Investigation Summary
The accident occurred during a rapidly developing thunderstorm. While on final approach to Runway 18R, the crew encountered heavy rain and significant wind fluctuations. Realizing the danger, the captain ordered a go-around. However, as the flaps were retracted from 40 to 15 degrees, a software discrepancy in the Honeywell windshear warning system inhibited the red windshear alert. The First Officer, experiencing a somatogravic illusion—a type of spatial disorientation where rapid acceleration is perceived as a steep pitch-up—responded by reducing the pitch from 15 degrees nose-up to 5 degrees nose-down. This pitch reduction, combined with a massive 61-knot wind shift, caused the DC-9 to plummet. The NTSB also highlighted that Air Traffic Control failed to relay timely weather information, including a special weather observation and low-level windshear alerts that were being broadcast on other frequencies.
Final Conclusions
The NTSB determined the probable cause was the flight crew's decision to continue the approach into severe convective activity and their subsequent failure to recognize and properly escape the windshear. Contributing factors included the lack of real-time weather dissemination by ATC, inadequate software logic in the windshear warning system, and USAir's failure to ensure adherence to standard operating procedures regarding thunderstorm avoidance.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Michael R. Greenlee, age 38
First Officer
James P. 'Phil' Hayes, age 41
Systems & Failure Modes
Honeywell Windshear Warning System
Onboard system designed to detect windshear; failed to trigger because software logic inhibited alerts while flaps were moving from 40 to 15 degrees.
ASR-9 Radar
Airport surveillance radar; the NTSB noted ATC lacked procedures to properly issue ASR-9 weather information to the pilots.
Pratt & Whitney JT8D-7B
The two rear-mounted engines; during the go-around, thrust was set below the standard EPR limit of 1.93.
Interesting Facts
- 01The aircraft was 21 years old, had logged 53,917 airframe hours, and its Manufacturer Serial Number (MSN) was 47590 (Line Number 703).
- 02The windshear warning system failed to alert the crew because the flaps were in transit, which lowered the system's sensitivity.
- 03The aircraft broke into four major sections; the cockpit and unoccupied first-class cabin came to rest on Wallace Neel Road.
- 04A South Carolina jury later found the flight crew negligent for choosing to land in a known thunderstorm.
- 05The tail section and rear engines came to rest in the carport of a residential house.
Safety Actions & Advisories
Windshear Warning Software Update
Honeywell and the FAA addressed the software logic that inhibited windshear alerts during flap transitions to ensure warnings are provided even during configuration changes.
ATC Weather Reporting Procedures
Procedures were updated to ensure controllers provide real-time ASR-9 radar weather data and low-level windshear alerts to all aircraft on the active tower frequency.
Known Controversies & Unanswered Questions
Legal Finding of Pilot Negligence
Reference ↗While the NTSB report focused on the technical and operational failures of the crew, ATC, and the windshear warning system, a South Carolina jury in a civil lawsuit found the pilots specifically negligent for the decision to continue the approach into a known severe thunderstorm, leading to significant compensation awards for victims' families.