B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 169
Distraction
Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Wake Vortex Encounter
General None Reported / Taken
Environment - Non Weather Related; Human Factors
We were on the SWFFT 1 arrival into BNA and had finished briefing the intersections and altitudes. The restriction at LENSE Intersection is to cross at or above FL240. ATC gave us a clearance to descend now to FL300 and then cross LENSE at FL240. The First Officer set 240 in the MCP and started our descent to FL300. At that time; we encountered some wake turbulence; which rolled the aircraft into a 20 to 25 degree right bank and the autopilot disengaged. The First Officer quickly resumed control and had to apply almost full left aileron to stop the roll; yet the aircraft remained in the bank for two to three seconds before the wings rolled level. He returned the aircraft to a stabilized profile and then re-engaged the autopilot with the aircraft back LNAV and VNAV PATH.I did not notice that we had forgotten to change the 'at or above altitude' at LENSE to a hard altitude of 240. It was in our descent through FL290 and about eight miles from LENSE Intersection that I noticed we were not going to make our altitude and reported it to ATC as we crossed the intersection at approximately FL260. They then gave us a clearance to descend to FL240. The flight continued to BNA without any further problems.
B737-700 Captain reported a wake vortex encounter on descent into BNA that provided enough distraction they missed a crossing restriction.