Aeroplanes get larger and larger, consequently
hangars to house them must grow at a similar
rate – and this inevitably means greater cost.
The Lockheed company has such a problem with
the housing of its latest transport aeroplane,
the largest transport yet built: one should say
‘had’ the problem because it has been solved by
an ingenious patented gigantic steel framed
double cantilever hangar large enough to house
simultaneously four aircraft each of which is 246
ft long, 65 ft high and measures 223 ft wing tip to
wing tip: and yet show savings in cost!
The design of the hangar envisages two backto
back cantilevered canopies, one for static and
fatigue ground testing, the other to house aircraft
undergoing actual flight tests. The two areas are
completely column-free and provide a clear span
height of 78 ft throughout. Offices, laboratories
and workshops are contained in the central core of
the hangar occupying five storeys and a total area
of 240,000 sq ft. This central core is the supporting
structure for the two massive cantilevered roofs:
one roof extends 261 ft, the other 271 ft.
The outstanding structural feature of the hangar
is a superstructure extending above the roof of the
central core and holding the cantilevered roofs
in position. This superstructure is supported by
one hundred 14-in columns which extend from
the foundations up through the centre core. To
achieve the full height of the superstructure –
142 ft from the ground – these main columns
which are 87 ft long below the roof, are spliced
above the roof to the centre core.
Two exposed main tension and compression
members – 24-in wide flange beams with 19-in
channel caps – extend down at an angle from
the top of the columns and connect to the trusses
Reprinted from Volume 5 No. 1
forming a triangular structural system.
The object of the superstructure – in addition
to holding the cantilevered trusses in shape – is
to provide resistance against uplift in abnormal
wind conditions. This means that the ends of
the trusses will move up and down a few inches
and no more, under maximum wind or live load
It is estimated by the designers that the
advantage in saving of steel with this hangar
over a conventional cantilever design, lacking the
superstructure, can be as high as 32 per cent with
a maximum saving in cost of 24 per cent – very
The designers draw special attention to the
fact that each cantilever canopy supports a full
coverage, bridge crane system of 10 ton capacity.
The hangar illustrated in the article is equipped
with enormous structural steel sliding doors on
each end of the two 480 ft hangar ends: these doors
are 70 ft high and 80 ft wide but it is emphasised
that experiments are now being carried out with
doors of up to 100 ft clear height.
Five thousand tons of steel are being used in this
structure which becomes fully operational this
month (February 1968).
Complete dimensions of the hangar – 630 ft by
480 ft with a height of 142 ft.
50 Years Ago
‘Back-to-Back’ Cantilever Hangar