Synopsis
Immediately after touchdown, the aircraft pitched nose-up, causing the tailskid to contact the runway and sustain light abrasion damage. Recorded flight data indicated that the pitch-up was probably caused by an up-elevator control input by the handling pilot when the aircraft skipped on landing. It may also have been aggravated by the simultaneous manual deployment of speed brakes by the non-handling pilot. The aircraft touched down at less than the recommended speed, leading to an increased pitch attitude and reduced tail clearance margin. Additionally, a significant mass of baggage had been loaded in the rearmost hold, which the crew did not account for in their weight and balance calculations. Although centre of gravity limits were not exceeded, this made the aircraft more sensitive in pitch.
History of the Flight
The aircraft, operated under charter to the UK Ministry of Defence, was landing at RAF Brize Norton. The crew had traveled by road from Gatwick Airport the previous day. They were scheduled to operate a return flight to Zagreb, Croatia, and then fly empty to Gatwick.
Among the Acceptable Deferred Defects in the aircraft technical log was an inoperative automatic speed brake system, requiring manual deployment. The control lever was placarded “INOP.” The outbound flight to Zagreb proceeded without further issues.
At Zagreb, a longer turnaround occurred due to baggage handling problems. A Loading Instruction Report (LIR) was compiled and passed to the flight crew. The co-pilot used the LIR to prepare a load sheet, countersigned by the commander. The aircraft departed Zagreb at 1640 hrs with 136 passengers and the co-pilot as handling pilot.
During the takeoff roll, the co-pilot noted an uncommanded pitch-up at VR, but no excessive inputs were needed. The commander did not recall this being mentioned later. During the approach to Runway 26 at Brize Norton, the autopilot and autothrottle were disconnected at about 1,000 ft. The commander alerted the co-pilot to low airspeed; the co-pilot added power. The aircraft deviated above the glide slope, and the co-pilot corrected, resulting in an increased descent rate that was arrested by about 20 ft above the runway. A normal main gear touchdown followed.
The co-pilot selected reverse thrust, and the commander manually deployed speed brakes. As the co-pilot relaxed back pressure to lower the nose, the aircraft pitched up unexpectedly. Both pilots pushed forward on the control columns, requiring significant forward movement to stop the pitch-up. Subsequent nose gear touchdown and landing roll were normal.
After parking, normal unloading began before crew intervention, preventing accurate mass distribution assessment. Inspection revealed a tail strike with light damage to the tailskid friction pad. It was later established that the automatic speed brake system had been rectified two days earlier but the placard and ADD page were not updated.
Loading and Performance Information
The loading operation at Zagreb was handled by local agents. Baggage was loaded into containers; due to volume, 2,339 kg of loose bags were placed in the rear bulk hold (hold five). The LIR accurately reflected this distribution. However, when the co-pilot compiled the load sheet, he did not notice the bags in the bulk hold, so they were not included. The commander also missed the error when countersigning. The load sheet showed a takeoff mass of 129,868 kg and a CG at 26% MAC. The actual takeoff mass was 132,207 kg with CG at 30.5% MAC (aft limit 33.3% MAC). The stabilizer trim setting for actual conditions would have been approximately 1.3 units, and takeoff speeds increased by 1-2 kt.
The landing data card showed a landing mass of 119,500 kg with a flaps 30 Vref of 131 kt from the FMC. Actual landing mass was about 121,839 kg, giving a Vref of 132 kt.
Recorded Information
Boeing’s Air Safety Investigation Department analyzed FDR data. Several parameters were invalid during takeoff and initial climb, including elevator and stabilizer positions, and engine data. The stabilizer remained invalid throughout the flight. The nature of anomalies suggested a maintenance issue, which the operator was made aware of. Air data confirmed calm conditions during landing. The data showed incremental nose-up column input of 2.5°-3° at 135 kt initiating rotation, compared to Boeing flight test data requiring 5°-6° for similar conditions with recommended stabilizer. The column-elevator relationship was validated against simulator data.
During landing, the approach was stabilized through 700 ft radio altitude. After touchdown and speed brake deployment, the column moved further nose-up by about 6° in 1.5 seconds, then the crew applied 26° nose-down input. The pitch attitude at first touchdown appeared close to that for Vref, but the exact value was not recorded.
Handling Information
The Boeing Flight Crew Training Manual recommends touchdown at no less than Vref speed, producing a pitch attitude of about 5.5°. Touchdown at Vref-5 increases attitude, reducing tailskid clearance. Tailskid contact occurs at a pitch attitude of 7.9° with oleos compressed and 9.6° extended. According to the FCTM, touchdown in this instance would theoretically have occurred at a pitch attitude of 6.9°.