I noticed a GA plane fly pretty low over my house today heading towards PDX. I checked on FlightRadar and noticed it made (what seemed like) an unusual maneuver. It flew directly to the airport and entered what looked like a very abbreviated right hand pattern to runway 10 at only a few hundred ft MSL. I think it was a touch and go, and it took off right afterwards. The sectional doesn’t show a RP for any PDX runway, and it doesn’t really match any IFR approaches either. What might this be and when would it be approved? I didn’t take a screenshot of the flight path so I recreated it.
When you're at a controlled airport, ATC directions can be anything they want for pattern entry.
AIM 4-3-2 does a poor job of saying it with this text:
When necessary, the tower controller will issue clearances or other information for aircraft to generally follow the desired flight path (traffic patterns) when flying in Class B, Class C, and Class D surface areas and the proper taxi routes when operating on the ground. If not otherwise authorized or directed by the tower, pilots of fixed-wing aircraft approaching to land must circle the airport to the left.
But this example would likely be an ATC instruction to make right traffic.
Runway 10R at PDX uses Right Traffic.
Source: Airnav. This information is derived from the applicable "Chart Supplement" for PDX, which contains expanded airport data beyond that which is shown on the sectional chart, and is an important document to review before operating to or from any airport.