Narrative:

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.

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Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.