NTSB · Safety Recommendation
Safety Recommendation A-80-113
Recommendation
THE NTSB RECOMMENDS THAT THE FEDERAL AVIATION ADMINISTRATION: INITIATE A STUDY OF THE EFFECTIVENESS OF ETHYLENE GLYCOL-BASED DEICING FLUID CONCENTRATIONS AS AN ANTI-ICING AGENT UNDER DIFFERING ICING AND SNOW CONDITIONS.
Safety Issue and Context
ON FEBRUARY 12, 1979, AN ALLEGHENY AIRLINES NORD 262 CRASHED ON TAKEOFF FROM CLARKSBURG, WEST VIRGINIA. THE ACCIDENT RESULTED IN TWO FATALITIES AND SEVEN SERIOUS INJURIES. AT THE TIME OF TAKEOFF, THERE WERE LIGHT SNOW SHOWERS AT THE AIRPORT WITH AN ESTIMATED ACCUMULATION RATE OF APPROXIMATELY 1 INCH PER HOUR. DEICING OF THE AIRCRAFT, WITH A 78-PERCENT SOLUTION OF AN ETHYLENE GLYCOL-BASED DEICING FLUID AND WATER, WAS COMPLETED 25 TO 40 MINUTES PRIOR TO TAKEOFF. WITNESSES REPORTEDLY SAW SNOW ON THE EXPOSED HORIZONTAL SURFACES OF THE AIRCAFT WHEN IT TAXIED OUT.
THE PROBABLE CAUSE OF THE ACCIDENT WAS DETERMINED TO BE, IN PART, THE LOSS OF LATERAL CONTROL AND LIFT DUE TO SNOW ON THE WINGS AND EMPENNAGE WHEN THE AIRCRAFT CLIMBED OUT OF GROUND EFFECT. THE PRESENCE OF FROZEN SNOW ON THE UPPER HORIZONTAL AIRFOIL SURFACES WAS CONFIRMED BY PHOTOGRAPHS AFTER THE ACCIDENT. ON FEBRUARY 18, 1980, A REDCOAT AIR CARGO, LTD., BRISTOL BRITTANIA 253, CRASHED SHORTLY AFTER TAKEOFF FROM LOGAN INTERNATIONAL AIRPORT, BOSTON. THE ACCIDENT RESULTED IN SEVEN DEATHS AND ONE SERIOUS INJURY. LIGHT SNOW HAD FALLEN THROUGHOUT THE PERIOD OF FLIGHT PREPARATION, TAXI, AND TAKEOFF AT A RATE OF BETWEEN 0.5 AND 0.8 INCH PER HOUR.
THE AIRCRAFT HAD BEEN DEICED WITH A 30-PERCENT SOLUTION OF AN ETHYLENE GLYCOL-BASED DEICING FLUID 45 TO 60 MINUTES PRIOR TO TAKEOFF. EVIDENCE INDICATES THAT WET SNOW, WHICH ACCUMULATED ON THE WINGS AND HORIZONTAL STABILIZER PRIOR TO TAKEOFF, WAS A MAJOR FACTOR IN THIS ACCIDENT.
Response History
May 10, 1983 · NTSB Correspondence · FAA
The results of the FAA study of the effectiveness of gylycol-based freeze point depressants as both deicing and anti-icing agents were published in the FAA AC 20- 117. As expressed in our letter of 11/12/82 the Board appreciated the efforts of Data Source: NTSB Recommendations to FAA and FAA Responses the FAA to issue the AC before the winter season. In the letter we also expressed the belief that the FAA should provide positive guidance to operators regarding the deicing/antiicing methods which will provide the best possible results under typical ambient conditions and urged that more conservative assumptions be made with respect
to certain data presented in the appendices to the draft advisory circular. We were pleased to note that the appendices have been modified as we suggested and that the text concerning acceptable practices has been expanded to provide further guidance for operational and maintenance personnel finally, we are encouraged by your statement that you will assist in the development of specific industry standards and will publish additional advisory information as necessary. In view of the above, we shall classify Safety Recommendation A-80-113 as closed--acceptable action.
March 11, 1983 · Recipient Response · FAA
FAA LETTER: AS A RESULT OF FINDINGS DERIVED FROM RESEARCH AND DEVELOPMENT (R&D) EFFORTS CONDUCTED BY THE FEDERAL AVIATION ADMINISTRATION (FAA), ADVISORY CIRCULAR (AC) 20-117, TITLED "HAZARDS FOLLOWING GROUND DEICING AND GROUND OPERATIONS ON CONDITIONS CONDUCIVE TO AIRCRAFT ICING," WAS ISSUED ON DECEMBER 17, 1982. THE PURPOSE OF THIS IS TO EMPHASIZE THE "CLEAN AIRCRAFT CONCEPT" FOLLOWING GROUND DEICING AND GROUND OPERATIONS IN CONDITIONS CONDUCIVE TO AIRCRAFT ICING AND PROVIDE INFORMATION TO ASSIST IN COMPLIANCE. A COPY OF THIS AC WAS DISTRIBUTED TO ALL SEGMENTS OF THE AVIATION COMMUNITY INCLUDING AIRCRAFT OWNERS AND OPERATORS.
CONCLUSIONS TO DATE REMAIN THAT SOME FINITE TIME FOR THE LIFE OF THE DEICING FLUID CAN BE ESTIMATED IF SPECIFIC INFORMATION IS AVAILABLE. HOWEVER, BECAUSE OF THE NUMEROUS FACTORS THAT CAN INFLUENCE THESE ESTIMATES AND THE INABILITY OF OPERATORS TO QUANTIFY THESE FACTORS, IT IS NOT PRACTICAL TO USE THAT TECHNIQUE AS A SUBSTANCE FOR PRETAKEOFF INSPECTION. THIS SUBJECT IS DISCUSSED IN DEPTH IN THE AC, AND THE RESULTS OF THE R&D ARE ALSO CONTAINED THEREIN.