Phoenix Sky Harbor Airport
Aircraft Accident/Incident Report

Phoenix, Arizona 85008
Thursday, April 6, 1995 13:46 MST

MECHANICS IN A BOEING 737 MADE A HIGH SPEED TAXI DOWN RUNWAY 26L TO TEST THE ENGINES AS CESSNA 172N, N737AV, WAS ON FINAL APPROACH TO LAND. THE TOWER CONTROLLER TOLD THE BOEING MECHANICS TO EXIT AT MIDFIELD AND 'CONTINUE IN THE TURN ONTO THE PARALLEL TAXIWAY NO DELAY OFF PLEASE.' ONE MINUTE LATER, THE MECHANICS ASKED TO GO TO THE GATE AND THE CONTROLLER SAID TO CONTACT GROUND CONTROL. AFTER TURNING ONTO THE PARALLEL TAXIWAY, THE BOEING CAME TO A STOP. THE MECHANICS DID NOT CONTACT GROUND CONTROL UNTIL AFTER THE ACCIDENT (1 MINUTE 45 SECONDS LATER). THE TOWER CONTROLLER TOLD THE CESSNA PILOT TO EXIT AT THE SAME TAXIWAY, THEN CONTACT GROUND CONTROL. HE SAID HE CLEARED THE CESSNA ON THE ASSUMPTION THAT THE BOEING WOULD NOT STOP. THE CESSNA 172 EXITED THE RUNWAY AND STOPPED AT THE HOLD SHORT LINE. THE CESSNA WAS TOLD TO TAXI NORTHBOUND CROSSING BEHIND THE BOEING. THE CESSNA MOVED JUST AS THE BOEING BEGAN POWERING UP TO MOVE AND THE JET BLAST RESULTED IN SUBSTANTIAL DAMAGE TO THE CESSNA. THE MECHANICS SAID THEY STOPPED AFTER THE TURN AND SET THE BRAKES WHILE TUNING THE RADIO TO GROUND. THEY SAID THEY POWERED UP TO 40 TO 50 PERCENT N1 TO BEGIN TAXIING AGAIN WHEN THEY HEARD ABOUT 'BLASTING THE CESSNA.' N1 AT IDLE POWER WAS 21%. BOEING SPOKESMAN SAID BREAK-AWAY THRUST FOR AN EMPTY AIRCRAFT WAS 25 PERCENT N1, WHILE A FULLY LOADED AIRCRAFT NEEDED 35%.

THE USE OF EXCESSIVE BREAK-AWAY THRUST BY THE BOEING 737 CREW. A FACTOR RELATED TO THE ACCIDENT WAS: IMPROPER PLANNING/DECISION BY THE CESSNA 172 PILOT BY ACCEPTING A CLEARANCE TO TAXI BEHIND THE BOEING 737 WITHOUT ASSURANCE THAT THE BOEING 737 CREW WOULD NOT POWER UP.