tribo, et al, I have read the JAA documents. Both refer to Part 25 certification rulemaking and deal with ‘ideal’ conditions and ‘theoretical’ performance.
Many of the respondent’s comments relate to the disparity between certification proposals and actual operations; this follows many well established, but erroneous traditions in certification, which in this instance could yet again widen the gap between regulation and operations.
The proposals appear to be enabling operations beyond reasonable safety whilst attempting to provide data that are more accurate. The assumptions that the operator / pilots will have, and will use, guidance material falls short of reality, whilst guidance might be noted in part 25, no proposals appear to be planned for JAR-OPS etc, and also why hide information away in another ‘approved document’. Unless the guidance is spelt out in unequivocal terms then pilots will continue to be unaware of the assumptions made in certification. Similarly, those replies that state that ‘the issue is beyond the scope of the NPA’ show the weakness of the proposal and the processes that should improves safety.
I reinforce the point that it extremely disappointing that the FAA is not considering rulemaking, yet are party to JAR comment procedures. The FAA’s position does little to reduce the problems of differing standards and alternate terminology in use around the world.
As I interpret the comments, whilst normal landings have a safety margin of 1.67 /1.92 for jet aircraft on a dry/wet runway, on top of the measured landing distance, the contaminated data will only have a 1.15 factor above a theoretical distance (plus an arbitrary allowance by local authority or operator). The conditions on a contaminated runway are unlikely to match the assumed certification standard. A runway covered in dry snow may soon become rutted and slushy, or even ‘contaminated’ by de-icing fluid from aircraft taking off.
Thus, neither the theoretical distances nor the safety factor may provide a realistic stopping distance. Who can believe that a landing distance not less than the factored wet distance has the same safety margin on a contaminated runway? The responsibility for safety is yet again to be placed on the pilot by regulators who at this time have the opportunity in new regulation to help pilots, and maintain the highest levels of safety.
The rules and regulations are ever increasing in complexity, requiring pilots to have greater and deeper knowledge of a range of specialist subjects. Where is the department for clarifying regulations, even removing them, what efforts are being made to simplifying operations and thus improve safety? Where is the book of all of the certification assumptions made about pilot’s knowledge and performance … there are many draft sections in the accident and incident reports around the world.
Re the point, “I do not agree. The terms Good, Medium, ..... applies to runway contaminated with snow, slush and ice. They have been used for decades. The aircraft operators need a 'scale' for relating operations on contaminated/slippery runways.”
In the decades of using potentially ambiguous terms, alternatives, and those open to misinterpretation, the hull-loss accident statistics show that overruns are top of the list. If the industry is to improve safety in this area, then more rigid safety barriers are required. Many of the contributory causes involve human error; in order to reduce this, the threats to the operation have to be removed or their effect minimized, e.g. by providing adequate safety margins or prohibiting tailwind landings on contaminants, and the error provoking circumstances such as interpreting third party runway reports and choosing between ‘less than ideal’ data sets should be eliminated.