Unexpected Autopilot Behaviour on Instrument Landing System (ILS) Approach
- Published
- Replaces
- 2014-07
AI-generated summary of the official EASA document. Verify against the PDF before acting.
What to do
Operators should develop explicit procedures defining operational limits for intercepting the glide slope from above and train flight crews on the false glide slope inversion phenomenon and related threats. They must report similar occurrences to their National Aviation Authority and relevant investigation bodies. ANSPs are recommended to use navigation procedures that facilitate intercepting the glide slope from below to reduce flight crew workload.
Summary
EASA Safety Information Bulletin 2014-07R1 addresses unexpected autopilot behavior during Instrument Landing System (ILS) approaches, specifically when intercepting the glide slope (G/S) signal from above. The bulletin highlights incidents involving Boeing 737-800 and Airbus A340 aircraft where false glide slope signals caused sudden pitch-up maneuvers, risking stall conditions. It raises awareness among operators, Air Navigation Service Providers (ANSPs), and training organizations about this safety concern.
What changed
This revision replaces the original EASA SIB 2014-07 issued in March 2014 by including new specific safety recommendations aimed at increasing the effectiveness of the guidance. It incorporates findings from investigations by the Dutch Safety Board, BEA, and ANSV, emphasizing the risks of false glide slope capture and autopilot-induced pitch-up events.
Why it matters
The bulletin is critical for aviation professionals because it identifies a latent hazard in autopilot systems during ILS approaches that can lead to sudden pitch-up and potential stall without crew warning. Operators and training organizations must understand this phenomenon to prevent loss of control incidents and ensure safe approach procedures. Awareness and training can mitigate risks associated with autopilot engagement above the nominal 3-degree glide path.
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