The South African Civil Aviation Authority’s (SACAA) Accident and Incident Investigation (AIID) Division has, in a new report, released today, fingered a fog spray sealant applied to the runway at George airport in November last year for a planecrash in December.
“The use of the fog spray sealant can be considered to have been the primary probable cause of the occurrence of aquaplaning. In this regard it is considered imperative, in the interest of aviation safety, that the service provider (ACSA, Airports Company SA) improve the runway surface at George Airport and implement corrective actions to allow aircraft operations under wet conditions to return to normal,” SACAA says in a second interim report regarding its probe of the December 7 incident when a South African Airlink Embraer 135 Commuter Jet (ZS-SJW) with 30 passengers and three crew members aquaplaned on the runway while landing in bad weather. The aircraft came to rest 200 metres past the runway just beyond the perimeter fence of the airport, its nose across the R102 road that skirts the airport.
SACAA in February said it was perplexed by the incident. “A friction test was … performed on Monday, February 15 and the results indicated that the runway friction is within the prescribed limits,” SACAA said in a statement. “This presents a challenge when viewed against the fact that the data from the aircraft flight data recorder indicates that all systems appear to have functioned normally (inclusive of the brakes and the anti-lock braking system) and the approach and landing profiles and speeds were within normal limits. It is clear that something had to cause the overshooting of the runway at the time and the cause has to be identified in order to prevent a recurrence of the same accident.” George is the country’s sixth-biggest airport with 600 000 passengers a year.
The SACAA says the digital flight data recorder data has confirmed the aquaplaning, which is also verified by the damage observed on the aircraft tyres. “Overall, it would appear that the application of the fog spray sealant extensively degraded the surface friction coefficient of the runway surface during wet conditions, thereby allowing the onset of aquaplaning and thereby inhibiting the application of adequate braking pressure by the anti-skid system to stop the aircraft within the certificated distance.”
As a result, the AIID has asked the Commissioner for Civil Aviation to issue a NOTAM (Notice to Airmen) restricting the use of runway 11/29, the runway concerned, at George by transport aircraft over 5700kg in weight when the runway is wet. It also recommended that the NOTAM remain in force “until such time as adequate friction/texture treatment, such as grooving, has been implemented over the entire runway length and width” and that ACSA be required to conduct a risk assessment on the lack of an end safety area on the runway, “and if found necessary, to incorporate some form of arresting mechanism.”
The AIID further recommended the Director for Civil Aviation consider banning the use of sealants on runway surfaces. “In this regard it is considered imperative, in the interest of aviation safety, that the service provider (ACSA) improve the runway surface at George Airport and implement corrective actions to allow aircraft operations under wet conditions to return to normal. A further suggestion was that the Aerodrome Department of the SACAA be strengthened to ensure adequate skills and knowledge to enable the comprehensive safety oversight over the certification of aerodromes and the maintenance of certification standards. “This should include the establishment of an office that deals primarily with runway safety,” the report says.
SACAA says a final report can now be expected in September.
“Notwithstanding the above, the SACAA holds the view that runways in SA are generally in a good state and compliant with the ICAO (International Civil Aviation Organisation) physical requirements,” the statement says. “The SACAA also wishes to reiterate that the objective of an accident investigation is to establish the cause(s) of the accident and to take steps to prevent a further occurrence. As such, the objective is not to apportion blame or liability. Moreover, the SACAA values accident reports as they serve as mechanisms that point to any shortcoming; and as such enables the Authority to continuously upgrade its oversight systems. In this regard, the SACAA will carefully study this Interim Report as well as the Final Report and where necessary introduce changes to address potential shortcomings.”