B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Distraction; Human-Machine Interface
Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued Advisory / Alert; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Regained Aircraft Control
Software and Automation; Weather
Near the FAP; we transitioned into VMC and quickly got an Altitude Alert from ATC and a CAUTION TERRAIN from the GPWS System. I disconnected the autopilot added power and returned to Glidepath to continue the approach to landing.I think the most likely cause was undetected windshear. The aircraft was too high above touchdown to give a windshear warning and the altitude loss was both gentle and sudden enough to cause the system to not be able to respond. The expectations of the crew were that conditions were rapidly improving at the airport. The approach was marked by occasional moderate turbulence which had subsided as we approached the FAF. The transition to VMC and the actions which occur approaching and after the FAF caused the monitoring of performance to breakdown. The design of the LNAV/ VNAV approaches drives a distraction at and after the FAF. There is little that can be done to simplify the altimetry procedures but short finals are always a challenge.
B737-800 pilot reported undetected windshear encounter; resulted in an ATC altitude alert and GPWS terrain caution alert.