PWRBACK -- TOO FAR.

Narrative

I WAS EXECUTING A PWR BACK FROM THE GATE IN IAH ON FEB/XX/95 AT APPROX XA19Z. ACFT WAS A DC-9-30 AND IT WEIGHED APPROX 99.3 K. WX CLR. RAMP DRY I PWRED BACK AT APPROX 1.2 EPR. DURING THE PWRBACK I FELT WE WERE GOING BACK FURTHER THAN NORMAL ALSO THAT WE WERE GAINING MOMENTUM. THE FO HAD GONE HEADS DOWN TO CHANGE RADIO FREQ. WE HAD BEEN GIVEN A TURN AND THE ACFT WAS PWRING BACK SOUTHWARD PERPENDICULAR TO TXWY 5X. I FELT APPREHENSIVE ABOUT OUR PROX TO THE EDGE OF THE TXWY. I ADDED FORWARD THRUST TO STOP OUR BACKWARD MOVEMENT. PRIOR TO THE MARSHALLER GIVING THE COME AHEAD SIGNAL. THE ENGS APPEARED TO SPOOL SLOWLY AND I ADDED MORE FORWARD THRUST ACTIVATING THE TKOF WARNING HORN AS WE CONTINUED TO MOVE REARWARD. WE FELT A SMALL BUMP AS THE ACFT SLOWED TO A STOP AND THEN ANOTHER SMALL BUMP AS THE ACFT MOVED FORWARD. I TAXIED AHEAD SEVERAL MORE FT; PARKED THE ACFT AND SET THE PARKING BRAKE. OPS WAS CALLED AND A MAINT SUPVR AND SAFETY SUPVR RESPONDED TO THE ACFT. THE MAINT SUPVR INSPECTED THE ACFT AND SAID WE HAD LEFT THE TXWY ABOUT 1 1/2 FT; BUT THAT IT WAS STRAIGHT IN AND STRAIGHT OUT AND THAT NO SIDE LOADS WERE INCURRED.' HE TOLD US THE ACFT WAS 'OK FOR FLT.' (NOTIFIED US VIA HEADSET). DURING THE INCIDENT; THE MARSHALLER DID NOT APPEAR TO REALIZE HOW CLOSE WE WERE TO THE EDGE OF THE TXWY OR THAT THE MAIN GEAR HAD GONE BEYOND THE THRESHOLD OF THE TXWY.