Narrative:

On second maintenance flight after engine repair and replacement; aircraft's runway alignment was adversely affected by light gusting crosswind from left on rollout at approximately 70 mph with tail on ground and landing assured. I tapped l-hand brake to recover desirable runway alignment. L-hand brake momentarily locked up which slid l-hand main tire and made more correction to left than intended. I then tapped r-hand brake to recover desirable runway alignment with the same result. R-hand brake momentarily locked up and aircraft veered back to r-hand more than desired or anticipated. At that point I made a conscious decision to not use brakes further and to let aircraft veer off runway at 20 degree angle to runway centerline to avoid the possibility of ground looping or nosing over on drop. During this final rollout phase; off brakes; at approximately 25 mph both r-hand and l-hand flaps and r-hand landing gear spade door hit the runway marking the signs. Minor damage was done to both runway signs; both flaps; and r-hand spade door. No wing or airframe or propeller damage was incurred. My subsequent observations and conclusions: 1) aircraft had been fitted with oversized P-63 brakes and wheels. 2) no compensation in master cylinder volume had been made to maintain normal P-51 braking feel and effect. 3) both main landing gear pneumatic cylinders had been filled at time of previous annual to maximum ht for strut operation. 4) I was unfamiliar with both this brake combination and aircraft attitude resulting from this strut servicing. 5) I got behind aircraft with regard to its rollout characteristic in crosswind due to my 1200 hour time in type and favorable experience with other aircraft of this type.

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Original NASA ASRS Text

Title: P51D PLT HAS A RWY EXCURSION.

Narrative: ON SECOND MAINT FLT AFTER ENG REPAIR AND REPLACEMENT; ACFT'S RWY ALIGNMENT WAS ADVERSELY AFFECTED BY LIGHT GUSTING XWIND FROM L ON ROLLOUT AT APPROX 70 MPH WITH TAIL ON GND AND LNDG ASSURED. I TAPPED L-HAND BRAKE TO RECOVER DESIRABLE RWY ALIGNMENT. L-HAND BRAKE MOMENTARILY LOCKED UP WHICH SLID L-HAND MAIN TIRE AND MADE MORE CORRECTION TO L THAN INTENDED. I THEN TAPPED R-HAND BRAKE TO RECOVER DESIRABLE RWY ALIGNMENT WITH THE SAME RESULT. R-HAND BRAKE MOMENTARILY LOCKED UP AND ACFT VEERED BACK TO R-HAND MORE THAN DESIRED OR ANTICIPATED. AT THAT POINT I MADE A CONSCIOUS DECISION TO NOT USE BRAKES FURTHER AND TO LET ACFT VEER OFF RWY AT 20 DEG ANGLE TO RWY CTRLINE TO AVOID THE POSSIBILITY OF GND LOOPING OR NOSING OVER ON DROP. DURING THIS FINAL ROLLOUT PHASE; OFF BRAKES; AT APPROX 25 MPH BOTH R-HAND AND L-HAND FLAPS AND R-HAND LNDG GEAR SPADE DOOR HIT THE RWY MARKING THE SIGNS. MINOR DAMAGE WAS DONE TO BOTH RWY SIGNS; BOTH FLAPS; AND R-HAND SPADE DOOR. NO WING OR AIRFRAME OR PROP DAMAGE WAS INCURRED. MY SUBSEQUENT OBSERVATIONS AND CONCLUSIONS: 1) ACFT HAD BEEN FITTED WITH OVERSIZED P-63 BRAKES AND WHEELS. 2) NO COMPENSATION IN MASTER CYLINDER VOLUME HAD BEEN MADE TO MAINTAIN NORMAL P-51 BRAKING FEEL AND EFFECT. 3) BOTH MAIN LNDG GEAR PNEUMATIC CYLINDERS HAD BEEN FILLED AT TIME OF PREVIOUS ANNUAL TO MAX HT FOR STRUT OP. 4) I WAS UNFAMILIAR WITH BOTH THIS BRAKE COMBINATION AND ACFT ATTITUDE RESULTING FROM THIS STRUT SVCING. 5) I GOT BEHIND ACFT WITH REGARD TO ITS ROLLOUT CHARACTERISTIC IN XWIND DUE TO MY 1200 HR TIME IN TYPE AND FAVORABLE EXPERIENCE WITH OTHER ACFT OF THIS TYPE.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.