Originally Posted by
CaptainMongo
A319/320 fleet. We had a few of these reports at our outfit. (I don’t have access to the complete reports, only the anomaly described.)
Below the glide slope, in ALT, after arming APPR the aircraft leaves the altitude and climbs up to capture the glide slope.
Has anyone experienced this?
From the FCOM SOP
ICAO defines the envelope where the quality of the G/S signal ensures a normal capture. This envelope is within 10 NM, ±8° of the centerline of the ILS glide path and up to 1.75 θ and down to 0.3 θ (θ = nominal glide path angle).
When arming the approach well outside of the normal G/S capture envelope, a spurious G/S* engagement may occur due to a wrong G/S deviation signal.
Whenever the pilot notices the pitch movement, or the spurious G/S*, or the trajectory deviation, the pilot will immediately disconnect the AP, if engaged, to re-establish a normal attitude and will disengage APPR mode.