What happened
On July 20, 1998, an Evergreen International Airlines Boeing 747-212B, registration N482EV, departed Amsterdam Airport Schiphol for New York JFK. During the initial climb, the flight crew inadvertently retracted the flaps from position 20 directly to position 1, skipping the required intermediate position 5. This error occurred while the aircraft was traveling at a speed below the minimum maneuvering requirements for the new configuration.
As the aircraft entered a right turn to follow the standard instrument departure, the loss of lift caused airframe vibrations and the activation of the stick shaker, signaling an approaching stall. While the captain successfully prevented a full stall by leveling the wings and increasing power, the aircraft experienced pitch oscillations for approximately one minute due to continued active control inputs.
Believing the aircraft was experiencing weight and balance issues, the crew declared an emergency and decided to return to Sch/Schiphol immediately. This decision led to an approach characterized by excessive speeds and a landing weight that exceeded the maximum allowable limit by 124,500 pounds. Due to the high speed, heavy weight, and the inoperability of one thrust reverser, the wheel brakes reached extreme temperatures, causing the fuse plugs to melt and 10 of the 16 tires to deflate.
The investigation
The Dutch Safety Board examined flight data recorder (DFDR) plots, cockpit voice recorder (CVR) transcripts, and air traffic control communications. The investigation focused on the sequence of flap retraction, the crew's reaction to the stall warning, and the decision-making process regarding the return to Schiphol. Investigators also reviewed the airline's Crew Resource Management (CRM) training and maintenance records.
Findings
- The primary cause was the inadvertent retraction of flaps from 20 to 1, which placed the aircraft in a configuration where the airspeed was below the safe maneuvering limit.
- The crew lacked sufficient familiarity with the aircraft's specific aerodynamic response during stall recovery, leading to induced pitch oscillations.
- A lack of situational awareness and poor CRM led the crew to incorrectly diagnose a weight and balance problem.
- The decision to return to Schiphol under high-speed, high-weight conditions resulted in excessive brake heat and the subsequent deflation of ten tires.
Safety action
The investigation resulted in recommendations for the Federal Aviation Administration (FAA) to ensure Evergreen International Airlines reviewed its flap coordination procedures, enhanced its stall recovery training, and improved its CRM and situational awareness programs.