Construction projects in an airport movement area introduce numerous hazards and complexities, as illustrated by a case study at Paris Charles de Gaulle Airport (CDG).
To increase the safety and capacity of strategic taxiways crossing the southwest part of the airside, more than 7.0 acres (2.8 hectares) of pavement are being reconstructed at CDG through a four-year, six-phase program that started in 2010. The project included modifying the design of the entrance taxiways of Runway 08L (THR08) along the runway more than 2,400 ft (732 m) from the threshold. This operation was undertaken from April to June 2012 in a unique phase (called THR08 Reconstruction Program Phase 2), which required balancing safety standards, compliance with certification specifications, preservation of the operational robustness, and limiting constraints on the construction project.
Safety and Performance Challenges
Due to the size of the project and the nature of the construction, it was not realistic to complete the work at night with the runway closed. Only two options were available: closing Runway 08L/26R during the entire Phase 2, or operating the runway with a displaced threshold to make available a sufficient area to perform a large majority of the work, especially stages that cannot conveniently be interrupted (e.g., pouring concrete with slip forms).
The large number of airplane arrivals and departures was not compatible with a lengthy closure of one of the two long runways dedicated to takeoffs.
Moreover, a 24/7 closure would significantly degrade the operational robustness of the runways system.1 Indeed, in case of any incident on the second 13,780-ft (4,200-m) runway, the airfield capacity would be dramatically lower than required to accommodate daily flights. In addition, the heaviest long-haul flights would not be able to take off at their required takeoff weight. And finally, the two remaining 8,860-ft (2,700-m) outer runways would be too short for many airliners if their flight crews requested an emergency return just after takeoff.
So only the second option — a shortened Runway 08L/26R — could meet both operational and safety requirements.
Formal Risk Analysis
Following the recommendations of the International Civil Aviation Organization (ICAO),2 safety management systems (SMS) became mandatory in France in 2008. The related SMS regulation necessitates assessing the impacts on safety of any change to airport operations. During the six years preceding THR08 Phase 2, CDG and the airside community developed a mature process of safety risk management (SRM), for which Phase 2 was an opportunity to effect a complex and critical modification.
The formal SRM of Phase 2 started one year before the construction. The work group included the air traffic control tower (ATCT), project management support, the prime contractor3 and different activities of the Airside Operations and Facilities Department of the airport operator. Airlines were involved later, with the creation of a Pilots-for-SRM Pool that brought human factors expertise into the process.
A comprehensive airport SRM can be divided into five main steps: identification of hazards and risks, assessment of the risks’ acceptability, determination of appropriate mitigation measures, definition of an implementation plan, and preparation of a verification program for safety assurance.
If the SMS acquires and archives information about all safety events occurring on the airfield, these records usually do not date back more than a couple of years, because this practice started to be common only seven years ago. So the safety risk manager has to fill in the missing data using other accessible resources like external databases (e.g., air transportation safety organizations). As we will explain, it is also often relevant to search for inputs from other airports to succeed in reducing the most critical risks.
An overview of risk mitigation performed for Phase 2 comprises addressing the risks of an aircraft colliding with construction equipment after overrunning the runway end safety area (RESA) and of construction activity penetrating the protected approach slopes. One of the key events used during the risk analysis occurred in 2008 at CDG, when the threshold for Runway 09R was temporarily displaced by 4,050 ft (1,234 m) to allow for a partial resurfacing. The remaining available length of the runway was separated from the construction area by blast fences.
Because of the failure of a Boeing 737-800 flight crew to take into account the shortened takeoff runway available (TORA), they took off from Runway 27L, collided with the plastic separator delineating the runway end and then flew low over the fences. Therefore, the possibility must be considered that any flight crew could take off believing that the full runway is available.
