Narrative:

Flight to jqf was normal until about 1.5 miles outside of ecega on GPS runway 2 approach. Aircraft was on autopilot; LNAV and altitude hold at 2500 ft. The aircraft was configured except flaps were still 15; pilot flying was just about to call for flaps 35 when the warning; 'obstacle; obstacle' sounded. Pilot flying disconnected the autopilot and began climbing without changing aircraft configuration (flaps still at 15). The captain (pilot monitoring) asked the tower to confirm the altimeter setting (it was correct). The warning stopped after climbing to 2700; or 2800 ft MSL and the pilot flying continued the approach. When the captain advised the tower that we were climbing in response to an obstacle warning; we were told; 'oh; yeah; there are some towers out there by the FAF.' we are not sure if this is a common occurrence; or not. The degree of confusion caused to the flight crew by this unexpected event was significant. The pilot flying had to call for the landing checklist multiple times; the pilot monitoring was extremely busy trying to figure out what caused us to get the warning and trying to ensure that we were; in fact; where we were supposed to be on the approach. We have no idea why we got the 'obstacle; obstacle' warning since the aircraft was on the centerline and at the specified altitude. Is it possible that the towers referred to by the tower have been erected since the approach was approved? The next morning; the flight crew observed a series of tall towers in the area of the approach corridor for runway 2. After the pilot flying climbed to 2700-2800 ft; he inadvertently descended below 2500 ft prior to the actual crossing of ecega in response to the VNAV indications which were commanding a descent below 2500 ft. The VNAV indication returned to normal after ecega was crossed. This altitude deviation was a direct result of the confusion caused by this warning and the VNAV indications. There was never a 'terrain warning'; or any indication of further deviation; but it was a significant deviation from the approach mandated altitudes. The aircraft broke out below the overcast shortly after passing ecega and proceeded for a normal landing. Two questions: 1. Why did the 'obstacle' warning occur. 2. What was the appropriate response to the warning? While we practice maneuvers in response to terrain warnings; the pilot flying was confused as to the required response to the obstacle warning. Is the obstacle warning merely advisory; or does it require an immediate full performance climb like a terrain warning? Due to the 'surprise factor;' the havoc wreaked on the crew coordination by this warning was probably as significant as the warning itself. The approach needs to be reviewed to explain why the warning was issued. Perhaps the 2500 ft inbound altitude needs to be raised. If this warning occurs frequently; there needs to be a crew-note; or NOTAM issued to warn the crews of the phenomenon. This event occurred after the crew had been on duty about 12 hours dealing with weather associated with the snow storm moving up the east coast. I'm not sure if crew fatigue was a causal factor; but it certainly didn't help.

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Original NASA ASRS Text

Title: A C560 First Officer reported an EGPWS 'obstacle' alert just outside the JQF Runway 02 FAF ECEGA at 2;500 FT.

Narrative: Flight to JQF was normal until about 1.5 miles outside of ECEGA on GPS RWY 2 approach. Aircraft was on autopilot; LNAV and altitude hold at 2500 FT. The aircraft was configured except flaps were still 15; pilot flying was just about to call for Flaps 35 when the warning; 'OBSTACLE; OBSTACLE' sounded. Pilot flying disconnected the autopilot and began climbing without changing aircraft configuration (flaps still at 15). The Captain (pilot monitoring) asked the tower to confirm the altimeter setting (it was correct). The warning stopped after climbing to 2700; or 2800 FT MSL and the pilot flying continued the approach. When the Captain advised the tower that we were climbing in response to an obstacle warning; we were told; 'Oh; yeah; there are some towers out there by the FAF.' We are not sure if this is a common occurrence; or not. The degree of confusion caused to the flight crew by this unexpected event was significant. The pilot flying had to call for the landing checklist multiple times; the pilot monitoring was extremely busy trying to figure out what caused us to get the warning and trying to ensure that we were; in fact; where we were supposed to be on the approach. We have no idea why we got the 'OBSTACLE; OBSTACLE' warning since the aircraft was on the centerline and at the specified altitude. Is it possible that the towers referred to by the Tower have been erected since the approach was approved? The next morning; the flight crew observed a series of tall towers in the area of the approach corridor for Runway 2. After the pilot flying climbed to 2700-2800 FT; he inadvertently descended below 2500 FT prior to the actual crossing of ECEGA in response to the VNAV indications which were commanding a descent below 2500 FT. The VNAV indication returned to normal after ECEGA was crossed. This altitude deviation was a direct result of the confusion caused by this warning and the VNAV indications. There was never a 'Terrain Warning'; or any indication of further deviation; but it was a significant deviation from the approach mandated altitudes. The aircraft broke out below the overcast shortly after passing ECEGA and proceeded for a normal landing. Two questions: 1. Why did the 'OBSTACLE' warning occur. 2. What was the appropriate response to the warning? While we practice maneuvers in response to terrain warnings; the pilot flying was confused as to the required response to the obstacle warning. Is the obstacle warning merely advisory; or does it require an immediate full performance climb like a terrain warning? Due to the 'surprise factor;' the havoc wreaked on the crew coordination by this warning was probably as significant as the warning itself. The approach needs to be reviewed to explain why the warning was issued. Perhaps the 2500 FT inbound altitude needs to be raised. If this warning occurs frequently; there needs to be a crew-note; or NOTAM issued to warn the crews of the phenomenon. This event occurred after the crew had been on duty about 12 hours dealing with weather associated with the snow storm moving up the east coast. I'm not sure if crew fatigue was a causal factor; but it certainly didn't help.

Data retrieved from NASA's ASRS site as of April 2012 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.