Date: 201502
Local time of day: 0601-1200
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Stearman
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Landing
Reporter organization: Personal
Reporter function: Instructor; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Commercial; Flight Crew Flight Instructor
Anomaly: Aircraft Equipment Problem Less Severe; Ground Event / Encounter Loss Of Aircraft Control; Ground Event / Encounter Ground Strike - Aircraft; Ground Excursion Runway; Inflight Event / Encounter Loss Of Aircraft Control
Detector: Person Flight Crew
When detected: Other landing roll
Result: General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: This was the second flight of the day. Flying a friend in the Stearman. This was the 6th landing of the 2nd flight; and the 11th landing of the day. On the 5th landing of this flight; noticed a sudden quick pull to the right on the start of the roll-out after touchdown with the tail-wheel in full contact. Did a go around before the aircraft could depart control. I decided to do a wheel landing to be safe and carry power on the next landing for better control. Touched down lightly on the mains just right of center line. Rolled the power back and stick full aft to bring the tail-wheel into contact with the ground and began a long roll-out. At just below 40 mph; stick full aft and power off; the airplane lurched to the right briefly; I corrected with left rudder; then right as I still had my heels on the ground; the aircraft started a soft turn to the left and would not correct back right with rudder. I pressed brakes on the right to correct and the right wing dipped; I brought power in to straighten the nose and immediately to idle when the wing tip cleared the ground and applied brakes evenly to slow the aircraft as we departed 90 degrees to the runway. At a slow roll the aircraft main wheels slid into a small muddy drainage ditch at the side of the runway and the airplane rolled slowly up to its nose to rest on the lower portion of the engine. During that time I brought the mixture to cut off and turned the mags off as we settled nose first; tail high into the mud. After pulling the aircraft from the ditch with the help of local airport personnel; we were able to clean out the mud; inspect the structure and engine; pull the prop through; start the engine and taxi the aircraft back to the hangar for further inspection. There was no apparent damage to the airport; the airplane or anyone on board the aircraft. This is a very old aircraft; flown regularly; We suspect once of many possible causes for the initial pull to the right and found evidence on the runway where the right wheel had locked on the roll-out. We suspect that the brake drum may be slightly out of round or the well worn tires caused unusual heating of the bearings; causing one to lock after the roll-out; other possible cause we will be researching is the brake cabling in conjunction with the rudder movement; the tail-wheel alignment and cabling tolerances and the brake shoes and master cylinders themselves. We have grounded the airplane until all possibilities can be researched inspected and either fixed or ruled out. As for the runway departure; the initial locking of the brake caused me as the pilot to react quickly on the left rudder to compensate for the sudden right turn; then back hard on the right and due to the relatively slow speed putting the aircraft under the rudder authority speed caused a side loading on the right wheel and dragging of right wingtip; once turned more than about 30 degrees at such a speed there was no longer the possibility to control the aircraft's' direction and I got to go along for the ride until wing came off the pavement. Final thoughts; if the muddy ditch had been another 10 to 20 yards from the runway; I definitely would have been able to stop the aircraft before rolling into it; A full stall landing would not have helped due to the nature of the initial wheel locking at a speed below rudder authority speed; My reaction to the wheel lock may have been appropriate had the wheel stayed locked; but when the right wheel unloaded the weight on it; it began rolling again; causing a partial ground loop and an uncontrollable situation at the low speed with my toes off the brakes.




Synopsis: PT-13 pilot reported loss of directional control after landing; resulting in wingtip contact with the ground; a runway excursion; and the aircraft ending up on its nose in the mud.