PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Flight Crew Commercial; Flight Crew Instrument; Flight Crew Flight Instructor
Flight Crew Last 90 Days 15; Flight Crew Total 530; Flight Crew Type 340
Human-Machine Interface; Distraction
Aircraft Equipment Problem Less Severe; Conflict Ground Conflict; Critical; Inflight Event / Encounter Loss Of Aircraft Control
Flight Crew Regained Aircraft Control; Flight Crew Took Evasive Action
Aircraft; Human Factors
After starting the engine and setting the parking brake; I noticed that my seat was too low and attempted to raise the seat. This required trying to lift my weight off the seat and at the same time activating the seat adjustment knob. While I was doing this; I felt a forward motion and looked up to see the aircraft rolling at a quick walk to a slow jog toward another aircraft parked on the ramp. I quickly applied the brakes and noticed the right wing tip narrowly missed another parked aircraft on the ramp. I previously positioned my aircraft to clear this one; but to clear the second aircraft would require turning the plane while taxiing. Since I couldn't be sure of the clearance I had with the second aircraft (having rolled past where I would have started the turn); I elected to shut down and manually reposition the aircraft. Two lessons learned. First; what we are all taught during primary; to not trust the parking brakes in light GA aircraft is true. They are not reliable enough to let your guard down. Second; while I thought I was minimizing my risks by doing necessary head down work while stopped; in reality it had never occurred to me that the aircraft might roll forward on a crowded ramp without my knowing. Next time; I will do as much work as I can prior to engine start; and leave any remaining tasks to the run-up area. The risk is forgetting to do these tasks later; but a sticky note or equivalent would solve that issue.
PA28 pilot reports starting his engine and setting the parking brake to discover the seat height needs adjustment. While head down making the adjustment aircraft movement is detected and the brakes are quickly applied. The aircraft narrowly misses two aircraft parked on the ramp during the undetected movement.