B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 155
Situational Awareness
Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented
Human Factors; Procedure
Climbing thru 400 feet I selected LNAV; but it did not engage. The Captain continued to fly the aircraft and at approximately 1600 feet I requested vectors to insure we did not violate ourselves; and continued to troubleshoot the problem. At 3000 feet the Captain called for VNAV but after selection it did not engage. As we continue trying to figure out why neither LNAV; nor VNAV would engage; we climbed thru the assigned altitude of 4000 feet.The altitude deviation was noticed and we stop the ascent at 4500 feet. Before we could begin to descend to 4000 feet; ATC gave us a climb to higher altitude. Once the climb was begun I realized neither FD switch had been selected to ON. Upon selecting ON both LNAV and VNAV engaged and the flight continued without further trouble. ATC never queried us as to any altitude deviation.The habit of turning both FD switches to OFF after landing should be stopped. During the Departure Briefing; acknowledging the FD switches match who is flying the leg should be emphasized.
B737 First Officer reported having difficulty engaging LNAV and VNAV after takeoff; and then noticed both FD switches were off; inhibiting those functions.