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Measurement of pavement structural properties via the falling-weight deflectometer (FWD) is an accepted practice in highway pavement testing. FWD’s are becoming more commonplace in the airport community. Despite the increasing popularity of FWD devices, the FAA does not currently issue specifications for their use on airport pavements. FAA Advisory Circular 150/5370-11: "Use of Nondestructive Testing Devices in the Evaluation of Airport Pavements" was issued in 1976 and has not been updated to include current FWD technology. Falling-weight deflectometers are often preferred over destructive methods of testing because they are much faster than destructive tests and do not entail the removal of pavement materials. In addition, the testing apparatus is easily transportable. Pavement properties are "back-calculated" from the observed dynamic response of the pavement surface to an impulse load (the falling weight). The disadvantage of the FWD method is that its results are often dependent on such factors as the particular model of tester used, the specific testing procedure, and the method of back-calculation. It is therefore in the interest of the airport community to develop a standardized set of procedures for FWD testing and analysis that is applicable to all of the major equipment manufacturers.

Emphasis will be placed on verifying repeatability of FWD results, linearity of load impact, plate size and the development of improved back-calculation methods.

Most data collected by the FAA's Falling Weight Deflectometer is populated into the National Airport Pavement Test Facility (NAPTF) database.

The following software program is provided for backcalculation of FWD data. After downloading and unzipping the file, the setup file should be run to install the program on your computer. This software program is offered free of charge and accompanying documentation is currently being prepared. This software program is provided for evaluation purposes only.

Note: For Windows 2000 Professional, you may need to install Service Pack 3 before you setup the backcalculation program.

FAA Backcalulation Software Program
July 2002
In Zip format, size: 1.5MB

This program is furnished by the Government and is accepted and used by the recipient with the express understanding that the United States Government makes no warranties, expressed or implied, concerning the accuracy, completeness, reliability, usability, or suitability of any particular purpose of the information or the data contained in this program or furnished in connection therewith, and the United States Government shall be under no liability whatsoever to any person by reason of any use thereof. This program belongs to the government. Therefore, the recipient further agrees not to assert any proprietary rights therein or to represent this program to anyone as other than a government program.

If you have comments or issues with this software program, please contact the NDT project lead

The backcalculation software program is compressed in a Zip format. You can download a free evaluation copy of WinZip by clicking on the following image.

The published documents listed below are in Adobe Acrobat (*.pdf) format and are available for download. You will need Adobe Reader software to view these documents. Adobe Reader is free and available for download.

Analysis of Nondestructive Test Data on Flexible Pavements Acquired at the National Pavement Test Facility
Authors: Roy D. McQueen, Wayne Marsey and Jose M. Arze
August 2001

Analysis of Falling Weight Deflectometer Tests at Denver International Airport
Authors: May Dong, Gordon Hayhoe

Verification of Curling In PCC Slabs At FAA National Airport Pavement Test Facility
Authors: Edward H. Guo, Wayne Marsey
August 2001

Comparison Between Falling Weight Deflectometer and Static Deflection Measurements on Flexible Pavements at the National Airport Pavement Test Facility (NAPTF)
Authors: Navneet Garg, Wayne Marsey
May 2002

Contact Project Lead: Albert Larkin

Last Update: 02/12/2013