Is it a Loss of Braking?The LOSS OF BRAKING procedure memory items have to be applied in the extremely remote case of a failure of the braking system. In-service experience shows that inappropriate application of the LOSS OF BRAKING procedure may contribute to a risk of runway excursion.
This article recalls the conditions to apply the LOSS OF BRAKING procedure and highlights the risk of confusion by the flight crew when monitoring the aircraft deceleration during landing on contaminated runway.Event Description
An A320 aircraft was stabilized in final approach in CONF FULL. Autobrake MED was selected. The runway length was 3700 m. Autopilot and autothrust were both engaged. External conditions were combining snow showers and left crosswinds between 16 kt and 22 kt. The runway was reported as contaminated with snow.
Normal touchdown
① The touchdown was performed nominally at 140 kt ground speed (GS). The spoilers extended, ② MAX REV was applied, and the MED autobrake mode activated. ③ The DECEL light on the MED pushbutton switch transiently turned on and ④ then went OFF shortly after. The ON light remained ON.
Application of the LOSS OF BRAKING procedure
⑤ At around 70 kt, the flight crew set the A/SKID & N/W STRG switch to OFF. The PF selected REV IDLE almost simultaneously. The aircraft was slightly diverging from the centerline toward the left edge of the runway.
Lateral runway excursion
⑥ The PF applied differential braking and rudder inputs to the right to try to recover the runway centerline. ⑦ The flight crew set the engine thrust levers to IDLE and ⑧ the PF released the brake pedals for some seconds. ⑨ They selected REV MAX again and ⑩ applied maximum pedal braking. The aircraft skidded, deviated from the centerline and ⑪ came to a stop at 90° from the centerline with the nose landing gear out of the runway.
This article recalls the conditions to apply the LOSS OF BRAKING procedure and highlights the risk of confusion by the flight crew when monitoring the aircraft deceleration during landing on contaminated runway.
Event Description
An A320 aircraft was stabilized in final approach in CONF FULL. Autobrake MED was selected. The runway length was 3700 m. Autopilot and autothrust were both engaged. External conditions were combining snow showers and left crosswinds between 16 kt and 22 kt. The runway was reported as contaminated with snow.
Normal touchdown
① The touchdown was performed nominally at 140 kt ground speed (GS). The spoilers extended, ② MAX REV was applied, and the MED autobrake mode activated. ③ The DECEL light on the MED pushbutton switch transiently turned on and ④ then went OFF shortly after. The ON light remained ON.
Application of the LOSS OF BRAKING procedure
⑤ At around 70 kt, the flight crew set the A/SKID & N/W STRG switch to OFF. The PF selected REV IDLE almost simultaneously. The aircraft was slightly diverging from the centerline toward the left edge of the runway.
Lateral runway excursion
⑥ The PF applied differential braking and rudder inputs to the right to try to recover the runway centerline. ⑦ The flight crew set the engine thrust levers to IDLE and ⑧ the PF released the brake pedals for some seconds. ⑨ They selected REV MAX again and ⑩ applied maximum pedal braking. The aircraft skidded, deviated from the centerline and ⑪ came to a stop at 90° from the centerline with the nose landing gear out of the runway.
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