Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 173
Workload; Human-Machine Interface; Confusion; Time Pressure
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew FLC Overrode Automation; Flight Crew Returned To Clearance; Flight Crew Took Evasive Action; General Maintenance Action
Aircraft; Procedure
On takeoff from Runway 01 at DCA we were assigned the REBLL2 RNAV Departure. Prior to takeoff roll; both flight directors had been turned on with the Captain's (PF) set as master and LNAV was armed. On takeoff roll; the TOGA button was depressed and the autothrottles set the commanded takeoff thrust. Sometime between then and 400 feet AGL the flight directors disappeared from view and LNAV failed to engage. This was noticed at 400 feet AGL with the normal procedure to 'Verify LNAV.' I (PM) reselected TOGA to regain the flight directors then selected LNAV. Meanwhile; observing outside the cockpit that we were in danger of proceeding north of the Potomac River; I directed a left turn which the Captain (PF) was already beginning to initiate. We intercepted the normal departure course and flew the departure as published. By our estimation we had not entered the restricted airspace. I was also monitoring Guard frequency and we received no radio communication on that frequency.
Contract Maintenance in ZZZ could not duplicate the problem. Company MX Control said they have a history of this problem occurring on this aircraft but it always passes the BITE check. The same problem occurred with our takeoff from ZZZ. The aircraft was MEL'ed in ZZZ for LNAV and flight directors. Fixing the problem will avoid this from occurring again. Losing this system in IMC on an LNAV departure leaves the crew with limited choices.
A B737NG departed DCA on the REBLL2 RNAV. Shortly after takeoff both flight directors failed and LNAV ceased guidance so the crew manually initiated a turn to the departure course and avoided P56.