The South African Civil Aviation Authority (Sacaa) has released its final report on the SA Airlink incident in 2009 at George Airport and comes to the conclusion that it was not possible for the crew to bring the aircraft to a safe stop, due to the wet runway surface.
The incident happened on 7 December 2009 when an Embraer 135-LR aircraft overran the runway, burst through a perimeter fence and ended up on a public road. The final report confirms the findings of the previous interim report, in which the surface of the runway was also blamed.
The Airports Company of South Africa (Acsa) has said it would comment once the report had been studied. A spokesperson for Sacaa confirmed that the final report, released on Monday replaces the interim report published earlier. The aviation authority confirmed that George Airport currently "meets all requirements as per international standards", but said it did not wish to comment on questions raised in the report, as Sacaa has been subpoenaed and is expected to be called to testify in court.
The report states that although the runway had been grooved for water to run off, the grooves were not according to international standards. Grooves were cut only on the right-hand side of the runway and as a result of pressure from numerous landings, the asphalt had crept and several grooves had partially closed up.
Cracks had also formed and the grooved area had been a cause of concern for airport officials because of inadequate drainage during rainy conditions.
The landing was captured by three surveillance cameras - on the airport building, facing the apron and pointing towards the runway. According to the reports by Air Traffic Control (ATC), there was nothing untoward about the touchdown and no communication from the crew to indicate problems.
Once ATC realised the aircraft had veered to the right and off the runway, the crash alarm was activated and the aerodrome rescue and fire-fighting personnel responded swiftly.
The pilot stated there was nothing abnormal about the touchdown and he applied braking action. The 'pilot not flying' (PNF) described the landing as smooth and said that he had checked that the spoilers had deployed after touchdown. When rea-lising there was a problem, he tried to assist with the braking.
According to the flight data recor-der, the spoilers opened two seconds after touchdown and remained open until the aircraft came to a halt at the bottom of the embankment.
Sacaa concluded that friction tests of the runway surface and actual aircraft performance tests conducted at George Airport afterwards, apparently did not match. Although the friction tests indicated good braking action, substantially above the required limit for braking, the aircraft exceeded required limits for landing by 6% and on rejected takeoffs by 28%.
Sealant still questioned
The Sacaa report also again refers to the likelihood of the fog spray sealant contributing to the accident. "The bituminous fog-spray reduced the macro-texture available for water to dissipate from the runway. It should be kept in mind that water is not a compressible substance and needs to flow off or be channelled off in the case of a grooved runway surface as soon as possible to allow for proper tyre-to-runway contact. Surface texture has a significant influence on the wet surface friction characteristics of pneumatic tyres."
The investigative team stated they were concerned with the regulatory oversight of the airport, as the Civil Aviation Authority had conducted an operator licence renewal audit, during which no non-compliance at the airport was found.
The runway resurfacing was still in progress at the time, but the fog spray sealant being used for the runway surfacing did raise a concern at the time.
The report continues: "The fact that no non-compliance was found could be attributed to the fact that the audit team did not require any additional testing to be conducted on the runway and acted purely on the data required from their checklist.
"The investigation team found the checklist to be lacking critical content, especially with refe-
rence to the rehabilitation process of a runway, which falls outside its scope.
"The checklist did not require any additional test data, such as a runway friction test, to ensure that aircraft safety was not compromised."
"This again brings into question the issue of the aviation authority being both the regulatory body and the investigating authority," says aviation analyst Linden Birns. "In the UK, USA, Canada and France there is total separation between the regulatory and investigating authorities."
* Na 'n omvattende ondersoek is die finale verslag van die SA Lugvaartowerheid oor die ongeluk by George-lughawe in 2009 vandeesweek gepubliseer. Die bevinding is dat die oorsaak die oppervlak van die aanloopbaan en die nat weer was.