Narrative:

There was more traffic than I had ever experienced during a week night [late evening] at spokane international airport (geg). A contributing factor seemed to be the number of kc-135 tankers (that normally fly out of fairchild air force base but are currently based at spokane international while work is taking place at fairchild) returning from their missions. After being sequenced in to runway 21; I landed at the stripes; was slowing to about 50 ktas; had all three wheels on the ground when my right wing started to lift and I found myself being 'pushed' to the left. Within seconds; I was on the grass infield approximately 50 ft left of runway 21. Knowing that there was a lot of traffic behind me; I made the decision to continue on the grass to intersection foxtrot (which was about 100 ft ahead of me). I don't know that tower was aware I was off the runway and I was too busy trying to get the plane to foxtrot to make any calls. Tower asked if I could hurry to foxtrot and I was able to respond that I was almost there. Upon reaching foxtrot; I transitioned from the grass to the taxiway pavement and quickly across the hold short line. [I] then contacted ground indicating that I was clear of runway 21 at foxtrot and ready to taxi back to the ramp (which was straight ahead). In mental replays of what happened; I can only figure that I must have experienced some residual wake turbulence given that it was a cold; crisp evening with little to no wind to dissipate any vortices. When I talked with two of the pilots that work out of the local FBO; they both indicated that with the kc-135 tankers flying into spokane international; they had been making a practice of landing a little longer than the stripes in order to avoid what I may have experienced. In this case; I'm not sure the tower could have done anything different (they had been warning of possible wake turbulence following the landing of each heavy) but I learned a valuable lesson as to what to do differently under such conditions. Fortunately; there was no damage to the plane nor did I hit any runway or taxiway lights; but I was shaken by the incident and half expected to get a query from the tower as to what had happened and why I was off the runway for a short period of time. I'm not sure tower knew that this all happened given how dark it was and how busy things were that evening.

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Original NASA ASRS Text

Title: A C182 pilot reported difficulty controlling his aircraft after touching down behind a KC-135 at GEG; indicating a possible wake vortex encounter.

Narrative: There was more traffic than I had ever experienced during a week night [late evening] at Spokane International Airport (GEG). A contributing factor seemed to be the number of KC-135 tankers (that normally fly out of Fairchild Air Force Base but are currently based at Spokane International while work is taking place at Fairchild) returning from their missions. After being sequenced in to Runway 21; I landed at the stripes; was slowing to about 50 KTAS; had all three wheels on the ground when my right wing started to lift and I found myself being 'pushed' to the left. Within seconds; I was on the grass infield approximately 50 FT left of Runway 21. Knowing that there was a lot of traffic behind me; I made the decision to continue on the grass to intersection Foxtrot (which was about 100 FT ahead of me). I don't know that Tower was aware I was off the runway and I was too busy trying to get the plane to Foxtrot to make any calls. Tower asked if I could hurry to Foxtrot and I was able to respond that I was almost there. Upon reaching Foxtrot; I transitioned from the grass to the taxiway pavement and quickly across the hold short line. [I] then contacted Ground indicating that I was clear of Runway 21 at Foxtrot and ready to taxi back to the ramp (which was straight ahead). In mental replays of what happened; I can only figure that I must have experienced some residual wake turbulence given that it was a cold; crisp evening with little to no wind to dissipate any vortices. When I talked with two of the pilots that work out of the local FBO; they both indicated that with the KC-135 tankers flying into Spokane International; they had been making a practice of landing a little longer than the stripes in order to avoid what I may have experienced. In this case; I'm not sure the Tower could have done anything different (they had been warning of possible wake turbulence following the landing of each heavy) but I learned a valuable lesson as to what to do differently under such conditions. Fortunately; there was no damage to the plane nor did I hit any runway or taxiway lights; but I was shaken by the incident and half expected to get a query from the Tower as to what had happened and why I was off the runway for a short period of time. I'm not sure Tower knew that this all happened given how dark it was and how busy things were that evening.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.