LR35A ADVISED RWY WAS COVERED WITH THREE FOURTHS INCH OF SNOW. LATER IT WAS DISCOVERED THERE WERE TWO AND ONE HALF PLUS SOME MUCH DEEPER BERMS WHERE SNOW PLOWS HAD MADE TURNS. SHORTLY AFTER TKOF; ENGS ALMOST FLAMED OUT AND THE ACFT ROLLED UNCTLABLY ABOUT 45-60 DEGS. SUDDENLY; CTL WAS REGAINED FOR NO APPARENT REASON. FLC NOTICED SNOW WAS QUITE DEEP BUT TOOK NO ACTION.

Narrative

BFI ATIS AND GND ADVISED THREE FOURTH INCH OF ICE AND SNOW ON RWY. AFTER TKOF; ENGS ALMOST FLAMED OUT. OPS WENT OUT AND MEASURED TWO AND ONE HALF INCHES OF SNOW AND ICE. SEATTLE DOES NOT GET MUCH SNOW AND ICE. AFTER TALKING WITH THE TWR PEOPLE; THEY SAID THE SNOW REMOVAL PEOPLE ARE CONTRACT WORKERS AND DO NOT KNOW HOW TO RPT SNOW OR ICE DEPTH. THE NOSEWHEEL ON A LEARJET 35A CAN ONLY TAKE THREE FOURTH INCH OF SNOW OR ICE. SOME OF THE BLAME IS ON ME; BUT THE TWR OR COUNTY NEEDS TO TRAIN BETTER. WE WERE CLRED ONTO RWY 31L AT A10 FOR A BACK TAXI TO THE END. AS WE TAXIED INTO THE RWY ENVIRONMENT; LOOKING TO THE R; FO AND I BOTH NOTICED 2 SNOW REMOVAL VEHICLES AND 1 COUNTY TRUCK ABOUT 1500 FT N OF US. AS WE MADE OUR WAY ONTO THE RWY; MY FO AND I BOTH COMMENTED ON HOW DEEP SOME TRACKS FROM A LNDG ACFT WERE IN THE SNOW. IT APPEARED THE SNOW WAS GETTING DEEPER AS WE BACK TAXIED SO I TURNED ACFT AROUND FOR TKOF ABOUT 500 FT SHORT OF THE END OF RWY 31L. IT WAS A NORMAL TKOF BRIEF EXCEPT FOR THE GEAR UP CALL WHICH WOULD BE DELAYED FOR ADDITIONAL SNOW AND ICE TO BE SPUN OFF THE GEAR. THE PWR LEVELS WERE ADVANCED TO 93.2 N1 AND ALL INDICATIONS APPEARED TO BE NORMAL. AT ABOUT 95-100 KTS THE SOUND OF THE SNOW AND ICE STRIKING THE PLANE WAS LIKE NO OTHER I HAVE EVER HEARD. AT 110 KTS THE LNDG LIGHT ILLUMINATED MULTIPLE SNOW BERMS WHERE I BELIEVE THE COUNTY TRUCKS TURNED AROUND TO EXIT THE RWY PRIOR TO OUR DEP. AS THE ACFT R MAIN IMPACTED THE FIRST BERM; WE LOST 5 KTS OF AIRSPD. THE PLANE STARTED TO GAIN THAT BACK WHEN IT HIT THE SECOND BERM AND LOST ANOTHER 5 KTS. BY NOW; DIRECTIONAL CTL WAS BECOMING DIFFICULT. IN AN EFFORT TO REDUCE THE AMOUNT OF SNOW AND ICE IMPACTING THE WING AND BEING INGESTED INTO THE ENGS; I STARTED TO TAKE SOME WT OFF THE NOSEWHEEL WITH AFT ELEVATOR. FO CALLED V1 AT 122 KTS; THEN ROTATE AT 134 KTS. AS THE PLANE BROKE GND IT WAS AS THOUGH WE HAD CUT FREE OF A GIANT ANCHOR. THE PLANE ALMOST LURCHED FORWARD. THE FIRST 10 FT OF THE CLB OUT WAS NORMAL; THEN SOMETHING WENT TERRIBLY WRONG. THE ACFT STARTED TO BANK R. I APPLIED ABOUT 30 DEGS L AILERON; BUT THIS HAD NO EFFECT. AS THE PLANE CONTINUED ITS UNCTLED R BANK THROUGH 20 DEGS (APPROX); I APPLIED FULL L AILERON; STILL WITH NO EFFECT. SPD WAS NOW V2-10; BANK ANGLE SOMEWHERE BTWN 45-60 DEGS; ALT 75 FT (APPROX). WITH NO ROLL CTL OF THE ACFT; ALL I COULD DO IS TRY TO KEEP THE ACFT FROM STALLING WITH PITCH. THEN ALL OF A SUDDEN WITH NO NOISE; NO VIBRATION; CTL OF THE ACFT RETURNED. THE PLANE STARTED TO RESPOND TO THE L ROLL COMMAND; BUT NOW THE STICK SHAKER STARTED. I CONTINUED THE ROLL; BUT UNLOADED THE TAIL JUST ENOUGH TO GO INTO AND OUT OF THE SHAKER (WINDSHEAR RECOVERY). I CONTINUED THE ROLL TO PARALLEL THE RWY FOR OBSTACLE CLRNC AND ACCELERATED TO V2 FOR STALL RECOVERY. THE REST OF THE CLB OUT WAS NORMAL.