This guidance presents the new rational and performance-based French methodology for airfield pavement thickness design. It is applicable to new flexible pavements, and incorporates the latest developments from pavement mechanics. The verification of pavement structures is based on a mechanical design as well as a design against frost-thaw.
This document provides a technical reference frame allowing adressing airfield pavement design studies with a common approach. This is why this guidance not only details pavement thickness design process, but also provides recommendations about pavement subgrade, surface layer and pavement materials.
This methodology is meant to be applied for French airports as well as all airports worldwide, local environment and conditions (climate, geotechnics, pavement management policy...) being adjustable through design parameters. The implementation of this guidance is done with the software Alizé-Airfield Pavements, distributed by the company ITECH.
The decelerometer is a discontinuous measurement device of runways coefficient of friction. It is used especially by airport runway inspectors to characterize the surface condition of a runway in poor weather conditions.
The decelerometer is easy to use, relatively inexpensive and less bulky than most other devices.
Although it is commonly used in airports, there are only few recommendations or guidelines on its setting up and operational use. This technical information note solves this lack of information by providing recommendations so that runway inspectors can use this device to obtain accurate measurements.
The recommendations have been established from the current state of the art and from experiments conducted by the STAC.
The present technical guidance aims at providing a methodology for pavement testing using HWD. It gathers recommendations relative to operational survey and data analysis, based on an advanced dynamic modeling.
The operational recommendations include all information about platform survey and test carrying out. In particular, the requirements to meet before pavement testing and data analysis are respectively described. They consist in requirements relative to the device, in necessary complementary information about the pavement and in the traffic data.
The recommendations relative to the data analysis gathers the description of the mechanical modeling and its parameters, as well as the one of the associated backcalculation process developed.
All parts of the guide have been validated, numerically or using in-situ measurements. Last part of the document is dedicated to illustrations using real case studies.
Aircraft operational performances, at landing or take-off, are strongly dependant on runway surface conditions.
Bad weather conditions may severely degrade runway surface condition. For obvious safety reasons, when such events appear, methods and means must be implemented to characterize runway surface condition and to provide pilots with relevant information.
This characterization consists in identifying nature of contaminant, in measuring or assessing depth and coverage of contamination, and in quantifying the friction. This document provides guidance to assist airport operators in developing and implementing procedures relative to the monitoring of runway surface conditions under adverse weather conditions.
This technical guidance sets out the new French design methodology for new flexible airport pavements, implementing the last findings in pavement engineering. The validation of pavement structures is based on a mechanical design which is completed by frost-thaw verification.
This document constitutes a technical frame of reference which enables comprehending pavement design studies at best and with a unique approach. This is why elements relative to pavement foundation, surface course and pavement materials, are tackled complementarily to the design procedure itself.
The method has a vocation to be applied not only to the French airfields, but also abroad. Local specificities (climate, geotechnics, infrastructure management…) may be implemented by designers through various parameters.
Evaluation of measurement uncertainties is essential to assess measurement reliability and to be able to compare results to each other or to reference values. STAC has had two devices, of IMAG conception, for several years to measure runway friction. These devices have already demonstrated their repeatability and reproducibility. To improve the quality of STAC work, it was necessary to study and to quantify uncertainties in the field of friction measurements.
The evaluation of measurement uncertainty was conducted in accordance with the recommendations of the GUM (Guide to the expression of uncertainty in measurement). The methodology is divided into four steps:
As no physical model is currently available, an experimental approach has been adopted for this study.
Three values of the expanded uncertainty have been obtained, corresponding to each of the test speeds. The relative weight of each factor of influence in the overall uncertainty was studied to determine the best choices and ways to improve reliability of friction results.
The IMAG, automatic skid resistance friction trailer, was designed and patented by French civil aviation authority. It measures in operational conditions, mainly in winter, the characteristics of skid resistance of runways and allows pilots to know the operating conditions of these areas.
This device is used by the STAC as a national reference vehicle in the Certification process for self-wetting continuous friction measuring equipment.
