B747-400 flight crew reported during a CAT1 autoland approach; the aircraft pitched up 10 degrees at 20 feet AGL; resulting in a go-around.
Synopsis
B747-400 flight crew reported during a CAT1 autoland approach; the aircraft pitched up 10 degrees at 20 feet AGL; resulting in a go-around.
Narrative
The aircraft was on its last day of autoland currency; so we planned to perform an autoland at ZZZZ. When we checked on with Approach control ; we informed them of our intention to perform an autoland. We were cleared for the ILS to runway XXR. During the approach everything seemed in order and the ILS critical area clear. The weather at the time was winds 320/12G20; 10 miles VIS; and SCT015. The aircraft was performing to standard until around 20 feet; at which point it abruptly pitched up to about 10 degrees nose up; and the flight path leveled off. As it became clear the aircraft would not land in the landing zone; the PF called for a Go-around. When the PF pressed the TOGA switches; the aircraft did not respond; and so he clicked off the automation and performed the go-around manually until we were in a safe position to re-automate. From that point; all went smoothly to a hand-flown landing.Cause: I am uncertain what caused the aircraft to deviate from the autoland profile so close to the ground. Suggestions: Because I do not know the cause; I cannot provide a suggestion.
Second reporter narrative
While attempting a CAT I autoland to Runway XXR at ZZZZ for airplane currency; the aircraft pitched up aggressively towards 10 degrees around 20 feet AGL; significantly reducing the descent rate and shifting the landing point; to where landing within the touchdown zone was not assured. The airfield was advised on our first contact with ZZZZ Approach concerning our desire to perform an autoland and the critical area for the ILS appeared clear. The conditions during the approach were winds 320/12G20; with 10 miles or more on the VIS; and scattered clouds about 1500 MSL. The aircraft weighed about 282.9 and flaps 30 with autobrakes 4 selected. I added 8 knots to the vREF because the gusty winds seemed to cause the speed to bracket up to 5 knots. The vREF was 153 and the bug was set at 161. This was 3 knots over the usual +5 additive for a buffer of safety. All parameters were being met inside the aircraft for the autoland prior to this aggressive pitch. I was PF and called the go-around; I pressed the TOGA switches; but the thrust levers did not advance. At that point; since the plane started to pitch up; I disconnected the autothrottles and autopilot and advanced thrust levers manually to go-around thrust. Due to the issue of the thrust levers not advancing after the TOGA switch was pressed; I was slow in calling for the flaps to 20 and the gear up. The winds were gusting up to 20 kts. The PM notified ATC; and I reengaged the automation once we were safely climbing away and decided to stay at flaps 5 for the missed; expecting a vector for another approach. We were vectored for the ILS XXR; to a hand-flown landing which was uneventful. Cause: I don't know what caused the autopilot to aggressively pitch up that close to the ground. It could have been the wind gusts; ILS signal interruption or a radio altimeter glitch. Suggestions: The autoland was set to expire the next day. ZZZZ airport was extremely busy and the winds were gusty; not an ideal time for a CAT I autoland; but it was still doable. One suggestion I recommend is don't wait till the last day to get the autoland current. The ZZZZ ATC did an outstanding job on vectoring us around and fitting us in for another approach after the go-around.
More incidents for this aircraft family →
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.