Aero Contractors B735 at Lagos on Apr 9th 2016, temporary runway excursion on landing
Last Update: November 27, 2020 / 00:59:49 GMT/Zulu time
On Nov 26th 2020 Nigeria's AIB (NAIB) released their final report concluding the probable cause of the serious incident was:
Excessive rudder application by the crew after touchdown.
- Reduced visibility due heavy rain on the runway.
- The decision to continue approach in an unfavourable weather condition with crosswind component of 090o/15kt.
The NAIB reported the crew had already performed an approach to runway 18L but due to rain and gusting winds (crossind components 38-45 knots) went around and requested an ILS approach to runway 18R. The Captain (54, ATPL, 16,740 hours total, 2,140 hours on type) was pilot monitoring, the first officer (39, ATPL, 2,018 hours total, 1,060 hours on type) pilot flying.
The NAIB summarized the sequence of events:
Information obtained from the ATC transcript indicated that the crew re-established contact with the tower at 18:13:21 h as follows: “Tower, NIG316 with you we are established 18R 10 miles”. Tower replied, “NIG316 continue approach 18R preceding traffic MD83 1.5 miles touchdown”. At 18:15:56 h, Tower contacted aircraft: “NIG316 continue approach” and the crew replied, “To continue approach”.
At 18:16:24 h, Tower cleared the aircraft: “NIG316 RWY 18L wind reported now 100o/15 kt check greens cleared to land” and at 18:16:34 h, aircraft replied: “Roger cleared to land RWY 18R NIG316.” At 18:16:39 h, Tower acknowledged and corrected the error in the assigned runway to runway 18R. At 18:18:46 h, Tower confirmed aircraft landed: “NIG316 landing time 18 report runway vacated”, at 18:18:49 h crew responded in the affirmative.
The autopilot was disengaged at radio altimeter height of about 83 ft when the aircraft was on ILS approach.
The aircraft touched down right of the runway centreline and veered further right, travelling about 540 m from the touchdown point into the grass verge. The Captain took control of the aircraft and brought it back to the runway. The aircraft was taxied to Aero Ramp.
The last communication between the aircraft and the tower was at 18:25:02 h when it acknowledged permission to cross link Alpha 4 (A4). The crew did not report the incident to ATC.
All passengers disembarked with no injury.
After engine shutdown, the crew disembarked, conducted a walk-around inspection and discovered deep cuts, dents and abrasions to the No. 1, No. 2 and No. 4 Main Landing Gear (MLG) tyres as well as No.1 Nose Gear (NG) tyre. There were also grass ingestions into the right MLG wheel well, right MLG wheel axle and right inboard flap tracks. Instrument Meteorological Conditions (IMC) prevailed at the time of the incident.
The incident occurred after sunset.
The NAIB analysed:
The Boeing 737 has a maximum crosswind capability of 35 knots if the runway is perfectly dry, or 15 knots if the runway is wet (Boeing manual). On the day of the occurrence, the reported wind was 090o/15kt and the runway surface was wet.
The incident was neither reported to the ATC nor entered in the Technical Log Book as required by relevant regulations.
The Cockpit Voice Recorder (CVR) did not reveal any information as it was retrieved on the 11th April 2016, two days after the occurrence as such, it was confirmed overwritten.
The Flight Data Recorder (FDR) raw data was transmitted to the Bureau by the operator. During the analysis of same at the AIB Flight Safety Laboratory, it was found to have captured substantial data covering four flight sectors. The previous three (3) flight sectors were normal. The fourth sector which was the incident flight revealed the attitude of the aircraft during the approach and landing phase.
From the FDR analysis, the aircraft was on localizer and afterwards carried out a missed approach due to crosswind of 38 kt and magnetic heading of 174o. Before touchdown on second approach to runway 18R, the aircraft was crabbing to the left with a magnetic heading of 176.5o. The autopilot was disengaged at radio altimeter height of about 83 ft when the aircraft was on ILS approach.
At about 18:18 h, the aircraft touched down right of the runway centreline and veered further right travelling about 540 m from the touchdown point into the grass verge.
The FDR plots indicate that the autopilot disengagement and touchdown occurred within seconds at 18:18 h (making the approach resemble an “auto land / approach” gone wrong).
The FDR plots also showed that the PF applied the rudder pedals prior to touchdown - the PF began a right rudder command input, likely to initiate a de-crab manoeuvre. Shortly after touchdown the PF’s right rudder command reached 11.2 degrees to the right of the datum with an associated deflection of 25.8 degrees of the aircraft rudder tail plane to the right which corresponds to the aircraft veering to the right of the runway centreline and excursed into the grass verge.
This article is published under license from Avherald.com. © of text by Avherald.com.
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