Airbus A320 ILS Signal Disturbance and Alpha Floor Activation at Hamburg (F-GJVA)

Incident Overview and Context On March 28, 2012, at approximately 18:20 UTC, an Air France Airbus A320, registration F-GJVA, was operating a public transport flight from Paris Charles de Gaulle to Hamburg, Germany. The crew consisted of a pilot flying (PF) and a pilot not flying (PNF). The incident occurred during an ILS Category I approach to runway 23. The airport configuration had recently changed due to wind, with landings on runway 23 and departures on runway 33. The F-GJVA was the second aircraft to land on runway 23 following this change. ## Approach and Signal Disturbance The crew was radar vectored and cleared for the ILS approach. The PF manually disengaged the autopilot and auto-thrust 40 seconds before localizer capture, with flight directors displayed. The PNF reported a 50 kt crosswind, leading the PF to decide on a flaps 3 configuration instead of full flaps. As the aircraft approached the runway threshold, a Boeing 737 on the ground was instructed to cross runway 23 but was stopped on taxiway D by the tower controller. This stop point was located within the critical glide slope protection zone for runway 23. The tower controller did not have the F-GJVA on frequency and did not inform the approach controller of the situation. ## Aircraft Response and Go-Around Upon the Boeing 737 entering the critical zone, the glide slope information on the F-GJVA's primary flight display became disturbed. The crew initially misinterpreted the deviation, believing the aircraft was below the glide path when it was actually above. The PF made pitch-down inputs and reduced thrust, causing the vertical speed to reach -2,900 ft/min. The aircraft then stabilized at approximately 1,600 ft QNH, and the crew extended the landing gear and selected flaps 3. The glide slope deviation reached its upper limit, prompting the PF to apply pitch-up inputs. The engines were at idle, and the aircraft began to climb at 151 kt. The PNF suggested aborting the approach, which the PF accepted. ## Alpha Floor Activation During the go-around, the 'SPEED, SPEED, SPEED' alarm triggered at 143 kt. The crew advanced the thrust levers toward maximum continuous thrust (MCT). The high-incidence protection and Alpha Floor activated, automatically engaging auto-thrust and setting thrust to TOGA. The pitch attitude increased from 15° to 22° at a speed of 121 kt. The PF then applied pitch-down inputs, and the crew selected flaps 2 and retracted the landing gear. The aircraft reached the go-around altitude of 4,000 ft, and the crew disengaged auto-thrust. They subsequently completed a new approach to runway 33 without further incident. The crew reported ILS problems to the approach controller, who stated there were no other reports of incidents.