Date: 202011
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Skyhawk 172/Cutlass 172
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Takeoff / Launch
Reporter organization: Personal
Reporter function: Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Commercial
Second reporter function: Other / Unknown
Anomaly: Ground Event / Encounter Loss Of Aircraft Control; Ground Excursion Runway
Detector: Person Flight Crew
When detected: Taxi
Result: Flight Crew Regained Aircraft Control
Contributing factors: Aircraft; Human Factors
Primary problem: Ambiguous

Narrative: I was renting a C172 for some fun flying and to prepare for an interview in flight check ride. I took a family member along with me; who is an experienced ATP pilot as a safety [pilot] and a pair of extra eyes. After a thorough preflight with no abnormal conditions; I started the aircraft and began taxiing to the run up area. At one point on the taxiway (talking to ground) but blocked by hangars so out of sight; the aircraft veered aggressively to the right; but I was able to successfully reduce power and tap both brakes; recover control and had no further issues on taxi or in the run up area.Upon being cleared for takeoff with all appropriate checklists completed and the parking brake verified off; we began our taxi to the runway and alignment with centerline. It was during the left turn to align with runway centerline before adding power; that I was applying full left rudder and the aircraft was still turning right (crossing through centerline and heading diagonally with the nose pointing off at the tower). I began using left brake to no avail; brought the power to idle and had full pressure on both brake pedals. I drifted off into the grass area on the right side of Runway XX by 1-2 feet. I believe the nose and 1 main wheel were in the grass with 1 main still on the runway. At this point; I notified Tower and completed shutdown check list. The run-off into the grass area occurred no faster than 1-2 MPH. When I applied full brake to try and avoid going into the grass; [the safety pilot] also hopped on the brakes to try and get us stopped in the last 1-2 feet or so before going off pavement. I specifically did not notice anything abnormal or out of place on the preflight. Something to note: the parking brake was applied previous but not immediately before those 2 occurrences and was verified disengaged. In hindsight; I could have taxied back to the ramp after the first occurrence; but the plane did make 3 tight turns on the way to the runway that caused no issue; so it was not a red flag.


Second narrative: A close family member asked me to be a safety pilot as they were preparing for an in flight interview and wanted a second set of eyes. After a thorough preflight with no abnormal conditions; we got in the plane and started the aircraft. At one point on the taxiway (talking to Ground) but blocked by hangars so out of sight; I observed the aircraft veer aggressively to the right. The PIC (Pilot-In-Command) stomped on the brakes and brought the power to idle as we came to a full stop and recovered control. There seemed to be no further issues on taxi or in the run up area.Upon being cleared for takeoff with all appropriate checklists completed and the parking brake verified off (something I personally checked); the PIC began our taxi to the runway and alignment with centerline. It was during the left turn to align with runway centerline before adding power; the plane began to aggressively pull to the right again. The aircraft was passing through centerline to the opposite side of the runway and the PIC had full left rudder and at some point also left brake to try maintain directional control. PIC brought the power to idle and had full pressure on both brake pedals.As it became clear the aircraft was not going to stop on the runway and continued turning right; I placed both my feet on the brakes to try and help it stop about 1-2 feet before going into mowed grass area. PIC notified Tower and completed shutdown check list. The run-off into the grass area occurred no faster than 1-2 MPH. I witnessed the PIC do their best to regain control and follow aircraft procedure. The PIC has a significant amount of hours more in Cessnas than I do; and a pilot I consider to be very competent. I am at a loss to explain why the aircraft lurched to the right other than some sort of mechanical malfunction.


Synopsis: C172 pilot and observer reported a runway excursion followed loss of directional control during runway alignment.