TM 5-826-6/AFR 93-5
(b) Medium severity level (M).
Corrugations are noticeable and significantly affect ride quality (see
measurement criteria below, (fig. A-16).
Figure A-16. Corrugation.
(c) High severity level (H). Corrugations are easily noticed and severely affect ride quality (see
measurement criteria below).
(3) Measuring procedure. Corrugation is measured in square feet of surface area. The mean elevation
difference between the ridges and valleys of the corrugation indicates the level of severity. To determine the mean
elevation difference, a 10-foot straightedge should be placed perpendicular to the corrugations so that the depth of the
valleys can be measured in inches. The mean depth is calculated from the following measurements.
< 1/4 inch
< 1/2 inch
1/4 - 1/2 inch
1/2 - 1 inch
> 1/2 inch
> 1 inch
Some of the example photographs were taken on roads and streets because corrugation is not commonly found on airfield
e. Depression, distress 45.
(1) Description. Depressions are localized pavement surface areas having elevations slightly lower than those
of the surrounding pavement. In many instances, light depressions are not noticeable until after a rain when ponding of
water creates "bird-bath" areas, but the depressions can also be located without rain because of stains created by ponding
of water. Depressions can be caused by settlement of the foundation soil or can be built during construction. Depressions
cause roughness and, when filled with water of a sufficient depth, could cause hydroplaning of aircraft.
(2) Severity levels.
(a) Low severity level (L). Depression can be observed or located by stained areas, only slightly affects
pavement riding quality, and may cause hydroplaning potential on runways (see measurement criteria below) (fig. A-17).