Figure 8. Thin section of typical melt/refreeze ice within glacier ice show-
ing large crystals.
Figure 9. Thin section of milky glacial ice showing fine-grained texture.
when dropped. Thin sections of the milky ice
Pegasus, initial surveys provided a general topo-
were very typical of snow-derived ice; many small,
randomly oriented crystals were visible (Fig. 9). It
swales (Fig. 10). The surveys showed that a great
was anticipated that this ice would have greater
deal of cutting would be necessary to produce a
strength and less brittle behavior.
surface free of the large depression near the
midlength of the runway. If this 300-m section
Ice surface characteristics
could be filled (maximum fill depth of about 0.3
No universally accepted criteria are available
m) and if the runway was divided into three sec-
to determine allowable roughness for a runway.
tions, each with a slightly different grade, a mini-
This topic is discussed by Gerardi (1978) and
mal amount of ice would need to be removed to
Sonnenburg (1978), but there seems to be no agree-
achieve a very smooth surface.
ment as to whether passenger or aircraft acceler-
ations should dictate limits to roughness. For
vey results was compared to U.S. MILSPECMIL-