SA Airlink E135 at George on Dec 7th 2009, overran runway

Last Update: August 23, 2012 / 15:11:06 GMT/Zulu time

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Incident Facts

Date of incident
Dec 7, 2009

Classification
Accident

Airline
SA Airlink

Aircraft Type
Embraer ERJ-135

ICAO Type Designator
E135

South Africa's Civil Aviation Authority (SACAA) released their final report concluding the probable cause was:

The crew were unable to decelerate the aircraft to a safe stop due to ineffective braking of the aircraft on a wet runway surface, resulting in an overrun.

The SACAA added analysis stating that although the runway had been grooved, the grooves had not been applied according to international standards and stated: "The slots were cut at 45° to the centreline, and ran from the centreline to the runway edge for a distance of 120 m westward from a point 36 m west of the western edge of runway 02/20. They were on average 10 mm wide and 55 mm deep, spaced at 1,4 m intervals (measured perpendicularly), and cut only on the right-hand side of the runway. As a result of the pressure of numerous landings, the asphalt had crept and several slots had partially closed up. Cracks had also formed. According to aerodrome officials, the slotted area had been a cause of concern because of inadequate drainage during rainy conditions."

The SACAA analysed that friction tests of the runway surface and actual aircraft performance tests conducted by the SACAA did not match. Although the friction test indicated good braking action substantially above the required limit for good braking action, the aircraft exceeded required limits for landing by 6% and on rejected takeoffs by 28%. A Boeing 737-400 had been used for these tests, which other than the Embraer also featured thrust reversers with the crew employing primary focus on stopping the aircraft as quickly as possible. The exceedance of the aircraft in both landing and rejected takeoff is believed to be much higher had the thrust reversers not been used during those tests.

The investigation drew comparisms to the runway condition at Bristol, see Report: Various aircraft at Bristol between November 2006 and January 2007, slippery runway and further elaborated that the unevenness of the runway permitted water puddles to form on the runway.

The SACAA further analysed with respect to fog spray sealant: "The bituminous fog-spray thus 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 the runway surface (or be channelled in the case of a grooved runway surface) as soon as possible to allow for proper tyre-to-runway contact. The presence of water will decrease the braking force that the aircraft tyres can generate. Surface texture, especially existing micro and macro-texture, has a significant influence on the wet surface friction characteristics of pneumatic tyres."

As result of the accident and subsequent investigation the operator of the aerodrome re-surfaced the runway again, which was completed by May 26th 2010, which permitted the regulator to revoke limitations of runway use when wet.

The investigation analysed they were concerned with the regulatory oversight of the aerodome, as the Civil Aviation Authority had conducted a operator license renewal audit, during which no non-compliance affecting the status of the aerodrome was found. The runway resurfacing was still in progress at the time, the fog spray sealant being used for the runway surfacing however did already raise concern at that time. The SACAA continued: "The fact that no non-compliances were listed 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 the checklist (CA139-18). The investigation team found the checklist to be lacking critical content, especially with reference 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."
Incident Facts

Date of incident
Dec 7, 2009

Classification
Accident

Airline
SA Airlink

Aircraft Type
Embraer ERJ-135

ICAO Type Designator
E135

This article is published under license from Avherald.com. © of text by Avherald.com.
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