The possibility of an aircraft overrunning the RESA also was assessed. A history of excursions after landing or after a rejected takeoff revealed two extreme trajectories. The first was a longitudinal overrun of an Airbus A340-600 at Toronto Pearson International Airport in 2005 that stopped beyond a hypothetical ICAO RESA. The second, in 2000, was the trajectory of a lateral excursion by a Boeing 747-200 beyond the instrument landing system (ILS) Category I runway protections at CDG. The addition of the data from these two runway excursions revealed an area at risk that runs beyond the RESA of Runway 26R westward, and to the southern edge of the parallel Taxiway Tango northward.
Finally, the resulting countermeasures of the analysis for this critical risk were the implementation of a 787-ft (240-m) RESA at the temporary end of Runway 26R, banning of obstacles and human activity on the runway (including the closed section) when it was operational, and suspension of landings on Runway 08L/26R until the workers and mobile machines were moved beyond Taxiway Tango (in case an emergency situation necessitated a landing).
In addition, a prevention plan mitigated possible accident and incident precursors, particularly miscommunication of information to the flight crews. For that purpose, all the taxiway entries to Runway 26R were closed except the first one (Taxiway R1), which offered the longest TORA. Pilots’ situational awareness was reinforced by an illustrated aeronautical information publication (AIP), the designation of Taxiway R1 with the prefix “WORKS” and installation of signage as a reminder of the shortened TORA.
As noted, the risk analysis benefited from the study of safety events outside of CDG. Since April 2011, safety personnel at CDG have collected information about incidents and accidents worldwide. Although local records can be used to assess minor risks, they are inadequate for more-critical events. Indeed, catastrophic events are, fortunately, rare at a single airport and might include only a few types of accidents, requiring the addition of exogenous cases to create a benchmark case study. For Phase 2, more than 200 events were considered, and a dozen were integrated into the risk analysis. This approach allowed us to easily identify risks and precursors that we might otherwise have missed.
The Collaborative Approach
The THR08 Reconstruction Program involved a large number of stakeholders, sometimes with opposite interests and often with different organizational cultures and points of view. The complexity of Phase 2 made more challenging the need to reach consensus, using the differences as a strength, and having all partners working together to ensure the highest level of safety and operational performance.
Phase 2 also required the stakeholders to look more closely into each other’s procedures and practices to understand how we work and interact. This effort also helped us to understand how we could improve the quality and efficiency of these interactions and develop responses to the risks we faced.
All of the preceding was facilitated by the implementation of the airport collaborative decision-making (CDM) standards4 between the ATCT, the airport operator and the airlines, and best practices in airport productivity management, which taught all entities to share in the decisions. Phase 2 also was an opportunity to bring the project management support and the prime contractor more into the SMS. Their direct involvement in SRM meetings enhanced their comprehension of the safety objectives, and of our goals and constraints for the project. Today, these stakeholders even propose mitigation measures.
Operations Management
At CDG, the Airside Control Center (PCR) is responsible for monitoring operations on the movement area, and for overseeing the temporary operational changes. So the PCR is the key to real-time safety assurance, performing inspections of the construction area activities. During Phase 2, the airside operations specialists faced an exceptional number of mitigation measures to be verified. In addition, they had to monitor other major projects, including the extension of the centralized deicing facilities and the completion of a new concourse. This situation required a briefing of the staff on duty, and the addition of special supplements to the certification deviations inspection sheet.
During the nights when the installation and deconstruction of Phase 2 occurred, the PCR staffing was doubled, with one team dedicated to the usual duties and a second one dedicated to Phase 2. This was overseen by the activation of the CDM Command Center (or CDM Cell) in which the airport operator, the ATCT and the airlines decided together how to manage the irregular operations and adverse conditions.
“Plan B”
“Plan B” contingency actions were defined to guarantee the operational robustness of the runway during the work. For instance, the risk that the reduced-length Runway 08L/26R would not be reopened on time was anticipated through a recovery procedure based on the shorter parallel Runway 08R/26L.
