Investigation Summary
The accident occurred during a period of winter weather where the ramp and taxiways were covered in packed snow and ice. During the initial taxi, the captain noted the extremely slippery conditions, describing the surface as an ice rink. The crew performed engine run-ups to clear ice from the engines before lining up on runway 4L. As the takeoff roll commenced and the aircraft reached approximately 80 knots, it began to veer left. The captain attempted to correct the deviation using the rudder and the nosewheel steering tiller. However, the use of the tiller at high speeds on a slippery surface was inappropriate and exacerbated the loss of control. The NTSB investigation highlighted that Tower Air's procedures for slippery runways were inadequate and that the airline's flight simulators did not accurately reflect the ground handling characteristics of a Boeing 747 on ice. Furthermore, the Flight Data Recorder (FDR) was found to be malfunctioning, forcing investigators to rely heavily on the Cockpit Voice Recorder (CVR) and sound spectrum analysis to reconstruct the engine performance and timing of the crew's actions.
Final Conclusions
The NTSB determined the probable cause was the captain's failure to reject the takeoff in a timely manner when excessive nosewheel steering tiller inputs resulted in a loss of directional control on a slippery runway. Contributing to the accident were inadequate slippery runway operating procedures developed by Tower Air and Boeing, as well as the lack of fidelity in flight training simulators for such conditions. The captain's reapplication of forward thrust after the initial loss of control was cited as a factor that increased the severity of the excursion and resulting damage. The NTSB report NTSB/AAR-96/04 was adopted on December 2, 1996.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
53 years old, former U.S. Navy pilot.
First Officer
56 years old.
Flight Engineer
34 years old.
Systems & Failure Modes
Nosewheel Steering Tiller
A control wheel used for low-speed ground maneuvering. Its use at high speeds during takeoff can cause abrupt and uncontrollable directional changes, especially on slippery runways.
Flight Data Recorder (FDR)
The unit on N605FF had several malfunctioning components that went unnoticed by maintenance, resulting in random, unusable data values.
Public Address (PA) System
The PA and interphone wiring was damaged during the nose gear collapse, preventing the crew from communicating evacuation orders to the entire cabin.
Interesting Facts
- 01The aircraft was a 24-year-old Boeing 747-136 with over 90,000 airframe hours.
- 02The Flight Data Recorder (FDR) was found to be malfunctioning and provided no usable data for the investigation.
- 03One flight attendant suffered a broken shoulder when service carts became dislodged in the aft galley.
- 04The captain used the nosewheel steering tiller during the takeoff roll, which is contrary to standard high-speed directional control practices.
- 05Post-accident simulator tests revealed that Tower Air's simulators were inaccurate regarding ground handling on slippery surfaces.
Safety Actions & Advisories
Simulator Fidelity Improvements
The NTSB recommended that the FAA require flight simulators to more accurately model aircraft ground handling characteristics on slippery runways.
Galley Equipment Security
Recommendations were made to improve the security of service carts and galley equipment to prevent them from becoming projectiles during sudden decelerations.
FDR Maintenance Oversight
The investigation led to calls for stricter maintenance and testing of Flight Data Recorders to ensure they are functional before flight.
Location
ACCIDENT SITE · Coordinates taken from the entered by an editor.