Date: 202009
Local time of day: 0601-1200
Location: PDX.Tower, OR
Flight conditions: IMC
Weather elements / visibility: Fog; Haze / Smoke
Aircraft: EMB ERJ 170/175 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
Airspace: Class C PDX
ATC / advisory: Tower PDX
Aircraft component: GPWS
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion
Second reporter function: Captain
Anomaly: Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Other / Unknown
Detector: Automation Aircraft Terrain Warning; Person Flight Crew
When detected: In-flight
Result: Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem
Contributing factors: Aircraft; Weather
Primary problem: Aircraft

Narrative: On takeoff from PDX; in IMC conditions from takeoff up to about 15;000 ft. MSL. Everything seemed normal until 400 ft. AGL. The captain called 'verify NAV' and I did and then I noticed the EICAS displayed in cyan advisory messages 'Autoland 1 not available' and a second message which I believe was 'RNP (Required Navigation Performance) 0.1 not available.' I am certain about the first message but not about the second. I also noticed that the yellow square with 'RA' was displayed on the PFD in the bottom right corner. This seemed indicative of a radio altimeter malfunction or miscompare. The EICAS messages extinguished quickly and immediately we received an aural warning 'too low; terrain' GPWS message. I did not see a message on the PFD and there was no guidance provided; only the aural warning. I believe the aural warning was only announced once and then went away.This Aural warning is usually only for being low to terrain and not in a correct Landing configuration. We were taking off in takeoff configuration. The gear was up right after takeoff and the flaps were set to 2 for takeoff and had not been retracted since we had not achieved acceleration height. So the aural warning did not make any sense.We both quickly began scanning the instruments and found that the aircraft was already pitched to take off pitch of around 18 degrees nose up. Wings were mostly level. The aircraft was on the flight director. The altitude and vertical speed indicated a climb. Both PFDS displayed the same information. The backup instrument panel displayed the same. The MFD was on terrain display on the map page and showed black terrain in the immediate area and distant green terrain around the aircraft. And thrust was in the TOGA (Takeoff Go Around) position.So everything cross referenced to show a normal; terrain free; take off and climb. Also; we were already in full take off climb thrust; pitch; and configuration. So we continued flight.We got to acceleration height and retracted flaps and continued the remainder of the flight without issue. The issue did not repeat itself again.Another thought is that the IMC conditions were caused by smoke from wild fires. Perhaps the smoke particulates caused a radio altimeter malfunction and the RA briefly read the altitude as too low for only a split second.We were already in GPWS response pitch and configuration. So there was not much else to do. Especially when all indications seemed normal for climb out and the GPWS message was brief and seemed associated with RA malfunction. The only possible extra effort that could be made would be thrust to MAX but that didn't seem necessary in this case as the aural warning had already stopped.


Second narrative: The flight departed PDX into immediate IMC because of fog and smoke in the area. Everything was functioning normal and it was standard takeoff and climb. At about 500-600 ft. MSL the FO's (First Officer) PFD indicated an issue with the radar altimeter: amber rectangle with RA. Two EICAS messages appeared. One of them was AUTOLAND 1 NOT AVAIL and I think the second message was something with the RNP (Required Navigation Performance). At which point the EGPWS warning 'TOO LOW; TERRAIN' was heard once. I immediately verified again that the aircraft is pitching up; climbing at takeoff power; on speed; and following the RNAV departure; according to standard profile. Terrain map did not indicate any colors but green and black on the MFD. After a few seconds all messages extinguished and the flight proceeded without any other malfunctions or anomalies.Upon discussing the event with my FO later in cruise; we both thought that it was a radar altimeter anomaly and that the aircraft was at all times operated following normal operating procedures and never outside the normal flight profile/envelope. We also discussed the possibility of an oversized vehicle on the I-205 bridge as that would have been about the point in the air this event occurred.Please monitor if this was a onetime occurrence or there is a trend.


Synopsis: EMB175 flight crew reported GPWS message during climbout.