Recalling the 747-400 takeoff collision with construction barriers and equipment at Chiang Kai-Shek International Airport, Taiwan, in 2000, the procedure called for the aircraft to proceed to the outer runway through lighted corridors across Runway 08L/26R, preventing the alignment of an aircraft on the wrong runway. To reinforce the visual information, plans were put in place for extra lighted crosses after the last corridor. This procedure was not activated at the time, but we use it now as a standard risk mitigation for prolonged inner runway closures.
Limits of Aeronautical Information
The airport operator and the ATCT made considerable efforts to communicate to the flight crews, going beyond the regulatory requirements. An AIP supplement including temporary ground movement control maps was published and then activated by a notice to airmen. Pilot briefings were performed and a reminder was included on the automatic terminal information service messages. Complementary materials were provided on the website portal of CDG’s airport operations community. Finally, a special controller-pilot phraseology was used from preflight to takeoff alignment.
Despite these measures, the Safety Assessment of Foreign Aircraft inspections by the national Civil Aviation Safety Directorate found that more than a fourth of the flight crews inspected did not have the information provided by the AIP supplement around the first day of the threshold displacement. The controllers stopped three incursions on Runway 26R via the closed-entry taxiways, despite having cleared the aircraft crews involved for R1 WORKS.
The risk awareness of the controllers was increased by special briefings and a local temporary operational order. However, these incidents revealed that the regular aeronautical information alone, as defined by international standards and national or regional regulations, is not sufficient to guarantee correct and effective diffusion from the airport operator to the cockpit.
Beyond Phase 2
Phase 2 of the TH08 Reconstruction Program demonstrated the force of formal SRM as the main tool in managing airside changes and as a major tool of airport project management. This process was inspired by reality on the ground and designed in a proactive and pragmatic way. To achieve the intended level of risk mitigation, safety risk managers may conduct their study in a continual feedback loop between the theory and the operations. Indeed, a risk mitigation plan is useless if it cannot be deployed and verified, or if this plan is not updated after a safety event reveals an insufficiency.
The merger of the airport operator’s and ATCT’s risk analysis, determined at CDG after Phase 2, created valuable synergies in time saving (no redundancies), hazards identification (complementary aspects of both approaches) and risk mitigation (coherent and comprehensive action plans).
For project management, the CDM spirit among the stakeholders significantly facilitated the information sharing and the reciprocal understanding of difficulties for each participant. One simple, efficient CDM action was involving the ATCT in the acceptance inspections at the beginning and the end of the construction. It was followed by a multiple-party approval of the modified movement area.
Finally, Phase 2 highlighted the relevance of exchanging experiences and best management practices inside the airport community and adding exogenous events to the risk analysis. For this purpose, we developed collaborations with other airports and institutions, especially in North America.
We met in 2012 with Jim Krieger, chairman of the Airport Construction Advisory Council (ACAC), with whom we compared the lessons learned from operations on temporarily shortened runways at CDG and Chicago O’Hare International Airport. In particular, we agreed that in facing the same hazards, similar responses spontaneously appeared at both airports5 — proof, if needed, that safety is the common priority of our industry.
Gaël Le Bris is airside development manager for Aéroports de Paris at CDG. He is safety risk manager and leads the activity of economic and technical benchmarking for his department, with a special focus on establishing collaboration with the North American airport community.
Notes
- CDG has two independent north and south complexes of two parallel runways.
- ICAO. Amendment of Annex 14, Volume 1, Airport Design and Operations, Chapter 9.3. November 2005.
- At Aéroports de Paris, these functions are internalized through two divisions of the parent company.
- CDG was granted the Airport Collaborative Decision Making (A-CDM) certification by Eurocontrol in 2012. For further details about A-CDM, see the Airport CDM Implementation Manual of Eurocontrol.
- Rosenkrans, Wayne. “What’s on Your Runway?” AeroSafety World Volume 7 (July 2012), pp. 16–19.