Narrative:

As pilot of turbo commander; I was making a visual landing on runway 23. Radar vectors were provided until ZZZ was in sight. We were then turned over to the tower; and entered a right downwind leg for runway 23. Weather conditions were VMC; with a light crosswind. There were no other aircraft in the traffic pattern. Flight in the traffic pattern was nominal. Airspeed and power settings on final were nominal. About 20 feet above the runway we experienced a balloon effect which may have been the result of reflected heat radiating from the runway. Touchdown was on the centerline and nominal. Once the nose gear was on the ground I applied reverse and continued on the centerline for about 10 seconds. The plane then veered slightly to the right. I successfully corrected the direction. A few seconds later the aircraft again veered to the right. I was unable to control the drift to the right with rudder; brakes; or differential power. Eventually the aircraft left the right side of runway 23 and entered the grass area at about the mid-point of the runway length. To the best of my knowledge there was no damage done to any runway equipment.while off the runway I was able to straighten the aircraft and began a left turn back to the runway. The tower asked if we needed assistance and we declined. With tower permission we reentered runway; proceeded to a taxiway; and then to the FBO ramp. During that period of taxiing; control of the aircraft was nominal. In an attempt to determine what had happened; steering was accomplished with rudder; brakes; and differential power; all were nominal. After engine shutdown; the aircraft was inspected by the two pilots. We found no damage to any part of the plane; nor any indicators of what caused the steering difficulty. After refueling; and another inspection of the aircraft; we started engines; taxied to runway 23; and performed a takeoff. The same pilot was at the controls. Power was applied slowly at first to ensure we had appropriate steering capability. The takeoff was nominal. There were no abnormal indications during the IFR flight to home base. The landing at ZZZ1 was completely nominal. After touchdown reverse was applied. There were no steering or control issues. After clearing the runway at ZZZ1; taxiing and directional control were completely nominal.we do not understand what caused the runway departure. There are no indications of any malfunction or damage to the aircraft. To the best of our knowledge there was no damage to any facilities or equipment at ZZZ.

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Original NASA ASRS Text

Title: Turbo Commander 690A pilot reported loss of directional control on landing roll that resulted in a runway excursion. No cause was determined.

Narrative: As pilot of Turbo Commander; I was making a visual landing on runway 23. Radar vectors were provided until ZZZ was in sight. We were then turned over to the tower; and entered a right downwind leg for runway 23. Weather conditions were VMC; with a light crosswind. There were no other aircraft in the traffic pattern. Flight in the traffic pattern was nominal. Airspeed and power settings on final were nominal. About 20 feet above the runway we experienced a balloon effect which may have been the result of reflected heat radiating from the runway. Touchdown was on the centerline and nominal. Once the nose gear was on the ground I applied reverse and continued on the centerline for about 10 seconds. The plane then veered slightly to the right. I successfully corrected the direction. A few seconds later the aircraft again veered to the right. I was unable to control the drift to the right with rudder; brakes; or differential power. Eventually the aircraft left the right side of runway 23 and entered the grass area at about the mid-point of the runway length. To the best of my knowledge there was no damage done to any runway equipment.While off the runway I was able to straighten the aircraft and began a left turn back to the runway. The tower asked if we needed assistance and we declined. With tower permission we reentered runway; proceeded to a taxiway; and then to the FBO ramp. During that period of taxiing; control of the aircraft was nominal. In an attempt to determine what had happened; steering was accomplished with rudder; brakes; and differential power; all were nominal. After engine shutdown; the aircraft was inspected by the two pilots. We found no damage to any part of the plane; nor any indicators of what caused the steering difficulty. After refueling; and another inspection of the aircraft; we started engines; taxied to runway 23; and performed a takeoff. The same pilot was at the controls. Power was applied slowly at first to ensure we had appropriate steering capability. The takeoff was nominal. There were no abnormal indications during the IFR flight to home base. The landing at ZZZ1 was completely nominal. After touchdown reverse was applied. There were no steering or control issues. After clearing the runway at ZZZ1; taxiing and directional control were completely nominal.We do not understand what caused the runway departure. There are no indications of any malfunction or damage to the aircraft. To the best of our knowledge there was no damage to any facilities or equipment at ZZZ.

Data retrieved from NASA's ASRS site 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.