Aircraft pavements are subject to periodic monitoring by using the method of the Service Index. This method requires a systematic survey of surface distress, whose analysis is used to calculate the superficial, structural and overall service indices of the pavements.
These surveys, which are currently performed by operators on foot, prove long and extremely resource intensive and besides may cause disruption to the operation of the aerodrome.
To improve the performance of the service index surveys and reduce or eliminate the hindrance caused to the airport operations, the STAC has initiated an approach with the Regional Laboratory of Civil Engineering of Rouen (Normandy CETE Centre) to automatise the method based on existing high speed survey equipment used in the road sector in France and abroad.
The report presents the findings of the feasibility study and experimentation carried out in 2009 and 2010
This downloadable document is the version-1 of the HTPT technical report. The reader will note it is planned to establish a version-2 that will include complementary analysis
This report describes an outdoor full-scale test led by Airbus S.A.S in partnership with the French authorities DGAC-STAC, LCPC, LRPC-T, MICHELIN and VANCOUVER2 to improve experimental and theoretical knowledge related to the effects of aircraft internal tire inflation pressure on the behavior of and damage to flexible pavement.
Since some modern aircraft have tire pressures exceeding 15 bar, the tests focus on pressures from 15 bar to 17.5 bar.
The experimental pavement located on the Toulouse-Blagnac airport in France includes up to seven different test sections, representative of current airfield flexible pavement world-wide. Variant parameters from one section to another are thickness of AC surface layer and its performance in respect of rutting, and surface treatment as grooving. The structure has been designed according to the French airport pavement design method, for 10,000 passes of B747-400 gear.
The aircraft simulation vehicle drives four dual-wheel gears sufficiently spaced enough in order to prevent from any interaction between them, making it possible to test two different tire pressures (15 and 17.5 bar) and two weights per wheel (ultimate weights, 28.7 and 33.2 tons) simultaneously.
The seven test sections are instrumented to measure resilient strains, and resilient and permanent displacements (rutting).
This report presents the obtained results and their scope.
In accordance with ICAO standards, the French rules require aerodrome operators to assess regularly intrinsic friction characteristics of runway using a self-wetting continuous friction-measuring equipment (CFME).
French rules define a minimum friction level, below which the runway is considered as slippery, corrective actions have to be taken to improve runway friction characteristics and pilots have to be informed of such conditions.
All self-wetting CFMEs used for construction and maintenance purposes on French airports have to be certified by the State. The certification intends to ensure aerodrome operator that the CFME performs with reliability and consistency. It also harmonizes friction values between different devices and ensures a uniform acceptance of the minimum friction level.
The certification process consists in correlation trials between the applicant device and the reference device, owned by the French Civil Aviation Technical Centre (STAC). The performances of the applicant device in terms of repeatability and consistency of friction measurements are checked.
A device reaching requirements for certification is then correlated to the reference device of the same type and is delivered with a certificate. This certificate is valid for two years and must be renewed at the end of this period.
Operational friction means assessment of runway surface friction characteristics during poor meteorological conditions, when runway is covered with water, snow or ice. The assessment of operational friction characteristics and the nature of information to be transmitted are not supervised by rules or standards but by ICAO recommendations.
This statement led STAC to carry out an extensive information-gathering study to establish state-of the-art-practices. Relevant ICAO documents have been reviewed and two specific surveys have been sent to airport manager and air traffic control services from both French and foreign airports. Personal contacts with professionals from aeronautical industry (aircraft manufacturers, airlines, airport managers, air traffic services) have been established to flesh out the study and to refine analysis.
The survey has had a high response rate from French airport operators and French air traffic controller, showing their interest for this thematic. The survey has highlighted the following points:
The Heavy Weight Deflectometer (HWD) is viewed world wide as the most appropriate device to assess the bearing capacity of airport pavements.
The backcalculations are performed from the pseudo-static deflection bowls. These methods have shown limitations. Actually they use only part of available information, and the static modelling is far from the reality of the test.
