B737 Next Generation Undifferentiated
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 120; Flight Crew Total 14000; Flight Crew Type 1149
Workload; Distraction; Confusion; Situational Awareness
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT
Flight Crew Took Evasive Action; Flight Crew Executed Go Around / Missed Approach
Procedure; Airport; Weather; Airspace Structure; Environment - Non Weather Related
During a recent missed approach to MROC; I became aware that using the LNAV mode during the missed approach takes the aircraft way; way past the TIO 113 radial. The missed approach procedure also calls for the airplane to be leveled at 7000 feet which is approximately 1000 feet below the ridge line of the mountain that staying North of the TIO 113 radial is designed to avoid. Thus; if you precisely fly the missed approach in LNAV; you are pretty well positioned to hit the mountain at 7000.  If you haven't set up the TIO 113 radial on the FIX page; there's a good chance you won't notice the problem until you get the GPWS warning. I should also add that in the 737; the LNAV mode is the default lateral mode at 400' during a busy time in the cockpit. So; I think a person can reasonably understand the chain of events leading to CFIT during an MROC ILS 7 missed approach. During our missed approach;  we had the TIO 113 radial displayed on the EFIS screens (due to the engine out procedure; takeoff procedure; and a small note on the approach chart to remain North of the TIO 113) so we recognized the issue significantly before the LNAV went too far down that road. A note to not use LNAV on the missed approach would have given us a heads up for what was to come. Our solution to the issue was to turn off the autopilot; resume hand flying the aircraft; and increase the angle of bank thus tightening the turn and going off the LNAV magenta line to be well within the 113 radial. Of course; this was unexpected and increased workload considerably although the right resolution to the situation.
The reporter stated that although he had been into MROC at least 25 times; this missed approach was his first. This is not Special Qualifications Required airport; but possibly should be because of the close mountainous terrain proximity. His Company's takeoff briefing sheet procedures and cautions cover takeoffs very well. No such information exists for go-arounds and missed approaches. Because missed approach initiation engages LNAV automatically and flies at about 200 kts; the aircraft will probably not remain inside the 113 radial. Crews should be prepared to slow or turn more steeply than the preprogrammed 15 degrees. As stated earlier; the workload increase must be considered during the missed approach brief.
B737 flight crew realized during the MROC ILS DME Runway 07 missed approach a tight turn was required to comply with the constraint to remain north of TIO 113 radial and avoid the terrain exceeding 7;000 ft so LNAV was disconnected and the go-around flown manually.