Incident Details
On 26 December 1999, a McDonnell Douglas DC-9-83 was preparing for a charter flight from Munich Airport to Las Palmas. During the takeoff roll on runway 26L, the flight crew could not rotate the aircraft at the calculated rotation speed (VR). The control column could only be moved slightly past the neutral position. The takeoff was aborted, and the aircraft decelerated on the remaining runway without further incident. There were no injuries, and the aircraft sustained light damage.
Aircraft and System Description
The elevator control system of the MD-83 (the designator used in the report) comprises a horizontal stabilizer, elevators on each side, a control tab, and a geared tab. The left and right elevators are actuated separately via mechanical linkages and a hydraulic system. The control column connects both sides. The control tab is positioned mechanically by the control column, and aerodynamic forces then deflect the elevator. The elevators can move independently of the control column on the ground. Geared tabs assist the control tabs. Hydraulic actuators can push both elevators to the full-down position if certain conditions are met; otherwise, they act as dampers.
Pre-flight Events
The aircraft had been diverted to Munich for internal reasons and landed at 14:15, parking at gate 118. A new crew took over. Due to storm-force winds, ground handling was suspended from 14:20 to 16:20. During this period, the aircraft was exposed to gusty tailwinds of up to 70 knots for about one hour. The pilot in command (PIC) observed the control surfaces being blown hard against their mechanical stops and ordered a full flight control check.
Between 14:20 and 17:00, the crew performed a functional check of all flight controls from the cockpit while observing the surfaces externally. During this check, the ELV-PWR-ON light, indicating hydraulic pressure for elevator operation, did not illuminate. The PIC also noted unusually stiff manual elevator control. The check was completed at 17:00. At 18:10, the aircraft left the gate; wind speeds had dropped below 40 knots. During the taxi checklist at 18:15, the elevator hydraulic system was rechecked: the control column had to be held forward for 15 seconds before the light came on.
Post-flight Examination and Findings
After the abort, maintenance personnel found the left elevator jammed in the full-down position. The inner linkage of the geared tab was bent at its attachment to the elevator, locking it. The eyebolt connecting this linkage to the horizontal stabilizer structure was also bent. The jamming resulted from the left elevator exceeding its normal full-down travel by more than 6°, which required overriding the spring-loaded stop. Reconstruction showed that applying a pull force on the geared tab could reproduce the jamming, and it was repeatable. The force needed to override the stop could not be applied by a single load on the elevator without risk of damage.
The investigation determined that the excessive deflection was caused by the strong tailwinds or gusts that occurred while the aircraft was parked. According to the manufacturer's documentation, flight control damage is expected at wind speeds above 52 knots (FAR 25.415), and a visual and functional check is required only if the aircraft was parked with winds exceeding 65 knots not into the wind (AMM Chapter 10). The tailwinds of up to 70 knots met this threshold. The PIC accepted the parking position, apparently unaware of the need for a special check after such tailwind exposure.
Assessment
The investigation concluded that the jammed elevator control was not detected during the special check at the gate and/or during the taxi checklist procedures. The pre-flight checks were inconsistent: the aircraft remained exposed to gusty tailwinds of up to 50 knots during the gate inspection, a visual check of the tail was omitted due to high winds, and over an hour elapsed between the functional check and departure. The dangerous condition persisted unnoticed. Deficiencies in the aircraft type's operating instructions, which lacked specific guidance for post-storm inspections, contributed to the incomplete checks.
Probable Cause
The serious incident resulted from the jammed elevator control not being detected during the special inspection at the gate and/or during the taxi checklist measures.