Emery Crash Probe
Aviation Week & Space Technology
August 11, 2003
By Frances Fiorino
Airline cargo maintenance, operations and crew training will likely draw closer industry scrutiny, now that the NTSB has determined the probable cause of the February 2000 crash of Emery Worldwide Airlines Flight 17 and issued 15 related safety recommendations.
On Feb. 16, 2000, the three-person flight crew of Emery Flight 17, a DC-8-71F, N8079U, reported an "extreme CG condition" shortly after takeoff from Sacramento (Calif.) Mather Airport, near Rancho Cordova. The crew was attempting a return to the field for an emergency landing when the aircraft crashed, killing the pilot, copilot and flight engineer. The aircraft was destroyed.
The NTSB cited probable cause of the accident as "a loss of pitch control resulting from the disconnection of the right elevator control tab. The disconnection was caused by the failure to properly secure and inspect the attachment bolt."
The safety board concluded the bolt connecting the right elevator control tab crank fitting to the pushrod had migrated out of the fitting sometime after the accident aircraft's previous takeoff (from Reno, Nev.). As a result, the control tab disengaged from the pushrod and shifted to a trailing edge down position (see diagram).
As the aircraft accelerated during takeoff roll from Sacramento, the right elevator control tab crank fitting contacted the disconnected pushrod, leaving it in an extreme trailing edge-down deflection. This resulted in the DC-8's extreme nose-up pitch attitude. The board noted that the pilots were unable to overcome the effects of the restricted right elevator control tab despite application of large nose-down forces on the control columns.
The board determined the bolt was improperly secured and inspected, either during the DC-8's Nov. 1999 D inspection or in subsequent maintenance. However, the NTSB was unable to determine exactly when the improper securement occurred. The NTSB also found that each crewmember was properly certificated and qualified and had received appropriate training and off-duty time. There was no evidence of any preexisting medical or behavioral condition that might have affected the crew's performance. In addition, cargo loading was routine, and the aircraft was within prescribed CG limitations.
The board's 15 recommendations stemming from the accident include the following requirements of DC-8 operators:
-- Train flight crews to look for symmetry between right and left elevators, control tabs and geared tabs during preflight inspection.
-- Develop 80-kt. elevator check procedures to ensure pilots are aware of proper elevator functioning prior to aircraft liftoff, and to incorporate these procedures in training and normal operations.
-- Incorporate periodic elevator position indicator (EPI) calibration inspections into maintenance programs to ensure the EPI indications seen by pilots accurately represent the condition of the elevator. The board found DC-8 operators, including Emery, did not use the EPI to confirm elevator movement indications above and below neutral range during the 80-kt. elevator check.
-- Create or revise DC-8 work cards to ensure they specifically include postrigging inspection of the elevator assembly. This would include verification of the security of the elevator control tab attachments. Further, review and revise work cards related to critical flight controls to ensure tasks are identified as discrete with individual inspection sign-off requirements.
-- Require Part 121 air carrier operators to provide maintenance personnel with manufacturer's current installation drawings or illustrated parts catalog (IPC), and require the use of either by maintenance personnel in the installation or assembly of aircraft components.
The Air Line Pilots Assn. was pleased with the recommendations, but disappointed they "did not go far enough in addressing deficiencies in corporate safety culture and FAA oversight." ALPA noted that since 1984, the NTSB has investigated 38 cargo-related accidents, and that a U.K. Civil Aviation Authority study found cargo operations are four times more likely to have fatal accidents than passenger flights.
ALPA has formed a committee to define cargo safety issues more clearly, and the NTSB is working to present a cargo airline safety forum.
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Table, Illustration: Diagram: Elevator Control Tab Pushrod<credit>NTSB