Background
A scheduled flight from Washington, DC to Fort Lauderdale, FL was delayed for over one hour during moderate to heavy snowfall while the runway was closed for snow removal. The aircraft was deiced with a heated ethylene glycol and water solution; engine inlet plugs or pitot static covers were not installed.
Pre-takeoff Events
Contrary to procedures, reverse thrust was used to assist a tug during pushback from the gate, blowing snow. After pushback, the flight was delayed an additional 49 minutes while snow continued in subfreezing conditions. During the wait, the aircraft was positioned near the exhaust of the aircraft ahead.
Takeoff and Accident
During takeoff, the engine pressure ratios (EPRs) were set for 2.04, but an anomaly was noted in engine instrument readings. The captain elected to continue the takeoff. The aircraft lifted off approximately 2,000 feet and 15 seconds past the normal takeoff point. After liftoff, it initially climbed but failed to accelerate. The stall warning stickshaker activated shortly after takeoff and continued until the aircraft settled, struck a bridge and several vehicles, then plunged into a frozen river.
Investigation Findings
Investigation revealed engine inlet pressure probes became blocked with ice, resulting in erroneous EPR indications. Additionally, there was a possible pitchup due to snow/ice frozen on the wings. No runway distance markers were available, and the crew had limited cold weather operational experience.