Date: 201811
Local time of day: 1801-2400
Location: CHO.Airport, VA
Flight conditions: VMC
Light: Night
Aircraft: Embraer Jet Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class E PCT
ATC / advisory: TRACON PCT
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Situational Awareness
Second reporter function: First Officer; Pilot Flying
Anomaly: Inflight Event / Encounter CFTT / CFIT
Detector: Automation Aircraft Terrain Warning; Person Flight Crew
When detected: In-flight
Result: Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action
Contributing factors: Environment - Non Weather Related; Aircraft
Primary problem: Ambiguous

Narrative: I checked in with Potomac Approach and they descended us to 3000 feet and told us to expect vectors for the ILS 3 at KCHO. Some minutes later they gave us a turn to a heading of 220. Correcting for the wind out of the west; this put us on a right downwind for Runway 3. It surprised us because in the minutes leading up to this we had visual on the terrain below; including cars on the roads and building lights. It was not dark/invisible terrain. However I knew the safest thing would be to climb anyway. The autopilot came off but before the FO (First Officer) flying could really react much the warning stopped. We had only gained about 150 feet since the caution sounded. We didn't immediately know what had happened. In the past I had experienced RA malfunctions in the [ERJ] that had produced false landing gear warnings; bank angle warnings; ground prox warnings etc and I considered if that had happened but the RA seemed to be working okay. It showed us slowly fluctuating in the range of about 1900-2300 AGL at 3000 MSL. Field elevation at KCHO nearby is 640 feet MSL. As we approached the point where we would be abeam the field; ATC asked us to say our flight conditions. I replied that we were in VMC but could not yet see the field. The controller asked us if we wanted a vector to a visual or the ILS. The FO and I agreed we wanted the ILS. I told ATC this and they acknowledged. During this time we were looking off our right or 2 o clock position a lot; trying to make out the field position. Soon after this; the EGPWS gave us a Ground Prox caution box in the PFD attitude indicator area and an Aural 'Terrain terrain pull up!' When I looked over at my IPad approach plate; my Geo-Referenced aircraft symbol showed us and our track having just passed over an obstacle/tower labeled 1795 feet just east of KCHO near the missed approach track line. I then theorized that our RA might have bounced a wave off this probably metal tower and received enough beam back to cause our RA to read about 1200 feet; an instant drop of hundreds of feet. This led the EGPWS to trigger a warning due either to us not being configured for landing; or due to the EGPWS calculating a false rapid rise in terrain; and possibly coupled with the EGPWS database knowing that tower was there very close by. Possibly an ATC change to raise the Minimum vectoring altitude there; and/or a wider downwind closer to GVE VOR to avoid the possibility of this false warning.


Second narrative: I was the pilot flying. We were nearing the destination airport KCHO from the north. ATC gave us a heading to fly which set us up for a wide right downwind for runway 3. We were holding our last assigned altitude of 3000 thousand when the event occurred. Suddenly; several indications including an aural 'pull up' went off. This occurred approximately 7 nm east of the airport; and coincided with the position of a charted obstruction of 1795 ft MSL; which we did not see at the time. It was night time and the surrounding area was sparsely lit.Various messages. I can't recall all of them; but I do distinctly remember the aural 'pull up.' I also remember several seconds after the event occurred; looking at the radio altitude and noticing we were a little more than 2000 feet above the ground and gradually increasing that height.Aircraft was in such a position to the obstruction on the ground; that the aircraft systems alerted the crew to danger; and to pull up.A few seconds after the indications went off; I clicked the autopilot off. I slowly began to pitch the aircraft up and slowly began increasing the thrust levers. All messages had cleared a short period after the event occurred. As it became clear to the Captain and I that we had flown over a random tall obstruction and would be safe returning to 3000 feet; I selected the auto pilot back on. I don't recall how much altitude we had deviated when we began our slow climb; but it couldn't have been more than a couple hundred feet.I will be more vigilant in the future about terrain at night. I will start having my position turned on while using flight deck pro. This will increase my situational awareness in the terminal area in regards to obstructions.


Synopsis: ERJ flight crew reported receiving a terrain warning while on radar vectors for a visual approach to CHO; likely due to a nearby tower.