MD-11
Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Training / Qualification
Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Environment - Non Weather Related; Human Factors; Procedure; Weather
When we arrived at the aircraft; we discovered it was covered in frost. There was freezing fog at the airport. We conducted our pre-flight and de-iced in the gate. We discovered a maintenance issue on taxi out that required a return to the gate. While waiting for the maintenance work to be completed; I asked the First Officer (FO) to check out the plane to see if we might need more de-icing. There was no precipitation so I did not think we needed further de-icing. The FO made a thorough inspection and then I did as well. What we saw was surprising. The top of the wings; top of the tail and fuselage were all clear of frost. The underside of the wing; though; had a great deal of frost. The frost on the lower wing was thick and extended out beyond the fuel tanks. There was frost on the lower area of the winglet. There was also frost covering the underside of the tail. Neither the FO; the mechanic; nor I had ever seen that much frost on the underside of a wing to tail. The mechanic then told us that the plan had sat there for three and a half days in temperatures well below freezing and in freezing fog. We had the underside of the wing and tail de-iced with type 1 fluid. Takeoff and flight was normal.The plane was sitting idle for more than three days in below freezing temperatures and freezing fog. Frost was covering the whole plane including the landing gear. It obviously needed de-icing and we followed our procedures. But our procedures do not have a step for the pilots to exit the plane and check the de-icing results. Had we not returned to the gate; we would have never noticed the excessive frost on the underside of the wing.I think mechanics and de-icing crews should be trained to de-ice the whole plane when the plane has been cold soaked. In the future; I will specifically instruct the crew to de-ice the lower surfaces if the plane has been sitting and is covered with frost. I called [dispatch] and expressed my concerns.
MD-11 Captain reported finding a considerable amount of frost on the undersides of the wing and tail surfaces after the aircraft had sat on the ground for several days in freezing fog conditions. Reporter was concerned that normal de-ice procedures do not address this issue.