc-
tion, progress is nade through the properties of the materials
used, as determined by experience. The type of girder used for
withstanding bending and buckling stresses in aircraft is al-
ready regarded with increased respect in other lines of construc-
tionr The autogenous welding industry is one of the few indus-
tries which can increase its usefulness through the discovery
and appropriation of new fields of application. There are many
such fields not yet aware of the fact that production ccn be
cheapened by the use of autogenous welding.
N.A.C.A. Technical Memorandum No. 523
D i s c u s s i on
Mr. Herz.- I only wish to ask whether autogenously welded
or seamless drawn tubes were used:
Dr. Kuchel.- Seamless drawn steel tubes, as obtainable in
the market, are generally used in airplane construction. There
is no need of producing them in the aircraft factory, because
every kind of tube can be bought ready made in the market.
Mr. Herz.- My question was meant somewhat differently. In
recent years quite an extensive industry has developed in the man-
ufacture of well-made autogenously welded tubes for all purposes.
Have these tubes yet been used in aircraft construction? I un-
derstand that such tubes were investigated in Italy in 1923 or
1924. I do not know, however, what the outcome was.
Dr. Kuchel.- I do not know of autogenously welded tubes
being used in aircraft construction either in Germany or else-
where. In a tour of investigation in the spring through France
and England, I found, however, that this kind of welding is done
with no such precision in either of these countries as in Germany.
Mr. Butz.- In the welding of thin-walled tubes, are there
any data available on the effect of the purity of the welding
Dr. Kuchel.- The welding section generally uses apparatus
in which the gas is purified in the ordinary way. It is endeav-
ored to keep the gas as cool as possible, to have it well washed
N.A.C.A. Technical Memorandum To. 523 8
and to have the purifying rateri:Ls renewed often enough.
Mr. Butz.- I recently ascertained the effect of the purity
of the oxygen in a large welding factory which produces thin-
walled tubes and bicycle frames in large quantities. This fac-
tory undertook to use high percentage oxygen. The rejections
were 30% greater than with oxygen under 98% pure. The demands
on the skill of the welder increase with the purity of the oxy-
gon, especially for thin-walled tubes.
Mr. Pothmann.- We found that the purer the gas, the rore
sensitive the flane was when wrongly adjusted. We also found
that oxidation occurred much more readily with very pure gas.
In ordinary welding poorer results were obtained with very pure
Dr. Streb.- According to our experiments, nitrogen up to
5% has no harmful effect on the quality of the weld. We have
not yet determined whether a smaller amount of nitrogen has an
actually favorable effect on the quality of the weld. There
were some indications in other experiments that the presence of
a small quantity of nitrogen in the oxygen prevented or substan-
tially reduced the carbonization of the weld, when a slight ex-
cess of acetylene was used.
Dr. Vogel (the presiding officer).- It seems that the ex-
perimental results do not yet justify their adoption. in practice.
This remark applies also to the results thus far obtained by
Translation by Dwight M. Miner,
National Advisory Committee for Aeronautics.
N.A.C.A. Technical Memorandum No.523 Figs.1,2,3,4,5,6,7,8,9
UNIVERSITY OF FLORIDA
3 1262 08106 667 1
xml version 1.0 encoding UTF-8
REPORT xmlns http:www.fcla.edudlsmddaitss xmlns:xsi http:www.w3.org2001XMLSchema-instance xsi:schemaLocation http:www.fcla.edudlsmddaitssdaitssReport.xsd
INGEST IEID E9HQPJQZP_JCR0QB INGEST_TIME 2012-03-26T14:29:26Z PACKAGE AA00009490_00001
AGREEMENT_INFO ACCOUNT UF PROJECT UFDC