Narrative:

While flying a coupled ILS Z runway 8 approach into bur; the aircraft began a shallow left roll until going full-scale deflection; then began a right roll; quickly going nearly full-scale deflection to the right of course. At this point; the captain; as the PF; disconnected the autopilot and completed an uneventful landing.during the flight; I mentioned that recently (one month prior) I filed a report after flying this same approach to minimums in IMC. On that date; our coupled ILS could not maintain course past 1200 ft. On that report; I indicated the approach briefing included reference to the approach note #4; stating; 'autopilot coupled approach not authorized below 1027 ft.' the briefing continued with the stated plan to disconnect the autopilot at 1200 ft. During the actual approach; the aircraft was already rolling right; past half-scale deflection; in IMC. The response I received was confusing: it stated that they discovered that the approach note was a misprint. Apparently the note was intended to read that coupled approaches are not authorized below 1007 ft (the charted da). While that might indeed be the case; it doesn't address the safety concern that the coupled approach could not remain stable at a higher altitude. In the case of that flight; the coupled approach was unstable at 1200 ft. Now; on this recent flight (in VMC); the aircraft went full-scale deflection; both left and right; starting at 1400 ft. Bottom line: should the approach note read 'coupled ILS approaches not authorized below 1xxx ft'? This situation could be dangerous with a crew flying in IMC with fixed threats to include a congested area; steeply rising terrain; and a short runway.'

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Original NASA ASRS Text

Title: B737NG First Officer reported full scale localizer signal deflections flying the BUR ILS Z Runway 8 beginning at 1;400 feet. The ILS chart states; 'Autopilot coupled approaches not authorized below 1027 feet.' However; left and right aircraft maneuvers began much higher.

Narrative: While flying a coupled ILS Z Runway 8 approach into BUR; the aircraft began a shallow left roll until going full-scale deflection; then began a right roll; quickly going nearly full-scale deflection to the right of course. At this point; the Captain; as the PF; disconnected the autopilot and completed an uneventful landing.During the flight; I mentioned that recently (one month prior) I filed a report after flying this same approach to minimums in IMC. On that date; our coupled ILS could not maintain course past 1200 ft. On that report; I indicated the approach briefing included reference to the approach note #4; stating; 'Autopilot coupled approach not authorized below 1027 ft.' The briefing continued with the stated plan to disconnect the autopilot at 1200 ft. During the actual approach; the aircraft was already rolling right; past half-scale deflection; in IMC. The response I received was confusing: it stated that they discovered that the approach note was a misprint. Apparently the note was intended to read that coupled approaches are not authorized below 1007 ft (the charted DA). While that might indeed be the case; it doesn't address the safety concern that the coupled approach could not remain stable at a higher altitude. In the case of that flight; the coupled approach was unstable at 1200 ft. Now; on this recent flight (in VMC); the aircraft went full-scale deflection; both left and right; starting at 1400 ft. Bottom line: Should the approach note read 'coupled ILS approaches not authorized below 1xxx ft'? This situation could be dangerous with a crew flying in IMC with fixed threats to include a congested area; steeply rising terrain; and a short runway.'

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.