FA-28 INITIAL DEICING PROC WAS NOT SATISFACTORY. ACFT CONFIGN DURING DEICE PROC REQUIRES FLAPS BEING EXTENDED TO THE TKOF POS TO CATCH ACCRUED SNOW DEPOSITS.

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ACFT WAS AT GATE IN PIT FOR 1 HR WITH TAIL POINTING N. SNOW WAS FALLING WITH A N WIND OF ABOUT 15 KTS. WE LEFT THE GATE AND TAXIED TO THE DEICING AREA WITH FLAPS UP AS PER COMPANY PROCS. WE WERE DEICED WITH TYPE I AND II FLUIDS; AND THE GND CREW COMPLETED THE POST-APPLICATION CHK. AFTER DEICING; THE FLAPS WERE CYCLED AND THEN SET TO 18 DEGS FOR TKOF. JUST PRIOR TO TKOF I WENT BACK TO THE CABIN TO CONDUCT THE REQUIRED PRE-TKOF CHK FROM THE CABIN WINDOWS. ALTHOUGH THE WING UPPER SURFACES WERE 'CLEAN;' THE FORWARD AREA OF THE FLAP UPPER SURFACES (BOTH SIDES) HAD SUBSTANTIAL AMOUNTS OF SNOW. OBVIOUSLY WE RETURNED FOR ANOTHER DEICING; THIS TIME WITH FLAPS EXTENDED. IF THIS HAD OCCURRED AT NIGHT I DO NOT THINK I WOULD HAVE BEEN ABLE TO SEE THE SNOW ON THE FLAPS. I BELIEVE THAT WHILE THE ACFT WAS AT THE GATE SNOW BLEW INTO THE SPACE BTWN THE FLAP UPPER SURFACE AND WING LOWER SURFACE. SINCE WE DEICED THE AIRPLANE WITH FLAPS UP; THIS SNOW WAS NOT REMOVED BY THE DEICING FLUID OR VISIBLE TO THE GND CREW. THE SNOW WAS ONLY VISIBLE AFTER FLAPS WERE EXTENDED FOR TKOF. IN ADDITION TO THE OBVIOUS AERODYNAMIC PENALTIES; THIS SNOW MAY HAVE BEEN A FOREIGN OBJECT DAMAGE HAZARD DUE TO THE LOCATION OF THE ENGS AFT OF THE FLAPS. I BELIEVE THAT THIS ACFT TYPE (FOKKER 28) SHOULD BE DEICED WITH FLAPS IN TKOF POS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: THE AIRLINE MGMNT POLICY HAS NO SET RULING ON THE SETTING OF THE FLAPS DURING A DEICING PROC. THEY HAVE A RULING ON THE F-100 AND 'BOUNCE AROUND' WITH VARIABLE FLAP SETTINGS FOR THAT ACFT DURING DEICING BUT NO SPECIFIC POS HAS BEEN SETTLED UPON. THE AIRLINE WANTS THE MANUFACTURER TO STATE THE GUIDANCE ON THIS FLAP ISSUE AND WILL PROBABLY DO THE SAME REGARDING THIS FA-28 ACFT. RPTR HIGHLY RECOMMENDS THAT THESE FLAPS BE EXTENDED TO AT LEAST THE TKOF POS FOR DEICING PURPOSES.