Narrative:

Cold soaked fuel frost has occurred on a number of company flights. The fom requires the captain to check for cold soaked fuel frost on flights over 2 hours. As a result; it has gone undetected and many of our pilots are not aware of the risk. It occurs on the classic and ng on flights well under two hours in a variety of WX conditions. I am submitting this report to increase awareness and encourage checks for cold soaked fuel frost on every leg. Cold soaked fuel frost encountered flight from ZZZ; flight 1:54 hours. Inbound aircraft from ZZZ1. During preflight as part of my own personal check of the aircraft; I checked the wing from one row behind the emergency exit window. Cold soaked fuel frost covered a large portion of both wings. WX at the time was clear; 66F. I notified the captain who also looked at the wing. After passenger boarding was complete I went to the back and again checked the wing from one seat behind the emergency exit. Only condensation remained and we departed without delay. Again on following flight in route from to ZZZ2; flight 2:09 the fuel temperature was -20. There was rain on the approach and 37F. During the 25 minute turn I again went back to check the wing and found patches of frost 3 X 2 inches on both wings. The a flight attendant; also a private pilot; reported the left side was melting more rapidly than the right. After boarding I looked at the wings and it looked as though only condensation remained but I asked the captain to double-check. After a few minutes the captain checked the wing from the same location determined the cold soaked fuel frost had melted and we once again departed without delay. 'Such ice is difficult to see and in many instances cannot be detected other than by touch with the bare hand or by means of a special purpose ice detector such as a ground ice detection system (gids). A layer of slush on the wing cannot be assumed to flow off the wing on takeoff and must be removed.' transport canada; tp 10643E; 7TH edition; dec 2004. Additionally I have had cold soaked fuel frost: 1:20 hour flight to ZZZ3; 80 degrees F; clear sky. 1:05 hour flight to ZZZ4; 70 degrees F; clear sky. ZZZ5; ZZZ6 and others. Checks from 1-2 seats behind the emergency exit need to be incorporated into every leg no matter the duration of the previous flight. Ladders need to be provided to allow the crew to conduct a tactile or hands on check of the wing when cold soaked fuel frost occurs. It can be clear ice or difficult to determine if it is condensation or ice. More needs to be done to increase awareness of cold soaked fuel frost on the B737. Procedural changes may need to be incorporated to prevent crews from inadvertently departing with unknown frost/ice/slush from cold soaked fuel frost on the wing.

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Original NASA ASRS Text

Title: A B737 PILOT SUGGESTS FLIGHT CREWS INSPECT AIRCRAFT FOR COLD SOAKED FUEL FROST (CSFF) AFTER FLIGHT OF LESS THAN TWO HOURS. AIR CARRIER PROCEDURES AND TOOLS ARE NOT AVAILABLE FOR CSFF INSPECTIONS DURING PREFLIGHT.

Narrative: COLD SOAKED FUEL FROST HAS OCCURRED ON A NUMBER OF COMPANY FLIGHTS. THE FOM REQUIRES THE CAPTAIN TO CHECK FOR COLD SOAKED FUEL FROST ON FLIGHTS OVER 2 HOURS. AS A RESULT; IT HAS GONE UNDETECTED AND MANY OF OUR PILOTS ARE NOT AWARE OF THE RISK. IT OCCURS ON THE CLASSIC AND NG ON FLIGHTS WELL UNDER TWO HOURS IN A VARIETY OF WX CONDITIONS. I AM SUBMITTING THIS REPORT TO INCREASE AWARENESS AND ENCOURAGE CHECKS FOR COLD SOAKED FUEL FROST ON EVERY LEG. COLD SOAKED FUEL FROST ENCOUNTERED FLIGHT FROM ZZZ; FLIGHT 1:54 HRS. INBOUND AIRCRAFT FROM ZZZ1. DURING PREFLIGHT AS PART OF MY OWN PERSONAL CHECK OF THE AIRCRAFT; I CHECKED THE WING FROM ONE ROW BEHIND THE EMERGENCY EXIT WINDOW. COLD SOAKED FUEL FROST COVERED A LARGE PORTION OF BOTH WINGS. WX AT THE TIME WAS CLEAR; 66F. I NOTIFIED THE CAPTAIN WHO ALSO LOOKED AT THE WING. AFTER PAX BOARDING WAS COMPLETE I WENT TO THE BACK AND AGAIN CHECKED THE WING FROM ONE SEAT BEHIND THE EMERGENCY EXIT. ONLY CONDENSATION REMAINED AND WE DEPARTED WITHOUT DELAY. AGAIN ON FOLLOWING FLIGHT IN ROUTE FROM TO ZZZ2; FLIGHT 2:09 THE FUEL TEMPERATURE WAS -20. THERE WAS RAIN ON THE APPROACH AND 37F. DURING THE 25 MINUTE TURN I AGAIN WENT BACK TO CHECK THE WING AND FOUND PATCHES OF FROST 3 X 2 INCHES ON BOTH WINGS. THE A FLIGHT ATTENDANT; ALSO A PRIVATE PILOT; REPORTED THE LEFT SIDE WAS MELTING MORE RAPIDLY THAN THE RIGHT. AFTER BOARDING I LOOKED AT THE WINGS AND IT LOOKED AS THOUGH ONLY CONDENSATION REMAINED BUT I ASKED THE CAPTAIN TO DOUBLE-CHECK. AFTER A FEW MINUTES THE CAPTAIN CHECKED THE WING FROM THE SAME LOCATION DETERMINED THE COLD SOAKED FUEL FROST HAD MELTED AND WE ONCE AGAIN DEPARTED WITHOUT DELAY. 'SUCH ICE IS DIFFICULT TO SEE AND IN MANY INSTANCES CANNOT BE DETECTED OTHER THAN BY TOUCH WITH THE BARE HAND OR BY MEANS OF A SPECIAL PURPOSE ICE DETECTOR SUCH AS A GROUND ICE DETECTION SYSTEM (GIDS). A LAYER OF SLUSH ON THE WING CANNOT BE ASSUMED TO FLOW OFF THE WING ON TAKEOFF AND MUST BE REMOVED.' TRANSPORT CANADA; TP 10643E; 7TH EDITION; DEC 2004. ADDITIONALLY I HAVE HAD COLD SOAKED FUEL FROST: 1:20 HR FLIGHT TO ZZZ3; 80 DEGS F; CLEAR SKY. 1:05 HR FLIGHT TO ZZZ4; 70 DEGS F; CLEAR SKY. ZZZ5; ZZZ6 AND OTHERS. CHECKS FROM 1-2 SEATS BEHIND THE EMERGENCY EXIT NEED TO BE INCORPORATED INTO EVERY LEG NO MATTER THE DURATION OF THE PREVIOUS FLIGHT. LADDERS NEED TO BE PROVIDED TO ALLOW THE CREW TO CONDUCT A TACTILE OR HANDS ON CHECK OF THE WING WHEN COLD SOAKED FUEL FROST OCCURS. IT CAN BE CLEAR ICE OR DIFFICULT TO DETERMINE IF IT IS CONDENSATION OR ICE. MORE NEEDS TO BE DONE TO INCREASE AWARENESS OF COLD SOAKED FUEL FROST ON THE B737. PROCEDURAL CHANGES MAY NEED TO BE INCORPORATED TO PREVENT CREWS FROM INADVERTENTLY DEPARTING WITH UNKNOWN FROST/ICE/SLUSH FROM COLD SOAKED FUEL FROST ON THE WING.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.