to departure, since they were not required to demonstrate positively such knowledge. Accordingly, the Board believes that the procedures should be revised to require that pilots demonstrate by some means (e.g., an oral or written test or examination other than signing the flight release) that they are familiar with the "off route" airport into which they will operate.[1]
The flightpath and profile (Attachment 1) show that the aircraft descended through the MDA approximately 2 miles from the end of the runway and that such descent was not corrected in time to avoid impact with the trees. The major thrust of the investigation was focused on uncovering the reason or reasons which might explain this descent.
The relatively stable descent depicted by the flight recorder altitude trace does not suggest that a loss of control or autopilot "runaway" was experienced during the approach. However, conversation between the pilots at approximately 1931 and 1934 expressed concern with the performance of the autopilot. The captain's comment at 1931, ("that thing captured! How did it capture?") expressed surprise that the autopilot had apparently captured a glide slop signal when there was no signal. The glide slope capture probably resulted because the captain turned the autopilot NAV SELECT switch to ILS rather than to either MAN G/P or NAV LOC, which should be used on a localizer approach. Since the autopilot controls the aircraft on the glide slope by maintaining a null signal, the total absence of a glide slope signal, as in this case, would have resulted in an automatic 700 to 800 feet/minute descent. Subsequent increases in the rate of descent indicate that the NAV SELECT switch was turned to a proper position. The later comment at approximately 1934, ("This autopilot ain't responding just right - - - - sluggish") indicates dissatisfaction with the performance of that component, but the captain did not specify in which axis, or in what manner, it was "sluggish." An analysis of heading and altitude traces of the flight recorder indicates that the autopilot was used to maintain a course inbound on the localizer and to descend the aircraft during at least two periods of the instrument approach. Notwithstanding the captain's comments, both of which were made when the flight was in the vicinity of the outer marker, there is no indication of any hazardous situation. Although the captain's attention to the operation of the autopilot to the extent reflected by these remarks could have detracted from his normal instrument scan, there is no evidence to suggest that the autopilot was misused or that it had any direct bearing on the accident.
- ↑ A recommendation to the above effect is set forth hereafter, in the Recommendations section.
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