CHAPTER 4. RUNWAY CERTIFICATION
While a great deal of effort and time will have
30% overload factor, although seemingly some-
been spent to select the location and to construct a
what small, is really quite adequate, since the in-
runway, this by no means qualifies the site as an
situ ice is in a confined state.
airport. In preparation for aircraft operations from
If weak ice or gaps and crushed horizons are
the glacial ice all parties (e.g., construction team,
discovered, further coring should take place to
field engineer, project sponsor, site manager, flight
determine the extent of the problem area. If the
company, and pilots) must be confident of the
area is relatively small, the process of full-scale
ability of the runway and the site to safely sup-
testing and patching can be used to bring them
port flight operations. Many of the preliminary
up to a suitable strength. If the extent of the prob-
steps in the process outlined here will have indi-
lem area is too large to lend itself to repair, sev-
cated that the site characteristics are suitable for
eral options exist. Repositioning the runway
aircraft operations. However, final certification of
slightly to one side may be to allow the weak area
the runway by some appropriate authority is only
to be abandoned. Of course, if the weak area is
prudent, because lives and expensive equipment
centrally located, this could require a lot of work
are at risk.
and is probably not desirable. Another possibility
is the use of a compacted snow cover to assist in
load distribution. This may be an attractive op-
tion only for sites where significant quantities of
SMALL-SCALE MECHANICAL TESTS
snow are available and at sites that would require
A series of cores should be taken from random
a protective cover anyway during a portion of the
locations on the runway. Any locations where fill
season to avoid solar-induced degradation.
was added, and sites where particularly large blis-
As a last resort, the bearing strength of the ice
ters were graded, should also be cored. The core
from these tests can be used to set the limit for
holes should be inspected to ensure integrity of
aircraft contact pressure. This may mean that a
the subsurface ice. Since grading of the surface ice
different type of aircraft will need to be used at
will have exposed lower horizons of ice, small-
the site, or possibly that a reduced inflation pres-
scale compression tests should be completed on
sure will need to be maintained for operations at
the top of these cores and from a segment of the
the glacial ice runway. The latter may be feasible,
core about 0.5 m (1.5 ft) from the top. Simple
since heat buildup of tires will most likely not be
unconfined compression tests are adequate for
a problem when operating in polar regions, but
ensuring that the ice will support a stress suitable
reduced tire pressure may required a reduced
for the aircraft to use the facility. More sophisti-
cated compression tests may be performed and
will yield more information on the ice's mechani-
cal behavior (e.g., stressstrain response, elastic
FULL-SCALE LOAD SIMULATION
modulus, Poisson's ratio), but the most important
quantity to obtain is the stress at the point of
In preparation for the first flight at a glacial ice
brittle failure.
runway, full-scale testing will stress a far greater
These mechanical tests should be performed at
percentage of the runway than most mechanical
ice temperatures within a few degrees of the tem-
test methods. In addition to being good engineer-
perature at the time of anticipated runway use. If
ing, the full-scale test may have important psy-
the runway will be required to support aircraft
chological benefit to pilots, flight managers, and
over a range of ice temperatures that vary more
others. This will relieve the construction team
than about 10C (especially if some of these tem-
and field engineer from having to rely heavily on
peratures are above 5C), mechanical tests should
statistical means for certifying the integrity of the
be done at two or more temperatures represent-
runway. Full-scale testing is not cheap, but this
ing the range. During core testing, the loading
cost should be placed in perspective with the value
rate should be no less than 44 kN/s (10,000 lb/s).
of aircraft and the persons who will use the run-
We recommend that the ice cores be able to sup-
way.
port a compressive stress of at least 2.0 times the
Ideally, full-scale tests (proof rolling) should
maximum contact pressure (essentially the maxi-
simulate the worst possible case. For aircraft op-
mum tire pressure) of the design aircraft. The
erating on glacial ice, this translates to maximum
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