UFC 3-260-03
15 Apr 01
for dual tandem tricycle, and C-5A for twin delta tandem. Special aircraft not included in these groups can
be studied separately (e.g. KC-10 and DC-10-30, or C-17, or small aircraft for the case of outlying landing
fields).
6. EVALUATION TESTING METHODS. There are two basic testing methods used to evaluate Army
and Air Force airfield pavements. These are nondestructive testing techniques and direct sampling tech-
niques. The most commonly used method is the nondestructive testing method. The evaluation proce-
dure using nondestructive testing is presented in chapter 4, the procedure using direct sampling for
flexible pavements is presented in chapter 5, and the procedure using direct sampling for rigid pavements
and overlays is presented in chapter 6. Evaluation procedures in areas subject to seasonal frost are
presented in chapter 7.
7. AIRCRAFT/PAVEMENT CLASSIFICATION NUMBERS (ACN/PCN). The ACN/PCN is a reporting
method for weight-bearing capacity and not an evaluation procedure. The National Imagery and Mapping
Agency publishes weight bearing limits in terms of ACN/PCN in a Flight Information Publication for civil
and international use. The intent is to provide planning information for individual flights or multiflight mis-
sions which will avoid either overloading of pavement facilities or refused landing permission.
a. The International Civil Aviation Organization (ICAO) (DOC 9157-AN/901 and Amendment num-
ber 35 to Annex 14) devised the ACN/PCN method as an effective, simple, and readily comprehensible
means for reporting aircraft weight-bearing capacity of airfields. The United States, as a cooperating
ICAO nation, has agreed to report airfield weight-bearing limits by this method, and the airfield weight-
bearing limits will be included in evaluation reports.
b. The ACN and PCN are defined as follows:
(1) ACN is a number that expresses the relative structural effect of an aircraft on different pave-
ment types for specified standard subgrade strengths in terms of a standard single-wheel load.
(2) PCN is a number that expresses the relative load-carrying capacity of a pavement in terms
of a standard single-wheel load.
c. The system is structured so that a pavement with a particular PCN value can support, without
weight restrictions, an aircraft that has an ACN value equal to or less than the pavement's PCN value.
d. ACN values will normally be provided by the aircraft manufacturers. The ACN has been devel-
oped for two types of pavements, flexible and rigid, and for four levels of subgrade strength.
e. The PCN numerical value for a particular pavement is determined from the allowable load-
carrying capacity of the pavement. Once the allowable load is established, the determination of the PCN
value is a process of converting that load to a standard relative value. The allowable load to use for Army,
Navy, and Marine Corps evaluations is the maximum allowable load of the most critical aircraft that can
use the pavement for the number of equivalent passes expected to be applied for the remaining life. The
allowable load to use for Air Force evaluations is to be based on 50,000 passes of the C-17 aircraft.
Criteria for converting allowable loads to PCN values are presented in chapter 8.
f. The PCN value is for reporting pavement strength only. The PCN value expresses the results of
pavement evaluation in relative terms and cannot be used for pavement design or as a substitute for
evaluation.
8. EVALUATION OF ARMY AIRFIELDS AND HELIPORTS. An evaluation indicating the allowable
pass/load relationship and PCN will be made for each aircraft using the airfield. The U.S. Army, as a
result of its evaluations, requires that preliminary overlay thickness requirements be determined for
2-8
Previous Page
