The FAA is stressing the importance of operators notifying air traffic control (ATC) when they conduct ILS autoland procedures, citing several instances when localizer signal interference caused deviations on landing.
In a new Safety Alert for Operators (SAFO 21004), the FAA said it “emphasizes the importance of pilot awareness throughout the coupled approach and autoland maneuver.” The SAFO pointed to an instance in 2018 when a flight crew flew a Category III approach/landing (autoland) in non-CAT III weather without notifying ATC. According to a subsequent investigation, before it completed the CAT III landing, a departing aircraft interfered with the affected airport’s ILS localizer signal. This caused the landing aircraft to deviate to the left of the runway centerline.
“While the flight crew realized there was a substantial deviation from centerline at 50-70 feet above the surface, they initiated a go-around and a touchdown in the grass occurred,” the FAA said. This was among other such deviations.
ATC issues measures designed to protect ILS-critical areas from vehicle traffic and taxiing aircraft when the weather has a ceiling of fewer than 800 feet and/or visibility of fewer than 2 miles. However, the ATC measures do not cover preceding arriving or departing aircraft, the FAA said, adding, “Critical area protection is not required when the official weather observation reports weather conditions at or above 800 feet and/or visibility at or above 2 miles. Additionally, critical areas are not protected at uncontrolled airports or at airports with an operating control tower when weather or visibility conditions are above those requiring protective measures.”
However, the use of ILS autoland procedures is common even in good weather, the agency noted, citing a number of reasons for this, such as to maintain proficiency or recency of experience requirements, and to mitigate fatigue.
Further, these ILS disturbances can occur regardless of weather, the agency said, cautioning that this could spur momentary deviations to ILS course/glide slope signals.
The FAA encouraged operators to include in their procedures a practice of informing ATC of their intent to conduct an autoland approach. Such notification enables ATC to issue an advisory if the critical area is not protected, the FAA said. Also, operators should ensure their flight-crew manuals have effective information surrounding briefings, stabilized approaches, and go-around procedures during autoland procedures. Flight crews should remain alert to possible deviations during autoland procedures.