Can a Runway Shrink

Background:

The management of an Australian airport asked Aspirion to investigate reports that its runway needed to be lengthened as it could not accommodate a fully-laden Boeing 737-800 when the runway was wet. The assignment included providing solutions to the problems, if any, that might be uncovered.

The centre section of the runway had been grooved to assist with operations when wet, but as it was reported to us, that the airline(s) considered there was a predisposition to hydroplaning as a result of the inadequacy of this grooving. The cost of extending the runway by the suggested 200-metres, bounded at both ends by bodies of water, was estimated at $12-million.

Investigation:

Aspirion started its investigation by reviewing data from Airservices Australia, the consulting engineers retained by the airport and the airport manager, which supported the viability of the use of the runway. The next step was to consult Boeing in Seattle to run some computer studies using a generic 737-800 on the wet grooved runway at the airport. Afterwards we examined the CASR Part 139 standards, which revealed that a wet grooved runway could be considered ‘dry’ provided it had appropriate surface texture characteristics – which it did – and provided there was no standing water or pooling. Here we were dealing simply with a ‘wet’ grooved runway. So, why was there a problem reported?

The investigation took us then to the technical staff of the airline that had reported this issue in order to gain a better understanding of the problem. We reviewed their operating policy as well as Australian regulations covering these types of cases. From all of our discussions we did not uncover any problem unique to the airport’s runway, or anything that would effect operations on a wet (but uncontaminated) runway. We reported back to airport management, sought and obtained their permission to continue our investigations and began the next stage.

Meeting with the airline’s flight operations engineering management we began to uncover the reason for the problem. We found that a few years earlier, the airline changed its policy following an accident at another (overseas) airport where a Boeing 747 overran the runway during a tropical storm.

The official investigation into that accident revealed many contributing factors. However, one revelation was that the runway was not grooved.

The airline later found that another major airport had also not been cleaning its runway grooving and, on this basis, it decided to change its policy in respect of a wet grooved runway being considered ‘dry’. In most airports this would have made little noticeable difference as their runways were long enough to accommodate the change in policy. However, such was not the case at our client airport.

Solution:

Thereafter, our negotiations with the airline’s technical management and senior pilots were positive. They agreed that if they could be assured the runway grooving was optimal at all times they would be agreeable to a reinstatement of the previous policy that allowed ‘credit’ for the runway grooving.

Aspirion identified and examined a cost-effective cleaning process that would enable these safeguards to be implemented. They are presently in the process of being implemented and signed-off by the airline. After this, the airport will return to full productivity, with no need to spend $12-million in avoidable upgrade work.