A B767 ENCOUNTERS JETWASH AT LIFTOFF FROM A B757 THAT HAD PREVIOUSLY CROSSED THE RWY AND APPEARED TO HAVE BEEN STOPPED WAITING FOR FURTHER CLRNC. THE B767 SETTLED BACK ONTO THE RWY DURING RECOVERY RESULTING IN A TAILSKID STRIKE.

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WE WERE CLRED FOR TKOF ON MIA RWY 8R AS A PRECEDING ARRIVING B757 HAD JUST CLRED RWY 8R AFTER LNDG ON RWY 8L; AT INTXN M9 7000 FT FROM THE DEP END OF RWY 8R. TKOF WAS NORMAL WITH WINDS OF 150 DEGS/10 KTS AND ROTATION WAS INITIATED AT 144 KTS JUST PRIOR TO M9 INTXN. THE ACFT WHICH HAD CLRED WAS ON TXWY M WITH ENGS POINTING DIRECTLY ACROSS RWY 8R. IT HAD JUST STARTED TO MOVE FROM STOP AS WE CROSSED THROUGH HIS WAKE JETBLAST. OUR ACFT WAS JUST CLR OF THE RWY SURFACE WITH FIXED PITCH WHEN AN ABRUPT AND STRONG ROLL WAS FELT FROM THE JETBLAST WHICH HAD TO BE COUNTERED BY ME WITH IMMEDIATE R AILERON TO BRING WINGS LEVEL. HOWEVER; SINCE THE JETBLAST LASTED ONLY FOR 1 OR 2 SECONDS; THE RESULT WAS TOO MUCH AILERON. I FELT THE R MAIN RECONTACTING THE RWY SURFACE WITH A MODERATE THUMP AFTER WHICH THE ACFT WAS STABLE AND TKOF CLBOUT NORMAL FOR THE ACFT WT OF 329000 LBS. THERE WERE NO INDICATIONS OF ANY ABNORMALITIES DURING EARLY CLB. THE FLT ATTENDANTS; CALLED THE COCKPIT TO INQUIRE ABOUT A BANG THOUGH NONE RPTED A SCRAPING NOISE. I ASSURED THEM ALL APPEARED NORMAL AND WE WERE GOING TO CONTINUE TO LAX. I STRONGLY FELT THE NOISE WAS INDEED FROM TIRE CONTACT WITH THE RWY. AFTER ARRIVING LAX; I WENT OUTSIDE THE ACFT TO CONFIRM MY DETERMINATION. I DID FIND A SCRAPE ON THE TAILSKID METAL PAD BUT THE INDICATOR ON THE TAILSKID TO INDICATE COMPRESSION WAS NORMAL. THERE WAS NO MESSAGE ON EICAS FOR ANY ABNORMALITY. LOG ENTRY WAS MADE TO HAVE THE TAILSKID INSPECTED. THIS INCIDENT BRINGS A SPECIAL AWARENESS FOR THOSE TAKING OFF AND OTHERS THAT HAVE CLRED ACTIVE RWYS TO BE MINDFUL OF JETBLAST AND ITS POSSIBLE AFFECT AT CRITICAL PHASES OF FLT AT TKOF. SUPPLEMENTAL INFO FROM ACN 619011: HIS JETBLAST WAS DIRECTED AT OUR RWY. PERHAPS; AND THIS IS JUST SPECULATION; RIGHT AFTER CLRING OUR RWY; HE HAD STOPPED FOR A MOMENT TO RECEIVE TAXI INSTRUCTIONS FROM GND CTL OR TO TALK TO RAMP CTL. IN ANY CASE; HE MUST HAVE PUSHED UP HIS PWR JUST BEFORE; OR JUST AS; OUR ACFT PASSED RIGHT BEHIND HIM ON OUR TKOF ROLL. THE FIRST THING I WANTED TO CHK WAS THE CONDITION OF THE ENGS (SO AS