\ 1Jf-.J .A ~~J -111_ lC.i.,J(ij' iv\.li 13ahrami . _ Manug.er, Tran~port 1\nplHne D tre~IOr.ltC Aircraft Ccniika1ion Service 03/12/12 AC 25.803-1A
= Total evacuation time for the exit (in seconds) TTotal Exit i n = Total number of exits used The available time margin calculated using the above formula should be 9 or more seconds. The time interval of 9 seconds (10 percent of the current standard of 90 seconds) is based on the demonstrated capability of today's transport category airplanes. Note that this method of establishing conservatism depends on the passenger management techniques being appropriate to balance the evacuees among the exits.
(b) An alternative to the margin calculations shown above, as a means of showing conservatism in the analysis, would be to use exit flow rates less than the calculated average and exit preparation times greater than the calculated average. The amount of performance degradation can be a calculated number such as the value of a standard deviation. The average evacuee flow rate would be reduced (thereby increasing the time of exit flow) and the average exit preparation time would be increased by the respective calculated values. If, however, the data used to derive the standard deviations is widely scattered resulting in a large value for the standard deviation, the applicant may choose to use the slowest rate or longest exit preparation time instead.
v. Initial Coordination of Analysis. As a general guideline, evacuation analyses should be informally coordinated as early as possible with the FAA certification office prior to formal submittal to ensure that all significant factors have been addressed.
10. Computer Modeling. Work is being done in the field of computer modeling to develop programs which could be used to demonstrate compliance with the evacuation demonstration requirements. Although progress has been made, to date, no program has been presented to the FAA and found acceptable as a substitute for an actual demonstration. Any applications for the use of computer modeling to demonstrate compliance with § 25.803(c) should be coordinated with the Standards Staff of the Transport Airplane Directorate.
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