The objective of the study is to develop an advanced method for the assessment of flexible pavements using HWD tests data. This work has been realized through a thesis by Michaël BROUTIN, chief of STAC program "Pavements assesment", supervised by Michel FRÉMOND, from LCPC.
Michaël BROUTIN defended his thesis on June 11th, 2010 at the LCPC in Paris.
The document outlines the recommended interventions for maintenance and rehabilitation of grass airfield pavement and their surroundings.
Routine maintenance and rehabilitation of runways and taxiways are presented. For each type of worksite, the purpose of the operation, its prerequisites and how to act are described.
The document describes the characteristics and mixture designs commonly used in France for all hot bituminous mixtures intended for surface courses or base courses, and for surface dressing and cold coat material. It links the earlier French terminology to the designations defined by NF EN European standards.
Compared to the previous version, the guide introduces a new concept called «aircraft group». This concept is more representative of the impact made by an aircraft on an airport pavement than simply its weight. It is arrived at by taking into consideration the aircraft’s landing gear configuration and tyre pressures.
The document also includes a number of appendices in table form. This approach is intended to help the designer to determine which products to use, and to determine their mechanical performance
Determination of ACN (Aircraft Classification Number) is based on an international standard that applies to aircraft with a mass on the ramp greater than 5700 kg.
ICAO has approved on October 16, 2007 the changing of the numerical coefficients entitled "Alpha factor" involved, for flexible pavement type, in calculating the ACN of the aircraft.
The ICAO decision led to recalculate the ACN "flexible" of landing gears of aircraft which have a total of at least four wheels.
The visual survey of surface damage and its interpretation are the first step of investigation that an airport operator must take to assess the level of degradation of the runways he has to maintain to ensure flight safety and adequate pavement asset management.
In addition to its purpose as catalog, this guide is a tool:
Guidelines are also available for flexible pavements to determine the types of works and response times for maintenance.
Aircraft pavements have special characteristics which differentiate them from road pavements although materials and methods of implementation are virtually identical.
This paper presents various types of pavements and their methods of design, evaluation and maintenance, auscultation. It contains a table comparing the characteristics of airfield vs. road pavements.
The purpose of this study is to test several pavement shoulder structures in order to meet the requirement imposed by New Large Aircraft (NLA).
International Civil Aviation Organization identifies three potential functions for shoulders :
The two first functions have an impact on bearing capacity ; so, structure of shoulders could be designed in correlation with subgrade and load of aircraft considering at least one pass.
Introduction of New Large Aircraft with a load by wheel close to 25-30 t conducted STAC (French civil aviation technical center) to lead an experimentation to compare some shoulder structures.
An experimental shoulder with five different structures has been tested with a NLA Wing Landing Gear module.
This paper describes the experimentation with context, site selection, test section construction, test procedures and results.
This experimentation showed one of tested structures was able to support at least one pass of NLA gear. Then, this shoulder section was tested with the load applied during 18 hours. No permanent deformation was observed.
Airfield pavement maintenance requires periodic measurements of pavement state indicators. These measurements may be heavy, inconvenient and costly for an airport operator.
Experience demonstrates that a simple visual survey of surface damage allows characterising pavement state. STAC has thus developed a visual pavement distress inspection method to allow defining a simple indicator characterising the pavement conditions.
A guide has been published to help users to gain practice and to ensure collected data are well interpreted.
This guide is intended to assist agencies in charge of winter services on French aerodromes on how to meet the three following objectives:
Longitudinal airfield pavement irregularities are obviously felt by taxiing aircraft. They may be prejudicial to the good performance of the aircraft on their optimal trajectory.
This note aims to present the new specifications of longitudinal evenness on new wearing courses applicable to airfield pavement construction contracts.
In the context of the NLA development, Airbus Industrie proposed the A380 program, an aircraft whose mission is to transport 555 Pax over 7920nm (A380-800). The aircraft sets the standard for new Code F airports (80 m wing span, Landing Gear (L/G) Outer Wheel Span >14 m) and will feature 20 Main Landing Gear wheels for MTOW ranging from 560t to 600t with development potential beyond 640t.
