Narrative:

Increased deicing for cold soaked fuel frost. Csff on 3 out of 4 flights; mco tanker in fuel; or fob. Mco 58 degrees. During exterior preflight discovered csff covering 60% of both wings. I asked the ramper for a ladder to do a tactile check and none was available. I asked to use the belt loader and they said they would get in trouble. The captain called ops for hot water deice. When the agent came down with the loadsheet; he asked the captain if something could have been done earlier and continued to discuss the delay (making us even later). Despite the fact the agent was still calling for passenger the delay was written up to deicing. Flight to ZZZ the next day. Aircraft tankered in fuel. Nothing on aircraft during exterior preflight including inspection of the wings from the cabin. Temp was 0 and winds gusting to 25. It began to very lightly snow; so I would have asked the captain to deice based on the 'one snowflake' requirement. I went to the cabin again and asked the passengers to step into the aisle; so I could get a good look at the wings. A few minutes later the captain went outside and checked the aircraft. He climbed up on the belt loader from the aft cargo. From his vantage point he found a large modified oval patch above the fuel bladder with snow adhering only to that area. He said it was not on the baggage carts; tug; leading edges; nose; etc. Flight back in ZZZ 4 hrs later on thru-flight (different captain). Clear; -1; 250/08 I think. Tankered in fuel to ZZZ and while boarding I went back to check the wings from the cabin and found csff. I also checked from the aft galley door that provided a much better view thanks to good lighting on the ramp. The captain did an exterior preflight; but I don't know if he used a ladder or belt loader to look at the top of the wings. We called for deice with type one and took about a 30 minute delay to have the wings sprayed. Other aircraft had to deice for csff after us. Correct the most recent winter ops bulletin and fom that continue to mislead crews that csff only occurs on 'long flights' or flights of 'over 2 hours.' inform crews; the length of flight is irrelevant and misleading to our crews that it is not necessary to check. The fuel temperature and amount of fuel onboard are the biggest factors. (Look at the fuel temp in the descent and whenever you are tinkering.) csff can begin to develop in the descent or can take up to 20 minutes to develop after landing. Csff can be clear. It can melt on the bottom of the wing because of heat radiated from the ground; but still remain frozen on top of the wing. Environmental conditions such as humidity contribute; but can vary greatly as can temperature. The first ZZZ flight demonstrated it only takes a very thin layer of csff to bond any precipitation to the wing and can occur after the preflight and after a cabin check.callback conversation with reporter revealed the following info: reporter stated the problem of csff only became an issue when the air carrier instituted the technique of ferrying significant amounts fuel when fuel prices were at their peak and it made more sense to buy more of it at cheaper locations and carry it along even at the cost of burning more fuel on the ferrying legs. In addition to the csff issue itself; problems emerged regarding the availability of deicing equipment at stations where frozen precipitation is essentially never present. They have instituted the use of spraying with hot water to melt the frost; but reporter is concerned that; as long as the cold soaked fuel remains at very cold temperatures; the potential for the water refreezing as clear ice may occur. Of great interest was reporter's observance of water freezing at the trailing edge of the wing following such a hot water deicing procedure. Trailing edge ice is a subject seldom if ever addressed in the literature. Reporter also advised the air carrier involved has modified earlier recommendations; so as to make enroute inspections fo

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Original NASA ASRS Text

Title: B737NG First Officer reports recurring examples of CSFF (Cold Soaked Fuel Frost) on aircraft that tankered fuel into stations with various forms of precipitation or high humidity.

Narrative: Increased deicing for cold soaked fuel frost. CSFF on 3 out of 4 flights; MCO Tanker in fuel; or FOB. MCO 58 degrees. During exterior preflight discovered CSFF covering 60% of both wings. I asked the Ramper for a ladder to do a tactile check and none was available. I asked to use the belt loader and they said they would get in trouble. The Captain called Ops for hot water deice. When the Agent came down with the loadsheet; he asked the Captain if something could have been done earlier and continued to discuss the delay (making us even later). Despite the fact the agent was still calling for passenger the delay was written up to deicing. Flight to ZZZ the next day. Aircraft tankered in fuel. Nothing on aircraft during exterior preflight including inspection of the wings from the cabin. Temp was 0 and winds gusting to 25. It began to very lightly snow; so I would have asked the Captain to deice based on the 'one snowflake' requirement. I went to the cabin again and asked the passengers to step into the aisle; so I could get a good look at the wings. A few minutes later the Captain went outside and checked the aircraft. He climbed up on the belt loader from the aft cargo. From his vantage point he found a large modified oval patch above the fuel bladder with snow adhering only to that area. He said it was not on the baggage carts; tug; leading edges; nose; etc. Flight back in ZZZ 4 hrs later on thru-flight (different Captain). Clear; -1; 250/08 I think. Tankered in fuel to ZZZ and while boarding I went back to check the wings from the cabin and found CSFF. I also checked from the aft galley door that provided a much better view thanks to good lighting on the ramp. The Captain did an exterior preflight; but I don't know if he used a ladder or belt loader to look at the top of the wings. We called for deice with type one and took about a 30 minute delay to have the wings sprayed. Other aircraft had to deice for CSFF after us. Correct the most recent Winter Ops bulletin and FOM that continue to mislead crews that CSFF only occurs on 'long flights' or flights of 'over 2 hours.' Inform crews; the length of flight is irrelevant and misleading to our crews that it is not necessary to check. The fuel temperature and amount of fuel onboard are the biggest factors. (Look at the fuel temp in the descent and whenever you are tinkering.) CSFF can begin to develop in the descent or can take up to 20 minutes to develop after landing. CSFF can be clear. It can melt on the bottom of the wing because of heat radiated from the ground; but still remain frozen on top of the wing. Environmental conditions such as humidity contribute; but can vary greatly as can temperature. The first ZZZ flight demonstrated it only takes a very thin layer of CSFF to bond any precipitation to the wing and can occur after the preflight and after a cabin check.Callback conversation with reporter revealed the following info: Reporter stated the problem of CSFF only became an issue when the air carrier instituted the technique of ferrying significant amounts fuel when fuel prices were at their peak and it made more sense to buy more of it at cheaper locations and carry it along even at the cost of burning more fuel on the ferrying legs. In addition to the CSFF issue itself; problems emerged regarding the availability of deicing equipment at stations where frozen precipitation is essentially never present. They have instituted the use of spraying with hot water to melt the frost; but reporter is concerned that; as long as the cold soaked fuel remains at very cold temperatures; the potential for the water refreezing as clear ice may occur. Of great interest was reporter's observance of water freezing at the trailing edge of the wing following such a hot water deicing procedure. Trailing edge ice is a subject seldom if ever addressed in the literature. Reporter also advised the air carrier involved has modified earlier recommendations; so as to make enroute inspections fo

Data retrieved from NASA's ASRS site as of April 2012 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.