|Title:||Elevator failure, Douglas DC-8-71, March 11, 1997|
|Micro summary:||Flight control failure on this Douglas DC-8-71 resulted in a rejected takeoff.|
|Event Time:||1997-03-11 at 1910 PST|
|Publishing Agency:||National Transportation Safety Board (NTSB)|
|Site of event:||Portland, OR|
|Departure:||Portland International Airport, Portland, Oregon, USA|
|Destination:||Toledo Express Airport, Toledo, Ohio|
|Airplane Type(s):||Douglas DC-8-71F|
|Operator(s):||Air Transport International|
|Type of flight:||Revenue|
NTSB short summary:
improper installation of four attach bolts on the elevator drive torque tube.
During the process of changing one side of the elevator, maintenance personnel put washers under the head of the bolts used to attach the inboard portion of the elevator drive torque tube to the outboard portion of the tube. Because washers were not called for in the installation, the clearance between the bolt heads and the elevator structure was reduced to a point where, under the flight loads generated during the takeoff roll elevator test, elevator binding occurred. Because of this binding, the takeoff was aborted. It was later determined that washers had been put under the bolt heads during a previous installation, and the mechanics had simply copied what they saw while removing the old elevator. After the incident, maintenance personnel checked the Illustrated Parts Catalog (IPC), which clearly showed that no washers were to be used. They also checked the installation of the elevator on the other side of the aircraft and discovered that it had been installed correctly (no washers under the bolt heads).
NTSB factual narrative text:
On March 11, 1997, approximately 1910 Pacific standard time, the pilot of a DC-8-71, N830BX, aborted a takeoff at Portland International Airport because the elevator was not correctly responding to his inputs. The airline transport rated captain, his first officer, and the flight engineer were not injured, and the aircraft was not damaged. The 14 CFR Part 121 cargo flight, which was being operated by Air Transport International, was in the process of departing for Toledo Express Airport, Toledo, Ohio. The flight, which was on an IFR flight plan, was departing in visual meteorological conditions.
According to the pilot, when he pushed the yoke forward for the 80 knot elevator check required by the company, the aircraft pitch angle did not change, and the yoke felt as if it was binding. He then applied a small amount of back-pressure on the yoke, expecting that the nose of the aircraft would rise slightly. Since the pitch attitude did not appear to change, and because the yoke still felt as if it were binding, the pilot elected to abort the takeoff. The aircraft was then taxied to a maintenance hangar in order for the elevator system to be inspected.
Further investigation reveled that just prior to this flight, maintenance personnel had replaced the right elevator because a hole had been detected in its top skin. During the replacement process, washers were put under the head of four bolts that attach the inboard portion of the elevator drive torque tube to the outboard portion of the tube, an application where no washers are called for. According to the operator, "With the washers installed under the bolt heads, clearance between the bolt heads and the elevator structure was reduced to a point where under a flight load, an interference condition existed."
According to the individuals who replaced the elevator, they used the washers for the new installation because when the bolts were removed from the old elevator torque tube attach fitting there were washers under the heads. They said that they assumed that the old installation had been correct, and simply copied what had been done in the past. After the incident, they checked the Illustrated Parts Catalog (IPC), and discovered that no washers were called for in this installation. In addition, maintenance personnel checked the installation of the bolts on the left elevator and found that those bolts had been installed correctly (no washers under the bolt heads).
|Learning Keywords:||Operations - Maintenance|
|Operations - Rejected Takeoff before V1|
|Operations - Upset - Uncommanded or excessive Pitch|
|Systems - Elevator, Stabilizer, Rudder, Ailerons|
|Systems - Flight Control System|
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