Any Unknown or Unlisted Aircraft Manufacturer
Flight Crew Last 90 Days 49; Flight Crew Total 225; Flight Crew Type 225
Other / Unknown; Troubleshooting; Confusion
Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway; Inflight Event / Encounter Weather / Turbulence
General None Reported / Taken
Human Factors
I was completing my run-up at the arrival end of Runway XY of ZZZ when I witnessed a runway incursion event that could have resulted in two accidents involving three aircraft. Across the runway from me; Aircraft Y taxied up and was holding for landing traffic on Runway XY as well. I radioed the Aircraft Y pilot on CTAF to say that I would hold for her to depart first; since it was a skydiving ops plane and I was in no hurry. The landing traffic Aircraft Z touched down (it was a small single engine of some kind) and Aircraft Y taxied onto the runway as soon as Aircraft Z passed us. The Aircraft Y pilot did not wait for Aircraft Z to exit the runway and instead throttled up and began accelerating down Runway XY towards Aircraft Z which was still rolling out; about midfield. If this wasn't bad enough; another pilot [Aircraft A] on short final decided not to go around but instead to land on Runway XY with two aircraft ahead of him. I do not remember what type of aircraft this third plane was; a small single-engine of some kind. The Aircraft Y pilot had to abort her takeoff and slam on the brakes to avoid hitting Aircraft Z; which rolled all the way to the departure end of the field before finally exiting. Aircraft Y exited the runway just in time for Aircraft A to roll out behind it without a collision. What caused the problem: 1. While Aircraft Y might have been OK to 'line up and wait' on Runway XY; she should not have begun her takeoff roll until the runway was clear. Pilot displayed impatience and was counting on Aircraft Z to exit promptly; which it did not. With traffic in the pattern; even the decision to line up and wait was not a very prudent one.2. The third; landing plane should have executed a go-around. The runway was occupied with two aircraft ahead of it. 3. Smoke/haze in the area may have been a factor; although the visibility was at least 3-5 SM and I don't believe that the runway was obscured from view at any time.
Pilot holding short of the runway at a non-towered airport reported observing a a Critical Ground Conflict involving three aircraft in different phases of takeoff and landing.