TO ALERT PF IF WE WERE HAVING ENG TROUBLE). ALL PARAMETERS WERE IN THEIR NORMAL RANGES. SINCE THE ACFT HAD ONLY FLOWN A FOOT OR TWO OFF THE GND; THE ROCKING CAUSED THE ACFT TO SETTLE BACK DOWN TO THE RWY FOR JUST A MOMENT. (PERHAPS IT SETTLED ONLY ON THE R MAIN GEAR; BUT IT IS JUST AS LIKELY THAT IT SETTLED DOWN ON BOTH.) WE HAD THE FLYING SPD; OF COURSE; SO THE ACFT FLEW RIGHT OUT OF THE WASH; AND SMOOTHLY SO; ONCE WE LEFT THE JETWASH AREA. TOTAL TIME OF TURB: ABOUT 2 1/2 TO 3 SECONDS. I THOUGHT THAT THE CAPT DID AN EXCELLENT JOB OF HANDLING IT. I DID NOT NOTICE ANY OVER-ROTATION. IN MY ESTIMATION; THE CAPT SAVED THE ACFT FROM MORE SUBSTANTIAL AND POTENTIALLY SERIOUS ALT DEVS. LOOKING BACK ON IT; I REMEMBER THAT AS WE WERE CLRED 'ONTO HOLD RWY 8R' BY MIA TWR; A (B757; I THINK) JET WAS XING DOWNFIELD; L TO R. I ALSO REMEMBER THAT BEFORE THE (B757?) TAIL HAD EVEN CLRED THE RWY; TWR STARTED XMITTING OUR TKOF CLRNC CALL. 'HVY; FLY HDG 090 DEGS; CLRED FOR TKOF RWY 8R.' OF COURSE; THE DOWNFIELD JET WAS COMPLETELY CLR OF OUR RWY BY THE TIME WE RELEASED BRAKES. BUT THE REASON I MENTION THIS IS THAT ONCE THAT DOWNFIELD JET WAS CLR OF OUR RWY; I WASN'T CLOSELY WATCHING HIM ANY MORE. THAT IS; I WAS CONCENTRATING ON OUR (VERY HVY) TKOF PROCS: CALLING OUT AIRSPDS; SCANNING THE ENG INSTS; AND CLRING OUR FLT PATH DOWN THE RWY. LET'S BE FRANK. WITH ALL THE CRITICAL THINGS GOING ON DURING TKOF; IT DOESN'T SEEM AN EFFECTIVE PRIORITIZATION OF TASKS FOR THE PNF TO TRACK THE MOVEMENTS OF SOME OTHER JET ON THE FIELD: A JET SMALLER THAN OURS; NO LESS; WITH CONSIDERABLY LESS THRUST (IE; NOT SOME BIG B747; FOR EXAMPLE); A JET THAT; FURTHERMORE; HAD FULLY CLRED OUR RWY AND WAS NO LONGER AN INCURSION FACTOR OR COLLISION FACTOR; A JET WHOSE FUTURE POS (AND ALIGNMENT RELATIVE TO OUR RWY) WE WOULD HAVE NO WAY OF KNOWING AT THE TIME WE RELEASED BRAKES FOR TKOF ROLL. SO; FRANKLY SPEAKING; AS I SAID; I WASN'T LOOKING AT THAT JET ONCE IT CLRED THE RWY. IT HAD MOVED BEYOND THE SCOPE OF MY TKOF SCAN PERIPHERAL VISION; AND THUS I WASN'T IMMEDIATELY AWARE OF THE SOURCE OF THE TURB. THE CAPT; AS I SAID; KNEW THE TURB SOURCE RIGHT AWAY. HE HELD THE ACFT FROM MORE SEVERE ALT DEVS; AND FLEW US OUT OF THE WASH. AFTER LNDG; WE INSPECTED THE BOTTOM SURFACE OF THE TAILSKID'S METALLIC 'BLOCK' BUMPER. THE METAL BLOCK DID NOT APPEAR TO HAVE ANY SIGNIFICANT WEAR. HOWEVER; IT