By Jeff Marcus, Chief, NTSB Safety Recommendations Division
Forty years ago, on Jan. 13, 1982, a Boeing 737 jetliner crashed into Washington, DC’s 14th Street Bridge and plunged into the freezing Potomac River after departing National Airport during a snowstorm. The crash killed 73 of the 79 people aboard the airplane and 4 people in cars on the bridge; 4 others on the bridge were injured. A total of five passengers and a flight attendant escaped the airplane into the freezing, ice-filled Potomac River and clung to wreckage.
About 20 minutes after the crash, a National Park Service helicopter arrived. Showing remarkable flying skills, the pilot and paramedic worked so close to the water that at times the helicopter’s skids dipped beneath the surface. They managed to pull four of the survivors to shore. As a fifth survivor lost her grip on the helicopter’s lifeline, Lenny Skutnik—one of hundreds of bystanders—dove into the icy water and brought her to the riverbank.
A sixth survivor of the impact had taken the lifeline and flotation rings from the helicopter and passed them to others. When the helicopter returned for him, he was gone. The 14th Street Bridge is today named in honor of that passenger, Arland D. Williams.
NTSB investigators found that after traveling almost half a mile farther down the runway than was typical for a normal takeoff, the airplane lifted off and attained a maximum altitude of only about 350 feet before crashing into the bridge, which was less than a mile from the end of the runway. While the airplane was on its takeoff roll, the first officer remarked several times, “that don’t seem right, does it? Ah, that’s not right. That don’t seem right.” The captain did not respond.
The NTSB’s investigation identified numerous errors related to safely flying in snowy and icy conditions.
- Though the outside temperature was well below freezing and snow was falling, the crew did not activate the engine anti-ice system that prevents sensors in the engines from freezing and giving incorrect engine power readings. Although the pilots set the engines to the correct power setting, the NTSB’s analysis showed the engines were actually operating with substantially less power than was needed.
- After leaving the gate, the aircraft waited in a taxi line with many other aircraft for 49 minutes before reaching the takeoff runway. The pilot decided not to return to the gate for reapplication of deicing, fearing that the flight’s departure would be even further delayed. More snow and ice accumulated on the wings during that period.
- While waiting in line to take off, the pilots decided to maneuver closely behind a DC‑9 that was taxiing just ahead of them, mistakenly believing that the heat from the DC-9’s engines would melt the snow and ice that had accumulated on flight 90’s wings. This action, which went specifically against flight-manual recommendations for an icing situation, contributed to the icing on the Air Florida jet. The exhaust gases from the DC-9 turned the snow into a slush mixture that froze on the wings and the engine.
- Although the crew was aware of the ice and snow on the wings, they decided to take off.
Air Florida flight 90 was just one of numerous airframe-icing-related crashes we’ve investigated. Between 1982 and 1997, we investigated eight fatal accidents of aircraft flown by professional flight crews that encountered icing conditions. Other professionally crewed flights were among the numerous icing accidents we investigated through April 2011, when the final report on such an accident was issued. These crashes killed 265 people. Similar problems were found by the Canadian Transportation Safety Board where two accidents in 1985 and 1989 killed 280 passengers and crew.
As a result of these accidents, we’ve issued several recommendations covering a variety of topics, including the following:
- Deicing fluid properties
- The number of minutes after which a plane can safety take off after being deiced
- Airport congestion and the time needed for air traffic control clearance, which can delay takeoff beyond when deicing fluid is effective
- The importance of deicing engine instruments that are used to set the proper engine power
- Prolonged autopilot use in icing conditions can mask developing problems with controllability until it is too late to avoid a crash
- Icing on swept wing aircraft (including most airliners) can cause an airplane to pitch up uncontrollably, leading to a stall
- Small amounts of ice on an airplane wing (comparable to the roughness of sandpaper) disrupt airflow and reduce the airplane wing’s ability to hold up the airplane
- FAA certification standard revisions for airplanes approved to fly in icing conditions
- Increasing stall speed in icing conditions
Because the NTSB identified airframe icing as a significant threat to aviation safety, it was on our Most Wanted List of Transportation Safety Improvements for 14 years.
After researching how ice forms on airplane wings in flight, and how that ice affects airplane performance, the FAA revised the standards for airplanes certified for flight in icing conditions. Pilot training and flight procedures were improved, and more attention was paid to minimizing the time between deicing and taking off.
Although the NTSB still investigates aviation accidents involving icing, the numbers are down drastically. We have not investigated a fatal icing-related crash involving a professional flight crew since the February 16, 2005, crash of a Cessna Citation 560 in Pueblo, Colorado.
At the NTSB, we draw knowledge from tragedy to improve the safety of all. The knowledge gained from our investigations of icing accidents, such as Air Florida flight 90, identified the actions needed to improve the safety of everyone who flies.