Just for info
John.
In attachment H, the conclusion is drawn that the informal risk assessment process used by the company in evaluating the flaps 25 and idle reverse proposals contained several weaknesses. These included:
• There is no evidence that Qantas had sought Boeing’s opinion regarding the safety impact of the new procedures and their potential effect on carbon brake wear. Management personnel agreed that Boeing’s opinion on such issues would be useful, and that they would normally consider the manufacturer’s opinion before changing procedures. Boeing has since stated that it does not support the use of idle reverse thrust as a normal procedure as it increases landing distance. It has also stated that modified braking techniques alone would produce almost as much reduction in brake wear as the combined effect of the flaps 25/idle reverse procedures.
• Qantas examined the flaps 25/idle reverse procedures of two other operators as part of the project development process. This examination was incomplete and did not identify that the procedures used by these operators were more conservative than the proposed Qantas procedures, and had additional safeguards in place for operating on water-affected runways (see airlines D and E in attachment I).
• The performance differences between idle and full reverse thrust, and between flaps 25 and flaps 30, were not fully examined. Such an examination would probably have highlighted the significant differences in landing distance on wet or contaminated runways using these various configurations.
• There is no evidence that a systematic attempt was made to identify all the situations for which flaps 30 and/or full reverse thrust would be more appropriate.
• The term ‘contaminated’ was used in the flaps 25 procedure but was not defined.
• There appears to have been no review of the human factors implications of the new procedures. For example, there appears to have been no consideration of the extent to which the use of flaps 25/idle reverse could become a skill-based habit (i.e. ‘ the norm’), and therefore might be used by crews when a more conservative configuration was required.