In-flight landing distance safety margin may be inadequate

Safety issue

Safety issue description	Civil Aviation Order 20.7.1B stipulated that a 1.15 (15 per cent) safety margin was to be applied to the actual landing distance for jet-engine aircraft with a maximum take-off weight greater than 5,700 kg. This safety margin may be inadequate under certain runway conditions, which increases the risk of a runway excursion. The corresponding guidance in Civil Aviation Advisory Publication 235-5(0) had not been updated to account for this.
Issue number	AO-2015-046-SI-05
Issue owner	Civil Aviation Safety Authority
Transport function	Aviation: Air transport
Issue status	Closed – Adequately addressed
Date issue released	18/09/2018
Issue status justification	The ATSB is satisfied that the revision of Civil Aviation Advisory Publication 235-05 will encourage operators and pilots to apply additional conservatism to the in-flight safety margins for landing distances when the runway conditions have deteriorated. This will address the safety risk issue with regard to the margins being inadequate under certain runway conditions..

Safety action

Action type	Proactive action
Action number	AO-2015-046-NSA-011
Organisation	Australian Civil Aviation Safety Authority
Action date	18/09/2018
Action description	In response to this safety issue, the Civil Aviation Safety Authority advised that the advisory guidance material, Civil Aviation Advisory Publication 235-5(0) - New performance provisions for Civil Aviation Order 20.7.1B and Civil Aviation Order 20.7.4 was published to accompany the May 2014 amendment to Civil Aviation Order 20.7.1B. The subsequent August 2015 United States Federal Aviation Administration advisory safety alert (15009), which warns aircraft operators and pilots that the advisory data for wet runway landings may not provide a safe stopping margin under certain conditions will be evaluated for incorporation into the advisory material contained in Civil Aviation Advisory Publication 235-5(0), with an aim to incorporate any changes prior to the end of March 2019.
ATSB response	The ATSB notes the Australian Civil Aviation Safety Authority’s intention of incorporating additional safety information regarding the in-flight safety margin into Civil Aviation Advisory Publication 235-5(0). The ATSB will monitor the Civil Aviation Safety Authority’s progress and assess the safety issue on completion of amendments made to this publication. Correspondence Landing in very wet conditions Date received: 1 October 2020 Closed In October 2020, the Civil Aviation Safety Authority published Civil Aviation Advisory Publication 235-05 v2.0 - New performance provisions for Civil Aviation Order 20.7.1B and Civil Aviation Order 20.7.4. The revision cited research conducted by the United States Federal Aviation Administration, which indicated that 30 to 40 per cent of additional stopping distance may be required in certain circumstances when the runway is very wet, but not yet contaminated. As such, CASA recognised that the landing distance safety factors (margin) stated in the publication ‘may not provide adequate stopping distance in very wet but not yet contaminated runway surface conditions’. Consequently, in order to manage some of the risks associated with operating on very wet runways, CASA recommended that operators consider these margins to be a ‘minimum value’. In addition, CASA also suggested that operators and flight crew consider using a medium or fair braking action, or increase the in-flight landing distance safety margin if moderate or heavy precipitation was expected for landing.
Action status	Monitor