30 June 2001
(a) Determine the aircraft traffic that is anticipated to use the pavements during the life of
the pavements. Arrange this traffic in accordance with aircraft type, gross weight, and number of
(b) Select the pavement thickness required for each aircraft at the design gross weight,
pass level, and pavement characteristics.
(c) Select the controlling aircraft as the one requiring the maximum thickness.
(d) Evaluate the controlling thickness in terms of allowable passes for each aircraft in the
design mix using the appropriate design curves from Figures 12-1 to 12-17. Those curves are entered
from the left with the flexural strength, modulus of subgrade reaction, and load and from the right with
controlling thickness and traffic. The intersection point of these two lines will estimate the allowable
number of passes of an aircraft. An example of this operation is shown in Figure 12-18.
(e) Determine the number of each aircraft equivalent to one pass of the controlling aircraft
by dividing the allowable passes of each aircraft by the allowable pass level of the controlling aircraft.
(f) The number of design passes for each aircraft is then divided by the equivalent passes
to determine the total number of equivalent passes of the controlling aircraft to be considered for final
(3) Example problem solution.
(a) Determine the thickness of pavement required for a taxiway having the mixture of
aircraft, gross weights, and number of passes as shown in columns 1-3 in Table 12-1. The concrete
design flexural strength R is 4.48 MPa (650 psi), and the modulus of soil reaction k is 54 kPa/mm
(b) The pavement thickness required for each aircraft is shown in column 4 as determined
from appropriate design curves. (Figures 12-3, 12-4, 12-13 through 12-15)
(c) Determine the allowable number of passes of each aircraft for the controlling thickness
in column 4 of 363 millimeters (14.3 inches) for the C-141. These allowable passes are determined from
the aircraft respective design curve and listed in column 5.
(d) Divide the allowable number of passes (column 5) by the allowable number of passes
for the C-141 (10,000). This gives the number of equivalent passes of each aircraft in terms of one pass
of the C-141 and is shown in column 6. For example, one pass of the C-141 is equivalent to 780 passes
of the F-15 at the design weights.
(e) Divide the number of design passes in column 3 by the number of equivalent passes
in column 6 to determine the total number of equivalent C-141 passes for design. These values are
shown in column 7.
(f) Determine the total number of equivalent C-141 passes by totaling the values in
column 7. Enter the C-141 design curve (Figure 12-14) with the total number of equivalent passes
(20,129), the design load of 156,490 kilograms (345 kips), R of 4.48 MPa (650 psi), k of 54 kPa/mm
(200 pci), and traffic area A to determine the final design thickness of 381 millimeters (15.0 inches).
These values will be rounded to 380 millimeters (15.0 inches).