Proof rolling at the C-130 level began on 27
This provided factors of safety of 1.25, 1.4, and 1.3
January 1993. After 10 round-trips, approximately
for gross load, single tire load, and tire pressure,
18 m (60 ft) of the center width of the runway had
respectively. The proof cart was towed with the
received extensive coverage. An additional 40 ft
14G grader at a speed of 4 km/hr. The entire
of width was tracked with a tire-to-tire spacing of
runway surface was covered with a tire track-to-
about 2 ft. The first round-trip with the proof cart
tire track spacing of less than 1 m. No failures
was completed with a tire pressure of 1380 kPa
were found of the type seen the prior year. Sev-
(200 psi). This was done to observe the response
eral shallow gouges were detected which had been
to its new configuration of some components of
formed by the bulldozer blade used to clear win-
the proof cart. Following this first round-trip, the
ter-over snow. These gouges were patched. Proof
tire pressure was reduced to about 1100 kPa (160
rolling was completed in two days. The runway
psi); all subsequent passes were completed at this
was certified for C-130 and C-141 operations and
pressure.
opened for air operations on 25 January 1994.
During the first round-trip with the proof cart
Once a glacial ice runway has been proof rolled
(1380-kPa or 200-psi tire pressure), two ice fail-
satisfactorily, probably to repeated full-scale test-
ures occurred; each was about 1.4 m2 (15 ft2) in
ing is only necessary if something significant
size with a depth of about 15 to 20 cm (6 to 8 in.).
changes with respect to the runway. Such occa-
The failed spots showed broken up ice chunks in
sions might be 1) if cracks, bumps, or melt fea-
the failed area, but the cracks did not extend into
tures appear on the runway, 2) if different aircraft
the surrounding ice as was the case in November.
are considered with potentially more severe land-
Sixteen ice failures were experienced during the
ing gear loads, or 3) the runway will be used at a
42 round-trips (at a tire pressure of 1100 kPa or
time of year when temperatures will be signifi-
160 psi) covering the western 76 m (250 ft) of the
cantly different than when proof rolling was done.
90-m (300-ft) wide runway. These failures were
Other options include, for instance, fabricating
similar to the two discovered during the first pass
a cart or vehicle that duplicates only one side of
at 1380 kPa (200 psi). The proof cart was driven
the aircraft's main gear or even just a single wheel.
immediately adjacent to each side of the failed
However, we advise against a single wheel proof
areas to ensure that all of the weak area was
rolling device, because the zone of influence
broken. Little or no additional breakage occurred.
(stress) below each tire in a group may overlap,
An additional 12 ice failures were experienced
depending on the geometrical placement on an
when we proof rolled the easternmost 50 ft of the
aircraft. This situation would be difficult to ac-
runway width. These failure spots tended to be
commodate with a single wheel device. Another
similar in nature to the others, but were generally
option may be a static plunger or load piston that
smaller in area and depth.
could be easily moved about on the runway to
In all, 30 ice failures occurred during the Janu-
test the integrity of a number of locations. This
ary proof rolling; none of these were at sites that
would require "matching" of the plunger's load
had been patched in November. All failures were
and contact area with the aircraft tires to allow
non-catastrophic and showed very little surface
interpretation of the data obtained by the proof
expression. When excavated, these failures all
rolling device. Each of these options has some
were seen to be associated with a thin (6 mm, 0.25
disadvantages, particularly the fact that they will
in., or less), near-surface gap containing hoar frost.
probably require considerably more time to test
At each site, the total area of damaged ice aver-
the majority of the runway surface. However, such
aged 1.5 m (5 ft) in diameter with a depth of 30 cm
devices will certainly be cheaper, smaller, and
(12 in.). All failure points were patched, and sev-
easier to operate.
eral of the larger ones were proof rolled again
successfully, further confirming the integrity of
our patching technique. The runway was thus
PATCHING
deemed ready for flight tests by C-130 aircraft
(see section on flight tests).
In concept, the repair of ice surface defects
During the following austral summer season,
caused by grader damage, proof cart passage, or
the proof cart was rearranged to C-141 configura-
natural cracks is no different than patching of
tion. In early January 1994, proof rolling was be-
potholes in a highway or fixing a decayed spot in
gun with a total mass of nearly 136,200 kg (300,000
a tooth. The damaged or failed area is removed
lb) and a tire pressure of about 1725 kPa (250 psi).
and new material with equal or greater strength
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