DID HAVE A SHINY LOWER SURFACE; INDICATING FAIRLY RECENT ABRASION. EVERY OTHER ASPECT OF THE TAILSKID ASSEMBLY APPEARED NORMAL: NORMAL TAILSKID STRUT; NO LEAKS OR CRACKS; AND NO EXTENSION. NO 'POPPING OUT' OF THE TAILSKID LOW PRESSURE INDICATOR; (METALLIC POP-OUT TAB). NOTE: UNDERSIDE OF L AND R ENG COWLINGS WERE NORMAL AS WELL. IN SUMMARY; IT APPEARED THAT THE ONLY THING THAT HAPPENED TO THE ACFT WAS MILD TAILSKID CONTACT WITH THE RWY UPON TKOF; AND THE SLIGHT SCRAPING OF THE BOTTOM SURFACE OF THE TAILSKID BLOCK (BUMPER). THIS RPT WOULDN'T BE COMPLETE WITHOUT ALSO LOOKING AT WHY THAT B757 AT MIA WAS STOPPED CLOSE TO OUR RWY IN THE FIRST PLACE. WAS HE TRYING TO BREAK INTO A CONGESTED GND CTL FREQ; STOPPING HIS JET UNTIL CLRNC COULD BE OBTAINED? PROBABLY. WAS HE TRYING TO BREAK IN ON A CONGESTED RAMP FREQ TO GET INSTRUCTIONS AND BE SURE HE WAS GIVING GND CTL HIS (CORRECT) ULTIMATE DEST? WAS HE STOPPING HIS JET SO THAT THE MIA FOLKS HAD AN OPPORTUNITY TO TELL HIM WHETHER THE INFO THEY GAVE HIM THE FIRST TIME; 25 MINS AGO DURING AIRBORNE GATE ASSIGNMENT IS STILL CURRENT? BEFORE ANY HINT OF SCRUTINY COMES ON THE B757 CREW; I FEEL WE MUST ASK; 'CAN WE SIMPLIFY THE TAXI-IN PROCESS; PERHAPS ELIMINATE REDUNDANT RADIO CALLS; OR AT LEAST AUTOMATE SOME OF THE 'RADIO DISCUSSIONS AFTER LNDG.' WOULD THIS NOT ONLY HELP AVERT FUTURE INCIDENTS LIKE OURS; BUT ALSO SAVE FUEL AS WELL? CAPT LATER MADE A GOOD OBSERVATION: MANY ACFT WOULD HAVE BEEN WELL UP INTO THE AIR BY THE TIME THEY CROSSED DIRECTLY BEHIND ANY DOWNFIELD ACFT THAT HAD JUST CLRED THE RWY. ONLY VERY HVY ACFT ARE GOING TO STILL BE ON THE RWY THAT FAR DOWNFIELD. PERHAPS THAT IS WHY INCIDENTS LIKE OURS DON'T HAPPEN MORE OFTEN. BUT THEY ARE POTENTIALLY SERIOUS ONES. GIVEN THE HIGH SPDS OF JETWASH; UP TO 4 TIMES THE XWIND LIMITS OF OUR ACFT; PERHAPS THESE INCIDENTS SHOULD RECEIVE THE SAME SCRUTINY AS 'RWY INCURSIONS.' AFTER EXPERIENCING THIS INCIDENT; I SHALL RECONSIDER THE IMPORTANCE OF JETBLAST FROM NEARBY ACFT; EVEN FROM SMALLER ACFT. CALLBACK CONVERSATION WITH RPTR FROM ACN 619011 REVEALED THE FOLLOWING INFO: NO DAMAGE WAS FOUND TO THE ACFT BY MAINT. THE TAILSKID WAS REPAINTED. CONCERN WAS EXPRESSED AGAIN ABOUT THE NEED TO VERIFY THE PREVIOUSLY ASSIGNED ARR GATE AND THE FREQ CONGESTION THAT CAUSES DELAYS IN TURNING ON TO THE PARALLEL TXWY AFTER XING OR EXITING THE RWY.