B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 210; Flight Crew Type 19000
Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Flight Crew Became Reoriented
Human Factors
Clearance was the GEETK9 RNAV Departure. On takeoff Runway 8R; Tower cleared us for takeoff RNAV HRSHL. After takeoff; while cleaning up the aircraft; we tried to initiate direct HRSHL as directed by Tower in the FMC. We had no flight director showing direct to HRSHL. After several attempts to initiate direct in the FMC; cleaning up the aircraft; IMC; raining; Master Caution for Center Boost Pumps (twice); and Tower querying us; I told Tower we were having navigation issues and ask for a heading to HRSHL. Tower gave us a heading to HRSHL and handed us off to Departure. We found the flight directors switches were off; we contacted Departure and rejoined the departure. I turned the flight directors off during taxi-in to clear the FMA and got distracted. My usual pre-departure 'mental checklist technique'; after the before takeoff checklist is run; includes checking 'flight directors on' among several other items (i.e. minimum takeoff fuel). The one time I did not perform my technique; the flight directors were off.Preventative Measures: Add flight directors to the before takeoff checklist.
[Report narrative contained no additional information.]
B737 flight reported taking off unknowingly with flight director switches off.