The issue of pavement compatibility was considered to be fundamental to the programme, especially as the current ACN/PCN method, was shown to have reached its limit of reability with the unpredicted failures of pavements subject to 6 wheel bogie loads. The pavement designers from Airport and Airforce Bases Engineering Dept. (Direction Générale de l’Aviation Civile - Service Technique des Bases Aériennes DGAC-STBA), ICAO ACNSG European voting member, the pavement structure and materials experts (French Laboratory for Civil Engineering – Laboratoire Central des Ponts et Chaussées LCPC) and the European aircraft manufacturer AIRBUS INDUSTRIE felt the need for an ambitious research program aiming at defining more accurate pavement design methods.
AIRBUS INDUSTRIE set up in partnership with STBA and LCPC the experimental part of this research via the A380 Pavement Experimental Program to be able to bring in the pavement compatibility issue into the Landing gear (L/G) configuration selection decision process.
In 1981, ICAO proposed to its member states the ACN-PCN method as a standardized system to publish the information on the strength of airfield pavements.
This method results of a desire to unify the standards for accommodation of aircraft globally. It resides in a simple comparison between two classification numbers, one assigned to the pavement (PCN – Pavement Classification Number), the other to the aircraft (ACN - Aircraft Classification Number).
This note aims to explain what the ACN-PCN method is and how it is used in France.
This guide is intended for the engineer of a project involving the construction of concrete airfield pavement and aims to facilitate the drafting of specifications, the assessment of the technical proposals of contractors and the organization of the monitoring and control of the work.
It also sheds light on appropriate construction practice with reminders about the rules of art and guidance on internal and external quality controls.
Considerable progress has been made in the fight against rising cracks for both new aircraft pavements and others, provided that the method chosen is appropriate to treat the problem. Certainly the reappearance of the cracks is only deferred, but that postponement is very significant particularly in terms of maintenance costs.
This guide is for designers and project managers to assist them in choosing the most appropriate solution. It explains:
The French design method for airfield flexible pavement provides a total equivalent pavement thickness. The actual thicknesses of materials are determined by assigning each material a coefficient of equivalence representative of its mechanical properties.
This note recalls the principles of the design method and presents the testing by the STBA of experimental pavements built with high modulus bituminous concrete (BBME) and high modulus bituminous mixes (EME) which validates the use of these materials in airfield pavements.
To maintain and make best use of its pavement assets, the manager of an aerodrome should:
To meet these needs, this paper presents the tools and special testing equipment designed by the STAC to measure bearing strength, friction and evenness of airfield pavements.
Construction and repair of the joints between cement concrete slabs of airport pavement raise specific questions.
This guide is for use by prime contractors and agencies in charge of construction and maintenance. It describes the products and methods used for lining those joints and indicates the necessary checks and precautions.
In 1981, ICAO proposed to its member states the ACN-PCN method as a standardized system of communication of the information on the strength of airfield pavements.
This method results of a desire to unify the standards for the accommodation of aircraft globally. It resides in a simple comparison between two classification numbers, one assigned to the pavement (PCN – Pavement Classification Number), the other to the aircraft (ACN - Aircraft Classification Number).
This guide aims to describe the method and make accessible the ACN-PCN concept.
The technical guide for airfield pavement structural design and allowable load determination consists of two volumes: the technical guide itself with appendices and a practical structural design manual.
The technical guide presents the overall approach to the design of flexible and rigid pavement and the determination of allowable loads.
The second volume provides further information for the use of the design methods (calculation of pavement thicknesses, study of the subgrade bearing strength and calculation of the depth of frost in the pavement). It presents graphs for general-type landing gear and structural design charts for major commercial aircraft as well as detailed examples of standard or optimized design, verification of freeze-thaw structures and pavement strengthening.
Updated Dec. 13, 2016