Date: 201603
Local time of day: 1201-1800
Flight conditions: VMC
Weather elements / visibility: 5
Light: Daylight
Aircraft: PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Operator: FBO
Operating under: Part 91
Flight plan: VFR
Mission: Training
Flight phase: Landing
Reporter organization: FBO
Reporter function: Pilot Not Flying; Instructor
Reporter qualification: Flight Crew Instrument; Flight Crew Commercial; Flight Crew Flight Instructor
Human factors: Training / Qualification; Situational Awareness
Anomaly: Ground Excursion Runway; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Regained Aircraft Control
Contributing factors: Human Factors; Weather
Primary problem: Human Factors

Narrative: I was doing landing practice in the pattern with a student when we veered off the runway during landing. This student was already an experienced CFI in another category of aircraft and was training for a (private pilot) airplane add-on. There was a 10 knot crosswind from the left. We had completed several laps around the pattern and he was executing nicely stabilized patterns and approaches. We were working on improving the flare; touchdown; and crosswind technique. The student was consistently landing well left of centerline each time. We discussed this repeatedly; including the reasons for landing on the centerline; ways to improve; and the need to go around when the landing was not stabilized and on centerline.On about the 10th landing; the student was again lined up to touch down somewhat to the left of the centerline. There was a small gust and the student also released the crosswind inputs during a brief flare; while simultaneously giving up the controls to me with a hurried last-minute 'your controls'. We touched down near the runway edge; then the left wheel went off the pavement. There was a couple inches of snow slush along the runway; hitting this caused some additional left yaw. This sent us entirely into the grass. While this was developing; I added power to go around; but since we were already skimming along the ground while wallowing along at a high angle of attack; and the ground was clear in front of us; I quickly opted to cut power and come to a stop with soft field technique in the grass alongside the runway.The aircraft was not damaged in any way; and there was no damage to runway lights; signs; or other airport facilities. I believe that this good fortune was due to luck in the particular positioning of the event; as well as moderate conditions that allowed the snow to be melted and slushy but the adjacent ground to still be relatively frozen and firm. Additionally; the airport engineering itself (i.e. the existence of the runway safety area; object free area; etc.) helped prevent a worse outcome. The soft field rollout with a bit of power and yoke back likely helped a little as well.However; the key lesson learned here is that I should have intervened earlier and initiated a go around much earlier to prevent the problem in the first place. I've emphasized the need to be on centerline with my students all along. After this; I will be greatly reducing my tolerance how far I let things proceed before expecting the student to go around and/or intervening myself.Lastly; it's possible that this student's status as a CFI in another aircraft category clouded my judgment somewhat; as well as my approach to critique; although we discussed the landing issues repeatedly; I was perhaps less emphatic that I might have been with a low-time student. Going forward; I will take extra care to watch for and avoid these types of issues as well.




Synopsis: A flight instructor in a PA28 reported a runway excursion that occurred when the trainee drifted to the runway edge during landing.